Intelligent processing for thick composites

NASA Astrophysics Data System (ADS)

Shin, Daniel Dong-Ok

2000-10-01

Manufacturing thick composite parts are associated with adverse curing conditions such as large in-plane temperature gradient and exotherms. The condition is further aggravated because the manufacturer's cycle and the existing cure control systems do not adequately counter such affects. In response, the forecast-based thermal control system is developed to have better cure control for thick composites. Accurate cure kinetic model is crucial for correctly identifying the amount of heat generated for composite process simulation. A new technique for identifying cure parameters for Hercules AS4/3502 prepreg is presented by normalizing the DSC data. The cure kinetics is based on an autocatalytic model for the proposed method, which uses dynamic and isothermal DSC data to determine its parameters. Existing models are also used to determine kinetic parameters but rendered inadequate because of the material's temperature dependent final degree of cure. The model predictions determined from the new technique showed good agreement to both isothermal and dynamic DSC data. The final degree of cure was also in good agreement with experimental data. A realistic cure simulation model including bleeder ply analysis and compaction is validated with Hercules AS4/3501-6 based laminates. The nonsymmetrical temperature distribution resulting from the presence of bleeder plies agreed well to the model prediction. Some of the discrepancies in the predicted compaction behavior were attributed to inaccurate viscosity and permeability models. The temperature prediction was quite good for the 3cm laminate. The validated process simulation model along with cure kinetics model for AS4/3502 prepreg were integrated into the thermal control system. The 3cm Hercules AS4/3501-6 and AS4/3502 laminate were fabricated. The resulting cure cycles satisfied all imposed requirements by minimizing exotherms and temperature gradient. Although the duration of the cure cycles increased, such phenomena was inevitable since longer time was required to maintain acceptable temperature gradient. The derived cure cycles were slightly different than what was anticipated by the offline simulation. Nevertheless, the system adapted to unanticipated events to satisfy the cure requirements.

Exploration Of `Click' Chemistry For Microelectronic Applications

NASA Astrophysics Data System (ADS)

Musa, Osama M.; Sridhar, Laxmisha M.

The ‘Click’ chemistry was explored for low temperature snap cure and for possible use as an adhesion promoter in electronic applications. Several azide and alkyne resins were synthesized and their curing potential was evaluated with a special emphasis on exploring Cu(I) catalyst effect. The preliminary curing study in the absence of catalysts showed a strong dependence of cure temperatures on the electronic nature of alkynes. The cure temperatures showed a tendency to increase with decreasing electronegativity of the substituent on alkynes. The capability of Cu(I) catalysts to accelerate the ‘Click’ chemistry was demonstrated for the first time in bulk phase. Using several Cu(I) catalysts, the cure temperatures could be lowered by as much as 40-100°C compared to the control, depending on the nature of catalyst and the catalyst loading. We discovered a novel synergistic effect between Cu(I) and silver filler in lowering the cure temperatures. Using this combination, lower cure temperatures could be obtained than using either alone. Among several resins screened, one resin system has shown promise for 80°C snap-cure in which the aforementioned synergistic effect is operative. Solution phase ‘Click’ chemistry was employed for the synthesis of a hybrid triazole-epoxy resin system. This system was found to cure without added amine curative. The triazole group here serves as a linker as well as an internal adhesion promoter. To address the incompatibility and volatility issues, which arose during evaluation, a controlled oligomerization method has been developed using controlled heating of azides and alkynes in solution phase.

Studies on chemoviscosity modeling for thermosetting resins

NASA Technical Reports Server (NTRS)

Bai, J. M.; Hou, T. H.; Tiwari, S. N.

1987-01-01

A new analytical model for simulating chemoviscosity of thermosetting resins has been formulated. The model is developed by modifying the well-established Williams-Landel-Ferry (WLF) theory in polymer rheology for thermoplastic materials. By introducing a relationship between the glass transition temperature Tg(t) and the degree of cure alpha(t) of the resin system under cure, the WLF theory can be modified to account for the factor of reaction time. Temperature dependent functions of the modified WLF theory constants C sub 1 (t) and C sub 2 (t) were determined from the isothermal cure data. Theoretical predictions of the model for the resin under dynamic heating cure cycles were shown to compare favorably with the experimental data. This work represents progress toward establishing a chemoviscosity model which is capable of not only describing viscosity profiles accurately under various cure cycles, but also correlating viscosity data to the changes of physical properties associated with the structural transformation of the thermosetting resin systems during cure.

Implantable Self-Powered Low-Level Laser Cure System for Mouse Embryonic Osteoblasts' Proliferation and Differentiation.

PubMed

Tang, Wei; Tian, Jingjing; Zheng, Qiang; Yan, Lin; Wang, Jiangxue; Li, Zhou; Wang, Zhong Lin

2015-08-25

Bone remodeling or orthodontic treatment is usually a long-term process. It is highly desirable to speed up the process for effective medical treatment. In this work, a self-powered low-level laser cure system for osteogenesis is developed using the power generated by the triboelectric nanogenerator. It is found that the system significantly accelerated the mouse embryonic osteoblasts' proliferation and differentiation, which is essential for bone and tooth healing. The system is further demonstrated to be driven by a living creature's motions, such as human walking or a mouse's breathing, suggesting its practical use as a portable or implantable clinical cure for bone remodeling or orthodontic treatment.

Financing cures in the United States.

PubMed

Basu, Anirban

2015-02-01

True cures in health care are rare but likely not for long. The high price tag that accompanies a cure along with its rapid uptake create challenges in the financing of cures by public and private payers. In the US, the disaggregated nature of health insurance system adds to this challenge as patients frequently churn across multiple health plans. This creates a 'free-rider' problem, where no one health plan has the incentive to invest in cure since the returns will be scattered over many health plans. Here, a new health currency is proposed as a generalized version of a social impact bond that has the potential to solve this free-rider problem, as it can be traded not only between public and private payers but also within the private sector. An ensuing debate as to whether and how to develop such a currency can serve the US health care system well.

Ultrasonic mixing of epoxy curing agents

NASA Technical Reports Server (NTRS)

Hodges, W. T.; St.clair, T. L.

1983-01-01

A new technique for mixing solid curing agents into liquid epoxy resins using ultrasonic energy was developed. This procedure allows standard curing agents such as 4,4 prime-diaminodiphenyl sulfone (4,4 prime-DDS) and its 3,3 prime-isomer, (3,3 prime-DDS) to be mixed without prior melting of the curing agent. It also allows curing agents such as 4,4 prime-diaminodiphenyl sulfone (4,4 prime-DDS) and its 3,3 prime-isomer, (3,3 prime-DDS) to be mixed without prior melting of the curing agent. It also allows curing agents with very high melt temperatures such as 4,4 prime-diaminobenzophenone (4,4 prime-DABP) (242 C) to be mixed without premature curing. Four aromatic diamines were ultrasonically blended into MY-720 epoxy resin. These were 4,4 prime-DDS; 3,3 prime-DDA; 4,4 prime-DABP and 3,3 prime-DABP. Unfilled moldings were cast and cured for each system and their physical and mechanical properties compared.

Determination of thermophysical characteristics of vulcanizable rubber products by the mathematical modeling method

NASA Astrophysics Data System (ADS)

Tikhomirov, S. G.; Pyatakov, Y. V.; Karmanova, O. V.; Maslov, A. A.

2018-03-01

The studies of the vulcanization kinetics of elastomers were carried out using a Truck tyre tread rubber compound. The formal kinetic scheme of vulcanization of rubbers sulfur-accelerator curing system was used which generalizes the set of reactions occurring in the curing process. A mathematical model is developed for determining the thermal parameters vulcanizable mixture comprising algorithms for solving direct and inverse problems for system of equations of heat conduction and kinetics of the curing process. The performance of the model is confirmed by the results of numerical experiments on model examples.

Process Modelling of Curing Process-Induced Internal Stress and Deformation of Composite Laminate Structure with Elastic and Viscoelastic Models

NASA Astrophysics Data System (ADS)

Li, Dongna; Li, Xudong; Dai, Jianfeng

2018-06-01

In this paper, two kinds of transient models, the viscoelastic model and the linear elastic model, are established to analyze the curing deformation of the thermosetting resin composites, and are calculated by COMSOL Multiphysics software. The two models consider the complicated coupling between physical and chemical changes during curing process of the composites and the time-variant characteristic of material performance parameters. Subsequently, the two proposed models are implemented respectively in a three-dimensional composite laminate structure, and a simple and convenient method of local coordinate system is used to calculate the development of residual stresses, curing shrinkage and curing deformation for the composite laminate. Researches show that the temperature, degree of curing (DOC) and residual stresses during curing process are consistent with the study in literature, so the curing shrinkage and curing deformation obtained on these basis have a certain referential value. Compared the differences between the two numerical results, it indicates that the residual stress and deformation calculated by the viscoelastic model are more close to the reference value than the linear elastic model.

Imide modified epoxy matrix resins

NASA Technical Reports Server (NTRS)

Scola, D. A.; Pater, R. H.

1981-01-01

High char yield epoxy using novel bisimide amines (BIA's) as curing agents with a state of the art epoxy resin was developed. Stoichiometric quantities of the epoxy resin and the BIA's were studied to determine the cure cycle required for preparation of resin specimens. The bisimide cured epoxies were designated IME's (imide modified epoxy). The physical, thermal and mechanical properties of these novel resins were determined. The levels of moisture absorption exhibited by the bisimide amine cured expoxies (IME's) were considerably lower than the state of the art epoxies. The strain-to-failure of the control resin system was improved 25% by replacement of DDS with 6F-DDS. Each BIA containing resin exhibited twice the char yield of the control resin MY 720/DDS. Graphite fiber reinforced control (C) and IME resins were fabricated and characterized. Two of the composite systems showed superior properties compared to the other Celion 6000/IME composite systems and state of the art graphite epoxy systems. The two systems exhibited excellent wet shear and flexural strengths and moduli at 300 and 350 F.

Assessment of the U.S. Department of Defense Efforts to Develop an Effective Medical Logistics System within the Afghan National Security Forces

DTIC Science & Technology

2011-06-14

aggressively to strengthen measures aimed at ensuring a successful ANSF transition. Ongoing actions include: • Working with CURE International and the ANSF...sustainability include the following ongoing actions: • Working with CURE International and the MoD and MoI to complete, promulgate and implement Standards of Care...approximately June-August 2011. In addition, NTM-A/CSTC-A previously awarded an approximately $1.57M contract with the NGO CURE International to

Electron Beam-Cure Polymer Matrix Composites: Processing and Properties

NASA Technical Reports Server (NTRS)

Wrenn, G.; Frame, B.; Jensen, B.; Nettles, A.

2001-01-01

Researchers from NASA and Oak Ridge National Laboratory are evaluating a series of electron beam curable composites for application in reusable launch vehicle airframe and propulsion systems. Objectives are to develop electron beam curable composites that are useful at cryogenic to elevated temperatures (-217 C to 200 C), validate key mechanical properties of these composites, and demonstrate cost-saving fabrication methods at the subcomponent level. Electron beam curing of polymer matrix composites is an enabling capability for production of aerospace structures in a non-autoclave process. Payoffs of this technology will be fabrication of composite structures at room temperature, reduced tooling cost and cure time, and improvements in component durability. This presentation covers the results of material property evaluations for electron beam-cured composites made with either unidirectional tape or woven fabric architectures. Resin systems have been evaluated for performance in ambient, cryogenic, and elevated temperature conditions. Results for electron beam composites and similar composites cured in conventional processes are reviewed for comparison. Fabrication demonstrations were also performed for electron beam-cured composite airframe and propulsion piping subcomponents. These parts have been built to validate manufacturing methods with electron beam composite materials, to evaluate electron beam curing processing parameters, and to demonstrate lightweight, low-cost tooling options.

Effect of curing modes of dual-curing core systems on microtensile bond strength to dentin and formation of an acid-base resistant zone.

PubMed

Li, Na; Takagaki, Tomohiro; Sadr, Alireza; Waidyasekera, Kanchana; Ikeda, Masaomi; Chen, Jihua; Nikaido, Toru; Tagami, Junji

2011-12-01

To evaluate the microtensile bond strength (μTBS) and acid-base resistant zone (ABRZ) of two dualcuring core systems to dentin using four curing modes. Sixty-four caries-free human molars were randomly divided into two groups according to two dual-curing resin core systems: (1) Clearfil DC Core Automix; (2) Estelite Core Quick. For each core system, four different curing modes were applied to the adhesive and core resin: (1) dual-cured and dual-cured (DD); (2) chemically cured and dual-cured (CD); (3) dual-cured and chemically cured (DC); (4) chemically cured and chemically cured (CC). The specimens were sectioned into sticks (n = 20 for each group) for the microtensile bond test. μTBS data were analyzed using two-way ANOVA and the Dunnett T3 test. Failure patterns were examined with scanning electron microscopy (SEM) to determine the proportion of each mode. Dentin sandwiches were produced and subjected to an acid-base challenge. After argon-ion etching, the ultrastructure of ABRZ was observed using SEM. For Clearfil DC Core Automix, the μTBS values in MPa were as follows: DD: 29.1 ± 5.4, CD: 21.6 ± 5.6, DC: 17.9 ± 2.8, CC: 11.5 ± 3.2. For Estelite Core Quick, they were: DD: 48.9 ±5.7, CD: 20.5 ± 4.7, DC: 41.4 ± 8.3, CC: 19.1 ± 6.0. The bond strength was affected by both material and curing mode, and the interaction of the two factors was significant (p < 0.001). Within both systems, there were significant differences among groups, and the DD group showed the highest μTBS (p < 0.05). ABRZ morphology was not affected by curing mode, but it was highly adhesive-material dependent. The curing mode of dual-curing core systems affects bond strength to dentin, but has no significant effect on the formation of ABRZ.

Out-of-Autoclave Cure Composites

NASA Technical Reports Server (NTRS)

Hayes, Brian S.

2015-01-01

As the size of aerospace composite parts exceeds that of even the largest autoclaves, the development of new out-of-autoclave processes and materials is necessary to ensure quality and performance. Many out-of-autoclave prepreg systems can produce high-quality composites initially; however, due to long layup times, the resin advancement commonly causes high void content and variations in fiber volume. Applied Poleramic, Inc. (API), developed an aerospace-grade benzoxazine matrix composite prepreg material that offers more than a year out-time at ambient conditions and provides exceptionally low void content when out-of-autoclave cured. When compared with aerospace epoxy prepreg systems, API's innovation offers significant improvements in terms of out-time at ambient temperature and the corresponding tack retention. The carbon fiber composites developed with the optimized matrix technology have significantly better mechanical performance in terms of hot-wet retention and compression when compared with aerospace epoxy matrices. These composites also offer an excellent overall balance of properties. This matrix system imparts very low cure shrinkage, low coefficient of thermal expansion, and low density when compared with most aerospace epoxy prepreg materials.

New curing system for urea-formaldehyde resins with polyhydrazides. I. Curing with poly(methycrylol hydrazide)

Treesearch

Katsumasa Miyake; Bunichiro Tomita; Chung-Yun Hse; George E. Myers

1989-01-01

A new curing system for urea-formaldehyde (UF) resins was investigated using poly(methacryloyl hydrazide) as the curing reagent. Results were as follows: 1) Gel time and the water-soluble part of cured resins were determined as function of pH and molar ratio [hydrazide group/(free formaldehyde+methylol group)]. It was found that the reaction in this system proceeds for...

Dielectric cure monitoring: Preliminary studies

NASA Technical Reports Server (NTRS)

Goldberg, B. E.; Semmel, M. L.

1984-01-01

Preliminary studies have been conducted on two types of dielectric cure monitoring systems employing both epoxy resins and phenolic composites. An Audrey System was used for 23 cure monitoring runs with very limited success. Nine complete cure monitoring runs have been investigated using a Micromet System. Two additional measurements were performed to investigate the Micromet's sensitivity to water absorption in a post-cure carbon-phenolic material. While further work is needed to determine data significance, the Micromet system appears to show promise as a feedback control device during processing.

Encapsulation Processing and Manufacturing Yield Analysis

NASA Technical Reports Server (NTRS)

Willis, P.

1985-01-01

Evaluation of the ethyl vinyl acetate (EVA) encapsulation system is presented. This work is part of the materials baseline needed to demonstrate a 30 year module lifetime capability. Process and compound variables are both being studied along with various module materials. Results have shown that EVA should be stored rolled up, and enclosed in a plastic bag to retard loss of peroxide curing agents. The TBEC curing agent has superior shelf life and processing than the earlier Lupersol-101 curing agent. Analytical methods were developed to test for peroxide content, and experimental methodologies were formalized.

Matrix Characterization and Development for the Vacuum Assisted Resin Transfer Molding Process

NASA Technical Reports Server (NTRS)

Grimsley, B. W.; Hubert, P.; Hou, T. H.; Cano, R. J.; Loos, A. C.; Pipes, R. B.

2001-01-01

The curing kinetics and viscosity of an epoxy resin system, SI-ZG-5A, have been characterized for application in the vacuum assisted resin transfer molding (VARTM) process. Impregnation of a typical carbon fiber perform provided the test bed for the characterization. Process simulations were carried out using the process model, COMPRO, to examine heat transfer and curing kinetics for a fully impregnated panel, neglecting resin flow. The predicted viscosity profile and final degree of cure were found to be in good agreement with experimental observations.

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.

Nature cure treatment in the context of India's epidemiological transition.

PubMed

Alter, Joseph Stewart; Sharma, Chandrashekar

2016-07-01

Scholars have argued that theoretical insights of critical medical anthropology should be applied to the analysis of complementary and alternative medicine in order to develop more critically engaged integrative medicine. In this essay we focus on nature cure in the context of India's contemporary epidemiological transition as an example of why engaged integrative medicine is important for public health, and how the institutionalization of nature cure treatment in India provides a critical framework for the development of programs focused on holistic treatment and prevention. After providing an overview of the epidemiological transition in contemporary India, we develop this argument through an examination of illustrative cases in a clinic that operates within the structure of India's Central Council for Research on Yoga and Naturopathy. Based on a review of recent history and contemporary practice we describe how a system of medicine that makes use exclusively of air, earth, sunlight, water and food has been institutionalized and professionalized in India. Whereas biomedical treatment for chronic non-communicable diseases is focused on the problem of curing individual diseases, nature cure establishes a regimen of personalized public healthcare for the integrated management of symptoms. We argue that nature cure is based on an ecological understanding of health, thus providing treatment that reflects a broad appreciation for the risk factors that characterize India's current crises of public health.

Development of new and improved polymer matrix resin systems, phase 1

NASA Technical Reports Server (NTRS)

Hsu, M. S.

1983-01-01

Vinystilbazole (vinylstryrylpyridine) and vinylpolystyrulpyridine were prepared for the purpose of modifying bismaleimide composite resins. Cure studies of resins systems were investigated by differential scanning calorimetry. The vinylstyrylpyridine-modified bismaleimide composite resins were found to have lower cure and gel temperatures, and shorter cure times than the corresponding unmodified composite resins. The resin systems were reinforced with commercially avialable satin-weave carbon cloth. Prepregs were fabricated by solvent or hot melt techniques. Thermal stability, flammability, moisture absorption, and mechanical properties of the composites (such as flexural strength, modulus, tensile and short beam shear strength) were determined. Composite laminates showed substantial improvements in both processability and mechanical properties compared to he bismaleimide control systems. The vinylstyrylpyridine modified bismaleimide resins can be used as advanced matrix resins for graphite secondary structures where ease of processing, fireworthiness, and high temperature stability are required for aerospace applications.

Microkinetic modeling of the autoxidative curing of an alkyd and oil-based paint model system

NASA Astrophysics Data System (ADS)

Oakley, Lindsay H.; Casadio, Francesca; Shull, Kenneth R.; Broadbelt, Linda J.

2015-11-01

Elucidating the curing and aging mechanisms of alkyd and other oil-based paints is valuable for the fields of conservation and bio-based coatings. Recent research has demonstrated the limitations of artificial aging in predicting the actual properties of paints that are hundreds of years old. Kinetic modeling offers pathways to develop a realistic and dynamic description of the composition of these oil-based paint coatings and facilitates the exploration of the effects of various environmental conditions on their long-term chemical stability. This work presents the construction of a kinetic Monte Carlo framework from elementary steps for the cobalt-catalyzed autoxidative curing of an ethyl linoleate model system up to the formation of single cross-links. Kinetic correlations for reaction families of similar chemistry are employed to reduce the number of parameters required to calculate rate constants in Arrhenius form. The model, developed from mechanisms proposed in the literature, shows good agreement with experiment for the formation of primary products in the early stages of curing. The model has also revealed that the mechanisms proposed in the literature for the formation of secondary products, such as volatile aldehydes, are still not well established, and alternative routes are under evaluation.

Advanced composite aileron for L-1011 transport aircraft: Aileron manufacture

NASA Technical Reports Server (NTRS)

Dunning, E. G.; Cobbs, W. L.; Legg, R. L.

1981-01-01

The fabrication activities of the Advanced Composite Aileron (ACA) program are discussed. These activities included detail fabrication, manufacturing development, assembly, repair and quality assurance. Five ship sets of ailerons were manufactured. The detail fabrication effort of ribs, spar and covers was accomplished on male tools to a common cure cycle. Graphite epoxy tape and fabric and syntactic epoxy materials were utilized in the fabrication. The ribs and spar were net cured and required no post cure trim. Material inconsistencies resulted in manufacturing development of the front spar during the production effort. The assembly effort was accomplished in subassembly and assembly fixtures. The manual drilling system utilized a dagger type drill in a hydraulic feed control hand drill. Coupon testing for each detail was done.

Network Formation in Piperidine-Cured Epoxy and Epoxy-Rubber Systems: Effects of Cure Time.

NASA Astrophysics Data System (ADS)

D'Oyen, Raquel M.; Carr, Stephen H.

1996-03-01

The system, piperidine-cured diglycidyl ether of bisphenol-A (DGEBA) to which various amounts of carboxyl terminated acrylonitrile-butadiene (CTBN) have been added, is used as a model rubber modified thermoset. The glass transition temperatures (T_g) of a low molecular weight (374 g/eq) epoxy, cured with piperidine at 120 degC, have been measured by differential scanning calorimetry in order to follow the curing process. The maximum Tg is found after curing for 16 hours. Systems that have been modified with varied concentrations of an adducted CTBN, also show Tg maxima at this time. Addition of 5-20in long-time T_gs, indicating complete segregation of the rubber. The T_gs of the CTBN modified systems at short times are higher than in the unmodified epoxy. This acceleration of the initial stage of cure indicates that the CTBN acts as a diluent, increasing the initial rate of reaction by changing the mobility of the reactive sites. The mechanical properties--toughness, yield and modulus--are related to the CTBN content and to the degree of cure of the system.

A novel injectable borate bioactive glass cement for local delivery of vancomycin to cure osteomyelitis and regenerate bone.

PubMed

Cui, Xu; Zhao, Cunju; Gu, Yifei; Li, Le; Wang, Hui; Huang, Wenhai; Zhou, Nai; Wang, Deping; Zhu, Yi; Xu, Jun; Luo, Shihua; Zhang, Changqing; Rahaman, Mohamed N

2014-03-01

Osteomyelitis (bone infection) is often difficult to cure. The commonly-used treatment of surgical debridement to remove the infected bone combined with prolonged systemic and local antibiotic treatment has limitations. In the present study, an injectable borate bioactive glass cement was developed as a carrier for the antibiotic vancomycin, characterized in vitro, and evaluated for its capacity to cure osteomyelitis in a rabbit tibial model. The cement (initial setting time = 5.8 ± 0.6 min; compressive strength = 25.6 ± 0.3 MPa) released vancomycin over ~25 days in phosphate-buffered saline, during which time the borate glass converted to hydroxyapatite (HA). When implanted in rabbit tibial defects infected with methicillin-resistant Staphylococcus aureus (MRSA)-induced osteomyelitis, the vancomycin-loaded cement converted to HA and supported new bone formation in the defects within 8 weeks. Osteomyelitis was cured in 87 % of the defects implanted with the vancomycin-loaded borate glass cement, compared to 71 % for the defects implanted with vancomycin-loaded calcium sulfate cement. The injectable borate bioactive glass cement developed in this study is a promising treatment for curing osteomyelitis and for regenerating bone in the defects following cure of the infection.

The development of low temperature curing adhesives

NASA Technical Reports Server (NTRS)

Green, H. E.; Sutherland, J. D.; Hom, J. M.; Sheppard, C. H.

1975-01-01

An approach for the development of a practical low temperature (293 K-311 K/68 F-100 F) curing adhesive system based on a family of amide/ester resins was studied and demonstrated. The work was conducted on resin optimization and adhesive compounding studies. An improved preparative method was demonstrated which involved the reaction of an amine-alcohol precursor, in a DMF solution with acid chloride. Experimental studies indicated that an adhesive formulation containing aluminum powder provided the best performance when used in conjunction with a commercial primer.

Analysis of curing of a sustained release coating formulation by application of NIR spectroscopy to monitor changes associated with glyceryl monostearate.

PubMed

Howland, Harris; Fahmy, Raafat; Hoag, Stephen W

2015-01-01

For controlled release, latex or pseudolatex coatings to function as designed, it must be cured at temperatures at or slightly above the polymer's glass transition temperature. The focus of this study is to develop an understanding of the curing process and to develop near infrared spectroscopy as a tool for monitoring curing. Differential scanning calorimetry studies were used to determine how the thermal properties of glyceryl monostearate (GMS) and its polymorphic forms relate to the extent of Eudragit® polymer coat curing at different curing temperatures. The different GMS melting endotherms were used to monitor the extent of curing and as references for model development. The calculated melting peak areas for the GMS were plotted versus time and found to be dependent on time and temperature used for curing. Principal component analysis and parallel factor analysis were used to investigate the effect of curing on the films and showed that spectral changes could be could be directly related to the changes associated with the GMS during curing. Partial least square models developed could predict the extent of curing and the final state of GMS post curing.

Room Temperature Curing Resin Systems for Graphite/Epoxy Composite Repair.

DTIC Science & Technology

1979-12-01

ROOM TEMPERATURE CURING RESIN SYSTEMS FOR GRAPHITE/EPOXY COMPOS--ETC(UI DEC 79 0 J CRABTREE N62269-79-C-G224 UNCLASSIFIE O80-46 NADC -781 1-6 NL END...Room Temperature Curing Resin Sys-U3 linal for Graphite/Epoxy Composite Repair •.Dec *79 NOR- -46h: V111IT NUM8ER(s) 4362269-79- ,722 S. PERFORMING...repair, composite repair room temperature cure resin , moderate temperature cure resins , epoxies, adhesives, vinyl eater polymers, anaerobic curing polymers

Heat resistant composite structure for shuttle applications (Ryton-B)

NASA Technical Reports Server (NTRS)

1972-01-01

A program was undertaken to characterize Ryton-B resin, develop graphite filament prepregs, undirectional laminates and determine the strength and heat resistance of the composite system. Through the use of a water soluble resin binder, high quality prepreg tape, three inches wide with 4 tows of HM-S were produced. The tape laminated to 0.00175 inch per ply. A wide range of properties in the cured resin and laminate were found using different curing conditions. The thermal stability and strength of molded laminates appears to be very dependent upon the cure cycle used for polymerization.

ASRM test report: Autoclave cure process development

NASA Technical Reports Server (NTRS)

Nachbar, D. L.; Mitchell, Suzanne

1992-01-01

ASRM insulated segments will be autoclave cured following insulation pre-form installation and strip wind operations. Following competitive bidding, Aerojet ASRM Division (AAD) Purchase Order 100142 was awarded to American Fuel Cell and Coated Fabrics Company, Inc. (Amfuel), Magnolia, AR, for subcontracted insulation autoclave cure process development. Autoclave cure process development test requirements were included in Task 3 of TM05514, Manufacturing Process Development Specification for Integrated Insulation Characterization and Stripwind Process Development. The test objective was to establish autoclave cure process parameters for ASRM insulated segments. Six tasks were completed to: (1) evaluate cure parameters that control acceptable vulcanization of ASRM Kevlar-filled EPDM insulation material; (2) identify first and second order impact parameters on the autoclave cure process; and (3) evaluate insulation material flow-out characteristics to support pre-form configuration design.

Development and characterization of soy-based epoxy resins and pultruded FRP composites

NASA Astrophysics Data System (ADS)

Zhu, Jiang

This dissertation focuses on the development, manufacture and characterization of novel soy-based epoxy FRP composites. Use of alternative epoxy resin systems derived from a renewable resource holds potential for low cost raw materials for the polymer and composite industries. Epoxidized Allyl Soyate (EAS) and Epoxidized Methyl Soyate (EMS) were developed from soybean oil with two chemical modification procedures: transesterification and epoxidation. This research investigates the curing characteristics and thermal and mechanical properties of the neat soyate resin systems. The derived soyate resins have higher reactivity and superior performance compared to commercially available epoxidized soybean oil. An efficient two-step curing method was developed in order to utilize these soyate resins to their full potential. The epoxy co-resin systems with varied soyate resin content were successfully used to fabricate composite material through pultrusion. The pultrusion resin systems with 30 wt% soyate resins yielded improved, or comparable mechanical properties with neat commercial resins. A finite element analysis of the heat transfer and curing process was performed to study the processing characterization on glass/epoxy composite pultrusion. This model can be used to establish baseline process variables and will benefit subsequent optimization. This research demonstrates that soy-based resins, especially EAS, show considerable promise as an epoxy resin supplement for use in polymer and composite structural applications. The new products derived from soybean oil can provide competitive performance, low cost and environmental advantages.

Coating Characterization with the Quartz Crystal Microbalance

NASA Astrophysics Data System (ADS)

Sturdy, Lauren F.

The quartz crystal microbalance is a sensitive tool that can be used to measure the mass, modulus and phase angle of films of appropriate thicknesses. It is can be applied to systems with very varied properties, from liquid to solid, and under many different conditions. In this thesis its capabilities have been used to study the properties of several different systems of relevance to the coatings, art conservation, and rubber communities, in the process of which new techniques and tools were developed to analyze data and improve QCM data collection and experimental design. Alkyd resins, which have been used in artists' paints since the twentieth century, are the subject of the first studies. Alkyds are oil-modified polyesters. These resins are of interest because of their relatively recent use in art and how little is known of the mechanical properties in the early stages of cure. The QCM was shown to be sensitive to the curing process, changes in temperature, and mass change due to exposure to water. Kinetic studies during the first days of curing showed that the curing process can be divided into three regions. The first is dominated by solvent evaporation. In the second, oxygen absorption dominates and the mechanical properties change rapidly. The final stage extends from when the film is touch dry after about a day to years and is characterized by mass loss and continued increases in the modulus. Studying the curing at different temperatures revealed that the reactions do proceed much more rapidly at higher temperatures and an overall energy of activation was calculated for the curing process. The mechanical properties of alkyd resins containing zinc oxide, a white pigment, were studied with the QCM, nanoindentation and dynamic mechanical analysis. These measurements showed increases in the modulus with the inclusion of zinc oxide, and the QCM data showed that the second region started at earlier times as the pigment concentration was increased. Linseed oil is one of the starting materials for many alkyd resins and should cure similarly since the primary curing mechanisms are the same. It takes longer to cure than alkyds because it begins with no initial polymerization. Linseed oil was harder to study, as obtaining even films was difficult, multiple peaks at a single harmonic were observed, and the material properties during the early stages of curing led to a region where viscoelastic properties could not be calculated. To facilitate studying linseed oil, a multiple peak fitting method was developed to extract data from unusual peak shapes. With this ability, measurements at short times could be obtained despite poor film quality. Although linseed oil begins as a softer material than alkyds, its curing follows the same patterns as alkyd resins, exhibiting mass gain followed by mass loss, and sharp increases in modulus and decreases in phase angle during the early stages of curing. Having demonstrated the ability of the QCM to monitor curing, the QCM was also applied to uncrosslinked rubber systems. Rubbers, like the drying oils, contain double bonds which can react with oxygen, so first the oxidation of these materials was studied. In further studies oxidation was undesirable, so protocols were developed to limit oxidation. Measurements were made of homopolymers at different temperatures and the QCM measurements appear to be consistent with time-temperature superposition results obtained at lower frequencies. Blends of the various rubbers were studied and compared with models. The mechanical properties measured by the QCM were between the Voigt and Reuss predictions for most blends studied. Modeling the expected QCM response of layered rubbers matched the predictions of the Reuss model but not the measured values of the rubber blends, suggesting that the QCM is sensitive to different morphologies. Measurements with the QCM expanded our understanding of a variety of systems and proved to be a useful tool to measure mechanical changes during processes which are difficult to study by other methods.

UV-cured polymer optics

NASA Astrophysics Data System (ADS)

Piñón, Victor; Santiago, Freddie; Vogelsberg, Ashten; Davenport, Amelia; Cramer, Neil

2017-10-01

Although many optical-quality glass materials are available for use in optical systems, the range of polymeric materials is limited. Polymeric materials have some advantages over glass when it comes to large-scale manufacturing and production. In smaller scale systems, they offer a reduction in weight when compared to glass counterparts. This is especially important when designing optical systems meant to be carried by hand. We aimed to expand the availability of polymeric materials by exploring both crown-like and flint-like polymers. In addition, rapid and facile production was also a goal. By using UV-cured thiolene-based polymers, we were able to produce optical materials within seconds. This enabled the rapid screening of a variety of polymers from which we down-selected to produce optical flats and lenses. We will discuss problems with production and mitigation strategies in using UV-cured polymers for optical components. Using UV-cured polymers present a different set of problems than traditional injection-molded polymers, and these issues are discussed in detail. Using these produced optics, we integrated them into a modified direct view optical system, with the end goal being the development of drop-in replacements for glass components. This optical production strategy shows promise for use in lab-scale systems, where low-cost methods and flexibility are of paramount importance.

The ethics of talking about 'HIV cure'.

PubMed

Rennie, Stuart; Siedner, Mark; Tucker, Joseph D; Moodley, Keymanthri

2015-03-27

In 2008, researchers reported that Timothy Brown (the 'Berlin Patient'), a man with HIV infection and leukemia, received a stem-cell transplant that removed HIV from his body as far as can be detected. In 2013, an infant born with HIV infection received anti-retroviral treatment shortly after birth, but was then lost to the health care system for the next six months. When tested for HIV upon return, the child (the 'Mississippi Baby') had no detectable viral load despite cessation of treatment. These remarkable clinical developments have helped reinvigorate the field of 'HIV cure' research. Although this research field is largely in a pre-clinical phase, talk about curing HIV has become a regular feature in the global mass media. This paper explores the language of HIV cure from philosophical, ethical and historical perspectives. Examination of currently influential definitions of 'functional' and 'sterilizing' HIV cure reveal that these conceptualizations are more complicated than they seem. Cure is often understood in narrowly biomedical terms in isolation from the social and psychological dimensions of illness. Contemporary notions of HIV cure also inherit some of the epistemic problems traditionally associated with cures for other health conditions, such as cancer. Efforts to gain greater conceptual clarity about cure lead to the normative question of how 'HIV cure research' ought to be talked about. We argue that attention to basic concepts ethically matter in this context, and identify advantages as well as potential pitfalls of how different HIV/AIDS stakeholders may make use of the concept of cure. While concepts other than cure (such as remission) may be appropriate in clinical contexts, use of the word cure may be justified for other important purposes in the struggle against HIV/AIDS.

Surface engineering of nanoparticles with macromolecules for epoxy curing: Development of super-reactive nitrogen-rich nanosilica through surface chemistry manipulation

NASA Astrophysics Data System (ADS)

Jouyandeh, Maryam; Jazani, Omid Moini; Navarchian, Amir H.; Shabanian, Meisam; Vahabi, Henri; Saeb, Mohammad Reza

2018-07-01

Curing behavior of epoxy-based nanocomposites depends on dispersion state of nanofillers and their physical and chemical interactions with the curing moieties. In this work, a systematic approach was introduced for chemical functionalization of nanoparticles with macromolecules in order to enrich crosslinking potential of epoxy/amine systems, particularly at late stages of cure where the curing is diffusion-controlled. Super-reactive hyperbranched polyethylenimine (PEI)-attached nanosilica was materialized in this work to facilitate epoxy-amine curing. Starting from coupling [3-(2,3-epoxypropoxy) propyl] trimethoxysilane (EPPTMS) with hyperbranched PEI, a super-reactive macromolecule was obtained and subsequently grafted onto the nanosilica surface. Eventually, a thermally-stable highly-curable nanocomposite was attained by replacement of amine and imine groups of the PEI with imide and amide groups through the reaction with pyromellitic acid dianhydride. Fourier-transform infrared spectrophotometry, X-ray diffractometry, X-ray photoelectron spectroscopy and transmission electron microscopy approved successful grafting of polymer chains onto the nanosilica surface. Thermogravimetric analyses approved a relatively high grafting ratio of ca. 21%. Curing potential of the developed super-reactive nanoparticle was uncovered through nonisothermal differential scanning calorimetry signifying an enthalpy rise of ca. 120 J/g by addition of 2 wt.% to epoxy at 5 °C/min heating rate. Even at low concentration of 0.5 wt.%, the glass transition temperature of epoxy increased from 128 to 156 °C, demonstrating prolonged crosslinking.

A New Epoxy-Based Layered Silicate Nanocomposite Using a Hyperbranched Polymer: Study of the Curing Reaction and Nanostructure Development.

PubMed

Cortés, Pilar; Fraga, Iria; Calventus, Yolanda; Román, Frida; Hutchinson, John M; Ferrando, Francesc

2014-03-04

Polymer layered silicate (PLS) nanocomposites have been prepared with diglycidyl ether of bisphenol-A (DGEBA) epoxy resin as the matrix and organically modified montmorillonite (MMT) as the clay nanofiller. Resin-clay mixtures with different clay contents (zero, two, five and 10 wt%) were cured, both isothermally and non-isothermally, using a poly(ethyleneimine) hyperbranched polymer (HBP), the cure kinetics being monitored by differential scanning calorimetry (DSC). The nanostructure of the cured nanocomposites was characterized by small angle X-ray scattering (SAXS) and transmission electron microscopy (TEM), and their mechanical properties were determined by dynamic mechanical analysis (DMA) and impact testing. The results are compared with an earlier study of the structure and properties of the same DGEBA-MMT system cured with a polyoxypropylene diamine, Jeffamine. There are very few examples of the use of HBP as a curing agent in epoxy PLS nanocomposites; here, it is found to enhance significantly the degree of exfoliation of these nanocomposites compared with those cured with Jeffamine, with a corresponding enhancement in the impact energy for nanocomposites with the low clay content of 2 wt%. These changes are attributed to the different cure kinetics with the HBP, in which the intra-gallery homopolymerization reaction is accelerated, such that it occurs before the bulk cross-linking reaction.

Using a centrifuge for quality control of pre-wetted lightweight aggregate in internally cured concrete

NASA Astrophysics Data System (ADS)

Miller, Albert E.

Early age shrinkage of cementitious systems can result in an increased potential for cracking which can lead to a reduction in service life. Early age shrinkage cracking can be particularly problematic for high strength concretes, which are often specified due to their high strength and low permeability. However, these high strength concretes frequently exhibit a reduction in the internal relative humidity (RH) due to the hydration reaction (chemical shrinkage) and self-desiccation which results in a bulk shrinkage, termed autogenous shrinkage, which is substantial at early ages. Due to the low permeability of these concretes, standard external curing is not always efficient in addressing this reduction in internal RH since the penetration of water can be limited. Internal curing has been developed to reduce autogenous shrinkage. Internally cured mixtures use internal reservoirs filled with fluid (generally water) that release this fluid at appropriate times to counteract the effects of self-desiccation thereby maintaining a high internal RH. Internally cured concrete is frequently produced in North America using pre-wetted lightweight aggregate. One important aspect associated with preparing quality internally cured concrete is being able to determine the absorbed moisture and surface moisture associated with the lightweight aggregate which enables aggregate moisture corrections to be made for the concrete mixture. This thesis represents work performed to develop a test method using a centrifuge to determine the moisture state of pre-wetted fine lightweight aggregate. The results of the test method are then used in a series of worksheets that were developed to assist field technicians when performing the tests and applying the results to a mixture design. Additionally, research was performed on superabsorbent polymers to assess their ability to be used as an internal curing reservoir.

Molecular Mobility in Hyperbranched Polymers and Their Interaction with an Epoxy Matrix

PubMed Central

Román, Frida; Colomer, Pere; Calventus, Yolanda; Hutchinson, John M.

2016-01-01

The molecular mobility related to the glass transition and secondary relaxations in a hyperbranched polyethyleneimine, HBPEI, and its relaxation behaviour when incorporated into an epoxy resin matrix are investigated by dielectric relaxation spectroscopy (DRS) and dynamic mechanical analysis (DMA). Three systems are analysed: HBPEI, epoxy and an epoxy/HBPEI mixture, denoted ELP. The DRS behaviour is monitored in the ELP system in three stages: prior to curing, during curing, and in the fully cured system. In the stage prior to curing, DRS measurements show three dipolar relaxations: γ, β and α, for all systems (HBPEI, epoxy and ELP). The α-relaxation for the ELP system deviates significantly from that for HBPEI, but superposes on that for the epoxy resin. The fully cured thermoset displays both β- and α-relaxations. In DMA measurements, both α- and β-relaxations are observed in all systems and in both the uncured and fully cured systems, similar to the behaviour identified by DRS. PMID:28773319

Development of informational-communicative system, created to improve medical help for family medicine doctors.

PubMed

Smiianov, Vladyslav A; Dryha, Natalia O; Smiianova, Olha I; Obodyak, Victor K; Zudina, Tatyana O

2018-01-01

Introduction: Today mobile health`s protection service has no concrete meaning. As an research object it was called mHealth and named by Global observatory of electronic health`s protection as "Doctor and social health practice that can be supported by any mobile units (mobile phones or smartphones), units for patient`s health control, personal computers and other units of non-wired communication". An active usage of SMS in programs for patients` cure regimen keeping was quiet predictable. Mobile and electronic units only begin their development in medical sphere. Thus, to solve all health`s protection system reformation problems a special memorandum about cooperation in creating E-Health system in Ukraine was signed. The aim: Development of ICS for monitoring and non-infection ill patients` informing system optimization as a first level of medical help. Materials and methods: During research, we used systematical approach, meta-analysis, informational-analytical systems` schemes projection, expositive modeling. Developing the backend (server part of the site), we used next technologies: 1) the Apache web server; 2) programming language PHP; 3) Yii 2 PHP Framework. In the frontend developing were used the following technologies (client part of the site): 1) Bootstrap 3; 2) Vue JS Framework. Results and conclusions: Created duo-channel system "doctor-patient" and "patient-doctor" will allow usual doctors of family medicine (DFM) take the interactive dispensary cure and avoid uncontrolled illness progress. Doctor will monitor basic physical data of patient`s health and curing process. The main goal is to create automatic system to allow doctor regularly write periodical or non-periodical notifications, get patients` questioning answers and spread information between doctor and patient; that will optimize work of DFMs.

Large-scale development of SSR markers in tobacco and construction of a linkage map in flue-cured tobacco

PubMed Central

Tong, Zhijun; Xiao, Bingguang; Jiao, Fangchan; Fang, Dunhuang; Zeng, Jianmin; Wu, Xingfu; Chen, Xuejun; Yang, Jiankang; Li, Yongping

2016-01-01

Tobacco (Nicotiana tabacum L.), particularly flue-cured tobacco, is one of the most economically important nonfood crops and is also an important model system in plant biotechnology. Despite its importance, only limited molecular marker resources are available for genome analysis, genetic mapping, and breeding. Simple sequence repeats (SSR) are one of the most widely-used molecular markers, having significant advantages including that they are generally co-dominant, easy to use, abundant in eukaryotic organisms, and produce highly reproducible results. In this study, based on the genome sequence data of flue-cured tobacco (K326), we developed a total of 13,645 mostly novel SSR markers, which were working in a set of eighteen tobacco varieties of four different types. A mapping population of 213 backcross (BC1) individuals, which were derived from an intra-type cross between two flue-cured tobacco varieties, Y3 and K326, was selected for mapping. Based on the newly developed SSR markers as well as published SSR markers, we constructed a genetic map consisting of 626 SSR loci distributed across 24 linkage groups and covering a total length of 1120.45 cM with an average distance of 1.79 cM between adjacent markers, which is the highest density map of flue-cured tobacco till date. PMID:27436948

Quantitative NDE applied to composites and metals

NASA Technical Reports Server (NTRS)

Heyman, Joseph S.; Winfree, William P.; Parker, F. Raymond; Heath, D. Michele; Welch, Christopher S.

1989-01-01

Research at the NASA/Langley Research Center concerning quantitative NDE of composites and metals is reviewed. The relationship between ultrasonics and polymer cure is outlined. NDE models are presented, which can be used to develop measurement technologies for characterizing the curing of a polymer system for composite materials. The models can be used to determine the glass transition temperature, the degree of cure, and the cure rate. The application of the model to control autoclave processing of composite materials is noted. Consideration is given to the use of thermal diffusion models combined with controlled thermal input measurements to determine the thermal diffusivity of materials. Also, a two-dimensional physical model is described that permits delaminations in samples of Space Shuttle Solid Rocket Motors to be detected in thermograms in the presence of cooling effects and uneven heating.

40 CFR 63.4165 - How do I determine the emission capture system efficiency?

Code of Federal Regulations, 2010 CFR

2010-07-01

... system; coating solvent flash-off and coating, curing, and drying occurs within the capture system and... when being moved between a spray booth and a curing oven. (b) If the capture system does not meet both... surface preparation activities and drying or curing time. (c) Liquid-to-uncaptured-gas protocol using a...

Fiber optic sensor design for chemical process and environmental monitoring

NASA Astrophysics Data System (ADS)

Mahendran, R. S.; Harris, D.; Wang, L.; Machavaram, V. R.; Chen, R.; Kukureka, St. N.; Fernando, G. F.

2007-07-01

Cure monitoring is a term that is used to describe the cross-linking reactions in a thermosetting resin system. Advanced fiber reinforced composites are being used increasingly in a number of industrial sectors including aerospace, marine, sport, automotive and civil engineering. There is a general realization that the processing conditions that are used to manufacture the composites can have a major influence on its hot-wet mechanical properties. This paper is concerned with the design and demonstration of a number of sensor designs for in-situ cure monitoring of a model thermosetting resin system. Simple fixtures were constructed to enable a pair of cleaved optical fibers with a defined gap between the end-faces to be held in position. The resin system was introduced into this gap and the cure kinetics were followed by transmission infrared spectroscopy. A semi-empirical model was used to describe the cure process using the data obtained at different cure temperatures. The same sensor system was used to detect the ingress of moisture in the cured resin system.

A One-Component, Fast-Cure, and Economical Epoxy Resin System Suitable for Liquid Molding of Automotive Composite Parts.

PubMed

Wang, Yiru; Liu, Wanshuang; Qiu, Yiping; Wei, Yi

2018-04-27

Imidazole cured epoxy resin systems were evaluated for one-component, fast-curing resins for liquid molding of automotive composite parts according to industry requirements. It was demonstrated that an epoxy resin-1-(cyanoethyl)-2-ethyl-4-methylimidazol(EP-1C2E4MIM) system would cure in a few minutes at 120 °C, while exhibiting acceptable pot life, viscosity profiles, and low water absorption. Moreover, this system yielded high T g parts with mechanical properties similar to the amine-epoxy systems, which are the mainstream two-component epoxy resin systems for automobiles.

A One-Component, Fast-Cure, and Economical Epoxy Resin System Suitable for Liquid Molding of Automotive Composite Parts

PubMed Central

Wang, Yiru; Qiu, Yiping; Wei, Yi

2018-01-01

Imidazole cured epoxy resin systems were evaluated for one-component, fast-curing resins for liquid molding of automotive composite parts according to industry requirements. It was demonstrated that an epoxy resin-1-(cyanoethyl)-2-ethyl-4-methylimidazol(EP-1C2E4MIM) system would cure in a few minutes at 120 °C, while exhibiting acceptable pot life, viscosity profiles, and low water absorption. Moreover, this system yielded high Tg parts with mechanical properties similar to the amine-epoxy systems, which are the mainstream two-component epoxy resin systems for automobiles. PMID:29702575

A New Epoxy-Based Layered Silicate Nanocomposite Using a Hyperbranched Polymer: Study of the Curing Reaction and Nanostructure Development

PubMed Central

Cortés, Pilar; Fraga, Iria; Calventus, Yolanda; Román, Frida; Hutchinson, John M.; Ferrando, Francesc

2014-01-01

Polymer layered silicate (PLS) nanocomposites have been prepared with diglycidyl ether of bisphenol-A (DGEBA) epoxy resin as the matrix and organically modified montmorillonite (MMT) as the clay nanofiller. Resin-clay mixtures with different clay contents (zero, two, five and 10 wt%) were cured, both isothermally andnon-isothermally, using a poly(ethyleneimine) hyperbranched polymer (HBP), the cure kinetics being monitored by differential scanning calorimetry (DSC). The nanostructure of the cured nanocomposites was characterized by small angle X-ray scattering (SAXS) and transmission electron microscopy (TEM), and their mechanical properties were determined by dynamic mechanical analysis (DMA) and impact testing. The results are compared with an earlier study of the structure and properties of the same DGEBA-MMT system cured with a polyoxypropylene diamine, Jeffamine. There are very few examples of the use of HBP as a curing agent in epoxy PLS nanocomposites; here, it is found to enhance significantly the degree of exfoliation of these nanocomposites compared with those cured with Jeffamine, with a corresponding enhancement in the impact energy for nanocomposites with the low clay content of 2 wt%. These changes are attributed to the different cure kinetics with the HBP, in which the intra-gallery homopolymerization reaction is accelerated, such that it occurs before the bulk cross-linking reaction. PMID:28788542

The synthesis and dynamics research of new curing agent for epoxy resin

NASA Astrophysics Data System (ADS)

Peng, Yongli; Huang, Hengyu; Sun, Yong

2017-05-01

Two-step synthesis of trimellitic anhydride trimellitic anhydride n - butyl ester (TMNB) was introduced which could be used as an epoxy resin curing agent. The kinetics of the curing reaction was analyzed by N-order model and autocatalytic model. The curing kinetics parameters, the results show that the curing activation energy (Ea) of this system was 35.79kJ / mol. The kinetic equation of curing was d/a d t =2.1061 ×104e x p (-35.79/R T ) α0.5163(l-α ) 0.366 . Combined with β-1 / T extrapolation and experimental adjustment to obtain the resin system curing process: 75°C for 1h, 140°C for 3h, 160°C for 2h.

Relationship of Cure Temperature to Mechanical, Physical, and Dielectric Performance of PDMS Glass Composite for Electric Motor Insulation

NASA Technical Reports Server (NTRS)

Miller, Sandi G.; Becker, Kathleen; Williams, Tiffany S.; Scheiman, Daniel A.; McCorkle, Linda S.; Heimann, Paula J.; Ring, Andrew; Woodworth, Andrew

2017-01-01

Achieving NASAs aggressive fuel burn and emission reduction for N-plus-3 aircraft will require hybrid electric propulsion system in which electric motors driven by either power generated from turbine or energy storage system will power the fan for propulsion. Motors designed for hybrid electric aircraft are expected to operate at medium to high voltages over long durations in a high altitude service environment. Such conditions have driven research toward the development of wire insulation with improved mechanical strength, thermal stability and increased breakdown voltage. The silicone class of materials has been considered for electric wire insulation due to its inherent thermal stability, dielectric strength and mechanical integrity. This paper evaluates the dependence of these properties on the cure conditions of a polydimethyl-siloxane (PDMS) elastomer; where both cure temperature and base-to-catalyst ratio were varied. The PDMS elastomer was evaluated as a bulk material and an impregnation matrix within a lightweight glass veil support. The E-glass support was selected for mechanical stiffness and dielectric strength. This work has shown a correlation between cure conditions and material physical properties. Tensile strength increased with cure temperature whereas breakdown voltage tended to be independent of process variations. The results will be used to direct material formulation based on specific insulation requirements.

Correlation between clinical performance and degree of conversion of resin cements: a literature review

PubMed Central

DE SOUZA, Grace; BRAGA, Roberto Ruggiero; CESAR, Paulo Francisco; LOPES, Guilherme Carpena

2015-01-01

Resin-based cements have been frequently employed in clinical practice to lute indirect restorations. However, there are numerous factors that may compromise the clinical performance of those cements. The aim of this literature review is to present and discuss some of the clinical factors that may affect the performance of current resin-based luting systems. Resin cements may have three different curing mechanisms: chemical curing, photo curing or a combination of both. Chemically cured systems are recommended to be used under opaque or thick restorations, due to the reduced access of the light. Photo-cured cements are mainly indicated for translucent veneers, due to the possibility of light transmission through the restoration. Dual-cured are more versatile systems and, theoretically, can be used in either situation, since the presence of both curing mechanisms might guarantee a high degree of conversion (DC) under every condition. However, it has been demonstrated that clinical procedures and characteristics of the materials may have many different implications in the DC of currently available resin cements, affecting their mechanical properties, bond strength to the substrate and the esthetic results of the restoration. Factors such as curing mechanism, choice of adhesive system, indirect restorative material and light-curing device may affect the degree of conversion of the cement and, therefore, have an effect on the clinical performance of resin-based cements. Specific measures are to be taken to ensure a higher DC of the luting system to be used. PMID:26398507

FT-IR Investigation of Hoveyda-Grubbs'2{sup nd} Generation Catalyst in Self-Healing Epoxy Mixtures

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

Guadagno, Liberata; Naddeo, Carlo; Vittoria, Vittoria

The development of smart composites capable of self-repair on aeronautical structures is still at the planning stage owing to complex issues to overcome. A very important issue to solve concerns the components' stability of the proposed composites which are compromised at the cure temperatures necessary for good performance of the composite. In this work we analyzed the possibility to apply Hoveyda Grubbs' second generation catalyst (HG2) to develop self-healing systems. Our experimental results have shown critical issues in the use of epoxy precursors in conjunction with Hoveyda-Grubbs II metathesis catalyst. However, an appropriate curing cycle of the self-healing mixture permitsmore » to overcome the critical issues making possible high temperatures for the curing process without deactivating self-repair activity.« less

Exploratory Development of Corrosion Inhibiting Primers

DTIC Science & Technology

1977-07-01

Phenolic Hardener From previous studies, phenol formaldehyde resins of the novolac (two-step) type have given superior properties when used to cure epoxy...novolacs and three resole (one-step) type phenol- formaldehyde resins which also perform as epoxide curing agents. First, Model #1, as de;crihed in Section...results. Varcum 4326 resin was chosen at this stage for further use with the model systems. It is a low molecular weight phenol- formaldehyde resin used

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

Spellman, G.P.

A relatively new advanced composite matrix, polycyanate ester, was evaluated for cure shrinkage. The chemical cure shrinkage of composites is difficult to model but a number of clever experimental techniques are available to the investigator. In this work the method of curing a prepreg layup on top of a previously cured laminate of identical ply composition is utilized. The polymeric matrices used in advanced composites have been primarily epoxies and therefore a common system of this type, Fiberite 3501-6, was used as a base case material. Three polycyanate matrix systems were selected for the study. These are: Fiberite 954-2A, YLAmore » RS-3, and Bryte Technology BTCy-1. The first three of these systems were unidirectional prepreg with carbon fiber reinforcement. The Bryte Technology material was reinforced with E-glass fabric. The technique used to evaluate cure shrinkage results in distortion of the flatness of an otherwise symmetric laminate. The first laminate is cured in a conventional fashion. An identical layup is cured on this first laminate. During the second cure all constituents are exposed to the same thermal cycles. However, only the new portion of the laminate will experience volumetric changes associate with matrix cure. The additional strain of cure shrinkage results in an unsymmetric distribution of residual stresses and an associated warpage of the laminate. The baseline material, Fiberite 3501-6, exhibited cure shrinkage that was in accordance with expectations. Cure strains were {minus}4.5E-04. The YLA RS-3 material had cure strains somewhat lower at {minus}3.2E-04. The Fiberite 954-2A cure strain was {minus}1.5E-04 that is 70% lower than the baseline material. The glass fabric material with the Bryte BTCy-1 matrix did not result in meaningful results because the processing methods were not fully compatible with the material.« less

When to start paediatric testing of the adult HIV cure research agenda?

PubMed

Shah, Seema K

2017-02-01

Ethical guidelines recommend that experimental interventions should be tested in adults first before they are tested and approved in children. Some challenge this paradigm, however, and recommend initiating paediatric testing after preliminary safety testing in adults in certain cases. For instance, commentators have argued for accelerated testing of HIV vaccines in children. Additionally, HIV cure research on the use of very early therapy (VET) in infants, prompted in part by the Mississippi baby case, is one example of a strategy that is currently being tested in infants before it has been well tested in adults. Because infants' immune systems are still developing, the timing of HIV transmission is easier to identify in infants than in adults, and infants who receive VET might never develop the viral reservoirs that make HIV so difficult to eradicate, infants may be uniquely situated to achieve HIV cure or sustained viral remission. Several commentators have now argued for earlier initiation of HIV cure interventions other than (or in addition to) VET in children. HIV cure research is therefore a good case for re-examining the important question of when to initiate paediatric research. I will argue that, despite the potential for HIV cure research to benefit children and the scientific value of involving children in this research, the HIV cure agenda should not accelerate the involvement of children for the following reasons: HIV cure research is highly speculative, risky, aimed at combination approaches and does not compare favourably with the available alternatives. I conclude by drawing general implications for the initiation of paediatric testing, including that interventions that have to be used in combination with others and cures for chronic diseases may not be valuable enough to justify early paediatric testing. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/.

Characterization of the relationship of the cure cycle chemistry to cure cycle processing properties

NASA Technical Reports Server (NTRS)

Kranbuehl, D. E.

1986-01-01

Dynamic Dielectric measurements made over a wide range of frequency provide a sensitive and convenient means for monitoring the cure process in thermosets and thermoplastics. The measurement of dielectric relaxation is one of only a few instrumental techniques available for studying molecular properties in both the liquid and solid states. Furthermore, it is probably the only convenient experimental technique for studying the polymerization process of going from a monomeric liquid of varying viscosity to a crosslinked, insoluble, high temperature solid. The objective of the research is to develop on-line dielectric instrumentation for quantitative nondestructive material evaluation and closed loop smart cure cycle control. The key is to relate the chemistry of the cure cycle process to the dielectric properties of the polymer system by correlating the time, temperature, and frequency dependent dielectric measurements with chemical characterization measurements. Measurement of the wide variation in magnitude of the complex permittivity with both frequency and state of cure, coupled with chemical characterization work, have been shown in the laboratory to have the potential to determine: resin quality, composition and age; cure cycle window boundaries; onset of flow and point of maximum flow; extent of and completion of reaction; evolution of volatiles; T sub g; and, crosslinking and molecular weight buildup.

[Development of visible-light cured FRP denture].

PubMed

Yu, P Y

1990-06-01

Acrylic denture may be fractured easily because it has a relatively poor resistance to stresses of impact, and the thick acrylic denture base also uncomforted to denture wearers. In this study, for improvement of the mechanical properties, the FRP is applied to the denture base, and try to make a thin denture base. Using the visible light-curing system, the laboratory fabrication time is saved dramatically. To develop the visible light-cured FRP denture base, with various combination of matrix resins and reinforcements, the physical properties of FRP plates were investigated first. From the results of the bending test, hardness test, and manipulation considering, the sateen weave's glasscloth was choose as the reinforcement of the prepreg. The matrix resin of Bis-GMA/UDMA/3G at 48/48/4 wt% was determined. The 3 plies glasscloth included FRP plate is 0.8 mm thickness has the maximum bending strength about 50 kgf/mm2, which is about 5 times larger than that of acrylic resin. Succeeding the study of above, the FRP denture base was fabricated by using the 0.8 mm thickness 3 plies included prepreg. This repreg is manufactured in sheet form beforehand, which is ease to manipulate at laboratory. By using the visible light curing system, it is only taken 10 min. to make a FRP denture base. The following procedures of fabricating a FRP denture is the same as metalplate denture. The visible-light cured FRP denture has some advantages such as accuracy of fit, ease of fabrication and manipulation, and only 0.8 mm thickness but has superior strength.

40 CFR 63.3965 - How do I determine the emission capture system efficiency?

Code of Federal Regulations, 2010 CFR

2010-07-01

...; coating solvent flash-off, curing, and drying occurs within the capture system; and the removal or... spray booth and a curing oven. (b) Measuring capture efficiency. If the capture system does not meet... surface preparation activities and drying and curing time. (c) Liquid-to-uncaptured-gas protocol using a...

Advancements in Developing Strategies for Sterilizing and Functional HIV Cures

PubMed Central

Li, Haoyang; Hua, Chen; Zhang, Hanzhen

2017-01-01

Combined antiretroviral therapy (cART) has been successful in prolonging lifespan and reducing mortality of patients infected with human immunodeficiency virus (HIV). However, the eradication of latent HIV reservoirs remains a challenge for curing HIV infection (HIV cure) because of HIV latency in primary memory CD4+ T cells. Currently, two types of HIV cures are in development: a “sterilizing cure” and a “functional cure.” A sterilizing cure refers to the complete elimination of replication-competent proviruses in the body, while a functional cure refers to the long-term control of HIV replication without treatment. Based on these concepts, significant progress has been made in different areas. This review focuses on recent advancements and future prospects for HIV cures. PMID:28529952

Toward 3D Printing of Medical Implants: Reduced Lateral Droplet Spreading of Silicone Rubber under Intense IR Curing.

PubMed

Stieghorst, Jan; Majaura, Daniel; Wevering, Hendrik; Doll, Theodor

2016-03-01

The direct fabrication of silicone-rubber-based individually shaped active neural implants requires high-speed-curing systems in order to prevent extensive spreading of the viscous silicone rubber materials during vulcanization. Therefore, an infrared-laser-based test setup was developed to cure the silicone rubber materials rapidly and to evaluate the resulting spreading in relation to its initial viscosity, the absorbed infrared radiation, and the surface tensions of the fabrication bed's material. Different low-adhesion materials (polyimide, Parylene-C, polytetrafluoroethylene, and fluorinated ethylenepropylene) were used as bed materials to reduce the spreading of the silicone rubber materials by means of their well-known weak surface tensions. Further, O2-plasma treatment was performed on the bed materials to reduce the surface tensions. To calculate the absorbed radiation, the emittance of the laser was measured, and the absorptances of the materials were investigated with Fourier transform infrared spectroscopy in attenuated total reflection mode. A minimum silicone rubber spreading of 3.24% was achieved after 2 s curing time, indicating the potential usability of the presented high-speed-curing process for the direct fabrication of thermal-curing silicone rubbers.

Might dolutegravir be part of a functional cure for HIV?

PubMed

Wainberg, Mark A; Han, Ying-Shan; Mesplède, Thibault

2016-05-01

Antiretroviral therapy (ART) has greatly decreased HIV-related morbidity and mortality. However, HIV can establish viral reservoirs that evade both the immune system and ART. Dolutegravir (DTG) is a second-generation integrase strand transfer inhibitor (INSTI) related to the first-generation INSTIs raltegravir (RAL) and elvitegravir (EVG). DTG shows a higher genetic barrier to the development of HIV-1 resistance than RAL and EVG. More interestingly, clinical resistance mutations to DTG in treatment-naïve patients have not been observed to date. This review summarizes recent studies on strategies toward a cure for HIV, explores resistance profiles of DTG, and discusses how DTG might help in finding a functional cure for HIV.

3D silicone rubber interfaces for individually tailored implants.

PubMed

Stieghorst, Jan; Bondarenkova, Alexandra; Burblies, Niklas; Behrens, Peter; Doll, Theodor

2015-01-01

For the fabrication of customized silicone rubber based implants, e.g. cochlear implants or electrocortical grid arrays, it is required to develop high speed curing systems, which vulcanize the silicone rubber before it runs due to a heating related viscosity drop. Therefore, we present an infrared radiation based cross-linking approach for the 3D-printing of silicone rubber bulk and carbon nanotube based silicone rubber electrode materials. Composite materials were cured in less than 120 s and material interfaces were evaluated with scanning electron microscopy. Furthermore, curing related changes in the mechanical and cell-biological behaviour were investigated with tensile and WST-1 cell biocompatibility tests. The infrared absorption properties of the silicone rubber materials were analysed with fourier transform infrared spectroscopy in transmission and attenuated total reflection mode. The heat flux was calculated by using the FTIR data, emissivity data from the infrared source manufacturer and the geometrical view factor of the system.

A Central Support System Can Facilitate Implementation and Sustainability of a Classroom-Based Undergraduate Research Experience (CURE) in Genomics

PubMed Central

Lopatto, David; Hauser, Charles; Jones, Christopher J.; Paetkau, Don; Chandrasekaran, Vidya; Dunbar, David; MacKinnon, Christy; Stamm, Joyce; Alvarez, Consuelo; Barnard, Daron; Bedard, James E. J.; Bednarski, April E.; Bhalla, Satish; Braverman, John M.; Burg, Martin; Chung, Hui-Min; DeJong, Randall J.; DiAngelo, Justin R.; Du, Chunguang; Eckdahl, Todd T.; Emerson, Julia; Frary, Amy; Frohlich, Donald; Goodman, Anya L.; Gosser, Yuying; Govind, Shubha; Haberman, Adam; Hark, Amy T.; Hoogewerf, Arlene; Johnson, Diana; Kadlec, Lisa; Kaehler, Marian; Key, S. Catherine Silver; Kokan, Nighat P.; Kopp, Olga R.; Kuleck, Gary A.; Lopilato, Jane; Martinez-Cruzado, Juan C.; McNeil, Gerard; Mel, Stephanie; Nagengast, Alexis; Overvoorde, Paul J.; Parrish, Susan; Preuss, Mary L.; Reed, Laura D.; Regisford, E. Gloria; Revie, Dennis; Robic, Srebrenka; Roecklien-Canfield, Jennifer A.; Rosenwald, Anne G.; Rubin, Michael R.; Saville, Kenneth; Schroeder, Stephanie; Sharif, Karim A.; Shaw, Mary; Skuse, Gary; Smith, Christopher D.; Smith, Mary; Smith, Sheryl T.; Spana, Eric P.; Spratt, Mary; Sreenivasan, Aparna; Thompson, Jeffrey S.; Wawersik, Matthew; Wolyniak, Michael J.; Youngblom, James; Zhou, Leming; Buhler, Jeremy; Mardis, Elaine; Leung, Wilson; Threlfall, Jennifer; Elgin, Sarah C. R.

2014-01-01

In their 2012 report, the President's Council of Advisors on Science and Technology advocated “replacing standard science laboratory courses with discovery-based research courses”—a challenging proposition that presents practical and pedagogical difficulties. In this paper, we describe our collective experiences working with the Genomics Education Partnership, a nationwide faculty consortium that aims to provide undergraduates with a research experience in genomics through a scheduled course (a classroom-based undergraduate research experience, or CURE). We examine the common barriers encountered in implementing a CURE, program elements of most value to faculty, ways in which a shared core support system can help, and the incentives for and rewards of establishing a CURE on our diverse campuses. While some of the barriers and rewards are specific to a research project utilizing a genomics approach, other lessons learned should be broadly applicable. We find that a central system that supports a shared investigation can mitigate some shortfalls in campus infrastructure (such as time for new curriculum development, availability of IT services) and provides collegial support for change. Our findings should be useful for designing similar supportive programs to facilitate change in the way we teach science for undergraduates. PMID:25452493

Photochromic cross-link polymer for color changing and sensing surface

NASA Astrophysics Data System (ADS)

Fu, Richard; Shi, Jianmin; Forsythe, Eric; Srour, Merric

2016-12-01

Photochromic cross-link polymers were developed using patented ultraviolet (UV) photoinitiator and commercial photochromic dyes. The photochromic dyes have been characterized by measuring absorbance before and after UV activation using UV-visible (Vis) spectrometry with varying activation intensities and wavelengths. Photochromic cross-link polymers were characterized by a dynamic xenon and UV light activation and fading system. The curing processes on cloth were established and tested to obtain effective photochromic responses. Both PulseForge photonic curing and PulseForge plus heat surface curing processes had much better photochromic responses (18% to 19%, 16% to 25%, respectively) than the xenon lamp treatment (8%). The newly developed photochromic cross-link polymer showed remarkable coloration contrasts and fast and comparable coloration and fading rates. Those intelligent, controlled color changing and sensing capabilities will be used on flexible and "drapeable" surfaces, which will incorporate ultra-low power sensors, sensor indicators, and identifiers.

Assessing the prediction accuracy of a cure model for censored survival data with long-term survivors: Application to breast cancer data.

PubMed

Asano, Junichi; Hirakawa, Akihiro

2017-01-01

The Cox proportional hazards cure model is a survival model incorporating a cure rate with the assumption that the population contains both uncured and cured individuals. It contains a logistic regression for the cure rate, and a Cox regression to estimate the hazard for uncured patients. A single predictive model for both the cure and hazard can be developed by using a cure model that simultaneously predicts the cure rate and hazards for uncured patients; however, model selection is a challenge because of the lack of a measure for quantifying the predictive accuracy of a cure model. Recently, we developed an area under the receiver operating characteristic curve (AUC) for determining the cure rate in a cure model (Asano et al., 2014), but the hazards measure for uncured patients was not resolved. In this article, we propose novel C-statistics that are weighted by the patients' cure status (i.e., cured, uncured, or censored cases) for the cure model. The operating characteristics of the proposed C-statistics and their confidence interval were examined by simulation analyses. We also illustrate methods for predictive model selection and for further interpretation of variables using the proposed AUCs and C-statistics via application to breast cancer data.

Composite Structure Repair. Addendum

DTIC Science & Technology

1984-08-01

room temperature curing systems . For permanent repairs no reduction in " serciveability with regard to the maximum design temperature and the design...pressure for ply compaction and conformation of bonding surfaces. In certain instances, ambient temperature cure systems may be sufficient. - Noisture...than those placed on radomes. Some of ,the resins used for the repairs were ambient curing systems which also required no additional pressure for

HIV-1 functional cure: will the dream come true?

PubMed

Liu, Chao; Ma, Xiancai; Liu, Bingfeng; Chen, Cancan; Zhang, Hui

2015-11-20

The reservoir of human immunodeficiency virus type 1 (HIV-1), a long-lived pool of latently infected cells harboring replication-competent viruses, is the major obstacle to curing acquired immune deficiency syndrome (AIDS). Although the combination antiretroviral therapy (cART) can successfully suppress HIV-1 viremia and significantly delay the progression of the disease, it cannot eliminate the viral reservoir and the patient must continue to take anti-viral medicines for life. Currently, the appearance of the 'Berlin patient', the 'Boston patients', and the 'Mississippi baby' have inspired many therapeutic strategies for HIV-1 aimed at curing efforts. However, the specific eradication of viral latency and the recovery and optimization of the HIV-1-specific immune surveillance are major challenges to achieving such a cure. Here, we summarize recent studies addressing the mechanisms underlying the viral latency and define two categories of viral reservoir: 'shallow' and 'deep'. We also present the current strategies and recent advances in the development of a functional cure for HIV-1, focusing on full/partial replacement of the immune system, 'shock and kill', and 'permanent silencing' approaches.

Cold-Curing Structural Epoxy Resins: Analysis of the Curing Reaction as a Function of Curing Time and Thickness

PubMed Central

Esposito Corcione, Carola; Freuli, Fabrizio; Frigione, Mariaenrica

2014-01-01

The curing reaction of a commercial cold-curing structural epoxy resin, specifically formulated for civil engineering applications, was analyzed by thermal analysis as a function of the curing time and the sample thickness. Original and remarkable results regarding the effects of curing time on the glass transition temperature and on the residual heat of reaction of the cold-cured epoxy were obtained. The influence of the sample thickness on the curing reaction of the cold-cured resin was also deeply investigated. A highly exothermal reaction, based on a self-activated frontal polymerization reaction, was supposed and verified trough a suitable temperature signal acquisition system, specifically realized for this measurement. This is one of the first studies carried out on the curing behavior of these peculiar cold-cured epoxy resins as a function of curing time and thickness. PMID:28788215

Cold-Curing Structural Epoxy Resins: Analysis of the Curing Reaction as a Function of Curing Time and Thickness.

PubMed

Corcione, Carola Esposito; Freuli, Fabrizio; Frigione, Mariaenrica

2014-09-22

The curing reaction of a commercial cold-curing structural epoxy resin, specifically formulated for civil engineering applications, was analyzed by thermal analysis as a function of the curing time and the sample thickness. Original and remarkable results regarding the effects of curing time on the glass transition temperature and on the residual heat of reaction of the cold-cured epoxy were obtained. The influence of the sample thickness on the curing reaction of the cold-cured resin was also deeply investigated. A highly exothermal reaction, based on a self-activated frontal polymerization reaction, was supposed and verified trough a suitable temperature signal acquisition system, specifically realized for this measurement. This is one of the first studies carried out on the curing behavior of these peculiar cold-cured epoxy resins as a function of curing time and thickness.

Epoxy matrix with triaromatic mesogenic unit in dielectric spectroscopy observation

NASA Astrophysics Data System (ADS)

Włodarska, Magdalena; Mossety-Leszczak, Beata; Bąk, Grzegorz W.; Kisiel, Maciej; Dłużniewski, Maciej; Okrasa, Lidia

2018-04-01

This paper describes the dielectric response of a selected liquid crystal epoxy monomer (plain and in curing systems) in a wide range of frequency and temperature. The dielectric spectroscopy, thanks to its sensitivity, is a very good tool for studying phase transitions, reaction progress, or material properties. This sensitivity is important in the case of liquid crystal epoxy resins, where properties of the final network depend on the choice of monomers, curing agents, curing conditions and post-curing treatment, or applying an external electric or magnetic field during the reaction. In most of the obtained cured products, the collected dielectric data show two relaxation processes. The α-process is related to a structural reorientation; it can usually be linked with the glass transition and the mechanical properties of the material. The β-process can be identified as a molecular motion process, probably associated with the carboxyl groups in the mesogen. A transient Maxwell-Wagner relaxation observed in one of the compositions after the initial curing is removed by post-curing treatment at elevated temperatures. Post-curing is therefore necessary for obtaining uniformly cured products in those cases. In the investigated systems, the choice of a curing agent can change the glass transition temperature by at least 70 °C. The obtained results are in a good agreement with an earlier study employing other techniques. Finally, we assess the influence of the direction of mesogen alignment on the dielectric properties of one selected system, where a global order was induced by applying an external magnetic field in the course of curing.

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

Characterization and optimization of an inkjet-printed smart textile UV-sensor cured with UV-LED light

NASA Astrophysics Data System (ADS)

Seipel, S.; Yu, J.; Periyasamy, A. P.; Viková, M.; Vik, M.; Nierstrasz, V. A.

2017-10-01

For the development of niche products like smart textiles and other functional high-end products, resource-saving production processes are needed. Niche products only require small batches, which makes their production with traditional textile production techniques time-consuming and costly. To achieve a profitable production, as well as to further foster innovation, flexible and integrated production techniques are a requirement. Both digital inkjet printing and UV-light curing contribute to a flexible, resource-efficient, energy-saving and therewith economic production of smart textiles. In this article, a smart textile UV-sensor is printed using a piezoelectric drop-on-demand printhead and cured with a UV-LED lamp. The UVcurable ink system is based on free radical polymerization and the integrated UVsensing material is a photochromic dye, Reversacol Ruby Red. The combination of two photoactive compounds, for which UV-light is both the curer and the activator, challenges two processes: polymer crosslinking of the resin and color performance of the photochromic dye. Differential scanning calorimetry (DSC) is used to characterize the curing efficiency of the prints. Color measurements are made to determine the influence of degree of polymer crosslinking on the developed color intensities, as well as coloration and decoloration rates of the photochromic prints. Optimized functionality of the textile UV-sensor is found using different belt speeds and lamp intensities during the curing process.

Facile fabrication of superhydrophobic films with fractal structures using epoxy resin microspheres

NASA Astrophysics Data System (ADS)

Quan, Yun-Yun; Zhang, Li-Zhi

2014-02-01

A simple method has been developed to fabricate superhydrophobic surfaces with fractal structures with epoxy resin microspheres (ERMs). The ERMs is produced by phase separation in an epoxy-amine curing system with a silica sol (SS) dispersant. The transparent epoxy solution becomes cloudy and turns into epoxy suspension (ES) in this process. The fractal structure (two tier structure) generated by synthetic epoxy resin microspheres (ERMs) and deposited nanoincrutations on the surfaces of these ERMs, which have been observed by scanning electron microscope (SEM). The curing time of ES is an important condition to obtain films with good comprehensive performances. Superhydrophobic films can be prepared by adding extra SS into ES with a curing time longer than 5 h. The optimal curing time is 10 h to fabricate a film with good mechanical stability and high superhydrophobicity. In addition, a surface with anti-wetting property of impacting microdroplets can be fabricated by prolonging the curing time of ES to 24 h. The gradually decreased hydrophilic groups resulted from a longer curing time enable the surface to have smaller surface adhesions to water droplets, which is the main reason to keep its superhydrophobicity under impacting conditions. The coated surface is highly hydrophobic and the impacting water droplets are bounced off from the surface.

Cure Cycle Optimization of Rapidly Cured Out-Of-Autoclave Composites.

PubMed

Dong, Anqi; Zhao, Yan; Zhao, Xinqing; Yu, Qiyong

2018-03-13

Out-of-autoclave prepreg typically needs a long cure cycle to guarantee good properties as the result of low processing pressure applied. It is essential to reduce the manufacturing time, achieve real cost reduction, and take full advantage of out-of-autoclave process. The focus of this paper is to reduce the cure cycle time and production cost while maintaining high laminate quality. A rapidly cured out-of-autoclave resin and relative prepreg were independently developed. To determine a suitable rapid cure procedure for the developed prepreg, the effect of heating rate, initial cure temperature, dwelling time, and post-cure time on the final laminate quality were evaluated and the factors were then optimized. As a result, a rapid cure procedure was determined. The results showed that the resin infiltration could be completed at the end of the initial cure stage and no obvious void could be seen in the laminate at this time. The laminate could achieve good internal quality using the optimized cure procedure. The mechanical test results showed that the laminates had a fiber volume fraction of 59-60% with a final glass transition temperature of 205 °C and excellent mechanical strength especially the flexural properties.

Cure Cycle Optimization of Rapidly Cured Out-Of-Autoclave Composites

PubMed Central

Dong, Anqi; Zhao, Yan; Zhao, Xinqing; Yu, Qiyong

2018-01-01

Out-of-autoclave prepreg typically needs a long cure cycle to guarantee good properties as the result of low processing pressure applied. It is essential to reduce the manufacturing time, achieve real cost reduction, and take full advantage of out-of-autoclave process. The focus of this paper is to reduce the cure cycle time and production cost while maintaining high laminate quality. A rapidly cured out-of-autoclave resin and relative prepreg were independently developed. To determine a suitable rapid cure procedure for the developed prepreg, the effect of heating rate, initial cure temperature, dwelling time, and post-cure time on the final laminate quality were evaluated and the factors were then optimized. As a result, a rapid cure procedure was determined. The results showed that the resin infiltration could be completed at the end of the initial cure stage and no obvious void could be seen in the laminate at this time. The laminate could achieve good internal quality using the optimized cure procedure. The mechanical test results showed that the laminates had a fiber volume fraction of 59–60% with a final glass transition temperature of 205 °C and excellent mechanical strength especially the flexural properties. PMID:29534048

Isothermal transitions of a thermosetting system

NASA Technical Reports Server (NTRS)

Gillham, J. K.; Benci, J. A.; Noshay, A.

1974-01-01

A study of the curing reactions of a cycloaliphatic epoxy resin/anhydride system by torsional braid analysis showed the existence of two critical isothermal temperatures - namely, the maximum glass transition temperature of the thermoset system and the glass transition temperature of the material at its gel point. Two rheologically active kinetic transitions occur during isothermal cure which correspond to gelation and vitrification. Three types of isothermal behavior occur. Methods for determining the time to gel and the time to vitrify, and also the two above-mentioned critical isothermal temperatures, have been developed. The time to gel obeyed the Arrhenius relationship, whereas the time to vitrify passed through a minimum. Application of these results to thermosetting systems in general is discussed in terms of the influence of molecular structure on the values of the critical isothermal temperatures.

Each to Their Own CURE: Faculty Who Teach Course-Based Undergraduate Research Experiences Report Why You Too Should Teach a CURE†

PubMed Central

Shortlidge, Erin E.; Bangera, Gita; Brownell, Sara E.

2017-01-01

Course-based undergraduate research experiences (CUREs) meet national recommendations for integrating research experiences into life science curricula. As such, CUREs have grown in popularity and many research studies have focused on student outcomes from CUREs. Institutional change literature highlights that understanding faculty is also key to new pedagogies succeeding. To begin to understand faculty perspectives on CUREs, we conducted semi-structured interviews with 61 faculty who teach CUREs regarding why they teach CUREs, what the outcomes are, and how they would discuss a CURE with a colleague. Using grounded theory, participant responses were coded and categorized as tangible or intangible, related to both student and faculty-centered themes. We found that intangible themes were prevalent, and that there were significant differences in the emphasis on tangible themes for faculty who have developed their own independent CUREs when compared with faculty who implement pre-developed, national CUREs. We focus our results on the similarities and differences among the perspectives of faculty who teach these two different CURE types and explore trends among all participants. The results of this work highlight the need for considering a multi-dimensional framework to understand, promote, and successfully implement CUREs. PMID:28656071

3. DETAIL OF RACKS AND TEMPERATURE/HUMIDITY CONTROL SYSTEM IN CURING ...

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

3. DETAIL OF RACKS AND TEMPERATURE/HUMIDITY CONTROL SYSTEM IN CURING ROOM ON LEVEL 6; LOOKING SOUTHEAST; ENVIRONMENT INSIDE THE CURING ROOM WAS CONTROLLED BY NIAGARA MODEL 87007 SPRAY COOLER AND BUFFALO FORGE CENTRIFUGAL FAN IN BACKGROUND - Rath Packing Company, Cooler Building, Sycamore Street between Elm & Eighteenth Streets, Waterloo, Black Hawk County, IA

Investigation into improved pavement curing materials and techniques : part 1 (phases I and II).

DOT National Transportation Integrated Search

2002-04-01

Concrete curing is closely related to cement hydration, microstructure development, and concrete : performance. Application of a liquid membrane-forming curing compound is among the most widely : used curing methods for concrete pavements and bridge ...

Current views on HIV-1 latency, persistence, and cure.

PubMed

Melkova, Zora; Shankaran, Prakash; Madlenakova, Michaela; Bodor, Josef

2017-01-01

HIV-1 infection cannot be cured as it persists in latently infected cells that are targeted neither by the immune system nor by available therapeutic approaches. Consequently, a lifelong therapy suppressing only the actively replicating virus is necessary. The latent reservoir has been defined and characterized in various experimental models and in human patients, allowing research and development of approaches targeting individual steps critical for HIV-1 latency establishment, maintenance, and reactivation. However, additional mechanisms and processes driving the remaining low-level HIV-1 replication in the presence of the suppressive therapy still remain to be identified and targeted. Current approaches toward HIV-1 cure involve namely attempts to reactivate and purge HIV latently infected cells (so-called "shock and kill" strategy), as well as approaches involving gene therapy and/or gene editing and stem cell transplantation aiming at generation of cells resistant to HIV-1. This review summarizes current views and concepts underlying different approaches aiming at functional or sterilizing cure of HIV-1 infection.

In Vivo Models of Human Immunodeficiency Virus Persistence and Cure Strategies

PubMed Central

Mavigner, Maud; Silvestri, Guido; Garcia, J. Victor

2017-01-01

Abstract Current HIV therapy is not curative regardless of how soon after infection it is initiated or how long it is administered, and therapy interruption almost invariably results in robust viral rebound. Human immunodeficiency virus persistence is therefore the major obstacle to a cure for AIDS. The testing and implementation of novel yet unproven approaches to HIV eradication that could compromise the health status of HIV-infected individuals might not be ethically warranted. Therefore, adequate in vitro and in vivo evidence of efficacy is needed to facilitate the clinical implementation of promising strategies for an HIV cure. Animal models of HIV infection have a strong and well-documented history of bridging the gap between laboratory discoveries and eventual clinical implementation. More recently, animal models have been developed and implemented for the in vivo evaluation of novel HIV cure strategies. In this article, we review the recent progress in this rapidly moving area of research, focusing on the two most promising model systems: humanized mice and nonhuman primates. PMID:28520967

Cure effects on microcracking in IM7 fiber/Matrimid 5292{reg_sign} BMI composites

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

Wilenski, M.S.; Shin, E.; Morgan, R.J.

1995-12-31

Initial results from a study of the microcracking behavior of the Matrimid 5292{reg_sign} BMI/IM7 carbon fiber system are presented. Studies were performed to determine the composite`s Stress Free Temperature (SFT) which is seen to control the presence and extent of microcracking. The SFT was determined using asymmetric laminates [0{sub 2}/90{sub 2}]. Varied post-cure cycles were utilized and it was found that until complete cure is obtained, the SFT is a function of the highest temperature experienced by the laminate, with little effect of previous thermal history. The reactions necessary to fully cure this system are not active at temperatures belowmore » 250 C, ruling out the possibility of obtaining a fully cured composite with a low SFT through extended post-cures at lower temperatures.« less

Curing kinetics and thermomechanical properties of latent epoxy/carbon fiber composites

NASA Astrophysics Data System (ADS)

Dalle Vacche, S.; Michaud, V.; Demierre, M.; Bourban, P.-E.; Månson, J.-A. E.

2016-07-01

In this work, resins based on diglycidyl ether of bisphenol A (DGEBA) epoxy and a latent hardener, dicyandiamide (DICY), as well as carbon fiber (CF) composites based on them, were prepared with three commercial accelerators: a methylene bis (phenyl dimethyl urea), a cycloaliphatic substituted urea, and a modified polyamine. The curing kinetics of the three DGEBA/DICY/accelerator systems were investigated by chemorheology and differential scanning calorimetry (DSC), in isothermal and over temperature change conditions. Differences in the reaction onset temperature, and in the glass transition temperature (Tg) were highlighted. For curing of thick resin samples, a slow curing cycle at the lowest possible temperature was used, followed by high temperature (160 - 180 °C) post-curing. Indeed, fast curing at higher temperatures caused the formation of hot spots and led to local burning of the samples. The obtained thermomechanical properties, assessed by ultimate tensile testing and dynamic mechanical analysis (DMA) in single cantilever configuration, were all in the expected range for epoxy resins, with tensile moduli close to 3 GPa and Tg > 140 °C. The longterm stability of these resins at room temperature was verified by DSC. Composite samples were prepared by hand lay-up by manually impregnating four layers of 5-harness satin CF textile, and curing in vacuum bag. Impregnation quality and void content were assessed by optical microscopy. The flexural properties of the post-cured composites were assessed by three-point bending test at room temperature and showed no relevant differences, all composites having bending moduli of 45 - 50 GPa. Finally, composites cured with a faster high temperature curing cycle (20 min at 140 °C) were prepared with the DGEBA/DICY/ methylene bis (phenyl dimethyl urea) system, obtaining similar properties as with the slower curing cycle, showing that the prepreg system allowed more flexibility in terms of curing cycle than the bulk resin samples.

Comparing the shear bond strength of direct and indirect composite inlays in relation to different surface conditioning and curing techniques

PubMed Central

Zorba, Yahya Orcun; Ilday, Nurcan Ozakar; Bayındır, Yusuf Ziya; Demirbuga, Sezer

2013-01-01

Objective: The aim of this study was to test the null hypothesis that different surface conditioning (etch and rinse and self-etch) and curing techniques (light cure/dual cure) had no effect on the shear bond strength of direct and indirect composite inlays. Materials and Methods: A total of 112 extracted human molar teeth were horizontally sectioned and randomly divided into two groups according to restoration technique (direct and indirect restorations). Each group was further subdivided into seven subgroups (n = 8) according to bonding agent (etch and rinse adhesives Scotchbond multi-purpose plus, All-Bond 3, Adper Single Bond and Prime Bond NT; and self-etch adhesives Clearfil Liner Bond, Futurabond DC and G bond). Indirect composites were cemented to dentin surfaces using dual-curing luting cement. Shear bond strength of specimens was tested using a Universal Testing Machine. Two samples from each subgroup were evaluated under Scanning electron microscopy to see the failing modes. Data was analyzed using independent sample t-tests and Tukey's tests. Results: Surface conditioning and curing of bonding agents were all found to have significant effects on shear bond strength (P < 0.05) of both direct and indirect composite inlays. With direct restoration, etch and rinse systems and dual-cured bonding agents yielded higher bond strengths than indirect restoration, self-etch systems and light-cured bonding agents. Conclusions: The results of the present study indicated that direct restoration to be a more reliable method than indirect restoration. Although etch and rinse bonding systems showed higher shear bond strength to dentin than self-etch systems, both systems can be safely used for the adhesion of direct as well as indirect restorations. PMID:24932118

Comparing the shear bond strength of direct and indirect composite inlays in relation to different surface conditioning and curing techniques.

PubMed

Zorba, Yahya Orcun; Ilday, Nurcan Ozakar; Bayındır, Yusuf Ziya; Demirbuga, Sezer

2013-10-01

The aim of this study was to test the null hypothesis that different surface conditioning (etch and rinse and self-etch) and curing techniques (light cure/dual cure) had no effect on the shear bond strength of direct and indirect composite inlays. A total of 112 extracted human molar teeth were horizontally sectioned and randomly divided into two groups according to restoration technique (direct and indirect restorations). Each group was further subdivided into seven subgroups (n = 8) according to bonding agent (etch and rinse adhesives Scotchbond multi-purpose plus, All-Bond 3, Adper Single Bond and Prime Bond NT; and self-etch adhesives Clearfil Liner Bond, Futurabond DC and G bond). Indirect composites were cemented to dentin surfaces using dual-curing luting cement. Shear bond strength of specimens was tested using a Universal Testing Machine. Two samples from each subgroup were evaluated under Scanning electron microscopy to see the failing modes. Data was analyzed using independent sample t-tests and Tukey's tests. Surface conditioning and curing of bonding agents were all found to have significant effects on shear bond strength (P < 0.05) of both direct and indirect composite inlays. With direct restoration, etch and rinse systems and dual-cured bonding agents yielded higher bond strengths than indirect restoration, self-etch systems and light-cured bonding agents. The results of the present study indicated that direct restoration to be a more reliable method than indirect restoration. Although etch and rinse bonding systems showed higher shear bond strength to dentin than self-etch systems, both systems can be safely used for the adhesion of direct as well as indirect restorations.

Chemoviscosity modeling for thermosetting resins - I

NASA Technical Reports Server (NTRS)

Hou, T. H.

1984-01-01

A new analytical model for chemoviscosity variation during cure of thermosetting resins was developed. This model is derived by modifying the widely used WLF (Williams-Landel-Ferry) Theory in polymer rheology. Major assumptions involved are that the rate of reaction is diffusion controlled and is linearly inversely proportional to the viscosity of the medium over the entire cure cycle. The resultant first order nonlinear differential equation is solved numerically, and the model predictions compare favorably with experimental data of EPON 828/Agent U obtained on a Rheometrics System 4 Rheometer. The model describes chemoviscosity up to a range of six orders of magnitude under isothermal curing conditions. The extremely non-linear chemoviscosity profile for a dynamic heating cure cycle is predicted as well. The model is also shown to predict changes of glass transition temperature for the thermosetting resin during cure. The physical significance of this prediction is unclear at the present time, however, and further research is required. From the chemoviscosity simulation point of view, the technique of establishing an analytical model as described here is easily applied to any thermosetting resin. The model thus obtained is used in real-time process controls for fabricating composite materials.

Compact Embedded Wireless Sensor-Based Monitoring of Concrete Curing.

PubMed

Cabezas, Joaquín; Sánchez-Rodríguez, Trinidad; Gómez-Galán, Juan Antonio; Cifuentes, Héctor; González Carvajal, Ramón

2018-03-15

This work presents the design, construction and testing of a new embedded sensor system for monitoring concrete curing. A specific mote has been implemented to withstand the aggressive environment without affecting the measured variables. The system also includes a real-time monitoring application operating from a remote computer placed in a central location. The testing was done in two phases: the first in the laboratory, to validate the functional requirements of the developed devices; and the second on civil works to evaluate the functional features of the devices, such as range, robustness and flexibility. The devices were successfully implemented resulting in a low cost, highly reliable, compact and non-destructive solution.

Compact Embedded Wireless Sensor-Based Monitoring of Concrete Curing

PubMed Central

Cabezas, Joaquín; Sánchez-Rodríguez, Trinidad; González Carvajal, Ramón

2018-01-01

This work presents the design, construction and testing of a new embedded sensor system for monitoring concrete curing. A specific mote has been implemented to withstand the aggressive environment without affecting the measured variables. The system also includes a real-time monitoring application operating from a remote computer placed in a central location. The testing was done in two phases: the first in the laboratory, to validate the functional requirements of the developed devices; and the second on civil works to evaluate the functional features of the devices, such as range, robustness and flexibility. The devices were successfully implemented resulting in a low cost, highly reliable, compact and non-destructive solution. PMID:29543765

The Effect of Molecular Weight on the Composite Properties of Cured Phenylethynyl Terminated Imide Oligomers

NASA Technical Reports Server (NTRS)

Smith, J. G., Jr.; Connell, J. W.; Hergenrother, P. M.

1997-01-01

As part of a program to develop high temperature/high performance structural resins for aeronautical applications, imide oligomers containing terminal phenylethynyl groups with calculated number average molecular weights of 1250, 2500 and 5000 g/mol were prepared, characterized, and evaluated as adhesives and composite matrix resins. The goal of this work was to develop resin systems that are processable using conventional processing equipment into void free composites that exhibit high mechanical properties with long term high temperature durability, and are not affected by exposure to common aircraft fluids. The imide oligomers containing terminal phenylethynyl groups were fabricated into titanium adhesive specimens and IM-7 carbon fiber laminates under 0.1 - 1.4 MPa for 1 hr at 350-371 C. The lower molecular weight oligomers exhibited higher cured Tg, better processability, and better retention of mechanical properties at elevated temperature without significantly sacrificing toughness or damage tolerance than the higher molecular weight oligomer. The neat resin, adhesive and composite properties of the cured polymers will be presented.

Development and Evaluation of the Tigriopus Course-Based Undergraduate Research Experience: Impacts on Students’ Content Knowledge, Attitudes, and Motivation in a Majors Introductory Biology Course

PubMed Central

Olimpo, Jeffrey T.; Fisher, Ginger R.; DeChenne-Peters, Sue Ellen

2016-01-01

Within the past decade, course-based undergraduate research experiences (CUREs) have emerged as a viable mechanism to enhance novices’ development of scientific reasoning and process skills in the science, technology, engineering, and mathematics disciplines. Recent evidence within the bioeducation literature suggests that student engagement in such experiences not only increases their appreciation for and interest in scientific research but also enhances their ability to “think like a scientist.” Despite these critical outcomes, few studies have objectively explored CURE versus non-CURE students’ development of content knowledge, attitudes, and motivation in the discipline, particularly among nonvolunteer samples. To address these concerns, we adopted a mixed-methods approach to evaluate the aforementioned outcomes following implementation of a novel CURE in an introductory cell/molecular biology course. Results indicate that CURE participants exhibited more expert-like outcomes on these constructs relative to their non-CURE counterparts, including in those areas related to self-efficacy, self-determination, and problem-solving strategies. Furthermore, analysis of end-of-term survey data suggests that select features of the CURE, such as increased student autonomy and collaboration, mediate student learning and enjoyment. Collectively, this research provides novel insights into the benefits achieved as a result of CURE participation and can be used to guide future development and evaluation of authentic research opportunities. PMID:27909022

On processing development for fabrication of fiber reinforced composite, part 2

NASA Technical Reports Server (NTRS)

Hou, Tan-Hung; Hou, Gene J. W.; Sheen, Jeen S.

1989-01-01

Fiber-reinforced composite laminates are used in many aerospace and automobile applications. The magnitudes and durations of the cure temperature and the cure pressure applied during the curing process have significant consequences for the performance of the finished product. The objective of this study is to exploit the potential of applying the optimization technique to the cure cycle design. Using the compression molding of a filled polyester sheet molding compound (SMC) as an example, a unified Computer Aided Design (CAD) methodology, consisting of three uncoupled modules, (i.e., optimization, analysis and sensitivity calculations), is developed to systematically generate optimal cure cycle designs. Various optimization formulations for the cure cycle design are investigated. The uniformities in the distributions of the temperature and the degree with those resulting from conventional isothermal processing conditions with pre-warmed platens. Recommendations with regards to further research in the computerization of the cure cycle design are also addressed.

Fiber-optic sensor design for chemical process and environmental monitoring

NASA Astrophysics Data System (ADS)

Mahendran, R. S.; Wang, L.; Machavaram, V. R.; Pandita, S. D.; Chen, R.; Kukureka, S. N.; Fernando, G. F.

2009-10-01

"Curing" is a term that is used to describe the cross-linking reactions in a thermosetting resin system. Advanced fiber-reinforced composites are being used increasingly in a number of industrial sectors including aerospace, marine, sport, automotive and civil engineering. There is a general realization that the processing conditions that are used to manufacture the composite can have a major influence on its hot-wet mechanical properties. This paper is concerned with the design and demonstration of a number of sensor designs for in situ monitoring of the cross-linking reactions of a commercially available thermosetting resin system. Simple fixtures were constructed to enable a pair of cleaved optical fibers with a defined gap between the end-faces to be held in position. The resin system was introduced into this gap and the cure kinetics were followed by transmission infrared spectroscopy. A semi-empirical model was used to describe the cure process using the data obtained at different cure temperatures. The same sensor system was used to detect the ingress of moisture into the cured resin system.

Development of processing diagrams for polymeric die attach adhesives

NASA Astrophysics Data System (ADS)

Hsiung, Jen-Chou

With a processing diagram, one can reduce the effort required to customize curing process conditions for polymeric die attach adhesives. Polymeric die attach adhesives are often cured per the manufacturer's recommendations during initial screening evaluations. In most cases, the recommended cure schedules have to be modified so as to fit differences in process equipment. Unfortunately, the modified cure schedule is usually determined by a trial-and-error method. An aim of our experiments is to understand the curing process of a wide range of polymeric die attach adhesives (conventional, fast, and snap cure adhesives) and to construct a processing diagram, i.e., "Bondability Diagram", so as to define the processing window. Such diagrams should be helpful in determining both the time and cure temperature required to produce high quality bonds. The bondability diagram can be constructed based on fundamental understandings of the phenomena involved in the curing process using a wide variety of tools. Differential Scanning Calorimetry (DSC) is utilized to study the cure kinetics and the extent of reaction. Dynamic Mechanical Analysis (DMA) is used to determine gelation times and melt viscosity under a shear mode. A modified Rheovibron is employed to perform cure characterizations under a tensile mode so that cure stresses could be determined. Thermogravimetric Analysis (TGA) is used to evaluate the outgassing phenomena. Optical Microscopy (OM) is used to detect voids. Results indicate that the cure behaviors of conventional, fast, and snap cure adhesives are different in several respects. The combination of DSC, DMA, TGA, OM, and lap shear test leads to a frame work of developing the bondability diagram concept. The bondability diagram concept provides a foundation for an understanding of the recommended cure schedule and allows one to design their own cure schedule.

Monitoring cure of composite resins using frequency dependent electromagnetic sensing techniques

NASA Technical Reports Server (NTRS)

Kranbuehl, D. E.; Hoff, M. S.; Loos, A. C.; Freeman, W. T., Jr.; Eichinger, D. A.

1988-01-01

A nondestructive in situ measurement technique has been developed for monitoring and measuring the cure processing properties of composite resins. Frequency dependent electromagnetic sensors (FDEMS) were used to directly measure resin viscosity during cure. The effects of the cure cycle and resin aging on the viscosity during cure were investigated using the sensor. Viscosity measurements obtained using the sensor are compared with the viscosities calculated by the Loos-Springer cure process model. Good overall agreement was obtained except for the aged resin samples.

Microgel Modified UV-Cured Methacrylic-Silica Hybrid: Synthesis and Characterization

PubMed Central

Corcione, Carola Esposito; Striani, Raffaella; Frigione, Mariaenrica

2013-01-01

An innovative photopolymerizable microgel modified UV-cured acrylic-silica hybrid formulation was developed and characterized for possible use as protective coating for different substrates. A deep investigation, aiming at providing a strong scientific basis for the production of organic-inorganic (O-I) hybrids exhibiting phase co-continuity, was firstly carried out. The O-I hybrid first proposed in this study was obtained from organic precursors with a high siloxane content, which are mixed with tetraethoxysilane (TEOS) in such a way to produce co-continuous silica nanodomains dispersed within the crosslinked organic phase, as a result of the sol-gel process. The first part of the research deals with the selection and optimization of suitable systems through appropriate chemical modifications, in order to ensure that curing reactions can be carried out at room temperature and in the presence of UV radiation. Firstly, the silica domains are formed, followed by crosslinking reactions of the acrylic groups in the oligomer via a free radical polymerization. The crosslinking reaction was controlled with the use of a suitable photoinitiator. Most of the experimental work was devoted to understanding the morphology of the hybrid system, both in uncured and cured states, and to assess its final thermal and optical properties, using different experiential techniques. PMID:28788307

Development of phosphorylated adhesives

NASA Technical Reports Server (NTRS)

Bilow, N.; Giants, T. W.; Jenkins, R. K.; Campbell, P. L.

1983-01-01

The synthesis of epoxy prepolymers containing phosphorus was carried out in such a manner as to provide adhesives containing at least 5 percent of this element. The purpose of this was to impart fire retardant properties to the adhesive. The two epoxy derivatives, bis(4-glycidyl-oxyphenyl)phenylphosphine oxide and bis(4-glycidyl-2-methoxyphenyl)phenylphosphonate, and a curing agent, bis(3-aminophenyl)methylphosphine oxide, were used in conjunction with one another and along with conventional epoxy resins and curing agents to bond Tedlar and Polyphenylethersulfone films to Kerimid-glass syntactic foam-filled honeycomb structures. Elevated temperatures are required to cure the epoxy resins with the phosphorus-contaning diamine; however, when Tedlar is being bonded, lower curing temperatures must be used to avoid shrinkage and the concomitant formation of surface defects. Thus, the phosphorus-containing aromatic amine curing agent cannot be used alone, although it is possible to use it in conjunction with an aliphatic amine which would allow lower cure temperatures to be used. The experimental epoxy resins have not provided adhesive bonds quite as strong as those provided by Epon 828 when compared in peel tests, but the differences are not very significant. It should be noted, if optimum properties are to be realized. In any case the fire retardant characteristics of the neat resin systems obtained are quite pronounced, since in most cases the self-extinguishing properties are evident almost instantly when specimens are removed from a flame.

Biomarkers for Uranium Risk Assessment for the Development of the CURE (Concerted Uranium Research in Europe) Molecular Epidemiological Protocol.

PubMed

Guéguen, Yann; Roy, Laurence; Hornhardt, Sabine; Badie, Christophe; Hall, Janet; Baatout, Sarah; Pernot, Eileen; Tomasek, Ladislav; Laurent, Olivier; Ebrahimian, Teni; Ibanez, Chrystelle; Grison, Stephane; Kabacik, Sylwia; Laurier, Dominique; Gomolka, Maria

2017-01-01

Despite substantial experimental and epidemiological research, there is limited knowledge of the uranium-induce health effects after chronic low-dose exposures in humans. Biological markers can objectively characterize pathological processes or environmental responses to uranium and confounding agents. The integration of such biological markers into a molecular epidemiological study would be a useful approach to improve and refine estimations of uranium-induced health risks. To initiate such a study, Concerted Uranium Research in Europe (CURE) was established, and involves biologists, epidemiologists and dosimetrists. The aims of the biological work package of CURE were: 1. To identify biomarkers and biological specimens relevant to uranium exposure; 2. To define standard operating procedures (SOPs); and 3. To set up a common protocol (logistic, questionnaire, ethical aspects) to perform a large-scale molecular epidemiologic study in uranium-exposed cohorts. An intensive literature review was performed and led to the identification of biomarkers related to: 1. retention organs (lungs, kidneys and bone); 2. other systems/organs with suspected effects (cardiovascular system, central nervous system and lympho-hematopoietic system); 3. target molecules (DNA damage, genomic instability); and 4. high-throughput methods for the identification of new biomarkers. To obtain high-quality biological materials, SOPs were established for the sampling and storage of different biospecimens. A questionnaire was developed to assess potential confounding factors. The proposed strategy can be adapted to other internal exposures and should improve the characterization of the biological and health effects that are relevant for risk assessment.

Color Developing Capacity of Plasma-treated Water as a Source of Nitrite for Meat Curing.

PubMed

Jung, Samooel; Kim, Hyun Joo; Park, Sanghoo; Yong, Hae In; Choe, Jun Ho; Jeon, Hee-Joon; Choe, Wonho; Jo, Cheorun

2015-01-01

The interaction of plasma with liquid generates nitrogen species including nitrite (NO(-) 2). Therefore, the color developing capacity of plasma-treated water (PTW) as a nitrite source for meat curing was investigated in this study. PTW, which is generated by surface dielectric barrier discharge in air, and the increase of plasma treatment time resulted in increase of nitrite concentration in PTW. The PTW used in this study contains 46 ppm nitrite after plasma treatment for 30 min. To evaluate the effect of PTW on the cured meat color, meat batters were prepared under three different conditions (control, non-cured meat batter; PTW, meat batter cured with PTW; Sodium nitrite, meat batter cured with sodium nitrite). The meat batters were vacuum-packaged and cooked in a water-bath at 80℃ for 30 min. The typical color of cured meat developed in cooked meat batter treated with sodium nitrite or PTW. The lightness (L*) and yellowness (b*) values were similar in all conditions, whereas, the redness (a*) values of cooked meat batter with PTW and sodium nitrite (p<0.05) were significantly higher than the control. These data indicate that PTW can be used as a nitrite source in the curing process of meat without addition of other nitrite sources.

Color Developing Capacity of Plasma-treated Water as a Source of Nitrite for Meat Curing

PubMed Central

Jung, Samooel; Kim, Hyun Joo; Park, Sanghoo; Choe, Jun Ho; Jeon, Hee-Joon; Choe, Wonho

2015-01-01

The interaction of plasma with liquid generates nitrogen species including nitrite (NO−2). Therefore, the color developing capacity of plasma-treated water (PTW) as a nitrite source for meat curing was investigated in this study. PTW, which is generated by surface dielectric barrier discharge in air, and the increase of plasma treatment time resulted in increase of nitrite concentration in PTW. The PTW used in this study contains 46 ppm nitrite after plasma treatment for 30 min. To evaluate the effect of PTW on the cured meat color, meat batters were prepared under three different conditions (control, non-cured meat batter; PTW, meat batter cured with PTW; Sodium nitrite, meat batter cured with sodium nitrite). The meat batters were vacuum-packaged and cooked in a water-bath at 80℃ for 30 min. The typical color of cured meat developed in cooked meat batter treated with sodium nitrite or PTW. The lightness (L*) and yellowness (b*) values were similar in all conditions, whereas, the redness (a*) values of cooked meat batter with PTW and sodium nitrite (p<0.05) were significantly higher than the control. These data indicate that PTW can be used as a nitrite source in the curing process of meat without addition of other nitrite sources. PMID:26761900

Traditional, complementary, and alternative medical cures for HIV: rationale and implications for HIV cure research.

PubMed

Pan, Xin; Zhang, Alice; Henderson, Gail E; Rennie, Stuart; Liu, Chuncheng; Cai, Weiping; Wu, Feng; Tucker, Joseph D

2017-12-13

Traditional, complementary, and alternative medicine (TCAM) has been used by some people living with HIV (PLHIV) in an attempt to cure HIV. This article reviews the main factors influencing their decision to choose TCAM to cure HIV and discusses implications for HIV cure research. Those who decide to pursue traditional, complementary, and alternative medical cures may be influenced by the health system, cultural, and social dynamics, and their own individual beliefs and preferences. These same factors may impact participation in HIV cure research. People who search for traditional, complementary, and alternative medical cures may face special challenges as they are recruited, consented, and retained within HIV cure research studies. To address these potential challenges, we have suggested solutions focusing on culturally tailored communication and education, formative social science research, and community partnerships with key stakeholders. The social conditions that have promoted traditional, complementary and alternative medical cures will likely impact how PLHIV participate and experience HIV remission trials. Despite the potential challenges, it will be crucial to involve those who have previously sought out traditional cures for HIV in HIV cure research.

Curing of polymer thermosets via click reactions and on demand processes

NASA Astrophysics Data System (ADS)

Brei, Mark Richard

In the first project, an azide functional resin and tetra propargyl aromatic diamines were fabricated for use as a composite matrix. These systems take already established epoxy/amine matrices and functionalize them with click moieties. This allows lower temperatures to be used in the production of a thermoset part. These new systems yield many better mechanical properties than their epoxy/amine derivatives, but their Tgs are low in comparison. The second project investigates the characterization of a linear system based off of the above azide functional resin and a difunctional alkyne. Through selectively choosing catalyst, the linear system can show regioselectivity to either a 1,4-disubstituted triazole, or a 1,5-disubstituted triazole. Without the addition of catalyst, the system produces both triazoles in almost an equal ratio. The differently catalyzed systems were cured and then analyzed by 1H and 13C NMR to better understand the structure of the material. The third project builds off of the utility of the aforementioned azide/alkyne system and introduces an on-demand aspect to the curing of the thermoset. With the inclusion of copper(II) within the azide/alkyne system, UV light is able to catalyze said reaction and cure the material. It has been shown that the copper(II) loading levels can be extremely small, which helps in reducing the copper's effect on mechanical properties The fourth project takes a look at polysulfide-based sealants. These sealants are normally cured via an oxidative reaction. This project took thiol-terminated polysulfides and fabricated alkene-terminated polysulfides for use as a thiol-ene cured material. By changing the mechanism for cure, the polysulfide can be cured via UV light with the use of a photoinitiator within the thiol/alkene polysulfide matrix. The final chapter will focus on a characterization technique, MALDI-TOF, which was used to help characterize the above materials as well as many others. By using MALDI-TOF, the researcher is able to elicit the molecular weight of the repeat unit and end group, which allows the determination of the polymer's structure. This technique can also determine the Mn and M w, as well as the PDI for each given polymer.

Animal Models for HIV Cure Research.

PubMed

Policicchio, Benjamin B; Pandrea, Ivona; Apetrei, Cristian

2016-01-01

The HIV-1/AIDS pandemic continues to spread unabated worldwide, and no vaccine exists within our grasp. Effective antiretroviral therapy (ART) has been developed, but ART cannot clear the virus from the infected patient. A cure for HIV-1 is badly needed to stop both the spread of the virus in human populations and disease progression in infected individuals. A safe and effective cure strategy for human immunodeficiency virus (HIV) infection will require multiple tools, and appropriate animal models are tools that are central to cure research. An ideal animal model should recapitulate the essential aspects of HIV pathogenesis and associated immune responses, while permitting invasive studies, thus allowing a thorough evaluation of strategies aimed at reducing the size of the reservoir (functional cure) or eliminating the reservoir altogether (sterilizing cure). Since there is no perfect animal model for cure research, multiple models have been tailored and tested to address specific quintessential questions of virus persistence and eradication. The development of new non-human primate and mouse models, along with a certain interest in the feline model, has the potential to fuel cure research. In this review, we highlight the major animal models currently utilized for cure research and the contributions of each model to this goal.

Animal Models for HIV Cure Research

PubMed Central

Policicchio, Benjamin B.; Pandrea, Ivona; Apetrei, Cristian

2016-01-01

The HIV-1/AIDS pandemic continues to spread unabated worldwide, and no vaccine exists within our grasp. Effective antiretroviral therapy (ART) has been developed, but ART cannot clear the virus from the infected patient. A cure for HIV-1 is badly needed to stop both the spread of the virus in human populations and disease progression in infected individuals. A safe and effective cure strategy for human immunodeficiency virus (HIV) infection will require multiple tools, and appropriate animal models are tools that are central to cure research. An ideal animal model should recapitulate the essential aspects of HIV pathogenesis and associated immune responses, while permitting invasive studies, thus allowing a thorough evaluation of strategies aimed at reducing the size of the reservoir (functional cure) or eliminating the reservoir altogether (sterilizing cure). Since there is no perfect animal model for cure research, multiple models have been tailored and tested to address specific quintessential questions of virus persistence and eradication. The development of new non-human primate and mouse models, along with a certain interest in the feline model, has the potential to fuel cure research. In this review, we highlight the major animal models currently utilized for cure research and the contributions of each model to this goal. PMID:26858716

Methods for analysis of the occurrence of abscess in patients with pancreatitis.

PubMed

Roca-Antonio, J; Escudero, L E; Gener, J; Oller, B; Rodríguez, N; Muñoz, A

1997-01-01

Standard survival analysis methods are useful for data involving censored cases when cures do not generally occur. If the object is to study, for instance, the development of a complication in the progress of an infectious disease, some people may be cured before complications develop. In this article, we provide methods for the analysis of data when cures do occur. An example is a study of prognostic factors for pancreatic abscess in patients with pancreatitis, some of whom leave the risk set because the pancreatitis clears. We present methods for estimating the survival curves and comparing hazard function for two objectives: (1) the occurrence of an abscess, irrespective of whether the patients are cured or not, and (2) the occurrence of an abscess for patients who, at that stage, have not been cured. We illustrate the applications of the methods using a sample of 50 patients with severe pancreatitis. To study the occurrence of an abscess, regardless of whether the patients are cured or not, we show that the appropriate strategy is to assign to the cured patients an infinite time to the appearance of an abscess. If the cured were considered censored at the moment the pancreatitis cleared, this would result in an overestimation of the hazard of presenting an abscess. On the other hand, if the objective is to compare the occurrence of abscess according to an exposure for patients who have not been cured, one needs to censor the cured patients at the time they are cured. For the analysis of survival data in the context of infectious diseases when cure is possible, it is important to use a censoring strategy that is pertinent to the specific aims of the study. Considering cures as censored at the time of cure is not always appropriate.

Fast Curing of Composite Wood Products

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

Dr. Arthur J. Ragauskas

2006-04-26

The overall objective of this program is to develop low temperature curing technologies for UF and PF resins. This will be accomplished by: • Identifying the rate limiting UF and PF curing reactions for current market resins; • Developing new catalysts to accelerate curing reactions at reduced press temperatures and times. In summary, these new curing technologies will improve the strength properties of the composite wood products and minimize the detrimental effects of wood extractives on the final product while significantly reducing energy costs for wood composites. This study is related to the accelerated curing of resins for wood compositesmore » such as medium density fiberboard (MDF), particle board (PB) and oriented strandboard (OSB). The latter is frequently manufactured with a phenol-formaldehyde resin whereas ureaformaldehyde (UF) resins are usually used in for the former two grades of composite wood products. One of the reasons that hinder wider use of these resins in the manufacturing of wood composites is the slow curing speed as well as inferior bondability of UF resin. The fast curing of UP and PF resins has been identified as an attractive process development that would allow wood to be bonded at higher moisture contents and at lower press temperatures that currently employed. Several differing additives have been developed to enhance cure rates of PF resins including the use of organic esters, lactones and organic carbonates. A model compound study by Conner, Lorenz and Hirth (2002) employed 2- and 4-hydroxymethylphenol with organic esters to examine the chemical basis for the reported enhanced reactivity. Their studies suggested that the enhance curing in the presence of esters could be due to enhanced quinone methide formation or enhanced intermolecular SN2 reactions. In either case the esters do not function as true catalysts as they are consumed in the reaction and were not found to be incorporated in the polymerized resin product. An alternative approach to accelerated PF curing can be accomplished with the addition amines or amides. The later functionality undergoes base catalyzed hydrolysis yielding the corresponding carboxyl ate and free amine which rapidly reacts with the phenolic methylol groups facilitating polymerization and curing of the PF resin (Pizzi, 1997).« less

Travelers with cutaneous leishmaniasis cured without systemic therapy.

PubMed

Morizot, G; Kendjo, E; Mouri, O; Thellier, M; Pérignon, A; Foulet, F; Cordoliani, F; Bourrat, E; Laffitte, E; Alcaraz, I; Bodak, N; Ravel, C; Vray, M; Grogl, M; Mazier, D; Caumes, E; Lachaud, L; Buffet, P A

2013-08-01

Cutaneous leishmaniasis (CL) is a disfiguring but not life-threatening disease. Because antileishmanial drugs are potentially toxic, the World Health Organization (WHO) recommends simple wound care or local therapy as first-line treatment, followed or replaced by systemic therapy if local therapy fails or cannot be performed. To determine the feasibility and impact of the recommended approach, we analyzed the results of a centralized referral treatment program in 135 patients with parasitologically proven CL. Infections involved 10 Leishmania species and were contracted in 29 different countries. Eighty-four of 135 patients (62%) were initially treated without systemic therapy. Of 109 patients with evaluable charts, 23 of 25 (92%) treated with simple wound care and 37 of 47 (79%) treated with local antileishmanial therapy were cured by days 42-60. In 37 patients with large or complex lesions, or preexisting morbidities, or who had not been cured with local therapy, the cure rate with systemic antileishmanial agents was 60%. Systemic adverse events were observed in 15 patients, all receiving systemic therapy. In this population of CL patients displaying variable degrees of complexity and severity, almost two-thirds of patients could be initially managed without systemic therapy. Of these, 60 were cured before day 60. The WHO-recommended stepwise approach favoring initial local therapy therefore resulted in at least 44% of all patients being cured without exposure to the risk of systemic adverse events. Efforts are needed to further simplify local therapy of CL and to improve the management of patients with complex lesions and/or preexisting comorbidities.

From Composition to Cure: A Systems Engineering Approach to Anticancer Drug Carriers.

PubMed

MacEwan, Sarah R; Chilkoti, Ashutosh

2017-06-06

The molecular complexity and heterogeneity of cancer has led to a persistent, and as yet unsolved, challenge to develop cures for this disease. The pharmaceutical industry focuses the bulk of its efforts on the development of new drugs, but an alternative approach is to improve the delivery of existing drugs with drug carriers that can manipulate when, where, and how a drug exerts its therapeutic effect. For the treatment of solid tumors, systemically delivered drug carriers face significant challenges that are imposed by the pathophysiological barriers that lie between their site of administration and their site of therapeutic action in the tumor. Furthermore, drug carriers face additional challenges in their translation from preclinical validation to clinical approval and adoption. Addressing this diverse network of challenges requires a systems engineering approach for the rational design of optimized carriers that have a realistic prospect for translation from the laboratory to the patient. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Cationic cure kinetics of a polyoxometalate loaded epoxy nanocomposite

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

Anderson, Benjamin J.

2012-08-06

The reaction cure kinetics of a novel polyoxometalate (POM) loaded epoxy nanocomposite is described. The POM is dispersed in the epoxy resin up to volume fractions of 0.1. Differential scanning calorimetry measurements show the cure of the epoxy resin to be sensitive to the POM loading. A kinetics study of the cure exotherm confirms that POM acts as a catalyst promoting cationic homopolymerization of the epoxy resin. The cure reaction is shown to propagate through two cure regimes. A fast cure at short time is shown to be propagation by the activated chain end (ACE) mechanism. A slow cure atmore » long time is shown to be propagation by the activated monomer (AM) mechanism. The activation energies for the fast and slow cure regimes agree well with other epoxy based systems that have been confirmed to propagate by the ACE and AM mechanisms.« less

Effects of curing conditions on the structure of sodium carboxymethyl starch/mineral matrix system: FT-IR investigation.

PubMed

Kaczmarska, Karolina; Grabowska, Beata; Bobrowski, Artur; Cukrowicz, Sylwia

2018-04-24

Strength properties of the microwave cured molding sands containing binders in a form of the aqueous solution of sodium carboxymethyl starch (CMS-Na) are higher than the same molding composition cured by conventional heating. Finding the reason of this effect was the main purpose in this study. Structural changes caused by both physical curing methods of molding sands systems containing mineral matrix (silica sand) and polymer water-soluble binder (CMS-Na) were compared. It was shown, by means of the FT-IR spectroscopic studies, that the activation of the polar groups in the polymer macromolecules structure as well as silanol groups on the mineral matrix surfaces was occurred in the microwave radiation. Binding process in microwave-cured samples was an effect of formation the hydrogen bonds network between hydroxyl and/or carbonyl groups present in polymer and silanol groups present in mineral matrix. FT-IR studies of structural changes in conventional and microwave cured samples confirm that participation of hydrogen bonds is greater after microwave curing than conventional heating. Copyright © 2018 Elsevier B.V. All rights reserved.

Out of the Autoclave Fabrication of LaRC[TradeMark] PETI-9 Polyimide Laminates

NASA Technical Reports Server (NTRS)

Cano, Robert J.; Jensen, Brian J.

2013-01-01

The NASA Langley Research Center developed polyimide system, LaRC PETI-9, has successfully been processed into composites by high temperature vacuum assisted resin transfer molding (HT-VARTM). To extend the application of this high use temperature material to other out-of-autoclave (OOA) processing techniques, the fabrication of PETI- 9 laminates was evaluated using only a vacuum bag and oven cure. A LaRC PETI-9 polyimide solution in NMP was prepared and successfully utilized to fabricate unidirectional IM7 carbon fiber prepreg that was subsequently processed into composites with a vacuum bag and oven cure OOA process. Composite panels of good quality were successfully fabricated and mechanically tested. Processing characteristics, composite panel quality and mechanical properties are presented in this work. The resultant properties are compared to previously developed LaRC material systems processed by both autoclave and OOA techniques including the well characterized, autoclave processed LaRC PETI-5.

An investigation of the curing process for moisture-crosslinkable polyethylene used in cable coating extrusion

NASA Astrophysics Data System (ADS)

Cantor, Kirk Martin

1998-12-01

Moisture-crosslinkable polyethylene used in the extrusion coating of electrical cable has many advantages over other polymer systems used for crosslinked cable coating. However, one of its major drawbacks is the long cure times required. The purpose of this study was to describe how curing takes place in cable systems using moisture-crosslinkable polyethylene, with an ultimate goal of gaining insight into how cure times might be reduced. Crosslinking was investigated with an emphasis on how the curing reaction proceeds through the coating, using analyses to characterize processing conditions and resulting mechanical and structural properties. In the design of the study, material compounds were varied as were curing conditions. Cable coatings were sectioned by position through the coating thickness and characterized using several techniques. Mechanical, thermal, and structural properties of the polymer coating were measured. A significant finding from the study was that the degree of cure was highest at positions in the coating closest to the conductor. Because this was opposite to what was expected, an investigation into the cause of this finding was pursued. It was found that during cure at elevated temperature, the inside surface of the coating remains at a generally higher temperature than the outside surface. This provides a more favorable cure condition for positions in the coating closest to the conductor. Based on the results of this study, a list of suggested follow-up studies is provided at the end of the dissertation. One proposal for investigating reduced cure times involves providing heat to the interior of the cable during cure.

A comparison between the effects of gamma radiation and sulfur cure system on the microstructure and crosslink network of (styrene butadiene rubber/ethylene propylene diene monomer) blends in presence of nanoclay

NASA Astrophysics Data System (ADS)

Shoushtari Zadeh Naseri, Aida; Jalali-Arani, Azam

2015-10-01

Rubber blends based on (styrene-butadiene rubber (SBR)/ethylene-propylene-diene monomer (EPDM)) with and without organoclay (OC) were prepared through a melt mixing process. The concentration ratio of the rubber phases (EPDM/SBR; 50/50 wt%) and the amount of the OC were kept constant. The samples were then vulcanized by means of gamma radiation using a Co-60 gamma source as well as sulfur cure system. The effect of absorbed dose on the formation of the crosslinks was confirmed by the Fourier transform infrared spectroscopy (FTIR). The effects of absorbed dose, sulfur cure system and OC on the gel content, and crosslink density were evaluated by the chemical tests. Applying the Charlesby-Pinner equation to estimate the radiation chemical yield, revealed that the use of OC in the blend caused 20% reduction in the degradation/crosslinking ratio. Employing the swelling test data, some thermodynamic parameters were determined. Using field emission scanning electron microscopy (FE-SEM) to investigate microstructure of the samples revealed a more homogeneous structure and also an increase in compatibility of the blend components in the sample cured by the irradiation in comparison to that cured by the sulfur curing system.

A Call to Develop Course-Based Undergraduate Research Experiences (CUREs) for Nonmajors Courses

PubMed Central

Ballen, Cissy J.; Blum, Jessamina E.; Brownell, Sara; Hebert, Sadie; Hewlett, James; Klein, Joanna R.; McDonald, Erik A.; Monti, Denise L.; Nold, Stephen C.; Slemmons, Krista E.; Soneral, Paula A. G.; Cotner, Sehoya

2017-01-01

Course-based undergraduate research experiences (CUREs) for non–science majors (nonmajors) are potentially distinct from CUREs for developing scientists in their goals, learning objectives, and assessment strategies. While national calls to improve science, technology, engineering, and mathematics education have led to an increase in research revealing the positive effects of CUREs for science majors, less work has specifically examined whether nonmajors are impacted in the same way. To address this gap in our understanding, a working group focused on nonmajors CUREs was convened to discuss the following questions: 1) What are our laboratory-learning goals for nonmajors? 2) What are our research priorities to determine best practices for nonmajors CUREs? 3) How can we collaborate to define and disseminate best practices for nonmajors in CUREs? We defined three broad student outcomes of prime importance to the nonmajors CURE: improvement of scientific literacy skills, proscience attitudes, and evidence-based decision making. We evaluated the state of knowledge of best practices for nonmajors, and identified research priorities for the future. The report that follows is a summary of the conclusions and future directions from our discussion. PMID:28450449

Influence of Curing on the Strength Development of Calcium-Containing Geopolymer Mortar

PubMed Central

Li, Xueying; Wang, Zheng; Jiao, Zhenzhen

2013-01-01

This paper investigated the curing effects on the mechanical properties of calcium-containing geopolymer mortar. Three precursors are used: Class C fly ash, Class F fly ash plus calcium hydroxide and Class F fly ash plus slag. Curing conditions included: (1) standard curing at 20 ± 3 °C and RH 95% (C); (2) steam curing at 60 °C for 24 h (S); (3) steam curing at 60 °C for 6 h (S6); and (4) oven curing at 60 °C for 24 h (O), then the latter three followed by the standard curing. Under the standard conditions, the flexural strength and compressive strength of Class C fly ash geopolymer mortars developed quickly until the age of 7 days, followed by a gradual increase. Specimens with Class F fly ash plus Ca(OH)2 showed slow increase till the age of 28 days. Under these non-standard conditions (2–4), all specimens showed higher 3-day strength, while later strengths were either higher or lower than those in standard conditions, depending on the type of the precursor. PMID:28788377

Influence of Curing on the Strength Development of Calcium-Containing Geopolymer Mortar.

PubMed

Li, Xueying; Wang, Zheng; Jiao, Zhenzhen

2013-11-07

This paper investigated the curing effects on the mechanical properties of calcium-containing geopolymer mortar. Three precursors are used: Class C fly ash, Class F fly ash plus calcium hydroxide and Class F fly ash plus slag. Curing conditions included: (1) standard curing at 20 ± 3 °C and RH 95% (C); (2) steam curing at 60 °C for 24 h (S); (3) steam curing at 60 °C for 6 h (S6); and (4) oven curing at 60 °C for 24 h (O), then the latter three followed by the standard curing. Under the standard conditions, the flexural strength and compressive strength of Class C fly ash geopolymer mortars developed quickly until the age of 7 days, followed by a gradual increase. Specimens with Class F fly ash plus Ca(OH)₂ showed slow increase till the age of 28 days. Under these non-standard conditions (2-4), all specimens showed higher 3-day strength, while later strengths were either higher or lower than those in standard conditions, depending on the type of the precursor.

Involvement of the immune response in the cure of metastatic murine CT-26 colon carcinoma by low electric field-enhanced chemotherapy.

PubMed

Plotnikov, Alexander; Tichler, Thomas; Korenstein, Rafi; Keisari, Yona

2005-12-10

Low electric field cancer treatment-enhanced chemotherapy (LEFCT-EC) is a new treatment modality that combines chemotherapeutic agents and low electric field stimulation. LEFCT-EC was found to destroy malignant mouse tumors and cause massive death of tumor cells. This may enable the immune system cells to efficiently recognize and eliminate tumor cells at the primary tumor site and at metastatic foci. Mice with 15 mm diameter intracutaneous colon carcinomas (CT-26) were injected with BCNU (35 mg/kg), and 2 min later the tumors were exposed to low electric fields (intensity 40 V/cm, pulse duration 180 micros, frequency 500 Hz) for 12 min (LEFCT-EC). We found that treatment with LEFCT-EC achieved complete cure of 93% of the animals. In comparison, electric fields alone (13% cure), chemotherapy alone (0%), surgery (15%) or a combination of surgery and bis-chloroethyl-nitrosurea, carmustine (BCNU; 84%) treatments resulted in lower cure rates. After treatment and cure with LEFCT-EC, 50% of the cured mice developed resistance to a tumor challenge (surgery + BCNU only 15%). Furthermore, splenocytes from cured animals protected naive animals from a tumorigenic dose of tumor cells. Separation of spleen cells into lymphocyte subpopulations indicated a major role for CD4 and CD8 T cells in this protection. FACS analysis revealed restoration of normal splenocyte subpopulation proportions impaired by cytotoxic chemotherapy. Our results suggest that LEFCT-EC can directly destroy primary tumors and facilitate the destruction of metastatic disease by enforcement of antitumor immune responses. Copyright 2005 Wiley-Liss, Inc

Fiber-optic epoxy composite cure sensor. I. Dependence of refractive index of an autocatalytic reaction epoxy system at 850 nm on temperature and extent of cure

NASA Astrophysics Data System (ADS)

Lam, Kai-Yuen; Afromowitz, Martin A.

1995-09-01

We discuss the behavior of the refractive index of a typical epoxy-aromatic diamine system. Near 850 nm the index of refraction is found to be largely controlled by the density of the epoxy. Models are derived to describe its dependence on temperature and extent of cure. Within the range of temperatures studied, the refractive index decreases linearly with increasing temperature. In addition, as the epoxy is cured, the refractive index increases linearly with conversion to the gel point. >From then on, shrinkage in the volume of the epoxy is restricted by local viscosity. Therefore the linear relationship between the refractive index and the extent of cure does not hold beyond the gel point.

Chronic hepatitis B: Virology, natural history, current management and a glimpse at future opportunities.

PubMed

Gish, Robert G; Given, Bruce D; Lai, Ching-Lung; Locarnini, Stephen A; Lau, Johnson Y N; Lewis, David L; Schluep, Thomas

2015-09-01

The host immune system plays an important role in chronic hepatitis B (CHB), both in viral clearance and hepatocellular damage. Advances in our understanding of the natural history of the disease have led to redefining the major phases of infection, with the "high replicative, low inflammatory" phase now replacing what was formerly termed the "immune tolerant" phase, and the "nonreplicative phase" replacing what was formerly termed the "inactive carrier" phase. As opposed to the earlier view that HBV establishes chronic infection by exploiting the immaturity of the neonate's immune system, new findings on trained immunity show that the host is already somewhat "matured" following birth, and is actually very capable of responding immunologically, potentially altering future hepatitis B treatment strategies. While existing therapies are effective in reducing viral load and necroinflammation, often restoring the patient to near-normal health, they do not lead to a cure except in very rare cases and, in many patients, viremia rebounds after cessation of treatment. Researchers are now challenged to devise therapies that will eliminate infection, with a particular focus on eliminating the persistence of viral cccDNA in the nuclei of hepatocytes. In the context of chronic hepatitis B, new definitions of 'cure' are emerging, such as 'functional' and 'virological' cure, defined by stable off-therapy suppression of viremia and antigenemia, and the normalization of serum ALT and other liver-related laboratory tests. Continued advances in the understanding of the complex biology of chronic hepatitis B have resulted in the development of new, experimental therapies targeting viral and host factors and pathways previously not accessible to therapy, approaches which may lead to virological cures in the near term and functional cures upon long term follow-up. This article forms part of a symposium in Antiviral Research on "An unfinished story: from the discovery of the Australia antigen to the development of new curative therapies for hepatitis B." Copyright © 2015 Elsevier B.V. All rights reserved.

Chemoviscosity modeling for thermosetting resin systems, 4

NASA Technical Reports Server (NTRS)

Hou, T. H.; Huang, Joan Y. Z.

1989-01-01

An experimental study on the changes of chemorheological properties has been conducted and analyzed on commercial Hercules 3501-6 resin system cured under several isothermal conditions between 375 and 435 K. For the cure temperatures equal to or greater than 385 K, the storage modulus curing curves, G prime (t), exhibited abrupt changes in slope which occurred at various times depending on the curing temperatures and were attributed to the onset of gelation reactions. The crossover points between G prime (t) and G double prime (t) curves were observed for curing temperatures equal to or greater than 400 K. The gelation and the crossover points obtained from the chemorheological measurements, therefore, defined two characteristic resin states during cure. Approximately the same value for the degree of cure was reached by the advancement of the reaction at each of these states. The temperature dependency of the viscosities for the characteristic resin states and the rate constants of increase in moduli at different stages of curing were analyzed. Various G prime (t) and G double prime (t) isothermal curing curves were also shown to be capable of being superimposed on one another by the principle of time-temperature superposition. The resultant shift factors a sub t(t) and a Eta(T) were shown to follow the Arrhenius type relationship. Values of the activation energy suggested that the reaction kinetics, instead of the diffusion mechanism, was the limiting step in the overall resin advancement for the cure at temperatures equal to or greater than 385 K.

New processable modified polyimide resins for adhesive and matrix applications

NASA Technical Reports Server (NTRS)

Landman, D.

1985-01-01

A broad product line of bismaleimide modified epoxy adhesives which are cured by conventional addition curing methods is described. These products fill a market need for 232 C (450 F) service adhesives which are cured in a manner similar to conventional 177 C (350 F) epoxy adhesives. The products described include film adhesives, pastes, and a primer. Subsequent development work has resulted in a new bismaleimide modified epoxy resin which uses a unique addition curing mechanism. This has resulted in products with improved thermomechanical properties compared to conventional bismaleimide epoxy resins. A film adhesive, paste, and matrix resin for composites using this new technology are described. In all cases, the products developed are heat cured by using typical epoxy cure cycles i.e., 1 hour at 177 C (350 F) followed by 2 hours postcure at 246 C (475 F).

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

Keeratitham, Waralee, E-mail: waralee.ke@student.chula.ac.th; Somwangthanaroj, Anongnat, E-mail: anongnat.s@chula.ac.th

Herein, our main objective is to prepare the fast curing epoxy system with high glass transition temperature (T{sub g}) by incorporating the multifunctional epoxy resin into the mixture of diglycidyl ether of bisphenol A (DGEBA) as a major epoxy component and aromatic diamine as a hardener. Furthermore, the curing behavior as well as thermal and thermomechanical properties were investigated by differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA) and thermomechanical analysis (TMA). It was found that T{sub g} obtained from tan δ of DGEBA/aromatic diamine system increased from 100 °C to 205 °C with the presence of 30 percentage bymore » weight of multifunctional epoxy resin. Additionally, the isothermal DSC results showed that the multifunctional epoxy resin can accelerate the curing reaction of DGEBA/aromatic diamine system. Namely, a high degree of curing (∼90%) was achieved after a few minutes of curing at low temperature of 130 °C, owing to a large number of epoxy ring of multifunctional epoxy resin towards the active hydrogen atoms of aromatic diamine.« less

Physician perceptions of HIV cure in China: A mixed methods review and implications for HIV cure research.

PubMed

Rich, Zachary Clarke; Liu, Chuncheng; Ma, Qingyan; Hu, Fengyu; Cai, Weiping; Tang, Xiaoping; Tucker, Joseph David

2015-09-01

There are over 100 clinical trials worldwide focused on developing an HIV cure. Research participants will assume substantial individual risks while receiving little or no individual benefit. Physicians will have important dual roles of leading HIV cure research studies and guiding patient expectations. Many low and middle-income nations have started HIV cure trials, including China. The goal of this study was to better understand physician attitudes, behaviors, and perceptions of HIV cure research within the context of China. We conducted a quantitative and qualitative evidence review of published literature on physician perceptions of HIV cure in China. Quantitative survey data revealed that physicians rarely believed HIV was curable, but this perception may be more common compared to other countries. Qualitative data showed that inconsistent terminology used among physicians may contribute to the perception of HIV as curable. The belief that HIV is curable among some physicians in China may be related to the influence of traditional Chinese medicine beliefs. Rather than seeking elimination of pathogens, traditional Chinese medicine aims to achieve harmony between organs and a vital life force. In this context, HIV infection can be seen as a temporary state of imbalance rather than an irreversible change. There is a wide range of physician perceptions about HIV cure in China. Conflicting information about HIV cure from physicians and other sources could thwart the progress of HIV cure research. Enhancing patient-physician communication about ongoing HIV cure research trials will be important for developing an HIV cure.

Residual Stress Developed During the Cure of Thermosetting Polymers: Optimizing Cure Schedule to Minimize Stress.

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

Kropka, Jamie Michael; Stavig, Mark E.; Jaramillo, Rex

When thermosetting polymers are used to bond or encapsulate electrical, mechanical or optical assemblies, residual stress, which often affects the performance and/or reliability of these devices, develops within the structure. The Thin-Disk-on-Cylinder structural response test is demonstrated as a powerful tool to design epoxy encapsulant cure schedules to reduce residual stress, even when all the details of the material evolution during cure are not explicitly known. The test's ability to (1) distinguish between cohesive and adhesive failure modes and (2) demonstrate methodologies to eliminate failure and reduce residual stress, make choices of cure schedules that optimize stress in the encapsulantmore » unambiguous. For the 828/DEA/GMB material in the Thin-Disk-on-Cylinder geometry, the stress associated with cure is significant and outweighs that associated with cool down from the final cure temperature to room temperature (for measured lid strain, Scure I > I I e+h erma * II) * The difference between the final cure temperature and 1 1 -- the temperature at which the material gels, Tf-T ge i, was demonstrated to be a primary factor in determining the residual stress associated with cure. Increasing T f -T ge i leads to a reduction in cure stress that is described as being associated with balancing some of the 828/DEA/GMB cure shrinkage with thermal expansion. The ability to tune residual stress associated with cure by controlling T f -T ge i would be anticipated to translate to other thermosetting encapsulation materials, but the times and temperatures appropriate for a given material may vary widely.« less

Energy curable compositions having improved cure speeds

DOEpatents

Halm, L.W.

1993-05-18

The composition and method provide improved physical properties and cure speed of polyurethane precursors, with or without free radical polymerizable monomers or oligomers present, by use of a two component catalyst system. The resin blend can be activated with a latent organometallic catalyst combined with an organic peroxide which can be a hydroperoxide or an acyl peroxide to decrease the cure time while increasing the break energy and tangent modulus of the system.

Energy curable compositions having improved cure speeds

DOEpatents

Halm, Leo W.

1993-01-01

A composition and method provide improved physical properties and cure speed of polyurethane precursors, with or without free radical polymerizable monomers or oligomers present, by use of a two component catalyst system. The resin blend can be activated with a latent organometallic catalyst combined with an organic peroxide which can be a hydroperoxide or an acyl peroxide to decrease the cure time while increasing the break energy and tangent modulus of the system.

Cushing's syndrome: aftermath of the cure.

PubMed

Pivonello, Rosario; De Martino, Maria Cristina; De Leo, Monica; Tauchmanovà, Libuse; Faggiano, Antongiulio; Lombardi, Gaetano; Colao, Annamaria

2007-11-01

Cushing's syndrome (CS) is a chronic and systemic disease caused by endogenous or exogenous hypercortisolism, associated with an increase of mortality rate due to the clinical consequences of glucocorticoid excess, especially cardiovascular diseases. After cure, usually obtained by the surgical removal of the tumor responsible for the disease, the normalization of cortisol secretion is not constantly followed by the recovery of the clinical complications developed during the active disease, and it is often followed by the development of novel clinical manifestations induced by the fall of cortisol levels. These evidences were mostly documented in patients with pituitary-dependent CS, after surgical resection of the pituitary tumor. Indeed, despite an improvement of the mortality rate, metabolic syndrome and the consequent cardiovascular risk have been found to partially persist after disease remission, strictly correlated to the insulin resistance. Skeletal diseases, mainly osteoporosis, improve after normalization of cortisol levels but require a long period of time or the use of specific treatment, mainly bisphosphonates, to reach the normalization of bone mass. A relevant improvement or resolution of mental disturbances has been described in patients cured from CS, although in several cases, cognitive decline persisted and psychological or psychiatric improvement was erratic, delayed, or incomplete. On the other hand, development or exacerbation of autoimmune disorders, mainly thyroid autoimmune diseases, was documented in predisposed patients with CS after disease remission. The totality of these complications persisting or occurring after successful treatment contribute to the impairment of quality of life registered in patients with CS after disease cure.

Chemotherapy of Second Stage Human African Trypanosomiasis: Comparison between the Parenteral Diamidine DB829 and Its Oral Prodrug DB868 in Vervet Monkeys

PubMed Central

Thuita, John K.; Wolf, Kristina K.; Murilla, Grace A.; Bridges, Arlene S.; Boykin, David W.; Mutuku, James N.; Liu, Qiang; Jones, Susan K.; Gem, Charles O.; Ching, Shelley; Tidwell, Richard R.; Wang, Michael Z.; Paine, Mary F.; Brun, Reto

2015-01-01

Human African trypanosomiasis (HAT, sleeping sickness) ranks among the most neglected tropical diseases based on limited availability of drugs that are safe and efficacious, particularly against the second stage (central nervous system [CNS]) of infection. In response to this largely unmet need for new treatments, the Consortium for Parasitic Drug Development developed novel parenteral diamidines and corresponding oral prodrugs that have shown cure of a murine model of second stage HAT. As a rationale for selection of one of these compounds for further development, the pharmacokinetics and efficacy of intramuscular (IM) active diamidine 2,5-bis(5-amidino-2-pyridyl)furan (DB829; CPD-0802) and oral prodrug2,5-bis[5-(N-methoxyamidino)-2-pyridyl]furan (DB868) were compared in the vervet monkey model of second stage HAT. Treatment was initiated 28 days post-infection of monkeys with T. b. rhodesiense KETRI 2537. Results showed that IM DB829 at 5 mg/kg/day for 5 consecutive days, 5 mg/kg/day every other day for 5 doses, or 2.5 mg/kg/day for 5 consecutive days cured all monkeys (5/5). Oral DB868 was less successful, with no cures (0/2) at 3 mg/kg/day for 10 days and cure rates of 1/4 at 10 mg/kg/day for 10 days and 20 mg/kg/day for 10 days; in total, only 2/10 monkeys were cured with DB868 dose regimens. The geometric mean plasma Cmax of IM DB829 at 5 mg/kg following the last of 5 doses was 25-fold greater than that after 10 daily oral doses of DB868 at 20 mg/kg. These data suggest that the active diamidine DB829, administered IM, should be considered for further development as a potential new treatment for second stage HAT. PMID:25654243

Autogenous accelerated curing of concrete cylinders. Part V, ASTM Cooperative Testing Program with additional emphasis on the influence of container and storage characteristics (supplemented by data on water bath curing from an earlier council project).

DOT National Transportation Integrated Search

1971-01-01

Concomitant with the Research Council's studies of accelerated curing for strength testing, Subcommittee II-i of ASTM Committee C-9 was developing and refining accelerated methods for standardization. This development included a cooperative testing p...

Intelligent sensor-model automated control of PMR-15 autoclave processing

NASA Technical Reports Server (NTRS)

Hart, S.; Kranbuehl, D.; Loos, A.; Hinds, B.; Koury, J.

1992-01-01

An intelligent sensor model system has been built and used for automated control of the PMR-15 cure process in the autoclave. The system uses frequency-dependent FM sensing (FDEMS), the Loos processing model, and the Air Force QPAL intelligent software shell. The Loos model is used to predict and optimize the cure process including the time-temperature dependence of the extent of reaction, flow, and part consolidation. The FDEMS sensing system in turn monitors, in situ, the removal of solvent, changes in the viscosity, reaction advancement and cure completion in the mold continuously throughout the processing cycle. The sensor information is compared with the optimum processing conditions from the model. The QPAL composite cure control system allows comparison of the sensor monitoring with the model predictions to be broken down into a series of discrete steps and provides a language for making decisions on what to do next regarding time-temperature and pressure.

The Clinical Utilisation of Respiratory Elastance Software (CURE Soft): a bedside software for real-time respiratory mechanics monitoring and mechanical ventilation management.

PubMed

Szlavecz, Akos; Chiew, Yeong Shiong; Redmond, Daniel; Beatson, Alex; Glassenbury, Daniel; Corbett, Simon; Major, Vincent; Pretty, Christopher; Shaw, Geoffrey M; Benyo, Balazs; Desaive, Thomas; Chase, J Geoffrey

2014-09-30

Real-time patient respiratory mechanics estimation can be used to guide mechanical ventilation settings, particularly, positive end-expiratory pressure (PEEP). This work presents a software, Clinical Utilisation of Respiratory Elastance (CURE Soft), using a time-varying respiratory elastance model to offer this ability to aid in mechanical ventilation treatment. CURE Soft is a desktop application developed in JAVA. It has two modes of operation, 1) Online real-time monitoring decision support and, 2) Offline for user education purposes, auditing, or reviewing patient care. The CURE Soft has been tested in mechanically ventilated patients with respiratory failure. The clinical protocol, software testing and use of the data were approved by the New Zealand Southern Regional Ethics Committee. Using CURE Soft, patient's respiratory mechanics response to treatment and clinical protocol were monitored. Results showed that the patient's respiratory elastance (Stiffness) changed with the use of muscle relaxants, and responded differently to ventilator settings. This information can be used to guide mechanical ventilation therapy and titrate optimal ventilator PEEP. CURE Soft enables real-time calculation of model-based respiratory mechanics for mechanically ventilated patients. Results showed that the system is able to provide detailed, previously unavailable information on patient-specific respiratory mechanics and response to therapy in real-time. The additional insight available to clinicians provides the potential for improved decision-making, and thus improved patient care and outcomes.

Infiltration/cure modeling of resin transfer molded composite materials using advanced fiber architectures

NASA Technical Reports Server (NTRS)

Loos, Alfred C.; Weideman, Mark H.; Long, Edward R., Jr.; Kranbuehl, David E.; Kinsley, Philip J.; Hart, Sean M.

1991-01-01

A model was developed which can be used to simulate infiltration and cure of textile composites by resin transfer molding. Fabric preforms were resin infiltrated and cured using model generated optimized one-step infiltration/cure protocols. Frequency dependent electromagnetic sensing (FDEMS) was used to monitor in situ resin infiltration and cure during processing. FDEMS measurements of infiltration time, resin viscosity, and resin degree of cure agreed well with values predicted by the simulation model. Textile composites fabricated using a one-step infiltration/cure procedure were uniformly resin impregnated and void free. Fiber volume fraction measurements by the resin digestion method compared well with values predicted using the model.

Equipment development for automated assembly of solar modules

NASA Technical Reports Server (NTRS)

Hagerty, J. J.

1982-01-01

Prototype equipment was developed which allows for totally automated assembly in the three major areas of module manufacture: cell stringing, encapsulant layup and cure and edge sealing. The equipment is designed to be used in conjunction with a standard Unimate 2000B industrial robot although the design is adaptable to other transport systems.

Feasibility study for the development of low temperature curing adhesives

NASA Technical Reports Server (NTRS)

Green, H. E.; Sutherland, J. D.; Sheppard, C. H.

1974-01-01

The feasibility of a new approach for the development of stable, easily handled, room temperature (293 K - 311 K) curing adhesives was studied and demonstrated. The work concentrated on a family of unsaturated amide/ester resins. Twelve candidate resins were synthesized and tested for completeness of cure at room temperature, adhesion to aluminum and titanium, shear strength, moisture resistance and heat stability. The three most promising candidate resins were selected and recommended for further development.

Modeling the curing process of thermosetting resin matrix composites

NASA Technical Reports Server (NTRS)

Loos, A. C.

1986-01-01

A model is presented for simulating the curing process of a thermosetting resin matrix composite. The model relates the cure temperature, the cure pressure, and the properties of the prepreg to the thermal, chemical, and rheological processes occurring in the composite during cure. The results calculated with the computer code developed on the basis of the model were compared with the experimental data obtained from autoclave-curved composite laminates. Good agreement between the two sets of results was obtained.

A Study of Upgraded Phenolic Curing for RSRM Nozzle Rings

NASA Technical Reports Server (NTRS)

Smartt, Ziba

2000-01-01

A thermochemical cure model for predicting temperature and degree of cure profiles in curing phenolic parts was developed, validated and refined over several years. The model supports optimization of cure cycles and allows input of properties based upon the types of material and the process by which these materials are used to make nozzle components. The model has been refined to use sophisticated computer graphics to demonstrate the changes in temperature and degree of cure during the curing process. The effort discussed in the paper will be the conversion from an outdated solid modeling input program and SINDA analysis code to an integrated solid modeling and analysis package (I-DEAS solid model and TMG). Also discussed will be the incorporation of updated material properties obtained during full scale curing tests into the cure models and the results for all the Reusable Solid Rocket Motor (RSRM) nozzle rings.

Fourier transform infrared (FTIR) fiber optic monitoring of composites during cure in an autoclave

NASA Technical Reports Server (NTRS)

Druy, Mark A.; Elandjian, Lucy; Stevenson, William A.; Driver, Richard D.; Leskowitz, Garett M.

1990-01-01

Real-time in situ monitoring of the chemical states of epoxy resins was investigated during cure in an autoclave using infrared evanescent spectroscopy. Fiber evanescent sensors were developed which may be sandwiched between the plies of the prepreg sample. A short length of sapphire fiber was used as the sensor cell portion of the fiber probe. Heavy metal fluoride glass optical fiber cables were designed for connecting the FTIR spectrometer to the sensor fiber within the autoclave. The sapphire fibers have outstanding mechanical thermal properties which should permit their use as an embedded link in all thermoset composites. The system is capable of operation at a temperature of 250 C for periods up to 8 hours without major changes to the fiber transmission. A discussion of the selection of suitable sensor fibers, the construction of a fiber-optic interface, and the interpretation of in situ infrared spectra of the curing process is presented.

Fast and efficient three-step target-specific curing of a virulence plasmid in Salmonella enterica.

PubMed

de Moraes, Marcos H; Teplitski, Max

2015-12-01

Virulence plasmids borne by serovars of Salmonella enterica carry genes involved in its pathogenicity, as well as other functions. Characterization of phenotypes associated with virulence plasmids requires a system for efficiently curing strains of their virulence plasmids. Here, we developed a 3-step protocol for targeted curing of virulence plasmids. The protocol involves insertion of an I-SecI restriction site linked to an antibiotic resistance gene into the target plasmid using λ-Red mutagenesis, followed by the transformation with a temperature-sensitive auxiliary plasmid which carries I-SecI nuclease expressed from a tetracycline-inducible promoter. Finally, the auxiliary plasmid is removed by incubation at 42 °C and the plasmid-less strains are verified on antibiotic-containing media. This method is fast and very efficient: over 90 % of recovered colonies lacked their virulence plasmid.

Controlling levonorgestrel binding and release in a multi-purpose prevention technology vaginal ring device.

PubMed

Murphy, Diarmaid J; Boyd, Peter; McCoy, Clare F; Kumar, Sandeep; Holt, Jonathon D S; Blanda, Wendy; Brimer, Andrew N; Malcolm, R Karl

2016-03-28

Despite a long history of incorporating steroids into silicone elastomers for drug delivery applications, little is presently known about the propensity for irreversible drug binding in these systems. In this study, the ability of the contraceptive progestin levonorgestrel to bind chemically with hydrosilane groups in addition-cure silicone elastomers has been thoroughly investigated. Cure time, cure temperature, levonorgestrel particle size, initial levonorgestrel loading and silicone elastomer type were demonstrated to be key parameters impacting the extent of levonorgestrel binding, each through their influence on the solubility of levonorgestrel in the silicone elastomer. Understanding and overcoming this levonorgestrel binding phenomenon is critical for the ongoing development of a number of drug delivery products, including a multi-purpose technology vaginal ring device offering simultaneous release of levonorgestrel and dapivirine - a lead candidate antiretroviral microbicide - for combination HIV prevention and hormonal contraception. Copyright © 2016 Elsevier B.V. All rights reserved.

International AIDS Society global scientific strategy: towards an HIV cure 2016.

PubMed

Deeks, Steven G; Lewin, Sharon R; Ross, Anna Laura; Ananworanich, Jintanat; Benkirane, Monsef; Cannon, Paula; Chomont, Nicolas; Douek, Daniel; Lifson, Jeffrey D; Lo, Ying-Ru; Kuritzkes, Daniel; Margolis, David; Mellors, John; Persaud, Deborah; Tucker, Joseph D; Barre-Sinoussi, Françoise; Alter, Galit; Auerbach, Judith; Autran, Brigitte; Barouch, Dan H; Behrens, Georg; Cavazzana, Marina; Chen, Zhiwei; Cohen, Éric A; Corbelli, Giulio Maria; Eholié, Serge; Eyal, Nir; Fidler, Sarah; Garcia, Laurindo; Grossman, Cynthia; Henderson, Gail; Henrich, Timothy J; Jefferys, Richard; Kiem, Hans-Peter; McCune, Joseph; Moodley, Keymanthri; Newman, Peter A; Nijhuis, Monique; Nsubuga, Moses Supercharger; Ott, Melanie; Palmer, Sarah; Richman, Douglas; Saez-Cirion, Asier; Sharp, Matthew; Siliciano, Janet; Silvestri, Guido; Singh, Jerome; Spire, Bruno; Taylor, Jeffrey; Tolstrup, Martin; Valente, Susana; van Lunzen, Jan; Walensky, Rochelle; Wilson, Ira; Zack, Jerome

2016-08-01

Antiretroviral therapy is not curative. Given the challenges in providing lifelong therapy to a global population of more than 35 million people living with HIV, there is intense interest in developing a cure for HIV infection. The International AIDS Society convened a group of international experts to develop a scientific strategy for research towards an HIV cure. This Perspective summarizes the group's strategy.

Effect of Fermented Spinach as Sources of Pre-Converted Nitrite on Color Development of Cured Pork Loin

PubMed Central

Hwang, Ko-Eun

2017-01-01

The effect of fermented spinach extracts on color development in cured meats was investigated in this study. The pH values of raw cured meats without addition of fermented spinach extract or nitrite (negative control) were higher (p<0.05) than those added with fermented spinach extract. The pH values of raw and cooked cured meats in treatment groups were decreased with increasing addition levels of fermented spinach extract. The lightness and yellowness values of raw cured meats formulated with fermented spinach extract were higher (p<0.05) than those of the control groups (both positive and negative controls). The redness values of cooked cured meats were increased with increasing fermented spinach extract levels, whereas the yellowness values of cooked cured meats were decreased with increasing levels of fermented spinach extract. The lowest volatile basic nitrogen (VBN) and thiobarbituric acid reactive substances (TBARS) values were observed in the positive control group with addition of nitrite. TBARS values of cured meats added with fermented spinach extract were decreased with increasing levels of fermented spinach extract and VBN values of curing meat with 30% fermented spinach extract was lower than the other treatments. Total viable bacterial counts in cured meats added with fermented spinach extract ranged from 0.34-1.01 Log CFU/g. E. coli and coliform bacteria were not observed in any of the cured meats treated with fermented spinach extracts or nitrite. Residual nitrite contents in treatment groups were increased with increasing levels of fermented spinach extract added. These results demonstrated that fermented spinach could be added to meat products to improve own curing characteristics. PMID:28316477

Effect of Fermented Spinach as Sources of Pre-Converted Nitrite on Color Development of Cured Pork Loin.

PubMed

Kim, Tae-Kyung; Kim, Young-Boong; Jeon, Ki-Hong; Park, Jong-Dae; Sung, Jung-Min; Choi, Hyun-Wook; Hwang, Ko-Eun; Choi, Yun-Sang

2017-01-01

The effect of fermented spinach extracts on color development in cured meats was investigated in this study. The pH values of raw cured meats without addition of fermented spinach extract or nitrite (negative control) were higher ( p <0.05) than those added with fermented spinach extract. The pH values of raw and cooked cured meats in treatment groups were decreased with increasing addition levels of fermented spinach extract. The lightness and yellowness values of raw cured meats formulated with fermented spinach extract were higher ( p <0.05) than those of the control groups (both positive and negative controls). The redness values of cooked cured meats were increased with increasing fermented spinach extract levels, whereas the yellowness values of cooked cured meats were decreased with increasing levels of fermented spinach extract. The lowest volatile basic nitrogen (VBN) and thiobarbituric acid reactive substances (TBARS) values were observed in the positive control group with addition of nitrite. TBARS values of cured meats added with fermented spinach extract were decreased with increasing levels of fermented spinach extract and VBN values of curing meat with 30% fermented spinach extract was lower than the other treatments. Total viable bacterial counts in cured meats added with fermented spinach extract ranged from 0.34-1.01 Log CFU/g. E. coli and coliform bacteria were not observed in any of the cured meats treated with fermented spinach extracts or nitrite. Residual nitrite contents in treatment groups were increased with increasing levels of fermented spinach extract added. These results demonstrated that fermented spinach could be added to meat products to improve own curing characteristics.

Between remission and cure: patients, practitioners and the transformation of leukaemia in the late twentieth century.

PubMed

Barnes, Emm

2007-12-01

During the course of the 1960s and 1970s, acute leukaemia in childhood ceased to be invariably fatal and was recategorized as curable. The meaning of cure in this case, however, was problematic, as it was impossible for physicians to be certain that cancer would not return. This paper uses historical methods to explore how remission was understood by families with children with acute leukaemia during the period in which the first cures were announced, roughly 1972-77. These comprised documentary analysis of records of the Medical Research Council's leukaemia working parties, published papers and letters on treatments for childhood leukaemia, and interviews with eight UK paediatric oncologists practising in UK hospitals in the 1960s and 1970s. Two approaches to defining 'cure' in leukaemia can be identified. The first relied on statistical assessment of survival rates. I argue that the concept of 'indefinite remission' came to serve for researchers and clinicians as a proxy measure of cure. However, the concept of 'indefinite remission' left many patients and their families quite uncertain as to whether a cure had really happened. A second approach to defining cure therefore developed. Faced with uncertainty, patients, parents and psychologists sought to develop alternative measures of success--including the notion of 'psychological cure'--that brought forward the moment of cure and its relief. Changing conceptualizations of leukaemia shaped and were shaped by negotiations over the meaning of 'remission' and 'cure'. On the one hand, the statistical definition of cure was not available for years. On the other hand, psychological cure could begin from the time of first remission, even if medical absolution was not available for years.

Large size space construction for space exploitation

NASA Astrophysics Data System (ADS)

Kondyurin, Alexey

2016-07-01

Space exploitation is impossible without large space structures. We need to make sufficient large volume of pressurized protecting frames for crew, passengers, space processing equipment, & etc. We have to be unlimited in space. Now the size and mass of space constructions are limited by possibility of a launch vehicle. It limits our future in exploitation of space by humans and in development of space industry. Large-size space construction can be made with using of the curing technology of the fibers-filled composites and a reactionable matrix applied directly in free space. For curing the fabric impregnated with a liquid matrix (prepreg) is prepared in terrestrial conditions and shipped in a container to orbit. In due time the prepreg is unfolded by inflating. After polymerization reaction, the durable construction can be fitted out with air, apparatus and life support systems. Our experimental studies of the curing processes in the simulated free space environment showed that the curing of composite in free space is possible. The large-size space construction can be developed. A project of space station, Moon base, Mars base, mining station, interplanet space ship, telecommunication station, space observatory, space factory, antenna dish, radiation shield, solar sail is proposed and overviewed. The study was supported by Humboldt Foundation, ESA (contract 17083/03/NL/SFe), NASA program of the stratospheric balloons and RFBR grants (05-08-18277, 12-08-00970 and 14-08-96011).

Factors affecting marginal integrity of class II bulk-fill composite resin restorations

PubMed Central

Savadi Oskoee, Siavash; Bahari, Mahmoud; Jafari Navimipour, Elmira; Ajami, Amir Ahmad; Ghiasvand, Negar; Savadi Oskoee, Ayda

2017-01-01

Background. Bulk-fill composite resins are a new type of resin-based composite resins, claimed to have the capacity to be placed in thick layers, up to 4 mm. This study was carried out to evaluate factors affecting gap formation in Cl II cavities restored using the bulk-fill technique. Methods. A total of 60 third molars were used in this study. Two Cl II cavities were prepared in each tooth, one on the mesial aspect 1 mm coronal to the CEJ and one on the distal aspect 1 mm apical to the CEJ. The teeth were divided into 4 groups: A: The cavities were restored using the bulk-fill technique with Filtek P90 composite resin and its adhesive system and light-cured with quartz tungsten halogen (QTH) light-curing unit. B: The cavities were restored similar to that in group A but light-cured with an LED light-curing unit. C: The cavities were restored using the bulk-fill technique with X-tra Fil composite resin and Clearfil SE Bond adhesive system and light-cured with a QTH curing unit. D: The cavities were restored similar to that in group C but light-cured with an LED light-curing unit. The gaps were examined under a stereomicroscope at ×60. Data were analyzed with General Linear Model test. In cases of statistical significance (P<0.05), post hoc Bonferroni test was used for further analyses. Results. The light-curing unit type had no effect on gap formation. However, the results were significant in relation to the composite resin type and margin location (P<0.001). The cumulative effects of light-curing unit*gingival margin and light-curing unit*composite resin type were not significant; however, the cumulative effect of composite rein type*gingival margin was significant (P=0.04) Conclusion. X-tra Fil composite exhibited smaller gaps compared with Filtek P90 composite with both light-curing units. Both composite resins exhibited smaller gaps at enamel margins. PMID:28748051

Solidifying process and flame retardancy of epoxy resin cured with boron-containing phenolic resin

NASA Astrophysics Data System (ADS)

Deng, Peng; Shi, Yan; Liu, Yuansen; Liu, Yuan; Wang, Qi

2018-01-01

For the sake of improving the charring performance and flame retardancy of epoxy resin (EP), boron-containing phenolic resin (BPR) instead of a conventional curing agent, linear phenolic resin (LPR) was employed to cure EP. Of several possible chemical structures for BPR, the existence of benzyl hydroxy groups in BPR chains has been confirmed using 1H nuclear magnetic resonance spectroscopy. The resonance of these groups may reasonably explain the higher curing reactivity of BPR-cured EP than that of LPR-cured EP. Thermogravimetric analysis, observation of the morphologies of the char residues and X-ray photoelectron spectroscopic were performed to characterize the charring process. Due to the presence of B2O3 produced on the char surface from decomposition of phenyl borates and the facile high self-crosslinking reaction of BPR, a more continuous and stronger char barrier was formed for BPR-cured EP compared to that for the LPR-cured EP system. Therefore the former exhibited much better flame retardancy. In addition, BPR-cured EP also displayed better dynamic mechanical properties, than those observed for LPR-cured EP. It is not subject to the significant lowering the glass transition temperature of the polymer which accompanies curing with LPR. This suggests that BPR cured resin may meet the requirement for utilization at high temperature.

A central support system can facilitate implementation and sustainability of a Classroom-based Undergraduate Research Experience (CURE) in Genomics.

PubMed

Lopatto, David; Hauser, Charles; Jones, Christopher J; Paetkau, Don; Chandrasekaran, Vidya; Dunbar, David; MacKinnon, Christy; Stamm, Joyce; Alvarez, Consuelo; Barnard, Daron; Bedard, James E J; Bednarski, April E; Bhalla, Satish; Braverman, John M; Burg, Martin; Chung, Hui-Min; DeJong, Randall J; DiAngelo, Justin R; Du, Chunguang; Eckdahl, Todd T; Emerson, Julia; Frary, Amy; Frohlich, Donald; Goodman, Anya L; Gosser, Yuying; Govind, Shubha; Haberman, Adam; Hark, Amy T; Hoogewerf, Arlene; Johnson, Diana; Kadlec, Lisa; Kaehler, Marian; Key, S Catherine Silver; Kokan, Nighat P; Kopp, Olga R; Kuleck, Gary A; Lopilato, Jane; Martinez-Cruzado, Juan C; McNeil, Gerard; Mel, Stephanie; Nagengast, Alexis; Overvoorde, Paul J; Parrish, Susan; Preuss, Mary L; Reed, Laura D; Regisford, E Gloria; Revie, Dennis; Robic, Srebrenka; Roecklien-Canfield, Jennifer A; Rosenwald, Anne G; Rubin, Michael R; Saville, Kenneth; Schroeder, Stephanie; Sharif, Karim A; Shaw, Mary; Skuse, Gary; Smith, Christopher D; Smith, Mary; Smith, Sheryl T; Spana, Eric P; Spratt, Mary; Sreenivasan, Aparna; Thompson, Jeffrey S; Wawersik, Matthew; Wolyniak, Michael J; Youngblom, James; Zhou, Leming; Buhler, Jeremy; Mardis, Elaine; Leung, Wilson; Shaffer, Christopher D; Threlfall, Jennifer; Elgin, Sarah C R

2014-01-01

In their 2012 report, the President's Council of Advisors on Science and Technology advocated "replacing standard science laboratory courses with discovery-based research courses"-a challenging proposition that presents practical and pedagogical difficulties. In this paper, we describe our collective experiences working with the Genomics Education Partnership, a nationwide faculty consortium that aims to provide undergraduates with a research experience in genomics through a scheduled course (a classroom-based undergraduate research experience, or CURE). We examine the common barriers encountered in implementing a CURE, program elements of most value to faculty, ways in which a shared core support system can help, and the incentives for and rewards of establishing a CURE on our diverse campuses. While some of the barriers and rewards are specific to a research project utilizing a genomics approach, other lessons learned should be broadly applicable. We find that a central system that supports a shared investigation can mitigate some shortfalls in campus infrastructure (such as time for new curriculum development, availability of IT services) and provides collegial support for change. Our findings should be useful for designing similar supportive programs to facilitate change in the way we teach science for undergraduates. © 2014 D. Lopatto et al. CBE—Life Sciences Education © 2014 The American Society for Cell Biology. This article is distributed by The American Society for Cell Biology under license from the author(s). It is available to the public under an Attribution–Noncommercial–Share Alike 3.0 Unported Creative Commons License (http://creativecommons.org/licenses/by-nc-sa/3.0).

Development and Evaluation of the Tigriopus Course-Based Undergraduate Research Experience: Impacts on Students' Content Knowledge, Attitudes, and Motivation in a Majors Introductory Biology Course.

PubMed

Olimpo, Jeffrey T; Fisher, Ginger R; DeChenne-Peters, Sue Ellen

2016-01-01

Within the past decade, course-based undergraduate research experiences (CUREs) have emerged as a viable mechanism to enhance novices' development of scientific reasoning and process skills in the science, technology, engineering, and mathematics disciplines. Recent evidence within the bioeducation literature suggests that student engagement in such experiences not only increases their appreciation for and interest in scientific research but also enhances their ability to "think like a scientist." Despite these critical outcomes, few studies have objectively explored CURE versus non-CURE students' development of content knowledge, attitudes, and motivation in the discipline, particularly among nonvolunteer samples. To address these concerns, we adopted a mixed-methods approach to evaluate the aforementioned outcomes following implementation of a novel CURE in an introductory cell/molecular biology course. Results indicate that CURE participants exhibited more expert-like outcomes on these constructs relative to their non-CURE counterparts, including in those areas related to self-efficacy, self-determination, and problem-solving strategies. Furthermore, analysis of end-of-term survey data suggests that select features of the CURE, such as increased student autonomy and collaboration, mediate student learning and enjoyment. Collectively, this research provides novel insights into the benefits achieved as a result of CURE participation and can be used to guide future development and evaluation of authentic research opportunities. © 2016 J. T. Olimpo et al. CBE—Life Sciences Education © 2016 The American Society for Cell Biology. This article is distributed by The American Society for Cell Biology under license from the author(s). It is available to the public under an Attribution–Noncommercial–Share Alike 3.0 Unported Creative Commons License (http://creativecommons.org/licenses/by-nc-sa/3.0).

Bond strength of a pit-and-fissure sealant associated to etch-and-rinse and self-etching adhesive systems to saliva-contaminated enamel: individual vs. simultaneous light curing.

PubMed

Gomes-Silva, Jaciara Miranda; Torres, Carolina Paes; Contente, Marta Maria Martins Giamatei; Oliveira, Maria Angélica Hueb de Menezes; Palma-Dibb, Regina Guenka; Borsatto, Maria Cristina

2008-01-01

This study evaluated in vitro the shear bond strength (SBS) of a resin-based pit-and-fissure sealant [Fluroshield (F), Dentsply/Caulk] associated with either an etch-and-rinse [Adper Single Bond 2 (SB), 3M/ESPE] or a self-etching adhesive system [Clearfil S3 Bond (S3), Kuraray Co., Ltd.] to saliva-contaminated enamel, comparing two curing protocols: individual light curing of the adhesive system and the sealant or simultaneous curing of both materials. Mesial and distal enamel surfaces from 45 sound third molars were randomly assigned to 6 groups (n=15), according to the bonding technique: I - F was applied to 37% phosphoric acid etched enamel. The other groups were contaminated with fresh human saliva (0.01 mL; 10 s) after acid etching: II - SB and F were light cured separately; III - SB and F were light cured together; IV - S3 and F were light cured separately; V - S3 and F were light cured simultaneously; VI - F was applied to saliva-contaminated, acid-etched enamel without an intermediate bonding agent layer. SBS was tested to failure in a universal testing machine at 0.5 mm/min. Data were analyzed by one-way ANOVA and Fisher's test (alpha=0.05).The debonded specimens were examined with a stereomicroscope to assess the failure modes. Three representative specimens from each group were observed under scanning electron microscopy for a qualitative analysis. Mean SBS in MPa were: I-12.28 (+/-4.29); II-8.57 (+/-3.19); III-7.97 (+/-2.16); IV-12.56 (+/-3.11); V-11.45 (+/-3.77); and VI-7.47 (+/-1.99). In conclusion, individual or simultaneous curing of the intermediate bonding agent layer and the resin sealant did not seem to affect bond strength to saliva-contaminated enamel. S3/F presented significantly higher SBS than the that of the groups treated with SB etch-and-rinse adhesive system and similar SBS to that of the control group, in which the sealant was applied under ideal dry, noncontaminated conditions.

International AIDS Society: Global Scientific Strategy Towards an HIV Cure 2016

PubMed Central

Deeks, Steven G.; Lewin, Sharon R.; Ross, Anna Laura; Ananworanich, Jintanat; Benkirane, Monsef; Cannon, Paula; Chomont, Nicolas; Douek, Daniel; Lifson, Jeffrey D.; Lo, Ying-Ru; Kuritzkes, Daniel; Margolis, David; Mellors, John; Persaud, Deborah; Tucker, Joseph D.; Barre-Sinoussi, Françoise

2017-01-01

Antiretroviral therapy is not curative. Given the challenges in providing life-long therapy to a global population of over 35 million people living with HIV, there is intense interest in developing a cure for HIV infection. The International AIDS Society convened a group of international experts to develop a scientific strategy for research towards an HIV cure. This Perspective summarizes the group's strategy. PMID:27400264

Using Zebrafish to Implement a Course-Based Undergraduate Research Experience to Study Teratogenesis in Two Biology Laboratory Courses

PubMed Central

Chism, Grady W.; Vaughan, Martin A.; Muralidharan, Pooja; Marrs, Jim A.

2016-01-01

Abstract A course-based undergraduate research experience (CURE) spanning three semesters was introduced into freshman and sophomore biology classes, with the hypothesis that participation in a CURE affects skills in research, communication, and collaboration, which may help students persist in science. Student research projects were centered on the hypothesis that nicotine and caffeine exposure during early development affects gastrulation and heart development in zebrafish. First, freshmen generated original data showing distinct effects of embryonic nicotine and caffeine exposure on zebrafish heart development and function. Next, Cell Biology laboratory students continued the CURE studies and identified novel teratogenic effects of nicotine and caffeine during gastrulation. Finally, new freshmen continued the CURE research, examining additional toxicant effects on development. Students designed new protocols, made measurements, presented results, and generated high-quality preliminary data that were studied in successive semesters. By implementing this project, the CURE extended faculty research and provided a scalable model to address national goals to involve more undergraduates in authentic scientific research. In addition, student survey results support the hypothesis that CUREs provide significant gains in student ability to (1) design experiments, (2) analyze data, and (3) make scientific presentations, translating into high student satisfaction and enhanced learning. PMID:26829498

Using Zebrafish to Implement a Course-Based Undergraduate Research Experience to Study Teratogenesis in Two Biology Laboratory Courses.

PubMed

Sarmah, Swapnalee; Chism, Grady W; Vaughan, Martin A; Muralidharan, Pooja; Marrs, Jim A; Marrs, Kathleen A

2016-08-01

A course-based undergraduate research experience (CURE) spanning three semesters was introduced into freshman and sophomore biology classes, with the hypothesis that participation in a CURE affects skills in research, communication, and collaboration, which may help students persist in science. Student research projects were centered on the hypothesis that nicotine and caffeine exposure during early development affects gastrulation and heart development in zebrafish. First, freshmen generated original data showing distinct effects of embryonic nicotine and caffeine exposure on zebrafish heart development and function. Next, Cell Biology laboratory students continued the CURE studies and identified novel teratogenic effects of nicotine and caffeine during gastrulation. Finally, new freshmen continued the CURE research, examining additional toxicant effects on development. Students designed new protocols, made measurements, presented results, and generated high-quality preliminary data that were studied in successive semesters. By implementing this project, the CURE extended faculty research and provided a scalable model to address national goals to involve more undergraduates in authentic scientific research. In addition, student survey results support the hypothesis that CUREs provide significant gains in student ability to (1) design experiments, (2) analyze data, and (3) make scientific presentations, translating into high student satisfaction and enhanced learning.

Molding cork sheets to complex shapes

NASA Technical Reports Server (NTRS)

Sharpe, M. H.; Simpson, W. G.; Walker, H. M.

1977-01-01

Partially cured cork sheet is easily formed to complex shapes and then final-cured. Temperature and pressure levels required for process depend upon resin system used and final density and strength desired. Sheet can be bonded to surface during final cure, or can be first-formed in mold and bonded to surface in separate step.

Fiber-optic epoxy composite cure sensor. II. Performance characteristics

NASA Astrophysics Data System (ADS)

Lam, Kai-Yuen; Afromowitz, Martin A.

1995-09-01

The performance of a fiber-optic epoxy composite cure sensor, as previously proposed, depends on the optical properties and the reaction kinetics of the epoxy. The reaction kinetics of a typical epoxy system are presented. It is a third-order autocatalytic reaction with a peak observed in each isothermal reaction-rate curve. A model is derived to describe the performance characteristics of the epoxy cure sensor. If a composite coupon is cured at an isothermal temperature, the sensor signal can be used to predict the time when the gel point occurs and to monitor the cure process. The sensor is also shown to perform well in nonstoichiometric epoxy matrices. In addition the sensor can detect the end of the cure without calibration.

Assessment of curing behavior of light-activated dental composites using intensity correlation based multiple reference optical coherence tomography.

PubMed

Dsouza, Roshan; Subhash, Hrebesh; Neuhaus, Kai; Kantamneni, Ramakrishna; McNamara, Paul M; Hogan, Josh; Wilson, Carol; Leahy, Martin

2016-01-01

Monitoring the curing kinetics of light-activated resin is a key area of research. These resins are used in restorative applications and particularly in dental applications. They can undergo volumetric shrinkage due to poor control of the depth dependent curing process, modulated by the intensity and duration of the curing light source. This often results in the formation of marginal gaps, causing pain and damage to the restoration site. In this study, we demonstrate the capabilities of a correlation method applied using a multiple references optical coherence tomography (MR-OCT) architecture to monitor the curing of the resin. A MR-OCT system is used in this study to monitor the curing of the resin. The system operates at the center wavelength of 1310 nm with an A-scan rate of 1200 A-scans per second. The axial and lateral resolution of the system is ∼13 μm and ∼27 μm. The method to determine the intensity correlation between adjacent B-frames is based on the Pearson correlation coefficient for a region of interest. Calculating the correlation coefficient for multiple B-frames related to the first B-frame at regular spaced time points, shows for a noncured resin a reduction of the correlation coefficient over time due to Brownian motion. The time constant of the reduction of the correlation value is a measure for the progress of the polymerization during LED light irradiation of the resin. The proposed approach is potentially a low-cost, powerful and unique optical imaging modality for measuring the curing behavior of dental resin and other resins, coatings, and adhesives in medical and industrial applications. To demonstrate the proposed method to monitor the curing process, a light-activated resin composite from GRADIA DIRECT ANTERIOR (GC Corporation, Japan) is studied. The curing time of resin was measured and monitored as a function of depth. The correlation coefficient method is highly sensitive to Brownian motion. The process of curing results in a change in intensity as measured by the MR-OCT signal and hence can be monitored using this method. These results show that MR-OCT has the potential to measure the curing time and monitor the curing process as a function of depth. Moreover, MR-OCT as a product has potential to be compact, low-cost and to fit into a smartphone. Using such a device for monitoring the curing of the resin will be suitable for dentists in stationary and mobile clinical settings. © 2015 Wiley Periodicals, Inc.

Intelligent system design for bionanorobots in drug delivery.

PubMed

Fletcher, Mark; Biglarbegian, Mohammad; Neethirajan, Suresh

A nanorobot is defined as any smart structure which is capable of actuation, sensing, manipulation, intelligence, and swarm behavior at the nanoscale. In this study, we designed an intelligent system using fuzzy logic for diagnosis and treatment of tumors inside the human body using bionanorobots. We utilize fuzzy logic and a combination of thermal, magnetic, optical, and chemical nanosensors to interpret the uncertainty associated with the sensory information. Two different fuzzy logic structures, for diagnosis (Mamdani structure) and for cure (Takagi-Sugeno structure), were developed to efficiently identify the tumors and treat them through delivery of effective dosages of a drug. Validation of the designed system with simulated conditions proved that the drug delivery of bionanorobots was robust to reasonable noise that may occur in the bionanorobot sensors during navigation, diagnosis, and curing of the cancer cells. Bionanorobots represent a great hope for successful cancer therapy in the near future.

Bonding durability of dual-curing composite core material with different self-etching adhesive systems in a model complete vertical root fracture reconstruction.

PubMed

Waidyasekera, Kanchana; Nikaido, Toru; Weerasinghe, Dinesh; Nurrohman, Hamid; Tagami, Junji

2012-04-01

This study evaluated a dual-curing composite along with different dentin adhesive systems for 1 year under water storage, as a new bonding method of root fragments in complete vertical root fracture. Bovine root fragments were bonded with the dual-curing resin composite Clearfil DC Core Automix (DCA) and one of three adhesive systems: two-step self-etching adhesive Clearfil SE Bond (SE), one-step self-etching adhesive Tokuyama Bond Force (BF), one-step dual-curing self-etching adhesive Clearfil DC Bond (DC). Microtensile bond strength (µTBS)/ultimate tensile bond strength (UTS), FE-SEM ultramorphology of fracture modes, and adhesive dentin interface were observed after water storage for periods of up to one year. The data were analyzed with two-way ANOVA. µTBS was influenced by "dentin adhesive system" (F = 324.455, p < 0.001) and "length of water storage" (F = 8.470, p < 0.001). SE yielded significantly higher µTBS, regardless of storage period (p < 0.05) and maintained the initial µTBS without a significant change after 1 year of water storage (p > 0.05). From 24 h to 1 month, BF showed significantly higher bond strength than DC. UTS of DCA was influenced only by the curing mode of the material (F = 5.051, p = 0.027), but not by the length of water storage (F = 0.053, p > 0.05). Two-step self-etching adhesive systems and dual-curing composite core material can be considered as a suitable bonding method for complete root fractures.

Developing protocols for recombinant adeno-associated virus-mediated gene therapy in space.

PubMed

Ohi, S

2000-07-01

With the advent of the era of International Space Station (ISS) and Mars exploration, it is important more than ever to develop means to cure genetic and acquired diseases, which include cancer and AIDS, for these diseases hamper human activities. Thus, our ultimate goal is to develop protocols for gene therapy, which are suitable to humans on the earth as well as in space. Specifically, we are trying to cure the hemoglobinopathies, beta-thalassemia (Cooley's anemia) and sickle cell anemia, by gene therapy. These well-characterized molecular diseases serve as models for developing ex vivo gene therapy, which would apply to other disorders as well. For example, the procedure may become directly relevant to treating astronauts for space-anemia, immune suppression and bone marrow derived tumors, e.g. leukemia. The adeno-associated virus serotype 2 (AAV2) is a non-pathogenic human parvovirus with broad host-range and tissue specificity. Exploiting these characteristics we have been developing protocols for recombinant AAV2 (rAAV)-based gene therapy. With the rAAV constructs and hematopoietic stem cell (HSC) culture systems in hand, we are currently attempting to cure the mouse model of beta-thalassemia [C57BL/6- Hbbth/Hbbth, Hb(d-minor)] by HSC transplantation (HST) as well as by gene therapy. This paper describes the current status of our rAAV-gene therapy research.

A curative regimen would decrease HIV prevalence but not HIV incidence unless targeted to an ART-naïve population.

PubMed

Dimitrov, Dobromir T; Kiem, Hans-Peter; Jerome, Keith R; Johnston, Christine; Schiffer, Joshua T

2016-02-24

HIV curative strategies currently under development aim to eradicate latent provirus, or prevent viral replication, progression to AIDS, and transmission. The impact of implementing curative programs on HIV epidemics has not been considered. We developed a mathematical model of heterosexual HIV transmission to evaluate the independent and synergistic impact of ART, HIV prevention interventions and cure on HIV prevalence and incidence. The basic reproduction number was calculated to study the potential for the epidemic to be eliminated. We explored scenarios with and without the assumption that patients enrolled into HIV cure programs need to be on antiretroviral treatment (ART). In our simulations, curative regimes had limited impact on HIV incidence if only ART patients were eligible for cure. Cure implementation had a significant impact on HIV incidence if ART-untreated patients were enrolled directly into cure programs. Concurrent HIV prevention programs moderately decreased the percent of ART treated or cured patients needed to achieve elimination. We project that widespread implementation of HIV cure would decrease HIV prevalence under all scenarios but would only lower rate of new infections if ART-untreated patients were targeted. Current efforts to identify untreated HIV patients will gain even further relevance upon availability of an HIV cure.

Autogenous accelerated curing of concrete cylinders. Part II, Development of a moisture measuring method.

DOT National Transportation Integrated Search

1970-01-01

Through a literature study, approximately fifty methods of measuring moisture were investigated to ascertain a suitable method for use in measuring moisture changes in 6 inch by 12 inch concrete cylinders cured by the autogenous accelerated curing me...

Internal curing as a new tool for infrastructural renewal : reducing repair congestion, increasing service life, and improving sustainability.

DOT National Transportation Integrated Search

2014-04-01

Internal curing has recently been developed as a new concrete technology that has the potential to : dramatically extend the service life of concrete infrastructure elements like bridge decks. Internal curing : uses prewetted lightweight aggregate in...

Strength Performance of Blended Ash Based Geopolymer Mortar

NASA Astrophysics Data System (ADS)

Zahib, Zaidahtulakmal M.; Kamaruddin, Kartini; Saman, Hamidah M.

2018-03-01

Geopolymer is a based on inorganic alumino-silicate binder system. Geopolymeric materials are formed using materials that containing silica and aluminium such as fly ash and rice husk ash, which activated by alkaline solution. This paper presents the study on the effect of replacement of SSA in RHA based geopolymer, types of curing and different molarity of NaOH used on the strength of Sewage Sludge Ash (SSA) and Rice Husk Ash (RHA) based geopolymer mortar incorporating with three (3) different mix proportions. Based geopolymer mortar was synthesized from treated sewage sludge and rice husk undergoing incineration process in producing ashes, activated with sodium silicate and sodium hydroxide solution by ratio of 2.5:1 and solution to ash ratio of 1:1. Molarity of 8M and 10M NaOH were used. The percentages of SSA replacement were 0%, 10% and 20% by weight. Compressive strength was conducted at age 7, 14 and 28 days to see the development of strength with two curing regimes, which are air curing and oven curing (60°C for 24 hours). From the research conducted, the ultimate compressive strength (6.28MPa) was obtained at zero replacement of SSA taken at 28 days of oven curing with 10M of NaOH. This shows that RHA, which is rich in silica content is enough to enhance the strength of geopolymer mortar especially with high molarity of NaOH.

Chemical analysis of DC745 Materials: DEV Lot 1 reinvestigation; barcodes P053387, P053388, and P053389

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

Dirmyer, Matthew R.

This report serves as a follow up to our initial development lot 1 chemical analysis report (LA-UR-16-21970). The purpose of that report was to determine whether or not certain combinations of resin lots and curing agent lots resulted in chemical differences in the final material. One finding of that report suggested that pad P053389 was different from the three other pads analyzed. This report consists of chemical analysis of P053387, P053388, and a reinvestigation of P053389 all of which came from the potentially suspect combination of resin and curing agents lot. The goal of this report is to determine whethermore » the observations relating to P053389 were isolated to that particular pad or systemic to that combination of resin and curing agent lot. The following suite of analyses were performed on the pads: Differential Scanning Calorimetry (DSC), Thermogravimetric Analysis (TGA), Fourier Transform Infrared Spectroscopy (FT-IR), and Solid State Nuclear Magnetic Resonance (NMR). The overall conclusions of the study are that pads P053387 and P053388 behave more consistently with the pads of other resin lot and curing agent lot combinations and that the chemical observations made regarding pad P053389 are isolated to that pad and not representative of an issue with that resin lot and curing agent lot combination.« less

Freeze-thaw durability of microwave cured air-entrained concrete

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

Pheeraphan, T.; Leung, C.K.Y.

1997-03-01

The strength development of concrete can be greatly accelerated by curing with microwave energy. Microwave curing can therefore be beneficial to construction operations such as concrete precasting and repair. To provide freeze-thaw durability for infrastructure applications, air entrainment has to be introduced. In this investigation, the freeze-thaw resistance of microwave cured air-entrained concrete is measured, and compared to that of air-entrained concrete under normal curing. Their compressive strength at 14 days and air-void characteristics are also measured and compared. The test results indicate that microwave curing can impair the freeze-thaw durability of high w/c concrete but not for low w/cmore » concrete. Also, under microwave curing, the decrease in strength due to air entrainment becomes more significant. Based on these observations, it is recommended that for microwave cured air-entrained concrete, a low w/c ratio should be employed.« less

Biological Course-Based Undergraduate Research Experiences: An Examination of an Introductory Level Implementation

NASA Astrophysics Data System (ADS)

Knoth, Kenneth Charles

Course-based undergraduate research experiences (CUREs) provide authentic research benefits to an entire laboratory course population. CURE experiences are proposed to enhance research skills, critical thinking, productivity, and retention in science. CURE curriculum developers face numerous obstacles, such as the logistics and time commitment involved in bringing a CURE to larger student populations. In addition, an ideal CURE topic requires affordable resources, lab techniques that can be quickly mastered, time for multiple iterations within one semester, and the opportunity to generate new data. This study identifies some of the CURE activities that lead to proposed participant outcomes. Introductory Biology I CURE lab students at Southern Illinois University Edwardsville completed research related to the process of converting storage lipids in microalgae into biodiesel. Data collected from CURE and traditional lab student participants indicate increased CURE student reports of project ownership, scientific self-efficacy, identification as a scientist, and sense of belonging to a science community. Study limitations and unanticipated benefits are discussed.

The stability of new transparent polymeric materials: The epoxy trimethoxyboroxine system. Part 1: The preparation, characterization and curing of epoxy resins and their copolymers

NASA Technical Reports Server (NTRS)

Pearce, E.; Lin, S. C.

1981-01-01

The effects of resin composition, curing conditions fillers, and flame retardant additives on the flammability of diglycidyl ether of bisphenol-A (DGEBA) as measured by the oxygen index is examined. The oxygen index of DGEBA cured with various curing agents was between 0.198 to 0.238. Fillers and flame retardant additives can increase the oxygen index dependent on the material and the amount used. Changes in the basic cured resin properties can be anticipated with the addition of noncompatible additives. High flame resistant epoxy resins with good stability and mechanical properties are investigated.

Influence of power density on polymerization behavior and bond strengths of dual-cured resin direct core foundation systems.

PubMed

Oto, Tatsuki; Yasuda, Genta; Tsubota, Keishi; Kurokawa, Hiroyasu; Miyazaki, Masashi; Platt, Jeffrey A

2009-01-01

This study examined the influence of power density on dentin bond strength and polymerization behavior of dual-cured direct core foundation resin systems. Two commercially available dual-cured direct core foundation resin systems, Clearfil DC Core Automix with Clearfil DC Bond and UniFil Core with Self-Etching Bond, were studied. Bovine mandibular incisors were mounted in autopolymerizing resin and the facial dentin surfaces were ground wet on 600-grit SiC paper. Dentin surfaces were treated according to manufacturer's recommendations. The resin pastes were condensed into the mold and cured with the power densities of 0 (no irradiation), 100, 200, 400 and 600 mW/cm2. Ten specimens per group were stored in 37 degrees C water for 24 hours, then shear tested at a crosshead speed of 1.0 mm/minute in a universal testing machine. An ultrasonic measurement device was used to measure the ultrasonic velocities through the core foundation resins. The power densities selected were 0 (no irradiation), 200, and 600 mW/cm2, and ultrasonic velocity was calculated. ANOVA and Tukey HSD tests were performed at a level of 0.05. The highest bond strengths were obtained when the resin pastes were cured with the highest power density for both core foundation systems (16.8 +/- 1.9 MPa for Clearfil DC Core Automix, 15.6 +/- 2.9 MPa for UniFil Core). When polymerized with the power densities under 200 mW/cm2, significantly lower bond strengths were observed compared to those obtained with the power density of 600 mW/cm2. As the core foundation resins hardened, the sonic velocities increased and this tendency differed among the power density of the curing unit. When the sonic velocities at three minutes after the start of measurements were compared, there were no significant differences among different irradiation modes for UniFil Core, while a significant decrease in sonic velocity was obtained when the resin paste was chemically polymerized compared with dual-polymerization for Clearfil DC Core Automix. The data suggests that the dentin bond strengths and polymerization behavior of the dual-cured, direct core foundation systems are still affected by the power density of the curing unit. With a careful choice of the core foundation systems and power density of the curing unit, the benefit of using resin composites to endodontically-treated teeth might be acceptable.

HIV cure research in South Africa: a preliminary exploration of stakeholder perspectives.

PubMed

Moodley, Keymanthri; Staunton, Ciara; de Roubaix, Malcolm; Cotton, Mark

2016-01-01

Innovative strategies for HIV cure are in development and research studies are being designed and planned globally. South Africa is no exception. However, little is known about stakeholders' knowledge, understanding and expectations of future cure research. This study aimed to obtain in-depth qualitative insights into stakeholder perspectives at this formative stage of HIV cure research. Fifteen stakeholders were interviewed in an HIV research clinic in the Western Cape, South Africa with their consent. Interviews were transcribed verbatim and analysed using thematic content analysis. Broad themes that emerged included the meaning of cure, awareness of HIV cure research, risks and benefits of such research. General awareness and understanding of HIV cure research was lower than expected. Some participants expressed a fatalistic attitude to HIV and described it as an "end-time illness" with no prospect of cure. In general, HIV cure research was regarded as risky - biologically psychologically and socially. If study designs were to include treatment interruption, participants would comply only if success was guaranteed. Given these perceptions of HIV cure research, significant challenges to consent processes and participant recruitment can be anticipated. Authentic community engagement and intensive educational interventions will be necessary prior to future cure research in South Africa.

'I can coexist with HIV': a qualitative study of perceptions of HIV cure among people living with HIV in Guangzhou, China.

PubMed

Ma, Qingyan; Wu, Feng; Henderson, Gail; Rennie, Stuart; Rich, Zachary C; Cheng, Yu; Hu, Fengyu; Cai, Weiping; Tucker, Joseph D

2016-07-01

Little is known about perceptions of HIV cure among people living with HIV (PLHIV), despite them being crucial stakeholders in ongoing HIV cure research. A qualitative research study was conducted in Guangzhou, China, to explore the perceptions of HIV cure among PLHIV in relation to their views on HIV treatment, stigma and social identity. We conducted in-depth interviews with 22 PLHIV from September 2014 to June 2015. Our qualitative data revealed three major themes: (1) Representations of HIV cure: PLHIV generally thought HIV cure was distant from them; (2) Possibility of HIV cure: ideas about the possibility of HIV cure ranged from optimism to scepticism and pessimism; and (3) Life without HIV cure: some participants had adjusted well to the chronic condition of HIV and ART adherence. Although some PLHIV looked forward to HIV being cured, most of the PLHIV in our study had little interest in it. On the contrary, many felt it is more important and realistic to have access to better ART medication and more education for the general public to decrease HIV stigma today rather than develop a cure for tomorrow.

National fire-danger rating system fine-fuel moisture content tables—an Alaskan adaptation.

Treesearch

Richard J. Barney

1969-01-01

Fine-fuel moisture content tables, using dry bulb and dewpoint temperatures as entry data, have been developed for use with the National Fire-Danger Rating System in Alaska. Comparisons have been made which illustrate differences resulting from danger-rating calculations based on these new fine-fuel moisture content tables for the cured, transition, and green...

Development of a Microcomputer-Based Adaptive Testing System. Phase I. Specification of Requirements and Preliminary Design.

DTIC Science & Technology

1982-06-30

treatments, and cure (or kill ) a patient. Administratively, the items were in a multiple-choice format and the simulation proceeded by branching...Discs: dual 5 1/4 inch floppies (IM) Bus: N/A Operating System: CP/M, MmmOST Price: $3,495 -14 ~-174- - ’i~ Model 820 Xerox 1341 West Mockingbird Lane

Ethical challenges in developing an educational video to empower potential participants during consent processes in HIV cure research in South Africa.

PubMed

Staunton, Ciara; de Roubaix, Malcolm; Baatjies, Dianno; Black, Gill; Hendricks, Melany; Rossouw, Theresa; Moodley, Keymanthri

2018-04-01

Obtaining consent for HIV research is complex, particularly in low- and middle-income countries. Low levels of education, complexity of science and research processes, confusion about basic elements of research, and socio-economic conditions that make access to medical care difficult have collectively led to concerns about the adequacy of the consent process. Given the exponential growth of HIV prevention and treatment research in South Africa, HIV researchers are increasingly facing challenges obtaining authentic informed consent from potential participants. It is anticipated that HIV cure research, despite being in its infancy in South Africa, will introduce a new discourse into a population that is often struggling to understand the differences between 'cure', 'preventive and therapeutic vaccines' and other elements of the research process. Coupled with this, South Africa has a complex history of 'illegitimate' or 'false cures' for HIV. It is therefore logical to anticipate that HIV cure research may face significant challenges during consent processes. HIV prevention research in South Africa has demonstrated the importance of early community engagement in educating potential research participants and promoting community acceptance of research. Consequently, in an attempt to extrapolate from this experience of engaging with communities early regarding cure research, a 15-minute educational video entitled ' I have a dream: a world without HIV ' was developed to educate and ultimately empower potential research participants to make informed choices during consent processes in future HIV cure clinical trials. To aid others in the development of educational interventions, this paper discusses the challenges faced in developing this educational video.

Electron beam curing — taking good ideas to the manufacturing floor

NASA Astrophysics Data System (ADS)

Saunders, C.; Lopata, V.; Barnard, J.; Stepanik, T.

2000-03-01

Acsion is exploiting several emerging electron beam EB applications ranging from composite curing and repair to viscose manufacturing. EB curing of composite structures offers several advantages: significantly reduced curing times; improvements in part quality and performance; reduced environmental and health concerns; improvements in material handling; and reduced overall manufacturing costs compared to thermal curing. The aerospace industry is developing EB technology in all of their market sectors, including military aviation and space products. Some specific products include cryogenic fuel tanks, improved canopy frames for jet aircraft, and the all-composite military aircraft. This paper discusses each of these opportunities.

Nitrite, nitrite alternatives, and the control of Clostridium botulinum in cured meats.

PubMed

Pierson, M D; Smoot, L A

1982-01-01

Historically, nitrite has been a component of meat-curing additives for several centuries. In recent years the safety of nitrite as an additive in cured meats has been questioned mainly because of the possible formation of carcinogenic nitrosamines. Nitrite has many important functions in meat curing including its role in color development, flavor, antioxidant properties, and antimicrobial activity. The inhibition of Clostridium botulinum growth and toxin production is an especially important antimicrobial property of nitrite. This review discusses the effects of processing, curing ingredients (especially nitrite), and storage of cured meats in relation to the control of C. botulinum. If nitrite is eliminated from cured meats or the level of usage decreased, then alternatives for the antibotulinal function of nitrite need to be considered. Several potential alternatives including sorbates, parabens, and biological acidulants are discussed.

Modeling of polymer networks for application to solid propellant formulating

NASA Technical Reports Server (NTRS)

Marsh, H. E.

1979-01-01

Methods for predicting the network structural characteristics formed by the curing of pourable elastomers were presented; as well as the logic which was applied in the development of mathematical models. A universal approach for modeling was developed and verified by comparison with other methods in application to a complex system. Several applications of network models to practical problems are described.

Bisimide amine cured epoxy /IME/ resins and composites. II - Ten-degree off-axis tensile and shear properties of Celion 6000/IME composites

NASA Technical Reports Server (NTRS)

Scola, D. A.

1982-01-01

Bisimide amines (BIAs), which are presently used as curing agents in a state-of-the-art epoxy resin, are oligomeric and polymeric mixtures. A series of composites consisting of the novel BIA-cured epoxy resin reinforced with Celion 6000 graphite fibers were fabricated and evaluated, and the ten-degree, off-axis uniaxial tensile and shear properties of these composites were determined. The use of the intralaminar shear strain-to-failure was used in the calculation of resin shear strain-to-failure. Study results indicate that several of these novel composite systems exhibit shear strain properties that are superior to those of the control composite system of the present experiments, which employed a sulfone curing agent.

New Insights into Structure-Property Relationships in Thermosetting Polymers from Studies of Co-Cured Polycyanurate Networks (Preprint)

DTIC Science & Technology

2011-12-19

have shown through positron annihilation studies that a substantial amount of free volume develops during the final stages of cyanate ester cure...Polymers from 5b. GRANT NUMBER Studies of Co-Cured Polycyanurate Networks (preprint) 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) Andrew J. Guenthner...Macromolecules. 14. ABSTRACT Studies of the physical properties of the co-cured networks formed from three similar dicyanate ester monomers revealed a

Research and Operational Support for the Study of Military Relevant Infectious Diseases of Interest to United States and Royal Thai Government

DTIC Science & Technology

2006-01-01

in progress 8 PvDBP Polymorphisms Study completed; publication in progress 9 Tafenoquine Cure /Radical Cure Dose Ranging NIH In life completed Jan...and II, as possibly phase III testing. We will continue efforts for tafenoquine development, especially towards an indication of radical cure for...disease (prophylaxis) and to cure the infection (therapeutic). Antimalarial drug screening in the rhesus monkey model is very effective for making

Measurement of the degree of cure in epoxies with ultrasonic velocity

NASA Technical Reports Server (NTRS)

Winfree, W. P.; Parker, F. R.

1986-01-01

The use of ultrasonic longitudinal velocity values to measure the degree of cure (defined for an epoxide system as the concentration of epoxide/amine bonds divided by the initial epoxide concentration) in epoxy resins is investigated. The experimental setup used to measure the changes in longitudinal velocity with time is described, together with the technique used to calculate the degree of cure from the acoustic data, using the principle of additive module. Measurements were done with diglycidyl ether of bisphenol A epoxy resin cured with an amine adduct agent. Good qualitative agreement was shown between the time dependence of the acoustically measured degree of cure and the predicted rate of reaction.

Leprosy-associated Chronic Wound Management Using Biomaterials

PubMed Central

Sivasubramanian, Srinivasan; Mohana, Sambasivam; Maheswari, Paulraj; Victoria, Victor; Thangam, Ramar; Mahalingam, Jayashri; Chandrasekar-Janebjer, Gayathri; Savariar, Vincent; Madhan, Balaraman; Gunasekaran, Palani; Kitambi, Satish S

2018-01-01

Background: Deformities and neuropathic chronic ulcers are the common features associated with leprosy-cured individuals that impact their quality of life and impair rehabilitation efforts. The challenging aspects for treatment of chronic wounds are the factors that inhibit healing. We reasoned that limited success of various therapeutic interventions could be due to the fact that leprosy-cured individual's physiology gets acclimatized to having a chronic wound that any therapeutic intervention is counterbalanced to maintain status quo at the wound site. Therefore, an alternative strategy would be to use biomaterials that gradually alter the wound site allowing the individual's physiology to participate in the healing process. Aims: Developing the human amnion (Amn)-derived biomaterial scaffolds and evaluating its use to heal chronic wounds in leprosy-cured but deformed persons (LCDPs). Materials and Methods: Using an enzymatic protocol, we have developed a rapid method to generate biomaterial scaffolds from discarded human Amn. A clinical trial on 26 LCDPs was performed with the biomaterial, and its wound-healing potential was then compared with LCDPs undergoing standard treatment procedure. Results: Biomaterial-based treatment of chronic wounds on LCDP displayed a higher efficiency in healing when compared to standard treatment. Conclusions: This study exemplifies that biomaterial-based treatment of leprosy-wounds offers an excellent affordable alternative for wound management. This study underlines the importance of involving both local wound environment and systemic effects for healing. In addition, we highlight wound healing as a necessity for successful rehabilitation and reintegration of leprosy-cured person into the society. PMID:29910571

Leprosy-associated Chronic Wound Management Using Biomaterials.

PubMed

Sivasubramanian, Srinivasan; Mohana, Sambasivam; Maheswari, Paulraj; Victoria, Victor; Thangam, Ramar; Mahalingam, Jayashri; Chandrasekar-Janebjer, Gayathri; Savariar, Vincent; Madhan, Balaraman; Gunasekaran, Palani; Kitambi, Satish S

2018-01-01

Deformities and neuropathic chronic ulcers are the common features associated with leprosy-cured individuals that impact their quality of life and impair rehabilitation efforts. The challenging aspects for treatment of chronic wounds are the factors that inhibit healing. We reasoned that limited success of various therapeutic interventions could be due to the fact that leprosy-cured individual's physiology gets acclimatized to having a chronic wound that any therapeutic intervention is counterbalanced to maintain status quo at the wound site. Therefore, an alternative strategy would be to use biomaterials that gradually alter the wound site allowing the individual's physiology to participate in the healing process. Developing the human amnion (Amn)-derived biomaterial scaffolds and evaluating its use to heal chronic wounds in leprosy-cured but deformed persons (LCDPs). Using an enzymatic protocol, we have developed a rapid method to generate biomaterial scaffolds from discarded human Amn. A clinical trial on 26 LCDPs was performed with the biomaterial, and its wound-healing potential was then compared with LCDPs undergoing standard treatment procedure. Biomaterial-based treatment of chronic wounds on LCDP displayed a higher efficiency in healing when compared to standard treatment. This study exemplifies that biomaterial-based treatment of leprosy-wounds offers an excellent affordable alternative for wound management. This study underlines the importance of involving both local wound environment and systemic effects for healing. In addition, we highlight wound healing as a necessity for successful rehabilitation and reintegration of leprosy-cured person into the society.

Characterization of the relationship of the cure cycle chemistry to cure cycle processing properties

NASA Technical Reports Server (NTRS)

Kranbuehl, D. E.

1985-01-01

Dynamic dielectric analysis (DDA) is used to study curing polymer systems and thermoplastics. Measurements are made over a frequency range of six decades. This wide range of frequencies increases the amount of information which can be obtained. The data is analyzed in terms of the frequency dependence of the complex permittivity epsilon sup *, specific conductivity sigma (ohm/cm) and the relaxation time tau, parameters which are characteristic of the cure state of the material and independent of the size of the sample.

Highlights from the HIV Cure and Reservoir Symposium, 11-12 September 2017, Ghent, Belgium.

PubMed

Kint, Sam; Van Hecke, Clarissa; Cole, Basiel; Vandekerckhove, Linos; Sips, Magdalena

2018-01-01

For the second time, the HIV Cure Research Center (HCRC) at Ghent University organised the HIV Cure and Reservoir Symposium, in Ghent, Belgium, where in this two-day conference, virologists, molecular biologists, immunologists and clinicians presented the most recent achievements in the field of HIV cure, including data on therapeutic vaccines, HIV remission strategies such as 'shock and kill' or 'block and lock', benefits of early ART and potential of haematopoietic stem cell transplant in achieving cure. Furthermore, methods to characterise and quantify the HIV reservoir were discussed along with HIV reservoir characterisation in different body parts, including the central nervous system. An HIV activist and representative of a patients' agency also presented the patients' perspective on HIV cure. This report is a summary of all topics discussed during this symposium.

Relaxed Poisson cure rate models.

PubMed

Rodrigues, Josemar; Cordeiro, Gauss M; Cancho, Vicente G; Balakrishnan, N

2016-03-01

The purpose of this article is to make the standard promotion cure rate model (Yakovlev and Tsodikov, ) more flexible by assuming that the number of lesions or altered cells after a treatment follows a fractional Poisson distribution (Laskin, ). It is proved that the well-known Mittag-Leffler relaxation function (Berberan-Santos, ) is a simple way to obtain a new cure rate model that is a compromise between the promotion and geometric cure rate models allowing for superdispersion. So, the relaxed cure rate model developed here can be considered as a natural and less restrictive extension of the popular Poisson cure rate model at the cost of an additional parameter, but a competitor to negative-binomial cure rate models (Rodrigues et al., ). Some mathematical properties of a proper relaxed Poisson density are explored. A simulation study and an illustration of the proposed cure rate model from the Bayesian point of view are finally presented. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Concordance measure and discriminatory accuracy in transformation cure models.

PubMed

Zhang, Yilong; Shao, Yongzhao

2018-01-01

Many populations of early-stage cancer patients have non-negligible latent cure fractions that can be modeled using transformation cure models. However, there is a lack of statistical metrics to evaluate prognostic utility of biomarkers in this context due to the challenges associated with unknown cure status and heavy censorship. In this article, we develop general concordance measures as evaluation metrics for the discriminatory accuracy of transformation cure models including the so-called promotion time cure models and mixture cure models. We introduce explicit formulas for the consistent estimates of the concordance measures, and show that their asymptotically normal distributions do not depend on the unknown censoring distribution. The estimates work for both parametric and semiparametric transformation models as well as transformation cure models. Numerical feasibility of the estimates and their robustness to the censoring distributions are illustrated via simulation studies and demonstrated using a melanoma data set. © The Author 2017. Published by Oxford University Press. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

A method for observing gas evolution during plastic laminate cure

NASA Technical Reports Server (NTRS)

Nicholls, A. H.

1969-01-01

Polyimide, phenolic, and other resins which develop volatiles during laminating or molding cure are studied using optimum cure cycles. The specimen is placed on a platen and sealed in a plastic bag, then heated and observed for gas evolution using a binocular microscope. A cover plate is added to sumulate an autoclave.

Ambient curing fire resistant foams

NASA Technical Reports Server (NTRS)

Hamermesh, C. L.; Hogenson, P. A.; Tung, C. Y.; Sawko, P. M.; Riccitiello, S. R.

1979-01-01

The feasibility of development of an ambient curing foam is described. The thermal stability and flame spread index of the foams were found to be comparable to those of the high-temperature cured polyimide foams by Monsanto two-foot tunnel test and NASA T-3 Fire test. Adaptation of the material to spray in place applications is described

Influence of post pattern and resin cement curing mode on the retention of glass fibre posts.

PubMed

Poskus, L T; Sgura, R; Paragó, F E M; Silva, E M; Guimarães, J G A

2010-04-01

To evaluate the influence of post design and roughness and cement system (dual- or self-cured) on the retention of glass fibre posts. Two tapered and smooth posts (Exacto Cônico No. 2 and White Post No. 1) and two parallel-sided and serrated posts (Fibrekor 1.25 mm and Reforpost No. 2) were adhesively luted with two different resin cements--a dual-cured (Rely-X ARC) and a self-cured (Cement Post)--in 40 single-rooted teeth. The teeth were divided into eight experimental groups (n = 5): PFD--Parallel-serrated-Fibrekor/dual-cured; PRD--Parallel-serrated-Reforpost/dual-cured; TED--Tapered-smooth-Exacto Cônico/dual-cured; TWD--Tapered-smooth-White Post/dual-cured; PFS--Parallel-serrated-Fibrekor/self-cured; PRS--Parallel-serrated-Reforpost/self-cured; TES--Tapered-smooth-Exacto Cônico/self-cured; TWS--Tapered-smooth-White Post/self-cured. The specimens were submitted to a pull-out test at a crosshead speed of 0.5 mm min(-1). Data were analysed using analysis of variance and Bonferroni's multiple comparison test (alpha = 0.05). Pull-out results (MPa) were: PFD = 8.13 (+/-1.71); PRD = 8.30 (+/-0.46); TED = 8.68 (+/-1.71); TWD = 9.35 (+/-1.99); PFS = 8.54 (+/-2.23); PRS = 7.09 (+/-1.96); TES = 8.27 (+/-3.92); TWS = 7.57 (+/-2.35). No statistical significant difference was detected for posts and cement factors and their interaction. The retention of glass fibre posts was not affected by post design or surface roughness nor by resin cement-curing mode. These results imply that the choice for serrated posts and self-cured cements is not related to an improvement in retention.

In-situ Frequency Dependent Dielectric Sensing of Cure

NASA Technical Reports Server (NTRS)

Kranbuehl, David E.

1996-01-01

With the expanding use of polymeric materials as composite matrices, adhesives, coatings and films, the need to develop low cost, automated fabrication processes to produce consistently high quality parts is critical. Essential to the development of reliable, automated, intelligent processing is the ability to continuously monitor the changing state of the polymeric resin in-situ in the fabrication tool. This final report discusses work done on developing dielectric sensing to monitor polymeric material cure and which provides a fundamental understanding of the underlying science for the use of frequency dependent dielectri sensors to monitor the cure process.

ON THE DEGREE OF CONVERSION AND COEFFICIENT OF THERMAL EXPANSION OF A SINGLE FIBER COMPOSITE USING A FBG SENSOR

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

Lai, M.; Botsis, J.; Coric, D.

2008-08-28

The increasing needs of extending the lifetime in high-technology fields, such as space and aerospace, rail transport and naval systems, require quality enhancing of the composite materials either from a processing standing point or in the sense of resistance to service conditions. It is well accepted that the final quality of composite materials and structures is strongly influenced by processing parameters like curing and post-curing temperatures, rate of heating and cooling, applied vacuum, etc. To optimize manufacturing cycles, residual strains evolution due to chemical shrinkage and other physical parameters of the constituent materials must be characterized in situ. Such knowledgemore » can lead to a sensible reduction in defects and to improved physical and mechanical properties of final products. In this context continuous monitoring of strains distribution developed during processing is important in understanding and retrieving components' and materials' characteristics such as local strains gradients, degree of curing, coefficient of thermal expansion, moisture absorption, etc.« less

Eradication of HIV from Tissue Reservoirs: Challenges for the Cure.

PubMed

Rose, Rebecca; Nolan, David J; Maidji, Ekaterina; Stoddart, Cheryl A; Singer, Elyse J; Lamers, Susanna L; McGrath, Michael S

2018-01-01

The persistence of HIV infection, even after lengthy and successful combined antiretroviral therapy (cART), has precluded an effective cure. The anatomical locations and biological mechanisms through which the viral population is maintained remain unknown. Much research has focused nearly exclusively on circulating resting T cells as the predominant source of persistent HIV, a strategy with limited success in developing an effective cure strategy. In this study, we review research supporting the importance of anatomical tissues and other immune cells for HIV maintenance and expansion, including the central nervous system, lymph nodes, and macrophages. We present accumulated research that clearly demonstrates the limitations of using blood-derived cells as a proxy for tissue reservoirs and sanctuaries throughout the body. We cite recent studies that have successfully used deep-sequencing strategies to uncover the complexity of HIV infection and the ability of the virus to evolve despite undetectable plasma viral loads. Finally, we suggest new strategies and highlight the importance of tissue banks for future research.

Development of an embedded thin-film strain-gauge-based SHM network into 3D-woven composite structure for wind turbine blades

NASA Astrophysics Data System (ADS)

Zhao, Dongning; Rasool, Shafqat; Forde, Micheal; Weafer, Bryan; Archer, Edward; McIlhagger, Alistair; McLaughlin, James

2017-04-01

Recently, there has been increasing demand in developing low-cost, effective structure health monitoring system to be embedded into 3D-woven composite wind turbine blades to determine structural integrity and presence of defects. With measuring the strain and temperature inside composites at both in-situ blade resin curing and in-service stages, we are developing a novel scheme to embed a resistive-strain-based thin-metal-film sensory into the blade spar-cap that is made of composite laminates to determine structural integrity and presence of defects. Thus, with fiberglass, epoxy, and a thinmetal- film sensing element, a three-part, low-cost, smart composite laminate is developed. Embedded strain sensory inside composite laminate prototype survived after laminate curing process. The internal strain reading from embedded strain sensor under three-point-bending test standard is comparable. It proves that our proposed method will provide another SHM alternative to reduce sensing costs during the renewable green energy generation.

A thermo-chemo-mechanically coupled constitutive model for curing of glassy polymers

NASA Astrophysics Data System (ADS)

Sain, Trisha; Loeffel, Kaspar; Chester, Shawn

2018-07-01

Curing of a polymer is the process through which a polymer liquid transitions into a solid polymer, capable of bearing mechanical loads. The curing process is a coupled thermo-chemo-mechanical conversion process which requires a thorough understanding of the system behavior to predict the cure dependent mechanical behavior of the solid polymer. In this paper, a thermodynamically consistent, frame indifferent, thermo-chemo-mechanically coupled continuum level constitutive framework is proposed for thermally cured glassy polymers. The constitutive framework considers the thermodynamics of chemical reactions, as well as the material behavior for a glassy polymer. A stress-free intermediate configuration is introduced within a finite deformation setting to capture the formation of the network in a stress-free configuration. This work considers a definition for the degree of cure based on the chemistry of the curing reactions. A simplified version of the proposed model has been numerically implemented, and simulations are used to understand the capabilities of the model and framework.

Shear bond strength of a bracket-bonding system cured with a light-emitting diode or halogen-based light-curing unit at various polymerization times

PubMed Central

Gupta, Sanjay Prasad; Shrestha, Basanta Kumar

2018-01-01

Purpose To determine and compare the shear bond strength (SBS) of bracket-bonding system cured with light-emitting diode (LED) and halogen-based light-curing unit at various polymerization times. Materials and methods Ninety six human maxillary premolar teeth extracted for orthodontic purpose were divided into four groups, according to the light-curing unit and exposure times used. In the halogen group, the specimens were light cured for 20 and 40 seconds. In the LED group, the specimens were light cured for 5 and 10 seconds. Stainless steel brackets were bonded with Enlight bonding system, stored in distilled water at 37°C for 24 hours and then submitted to SBS testing in a universal testing machine at a crosshead speed of 0.5 mm/minute. Adhesive remnant index (ARI) was used to evaluate the amount of adhesive remaining on the teeth determined by stereomicroscope at 10× magnification. Results The highest mean SBS was obtained with the halogen 40 seconds (18.27 MPa) followed by halogen 20 seconds (15.36 MPa), LED 10 seconds (14.60 MPa) and least with LED 5 seconds (12.49 MPa) group. According to analysis of variance (ANOVA) and Tukey’s multiple-comparison test, SBS of halogen 20 seconds group was not significantly different from halogen 40 seconds group, LED 5 seconds group and LED 10 seconds group, whereas halogen 40 seconds group was significantly different from LED 5 seconds and LED 10 seconds group. The method of light curing did not influence the ARI, with score 2 being predominant. Conclusion Polymerization with both halogen and LED resulted in SBS values that were clinically acceptable for orthodontic treatment in all groups. Hence, for bonding orthodontic brackets, photoactivation with halogen for 20 seconds and LED for 5 seconds is suggested. PMID:29692633

Effect of different photoinitiators and reducing agents on cure efficiency and color stability of resin-based composites using different LED wavelengths.

PubMed

de Oliveira, Dayane Carvalho Ramos Salles; Rocha, Mateus Garcia; Gatti, Alexandre; Correr, Americo Bortolazzo; Ferracane, Jack Liborio; Sinhoret, Mario Alexandre Coelho

2015-12-01

To evaluate the effect of photoinitiators and reducing agents on cure efficiency and color stability of resin-based composites using different LED wavelengths. Model resin-based composites were associated with diphenyl(2,4,6-trimethylbenzoyl) phosphine oxide (TPO), phenylbis(2,4,6-trimethylbenzoyl) phosphine oxide (BAPO) or camphorquinone (CQ) associated with 2-(dimethylamino) ethyl methacrylate (DMAEMA), ethyl 4-(dimethyamino) benzoate (EDMAB) or 4-(N,N-dimethylamino) phenethyl alcohol (DMPOH). A narrow (Smartlite, Dentisply) and a broad spectrum (Bluephase G2, Ivoclar Vivadent) LEDs were used for photo-activation (20 J/cm(2)). Fourier transform infrared spectroscopy (FT-IR) was used to evaluate the cure efficiency for each composite, and CIELab parameters to evaluated color stability (ΔE00) after aging. The UV-vis absorption spectrophotometric analysis of each photoinitiator and reducing agent was determined. Data were analyzed using two-way ANOVA and Tukey's test for multiple comparisons (α=0.05). Higher cure efficiency was found for type-I photoinitiators photo-activated with a broad spectrum light, and for CQ-systems with a narrow band spectrum light, except when combined with an aliphatic amine (DMAEMA). Also, when combined with aromatic amines (EDMAB and DMPOH), similar cure efficiency with both wavelength LEDs was found. TPO had no cure efficiency when light-cured exclusively with a blue narrowband spectrum. CQ-systems presented higher color stability than type-I photoinitiators, especially when combined with DMPOH. After aging, CQ-based composites became more yellow and BAPO and TPO lighter and less yellow. However, CQ-systems presented higher color stability than type-I photoinitiators, as BAPO- and TPO-, despite their higher cure efficiency when photo-activated with corresponding wavelength range. Color matching is initially important, but color change over time will be one of the major reasons for replacing esthetic restorations; despite the less yellowing of these alternative photoinitiators, camphorquinone presented higher color stability. Copyright © 2015 Elsevier Ltd. All rights reserved.

Investor Outlook: Solving Gene Therapy Pricing…with a Cures Voucher?

PubMed

Schimmer, Joshua; Breazzano, Steven

2016-12-01

Gene therapy reimbursement continues to be an intense topic of discussion in the field given the unique and durable benefits from a single administration and generally small patient populations against a reimbursement framework that is not optimized for such "cures" or long-lived benefits. As more gene therapy programs enter the market and late-stage development, it is increasingly important for the field to define a reimbursement model that works for all stakeholders in order to encourage the next wave of innovation. To add to the discussion around new payment models and potential solutions, we propose a flexible voucher system that takes advantage of existing infrastructure, precedent, and regulatory frameworks.

Approaches to Polymer Curing and Imaging Via the In Situ Generation of a Catalyst

DTIC Science & Technology

1992-04-20

polyimide can be formulated from a polyamic acid derivative and a photo- precursor of base. Of particular interest are systems that incorporate chemical...amplification. In these systems the initial radiation induced proc- ess, photogeneration of the acid or base catalyst within the polymer film, is...different, new systems better suited for the high demands of modem microlithography have been developed. Issues of particular relevance in the design of

Thermal protection system repair kit program

NASA Technical Reports Server (NTRS)

1979-01-01

The feasibility and conceptual design aspects of repair materials and procedures for in orbit repair of the space shuttle orbiter TPS tiles are investigated. Material studies to investigate cure in place materials are described including catalyst and cure studies, ablation tests and evaluations, and support mixing and applicator design. The feasibility of the repair procedures, the storage of the TPS, dispensing, and cure problems are addressed.

40 CFR 63.4964 - How do I determine the emission capture system efficiency?

Code of Federal Regulations, 2010 CFR

2010-07-01

... operation are applied within the capture system; coating solvent flash-off and coating, curing, and drying... parts enter the open shop environment when being moved between a spray booth and a curing oven. (b... from the beginning to the end of production, which includes surface preparation activities and drying...

Method for applying photographic resists to otherwise incompatible substrates

NASA Technical Reports Server (NTRS)

Fuhr, W. (Inventor)

1981-01-01

A method for applying photographic resists to otherwise incompatible substrates, such as a baking enamel paint surface, is described wherein the uncured enamel paint surface is coated with a non-curing lacquer which is, in turn, coated with a partially cured lacquer. The non-curing lacquer adheres to the enamel and a photo resist material satisfactorily adheres to the partially cured lacquer. Once normal photo etching techniques are employed the lacquer coats can be easily removed from the enamel leaving the photo etched image. In the case of edge lighted instrument panels, a coat of uncured enamel is placed over the cured enamel followed by the lacquer coats and the photo resists which is exposed and developed. Once the etched uncured enamel is cured, the lacquer coats are removed leaving an etched panel.

Recent developments in the search for a cure for HIV-1 infection: targeting the latent reservoir for HIV-1.

PubMed

Siliciano, Janet D; Siliciano, Robert F

2014-07-01

HIV-1 infection can now be readily controlled with combination antiretroviral therapy. However, the virus persists indefinitely in a stable latent reservoir in resting CD4(+) T cells. This reservoir generally prevents cure of the infection with combination antiretroviral therapy alone. However, several recent cases of potential HIV-1 cure have generated renewed optimism. Here we review these cases and consider new developments in our understanding of the latent reservoir. In addition, we consider clinical aspects of curative strategies to provide a more realistic picture of what a generally applicable cure for HIV-1 infection is likely to entail. Copyright © 2014 American Academy of Allergy, Asthma & Immunology. Published by Mosby, Inc. All rights reserved.

Scalable and continuous fabrication of bio-inspired dry adhesives with a thermosetting polymer.

PubMed

Lee, Sung Ho; Kim, Sung Woo; Kang, Bong Su; Chang, Pahn-Shick; Kwak, Moon Kyu

2018-04-04

Many research groups have developed unique micro/nano-structured dry adhesives by mimicking the foot of the gecko with the use of molding methods. Through these previous works, polydimethylsiloxane (PDMS) has been developed and become the most commonly used material for making artificial dry adhesives. The material properties of PDMS are well suited for making dry adhesives, such as conformal contacts with almost zero preload, low elastic moduli for stickiness, and easy cleaning with low surface energy. From a performance point of view, dry adhesives made with PDMS can be highly advantageous but are limited by its low productivity, as production takes an average of approximately two hours. Given the low productivity of PDMS, some research groups have developed dry adhesives using UV-curable materials, which are capable of continuous roll-to-roll production processes. However, UV-curable materials were too rigid to produce good adhesion. Thus, we established a PDMS continuous-production system to achieve good productivity and adhesion performance. We designed a thermal roll-imprinting lithography (TRL) system for the continuous production of PDMS microstructures by shortening the curing time by controlling the curing temperature (the production speed is up to 150 mm min-1). Dry adhesives composed of PDMS were fabricated continuously via the TRL system.

78 FR 29755 - Human Immunodeficiency Virus Patient-Focused Drug Development and Human Immunodeficiency Virus...

Federal Register 2010, 2011, 2012, 2013, 2014

2013-05-21

... research study, and why? (Examples of risks that may be associated with participation in an HIV cure... Research: Public Meeting AGENCY: Food and Drug Administration, HHS. ACTION: Notice of public meeting... Development and HIV Cure Research. Patient-Focused Drug Development is part of FDA's performance commitments...

Interfacial adhesion improvement in carbon fiber/carbon nanotube reinforced hybrid composites by the application of a reactive hybrid resin initiated by gamma irradiation

NASA Astrophysics Data System (ADS)

Szebényi, G.; Faragó, D.; Lámfalusi, Cs.; Göbl, R.

2018-04-01

Interfacial adhesion is a key factor in composite materials. The effective co-working of the reinforcing materials and matrix is essential for the proper load transfer between them, and to achieve the desired reinforcing effect. In case of nanocomposites, especially carbon nanotube (CNT) reinforced nanocomposites the adhesion between the CNTs and the polymer matrix is poor. To improve the interfacial adhesion and exploit the reinforcing effect of these nanoparticles a two step curable epoxy (EP)/vinylester (VE) hybrid resin system was developed where the EP is cured using hardener in the first step, during the composite production, and in the second step the curing of the VE is initiated by gamma irradiation, which also activates the reinforcing materials and the cured matrix component. A total of six carbon fiber reinforced composite systems were compared with neat epoxy and EP/VE hybrid matrices with and without chemical initiator and MWCNT nano-reinforcement. The effect of gamma irradiation was investigated at four absorbed dose levels. According to our three point bending and interlaminar shear test results the adhesion has improved between all constituents of the composite system. It was demonstrated that gamma irradiation has beneficial effect on the static mechanical, especially interlaminar properties of both micro- and nanocomposites in terms of modulus, strength and interlaminar shear strength.

Method for curing polymers using variable-frequency microwave heating

DOEpatents

Lauf, R.J.; Bible, D.W.; Paulauskas, F.L.

1998-02-24

A method for curing polymers incorporating a variable frequency microwave furnace system designed to allow modulation of the frequency of the microwaves introduced into a furnace cavity is disclosed. By varying the frequency of the microwave signal, non-uniformities within the cavity are minimized, thereby achieving a more uniform cure throughout the workpiece. A directional coupler is provided for detecting the direction of a signal and further directing the signal depending on the detected direction. A first power meter is provided for measuring the power delivered to the microwave furnace. A second power meter detects the magnitude of reflected power. The furnace cavity may be adapted to be used to cure materials defining a continuous sheet or which require compressive forces during curing. 15 figs.

22 CFR 204.22 - Right of A.I.D. to cure default.

Code of Federal Regulations, 2011 CFR

2011-04-01

... 22 Foreign Relations 1 2011-04-01 2011-04-01 false Right of A.I.D. to cure default. 204.22 Section 204.22 Foreign Relations AGENCY FOR INTERNATIONAL DEVELOPMENT HOUSING GUARANTY STANDARD TERMS AND CONDITIONS Procedure for Obtaining Compensation § 204.22 Right of A.I.D. to cure default. Within sixty (60...

22 CFR 204.22 - Right of A.I.D. to cure default.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 22 Foreign Relations 1 2010-04-01 2010-04-01 false Right of A.I.D. to cure default. 204.22 Section 204.22 Foreign Relations AGENCY FOR INTERNATIONAL DEVELOPMENT HOUSING GUARANTY STANDARD TERMS AND CONDITIONS Procedure for Obtaining Compensation § 204.22 Right of A.I.D. to cure default. Within sixty (60...

22 CFR 204.22 - Right of A.I.D. to cure default.

Code of Federal Regulations, 2014 CFR

2014-04-01

... 22 Foreign Relations 1 2014-04-01 2014-04-01 false Right of A.I.D. to cure default. 204.22 Section 204.22 Foreign Relations AGENCY FOR INTERNATIONAL DEVELOPMENT HOUSING GUARANTY STANDARD TERMS AND CONDITIONS Procedure for Obtaining Compensation § 204.22 Right of A.I.D. to cure default. Within sixty (60...

22 CFR 204.22 - Right of A.I.D. to cure default.

Code of Federal Regulations, 2013 CFR

2013-04-01

... 22 Foreign Relations 1 2013-04-01 2013-04-01 false Right of A.I.D. to cure default. 204.22 Section 204.22 Foreign Relations AGENCY FOR INTERNATIONAL DEVELOPMENT HOUSING GUARANTY STANDARD TERMS AND CONDITIONS Procedure for Obtaining Compensation § 204.22 Right of A.I.D. to cure default. Within sixty (60...

22 CFR 204.22 - Right of A.I.D. to cure default.

Code of Federal Regulations, 2012 CFR

2012-04-01

... 22 Foreign Relations 1 2012-04-01 2012-04-01 false Right of A.I.D. to cure default. 204.22 Section 204.22 Foreign Relations AGENCY FOR INTERNATIONAL DEVELOPMENT HOUSING GUARANTY STANDARD TERMS AND CONDITIONS Procedure for Obtaining Compensation § 204.22 Right of A.I.D. to cure default. Within sixty (60...

Curing system for high voltage cross linked cables

DOEpatents

Bahder, George; Katz, Carlos; Bopp, Louis A.

1978-01-01

This invention makes extruded, vulcanized, high voltage cables insulated with thermosetting compounds at much higher rates of production and with superior insulation of reduced thickness and with reduced cavities or voids in the insulation. As the cable comes from an extruder, it passes into a curing chamber with a heat booster that quickly raises the insulation to a temperature at which it is cured much more quickly than with steam heating of the prior art. A high temperature liquid in contact with the insulation maintains the high temperature; and because of the greater curing heat, the cable can travel through the curing chamber at a faster rate and into a cooling tube where it contacts with a cooling liquid under high pressure. The insulation compound is treated to reduce the size of cavities; and the high pressure maintained by the curing and cooling mediums prevent expansion of cavities before the insulation is set.

Cure Chemistry of Phenylethynyl Terminated Oligomers

NASA Technical Reports Server (NTRS)

Wood, Karen H.; Orwoll, Robert A.; Young, Philip R.; Jensen, Brian J.; McNair, Harold M.

1997-01-01

The ability to process high performance polymers into quality, void-free composites has been significantly advanced using oligomers terminated with reactive groups which cure or crosslink at elevated temperature without the evolution of volatile byproducts. Several matrix resin systems of considerable interest to the aerospace community utilize phenylethynyl-terminated imide (PETI) technology to achieve this advantage. The present paper addresses the cure chemistry of PETI oligomers. The thermal cure of a low molecular weight model compound was studied using a variety of analytical techniques including differential scanning calorimetry, Fourier transform infrared spectroscopy, and liquid chromatography-mass spectroscopy. The studies indicate an extremely complex cure process. Many stable products were isolated and this paper reports current work on identification of those products. The intent of this research is to provide fundamental insight into the molecular structure of the cured PETI engineering materials so that performance and durability can be more fully assessed.

A Call to Develop Course-Based Undergraduate Research Experiences (CUREs) for Nonmajors Courses.

PubMed

Ballen, Cissy J; Blum, Jessamina E; Brownell, Sara; Hebert, Sadie; Hewlett, James; Klein, Joanna R; McDonald, Erik A; Monti, Denise L; Nold, Stephen C; Slemmons, Krista E; Soneral, Paula A G; Cotner, Sehoya

2017-01-01

Course-based undergraduate research experiences (CUREs) for non-science majors (nonmajors) are potentially distinct from CUREs for developing scientists in their goals, learning objectives, and assessment strategies. While national calls to improve science, technology, engineering, and mathematics education have led to an increase in research revealing the positive effects of CUREs for science majors, less work has specifically examined whether nonmajors are impacted in the same way. To address this gap in our understanding, a working group focused on nonmajors CUREs was convened to discuss the following questions: 1) What are our laboratory-learning goals for nonmajors? 2) What are our research priorities to determine best practices for nonmajors CUREs? 3) How can we collaborate to define and disseminate best practices for nonmajors in CUREs? We defined three broad student outcomes of prime importance to the nonmajors CURE: improvement of scientific literacy skills, proscience attitudes, and evidence-based decision making. We evaluated the state of knowledge of best practices for nonmajors, and identified research priorities for the future. The report that follows is a summary of the conclusions and future directions from our discussion. © 2017 C. J. Ballen et al. CBE—Life Sciences Education © 2017 The American Society for Cell Biology. This article is distributed by The American Society for Cell Biology under license from the author(s). It is available to the public under an Attribution–Noncommercial–Share Alike 3.0 Unported Creative Commons License (http://creativecommons.org/licenses/by-nc-sa/3.0).

Induction Curing of Thiol-acrylate and Thiolene Composite Systems

PubMed Central

Ye, Sheng; Cramer, Neil B.; Stevens, Blake E.; Sani, Robert L.; Bowman, Christopher N.

2011-01-01

Induction curing is demonstrated as a novel type of in situ radiation curing that maintains most of the advantages of photocuring while eliminating the restriction of light accessibility. Induction curing is utilized to polymerize opaque composites comprised of thiol-acrylate and thiol-ene resins, nanoscale magnetic particles, and carbon nanotubes. Nanoscale magnetic particles are dispersed in the resin and upon exposure to the magnetic field, these particles lead to induction heating that rapidly initiates the polymerization. Heat transfer profiles and reaction kinetics of the samples are modeled during the reactions with varying induction heater power, species concentration, species type and sample thickness, and the model is compared with the experimental results. Thiol-ene polymerizations achieved full conversion between 1.5 minutes and 1 hour, depending on the field intensity and the composition, with the maximum reaction temperature decreasing from 146 – 87 °C when the induction heater power was decreased from 8 – 3 kW. The polymerization reactions of the thiol-acrylate system were demonstrated to achieve full conversion between 0.6 and 30 minutes with maximum temperatures from 139 to 86 °C. The experimental behavior was characterized and the temperature profile modeled for the thiol-acrylate composite comprised of sub100nm nickel particles and induction heater power in the range of 32 to 20 kW. A 9°C average deviation was observed between the modeling and experimental results for the maximum temperature rise. The model also was utilized to predict reaction temperatures and kinetics for systems with varying thermal initiator concentration, initiator half-life, monomer molecular weight and temperature gradients in samples with varying thickness, thereby demonstrating that induction curing represents a designable and tunable polymerization method. Finally, induction curing was utilized to cure thiol-acrylate systems containing carbon nanotubes where 1 wt% carbon nanotubes resulted in systems where the storage modulus increased from 17.6 ± 0.2 to 21.6 ± 0.1 MPa and an electrical conductivity that increased from <10−7 to 0.33 ± 0.5 S/m. PMID:21765552

Insight into HIV-2 latency may disclose strategies for a cure for HIV-1 infection.

PubMed

Saleh, Suha; Vranckx, Lenard; Gijsbers, Rik; Christ, Frauke; Debyser, Zeger

2017-01-01

HIV-1 and HIV-2 originate from two distinct zoonotic transmissions of simian immunodeficiency viruses from primate to human. Although both share similar modes of transmission and can result in the development of AIDS with similar clinical manifestations, HIV-2 infection is generally milder and less likely to progress to AIDS. HIV is currently incurable due to the presence of HIV provirus integrated into the host DNA of long-lived memory cells of the immune system without active replication. As such, the latent virus is immunologically inert and remains insensitive to the administered antiviral drugs targeting active viral replication steps. Recent evidence suggests that persistent HIV replication may occur in anatomical sanctuaries such as the lymphoid tissue due to low drug penetration. At present, different strategies are being evaluated either to completely eradicate the virus from the patient (sterilising cure) or to allow treatment interruption without viral rebound (functional cure). Because HIV-2 is naturally less pathogenic and displays a more latent phenotype than HIV-1, it may represent a valuable model that provides elementary information to cure HIV-1 infection. Insight into the viral and cellular determinants of HIV-2 replication may therefore pave the way for alternative strategies to eradicate HIV-1 or promote viral remission.

Co-Curing of CFRP-Steel Hybrid Joints Using the Vacuum Assisted Resin Infusion Process

NASA Astrophysics Data System (ADS)

Streitferdt, Alexander; Rudolph, Natalie; Taha, Iman

2017-10-01

This study focuses on the one-step co-curing process of carbon fiber reinforced plastics (CFRP) joined with a steel plate to form a hybrid structure. In this process CFRP laminate and bond to the metal are realized simultaneously by resin infusion, such that the same resin serves for both infusion and adhesion. For comparison, the commonly applied two-step process of adhesive bonding is studied. In this case, the CFRP laminate is fabricated in a first stage through resin infusion of Non Crimp Fabric (NCF) and joined to the steel plate in a further step through adhesive bonding. For this purpose, the commercially available epoxy-based Betamate 1620 is applied. CFRP laminates were fabricated using two different resin systems, namely the epoxy (EP)-based RTM6 and a newly developed fast curing polyurethane (PU) resin. Results show comparable mechanical performance of the PU and EP based CFRP laminates. The strength of the bond of the co-cured samples was in the same order as the samples adhesively bonded with the PU resin and the structural adhesive. The assembly adhesive with higher ductility showed a weaker performance compared to the other tests. It could be shown that the surface roughness had the highest impact on the joint performance under the investigated conditions.

Low-temperature technique for thick film resist stabilization and curing

NASA Astrophysics Data System (ADS)

Minter, Jason P.; Wong, Selmer S.; Marlowe, Trey; Ross, Matthew F.; Narcy, Mark E.; Livesay, William R.

1999-06-01

For a range of thick film photoresist applications, including MeV ion implant processing, thin film head manufacturing, and microelectromechanical systems processing, there is a need for a low-temperature method for resist stabilization and curing. Traditional methods of stabilizing or curing resist films have relied on thermal cycling, which may not be desirable due to device temperature limitations or thermally-induced distortion of the resist features.

Development of a fast curing tissue adhesive for meniscus tear repair.

PubMed

Bochyńska, Agnieszka Izabela; Hannink, Gerjon; Janssen, Dennis; Buma, Pieter; Grijpma, Dirk W

2017-01-01

Isocyanate-terminated adhesive amphiphilic block copolymers are attractive materials to treat meniscus tears due to their tuneable mechanical properties and good adhesive characteristics. However, a drawback of this class of materials is their relatively long curing time. In this study, we evaluate the use of an amine cross-linker and addition of catalysts as two strategies to accelerate the curing rates of a recently developed biodegradable reactive isocyanate-terminated hyper-branched adhesive block copolymer prepared from polyethylene glycol (PEG), trimethylene carbonate, citric acid and hexamethylene diisocyanate. The curing kinetics of the hyper-branched adhesive alone and in combination with different concentrations of spermidine solutions, and after addition of 2,2-dimorpholinodiethylether (DMDEE) or 1,4-diazabicyclo [2.2.2] octane (DABCO) were determined using FTIR. Additionally, lap-shear adhesion tests using all compositions at various time points were performed. The two most promising compositions of the fast curing adhesives were evaluated in a meniscus bucket handle lesion model and their performance was compared with that of fibrin glue. The results showed that addition of both spermidine and catalysts to the adhesive copolymer can accelerate the curing rate and that firm adhesion can already be achieved after 2 h. The adhesive strength to meniscus tissue of 3.2-3.7 N was considerably higher for the newly developed compositions than for fibrin glue (0.3 N). The proposed combination of an adhesive component and a cross-linking component or catalyst is a promising way to accelerate curing rates of isocyanate-terminated tissue adhesives.

Healing efficiency and dynamic mechanical properties of self-healing epoxy systems

NASA Astrophysics Data System (ADS)

Guadagno, Liberata; Raimondo, Marialuigia; Naddeo, Carlo; Longo, Pasquale; Mariconda, Annaluisa; Binder, Wolfgang H.

2014-03-01

Several systems to develop self-repairing epoxy resins have recently been formulated. In this paper the effect of matrix nature and curing cycle on the healing efficiency and dynamic mechanical properties of self-healing epoxy resins were investigated. We discuss several aspects by transferring self-healing systems from the laboratory scale to real applications in the aeronautic field, such as the possibility to choose systems with increased glass transition temperature, high storage modulus and high values in the healing functionality under real working conditions.

Cure Cycle Design Methodology for Fabricating Reactive Resin Matrix Fiber Reinforced Composites: A Protocol for Producing Void-free Quality Laminates

NASA Technical Reports Server (NTRS)

Hou, Tan-Hung

2014-01-01

For the fabrication of resin matrix fiber reinforced composite laminates, a workable cure cycle (i.e., temperature and pressure profiles as a function of processing time) is needed and is critical for achieving void-free laminate consolidation. Design of such a cure cycle is not trivial, especially when dealing with reactive matrix resins. An empirical "trial and error" approach has been used as common practice in the composite industry. Such an approach is not only costly, but also ineffective at establishing the optimal processing conditions for a specific resin/fiber composite system. In this report, a rational "processing science" based approach is established, and a universal cure cycle design protocol is proposed. Following this protocol, a workable and optimal cure cycle can be readily and rationally designed for most reactive resin systems in a cost effective way. This design protocol has been validated through experimental studies of several reactive polyimide composites for a wide spectrum of usage that has been documented in the previous publications.

Can hepatic resection provide a long-term cure for patients with intrahepatic cholangiocarcinoma?

PubMed

Spolverato, Gaya; Vitale, Alessandro; Cucchetti, Alessandro; Popescu, Irinel; Marques, Hugo P; Aldrighetti, Luca; Gamblin, T Clark; Maithel, Shishir K; Sandroussi, Charbel; Bauer, Todd W; Shen, Feng; Poultsides, George A; Marsh, J Wallis; Pawlik, Timothy M

2015-11-15

A patient can be considered statistically cured from a specific disease when their mortality rate returns to the same level as that of the general population. In the current study, the authors sought to assess the probability of being statistically cured from intrahepatic cholangiocarcinoma (ICC) by hepatic resection. A total of 584 patients who underwent surgery with curative intent for ICC between 1990 and 2013 at 1 of 12 participating institutions were identified. A nonmixture cure model was adopted to compare mortality after hepatic resection with the mortality expected for the general population matched by sex and age. The median, 1-year, 3-year, and 5-year disease-free survival was 10 months, 44%, 18%, and 11%, respectively; the corresponding overall survival was 27 months, 75%, 37%, and 22%, respectively. The probability of being cured of ICC was 9.7% (95% confidence interval, 6.1%-13.4%). The mortality of patients undergoing surgery for ICC was higher than that of the general population until year 10, at which time patients alive without tumor recurrence can be considered cured with 99% certainty. Multivariate analysis demonstrated that cure probabilities ranged from 25.8% (time to cure, 9.8 years) in patients with a single, well-differentiated ICC measuring ≤5 cm that was without vascular/periductal invasion and lymph nodes metastases versus <0.1% (time to cure, 12.6 years) among patients with all 6 of these risk factors. A model with which to calculate cure fraction and time to cure was developed. The cure model indicated that statistical cure was possible in patients undergoing hepatic resection for ICC. The overall probability of cure was approximately 10% and varied based on several tumor-specific factors. Cancer 2015;121:3998-4006. © 2015 American Cancer Society. © 2015 American Cancer Society.

Prediction of ultrasonic pulse velocity for enhanced peat bricks using adaptive neuro-fuzzy methodology.

PubMed

Motamedi, Shervin; Roy, Chandrabhushan; Shamshirband, Shahaboddin; Hashim, Roslan; Petković, Dalibor; Song, Ki-Il

2015-08-01

Ultrasonic pulse velocity is affected by defects in material structure. This study applied soft computing techniques to predict the ultrasonic pulse velocity for various peats and cement content mixtures for several curing periods. First, this investigation constructed a process to simulate the ultrasonic pulse velocity with adaptive neuro-fuzzy inference system. Then, an ANFIS network with neurons was developed. The input and output layers consisted of four and one neurons, respectively. The four inputs were cement, peat, sand content (%) and curing period (days). The simulation results showed efficient performance of the proposed system. The ANFIS and experimental results were compared through the coefficient of determination and root-mean-square error. In conclusion, use of ANFIS network enhances prediction and generation of strength. The simulation results confirmed the effectiveness of the suggested strategies. Copyright © 2015 Elsevier B.V. All rights reserved.

40 CFR 63.4565 - How do I determine the emission capture system efficiency?

Code of Federal Regulations, 2010 CFR

2010-07-01

... solvent flash-off, curing, and drying occurs within the capture system; and the removal or evaporation of..., this criterion is not met if parts enter the open shop environment when being moved between a spray... surface preparation activities and drying and curing time. (c) Liquid-to-uncaptured-gas protocol using a...

40 CFR 63.4765 - How do I determine the emission capture system efficiency?

Code of Federal Regulations, 2010 CFR

2010-07-01

... coating, curing, and drying occurs within the capture system; and the removal or evaporation of cleaning... criterion is not met if parts enter the open shop environment when being moved between a spray booth and a... activities and drying or curing time. (c) Liquid-to-uncaptured-gas protocol using a temporary total enclosure...

Effects of a low-shrinkage methacrylate monomer and monoacylphosphine oxide photoinitiator on curing efficiency and mechanical properties of experimental resin-based composites.

PubMed

Manojlovic, Dragica; Dramićanin, Miroslav D; Milosevic, Milos; Zeković, Ivana; Cvijović-Alagić, Ivana; Mitrovic, Nenad; Miletic, Vesna

2016-01-01

This study investigated the degree of conversion, depth of cure, Vickers hardness, flexural strength, flexural modulus and volumetric shrinkage of experimental composite containing a low shrinkage monomer FIT-852 (FIT; Esstech Inc.) and photoinitiator 2,4,6-trimethylbenzoyldiphenylphosphine oxide (TPO; Sigma Aldrich) compared to conventional composite containing Bisphenol A-glycidyl methacrylate (BisGMA) and camphorquinone-amine photoinitiator system. The degree of conversion was generally higher in FIT-based composites (45-64% range) than in BisGMA-based composites (34-58% range). Vickers hardness, flexural strength and modulus were higher in BisGMA-based composites. A polywave light-curing unit was generally more efficient in terms of conversion and hardness of experimental composites than a monowave unit. FIT-based composite containing TPO showed the depth of cure below 2mm irrespective of the curing light. The depth of cure of FIT-based composite containing CQ and BisGMA-based composites with either photoinitiator was in the range of 2.8-3.0mm. Volumetric shrinkage of FIT-based composite (0.9-5.7% range) was lower than that of BisGMA-based composite (2.2-12% range). FIT may be used as a shrinkage reducing monomer compatible with the conventional CQ-amine system as well as the alternative TPO photoinitiator. However, the depth of cure of FIT_TPO composite requires boosting to achieve clinically recommended thickness of 2mm. Copyright © 2015 Elsevier B.V. All rights reserved.

Solubilization and spore recovery from silicone polymers. Ph.D. Thesis

NASA Technical Reports Server (NTRS)

Hsiao, Y. C.

1974-01-01

A non-sporicidal technique for solvent degradation of cured silicone polymers was developed which involves chemical degradation of cured silicone polymers by amine solvents at room temperature. Substantial improvements were obtained in the recovery of seeded spores from room temperature cured polymers as compared to the standard recovery procedures, which indicates that the curing process is not sufficiently exothermic to reduce spore viability. The dissolution reaction of cured silicone polymers whith amine solvents is proposed to occur by bimolecular nucleophilic displacement. The chemical structure of silicone polymers was determined by spectroscopic methods. The phenyl to methyl ratio, R/Si ratio, molecular weight, and hydroxyl content of the silicone resins were determined.

Expectation Maximization Algorithm for Box-Cox Transformation Cure Rate Model and Assessment of Model Misspecification Under Weibull Lifetimes.

PubMed

Pal, Suvra; Balakrishnan, Narayanaswamy

2018-05-01

In this paper, we develop likelihood inference based on the expectation maximization algorithm for the Box-Cox transformation cure rate model assuming the lifetimes to follow a Weibull distribution. A simulation study is carried out to demonstrate the performance of the proposed estimation method. Through Monte Carlo simulations, we also study the effect of model misspecification on the estimate of cure rate. Finally, we analyze a well-known data on melanoma with the model and the inferential method developed here.

Novel self-healing materials chemistries for targeted applications

NASA Astrophysics Data System (ADS)

Wilson, Gerald O.

Self-healing materials of the type developed by White and co-workers [1] were designed to autonomically heal themselves when damaged, thereby extending the lifetime of various applications in which such material systems are employed. The system was based on urea-formaldehyde microcapsules containing dicyclopentadiene (DCPD) and Grubbs' catalyst particles embedded together in an epoxy matrix. When a crack propagates through the material, it ruptures the microcapsules, releasing DCPD into the crack plane, where it comes in contact and reacts with the catalyst to initiate a ring opening metathesis polymerization (ROMP), bonding the crack and restoring structural continuity. The present work builds on this concept in several ways. Firstly, it expands the scope and versatility of the ROMP self-healing chemistry by incorporation into epoxy vinyl ester matrices. Major technical challenges in this application include protection of the catalyst from deactivation by aggressive curing agents, and optimization of the concentration of healing agents in the matrix. Secondly, new ruthenium catalysts are evaluated for application in ROMP-based self-healing materials. The use of alternative derivatives of Grubbs' catalyst gave rise to self-healing systems with improved healing efficiencies and thermal properties. Evaluation of the stability of these new catalysts to primary amine curing agents used in the curing of common epoxy matrices also led to the discovery and characterization of new ruthenium catalysts which exhibited ROMP initiation kinetics superior to those of first and second generation Grubbs' catalysts. Finally, free radical polymerization was evaluated for application in the development of bio-compatible self-healing materials. [1] White, S. R.; Sottos, N. R.; Geubelle, P. R.; Moore, J. S.; Kessler, M. R.; Sriram, S. R.; Brown, E. N.; Viswanathan, S. Nature 2001, 409, 794.

Methods for multi-material stereolithography

DOEpatents

Wicker, Ryan [El Paso, TX; Medina, Francisco [El Paso, TX; Elkins, Christopher [Redwood City, CA

2011-06-14

Methods and systems of stereolithography for building cost-efficient and time-saving multi-material, multi-functional and multi-colored prototypes, models and devices configured for intermediate washing and curing/drying is disclosed including: laser(s), liquid and/or platform level sensing system(s), controllable optical system(s), moveable platform(s), elevator platform(s), recoating system(s) and at least one polymer retaining receptacle. Multiple polymer retaining receptacles may be arranged in a moveable apparatus, wherein each receptacle is adapted to actively/passively maintain a uniform, desired level of polymer by including a recoating device and a material fill/remove system. The platform is movably accessible to the polymer retaining receptacle(s), elevator mechanism(s) and washing and curing/drying area(s) which may be housed in a shielded enclosure(s). The elevator mechanism is configured to vertically traverse and rotate the platform, thus providing angled building, washing and curing/drying capabilities. A horizontal traversing mechanism may be included to facilitate manufacturing between components of SL cabinet(s) and/or alternative manufacturing technologies.

Beitrag zum mechanismus der oxydation von freiblei in bleiakkumulatorpaste bei der reifung

NASA Astrophysics Data System (ADS)

Duc Hung, Nguyen; Garche, J.; Wiesener, K.

The kinetics of lead oxidation during curing was studied by chemical analysis of the free lead content as well as by the gas volumetry of oxygen. The difference in the results in this research lies in the evolution of hydrogen as a curing reaction. This agrees with the results of curing the paste The optimal water content of the paste for lead oxidation was determined. A model for the electrolyte film during curing has been developed, which allows the results to be interpreted satisfactorily.

Visual Hybrid Development Learning System (VHDLS) framework for children with autism.

PubMed

Banire, Bilikis; Jomhari, Nazean; Ahmad, Rodina

2015-10-01

The effect of education on children with autism serves as a relative cure for their deficits. As a result of this, they require special techniques to gain their attention and interest in learning as compared to typical children. Several studies have shown that these children are visual learners. In this study, we proposed a Visual Hybrid Development Learning System (VHDLS) framework that is based on an instructional design model, multimedia cognitive learning theory, and learning style in order to guide software developers in developing learning systems for children with autism. The results from this study showed that the attention of children with autism increased more with the proposed VHDLS framework.

From scientific discovery to cures: bright stars within a galaxy.

PubMed

Williams, R Sanders; Lotia, Samad; Holloway, Alisha K; Pico, Alexander R

2015-09-24

We propose that data mining and network analysis utilizing public databases can identify and quantify relationships between scientific discoveries and major advances in medicine (cures). Further development of such approaches could help to increase public understanding and governmental support for life science research and could enhance decision making in the quest for cures. Copyright © 2015 Elsevier Inc. All rights reserved.

Heat stability of cured urea-formaldehyde resins by measuring formaldehyde emission

Treesearch

Shin-ichiro Tohmura; Chung-Yun Hse; Mitsuo Higuchi

1999-01-01

A test method for measuring formaldehyde from urea-formaldehyde (UF) resins at high tempera­tures was developed and used to assess the influence of the reaction pH at synthesis on the formaldehyde emission during cure and heat stability of the cured resins without water. Additionally, 13C-CP/MAS solid-state nuclear magnetic resonance (NMR)...

Effects of Curing Temperature and Pressure on the Chemical, Physical, and Mechanical Properties of Portland Cement

NASA Astrophysics Data System (ADS)

Pang, Xueyu

This dissertation mainly focuses on studying the fundamental hydration kinetics and mechanisms of Portland cement as well as the effects of curing temperature and pressure on its various properties. An innovative test apparatus has been developed in this study to cure and test cement paste specimens under in-situ conditions, such as down-hole in oil wells with high temperature and high pressure. Two series of tests were performed using cement pastes prepared with four different classes of oilwell cement (namely Class A, C, G, and H cements). Specimens in groups of four were cured at temperatures ranging from ambient to 60 °C and pressures ranging from 0.69 to 51.7 MPa for a period of 48 or 72 hours. The density and w/c ratio of the specimens at the time of casting as well as at the end of the curing period were recorded. Total chemical shrinkage of the cement paste was measured continuously during the entire hydration period while tensile strength was obtained at the end of the curing period using both water pressure and splitting tension test methods. Due to capacity limitations of the test equipment, in-situ tensile strength was obtained for only one test series with a highest curing pressure of 13.1 MPa. Specimens from the other test series were depressurized before the tensile strength tests. Chemical shrinkage test is an important method of measuring cement hydration kinetics in that the normalized total chemical shrinkage is approximately equal to the degree of cement hydration. By studying the correlations between the chemical shrinkage and the non-evaporable water content of cement during hydration, a multi-linear model is first proposed to estimate the normalization factors for different types of cement under different curing conditions. Based on the hydration kinetics data obtained from chemical shrinkage test results, a new approach of modeling the effect of curing temperature and pressure on cement hydration kinetics is proposed. It is found that when a hydration kinetics curve is represented by an unknown function, the effect of curing condition on the curve can be modeled by incorporating a simple scale factor in this function. The relationship between this scale factor and curing condition is described by chemical kinetics laws. While the proposed new approach of modeling cement hydration kinetics has the advantage of being widely applicable to different types of cement, it only explains one influence factor of cement hydration (i.e. the curing condition). In order to take into account other influence factors and to further understand the fundamental mechanisms of cement hydration, a more complex particle-based numerical hydration model is developed by combining the two well-known cement hydration mechanisms, namely the nucleation and growth controlled mechanism and the diffusion controlled mechanism. The model is applied to experimental data of both C3S hydration in dilute suspensions and Class H cement paste hydration. Excellent agreement is observed between experimental and modeled results. Three rate-controlling parameters with clear physical meanings can be identified from the proposed model. Fitted model parameters are found to be in reasonable agreement with experimental observation. The dependencies of these parameters on particle size, cement composition, w/c ratio, and curing condition are also investigated. Finally, the importance of cement hydration kinetics is illustrated by showing their close correlations with the physical and mechanical properties. The various influence factors, including the curing temperature and pressure, of physical and mechanical property test results (particularly density and tensile strength) are evaluated. Potential damage mechanisms of cement paste specimens during depressurization are studied by analyzing the deformation behavior of the entire system consisting of the cement paste and pressurizing water.

Latent curing systems stabilized by reaction equilibrium in homogeneous mixtures of benzoxazine and amine

PubMed Central

Wang, Jun; Xu, Ya Zhen; Fu, Ya Fei; Liu, Xiang Dong

2016-01-01

Latent curing systems are widely used in industrial thermosets in applications such as adhesion, coating, and composites. Despite many attempts to improve the practicality of this dormant reaction system, the majority of commercially available latent products still use particulate hardeners or liquid compounds with blocked active groups. These formulations generally lack fluidity or rapid reaction characteristics and thus are problematic in some industry applications. Here we describe a novel concept that stabilizes highly reactive benzoxazine/amine mixtures by reaction equilibrium. These new latent benzoxazine curing systems have a long storable lifetime but very short gel time at 150 °C. The reversible reaction between benzoxazine and amine is further demonstrated by FT-IR spectral measurements and rheological experiments, and it is shown that the overall characteristics of the latent system are promising for many industrial applications. PMID:27917932

Advanced Booster Composite Case/Polybenzimidazole Nitrile Butadiene Rubber Insulation Development

NASA Technical Reports Server (NTRS)

Gentz, Steve; Taylor, Robert; Nettles, Mindy

2015-01-01

The NASA Engineering and Safety Center (NESC) was requested to examine processing sensitivities (e.g., cure temperature control/variance, debonds, density variations) of polybenzimidazole nitrile butadiene rubber (PBI-NBR) insulation, case fiber, and resin systems and to evaluate nondestructive evaluation (NDE) and damage tolerance methods/models required to support human-rated composite motor cases. The proposed use of composite motor cases in Blocks IA and II was expected to increase performance capability through optimizing operating pressure and increasing propellant mass fraction. This assessment was to support the evaluation of risk reduction for large booster component development/fabrication, NDE of low mass-to-strength ratio material structures, and solid booster propellant formulation as requested in the Space Launch System NASA Research Announcement for Advanced Booster Engineering Demonstration and/or Risk Reduction. Composite case materials and high-energy propellants represent an enabling capability in the Agency's ability to provide affordable, high-performing advanced booster concepts. The NESC team was requested to provide an assessment of co- and multiple-cure processing of composite case and PBI-NBR insulation materials and evaluation of high-energy propellant formulations.

Volatile hydrocarbon profile of Iberian dry-cured hams. A possible tool for authentication of hams according to the fattening diet.

PubMed

Narváez-Rivas, Mónica; Vicario, Isabel M; Alcalde, M Jesús; León-Camacho, Manuel

2010-06-15

The aims of this work were to carry out a comprehensive study of the volatile hydrocarbons of 34 Iberian dry-cured hams and to evaluate the efficiency of these compounds for discriminating hams according to the fattening system: "Montanera" (B) and "Cebo" (C). The samples of hams were obtained by mincing the semimembranosus and semitendinosus muscles from slices of dry-cured ham. The analyses were carried out by gas chromatography-mass spectrometry with a polar capillary column and after a previous extraction by Purge and Trap method. Forty-three volatile hydrocarbons were identified, 26 of them for the first time in Iberian dry-cured ham. Only five compounds showed significant differences between the two types of hams. Among the 33 volatile hydrocarbons, 22 of them allowed a complete discrimination of the two groups of hams according the fattening system.

Characterization of a carbon fiber reinforced polymer repair system for structurally deficient steel piping

NASA Astrophysics Data System (ADS)

Wilson, Jeffrey M.

This Dissertation investigates a carbon fiber reinforced polymer repair system for structurally deficient steel piping. Numerous techniques exist for the repair of high-pressure steel piping. One repair technology that is widely gaining acceptance is composite over-wraps. Thermal analytical evaluations of the epoxy matrix material produced glass transition temperature results, a cure kinetic model, and a workability chart. These results indicate a maximum glass transition temperature of 80°C (176°F) when cured in ambient conditions. Post-curing the epoxy, however, resulted in higher glass-transition temperatures. The accuracy of cure kinetic model presented is temperature dependent; its accuracy improves with increased cure temperatures. Cathodic disbondment evaluations of the composite over-wrap show the epoxy does not breakdown when subjected to a constant voltage of -1.5V and the epoxy does not allow corrosion to form under the wrap from permeation. Combustion analysis of the composite over-wrap system revealed the epoxy is flammable when in direct contact with fire. To prevent combustion, an intumescent coating was developed to be applied on the composite over-wrap. Results indicate that damaged pipes repaired with the carbon fiber composite over-wrap withstand substantially higher static pressures and exhibit better fatigue characteristics than pipes lacking repair. For loss up to 80 percent of the original pipe wall thickness, the composite over-wrap achieved failure pressures above the pipe's specified minimum yield stress during monotonic evaluations and reached the pipe's practical fatigue limit during cyclical pressure testing. Numerous repairs were made to circular, thru-wall defects and monotonic pressure tests revealed containment up to the pipe's specified minimum yield strength for small diameter defects. The energy release rate of the composite over-wrap/steel interface was obtained from these full-scale, leaking pipe evaluations and results indicate a large amount of scatter is associated with this test method. Due to the large amount of scatter present in the leaking pipe evaluations (energy release rate tests), a new laboratory specimen was created to evaluate mixed mode debonding of composite over-wrapped piping. The laboratory specimen results are much more conservative than the leaking pipe evaluations. The laboratory specimen results, however, agree quite favorably to a closed form solution developed in this Dissertation, as well as to energy release rate calculations performed by two different finite element analysis methods, the Modified Crack Closure Integral and the change in compliance method.

Mechanical impedance measurements for improved cost-effective process monitoring

NASA Astrophysics Data System (ADS)

Clopet, Caroline R.; Pullen, Deborah A.; Badcock, Rodney A.; Ralph, Brian; Fernando, Gerard F.; Mahon, Steve W.

1999-06-01

The aerospace industry has seen a considerably growth in composite usage over the past ten years, especially with the development of cost effective manufacturing techniques such as Resin Transfer Molding and Resin Infusion under Flexible Tooling. The relatively high cost of raw material and conservative processing schedules has limited their growth further in non-aerospace technologies. In-situ process monitoring has been explored for some time as a means to improving the cost efficiency of manufacturing with dielectric spectroscopy and optical fiber sensors being the two primary techniques developed to date. A new emerging technique is discussed here making use of piezoelectric wafers with the ability to sense not only aspects of resin flow but also to detect the change in properties of the resin as it cures. Experimental investigations to date have shown a correlation between mechanical impedance measurements and the mechanical properties of cured epoxy systems with potential for full process monitoring.

American Society of Composites, 32nd Technical Conference

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

Aitharaju, Venkat; Yu, Hang; Zhao, Selina

Resin transfer molding (RTM) has become increasingly popular for the manufacturing of composite parts. To enable high volume manufacturing and obtain good quality parts at an acceptable cost to automotive industry, accurate process simulation tools are necessary to optimize the process conditions. Towards that goal, General Motors and the ESI-group are involved in developing a state of the art process simulation tool for composite manufacturing in a project supported by the Department of Energy. This paper describes the modeling of various stages in resin transfer molding such as resin injection, resin curing, and part distortion. An instrumented RTM system locatedmore » at the General Motors Research and Development center was used to perform flat plaque molding experiments. The experimental measurements of fill time, in-mold pressure versus time, cure variation with time, and part deformation were compared with the model predictions and very good correlations were observed.« less

Investigating the weight ratio variation of alginate-hydroxyapatite composites for vertebroplasty method bone filler material

NASA Astrophysics Data System (ADS)

Lestari, Gusti Ruri; Yuwono, Akhmad Herman; Sofyan, Nofrijon; Ramahdita, Ghiska

2017-02-01

One of the newly developed methods for curing spinal fracture due to osteoporosis is vertebroplasty. The method is basically based on injection of special material directly to the fractured spine in order to commence the formation of new bone. Therefore, appropriate injectable materials are very important to the curing success. In this study, injectable alginate-hydroxyapatite (HA) composites were fabricated varying the weight percentage of alginate upon synthesis procedure. The result of injection capability and compressive tests as well as Fourier transform infrared (FTIR) spectroscopy and scanning electron microscope (SEM) suggested that bone filler composite containing 60 wt% alginate is the optimum composition obtaining a compressive modulus up to 0.15 MPa, injection capability of more than 85% and morphology with uniform porous and fibrous structure. This injectable composite fabrication process can be used for the development of injectable materials system for vertebroplasty method.

Method for curing polymers using variable-frequency microwave heating

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

Lauf, R.J.; Bible, D.W.; Paulauskas, F.L.

1998-02-24

A method for curing polymers incorporating a variable frequency microwave furnace system designed to allow modulation of the frequency of the microwaves introduced into a furnace cavity is disclosed. By varying the frequency of the microwave signal, non-uniformities within the cavity are minimized, thereby achieving a more uniform cure throughout the workpiece. A directional coupler is provided for detecting the direction of a signal and further directing the signal depending on the detected direction. A first power meter is provided for measuring the power delivered to the microwave furnace. A second power meter detects the magnitude of reflected power. Themore » furnace cavity may be adapted to be used to cure materials defining a continuous sheet or which require compressive forces during curing. 15 figs.« less

Method for curing polymers using variable-frequency microwave heating

DOEpatents

Lauf, Robert J.; Bible, Don W.; Paulauskas, Felix L.

1998-01-01

A method for curing polymers (11) incorporating a variable frequency microwave furnace system (10) designed to allow modulation of the frequency of the microwaves introduced into a furnace cavity (34). By varying the frequency of the microwave signal, non-uniformities within the cavity (34) are minimized, thereby achieving a more uniform cure throughout the workpiece (36). A directional coupler (24) is provided for detecting the direction of a signal and further directing the signal depending on the detected direction. A first power meter (30) is provided for measuring the power delivered to the microwave furnace (32). A second power meter (26) detects the magnitude of reflected power. The furnace cavity (34) may be adapted to be used to cure materials defining a continuous sheet or which require compressive forces during curing.

Development of a method to manufacture uncured, no-nitrate/nitrite-added whole muscle jerky.

PubMed

Sindelar, Jeffrey J; Terns, Matthew J; Meyn, Elizabeth; Boles, Jane A

2010-10-01

"Natural curing" is accomplished by use of vegetable juice/powder high in naturally occurring nitrates combined with a nitrate reducing starter culture to result in indirectly "cured" products. Since the starter culture used is not water soluble, making "naturally cured" whole muscle jerky with current manufacturing techniques has been found ineffective. The objective was to investigate processes for whole muscle beef jerky that might provide cured meat characteristics similar to those of a nitrite-added control. Treatments where jerky was placed in a barrier bag during incubation were found to be the least similar to the nitrite-added control. Jerky placed in a 40.6 degrees C smokehouse during incubation resulted in significantly more (P<0.05) converted cured pigment than the barrier bag treatments but less (P<0.05) than the control. The processing methods investigated to manufacture "naturally cured" whole muscle jerky in this study were ineffective in resulting in products similar to those cured with sodium nitrite. Published by Elsevier Ltd.

Structure-Property Relationships of Bismaleimides

NASA Technical Reports Server (NTRS)

Tenteris-Noebe, Anita D.

1997-01-01

The purpose of this research was to control and systematically vary the network topology of bismaleimides through cure temperature and chemistry (addition of various coreactants) and subsequently attempt to determine structure-mechanical property relationships. Characterization of the bismaleimide structures by dielectric, rheological, and thermal analyses, and density measurements was subsequently correlated with mechanical properties such as modulus, yield strength, fracture energy, and stress relaxation. The model material used in this investigation was 4,4'-BismaleiMidodIphenyl methane (BMI). BMI was coreacted with either 4,4'-Methylene Dianiline (MDA), o,o'-diallyl bisphenol A (DABA) from Ciba Geigy, or Diamino Diphenyl Sulfone (DDS). Three cure paths were employed: a low- temperature cure of 140 C where chain extension should predominate, a high-temperature cure of 220 C where both chain extension and crosslinking should occur simultaneously, and a low-temperature (140 C) cure followed immediately by a high-temperature (220 C) cure where the chain extension reaction or amine addition precedes BMI homopolymerization or crosslinking. Samples of cured and postcured PMR-15 were also tested to determine the effects of postcuring on the mechanical properties. The low-temperature cure condition of BMI/MDA exhibited the highest modulus values for a given mole fraction of BMI with the modulus decreasing with decreasing concentration of BMI. The higher elastic modulus is the result of steric hindrance by unreacted BMI molecules in the glassy state. The moduli values for the high- and low/high-temperature cure conditions of BMI/MDA decreased as the amount of diamine increased. All the moduli values mimic the yield strength and density trends. For the high-temperature cure condition, the room- temperature modulus remained constant with decreasing mole fraction of BMT for the BMI/DABA and BMI/DDS systems. Postcuring PMR-15 increases the modulus over that of the cured material even though density values of cured and postcured PMR were essentially the same. Preliminary results of a continuous and intermittent stress relaxation experiment for BMI:MDA in a 2:1 molar ratio indicate that crosslinking is occurring when the sample is in the undeformed state. Computer simulation of properties such as density, glass transition temperature, and modulus for the low- temperature cure conditions of BMI/MDA and BMI/DABA were completed. The computer modeling was used to help further understand and confirm the structure characterization results. The simulations correctly predicted the trends of these properties versus mole fraction BMI and were extended to other BMI/diamine systems.

Development of a modified dry curing process for beef.

PubMed

Hayes, J E; Kenny, T A; Ward, P; Kerry, J P

2007-11-01

The development of a dry curing process using physical treatments to promote the diffusion of the cure ingredients was studied. Vacuum pulsing with and without tumbling, continuous vacuum, and tumbling only treatments were compared with a conventional static dry cure control method on beef M. supraspinatus. Vacuum tumble and tumble only treatments gave highest core salt content after 7 days conditioning (3.3% and 3.1%, respectively). All test treatments resulted in higher colour uniformity and lower % cook loss in comparison to control (P<0.001). The control and vacuum pulsed samples were tougher (P<0.001). Vacuum tumble and tumble only treatments gave higher acceptability (P<0.001). Based on these findings for M. supraspinatus, indicating that the vacuum tumble treatments gave the best results, further testing of this method was conducted using the M. biceps femoris in addition to the M. supraspinatus. Cured beef slices were stored in modified atmosphere packs (MAP) (80%N(2):20%CO(2)) for up to 28 day at 4°C. Redness (a(∗), P<0.001) decreased over storage time in M. biceps femoris. Vacuum tumble treatment increased (P<0.05) redness in M. supraspinatus. Results obtained demonstrate the benefits of vacuum tumbling over the other physical treatments as a method for accelerating the dry curing process, producing dry cured beef products with enhanced organoleptic quality and increased yields.

Optimal cure cycle design of a resin-fiber composite laminate

NASA Technical Reports Server (NTRS)

Hou, Jean W.; Sheen, Jeenson

1987-01-01

A unified computed aided design method was studied for the cure cycle design that incorporates an optimal design technique with the analytical model of a composite cure process. The preliminary results of using this proposed method for optimal cure cycle design are reported and discussed. The cure process of interest is the compression molding of a polyester which is described by a diffusion reaction system. The finite element method is employed to convert the initial boundary value problem into a set of first order differential equations which are solved simultaneously by the DE program. The equations for thermal design sensitivities are derived by using the direct differentiation method and are solved by the DE program. A recursive quadratic programming algorithm with an active set strategy called a linearization method is used to optimally design the cure cycle, subjected to the given design performance requirements. The difficulty of casting the cure cycle design process into a proper mathematical form is recognized. Various optimal design problems are formulated to address theses aspects. The optimal solutions of these formulations are compared and discussed.

Rapid prediction of ochratoxin A-producing strains of Penicillium on dry-cured meat by MOS-based electronic nose.

PubMed

Lippolis, Vincenzo; Ferrara, Massimo; Cervellieri, Salvatore; Damascelli, Anna; Epifani, Filomena; Pascale, Michelangelo; Perrone, Giancarlo

2016-02-02

The availability of rapid diagnostic methods for monitoring ochratoxigenic species during the seasoning processes for dry-cured meats is crucial and constitutes a key stage in order to prevent the risk of ochratoxin A (OTA) contamination. A rapid, easy-to-perform and non-invasive method using an electronic nose (e-nose) based on metal oxide semiconductors (MOS) was developed to discriminate dry-cured meat samples in two classes based on the fungal contamination: class P (samples contaminated by OTA-producing Penicillium strains) and class NP (samples contaminated by OTA non-producing Penicillium strains). Two OTA-producing strains of Penicillium nordicum and two OTA non-producing strains of Penicillium nalgiovense and Penicillium salamii, were tested. The feasibility of this approach was initially evaluated by e-nose analysis of 480 samples of both Yeast extract sucrose (YES) and meat-based agar media inoculated with the tested Penicillium strains and incubated up to 14 days. The high recognition percentages (higher than 82%) obtained by Discriminant Function Analysis (DFA), either in calibration and cross-validation (leave-more-out approach), for both YES and meat-based samples demonstrated the validity of the used approach. The e-nose method was subsequently developed and validated for the analysis of dry-cured meat samples. A total of 240 e-nose analyses were carried out using inoculated sausages, seasoned by a laboratory-scale process and sampled at 5, 7, 10 and 14 days. DFA provided calibration models that permitted discrimination of dry-cured meat samples after only 5 days of seasoning with mean recognition percentages in calibration and cross-validation of 98 and 88%, respectively. A further validation of the developed e-nose method was performed using 60 dry-cured meat samples produced by an industrial-scale seasoning process showing a total recognition percentage of 73%. The pattern of volatile compounds of dry-cured meat samples was identified and characterized by a developed HS-SPME/GC-MS method. Seven volatile compounds (2-methyl-1-butanol, octane, 1R-α-pinene, d-limonene, undecane, tetradecanal, 9-(Z)-octadecenoic acid methyl ester) allowed discrimination between dry-cured meat samples of classes P and NP. These results demonstrate that MOS-based electronic nose can be a useful tool for a rapid screening in preventing OTA contamination in the cured meat supply chain. Copyright © 2015 Elsevier B.V. All rights reserved.

Development of aircraft lavatory compartments with improved fire resistance characteristics. Phase 4: Sandwich panel decorative ink development

NASA Technical Reports Server (NTRS)

Jayarajan, A.; Johnson, G. A.; Korver, G. L.; Anderson, R. A.

1983-01-01

Five chemically different resin systems with improved fire resistance properties were studied for a possible screenprinting ink application. Fire resistance is hereby defined as the cured ink possessing improvements in flammability, smoke emission, and thermal stability. The developed ink is for application to polyvinyl fluoride film. Only clear inks without pigments were considered. Five formulations were evaluated compared with KC4900 clear acrylic ink, which was used as a baseline. The tests used in the screening evaluation included viscosity, smoke and toxic gas emission, limiting oxygen index (LOI), and polyvinyl fluoride film (PVF) printability. A chlorofluorocarbon resin (FPC461) was selected for optimization studies. The parameters for optimization included screenprinting process performance, quality of coating, and flammability of screenprinted 0.051-mm (0.002-in.) white Tedlar. The quality of the screenprinted coating on Tedlar is dependent on viscosity, curing time, adhesion to polyvinyl fluoride film, drying time (both inscreen and as an applied film), and silk screen mesh material and porosity.

Cure models for estimating hospital-based breast cancer survival.

PubMed

Rama, Ranganathan; Swaminathan, Rajaraman; Venkatesan, Perumal

2010-01-01

Research on cancer survival is enriched by development and application of innovative analytical approaches in relation to standard methods. The aim of the present paper is to document the utility of a mixture model to estimate the cure fraction and compare it with other approaches. The data were for 1,107 patients with locally advanced breast cancer, who completed the neo-adjuvant treatment protocol during 1990-99 at the Cancer Institute (WIA), Chennai, India. Tumour stage, post-operative pathological node (PN) and tumour residue (TR) status were studied. Event free survival probability was estimated using the Kaplan-Meier method. Cure models under proportional and non-proportional hazard assumptions following log normal distribution for survival time were used to estimate both the cure fraction and the survival function for the uncured. Event free survival at 5 and 10 years were 64.2% and 52.6% respectively and cure fraction was 47.5% for all cases together. Follow up ranged between 0-15 years and survival probabilities showed minimal changes after 7 years of follow up. TR and PN emerged as independent prognostic factors using Cox and proportional hazard (PH) cure models. Proportionality condition was violated when tumour stage was considered and it was statistically significant only under PH and not under non PH cure models. However, TR and PN continued to be independent prognostic factors after adjusting for tumour stage using the non PH cure model. A consistent ordering of cure fractions with respect to factors of PN and TR was forthcoming across tumour stages using PH and non PH cure models, but perceptible differences in survival were observed between the two. If PH conditions are violated, analysis using a non PH model is advocated and mixture cure models are useful in estimating the cure fraction and constructing survival curves for non-cures.

Design and development of pressure and repressurization purge system for reusable space shuttle multilayer insulation system

NASA Technical Reports Server (NTRS)

1972-01-01

The experimental determination of purge bag materials properties, development of purge bag manufacturing techniques, experimental evaluation of a subscale purge bag under simulated operating conditions and the experimental evaluation of the purge pin concept for MLI purging are discussed. The basic purge bag material, epoxy fiberglass bounded by skins of FEP Teflon, showed no significant permeability to helium flow under normal operating conditions. Purge bag small scale manufacturing tests were conducted to develop tooling and fabrication techniques for use in full scale bag manufacture. A purge bag material layup technique was developed whereby the two plys of epoxy fiberglass enclosed between skins of FEP Teflon are vacuum bag cured in an oven in a single operation. The material is cured on a tool with the shape of a purge bag half. Plastic tooling was selected for use in bag fabrication. A model purge bag 0.6 m in diameter was fabricated and subjected to a series of structural and environmental tests simulating various flight type environments. Pressure cycling tests at high (450 K) and low (200 K) temperature as well as acoustic loading tests were performed. The purge bag concept proved to be structurally sound and was used for the full scale bag detailed design model.

Effect of dual-cure composite resin as restorative material on marginal adaptation of class 2 restorations.

PubMed

Bortolotto, Tissiana; Melian, Karla; Krejci, Ivo

2013-10-01

The present study attempted to find a simple direct adhesive restorative technique for the restoration of Class 2 cavities. A self-etch adhesive system with a dual-cured core buildup composite resin (paste 1 + paste 2) was evaluated in its ability to restore proximo-occlusal cavities with margins located on enamel and dentin. The groups were: A, cavity filling (cf) with paste 1 (light-curing component) by using a layering technique; B, cf by mixing both pastes, bulk insertion, and dual curing; and C, cf by mixing both pastes, bulk insertion, and chemical curing. Two control groups (D, negative, bulk; and E, positive, layering technique) were included by restoring cavities with a classic three-step etch-and-rinse adhesive and a universal restorative composite resin. SEM margin analysis was performed before and after thermomechanical loading in a chewing simulator. Percentages (mean ± SD) of "continuous margins" were improved by applying the material in bulk and letting it self cure (54 ± 6) or dual cure (59 ± 9), and no significant differences were observed between these two groups and the positive control (44 ± 19). The present study showed that the dual-cured composite resin tested has the potential to be used as bulk filling material for Class 2 restorations. When used as filling materials, dual-cure composite resins placed in bulk can provide marginal adaptation similar to light-cured composites applied with a complex stratification technique.

Application of mass spectrometry to process control for polymer material in autoclave curing

NASA Technical Reports Server (NTRS)

Smith, A. C.

1983-01-01

Mass spectrometer analysis of gas samples collected during a cure cycle of polymer materials can be used as a process control technique. This technique is particularly helpful in studying the various types of solvents and resin systems used in the preparation of polymer materials and characterizing the chemical composition of different resin systems and their mechanism of polymerization.

A Survey of Electronics Obsolescence and Reliability

DTIC Science & Technology

2010-07-01

properties but there are many minor and major variations (e.g. curing schedule) affecting their usage in packaging processes and in reworking. Curing...within them. Electronic obsolescence is increasingly associated with physical characteristics that reduce component and system reliability, both in usage ...semiconductor technologies and of electronic systems, both in usage and in storage. By design, electronics technologies include few reliability margins

Monitoring Prepregs As They Cure

NASA Technical Reports Server (NTRS)

Young, P. R.; Gleason, J. R.; Chang, A. C.

1986-01-01

Quality IR spectra obtained in dynamic heating environment. New technique obtains quality infrared spectra on graphite-fiber-reinforced, polymeric-matrix-resin prepregs as they cure. Technique resulted from modification of diffuse reflectance/Fourier transform infrared (DR/FTIR) technique previously used to analyze environmentally exposed cured graphite composites. Technique contribute to better understanding of prepreg chemistry/temperature relationships and development of more efficient processing cycles for advanced materials.

TiO₂-Based Photocatalytic Geopolymers for Nitric Oxide Degradation.

PubMed

Strini, Alberto; Roviello, Giuseppina; Ricciotti, Laura; Ferone, Claudio; Messina, Francesco; Schiavi, Luca; Corsaro, Davide; Cioffi, Raffaele

2016-06-24

This study presents an experimental overview for the development of photocatalytic materials based on geopolymer binders as catalyst support matrices. Particularly, geopolymer matrices obtained from different solid precursors (fly ash and metakaolin), composite systems (siloxane-hybrid, foamed hybrid), and curing temperatures (room temperature and 60 °C) were investigated for the same photocatalyst content (i.e., 3% TiO₂ by weight of paste). The geopolymer matrices were previously designed for different applications, ranging from insulating (foam) to structural materials. The photocatalytic activity was evaluated as NO degradation in air, and the results were compared with an ordinary Portland cement reference. The studied matrices demonstrated highly variable photocatalytic performance depending on both matrix constituents and the curing temperature, with promising activity revealed by the geopolymers based on fly ash and metakaolin. Furthermore, microstructural features and titania dispersion in the matrices were assessed by scanning electron microscopy (SEM) and energy dispersive X-ray (EDS) analyses. Particularly, EDS analyses of sample sections indicated segregation effects of titania in the surface layer, with consequent enhancement or depletion of the catalyst concentration in the active sample region, suggesting non-negligible transport phenomena during the curing process. The described results demonstrated that geopolymer binders can be interesting catalyst support matrices for the development of photocatalytic materials and indicated a large potential for the exploitation of their peculiar features.

Willingness to participate and take risks in HIV cure research: survey results from 400 people living with HIV in the US.

PubMed

Dubé, Karine; Evans, David; Sylla, Laurie; Taylor, Jeff; Weiner, Bryan J; Skinner, Asheley; Thirumurthy, Harsha; Tucker, Joseph D; Rennie, Stuart; Greene, Sandra B

2017-01-01

Participation in early-phase HIV cure studies includes clinical risks with little to no likelihood of clinical benefit. Examining the willingness of people living with HIV to participate is important to guide study design and informed consent. Our study examined the overall willingness of people living with HIV to participate in HIV cure research in the US, focusing on perceived risks and benefits of participation. We undertook an online survey of adults living with HIV in the US. Survey questions were developed based on previous research and a scoping review of the literature. We quantitatively assessed individuals' perceived risks and benefits of HIV cure-related research and respondents' willingness to participate in different modalities of HIV cure studies. We recruited 409 study participants of whom 400 were eligible for the study and were included in the analysis (nine were not eligible due to self-declared HIV-negative status). We found >50% willingness to participate in 14 different types of HIV cure studies. Perceived clinical benefits and social benefits were important motivators, while personal clinical risks appeared to deter potential participation. Roughly two-thirds of survey respondents (68%) indicated that they were somewhat willing to stop treatment as part of HIV cure research. In the bivariate models, females, African Americans/blacks, Hispanics, individuals in the lowest income bracket, people living with HIV for longer periods of their lives, and people who were self-perceived 'very healthy' were less willing to participate in certain types of HIV cure studies than others. Multivariate results showed the perceived benefits (adjusted odds ratios >1) and perceived risks (adjusted odds ratios <1) acted as potential motivators and deterrents to participation, respectively. Our study is the first attempt to quantify potential motivators and deterrents of participation in HIV cure research in the US using perceived risks and benefits. The results offer guidance to HIV cure researchers and developers of interventions about the beneficial and detrimental characteristics of HIV cure strategies that are most meaningful to people living with HIV. The study also highlights new potential lines of inquiry for further social science and ethics research.

Women in HIV cure research: multilevel interventions to improve sex equity in recruitment.

PubMed

Grewe, Mary E; Ma, Yuntong; Gilbertson, Adam; Rennie, Stuart; Tucker, Joseph D

Women are underrepresented in HIV cure research. In this paper we discuss the rationale for including women and propose multilevel strategies to improve sex equity in HIV cure research. The inadequate inclusion of women in HIV cure research is concerning for both scientific and ethical reasons. Biological responses to HIV and HIV treatment, as well as social contexts, differ between men and women, and this may affect the efficacy of curative interventions. Strategies for improving sex equity in HIV cure research include addressing eligibility criteria, adapting recruitment strategies, engaging community members early in the research process, and promoting funder policy changes. We conclude by describing the Gender, Race, and Clinical Experience (GRACE) study, which is one example of how women can be effectively recruited into HIV-related clinical trials. While HIV cure research is currently in the early stages, as it continues to develop it is important to mobilise for adequate inclusion of women.

High performance UV and thermal cure hybrid epoxy adhesive

NASA Astrophysics Data System (ADS)

Chen, C. F.; Iwasaki, S.; Kanari, M.; Li, B.; Wang, C.; Lu, D. Q.

2017-06-01

New type one component UV and thermal curable hybrid epoxy adhesive was successfully developed. The hybrid epoxy adhesive is complete initiator free composition. Neither photo-initiator nor thermal initiator is contained. The hybrid adhesive is mainly composed of special designed liquid bismaleimide, partially acrylated epoxy resin, acrylic monomer, epoxy resin and latent curing agent. Its UV light and thermal cure behavior was studied by FT-IR spectroscopy and FT-Raman spectroscopy. Adhesive samples cured at UV only, thermal only and UV + thermal cure conditions were investigated. By calculated conversion rate of double bond in both acrylic component and maleimide compound, satisfactory light curability of the hybrid epoxy adhesive was confirmed quantitatively. The investigation results also showed that its UV cure components, acrylic and bismalimide, possess good thermal curability too. The initiator free hybrid epoxy adhesive showed satisfactory UV curability, good thermal curability and high adhesion performance.

Influence of light intensity on surface free energy and dentin bond strength of core build-up resins.

PubMed

Shimizu, Y; Tsujimoto, A; Furuichi, T; Suzuki, T; Tsubota, K; Miyazaki, M; Platt, J A

2015-01-01

We examined the influence of light intensity on surface free energy characteristics and dentin bond strength of dual-cure direct core build-up resin systems. Two commercially available dual-cure direct core build-up resin systems, Clearfil DC Core Automix with Clearfil Bond SE One and UniFil Core EM with Self-Etching Bond, were studied. Bovine mandibular incisors were mounted in acrylic resin and the facial dentin surfaces were wet ground on 600-grit silicon carbide paper. Adhesives were applied to dentin surfaces and cured with light intensities of 0 (no irradiation), 200, 400, and 600 mW/cm(2). The surface free energy of the adhesives (five samples per group) was determined by measuring the contact angles of three test liquids placed on the cured adhesives. To determine the strength of the dentin bond, the core build-up resin pastes were condensed into the mold on the adhesive-treated dentin surfaces according to the methods described for the surface free energy measurement. The resin pastes were cured with the same light intensities as those used for the adhesives. Ten specimens per group were stored in water maintained at 37°C for 24 hours, after which they were shear tested at a crosshead speed of 1.0 mm/minute in a universal testing machine. Two-way analysis of variance (ANOVA) and a Tukey-Kramer test were performed, with the significance level set at 0.05. The surface free energies of the adhesive-treated dentin surfaces decreased with an increase in the light intensity of the curing unit. Two-way ANOVA revealed that the type of core build-up system and the light intensity significantly influence the bond strength, although there was no significant interaction between the two factors. The highest bond strengths were achieved when the resin pastes were cured with the strongest light intensity for all the core build-up systems. When polymerized with a light intensity of 200 mW/cm(2) or less, significantly lower bond strengths were observed. CONClUSIONS: The data suggest that the dentin bond strength of core build-up systems are still affected by the light intensity of the curing unit, which is based on the surface free energy of the adhesives. On the basis of the results and limitations of the test conditions used in this study, it appears that a light intensity of >400 mW/cm(2) may be required for achieving the optimal dentin bond strength.

Property Changes of Cyanate Ester/epoxy Insulation Systems Caused by AN Iter-Like Double Impregnation and by Reactor Irradiation

NASA Astrophysics Data System (ADS)

Prokopec, R.; Humer, K.; Fillunger, H.; Maix, R. K.; Weber, H. W.

2010-04-01

Because of the double pancake design of the ITER TF coils the insulation will be applied in several steps. As a consequence, the conductor insulation as well as the pancake insulation will undergo multiple heat cycles in addition to the initial curing cycle. In particular the properties of the organic resin may be influenced, since its heat resistance is limited. Two identical types of sample consisting of wrapped R-glass/Kapton layers and vacuum impregnated with a cyanate ester/epoxy blend were prepared. The build-up of the reinforcement was identical for both insulation systems; however, one system was fabricated in two steps. In the first step only one half of the reinforcing layers was impregnated and cured. Afterwards the remaining layers were wrapped onto the already cured system, before the resulting system was impregnated and cured again. The mechanical properties were characterized prior to and after irradiation to fast neutron fluences of 1 and 2×1022 m-2 (E>0.1 MeV) in tension and interlaminar shear at 77 K. In order to simulate the pulsed operation of ITER, tension-tension fatigue measurements were performed in the load controlled mode. The results do not show any evidence for reduced mechanical strength caused by the additional heat cycle.

Strength of Geopolymer Cement Curing at Ambient Temperature by Non-Oven Curing Approaches: An Overview

NASA Astrophysics Data System (ADS)

Wattanachai, Pitiwat; Suwan, Teewara

2017-06-01

At the present day, a concept of environmentally friendly construction materials has been intensively studying to reduce the amount of releasing greenhouse gases. Geopolymer is one of the cementitious binders which can be produced by utilising pozzolanic wastes (e.g. fly ash or furnace slag) and also receiving much more attention as a low-CO2 emission material. However, to achieve excellent mechanical properties, heat curing process is needed to apply to geopolymer cement in a range of temperature around 40 to 90°C. To consume less oven-curing energy and be more convenience in practical work, the study on geopolymer curing at ambient temperature (around 20 to 25°C) is therefore widely investigated. In this paper, a core review of factors and approaches for non-oven curing geopolymer has been summarised. The performance, in term of strength, of each non-oven curing method, is also presented and analysed. The main aim of this review paper is to gather the latest study of ambient temperature curing geopolymer and to enlarge a feasibility of non-oven curing geopolymer development. Also, to extend the directions of research work, some approaches or techniques can be combined or applied to the specific properties for in-field applications and embankment stabilization by using soil-cement column.

Argon Ion Laser Polymerized Acrylic Resin: A Comparative Analysis of Mechanical Properties of Laser Cured, Light Cured and Heat Cured Denture Base Resins

PubMed Central

Murthy, S Srinivasa; Murthy, Gargi S

2015-01-01

Background: Dentistry in general and prosthodontics in particular is evolving at greater pace, but the denture base resins poly methyl methacrylate. There has been vast development in modifying chemically and the polymerization techniques for better manipulation and enhancement of mechanical properties. One such invention was introduction of visible light cure (VLC) denture base resin. Argon ion lasers have been used extensively in dentistry, studies has shown that it can polymerize restorative composite resins. Since composite resin and VLC resin share the same photo initiator, Argon laser is tested as activator for polymerizing VLC resin. In the Phase 1 study, the VLC resin was evaluated for exposure time for optimum polymerization using argon ion laser and in Phase 2; flexural strength, impact strength, surface hardness and surface characteristics of laser cured resin was compared with light cure and conventional heat cure resin. Materials and Methods: Phase 1; In compliance with American Dental Association (ADA) specification no. 12, 80 samples were prepared with 10 each for different curing time using argon laser and evaluated for flexural strength on three point bend test. Results were compared to established performance requirement specified. Phase 2, 10 specimen for each of the mechanical properties (30 specimen) were polymerized using laser, visible light and heat and compared. Surface and fractured surface of laser, light and heat cured resins were examined under scanning electron microscope (SEM). Results: In Phase 1, the specimen cured for 7, 8, 9 and 10 min fulfilled ADA requirement. 8 min was taken as suitable curing time for laser curing. Phase 2 the values of mechanical properties were computed and subjected to statistical analysis using one-way ANOVA and Tukey post-hoc test. The means of three independent groups showed significant differences between any two groups (P < 0.001). Conclusion: Triad VLC resin can be polymerized by argon ion laser with 1 W/mm2 power and exposure time of 8 min to satisfy ADA specification. Impact strength, surface hardness of laser cure was better than light cure and heat cure resin. Flexural strength of light cure was better than laser cure and heat cure resin. The SEM study showed similar density on surface, the fractured surface of heat cure resin was dense and compact. PMID:26124596

A development of visible light cured FRP plate denture.

PubMed

Kimura, H; Teraoka, F

1990-12-01

A FRP denture base, which was made from visible light curing prepreg, was developed. The visible light cured FRP denture base had advantages with respect to an adequate strength, bonding strength of acrylic base resin, esthetic properties and ease to manipulation. The matrix resin of Bis-GMA/UDMA/3 G at 48/48/4 was determined from the results of the bending test and manipulation processing. The sateen weave's glasscloth was used for the reinforcement of the prepreg. The adaptability of the FRP plate denture was better than that of the resin base denture constructed with microwave heating.

A criterion for maximum resin flow in composite materials curing process

NASA Astrophysics Data System (ADS)

Lee, Woo I.; Um, Moon-Kwang

1993-06-01

On the basis of Springer's resin flow model, a criterion for maximum resin flow in autoclave curing is proposed. Validity of the criterion was proved for two resin systems (Fiberite 976 and Hercules 3501-6 epoxy resin). The parameter required for the criterion can be easily estimated from the measured resin viscosity data. The proposed criterion can be used in establishing the proper cure cycle to ensure maximum resin flow and, thus, the maximum compaction.

Investigation of the Use of Match Cure Technology in the Precast Concrete Industry

DOT National Transportation Integrated Search

1998-08-01

This project was proposed to evaluate the feasibility and methodology of implementing match cure technology and maturity measurement systems into TxDOT acceptance criteria for concrete construction projects. This report will deal strictly with the in...

Stavudine

MedlinePlus

... HIV in the blood. Although stavudine does not cure HIV, it may decrease your chance of developing acquired ... provided to measure the child's dose.Stavudine controls HIV infection but does not cure it. Continue to take stavudine even if you ...

Etravirine

MedlinePlus

... HIV in the blood. Although etravirine does not cure HIV, it may decrease your chance of developing acquired ... entire dose is taken.Etravirine helps to control HIV infection, but does not cure it. Continue to take etravirine even if you ...

Emtricitabine

MedlinePlus

... HIV in the blood. Although emtricitabine does not cure HIV, it may decrease your chance of developing acquired ... often than prescribed by your doctor.Emtricitabine controls HIV infection but does not cure it. Continue to take emtricitabine even if you ...

Abacavir

MedlinePlus

... HIV in the blood. Although abacavir does not cure HIV, it may decrease your chance of developing acquired ... prescribed by your doctor.Abacavir helps to control HIV infection but does not cure it. Continue to take abacavir even if you ...

Fosamprenavir

MedlinePlus

... HIV in the blood. Although fosamprenavir does not cure HIV, it may decrease your chance of developing acquired ... take another full dose of fosamprenavir.Fosamprenavir controls HIV infection but does not cure it. Continue to take fosamprenavir even if you ...

Adhesive curing through low-voltage activation

PubMed Central

Ping, Jianfeng; Gao, Feng; Chen, Jian Lin; Webster, Richard D.; Steele, Terry W. J.

2015-01-01

Instant curing adhesives typically fall within three categories, being activated by either light (photocuring), heat (thermocuring) or chemical means. These curing strategies limit applications to specific substrates and can only be activated under certain conditions. Here we present the development of an instant curing adhesive through low-voltage activation. The electrocuring adhesive is synthesized by grafting carbene precursors on polyamidoamine dendrimers and dissolving in aqueous solvents to form viscous gels. The electrocuring adhesives are activated at −2 V versus Ag/AgCl, allowing tunable crosslinking within the dendrimer matrix and on both electrode surfaces. As the applied voltage discontinued, crosslinking immediately terminated. Thus, crosslinking initiation and propagation are observed to be voltage and time dependent, enabling tuning of both material properties and adhesive strength. The electrocuring adhesive has immediate implications in manufacturing and development of implantable bioadhesives. PMID:26282730

A statistical comparison of two carbon fiber/epoxy fabrication techniques

NASA Technical Reports Server (NTRS)

Hodge, A. J.

1991-01-01

A statistical comparison of the compression strengths of specimens that were fabricated by either a platen press or an autoclave were performed on IM6/3501-6 carbon/epoxy composites of 16-ply (0,+45,90,-45)(sub S2) lay-up configuration. The samples were cured with the same parameters and processing materials. It was found that the autoclaved panels were thicker than the platen press cured samples. Two hundred samples of each type of cure process were compression tested. The autoclaved samples had an average strength of 450 MPa (65.5 ksi), while the press cured samples had an average strength of 370 MPa (54.0 ksi). A Weibull analysis of the data showed that there is only a 30 pct. probability that the two types of cure systems yield specimens that can be considered from the same family.

78 FR 46969 - Human Immunodeficiency Virus Patient-Focused Drug Development and Human Immunodeficiency Virus...

Federal Register 2010, 2011, 2012, 2013, 2014

2013-08-02

... for the notice of public meeting entitled ``Human Immunodeficiency Virus (HIV) Patient-Focused Drug Development and HIV Cure Research,'' published in the Federal Register of May 21, 2013 (78 FR 29755). In that... HIV, symptoms experienced because of HIV or its treatment, and issues related to HIV cure research...

Tools for Visualizing HIV in Cure Research.

PubMed

Niessl, Julia; Baxter, Amy E; Kaufmann, Daniel E

2018-02-01

The long-lived HIV reservoir remains a major obstacle for an HIV cure. Current techniques to analyze this reservoir are generally population-based. We highlight recent developments in methods visualizing HIV, which offer a different, complementary view, and provide indispensable information for cure strategy development. Recent advances in fluorescence in situ hybridization techniques enabled key developments in reservoir visualization. Flow cytometric detection of HIV mRNAs, concurrently with proteins, provides a high-throughput approach to study the reservoir on a single-cell level. On a tissue level, key spatial information can be obtained detecting viral RNA and DNA in situ by fluorescence microscopy. At total-body level, advancements in non-invasive immuno-positron emission tomography (PET) detection of HIV proteins may allow an encompassing view of HIV reservoir sites. HIV imaging approaches provide important, complementary information regarding the size, phenotype, and localization of the HIV reservoir. Visualizing the reservoir may contribute to the design, assessment, and monitoring of HIV cure strategies in vitro and in vivo.

Analysis of cured carbon-phenolic decomposition products to investigate the thermal decomposition of nozzle materials

NASA Technical Reports Server (NTRS)

Thompson, James M.; Daniel, Janice D.

1989-01-01

The development of a mass spectrometer/thermal analyzer/computer (MS/TA/Computer) system capable of providing simultaneous thermogravimetry (TG), differential thermal analysis (DTA), derivative thermogravimetry (DTG) and evolved gas detection and analysis (EGD and EGA) under both atmospheric and high pressure conditions is described. The combined system was used to study the thermal decomposition of the nozzle material that constitutes the throat of the solid rocket boosters (SRB).

An unexpected journey: how cancer immunotherapy has paved the way for an HIV-1 cure.

PubMed

Smith, Kellie N; Housseau, Franck

2015-03-01

Over 30 million people worldwide are currently infected with human immunodeficiency virus type-1 (HIV-1). While HIV-1 infection was initially thought to be a death sentence, the advent of combination antiretroviral therapy (cART) in the mid-1990's resulted in decreases in viremia and an extended lifespan for infected persons. Despite this, long-term control of the virus in the absence of drug therapy has yet to be achieved, owing to the rebound in viral load and resumption of disease progression that follows removal of the patient from cART. Currently, the most promising candidates for an HIV-1 cure are immunotherapies that harness the patient's own immune system and induce cytotoxic T lymphocyte (CTL)-mediated clearance of infected cells. Most of these approaches were developed and optimized in the cancer setting and have had varying degrees of success, the findings from which have wide applications to various disease models. In this review, we evaluate the past successes and failures of cancer immunotherapy and how the findings have shaped our journey toward an HIV-1 cure.

Looking back and to the future: Are we improving 'cure' in non-small cell lung cancer?

PubMed

Walder, David; O'Brien, Mary

2017-04-01

In surgical series, cancer-free survival at 5 years is often referred to as a cure. In recent years, attempts to improve cure rates in non-small cell lung cancer (NSCLC) have focussed on earlier diagnosis through cost-effective screening programs. Systemic therapies have historically added only a small benefit to overall survival in both the adjuvant and palliative setting. However, in the last two decades, the development of new treatment options has added incremental improvements in NSCLC survival rates. Patients with a targetable sensitising mutation including epidermal growth factor receptor gene mutations and anaplastic lymphoma kinase rearrangements have significantly better prognosis, and many will survive beyond 5 years. Immunotherapy is an effective treatment in selected patients with NSCLC and is set to cause another leap in 5 year survival rates. Although these patients are not free from disease, survival at 5 years may become the more important end-point as NSCLC becomes seen as a chronic oncological disease. Copyright © 2017 Elsevier Ltd. All rights reserved.

On the use of the EMI for the health monitoring of bonded elements

NASA Astrophysics Data System (ADS)

Gulizzi, Vincenzo; Rizzo, Piervincenzo; Milazzo, Alberto

2014-03-01

The low weight, robustness and fatigue resistance of adhesive joints make them suitable for structural joints. A fully developed nondestructive evaluation technique however is needed to monitor and assess the quality of bonded joints. In the present paper the application of the electromechanical impedance (EMI) technique is proposed. In the EMI method a piezoelectric transducer (PZT) is attached to the structure of interest. The high sensitivity and low power consumption make the EMI method feasible for real time structural health monitoring. In this study we investigated the sensitivity of the electromechanical response of a PZT to the curing and the quality of the adhesive used for bonded joints. A PXI unit running under LabView and an auxiliary circuit were employed to measure the electric impedance of a PZT glued to an aluminum plate. The system aimed at monitoring the bond line between an aluminum strip and the plate. The conductive signature of the PZT was measured and analyzed during the curing. The experimental results show that the electromechanical impedance technique is sensitive to the curing time and variations are observed for adhesives of different quality.

Signal inference with unknown response: calibration-uncertainty renormalized estimator.

PubMed

Dorn, Sebastian; Enßlin, Torsten A; Greiner, Maksim; Selig, Marco; Boehm, Vanessa

2015-01-01

The calibration of a measurement device is crucial for every scientific experiment, where a signal has to be inferred from data. We present CURE, the calibration-uncertainty renormalized estimator, to reconstruct a signal and simultaneously the instrument's calibration from the same data without knowing the exact calibration, but its covariance structure. The idea of the CURE method, developed in the framework of information field theory, is to start with an assumed calibration to successively include more and more portions of calibration uncertainty into the signal inference equations and to absorb the resulting corrections into renormalized signal (and calibration) solutions. Thereby, the signal inference and calibration problem turns into a problem of solving a single system of ordinary differential equations and can be identified with common resummation techniques used in field theories. We verify the CURE method by applying it to a simplistic toy example and compare it against existent self-calibration schemes, Wiener filter solutions, and Markov chain Monte Carlo sampling. We conclude that the method is able to keep up in accuracy with the best self-calibration methods and serves as a noniterative alternative to them.

The Effect of Simplified Bonding Agents on the Bond Strength to Dentin of Self-Activated Dual-Cure Resin Cements

DTIC Science & Technology

2013-04-26

versions of the self-etch adhesives on the market are one-step systems where the acidified primer and adhesive monomer are mixed together and placed in a...Figure 3 - Adhesive Classification B. Effects of Simplification at the Microscopic level Using restorative systems with simplified...bonding failures when self-cured “build-up” composites were bonded with simplified adhesive systems (Swift, 1999). They were alerted to potential

Light-Cured Self-Etch Adhesives Undergo Hydroxyapatite-Triggered Self-Cure

PubMed Central

Liu, Y.; Bai, X.; Liu, Y.W.; Wang, Y.

2015-01-01

Light cure is a popular mode of curing for dental adhesives. However, it suffers from inadequate light delivery when the restoration site is less accessible, in which case a self-cure mechanism is desirable to salvage any compromised polymerization. We previously reported a novel self-cure system mediated by ethyl 4-(dimethylamino)-benzoate (4E) and hydroxyapatite (HAp). The present work aims to investigate if such self-cure phenomenon takes place in adhesives that underwent prior inadequate light cure and to elucidate if HAp released from the dental etching process is sufficient to trigger it. Model self-etch adhesives were formulated with various components, including bis[2-methacryloyloxy)ethyl]-phosphate (2MP) as acidic monomer and trimethylbenzoyl-diphenylphosphine oxide (TPO) as photoinitiator. In vitro evolution of degree of conversion (DC) of HAp-incorporated adhesives was monitored by infrared spectroscopy during light irradiation and dark storage. Selected adhesives were allowed to etch and extract HAp from enamel, light-cured in situ, and stored in the dark, after which Raman line mapping was used to obtain spatially resolved DC across the enamel-resin interface. Results showed that TPO+4E adhesives reached DC similar to TPO-only counterparts upon completion of light irradiation but underwent another round of initiation that boosted DC to ~100% regardless of HAp level or prior light exposure. When applied to enamel, TPO-only adhesives had ~80% DC in resin, which gradually descended to ~50% in enamel, whereas TPO+4E adhesives consistently scored ~80% DC across the enamel-resin interface. These observations suggest that polymerization of adhesives that underwent insufficient light cure is salvaged by the novel self-cure mechanism, and such salvaging effect can be triggered by HAp released from dental substrate during the etching process. PMID:26635279

Light-Cured Self-Etch Adhesives Undergo Hydroxyapatite-Triggered Self-Cure.

PubMed

Liu, Y; Bai, X; Liu, Y W; Wang, Y

2016-03-01

Light cure is a popular mode of curing for dental adhesives. However, it suffers from inadequate light delivery when the restoration site is less accessible, in which case a self-cure mechanism is desirable to salvage any compromised polymerization. We previously reported a novel self-cure system mediated by ethyl 4-(dimethylamino)-benzoate (4E) and hydroxyapatite (HAp). The present work aims to investigate if such self-cure phenomenon takes place in adhesives that underwent prior inadequate light cure and to elucidate if HAp released from the dental etching process is sufficient to trigger it. Model self-etch adhesives were formulated with various components, including bis[2-methacryloyloxy)ethyl]-phosphate (2MP) as acidic monomer and trimethylbenzoyl-diphenylphosphine oxide (TPO) as photoinitiator. In vitro evolution of degree of conversion (DC) of HAp-incorporated adhesives was monitored by infrared spectroscopy during light irradiation and dark storage. Selected adhesives were allowed to etch and extract HAp from enamel, light-cured in situ, and stored in the dark, after which Raman line mapping was used to obtain spatially resolved DC across the enamel-resin interface. Results showed that TPO+4E adhesives reached DC similar to TPO-only counterparts upon completion of light irradiation but underwent another round of initiation that boosted DC to ~100% regardless of HAp level or prior light exposure. When applied to enamel, TPO-only adhesives had ~80% DC in resin, which gradually descended to ~50% in enamel, whereas TPO+4E adhesives consistently scored ~80% DC across the enamel-resin interface. These observations suggest that polymerization of adhesives that underwent insufficient light cure is salvaged by the novel self-cure mechanism, and such salvaging effect can be triggered by HAp released from dental substrate during the etching process. © International & American Associations for Dental Research 2015.

HLH Rotor Blade Manufacturing Technology Development Report

DTIC Science & Technology

1977-09-01

30 Tool Design and Fabrication . . . . . .. 30 Tool Concepts and Materials . . . . . . . 30 Autoclave Cure - Plastic Molds . . . 30...Materials Autoclave Cure - Plastic MoiJ.- The Double Coke Bottle specimen (Figure 13) was layed-up on a bean bag and cured in a fiberglass tool in...lower airfoil) was made from a foam material, mounted on a common base, and covered with plastic coating to give a hard working surface. This is

The Development of a High-Throughput/Combinatorial Workflow for the Study of Porous Polymer Networks

DTIC Science & Technology

2012-04-05

poragen composition , poragen level, and cure temperature. A total of 216 unique compositions were prepared. Changes in opacity of the blends as they cured...allowed for the identification of compositional variables and process variables that enabled the production of porous networks. Keywords: high...in polymer network cross-link density,poragen composition , poragen level, and cure temperature. A total of 216 unique compositions were prepared

UV dichroic coatings on metallic reflectors

NASA Astrophysics Data System (ADS)

Raghunath, C.; Babu, N. J.; chandran, K. M.

2008-05-01

The work presented here explains the design and deposition process of dichroic coating on metallic reflectors developed for UV curing systems. Special designs are adopted to achieve the spectral band and optimized to suit to the requirements. A mirror, which reflects the UV radiation (220 - 400 nm) and absorbs visible and infrared radiation (400 - 2000nm), is described in detail.

Visual Hybrid Development Learning System (VHDLS) Framework for Children with Autism

ERIC Educational Resources Information Center

Banire, Bilikis; Jomhari, Nazean; Ahmad, Rodina

2015-01-01

The effect of education on children with autism serves as a relative cure for their deficits. As a result of this, they require special techniques to gain their attention and interest in learning as compared to typical children. Several studies have shown that these children are visual learners. In this study, we proposed a Visual Hybrid…

Chemoviscosity modeling for thermosetting resins

NASA Technical Reports Server (NTRS)

Tiwari, S. N.; Hou, T. H.; Bai, J. M.

1985-01-01

A chemoviscosity model, which describes viscosity rise profiles accurately under various cure cycles, and correlates viscosity data to the changes of physical properties associated with structural transformations of the thermosetting resin system during cure, was established. Work completed on chemoviscosity modeling for thermosetting resins is reported.

Lamivudine and Zidovudine

MedlinePlus

... the combination of lamivudine and zidovudine does not cure HIV, it may decrease your chance of developing acquired ... prescribed by your doctor.Lamivudine and zidovudine controls HIV infection but does not cure it. Continue to take lamivudine and zidovudine even ...

Lamb wave propagation in Z-pin reinforced co-cured composite pi-joints

NASA Astrophysics Data System (ADS)

Swenson, Eric D.; Soni, Som R.; Kapoor, Hitesh

2010-04-01

This paper presents an initial study on Lamb wave propagation characteristics in z-pin reinforced, co-cured composite pi-joints for the purposes of structural health monitoring (SHM). Pi-joint test articles were designed and created to replicate a co-cured, all composite skin-spar joint found within a typical aircraft wing structure. Because pi-joints exhibit various complex damage modes, formal studies are required if SHM systems are to be developed to monitor these types of joints for potential damage. Experiments were conducted on a undamaged (healthy) and damaged test articles where Lamb waves were excited using one lead zirconate titanate (PZT) transducer. A three-dimensional (3D) scanning laser Doppler vibrometer (LDV) was used to collect high-density scans of both the in-plane and out-of-plane velocity measurements. In the damaged test article, where delamination, matrix cracking, and fiber breakage can clearly be seen, changes in both the fundamental antisymmetric A0 and symmetric S0 Lamb wave modes are apparent. In both test articles, the effects of narrow geometry, discontinuity due to the attachment of the web, and thickness has detectable effects on Lamb wave propagation. From the comparisons between Lamb waves propagating through the undamaged and damaged test articles, it is clear that damage can be detected using Lamb waves in z-pin reinforced, co-cured composite pi-joints for this case of extensive damage.

Modeling the curing process of thick-section autoclave cured composites

NASA Technical Reports Server (NTRS)

Loos, A. C.; Dara, P. H.

1985-01-01

Temperature gradients are significant during cure of large area, thick-section composites. Such temperature gradients result in nonuniformly cured parts with high void contents, poor ply compaction, and variations in the fiber/resin distribution. A model was developed to determine the temperature distribution in thick-section autoclave cured composites. Using the model, long with temperature measurements obtained from the thick-section composites, the effects of various processing parameters on the thermal response of the composites were examined. A one-dimensional heat transfer model was constructed for the composite-tool assembly. The governing differential equations and associated boundary conditions describing one-dimensional unsteady heat-conduction in the composite, tool plate, and pressure plate are given. Solution of the thermal model was obtained using an implicit finite difference technique.

Effect of water curing duration on strength behaviour of portland composite cement (PCC) mortar

NASA Astrophysics Data System (ADS)

Caronge, M. A.; Tjaronge, M. W.; Hamada, H.; Irmawaty, R.

2017-11-01

Cement manufacturing of Indonesia has been introduced Portland Composite Cement (PCC) to minimize the rising production cost of cement which contains 80% clinker and 20% mineral admixture. A proper curing is very important when the cement contains mineral admixture materials. This paper reports the results of an experimental study conducted to evaluate the effect of water curing duration on strength behaviour of PCC mortar. Mortar specimens with water to cement ratio of (W/C) 0.5 were casted. Compressive strength, flexural strength and concrete resistance were tested at 7, 28 and 91 days cured water. The results indicated that water curing duration is essential to continue the pozzolanic reaction in mortar which contributes to the development of strength of mortar made with PCC.

Elastic properties, reaction kinetics, and structural relaxation of an epoxy resin polymer during cure

NASA Astrophysics Data System (ADS)

Heili, Manon; Bielawski, Andrew; Kieffer, John

The cure kinetics of a DGEBA/DETA epoxy is investigated using concurrent Raman and Brillouin light scattering. Raman scattering allows us to monitor the in-situ reaction and quantitatively assess the degree of cure. Brillouin scattering yields the elastic properties of the system, providing a measure of network connectivity. We show that the adiabatic modulus evolves non-uniquely as a function of cure degree, depending on the cure temperature and the molar ratio of the epoxy. Two mechanisms contribute to the increase in the elastic modulus of the material during curing. First, there is the formation of covalent bonds in the network during the curing process. Second, following bond formation, the epoxy undergoes structural relaxation toward an optimally packed network configuration, enhancing non-bonded interactions. We investigate to what extent the non-bonded interaction contribution to structural rigidity in cross-linked polymers is reversible, and to what extent it corresponds to the difference between adiabatic and isothermal moduli obtained from static tensile, i.e. the so-called relaxational modulus. To this end, we simultaneously measure the adiabatic and isothermal elastic moduli as a function of applied strain and deformation rate.

Cure kinetics, morphologies, and mechanical properties of thermoplastic/MWCNT modified multifunctional glassy epoxies prepared via continuous reaction methods

NASA Astrophysics Data System (ADS)

Cheng, Xiaole

The primary goal of this dissertation is to develop a novel continuous reactor method to prepare partially cured epoxy prepolymers for aerospace prepreg applications with the aim of replacing traditional batch reactors. Compared to batch reactors, the continuous reactor is capable of solubilizing and dispersing a broad range of additives including thermoplastic tougheners, stabilizers, nanoparticles and curatives and advancing epoxy molecular weights and viscosities while reducing energy consumption. In order to prove this concept, polyethersulfone (PES) modified 4, 4'-diaminodiphenylsulfone (44DDS)/tetraglycidyl-4, 4'-diaminodiphenylmethane (TGDDM) epoxy prepolymers were firstly prepared using both continuous reactor and batch reactor methods. Kinetic studies confirmed the chain extension reaction in the continuous reactor is similar to the batch reactor, and the molecular weights and viscosities of prepolymers were readily controlled through reaction kinetics. Atomic force microscopy (AFM) confirmed similar cured network morphologies for formulations prepared from batch and continuous reactors. Additionally tensile strength, tensile modulus and fracture toughness analyses concluded mechanical properties of cured epoxy matrices produced from both reactors were equivalent. Effects of multifunctional epoxy compositions on thermoplastics phase-separated morphologies were systematically studied using a combination of AFM with nanomechanical mapping, spectroscopic and calorimetric techniques to provide new insights to tailor cured reaction induced phase separation (CRIPS) in multifunctional epoxy blend networks. Furthermore, how resultant crosslinked glassy polymer network and phase-separated morphologies correlated with mechanical properties are discussed in detail. Multiwall carbon nanotube (MWCNT)/TGDDM epoxy prepolymers were further prepared by combining the successful strategies for advancing epoxy chemistries and dispersing nanotubes using the continuous reactor. Optical microscopy (OM) and scanning electron microscopy (SEM) were used to characterize the MWCNT dispersion states and stabilization in epoxy prepolymer matrix after continuous process and during curing cycles. Additionally, electrical conductivities and mechanical properties of final cured MWCNT/TGDDM composites were measured and discussed in view of their corresponding MWCNT dispersion states. Ternary blends of MWCNT reinforced thermoplastic/epoxy prepolymers were prepared by the continuous reactor. Influence of MWCNT on the CRIPS mechanism and the cured morphologies were systematically investigated using SEM and rheological analysis. Incorporation of MWCNT in thermoplastic/epoxy matrices can lead to a morphological transformation from phase inverted, to co-continuous, and to droplet dispersed morphology. In additional, dynamic mechanical analysis revealed the heterogeneity of MWCNT dispersion in thermoplastic/thermosets systems.

Pressure injection of solubilized benomyl for prevention and cure of oak wilt

Treesearch

Thomas W. Jones; Garold F. Gregory; Percy McWain

1973-01-01

A preliminary evaluation of the effectiveness of injecting solubilized benomyl into oaks for prevention or cure of oak wilt disease is presented. Symptom development was greatly reduced or prevented in trees injected with fungicide before inoculation. Symptom development was markedly arrested in diseased trees by fungicide injected before more than 10 percent of the...

Stress Relaxation in Epoxy Thermosets via a Ferrocene-Based Amine Curing Agent

DOE PAGES

Jones, Brad H.; Wheeler, David R.; Black, Hayden T.; ...

2017-06-29

Physical stress relaxation in rubbery, thermoset polymers is limited by cross-links, which impede segmental motion and restrict relaxation to network defects, such as chain ends. In parallel, the cure shrinkage associated with thermoset polymerizations leads to the development of internal residual stress that cannot be effectively relaxed. Recent strategies have reduced or eliminated such cure stress in thermoset polymers largely by exploiting chemical relaxation processes, wherein temporary cross-links or otherwise transient bonds are incorporated into the polymer network. In this paper, we explore an alternative approach, wherein physical relaxation is enhanced by the incorporation of organometallic sandwich moieties into themore » backbone of the polymer network. A standard epoxy resin is cured with a diamine derivative of ferrocene and compared to conventional diamine curing agents. The ferrocene-based thermoset is clearly distinguished from the conventional materials by reduced cure stress with increasing cure temperature as well as unique stress relaxation behavior above its glass transition in the fully cured state. The relaxation experiments exhibit features characteristic of a physical relaxation process. Furthermore, the cure stress is observed to vanish precipitously upon deliberate introduction of network defects through an increasing imbalance of epoxy and amine functional groups. Finally, we postulate that these beneficial properties arise from fluxional motion of the cyclopentadienyl ligands on the polymer backbone.« less

Stress Relaxation in Epoxy Thermosets via a Ferrocene-Based Amine Curing Agent

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

Jones, Brad H.; Wheeler, David R.; Black, Hayden T.

Physical stress relaxation in rubbery, thermoset polymers is limited by cross-links, which impede segmental motion and restrict relaxation to network defects, such as chain ends. In parallel, the cure shrinkage associated with thermoset polymerizations leads to the development of internal residual stress that cannot be effectively relaxed. Recent strategies have reduced or eliminated such cure stress in thermoset polymers largely by exploiting chemical relaxation processes, wherein temporary cross-links or otherwise transient bonds are incorporated into the polymer network. In this paper, we explore an alternative approach, wherein physical relaxation is enhanced by the incorporation of organometallic sandwich moieties into themore » backbone of the polymer network. A standard epoxy resin is cured with a diamine derivative of ferrocene and compared to conventional diamine curing agents. The ferrocene-based thermoset is clearly distinguished from the conventional materials by reduced cure stress with increasing cure temperature as well as unique stress relaxation behavior above its glass transition in the fully cured state. The relaxation experiments exhibit features characteristic of a physical relaxation process. Furthermore, the cure stress is observed to vanish precipitously upon deliberate introduction of network defects through an increasing imbalance of epoxy and amine functional groups. Finally, we postulate that these beneficial properties arise from fluxional motion of the cyclopentadienyl ligands on the polymer backbone.« less

Bond performance of "Touch and Cure" adhesives on resin core systems.

PubMed

Kadowaki, Yoshitaka; Kakuda, Shinichi; Kawano, Shimpei; Katsumata, Aiichiro; Ting, Shihchun; Hoshika, Shuhei; Ikeda, Takatsumi; Tanaka, Toru; Carvalho, Ricardo Marinsde; Sano, Hidehiko

2016-01-01

The purpose of this study was to compare the micro-tensile bond strength (µTBS) of three resin core composites to dentin and to examine the bonded interface of the composites. One experimental TDK-03(TD) and, two commercial, DC core Automix One (DC) and Unifil core EM(UN) were used. Flat dentin surfaces of human molars were exposed using #600 SiC paper and bonded with the respective adhesive of each system. After bonding, the composites were built up on the surfaces and cured under two conditions: "light condition" or "dark condition". µTBSs (MPa) in the light condition were: TD; 60.02±17.08, DC; 38.21±13.70, and UN; 29.50±9.71; in the dark condition: TD; 54.62±17.11, DC; 8.40±4.81, and UN; 9.47±6.56. Dark curing negatively affected the bond strength of the two commercial resin-core materials. The experimental material was not affected by the curing conditions.

Abacavir, Lamivudine, and Zidovudine

MedlinePlus

... combination of abacavir, lamivudine and zidovudine does not cure HIV, it may decrease your chance of developing acquired ... doctor.Abacavir, lamivudine, and zidovudine helps to control HIV infection but does not cure it. Continue to take abacavir, lamivudine, and zidovudine ...

Optimal cure cycle design for autoclave processing of thick composites laminates: A feasibility study

NASA Technical Reports Server (NTRS)

Hou, Jean W.

1985-01-01

The thermal analysis and the calculation of thermal sensitivity of a cure cycle in autoclave processing of thick composite laminates were studied. A finite element program for the thermal analysis and design derivatives calculation for temperature distribution and the degree of cure was developed and verified. It was found that the direct differentiation was the best approach for the thermal design sensitivity analysis. In addition, the approach of the direct differentiation provided time histories of design derivatives which are of great value to the cure cycle designers. The approach of direct differentiation is to be used for further study, i.e., the optimal cycle design.

Composite Cure Process Modeling and Simulations using COMPRO(Registered Trademark) and Validation of Residual Strains using Fiber Optics Sensors

NASA Technical Reports Server (NTRS)

Sreekantamurthy, Thammaiah; Hudson, Tyler B.; Hou, Tan-Hung; Grimsley, Brian W.

2016-01-01

Composite cure process induced residual strains and warping deformations in composite components present significant challenges in the manufacturing of advanced composite structure. As a part of the Manufacturing Process and Simulation initiative of the NASA Advanced Composite Project (ACP), research is being conducted on the composite cure process by developing an understanding of the fundamental mechanisms by which the process induced factors influence the residual responses. In this regard, analytical studies have been conducted on the cure process modeling of composite structural parts with varied physical, thermal, and resin flow process characteristics. The cure process simulation results were analyzed to interpret the cure response predictions based on the underlying physics incorporated into the modeling tool. In the cure-kinetic analysis, the model predictions on the degree of cure, resin viscosity and modulus were interpreted with reference to the temperature distribution in the composite panel part and tool setup during autoclave or hot-press curing cycles. In the fiber-bed compaction simulation, the pore pressure and resin flow velocity in the porous media models, and the compaction strain responses under applied pressure were studied to interpret the fiber volume fraction distribution predictions. In the structural simulation, the effect of temperature on the resin and ply modulus, and thermal coefficient changes during curing on predicted mechanical strains and chemical cure shrinkage strains were studied to understand the residual strains and stress response predictions. In addition to computational analysis, experimental studies were conducted to measure strains during the curing of laminated panels by means of optical fiber Bragg grating sensors (FBGs) embedded in the resin impregnated panels. The residual strain measurements from laboratory tests were then compared with the analytical model predictions. The paper describes the cure process procedures and residual strain predications, and discusses pertinent experimental results from the validation studies.

Lethal acute demyelinization with encephalo-myelitis as a complication of cured Cushing's disease.

PubMed

Chevalier, N; Hieronimus, S; Vandenbos, F; Delmont, E; Cua, E; Cherick, F; Paquis, P; Michiels, J-F; Fenichel, P; Brucker-Davis, F

2010-12-01

Cushing's disease is usually associated with higher mortality rate, especially from cardiovascular causes. Development or exacerbation of autoimmune or inflammatory diseases is known to occur in patients with hypercortisolism after cure. We report for the first time a 34-year old woman with a psychiatric background, who developed four months after the surgical cure of Cushing's disease an acute disseminated encephalomyelitis (ADEM) presenting initially as a psychiatric illness. We hypothesize that the recent correction of hypercortisolism triggered ADEM and that the atypical presentation, responsible for diagnosis delay, led to the death of this patient. Copyright © 2010 Elsevier Masson SAS. All rights reserved.

Two-layer anti-reflection strategies for implant applications

NASA Astrophysics Data System (ADS)

Guerrero, Douglas J.; Smith, Tamara; Kato, Masakazu; Kimura, Shigeo; Enomoto, Tomoyuki

2006-03-01

A two-layer bottom anti-reflective coating (BARC) concept in which a layer that develops slowly is coated on top of a bottom layer that develops more rapidly was demonstrated. Development rate control was achieved by selection of crosslinker amount and BARC curing conditions. A single-layer BARC was compared with the two-layer BARC concept. The single-layer BARC does not clear out of 200-nm deep vias. When the slower developing single-layer BARC was coated on top of the faster developing layer, the vias were cleared. Lithographic evaluation of the two-layer BARC concept shows the same resolution advantages as the single-layer system. Planarization properties of a two-layer BARC system are better than for a single-layer system, when comparing the same total nominal thicknesses.

Sensor-model prediction, monitoring and in-situ control of liquid RTM advanced fiber architecture composite processing

NASA Technical Reports Server (NTRS)

Kranbuehl, D.; Kingsley, P.; Hart, S.; Loos, A.; Hasko, G.; Dexter, B.

1992-01-01

In-situ frequency dependent electromagnetic sensors (FDEMS) and the Loos resin transfer model have been used to select and control the processing properties of an epoxy resin during liquid pressure RTM impregnation and cure. Once correlated with viscosity and degree of cure the FDEMS sensor monitors and the RTM processing model predicts the reaction advancement of the resin, viscosity and the impregnation of the fabric. This provides a direct means for predicting, monitoring, and controlling the liquid RTM process in-situ in the mold throughout the fabrication process and the effects of time, temperature, vacuum and pressure. Most importantly, the FDEMS-sensor model system has been developed to make intelligent decisions, thereby automating the liquid RTM process and removing the need for operator direction.

NASA/aircraft industry standard specification for graphite fiber toughened thermoset resin composite material

NASA Technical Reports Server (NTRS)

1985-01-01

A standard specification for a selected class of graphite fiber/toughened thermoset resin matrix material was developed through joint NASA/Aircraft Industry effort. This specification was compiled to provide uniform requirements and tests for qualifying prepreg systems and for acceptance of prepreg batches. The specification applies specifically to a class of composite prepreg consisting of unidirectional graphite fibers impregnated with a toughened thermoset resin that produce laminates with service temperatures from -65 F to 200 F when cured at temperatures below or equal to 350 F. The specified prepreg has a fiber areal weight of 145 g sq m. The specified tests are limited to those required to set minimum standards for the uncured prepreg and cured laminates, and are not intended to provide design allowable properties.

Comparative bonding ability to dentin of a universal adhesive system and monomer conversion as functions of extended light curing times and storage.

PubMed

Sampaio, Paula Costa Pinheiro; Kruly, Paula de Castro; Ribeiro, Clara Cabral; Hilgert, Leandro Augusto; Pereira, Patrícia Nóbrega Rodrigues; Scaffa, Polliana Mendes Candia; Di Hipólito, Vinicius; D'Alpino, Paulo Henrique Perlatti; Garcia, Fernanda Cristina Pimentel

2017-11-01

The purpose of this in vitro study was to evaluate the bonding ability and monomer conversion of a universal adhesive system applied to dentin as functions of different curing times and storage. The results were compared among a variety of commercial adhesives. Flat superficial dentin surfaces were exposed on human molars and assigned into one of the following adhesives (n = 15): total-etch Adper Single Bond 2 (SB) and Optibond Solo Plus (OS), self-etch Optibond All in One (OA) and Clearfil SE Bond (CSE), and Scotchbond Universal Adhesive in self-etch mode (SU). The adhesives were applied following the manufacturers' instructions and cured for 10, 20, or 40s. Specimens were processed for the microtensile bond strength (µTBS) test in accordance with the non-trimming technique and tested after 24h and 2 years. The fractured specimens were classified under scanning electron microscopy (SEM). Infrared (IR) spectra were obtained and monomer conversion (%) was calculated by comparing the aliphatic-to-aromatic IR absorption peak ratio before and after polymerization (n=5). Data were analyzed by 2-way ANOVA/Tukey's tests (α = 0.05). At 24-h evaluation, OA and CSE presented similar bond strength means irrespective of the curing time, whereas SB and SU exhibited significantly higher means when cured for 40s as did OS when cured for 20 or 40s (p < 0.05). At 2-year evaluation, only OA exhibited significantly higher bond strength when cured for 20 and 40s (p < 0.05). When the evaluation times were compared, OA also exhibited the same bonding ability when cured for longer periods of time (20 and 40s). All of the adhesives tested exhibited significantly lower monomer conversion when photoactivated according to the manufacturers' instructions (10s). Higher monomer conversions obtained with longer light exposure allow only higher immediate bond strength for most of the adhesives tested. After 2-year storage, only the self-etching adhesive Optibond All-In-One exhibited the same bonding ability when cured for longer periods of time. Copyright © 2017 Elsevier Ltd. All rights reserved.

Effect of cementitious permanent formwork on moisture field of internal-cured concrete under drying

NASA Astrophysics Data System (ADS)

Wang, Jiahe; Zhang, Jun; Ding, Xiaoping; Zhang, Jiajia

2018-02-01

Drying shrinkage of concrete may still be the main source of cracking in concrete structures, even though the autogenous shrinkage of concrete can be effectively reduced by using internal curing. In the present paper, the effect of internal curing with pre-soaked lightweight aggregate and engineered cementitious composite permanent formwork (ECC-PF) on a moisture distribution in three kinds of concrete in a drying environment are investigated from both aspects of experiments and theoretical modeling. The test results show that the combination use of ECC-PF and internal curing can well maintain the humidity at a relatively high level not only at a place far from drying surface, but also at a place close to the drying surfaces. The developed model can well catch the characteristics of the moisture distribution in concrete under drying and the impacts of internal curing and ECC-PF can well be reflected as well. The model can be used for the design of concrete structures with combination use of internal curing and permanent formwork.

Development of a Wireless Brain Implant: The Telemetric Electrode Array System (TEAS) Project

DTIC Science & Technology

2001-10-25

8 array connected to an electronic system through a special polyimide flexible cable. The neuronal signals recorded by the electrode array at 1 mm...deposition prior to applying an insulation coating of glass using electron-beam deposition or a biocompatible epoxy through a dipping process. In the case...layer can be made relatively easily, by melting and cooling glass powder or curing biocompatible epoxy, it was desirable to simplify the process and

Use of Cox's Cure Model to Establish Clinical Determinants of Long-Term Disease-Free Survival in Neoadjuvant-Chemotherapy-Treated Breast Cancer Patients without Pathologic Complete Response.

PubMed

Asano, Junichi; Hirakawa, Akihiro; Hamada, Chikuma; Yonemori, Kan; Hirata, Taizo; Shimizu, Chikako; Tamura, Kenji; Fujiwara, Yasuhiro

2013-01-01

In prognostic studies for breast cancer patients treated with neoadjuvant chemotherapy (NAC), the ordinary Cox proportional-hazards (PH) model has been often used to identify prognostic factors for disease-free survival (DFS). This model assumes that all patients eventually experience relapse or death. However, a subset of NAC-treated breast cancer patients never experience these events during long-term follow-up (>10 years) and may be considered clinically "cured." Clinical factors associated with cure have not been studied adequately. Because the ordinary Cox PH model cannot be used to identify such clinical factors, we used the Cox PH cure model, a recently developed statistical method. This model includes both a logistic regression component for the cure rate and a Cox regression component for the hazard for uncured patients. The purpose of this study was to identify the clinical factors associated with cure and the variables associated with the time to recurrence or death in NAC-treated breast cancer patients without a pathologic complete response, by using the Cox PH cure model. We found that hormone receptor status, clinical response, human epidermal growth factor receptor 2 status, histological grade, and the number of lymph node metastases were associated with cure.

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

Jones, Brad H.; Wheeler, David R.; Black, Hayden T.

Physical stress relaxation in rubbery, thermoset polymers is limited by cross-links, which impede segmental motion and restrict relaxation to network defects, such as chain ends. In parallel, the cure shrinkage associated with thermoset polymerizations leads to the development of internal residual stress that cannot be effectively relaxed. Recent strategies have reduced or eliminated such cure stress in thermoset polymers largely by exploiting chemical relaxation processes, wherein temporary cross-links or otherwise transient bonds are incorporated into the polymer network. In this paper, we explore an alternative approach, wherein physical relaxation is enhanced by the incorporation of organometallic sandwich moieties into themore » backbone of the polymer network. A standard epoxy resin is cured with a diamine derivative of ferrocene and compared to conventional diamine curing agents. The ferrocene-based thermoset is clearly distinguished from the conventional materials by reduced cure stress with increasing cure temperature as well as unique stress relaxation behavior above its glass transition in the fully cured state. The relaxation experiments exhibit features characteristic of a physical relaxation process. Furthermore, the cure stress is observed to vanish precipitously upon deliberate introduction of network defects through an increasing imbalance of epoxy and amine functional groups. Finally, we postulate that these beneficial properties arise from fluxional motion of the cyclopentadienyl ligands on the polymer backbone.« less

3D-Printing of Meso-structurally Ordered Carbon Fiber/Polymer Composites with Unprecedented Orthotropic Physical Properties

NASA Astrophysics Data System (ADS)

Lewicki, James P.; Rodriguez, Jennifer N.; Zhu, Cheng; Worsley, Marcus A.; Wu, Amanda S.; Kanarska, Yuliya; Horn, John D.; Duoss, Eric B.; Ortega, Jason M.; Elmer, William; Hensleigh, Ryan; Fellini, Ryan A.; King, Michael J.

2017-03-01

Here we report the first example of a class of additively manufactured carbon fiber reinforced composite (AMCFRC) materials which have been achieved through the use of a latent thermal cured aromatic thermoset resin system, through an adaptation of direct ink writing (DIW) 3D-printing technology. We have developed a means of printing high performance thermoset carbon fiber composites, which allow the fiber component of a resin and carbon fiber fluid to be aligned in three dimensions via controlled micro-extrusion and subsequently cured into complex geometries. Characterization of our composite systems clearly show that we achieved a high order of fiber alignment within the composite microstructure, which in turn allows these materials to outperform equivalently filled randomly oriented carbon fiber and polymer composites. Furthermore, our AM carbon fiber composite systems exhibit highly orthotropic mechanical and electrical responses as a direct result of the alignment of carbon fiber bundles in the microscale which we predict will ultimately lead to the design of truly tailorable carbon fiber/polymer hybrid materials having locally programmable complex electrical, thermal and mechanical response.

3D-Printing of Meso-structurally Ordered Carbon Fiber/Polymer Composites with Unprecedented Orthotropic Physical Properties

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

Lewicki, James P.; Rodriguez, Jennifer N.; Zhu, Cheng

Here we report the first example of a class of additively manufactured carbon fiber reinforced composite (AMCFRC) materials which have been achieved through the use of a latent thermal cured aromatic thermoset resin system, through an adaptation of direct ink writing (DIW) 3D-printing technology. We have developed a means of printing high performance thermoset carbon fiber composites, which allow the fiber component of a resin and carbon fiber fluid to be aligned in three dimensions via controlled micro-extrusion and subsequently cured into complex geometries. Characterization of our composite systems clearly show that we achieved a high order of fiber alignmentmore » within the composite microstructure, which in turn allows these materials to outperform equivalently filled randomly oriented carbon fiber and polymer composites. Moreover, our AM carbon fiber composite systems exhibit highly orthotropic mechanical and electrical responses as a direct result of the alignment of carbon fiber bundles in the microscale which we predict will ultimately lead to the design of truly tailorable carbon fiber/polymer hybrid materials having locally programmable complex electrical, thermal and mechanical response.« less

3D-Printing of Meso-structurally Ordered Carbon Fiber/Polymer Composites with Unprecedented Orthotropic Physical Properties

DOE PAGES

Lewicki, James P.; Rodriguez, Jennifer N.; Zhu, Cheng; ...

2017-03-06

Here we report the first example of a class of additively manufactured carbon fiber reinforced composite (AMCFRC) materials which have been achieved through the use of a latent thermal cured aromatic thermoset resin system, through an adaptation of direct ink writing (DIW) 3D-printing technology. We have developed a means of printing high performance thermoset carbon fiber composites, which allow the fiber component of a resin and carbon fiber fluid to be aligned in three dimensions via controlled micro-extrusion and subsequently cured into complex geometries. Characterization of our composite systems clearly show that we achieved a high order of fiber alignmentmore » within the composite microstructure, which in turn allows these materials to outperform equivalently filled randomly oriented carbon fiber and polymer composites. Moreover, our AM carbon fiber composite systems exhibit highly orthotropic mechanical and electrical responses as a direct result of the alignment of carbon fiber bundles in the microscale which we predict will ultimately lead to the design of truly tailorable carbon fiber/polymer hybrid materials having locally programmable complex electrical, thermal and mechanical response.« less

3D-Printing of Meso-structurally Ordered Carbon Fiber/Polymer Composites with Unprecedented Orthotropic Physical Properties.

PubMed

Lewicki, James P; Rodriguez, Jennifer N; Zhu, Cheng; Worsley, Marcus A; Wu, Amanda S; Kanarska, Yuliya; Horn, John D; Duoss, Eric B; Ortega, Jason M; Elmer, William; Hensleigh, Ryan; Fellini, Ryan A; King, Michael J

2017-03-06

Here we report the first example of a class of additively manufactured carbon fiber reinforced composite (AMCFRC) materials which have been achieved through the use of a latent thermal cured aromatic thermoset resin system, through an adaptation of direct ink writing (DIW) 3D-printing technology. We have developed a means of printing high performance thermoset carbon fiber composites, which allow the fiber component of a resin and carbon fiber fluid to be aligned in three dimensions via controlled micro-extrusion and subsequently cured into complex geometries. Characterization of our composite systems clearly show that we achieved a high order of fiber alignment within the composite microstructure, which in turn allows these materials to outperform equivalently filled randomly oriented carbon fiber and polymer composites. Furthermore, our AM carbon fiber composite systems exhibit highly orthotropic mechanical and electrical responses as a direct result of the alignment of carbon fiber bundles in the microscale which we predict will ultimately lead to the design of truly tailorable carbon fiber/polymer hybrid materials having locally programmable complex electrical, thermal and mechanical response.

3D-Printing of Meso-structurally Ordered Carbon Fiber/Polymer Composites with Unprecedented Orthotropic Physical Properties

PubMed Central

Lewicki, James P.; Rodriguez, Jennifer N.; Zhu, Cheng; Worsley, Marcus A.; Wu, Amanda S.; Kanarska, Yuliya; Horn, John D.; Duoss, Eric B.; Ortega, Jason M.; Elmer, William; Hensleigh, Ryan; Fellini, Ryan A.; King, Michael J.

2017-01-01

Here we report the first example of a class of additively manufactured carbon fiber reinforced composite (AMCFRC) materials which have been achieved through the use of a latent thermal cured aromatic thermoset resin system, through an adaptation of direct ink writing (DIW) 3D-printing technology. We have developed a means of printing high performance thermoset carbon fiber composites, which allow the fiber component of a resin and carbon fiber fluid to be aligned in three dimensions via controlled micro-extrusion and subsequently cured into complex geometries. Characterization of our composite systems clearly show that we achieved a high order of fiber alignment within the composite microstructure, which in turn allows these materials to outperform equivalently filled randomly oriented carbon fiber and polymer composites. Furthermore, our AM carbon fiber composite systems exhibit highly orthotropic mechanical and electrical responses as a direct result of the alignment of carbon fiber bundles in the microscale which we predict will ultimately lead to the design of truly tailorable carbon fiber/polymer hybrid materials having locally programmable complex electrical, thermal and mechanical response. PMID:28262669

Effect of poly(ethylene oxide) homopolymer and two different poly(ethylene oxide-b-poly(propylene oxide)-b-poly(ethylene oxide) triblock copolymers on morphological, optical, and mechanical properties of nanostructured unsaturated polyester.

PubMed

Builes, Daniel H; Hernández-Ortiz, Juan P; Corcuera, Ma Angeles; Mondragon, Iñaki; Tercjak, Agnieszka

2014-01-22

Novel nanostructured unsaturated polyester resin-based thermosets, modified with poly(ethylene oxide) (PEO), poly(propylene oxide) (PPO), and two poly(ethylene oxide-b-propylene oxide-b-ethylene oxide) block copolymers (BCP), were developed and analyzed. The effects of molecular weights, blocks ratio, and curing temperatures on the final morphological, optical, and mechanical properties were reported. The block influence on the BCP miscibility was studied through uncured and cured mixtures of unsaturated polyester (UP) resins with PEO and PPO homopolymers having molecular weights similar to molecular weights of the blocks of BCP. The final morphology of the nanostructured thermosetting systems, containing BCP or homopolymers, was investigated, and multiple mechanisms of nanostructuration were listed and explained. By considering the miscibility of each block before and after curing, it was determined that the formation of the nanostructured matrices followed a self-assembly mechanism or a polymerization-induced phase separation mechanism. The miscibility between PEO or PPO blocks with one of two phases of UP matrix was highlighted due to its importance in the final thermoset properties. Relationships between the final morphology and thermoset optical and mechanical properties were examined. The mechanisms and physics behind the morphologies lead toward the design of highly transparent, nanostructured, and toughened thermosetting UP systems.

High-Performance, Low-Energy-Curing Resins.

DTIC Science & Technology

1984-03-01

with a phenolic resin 0. Quinlivan, private communication). Although in this system, the phenolic resin requires curing well above room temperature...34 -4 JOHN T. QUINLIVAN received a B.S. degree from Gonzaga University and M.A. *1 and Ph.D. degrees in chemistry from Princeton University. After

Cure shrinkage in casting resins

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

Spencer, J. Brock

2015-02-01

A method is described whereby the shrinkage of a casting resin can be determined. Values for the shrinkage of several resin systems in frequent use by Sandia have been measured. A discussion of possible methods for determining the stresses generated by cure shrinkage and thermal contraction is also included.

Program Spotlight: CURE Scholars Participate in Annual Mock Grant Review

Cancer.gov

As part of its 2015 Professional Development Workshop, CRCHD held a mock review session for CURE scholars, trainees, and investigators to enhance their understanding of the grant review process and provide insight on successful grant applications.

Release of Self-Healing Agents in a Material: What Happens Next?

PubMed

Lee, Min Wook; Yoon, Sam S; Yarin, Alexander L

2017-05-24

A microfluidic chip-like setup consisting of a vascular system of microchannels alternatingly filled with either a resin monomer or a curing agent is used to study the intrinsic physical healing mechanism in self-healing materials. It is observed that, as a prenotched crack propagates across the chip, the resin and curing agent are released from the damaged channels. Subsequently, both the resin and the curing agent wet the surrounding polydimethylsiloxane (PDMS) matrix and spread over the crack banks until the two blobs come in contact, mix, and polymerize through an organometallic cross-linking reaction. Moreover, the polymerized domains form a system of pillars, which span the crack banks on the opposite side. This "stitching" phenomenon prevents further propagation of the crack.

A Bayesian destructive weighted Poisson cure rate model and an application to a cutaneous melanoma data.

PubMed

Rodrigues, Josemar; Cancho, Vicente G; de Castro, Mário; Balakrishnan, N

2012-12-01

In this article, we propose a new Bayesian flexible cure rate survival model, which generalises the stochastic model of Klebanov et al. [Klebanov LB, Rachev ST and Yakovlev AY. A stochastic-model of radiation carcinogenesis--latent time distributions and their properties. Math Biosci 1993; 113: 51-75], and has much in common with the destructive model formulated by Rodrigues et al. [Rodrigues J, de Castro M, Balakrishnan N and Cancho VG. Destructive weighted Poisson cure rate models. Technical Report, Universidade Federal de São Carlos, São Carlos-SP. Brazil, 2009 (accepted in Lifetime Data Analysis)]. In our approach, the accumulated number of lesions or altered cells follows a compound weighted Poisson distribution. This model is more flexible than the promotion time cure model in terms of dispersion. Moreover, it possesses an interesting and realistic interpretation of the biological mechanism of the occurrence of the event of interest as it includes a destructive process of tumour cells after an initial treatment or the capacity of an individual exposed to irradiation to repair altered cells that results in cancer induction. In other words, what is recorded is only the damaged portion of the original number of altered cells not eliminated by the treatment or repaired by the repair system of an individual. Markov Chain Monte Carlo (MCMC) methods are then used to develop Bayesian inference for the proposed model. Also, some discussions on the model selection and an illustration with a cutaneous melanoma data set analysed by Rodrigues et al. [Rodrigues J, de Castro M, Balakrishnan N and Cancho VG. Destructive weighted Poisson cure rate models. Technical Report, Universidade Federal de São Carlos, São Carlos-SP. Brazil, 2009 (accepted in Lifetime Data Analysis)] are presented.

Processing and properties of carbon nanofibers reinforced epoxy powder composites

NASA Astrophysics Data System (ADS)

Palencia, C.; Mazo, M. A.; Nistal, A.; Rubio, F.; Rubio, J.; Oteo, J. L.

2011-11-01

Commercially available CNFs (diameter 30-300 nm) have been used to develop both bulk and coating epoxy nanocomposites by using a solvent-free epoxy matrix powder. Processing of both types of materials has been carried out by a double-step process consisting in an initial physical premix of all components followed by three consecutive extrusions. The extruded pellets were grinded into powder and sieved. Carbon nanofibers powder coatings were obtained by electrostatic painting of the extruded powder followed by a curing process based in a thermal treatment at 200 °C for 25 min. On the other hand, for obtaining bulk carbon nanofibers epoxy composites, a thermal curing process involving several steps was needed. Gloss and mechanical properties of both nanocomposite coatings and bulk nanocomposites were improved as a result of the processing process. FE-SEM fracture surface microphotographs corroborate these results. It has been assessed the key role played by the dispersion of CNFs in the matrix, and the highly important step that is the processing and curing of the nanocomposites. A processing stage consisted in three consecutive extrusions has reached to nanocomposites free of entanglements neither agglomerates. This process leads to nanocomposite coatings of enhanced properties, as it has been evidenced through gloss and mechanical properties. A dispersion limit of 1% has been determined for the studied system in which a given dispersion has been achieved, as the bending mechanical properties have been increased around 25% compared with the pristine epoxy resin. It has been also demonstrated the importance of the thickness in the nanocomposite, as it involves the curing stage. The complex curing treatment carried out in the case of bulk nanocomposites has reached to reagglomeration of CNFs.

Classification of the fragrant styles and evaluation of the aromatic quality of flue-cured tobacco leaves by machine-learning methods.

PubMed

Gu, Li; Xue, Lichun; Song, Qi; Wang, Fengji; He, Huaqin; Zhang, Zhongyi

2016-12-01

During commercial transactions, the quality of flue-cured tobacco leaves must be characterized efficiently, and the evaluation system should be easily transferable across different traders. However, there are over 3000 chemical compounds in flue-cured tobacco leaves; thus, it is impossible to evaluate the quality of flue-cured tobacco leaves using all the chemical compounds. In this paper, we used Support Vector Machine (SVM) algorithm together with 22 chemical compounds selected by ReliefF-Particle Swarm Optimization (R-PSO) to classify the fragrant style of flue-cured tobacco leaves, where the Accuracy (ACC) and Matthews Correlation Coefficient (MCC) were 90.95% and 0.80, respectively. SVM algorithm combined with 19 chemical compounds selected by R-PSO achieved the best assessment performance of the aromatic quality of tobacco leaves, where the PCC and MSE were 0.594 and 0.263, respectively. Finally, we constructed two online tools to classify the fragrant style and evaluate the aromatic quality of flue-cured tobacco leaf samples. These tools can be accessed at http://bioinformatics.fafu.edu.cn/tobacco .

CaP CURE Initiatives and Projects

PubMed Central

Soule, Howard R

2003-01-01

CaP CURE was founded in 1993 to help find better treatments and a cure for prostate cancer. By reducing the time and complexity required to apply for funding, and by funding many first-time applicants, CaP CURE has attracted a large number of high-level investigators to the field of prostate cancer research. The organization’s Therapy Consortium meets regularly to address major issues that impede progress in clinical development of new treatments for prostate cancer. CaP CURE has also sponsored an initiative to standardize clinical trial design scenarios for the clinical state of rising prostate-specific antigen and intends to present them to the Food and Drug Administration in partnership with the National Dialogue on Cancer. Finally, CaP CURE’s efforts have resulted in a significant increase in federal funding of prostate cancer research programs. PMID:16986049

Curing potential of experimental resin composites with systematically varying amount of bioactive glass: Degree of conversion, light transmittance and depth of cure.

PubMed

Par, Matej; Spanovic, Nika; Bjelovucic, Ruza; Skenderovic, Hrvoje; Gamulin, Ozren; Tarle, Zrinka

2018-06-17

The aim of this work was to investigate the curing potential of an experimental resin composite series with the systematically varying amount of bioactive glass 45S5 by evaluating the degree of conversion, light transmittance and depth of cure. Resin composites based on a Bis-GMA/TEGDMA resin with a total filler load of 70 wt% and a variable amount of bioactive glass (0-40 wt%) were prepared. The photoinitiator system was camphorquinone and ethyl-4-(dimethylamino) benzoate. The degree of conversion and light transmittance were measured by Raman spectroscopy and UV-vis spectroscopy, respectively. The depth of cure was evaluated according to the classical ISO 4049 test. The initial introduction of bioactive glass into the experimental series diminished the light transmittance while the further increase in the bioactive glass amount up to 40 wt% caused minor variations with no clear trend. The curing potential of the experimental composites was similar to or better than that of commercial resin composites. However, unsilanized bioactive glass fillers demonstrated the tendency to diminish both the maximum attainable conversion and the curing efficiency at depth. Experimental composite materials containing bioactive glass showed a clinically acceptable degree of conversion and depth of cure. The degree of conversion and depth of cure were diminished by bioactive glass fillers in a dose-dependent manner, although light transmittance was similar among all of the experimental composites containing 5-40 wt% of bioactive glass. Reduced curing potential caused by the bioactive glass has possible consequences on mechanical properties and biocompatibility. Copyright © 2018 Elsevier Ltd. All rights reserved.

Temperature excursions at the pulp-dentin junction during the curing of light-activated dental restorations.

PubMed

Jakubinek, Michael B; O'Neill, Catherine; Felix, Chris; Price, Richard B; White, Mary Anne

2008-11-01

Excessive heat produced during the curing of light-activated dental restorations may injure the dental pulp. The maximum temperature excursion at the pulp-dentin junction provides a means to assess the risk of thermal injury. In this investigation we develop and evaluate a model to simulate temperature increases during light-curing of dental restorations and use it to investigate the influence of several factors on the maximum temperature excursion along the pulp-dentin junction. Finite element method modeling, using COMSOL 3.3a, was employed to simulate temperature distributions in a 2D, axisymmetric model tooth. The necessary parameters were determined from a combination of literature reports and our measurements of enthalpy of polymerization, heat capacity, density, thermal conductivity and reflectance for several dental composites. Results of the model were validated using in vitro experiments. Comparisons with in vitro experiments indicate that the model provides a good approximation of the actual temperature increases. The intensity of the curing light, the curing time and the enthalpy of polymerization of the resin composite were the most important factors. The composite is a good insulator and the greatest risk occurs when using the light to cure the thin layer of bonding resin or in deep restorations that do not have a liner to act as a thermal barrier. The results show the importance of considering temperature increases when developing curing protocols. Furthermore, we suggest methods to minimize the temperature increase and hence the risk of thermal injury. The physical properties measured for several commercial composites may be useful in other studies.

Towards an HIV cure: a global scientific strategy.

PubMed

Deeks, Steven G; Autran, Brigitte; Berkhout, Ben; Benkirane, Monsef; Cairns, Scott; Chomont, Nicolas; Chun, Tae-Wook; Churchill, Melissa; Di Mascio, Michele; Katlama, Christine; Lafeuillade, Alain; Landay, Alan; Lederman, Michael; Lewin, Sharon R; Maldarelli, Frank; Margolis, David; Markowitz, Martin; Martinez-Picado, Javier; Mullins, James I; Mellors, John; Moreno, Santiago; O'Doherty, Una; Palmer, Sarah; Penicaud, Marie-Capucine; Peterlin, Matija; Poli, Guido; Routy, Jean-Pierre; Rouzioux, Christine; Silvestri, Guido; Stevenson, Mario; Telenti, Amalio; Van Lint, Carine; Verdin, Eric; Woolfrey, Ann; Zaia, John; Barré-Sinoussi, Françoise

2012-07-20

Given the limitations of antiretroviral therapy and recent advances in our understanding of HIV persistence during effective treatment, there is a growing recognition that a cure for HIV infection is both needed and feasible. The International AIDS Society convened a group of international experts to develop a scientific strategy for research towards an HIV cure. Several priorities for basic, translational and clinical research were identified. This Opinion article summarizes the group's recommended key goals for the international community.

Influence of an oxygen-inhibited layer on enamel bonding of dental adhesive systems: surface free-energy perspectives.

PubMed

Ueta, Hirofumi; Tsujimoto, Akimasa; Barkmeier, Wayne W; Oouchi, Hajime; Sai, Keiichi; Takamizawa, Toshiki; Latta, Mark A; Miyazaki, Masashi

2016-02-01

The influence of an oxygen-inhibited layer (OIL) on the shear bond strength (SBS) to enamel and surface free-energy (SFE) of adhesive systems was investigated. The adhesive systems tested were Scotchbond Multipurpose (SM), Clearfil SE Bond (CS), and Scotchbond Universal (SU). Resin composite was bonded to bovine enamel surfaces to determine the SBS, with and without an OIL, of adhesives. The SFE of cured adhesives with and without an OIL were determined by measuring the contact angles of three test liquids. There were no significant differences in the mean SBS of SM and CS specimens with or without an OIL; however, the mean SBS of SU specimens with an OIL was significantly higher than that of SU specimens without an OIL. For all three systems, the mean total SFE (γS), polarity force (γSp), and hydrogen bonding force (γSh) values of cured adhesives with an OIL were significantly higher than those of cured adhesives without an OIL. The results of this study indicate that the presence of an OIL promotes higher SBS of a single-step self-etch adhesive system, but not of a three-step or a two-step self-etch primer system. The SFE values of cured adhesives with an OIL were significantly higher than those without an OIL. The SFE characteristics of the OIL of adhesives differed depending on the type of adhesive. © 2015 Eur J Oral Sci.

Lower temperature curing thermoset polyimides utilizing a substituted norbornene endcap

NASA Technical Reports Server (NTRS)

Waters, John F.; Sukenik, Chaim N.; Kennedy, Vance O.; Livneh, Mordechai; Youngs, Wiley J.; Sutter, James K.; Meador, Mary A. B.; Burke, Luke A.; Ahn, Myong K.

1992-01-01

Methoxycarbonyl bridgehead substituted nadic diacid monomethyl ester, when used as an endcapping monomer, lowered the cure temperature of thermoset PMR polyimides without seriously affecting other desirable properties, such as glass transition temperature and thermal oxidative stability. The C-13 CP/MAS NMR of model compounds was used to follow the cure of resin systems using both the unmodified nadic endcap and the methoxycarbonyl-substituted endcap. Rheological analysis and differential scanning calorimetry DSC also provided evidence for the lower curing nature of the substituted endcap. Two regioisomers of the bridgehead-substituted endcap were isolated, and their chemical structures were elucidated by X-ray crystallography. The model compound and molecular modeling studies conducted ruled out the possibility of regioisomeric imide formation in the substituted endcaps.

Towards multi-disciplinary HIV cure research: integrating social science with biomedical research

PubMed Central

Grossman, Cynthia I; Ross, Anna Laura; Auerbach, Judith D.; Ananworanich, Jintanat; Dubé, Karine; Tucker, Joseph D.; Noseda, Veronica; Possas, Cristina; Rausch, Dianne

2015-01-01

The quest for a cure for HIV remains a timely and key challenge for the HIV research community. Despite significant scientific advances, current HIV therapy regimens do not completely eliminate the negative impact of HIV on the immune system; and the economic impact of treating all people infected with HIV globally, for the duration of their lifetimes, presents significant challenges. This article discusses, from a multi-disciplinary approach, critical social, behavioral, ethical, and economic issues permeating the HIV cure research agenda. As part of a search for an HIV cure, both the perspective of patients/participants and clinical researchers should be taken into account. In addition, continued efforts should be made to involve and educate the broader community. PMID:26642901

Towards Multidisciplinary HIV-Cure Research: Integrating Social Science with Biomedical Research.

PubMed

Grossman, Cynthia I; Ross, Anna Laura; Auerbach, Judith D; Ananworanich, Jintanat; Dubé, Karine; Tucker, Joseph D; Noseda, Veronica; Possas, Cristina; Rausch, Dianne M

2016-01-01

The quest for a cure for HIV remains a timely and key challenge for the HIV research community. Despite significant scientific advances, current HIV therapy regimens do not completely eliminate the negative impact of HIV on the immune system; and the economic impact of treating all people infected with HIV globally, for the duration of their lifetimes, presents significant challenges. This article discusses, from a multidisciplinary approach, critical social, behavioral, ethical, and economic issues permeating the HIV-cure research agenda. As part of a search for an HIV cure, both the perspective of patients/participants and clinical researchers should be taken into account. In addition, continued efforts should be made to involve and educate the broader community. Published by Elsevier Ltd.

Small Business Innovations (Fiber Optics)

NASA Technical Reports Server (NTRS)

1991-01-01

Foster-Miller, Inc. Waltham, MA developed the In-Situ Fiber Optic Polymer Reaction Monitor which could lead to higher yields and lower costs in complex composite manufacturing. The monitor, developed under a Small Business Innovation Research (SBIR) contract with Langley Research Center, uses an infrared, fiber optic sensor to track the molecular vibrational characteristics of a composite part while it is being cured. It is the first analytical system capable of directly measuring the chemistry of advanced composite materials.

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.

Curing behavior and reaction kinetics of binder resins for 3D-printing investigated by dielectric analysis (DEA)

NASA Astrophysics Data System (ADS)

Möginger, B.; Kehret, L.; Hausnerova, B.; Steinhaus, J.

2016-05-01

3D-Printing is an efficient method in the field of additive manufacturing. In order to optimize the properties of manufactured parts it is essential to adapt the curing behavior of the resin systems with respect to the requirements. Thus, effects of resin composition, e.g. due to different additives such as thickener and curing agents, on the curing behavior have to be known. As the resin transfers from a liquid to a solid glass the time dependent ion viscosity was measured using DEA with flat IDEX sensors. This allows for a sensitive measurement of resin changes as the ion viscosity changes two to four decades. The investigated resin systems are based on the monomers styrene and HEMA. To account for the effects of copolymerization in the calculation of the reaction kinetics it was assumed that the reaction can be considered as a homo-polymerization having a reaction order n≠1. Then the measured ion viscosity curves are fitted with the solution of the reactions kinetics - the time dependent degree of conversion (DC-function) - for times exceeding the initiation phase representing the primary curing. The measured ion viscosity curves can nicely be fitted with the DC-function and the determined fit parameters distinguish distinctly between the investigated resin compositions.

TiO2-Based Photocatalytic Geopolymers for Nitric Oxide Degradation

PubMed Central

Strini, Alberto; Roviello, Giuseppina; Ricciotti, Laura; Ferone, Claudio; Messina, Francesco; Schiavi, Luca; Corsaro, Davide; Cioffi, Raffaele

2016-01-01

This study presents an experimental overview for the development of photocatalytic materials based on geopolymer binders as catalyst support matrices. Particularly, geopolymer matrices obtained from different solid precursors (fly ash and metakaolin), composite systems (siloxane-hybrid, foamed hybrid), and curing temperatures (room temperature and 60 °C) were investigated for the same photocatalyst content (i.e., 3% TiO2 by weight of paste). The geopolymer matrices were previously designed for different applications, ranging from insulating (foam) to structural materials. The photocatalytic activity was evaluated as NO degradation in air, and the results were compared with an ordinary Portland cement reference. The studied matrices demonstrated highly variable photocatalytic performance depending on both matrix constituents and the curing temperature, with promising activity revealed by the geopolymers based on fly ash and metakaolin. Furthermore, microstructural features and titania dispersion in the matrices were assessed by scanning electron microscopy (SEM) and energy dispersive X-ray (EDS) analyses. Particularly, EDS analyses of sample sections indicated segregation effects of titania in the surface layer, with consequent enhancement or depletion of the catalyst concentration in the active sample region, suggesting non-negligible transport phenomena during the curing process. The described results demonstrated that geopolymer binders can be interesting catalyst support matrices for the development of photocatalytic materials and indicated a large potential for the exploitation of their peculiar features. PMID:28773634

Hepatitis C Cure Is Associated with Decreased Healthcare Costs in Cirrhotics in Retrospective Veterans Affairs Cohort.

PubMed

Maier, Marissa M; Zhou, Xiao-Hua; Chapko, Michael; Leipertz, Steven L; Wang, Xuan; Beste, Lauren A

2018-06-01

Approximately 233,898 individuals in the Veterans Affairs healthcare network are hepatitis C virus (HCV)-infected, making the Veterans Affairs the single largest provider of HCV care in the USA. Direct-acting antiviral treatment regimens for HCV offer high cure rates. However, these medications pose an enormous financial burden, and whether HCV cure is associated with decreased healthcare costs is poorly defined. To measure downstream healthcare costs in a national population of HCV-infected patients up to 9 years post-HCV antiviral treatment, to compare downstream healthcare costs between cured and uncured patients, and to assess impact of cirrhosis status on cost differences. This is a retrospective cohort study (2004-2014) of hepatitis C-infected patients who initiated antiviral treatment within the United States Veterans Affairs healthcare system October 2004-September 2013. We measured inpatient, outpatient, and pharmacy costs after HCV treatment. For the entire cohort, cure was associated with mean cumulative cost savings in post-treatment years three-six, but no cost savings by post-treatment year nine. By post-treatment year nine, cure in cirrhosis patients was associated with a mean cumulative cost savings of $9474 (- 32,666 to 51,614) per patient, while cure in non-cirrhotic patients was associated with a mean cumulative cost excess of $2526 (- 12,211 to 7159) per patient. Among patients with cirrhosis at baseline, cure is associated with absolute cost savings up to 9 years post-treatment compared to those without cure. Among patients without cirrhosis, early post-treatment cost savings are counterbalanced by higher costs in later years.

Effect of prior refrigeration on botulinal outgrowth in perishable canned cured meat when temperature abused.

PubMed Central

Tompkin, R B; Christiansen, L N; Shaparis, A B

1978-01-01

Perishable canned cured meat inoculated with Clostridium botulinum spores was placed at 4.4 or 10 degrees C after manufacture. Spore germination occurred at 10 degrees C. The germinated cell count remained stable over a period of 16 to 18 weeks. During that time period the inhibitory system and residual nitrite descreased. These factors combine to make perishable canned cured meats more prone to spoilage and potential hazard if they are temperature abused after a period of refrigerated storage. PMID:350155

An in vitro evaluation of diametral tensile strength and flexural strength of nanocomposite vs hybrid and minifill composites cured with different light sources (QTH vs LED).

PubMed

Garapati, Surendra Nath; Priyadarshini; Raturi, Piyush; Shetty, Dinesh; Srikanth, K Venkata

2013-01-01

Composites always remained the target of discussion due to lot of controversies around it. Mechanical properties are one of them. With the introduction of new technology and emergence of various composites which combine superior strength and polish retention, nanocomposites have led to a new spark in the dentistry. A recent curing unit LED with various curing modes claims to produce higher degree of conversion. The aim of this study was to evaluate the diametral tensile strength and flexural strength of nanocomposite, hybrid and minifill composites cured with different light sources (QTH vs LED). Seventy-two samples were prepared using different specially fabricated teflon molds, 24 samples of each composite were prepared for the diametral tensile strength (ADA specification no. 27) and the flexural strength (ISO 4049) of the 12 samples, six were cured with LED (Soft Start curing profile) and other six with QTH curing light and tested on a universal testing machine. The nanocomposite had highest diametral tensile strength and flexural strength which were equivalent to the hybrid composite and superior than the minifill composite. With the combination of superior esthetics and other optimized physical properties, this novel nanocomposite system would be useful for all posterior and anterior applications.

An infiltration/cure model for manufacture of fabric composites by the resin infusion process

NASA Technical Reports Server (NTRS)

Weideman, Mark H.; Loos, Alfred C.; Dexter, H. Benson; Hasko, Gregory H.

1992-01-01

A 1-D infiltration/cure model was developed to simulate fabrication of advanced textile composites by the resin film infusion process. The simulation model relates the applied temperature and pressure processing cycles, along with the experimentally measured compaction and permeability characteristics of the fabric preforms, to the temperature distribution, the resin degree of cure and viscosity, and the infiltration flow front position as a function of time. The model also predicts the final panel thickness, fiber volume fraction, and resin mass for full saturation as a function of compaction pressure. Composite panels were fabricated using the RTM (Resin Transfer Molding) film infusion technique from knitted, knitted/stitched, and 2-D woven carbon preforms and Hercules 3501-6 resin. Fabric composites were fabricated at different compaction pressures and temperature cycles to determine the effects of the processing on the properties. The composites were C-scanned and micrographed to determine the quality of each panel. Advanced cure cycles, developed from the RTM simulation model, were used to reduce the total cure cycle times by a factor of 3 and the total infiltration times by a factor of 2.

Integrating authentic scientific research in a conservation course–based undergraduate research experience

USGS Publications Warehouse

Sorensen, Amanda E.; Corral, Lucia; Dauer, Jenny M.; Fontaine, Joseph J.

2018-01-01

Course-based undergraduate research experiences (CUREs) have been developed to overcome barriers including students in research. However, there are few examples of CUREs that take place in a conservation and natural resource context with students engaging in field research. Here, we highlight the development of a conservation-focused CURE integrated to a research program, research benefits, student self-assessment of learning, and perception of the CURE. With the additional data, researchers were able to refine species distribution models and facilitate management decisions. Most students reported gains in their scientific skills, felt they had engaged in meaningful, real-world research. In student reflections on how this experience helped clarify their professional intentions, many reported being more likely to enroll in graduate programs and seek employment related to science. Also interesting was all students reported being more likely to talk with friends, family, or the public about wildlife conservation issues after participating, indicating that courses like this can have effects beyond the classroom, empowering students to be advocates and translators of science. Field-based, conservation-focused CUREs can create meaningful conservation and natural resource experiences with authentic scientific teaching practices.

Development of orthotropic birefringent materials for photoelastic stress analysis

NASA Technical Reports Server (NTRS)

Daniel, I. M.; Niiro, T.; Koller, G. M.

1981-01-01

Materials were selected and fabrication procedures developed for orthotropic birefringent materials. An epoxy resin (Maraset 658/558 system) was selected as the matrix material. Fibers obtained from style 3733 glass cloth and type 1062 glass roving were used as reinforcement. Two different fabrication procedures were used. In the first one, layers of unidirectional fibers removed from the glass cloth were stacked, impregnated with resin, bagged and cured in the autoclave at an elevated temperature. In the second procedure, the glass roving was drywound over metal frames, impregnated with resin and cured at room temperature under pressure and vacuum in an autoclave. Unidirectional, angle-ply and quasi-isotropic laminates of two thicknesses and with embedded flaws were fabricated. The matrix and the unidirectional glass/epoxy material were fully characterized. The density, fiber volume ratio, mechanical, and optical properties were determined. The fiber volume ratio was over 0.50. Birefringent properties were in good agreement with predictions based on a stress proportioning concept and also, with one exception, with properties predicted by a finite element analysis.

A review of devices used for photocuring resin-based composites.

PubMed

Small, B W

2001-01-01

Composite resin shrinks up to 5% by volume upon curing. This shrinkage and the associated contraction stress remain the two most significant clinical problems with curing resin composite restorations. Many patients continue to experience sensitivity following placement of direct composites and seating of indirect restorations utilizing resin cements. Unfortunately, some claims made by manufacturers or certain clinicians that promise to alleviate these problems are made from a marketing standpoint, with no refereed literature to support those claims. Even within the literature, contradictory results have been reported, perpetuating the confusion. It is of utmost importance that all practicing dentists be aware of the various types of curing systems available and the advantages and disadvantages of each system. It is the opinion of the author that no existing system will alleviate every problem. Until new composite systems are perfected, such as the cyclopolymerizable resins and expanding polymers, we will continue to have shrinkage and stress. Be aware of false claims, read and interpret the literature, and, most importantly, do what is best for your patients.

Acrylic injectable and self-curing formulations for the local release of bisphosphonates in bone tissue.

PubMed

Rodríguez-Lorenzo, L M; Fernández, M; Parra, J; Vázquez, B; López-Bravo, A; Román, J San

2007-11-01

Two bisphosphonates (BPs), namely 1-hydroxy-2-[4-aminophenyl]ethane-1,1-diphosphonic acid (APBP) and 1-hydroxy-2-[3-indolyl]ethane-1,1-diphosphonic acid (IBP), have been synthesized and incorporated to acrylic injectable and self-curing formulations. Alendronic acid monosodium trihydrated salt (ALN) containing cement was formulated as control. These systems have potential applications in low density hard tissues affected by ailments characterized by a high osteoclastic resorption, i.e. osteoporosis and osteolysis. Values of curing parameters of APBP and IBP were acceptable to obtain pastes with enough fluency to be injected through a biopsy needle into the bone cavity. Working times ranged between 8 and 15 min and maximum temperature was around 50 degrees C. Cured systems stored for a month in synthetic body fluid had compressive strengths between 90 and 96 MPa and modulus between 1.2 and 1.3 GPa, which suggest mechanical stabilization after setting and in the short time. BPs were released in PBS at an initial rate depending on the corresponding chemical structure in the order ALN > APBP > IBP to give final concentrations in PBS of 2.21, 0.44, and 0.19 mol/mL for ALN, APBP, and IBP, respectively. Cytotoxicities of bisphosphonates were evaluated, IC(50) values being in the order APBP > ALN > IBP. Absence of cytotoxicity coming from leachables of the cured systems was observed in all cases independently of the BP. An improved cell growth and proliferation for the systems loaded with APBP and IBP compared with that loaded with ALN was observed, as assessed by measuring cell adhesion and proliferation, and total DNA content.

A combinaison of UV curing technology with ATL process

NASA Astrophysics Data System (ADS)

Balbzioui, I.; Hasiaoui, B.; Barbier, G.; L'hostis, G.; Laurent, F.; Ibrahim, A.; Durand, B.

2017-10-01

In order to reduce the time and the cost of manufacturing composite, UV curing technology combined with automated tape placement process (ATL) based on reverse approach by working with a fixed head was studied in this article. First, a brief description of the developed head placement is presented. Mechanical properties are then evaluated by varying process parameters, including compaction force and tape placement speed. Finally, a parametric study is carried out to identify suitable materials and process parameters to manufacture a photo composite material with high mechanical performances. The obtained results show that UV curing is a very good alternative for thermal polymerization because of its fast cure speed due to less dependency on temperature.

Thermochemical tests on resins: Char resistance of selected phenolic cured epoxides

NASA Technical Reports Server (NTRS)

Keck, F. L.

1982-01-01

Curing epoxy resins with novalac phenolic resins is a feasible approach for increasing intact char of the resin system. Char yields above 40% at 700 C were achieved with epoxy novalac (DEN 438)/novalac phenolic (BRWE 5833) resin systems with or without catalyst such as ethyl tri-phenyl phosphonium iodide. These char yields are comparable to commercially used epoxy resin systems like MY-720/DDS/BF3. Stable prepregs are easily made from a solvent solution of the epoxy/phenolic system and this provides a feasible process for fabrication of same into commercial laminates.

Towards an HIV cure: a global scientific strategy

PubMed Central

2013-01-01

Given the limitations of antiretroviral therapy and recent advances in our understanding of HIV persistence during effective treatment, there is a growing recognition that a cure for HIV infection is both needed and feasible. The International AIDS Society convened a group of international experts to develop a scientific strategy for research towards an HIV cure. Several priorities for basic, translational and clinical research were identified. This Opinion article summarizes the group’s recommended key goals for the international community. PMID:22814509

Modeling the filament winding process

NASA Technical Reports Server (NTRS)

Calius, E. P.; Springer, G. S.

1985-01-01

A model is presented which can be used to determine the appropriate values of the process variables for filament winding a cylinder. The model provides the cylinder temperature, viscosity, degree of cure, fiber position and fiber tension as functions of position and time during the filament winding and subsequent cure, and the residual stresses and strains within the cylinder during and after the cure. A computer code was developed to obtain quantitative results. Sample results are given which illustrate the information that can be generated with this code.

Treatment of East Coast fever: a comparison of parvaquone and buparvaquone.

PubMed

Muraguri, G R; Kiara, H K; McHardy, N

1999-11-01

Two trials were conducted to compare the efficacy of parvaquone and buparvaquone for the treatment of naturally acquired East Coast fever (ECF, Theileria parva infection) which, if untreated, is almost invariably fatal in European breeds of cattle. In the first trial 28 naive cattle were exposed in a paddock infested with ticks carrying a virulent form of the disease. Twelve were treated with each drug when they developed clinical ECF. All 24 cattle were cured. In the second study, 100 cases of ECF occurring naturally on farms in Kenya were treated, 50 with each drug. Parvaquone cured 44 (88%) buparvaquone cured 45 (90%). Intercurrent infections, predominantly anaplasmosis and bacterial pneumonia or scour, were treated specifically. It is concluded that parvaquone and buparvaquone are similarly effective in curing ECF and cure rates are maximised by accurate diagnosis and prompt treatment of both ECF and intercurrent infections.

Mathematical and Numerical Analysis of Model Equations on Interactions of the HIV/AIDS Virus and the Immune System

NASA Astrophysics Data System (ADS)

Parumasur, N.; Willie, R.

2008-09-01

We consider a simple HIV/AIDs finite dimensional mathematical model on interactions of the blood cells, the HIV/AIDs virus and the immune system for consistence of the equations to the real biomedical situation that they model. A better understanding to a cure solution to the illness modeled by the finite dimensional equations is given. This is accomplished through rigorous mathematical analysis and is reinforced by numerical analysis of models developed for real life cases.

Rheological characterization of addition polyimide matrix resins and prepregs

NASA Technical Reports Server (NTRS)

Maximovich, M. G.; Galeos, R. M.

1984-01-01

Although graphite-reinforced polyimide matrix composites offer outstanding specific strength and stiffness, together with high thermal oxidative stability, processing problems connected with their rheological behavior remain to be addressed. The present rheological studies on neat polyimide resin systems encountered outgassing during cure. A staging technique has been developed which can successfully handle polyimide samples, and novel methods were applied to generate rheological curves for graphite-reinforced prepregs. The commercial graphite/polyimide systems studied were PRM 15, LARC 160, and V378A.

Liquid crystal materials and tunable devices for optical communications

NASA Astrophysics Data System (ADS)

Du, Fang

In this dissertation, liquid crystal materials and devices are investigated in meeting the challenges for photonics and communications applications. The first part deals with polymer-stabilized liquid crystal (PSLC) materials and devices. Three polymer-stabilized liquid crystal systems are developed for optical communications. The second part reports the experimental investigation of a novel liquid-crystal-infiltrated photonic crystal fiber (PCF) and explores its applications in fiber-optic communications. The curing temperature is found to have significant effects on the PSLC performance. The electro-optic properties of nematic polymer network liquid crystal (PNLC) at different curing temperatures are investigated experimentally. At high curing temperature, a high contrast, low drive voltage, and small hysteresis PNLC is obtained as a result of the formed large LC microdomains. With the help of curing temperature effect, it is able to develop PNLC based optical devices with highly desirable performances for optical communications. Such high performance is generally considered difficult to realize for a PNLC. In fact, the poor performance of PNLC, especially at long wavelengths, has hindered it from practical applications for optical communications for a long time. Therefore, the optimal curing temperature effect discovered in this thesis would enable PSLCs for practical industrial applications. Further more, high birefringence LCs play an important role for near infrared photonic devices. The isothiocyanato tolane liquid crystals exhibit a high birefringence and low viscosity. The high birefringence LC dramatically improves the PSLC contrast ratio while keeping a low drive voltage and fast response time. A free-space optical device by PNLC is experimentally demonstrated and its properties characterized. Most LC devices are polarization sensitive. To overcome this drawback, we have investigated the polymer-stabilized cholesteric LC (PSCLC). Combining the curing temperature effect and high birefringence LC, a polarization independent fiber-optical device is realized with over 30 dB attenuation, ˜12 V rms drive voltage and 11/28 milliseconds (rise/decay) response times. A polymer-stabilized twisted nematic LC (PS TNLC) is also proposed as a variable optical attenuator for optical communications. By using the polarization control system, the device is polarization independent. The polymer network in a PS TNLC not only results in a fast response time (0.9/9 milliseconds for rise/decay respectively), but also removes the backflow effect of TNLC which occurs in the high voltage regime. Another major achievement in this thesis is the first demonstration of an electrically tunable LC-infiltrated photonic crystal fiber (PCF). Two different LC PCF configurations are studied. For the first time, electrically tunable LC PCFs are demonstrated experimentally. The guiding mechanism and polarization properties are studied. Preliminary experimental results are also given for the thermo-optical properties of a LC filled air-core PCF. In conclusion, this dissertation has solved important issues related to PSLC and enables its applications as VOAs and light shutters in optical communications. Through experimental investigations of the LC filled PCFs, a new possibility of developing tunable micro-sized fiber devices is opened for optical communications as well.

Advanced manufacturing development of a composite empennage component for L-1011 aircraft

NASA Technical Reports Server (NTRS)

1978-01-01

Work continued toward the development of tooling and processing concepts required for a cocured hat/skin cover assembly. A plan was developed and implemented to develop the process for using preimpregnated T300/5208 with a resin content of 34 + or - 2 percent by weight. Use of this material results in a simplified laminating process because removal by bleeding or prebleeding is no longer required. The approach to this task basically consists of fabricating and testing flat laminated panels and simulated structural panels to verify known processing techniques relative to end-laminate quality. The flat panels were used to determine air bleeding arrangement and required cure cycle. Single and multihat-stiffened panels were fabricated using the established air bleeding arrangement and cure cycle with the resulting cured parts yielding excellent correlation of ply thickness with all surfaces clear of porosity and voids.

Efficacy of intralesional injection of mumps-measles-rubella vaccine in patients with wart.

PubMed

Zamanian, Abbas; Mobasher, Pezhman; Jazi, Ghazaleh Ahmadi

2014-01-01

In the previous studies, it has been shown that mumps-measles-rubella (MMR) vaccine resulted in regression of warts via immunomodulatory effect and induction of immune system. Due to the high prevalence of warts in various populations, we evaluated the efficacy of MMR vaccine injection in the treatment of cutaneous warts. This double-blind randomized controlled clinical trial was conducted in Hazrat-e-Rasoul Hospital in Tehran in 2011-2012 on 24 patients with warts who were allocated to two groups including MMR group and normal saline group. MMR vaccine was injected intralesionally in the MMR group, whereas normal saline was injected into the lesions in the second group. These injections were repeated every 2 weeks intervals for maximum 3 injections. All patients were followed up every 15-day interval up to 45 days and then up to 6 months regarding relapses and finally, side effects, probable relapse, and therapeutic outcomes were evaluated and compared. At the end of follow-up period, therapeutic outcomes in the MMR group included no cure in 2 cases, relative cure in 4 cases, and complete cure in 18 cases. In normal saline group, these rates included no cure in seven cases, relative cure in nine cases, and complete cure in six cases (P < 0.001). No significant complication occurred in the two groups. MMR vaccine may result in desirable therapeutic response. The hypothesis that is considered here is that MMR vaccine, via induction of cellular and humoral immune system, accelerates the destruction of virus and infected host cells.

Bio-based Polymer Foam from Soyoil

NASA Astrophysics Data System (ADS)

Bonnaillie, Laetitia M.; Wool, Richard P.

2006-03-01

The growing bio-based polymeric foam industry is presently lead by plant oil-based polyols for polyurethanes and starch foams. We developed a new resilient, thermosetting foam system with a bio-based content higher than 80%. The acrylated epoxidized soybean oil and its fatty acid monomers is foamed with pressurized carbon dioxide and cured with free-radical initiators. The foam structure and pore dynamics are highly dependent on the temperature, viscosity and extent of reaction. Low-temperature cure hinds the destructive pore coalescence and the application of a controlled vacuum results in foams with lower densities ˜ 0.1 g/cc, but larger cells. We analyze the physics of foam formation and stability, as well as the structure and mechanical properties of the cured foam using rigidity percolation theory. The parameters studied include temperature, vacuum applied, and cross-link density. Additives bring additional improvements: nucleating agents and surfactants help produce foams with a high concentration of small cells and low bulk density. Hard and soft thermosetting foams with a bio content superior to 80% are successfully produced and tested. Potential applications include foam-core composites for hurricane-resistant housing, structural reinforcement for windmill blades, and tissue scaffolds.

Miniature probe for the delivery and monitoring of a photopolymerizable material

NASA Astrophysics Data System (ADS)

Schmocker, Andreas; Khoushabi, Azadeh; Schizas, Constantin; Bourban, Pierre-Etienne; Pioletti, Dominique P.; Moser, Christophe

2015-12-01

Photopolymerization is a common method to cure materials initially in a liquid state, such as dental implants or bone or tissue fillers. Recent advances in the development of biocompatible gel- and cement-systems open up an avenue for in situ photopolymerization. For minimally invasive surgery, such procedures require miniaturized surgical endoscopic probes to activate and control photopolymerization in situ. We present a miniaturized light probe in which a photoactive material can be (1) mixed, pressurized, and injected, (2) photopolymerized/photoactivated, and (3) monitored during the chemical reaction. The device is used to implant and cure poly(ethylene glycol) dimethacrylate-hydrogel-precursor in situ with ultraviolet A (UVA) light (365 nm) while the polymerization reaction is monitored in real time by collecting the fluorescence and Raman signals generated by the 532-nm excitation light source. Hydrogels could be delivered, photopolymerized, and monitored by the probe up to a curing depth of 4 cm. The size of the photopolymerized samples could be correlated to the fluorescent signal collected by the probe, and the reproducibility of the procedure could be demonstrated. The position of the probe tip inside a bovine caudal intervertebral disc could be estimated in vitro based on the collected fluorescence and Raman signal.

Nano-chemo-mechanical signature of conventional oil-well cement systems: Effects of elevated temperature and curing time

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

Krakowiak, Konrad J., E-mail: kjkrak@mit.edu; Thomas, Jeffrey J., E-mail: JThomas39@slb.com; Musso, Simone, E-mail: SMusso@slb.com

2015-01-15

With ever more challenging (T,p) environments for cementing applications in oil and gas wells, there is a need to identify the fundamental mechanisms of fracture resistant oil well cements. We report results from a multi-technique investigation of behavior and properties of API class G cement and silica-enriched cement systems subjected to hydrothermal curing from 30 °C to 200 °C; including electron probe microanalysis, X-ray diffraction, thermogravimetry analysis, electron microscopy, neutron scattering (SANS), and fracture scratch testing. The results provide a new insight into the link between system chemistry, micro-texture and micro-fracture toughness. We suggest that the strong correlation found betweenmore » chemically modulated specific surface and fracture resistance can explain the drop in fracture properties of neat oil-well cements at elevated temperatures; the fracture property enhancement in silica-rich cement systems, between 110° and 175 °C; and the drop in fracture properties of such systems through prolonged curing over 1 year at 200 °C.« less

Bond Potential of Lithium Disilicate to Heat-Cured Polymethylmethacrylate (PMMA)

DTIC Science & Technology

2015-06-01

system eliminates the need for flasking, boil-out, and long processing times. Instead, the base is light-cured while the teeth are placed with a VLC set...component of previous studies causing failure can be challenged . The stronger ceramic may be durable enough to more accurately measure the bond strength

The microbiome and HIV persistence: implications for viral remission and cure.

PubMed

Koay, Wei Li A; Siems, Lilly V; Persaud, Deborah

2018-01-01

This article discusses the interaction between HIV infection, the gut microbiome, inflammation and immune activation, and HIV reservoirs, along with interventions to target the microbiome and their implications for HIV remission and cure. Most studies show that HIV-infected adults have a gut microbiome associated with decreased bacterial richness and diversity, and associated systemic inflammation and immune activation. A unique set of individuals, elite controllers, who spontaneously control HIV replication, have a similar microbiome to HIV-uninfected individuals. Conversely, exposure to maternal HIV in infants was shown to alter the gut microbiome, even in infants who escaped perinatal infection. Emerging research highlights the importance of the metabolomics and metaproteomics of the gut microbiome, which may have relevance for HIV remission and cure. Together, these studies illustrate the complexity of the relationship between HIV infection, the gut microbiome, and its systemic effects. Understanding the association of HIV with the microbiome, metabolome, and metaproteome may lead to novel therapies to decrease inflammation and immune activation, and impact HIV reservoir size and vaccine responses. Further research in this area is important to inform HIV remission and cure treatments.

Study on Synthesis of Thoreau-modified 3, 5-Dimethyl-Thioltoluenediamine Used as Epoxy Resin Curing Agent and Its Performance

NASA Astrophysics Data System (ADS)

Peng, Yongli; Xiao, Wenzheng

2017-06-01

A novel curing agent Thoreau modified 3, 5-Dimethyl-thioltoluenediamine was synthesized and its molecular structure was characterized by FTIR and DSC. The curing kinetics of a high toughness and low volume shrinkage ratio epoxy system (modified DMTDA/DGEBA) was studied by differential scanning calorimetry (DSC) under noni so thermal conditions. The data were fitted to an order model and autocatalytic model respectively. The results indicate that in order model deviates significantly from experimental data. Malik’s method was used to prove that the curing kinetics of the system concerned follow single-step autocatalytic model, and a “single-point model-free” approach was employed to calculate meaningful kinetic parameters. The DSC curves derived from autocatalytic model gave satisfactory agreement with that of experiment in the range 5K/min∼25K/min. As the heating rate increased, the predicted DSC curves deviated from experimental curves, and the total exothermic enthalpy declined owing to the transition of competition relationship between kinetics control and diffusion control.

A clinical trial of Empress II porcelain inlays luted to vital teeth with a dual-curing adhesive system and a self-curing resin cement.

PubMed

Fabianelli, Andrea; Goracci, Cecilia; Bertelli, Egidio; Davidson, Carel L; Ferrari, Marco

2006-12-01

The aim of the study was to clinically evaluate Empress II inlays cemented with a dual-curing bonding agent and a self-curing luting system. Forty patients were selected to receive one Empress II inlay. Empress II is a heat-pressed glass ceramic containing lithium disilicate and lithium orthophosphate crystals, purported to provide higher stress resistance and improved strength. The restorations were placed between March and May 2000. Recalls were performed after 6, 12, 24, and 36 months. At the 3-year recall, 7 patients were lost to follow-up. Inlays were evaluated for postoperative sensitivity, marginal integrity, marginal leakage, color stability, surface staining, retention, and surface crazing (microcracks). At the 3-year recall, all the restorations were in place and only one showed postoperative sensitivity (at the first recall, 1 week after placement). Only 3 inlays showed slight marginal staining, and 4 inlays showed gaps, with little surface staining or microcracks. No inlay debonded or fractured during theobservation period. All the evaluated inlays were in place and acceptable.

The management of systemic lupus erythematosus: Facts and controversies.

PubMed

Elbirt, Daniel; Sthoeger, Dalia; Asher, Ilan; Sthoeger, Zev Moshe

2010-01-01

Systemic lupus erythematosus is a multisystem disease of unknown etiology in which dysregulation of the innate and adaptive immune systems has a major effect in the pathogenesis of the disease. The treatment should be tailored for each patient according to how the disease manifests itself. Although there is no cure for systemic lupus erythematosus, the current treatment, using anti-inflammatory, antimalarial, and immunosuppressive agents, is fairly effective, but serious adverse events are possible. New biologic agents that target various components of the immune system recently have been developed for the treatment of patients with systemic lupus erythematosus. Copyright 2010 Elsevier Inc. All rights reserved.

Advanced development of non-discoloring EVA-based PV encapsulants

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

Holley, W.H.; Galica, J.P.; Argo, S.C.

1996-01-01

The purpose of this investigation was to better define the problem of field yellowing of EVA-based PV encapsulant, through laboratory study of probable chemical mechanisms and the development of stabilization strategies for protecting EVA from discoloration. EVA from fielded modules was analyzed for vinyl acetate content, unsaturation, and additive levels. These test results were then compared to results from Xenon Arc Weather-Ometer aged glass/EVA/glass laminates made in the laboratory. Variables evaluated in Weather-Ometer aged laminates included ``standard-cure`` A9918P EVA, ``fast-cure`` 15295P EVA, low iron glass superstrate containing cerium oxide, and systematic elimination or addition of specific additives. Six significant findingsmore » were revealed: 1) Improved ``standard-cure`` and ``fast-cure`` type EVA encapsulants, formulations X9903P and X15303P, respectively, showed little or no yellowing after extended Weather-Ometer exposure; 2) The use of {open_quote}{open_quote}fast-cure{close_quote}{close_quote} EVA reduced discoloration when compared with {open_quote}{open_quote}standard-cure{close_quote}{close_quote} A9918P EVA; 3) Glass superstrate containing cerium oxide resulted in a reduced rate of EVA discoloration; 4) {open_quote}{open_quote}Fast-cure{close_quote}{close_quote} EVA used with glass superstrate containing cerium oxide showed no visible yellowing after 32 weeks in the Weather-Ometer{emdash}a period estimated to be roughly equivalent to 20{endash}30 years of exposure in the Southwest; 5) Severely discolored EVA samples from the field showed no measurable loss of acetate group and little detectable unsaturation; and 6) EVA encapsulant with a Tefzel cover exhibited no yellowing after extended Weather-Ometer exposure. {copyright} {ital 1996 American Institute of Physics.}« less

Investigation of test methods, material properties, and processes for solar cell encapsulants

NASA Technical Reports Server (NTRS)

Willis, P. B.

1982-01-01

Technical investigations concerned the development of advanced cure chemistries for lamination type pottants; the continued evaluation of soil resistant surface treatments, 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. One compound in particular, designated Lupersol - TBEC (Lucidol Division of Pennwalt Corp.) was found to be unusually effective in promoting the rapid cure of both these materials. Formulation of these resins with TBEC resulted in compositions of very high gel content, lower temperatures of activation, and much lower cure times, even in the ethylene/methyl acrylate polymer that is more difficult to cure. It is expected that TBEC modified pottant formulations may permit the lamination/encapsulation step to be operated at lower temperatures, higher speed, higher throughput and a much wider tolerance for intentional or accidental variations in the cure schedule. An experimental program continued to determine the effectiveness of soil resistant coatings.

Compressive strength of marine material mixed concrete

NASA Astrophysics Data System (ADS)

Adnan; Parung, H.; Tjaronge, M. W.; Djamaluddin, R.

2017-11-01

Many cement factories have been incorporated fly ash with clinker cement to produce blended cement. PCC is a type of blended cement incorporated fly ash that produced in Indonesia cement factories. To promote the sustainable development in the remote islands this present paper attempted to study the suitability of sea water, marine sand that available abundantly surround the remote island with Portland Composite Cement (PCC) and crushed river stone to produce concrete. Slump test was conducted to evaluate the workability of fresh concrete and also compressive strength with stress-strain relationship was carried out to evaluate the hardened concrete that cured with two curing condition (e.g. sea water curing, and tap water-wet burlap curing). Test result indicated that fresh concrete had proper workability and all hardened specimens appeared a good compaction result. Compressive strength of specimens cured which sea water was higher than the specimens which cured by tap water-wet burlap where stress-strain behavior of specimens made with sea water, marine sand, and PCC had similar behavior with specimens which made with PCC and tap water.

Expectation maximization-based likelihood inference for flexible cure rate models with Weibull lifetimes.

PubMed

Balakrishnan, Narayanaswamy; Pal, Suvra

2016-08-01

Recently, a flexible cure rate survival model has been developed by assuming the number of competing causes of the event of interest to follow the Conway-Maxwell-Poisson distribution. This model includes some of the well-known cure rate models discussed in the literature as special cases. Data obtained from cancer clinical trials are often right censored and expectation maximization algorithm can be used in this case to efficiently estimate the model parameters based on right censored data. In this paper, we consider the competing cause scenario and assuming the time-to-event to follow the Weibull distribution, we derive the necessary steps of the expectation maximization algorithm for estimating the parameters of different cure rate survival models. The standard errors of the maximum likelihood estimates are obtained by inverting the observed information matrix. The method of inference developed here is examined by means of an extensive Monte Carlo simulation study. Finally, we illustrate the proposed methodology with a real data on cancer recurrence. © The Author(s) 2013.

Graphite filament wound pressure vessels

NASA Technical Reports Server (NTRS)

Feldman, A.; Damico, J. J.

1972-01-01

Filament wound NOL rings, 4-inch and 8-inch diameter closed-end vessels involving three epoxy resin systems and three graphite fibers were tested to develop property data and fabrication technology for filament wound graphite/epoxy pressure vessels. Vessels were subjected to single-cycle burst tests at room temperature. Manufacturing parameters were established for tooling, winding, and curing that resulted in the development of a pressure/vessel performance factor (pressure x volume/weight) or more than 900,000 in. for an oblate spheroid specimen.

Greyscale Photolithography for Multilayer PZT Microelectromechanical Systems (MEMS) Device Applications

DTIC Science & Technology

We present development of a process to perform greyscale photolithography on a 2.55-m thick photoresist in order to transfer tiered and sloped...platinum or iridium oxide (IrO2) electrodes above and below each layer. Process variables including resist rehydration , focus of the exposure, and UV cure...bake temperature were optimized to produce the best greyscale profile through the thickness of the resist.

The Rothermel surface fire spread model and associated developments: A comprehensive explanation

Treesearch

Patricia L. Andrews

2018-01-01

The Rothermel surface fire spread model, with some adjustments by Frank A. Albini in 1976, has been used in fire and fuels management systems since 1972. It is generally used with other models including fireline intensity and flame length. Fuel models are often used to define fuel input parameters. Dynamic fuel models use equations for live fuel curing. Models have...

[Physical and mechanical properties of the thermosetting resin for crown and bridge cured by micro-wave heating].

PubMed

Kaneko, K

1989-09-01

A heating method using micro-waves was utilized to obtain strong thermosetting resin for crown and bridge. The physical and mechanical properties of the thermosetting resin were examined. The resin was cured in a shorter time by the micro-waves heating method than by the conventional heat curing method and the working time was reduced markedly. The base resins of the thermosetting resin for crown and bridge for the micro-waves heating method were 2 PA and diluent 3 G. A compounding volume of 30 wt% for diluent 3 G was considered good the results of compressive strength, bending strength and diametral tensile strength. Grams of 200-230 of the filler compounded to the base resins of 2 PA-3 G system provided optimal compressive strength, bending strength and diametral tensile strength. A filler gram of 230 provided optimal hardness and curing shrinkage rate, the coefficient of thermal expansion became smaller with the increase of the compounding volume of the filler. The trial thermosetting resin for crown and bridge formed by the micro-waves heating method was not inferior to the conventional resin by the heat curing method or the light curing method.

A dynamic Monte Carlo model for predicting radiant exposure distribution in dental composites: model development and verifications

NASA Astrophysics Data System (ADS)

Chen, Yin-Chu; Ferracane, Jack L.; Prahl, Scott A.

2005-03-01

Photo-cured dental composites are widely used in dental practices to restore teeth due to the esthetic appearance of the composites and the ability to cure in situ. However, their complex optical characteristics make it difficult to understand the light transport within the composites and to predict the depth of cure. Our previous work showed that the absorption and scattering coefficients of the composite changed after the composite was cured. The static Monte Carlo simulation showed that the penetration of radiant exposures differed significantly for cured and uncured optical properties. This means that a dynamic model is required for accurate prediction of radiant exposure in the composites. The purpose of this study was to develop and verify a dynamic Monte Carlo (DMC) model simulating light propagation in dental composites that have dynamic optical properties while photons are absorbed. The composite was divided into many small cubes, each of which had its own scattering and absorption coefficients. As light passed through the composite, the light was scattered and absorbed. The amount of light absorbed in each cube was calculated using Beer's Law and was used to determine the next optical properties in that cube. Finally, the predicted total reflectance and transmittance as well as the optical property during curing were verified numerically and experimentally. Our results showed that the model predicted values agreed with the theoretical values within 1% difference. The DMC model results are comparable with experimental results within 5% differences.

Stakeholder Engagement in HIV Cure Research: Lessons Learned from Other HIV Interventions and the Way Forward

PubMed Central

Chu, Carissa; Ananworanich, Jintanat; Excler, Jean-Louis; Tucker, Joseph D.

2015-01-01

Abstract Clinical and basic science advances have raised considerable hope for achieving an HIV cure by accelerating research. This research is dominated primarily by issues about the nature and design of current and future clinical trials. Stakeholder engagement for HIV cure remains in its early stages. Our analysis examines timing and mechanisms of historical stakeholder engagement in other HIV research areas for HIV-uninfected individuals [vaccine development and pre-exposure prophylaxis (PrEP)], and HIV-infected individuals (treatment as prevention, prevention of mother-to-child transmission, and treatment of acute HIV infection) and articulate a plan for HIV cure stakeholder engagement. The experience from HIV vaccine development shows that early engagement of stakeholders helped manage expectations, mitigating the failure of several vaccine trials, while paving the way for subsequent trials. The relatively late engagement of HIV stakeholders in PrEP research may partly explain some of the implementation challenges. The treatment-related stakeholder engagement was strong and community-led from the onset and helped translation from research to implementation. We outline five steps to initiate and sustain stakeholder engagement in HIV cure research and conclude that stakeholder engagement represents a key investment in which stakeholders mutually agree to share knowledge, benefits, and risk of failure. Effective stakeholder engagement prevents misconceptions. As HIV cure research advances from early trials involving subjects with generally favorable prognosis to studies involving greater risk and uncertainty, success may depend on early and deliberate engagement of stakeholders. PMID:26061668

Stakeholder Engagement in HIV Cure Research: Lessons Learned from Other HIV Interventions and the Way Forward.

PubMed

Lo, Ying-Ru; Chu, Carissa; Ananworanich, Jintanat; Excler, Jean-Louis; Tucker, Joseph D

2015-07-01

Clinical and basic science advances have raised considerable hope for achieving an HIV cure by accelerating research. This research is dominated primarily by issues about the nature and design of current and future clinical trials. Stakeholder engagement for HIV cure remains in its early stages. Our analysis examines timing and mechanisms of historical stakeholder engagement in other HIV research areas for HIV-uninfected individuals [vaccine development and pre-exposure prophylaxis (PrEP)], and HIV-infected individuals (treatment as prevention, prevention of mother-to-child transmission, and treatment of acute HIV infection) and articulate a plan for HIV cure stakeholder engagement. The experience from HIV vaccine development shows that early engagement of stakeholders helped manage expectations, mitigating the failure of several vaccine trials, while paving the way for subsequent trials. The relatively late engagement of HIV stakeholders in PrEP research may partly explain some of the implementation challenges. The treatment-related stakeholder engagement was strong and community-led from the onset and helped translation from research to implementation. We outline five steps to initiate and sustain stakeholder engagement in HIV cure research and conclude that stakeholder engagement represents a key investment in which stakeholders mutually agree to share knowledge, benefits, and risk of failure. Effective stakeholder engagement prevents misconceptions. As HIV cure research advances from early trials involving subjects with generally favorable prognosis to studies involving greater risk and uncertainty, success may depend on early and deliberate engagement of stakeholders.

Novel therapeutic approaches for disease-modification of epileptogenesis for curing epilepsy

PubMed Central

Clossen, Bryan L.; Reddy, Doodipala Samba

2017-01-01

This article describes the recent advances in epileptogenesis and novel therapeutic approaches for the prevention of epilepsy, with a special emphasis on the pharmacological basis of disease-modification of epileptogenesis for curing epilepsy. Here we assess animal studies and human clinical trials of epilepsy spanning 1982–2016. Epilepsy arises from a number of neuronal factors that trigger epileptogenesis, which is the process by which a brain shifts from a normal physiologic state to an epileptic condition. The events precipitating these changes can be of diverse origin, including traumatic brain injury, cerebrovascular damage, infections, chemical neurotoxicity, and emergency seizure conditions such as status epilepticus. Expectedly, the molecular and system mechanisms responsible for epileptogenesis are not well defined or understood. To date, there is no approved therapy for the prevention of epilepsy. Epigenetic dysregulation, neuroinflammation, and neurodegeneration appear to trigger epileptogenesis. Targeted drugs are being identified that can truly prevent the development of epilepsy in at-risk people. The promising agents include rapamycin, COX-2 inhibitors, TRK inhibitors, epigenetic modulators, JAK-STAT inhibitors, and neurosteroids. Recent evidence suggests that neurosteroids may play a role in modulating epileptogenesis. A number of promising drugs are under investigation for the prevention or modification of epileptogenesis to halt the development of epilepsy. Some drugs in development appear rational for preventing epilepsy because they target the initial trigger or related signaling pathways as the brain becomes progressively more prone to seizures. Additional research into the target validity and clinical investigation is essential to make new frontiers in curing epilepsy. PMID:28179120

Novel therapeutic approaches for disease-modification of epileptogenesis for curing epilepsy.

PubMed

Clossen, Bryan L; Reddy, Doodipala Samba

2017-06-01

This article describes the recent advances in epileptogenesis and novel therapeutic approaches for the prevention of epilepsy, with a special emphasis on the pharmacological basis of disease-modification of epileptogenesis for curing epilepsy. Here we assess animal studies and human clinical trials of epilepsy spanning 1982-2016. Epilepsy arises from a number of neuronal factors that trigger epileptogenesis, which is the process by which a brain shifts from a normal physiologic state to an epileptic condition. The events precipitating these changes can be of diverse origin, including traumatic brain injury, cerebrovascular damage, infections, chemical neurotoxicity, and emergency seizure conditions such as status epilepticus. Expectedly, the molecular and system mechanisms responsible for epileptogenesis are not well defined or understood. To date, there is no approved therapy for the prevention of epilepsy. Epigenetic dysregulation, neuroinflammation, and neurodegeneration appear to trigger epileptogenesis. Targeted drugs are being identified that can truly prevent the development of epilepsy in at-risk people. The promising agents include rapamycin, COX-2 inhibitors, TRK inhibitors, epigenetic modulators, JAK-STAT inhibitors, and neurosteroids. Recent evidence suggests that neurosteroids may play a role in modulating epileptogenesis. A number of promising drugs are under investigation for the prevention or modification of epileptogenesis to halt the development of epilepsy. Some drugs in development appear rational for preventing epilepsy because they target the initial trigger or related signaling pathways as the brain becomes progressively more prone to seizures. Additional research into the target validity and clinical investigation is essential to make new frontiers in curing epilepsy. Copyright © 2017 Elsevier B.V. All rights reserved.

[MRSA-related empyema as thoracic surgical site infection].

PubMed

Mizutani, Hisao

2009-09-01

The incidence of empyema as a thoracic surgical site infection (SSI) is relating low, but empyema related to MRSA poses an unenviable therapeutic challenge. We review 3 cases of MRSA-related empyema as SSI seem in the last 10 years, and evaluate therapeutic measures. All 3 subjects began being administered vancomycin (VCM) systemically once the diagnosis was established. Subject 1 developed MRSA-related empyema following pulmonary segmentectomy for small-cell lung cancer. The subject was treated following a diagnosis of incisional SSI, with delayed adequate pleural drainage, resulting in treatment difficulties, but was cured without becoming MRSA-negative. Subject 2 developed MRSA-related empyema following pulmonary lobectomy for advanced lung cancer associated with pneumoconiosis. Following bronchoplasty, a chest tube was placed for long-term drainage. The subject did not become MRSA-negative after VCM administration, but became so after linezolid treatment, facilitating a cure. Subject 3, who had secondary pneumothorax, underwent thoracoscopic partial hepatic resection. Intraoperative findings suggested pleural cavity infection, necessitating a prophylactic drain, but MRSA-related pyothorax developed. Fibrinolysis with urokinase effectively cleared up the poor drainage and the subject was cured without becoming MRSA-negative. In conclusion, in controlling MRSA-related empyema as SSI noted that: (1) long-term postperative thoracic drain retention may lead to retrograde infection; (2) surgical procedures reducing the extent of pulmonary resection may effectively prevent pyothorax progression; (3) for poor drainage in advanced pyothorax, fibrinolytic therapy is worth attempting before thoracoscopic surgery; and (4) the timing for discontinuing anti-MRSA drugs should be determined based on the clinical course rather than negative conversion of bacteria.

Alkali-aggregate reactivity of typical siliceious glass and carbonate rocks in alkali-activated fly ash based geopolymers

NASA Astrophysics Data System (ADS)

Lu, Duyou; Liu, Yongdao; Zheng, Yanzeng; Xu, Zhongzi; Shen, Xiaodong

2013-08-01

For exploring the behaviour of alkali-aggregate reactivity (AAR) in alkali-activated geopolymeric materials and assessing the procedures for testing AAR in geopolymers, the expansion behaviour of fly ash based geopolymer mortars with pure silica glass and typical carbonate rocks were studied respectively by curing at various conditions, i.e. 23°C and 38°C with relative humidity over 95%, immersed in 1M NaOH solution at 80°C. Results show that, at various curing conditions, neither harmful ASR nor harmful ACR was observed in geopolymers with the criteria specified for OPC system. However, with the change of curing conditions, the geopolymer binder and reactive aggregates may experience different reaction processes leading to quite different dimensional changes, especially with additional alkalis and elevated temperatures. It suggests that high temperature with additional alkali for accelerating AAR in traditional OPC system may not appropriate for assessing the alkali-aggregate reactivity behaviour in geopolymers designed for normal conditions. On the other hand, it is hopeful to control the dimensional change of geopolymer mortar or concrete by selecting the type of aggregates and the appropriate curing conditions, thus changing the harmful AAR in OPC into beneficial AAR in geopolymers and other alkali-activated cementitious systems.

Nitrate reductase activity of Staphylococcus carnosus affecting the color formation in cured raw ham.

PubMed

Bosse Née Danz, Ramona; Gibis, Monika; Schmidt, Herbert; Weiss, Jochen

2016-07-01

The influence of the nitrate reductase activity of two Staphylococcus carnosus strains used as starter cultures on the formation of nitrate, nitrite and color pigments in cured raw ham was investigated. In this context, microbiological, chemical and multivariate image analyses were carried out on cured raw hams, which were injected with different brines containing either nitrite or nitrate, with or without the S. carnosus starter cultures. During processing and storage, the viable counts of staphylococci remained constant at 6.5logcfu/g in the hams inoculated with starter cultures, while the background microbiota of the hams processed without the starter cultures developed after 14days. Those cured hams inoculated with S. carnosus LTH 7036 (high nitrate reductase activity) showed the highest decrease in nitrate and high nitrite concentrations in the end product, but were still in the range of the legal European level. The hams cured with nitrate and without starter culture or with the other strain, S. carnosus LTH 3838 (low nitrate reductase activity) showed higher residual nitrate levels and a lower nitrite content in the end product. The multivariate image analysis identified spatial and temporal differences in the meat pigment profiles of the differently cured hams. The cured hams inoculated with S. carnosus LTH 3838 showed an uncured core due to a delay in pigment formation. Therefore, the selection of starter cultures based on their nitrate reductase activity is a key point in the formation of curing compounds and color pigments in cured raw ham manufacture. Copyright © 2016 Elsevier Ltd. All rights reserved.

Cure rate model with interval censored data.

PubMed

Kim, Yang-Jin; Jhun, Myoungshic

2008-01-15

In cancer trials, a significant fraction of patients can be cured, that is, the disease is completely eliminated, so that it never recurs. In general, treatments are developed to both increase the patients' chances of being cured and prolong the survival time among non-cured patients. A cure rate model represents a combination of cure fraction and survival model, and can be applied to many clinical studies over several types of cancer. In this article, the cure rate model is considered in the interval censored data composed of two time points, which include the event time of interest. Interval censored data commonly occur in the studies of diseases that often progress without symptoms, requiring clinical evaluation for detection (Encyclopedia of Biostatistics. Wiley: New York, 1998; 2090-2095). In our study, an approximate likelihood approach suggested by Goetghebeur and Ryan (Biometrics 2000; 56:1139-1144) is used to derive the likelihood in interval censored data. In addition, a frailty model is introduced to characterize the association between the cure fraction and survival model. In particular, the positive association between the cure fraction and the survival time is incorporated by imposing a common normal frailty effect. The EM algorithm is used to estimate parameters and a multiple imputation based on the profile likelihood is adopted for variance estimation. The approach is applied to the smoking cessation study in which the event of interest is a smoking relapse and several covariates including an intensive care treatment are evaluated to be effective for both the occurrence of relapse and the non-smoking duration. Copyright (c) 2007 John Wiley & Sons, Ltd.

Estimation of the cure rate in Iranian breast cancer patients.

PubMed

Rahimzadeh, Mitra; Baghestani, Ahmad Reza; Gohari, Mahmood Reza; Pourhoseingholi, Mohamad Amin

2014-01-01

Although the Cox's proportional hazard model is the popular approach for survival analysis to investigate significant risk factors of cancer patient survival, it is not appropriate in the case of log-term disease free survival. Recently, cure rate models have been introduced to distinguish between clinical determinants of cure and variables associated with the time to event of interest. The aim of this study was to use a cure rate model to determine the clinical associated factors for cure rates of patients with breast cancer (BC). This prospective cohort study covered 305 patients with BC, admitted at Shahid Faiazbakhsh Hospital, Tehran, during 2006 to 2008 and followed until April 2012. Cases of patient death were confirmed by telephone contact. For data analysis, a non-mixed cure rate model with Poisson distribution and negative binomial distribution were employed. All analyses were carried out using a developed Macro in WinBugs. Deviance information criteria (DIC) were employed to find the best model. The overall 1-year, 3-year and 5-year relative survival rates were 97%, 89% and 74%. Metastasis and stage of BC were the significant factors, but age was significant only in negative binomial model. The DIC also showed that the negative binomial model had a better fit. This study indicated that, metastasis and stage of BC were identified as the clinical criteria for cure rates. There are limited studies on BC survival which employed these cure rate models to identify the clinical factors associated with cure. These models are better than Cox, in the case of long-term survival.

EVALUATION OF BARRIERS TO THE USE OF RADIATION-CURED COATINGS IN SCREEN PRINTING

EPA Science Inventory

The report gives results of an evaluation of barriers to the use of radiation-cured coatings in screen printing. In support of the Source Reduction Review Project (SRRP), maximum achievable control technology (MACT) standards development, and the Pollution Prevention Act, EPA is ...

Advances in light-curing units: four generations of LED lights and clinical implications for optimizing their use: Part 2. From present to future.

PubMed

Shortall, Adrian C; Palin, Will M; Jacquot, Bruno; Pelissier, Bruno

2012-01-01

The first part of this series of two described the history of light curing in dentistry and developments in LED lights since their introduction over 20 years ago. Current second- and third-generation LED light units have progressively replaced their halogen lamp predecessors because of their inherent advantages. The background to this, together with the clinical issues relating to light curing and the possible solutions, are outlined in the second part of this article. Finally, the innovative features of what may be seen as the first of a new fourth-generation of LED lights are described and guidance is given for the practitioner on what factors to consider when seeking to purchase a new LED light activation unit. Adequate curing in depth is fundamental to clinical success with any light-activated restoration. To achieve this goal predictably, an appropriate light source needs to be combined with materials knowledge, requisite clinical skills and attention to detail throughout the entire restoration process. As dentists increasingly use light-cured direct composites to restore large posterior restorations they need to appreciate the issues central to effective and efficient light curing and to know what to look for when seeking to purchase a new light-curing unit.

A sup-score test for the cure fraction in mixture models for long-term survivors.

PubMed

Hsu, Wei-Wen; Todem, David; Kim, KyungMann

2016-12-01

The evaluation of cure fractions in oncology research under the well known cure rate model has attracted considerable attention in the literature, but most of the existing testing procedures have relied on restrictive assumptions. A common assumption has been to restrict the cure fraction to a constant under alternatives to homogeneity, thereby neglecting any information from covariates. This article extends the literature by developing a score-based statistic that incorporates covariate information to detect cure fractions, with the existing testing procedure serving as a special case. A complication of this extension, however, is that the implied hypotheses are not typical and standard regularity conditions to conduct the test may not even hold. Using empirical processes arguments, we construct a sup-score test statistic for cure fractions and establish its limiting null distribution as a functional of mixtures of chi-square processes. In practice, we suggest a simple resampling procedure to approximate this limiting distribution. Our simulation results show that the proposed test can greatly improve efficiency over tests that neglect the heterogeneity of the cure fraction under the alternative. The practical utility of the methodology is illustrated using ovarian cancer survival data with long-term follow-up from the surveillance, epidemiology, and end results registry. © 2016, The International Biometric Society.

The 21st Century Cures Act Implications for the Reduction of Racial Health Disparities in the US Criminal Justice System: a Public Health Approach.

PubMed

Cole, Donna M; Thomas, Dawna Marie; Field, Kelsi; Wool, Amelia; Lipiner, Taryn; Massenberg, Natalie; Guthrie, Barbara J

2017-11-09

Past drug epidemics have disproportionately criminalized drug addiction among African Americans, leading to disparate health outcomes, increased rates of HIV/AIDS, and mass incarceration. Conversely, the current opioid addiction crisis in the USA focuses primarily on white communities and is being addressed as a public health problem. The 21st Century Cures Act has the potential to reduce racial health disparities in the criminal justice system through the Act's public health approach to addiction and mental health issues. The 21st Century Cures Act is a progressive step in the right direction; however, given the historical context of segregation and the criminalization of drug addiction among African Americans, the goals of health equity are at risk of being compromised. This paper discusses the implications of this landmark legislation and its potential to decrease racial health disparities, highlighting the importance of ensuring that access to treatment and alternatives to incarceration must include communities of color. In this paper, the authors explain the key components of the 21st Century Cures Act that are specific to criminal justice reform, including a key objective, which is treatment over incarceration. We suggest that without proper attention to how, and where, funding mechanisms are distributed, the 21st Century Cures Act has the potential to increase racial health disparities rather than alleviate them.

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.

The hepatitis C genotype 1 paradox: cost per treatment is increasing, but cost per cure is decreasing.

PubMed

Shafran, Stephen D

2015-01-01

Significant attention has been focused on the perceived increase in the cost of antiviral treatment for hepatitis C genotype 1 infection since the approval of the first direct-acting antiviral agents in 2011. Using Canadian list prices, the present analysis points out a paradox: while the cost per antiviral regimen is increasing, the cost per cure is decreasing, especially with interferon-free therapy. In a publicly funded health care system, the lowest cost per cure is a more valuable measure of value for public money than the cost per regimen.

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

Not Available

The Phase I program and the design plan for the Phase II Experiment Integration wherein the AAI Corporation's 24/1 concentrating collector is used to produce hot water to cure concrete blocks is described. This concept has a tremendous potential since each block requires about 1500 Btu for curing at a temperature of 140/sup 0/F to 180/sup 0/F. To demonstrate this process, the solar hot water system will be installed at the new block fabricating plant being built by the York Building Products Co., Inc. at Harrisburg, Pa. A circular underground curing tank will be the storage tank for the solarmore » system. Since the plane is new, no retrofitting is required. The collectors will be mounted on the roof of the new block producing facility. A full-scale 256 ft/sup 2/ module of the 24/1 collector has been built and tested by AAI Corporation. A 9216 ft/sup 2/ array of collectors is required for this experiment. AAI Corporation is pursuing a development program planned to culminate in the marketing of the 24/1 collector at a selling price of $7 to $10 per square foot. The collector is built in 9 ft by 34 ft modules and is self-supporting with pads located at the four corners. It can be inclined at the most favorable angle for solar performance, and can be located on a roof, or as a separate unit on the ground. A final design and performance analysis and an economic analysis are presented. (WHK)« less

Clinical Applications of Genome Editing to HIV Cure.

PubMed

Wang, Cathy X; Cannon, Paula M

2016-12-01

Despite significant advances in HIV drug treatment regimens, which grant near-normal life expectancies to infected individuals who have good virological control, HIV infection itself remains incurable. In recent years, novel gene- and cell-based therapies have gained increasing attention due to their potential to provide a functional or even sterilizing cure for HIV infection with a one-shot treatment. A functional cure would keep the infection in check and prevent progression to AIDS, while a sterilizing cure would eradicate all HIV viruses from the patient. Genome editing is the most precise form of gene therapy, able to achieve permanent genetic disruption, modification, or insertion at a predesignated genetic locus. The most well-studied candidate for anti-HIV genome editing is CCR5, an essential coreceptor for the majority of HIV strains, and the lack of which confers HIV resistance in naturally occurring homozygous individuals. Genetic disruption of CCR5 to treat HIV has undergone clinical testing, with seven completed or ongoing trials in T cells and hematopoietic stem and progenitor cells, and has shown promising safety and potential efficacy profiles. Here we summarize clinical findings of CCR5 editing for HIV therapy, as well as other genome editing-based approaches under pre-clinical development. The anticipated development of more sophisticated genome editing technologies should continue to benefit HIV cure efforts.

In-situ measurement of processing properties during fabrication in a production tool

NASA Technical Reports Server (NTRS)

Kranbuehl, D. E.; Haverty, P.; Hoff, M.; Loos, A. C.

1988-01-01

Progress is reported on the use of frequency-dependent electromagnetic measurements (FDEMs) as a single, convenient technique for continuous in situ monitoring of polyester cure during fabrication in a laboratory and manufacturing environment. Preliminary FDEM sensor and modeling work using the Loss-Springer model in order to develop an intelligent closed-loop, sensor-controlled cure process is described. FDEMs using impedance bridges in the Hz to MHz region is found to be ideal for automatically monitoring polyester processing properties continuously throughout the cure cycle.

Effect of Dental Chair Light on Enamel Bonding of Orthodontic Brackets Using Light Cure Based Adhesive System: An In-Vitro Study

PubMed Central

Tiwari, Anil; Shyagali, Tarulatha; Kohli, Sarvraj; Joshi, Rishi; Gupta, Abhishek; Tiwari, Rana

2016-01-01

Aim: The aim of this in vitro study was to evaluate the influence of the Dental chair light on the bond strength of light cured composite resin. Materials and Methods: Sixty therapeutically extracted human premolar teeth were randomly allocated to two groups of 30 specimens each. In both groups light cured composite resin (Transbond XT) and MBT premolar metal brackets (3M Unitek) was used to bond brackets. In group I and II light curing was done using Light-emitting diode light curing units without and with the dental chair light respectively. After bonding, all samples were stored in distilled water at room temperature for 24 hours and subsequently tested for shear bond strength and Adhesive Remnant Index (ARI) scores. Data was subjected to Mann Whitney U statistical test. Results: Results indicated that there was significantly higher shear bond strength (7.71 ± 1.90) for the Group II (composite cured with LED and dental chair light) compared with Group I (composite cured with LED LCU only) (5.74 ± 1.13).the obtained difference was statistically significant. There was no statistical significant difference between ARI scores in between the groups. Conclusions: light cure bonding with dental chair light switched on will produce greater bond strength than the conventional bonding. However, the ARI score were similar to both the groups. It is advised that the inexperienced orthodontist should always switch off the dental chair light while bonding for enough working time during the bracket placement. PMID:28077886

Evolution of Immiscibly Blended Functionalized Polymers with Respect to Cure Parameters and Formulation

NASA Astrophysics Data System (ADS)

Heller, Nicholas Walter Medicus

Powder coatings are becoming ubiquitous in the coating marketplace due to the absence of solvents in their formulation, but they have yet to see implementation in low-reflectance outdoor applications. This demand could be met by utilizing polymer blends formulated with low loadings of matting agents and pigments. The goal of this research is a thorough characterization of prototype low-reflectance coatings through several analytical techniques. Prototypical thermoset blends consist of functionalized polyurethanes rendered immiscible by differences in polar and hydrogen bonding characteristics, resulting in a surface roughened by droplet domains. Analysis of both pigmented and control clear films was performed. This research project had three primary aims: (1) determine the composition of the resin components of the polymer blend; (2) to monitor the evolution of domains before and during curing of clear polymer blends; (3) to monitor the evolution of these domains when pigments are added to these blends. The clear films enabled unhindered analysis by Fourier transform infrared (FTIR) and Raman spectroscopy on the binder. However, these domains provided no spectroscopic signatures despite their observation by optical microscopy. This necessitated the development of a new procedure for cross-section preparation that leaves no contamination from polishing media, which enabled Raman mapping of the morphology via an introduced marker peak from styrene monomer. The clears were analyzed as a powder and as films that were quenched at various cure-times using FTIR, Raman, transmission electron microscopy (TEM), and thermomechanical methods to construct a model of coating evolution based on cure parameters and polymer dynamics. Domains were observed in the powder, and underwent varying rates of coarsening as the cure progressed. TEM, scanning electron microscopy and thermomechanical methods were also used on pigmented systems at different states of the cure, including in powder form. TEM analysis additionally revealed the encapsulation of pigment particles by the domains, which helped explain the interaction between phase separation and pigment materials. The knowledge gained from fundamental characterization could be used to enable future generations of durable powder coatings with dead matte finishes.

First Year Course-Based Undergraduate Research Experience (CURE) Using the CRISPR/Cas9 Genome Engineering Technology in Zebrafish †

PubMed Central

Bhatt, Jay M.; Challa, Anil Kumar

2018-01-01

Genetic analysis in model systems can provide a rich context for conceptual understanding of gene structure, regulation, and function. With an intent to create a rich learning experience in molecular genetics, we developed a semester-long course-based undergraduate research experience (CURE) using the CRISPR-Cas9 gene editing system to disrupt specific genes in the zebrafish. The course was offered to freshman students; nine students worked in four groups (two to three members per group) to design, synthesize, and test the nuclease activity of the CRISPR (Clustered Regularly Interspaced Short Palindromic Repeats)/sgRNAs for targeted disruption of specific genes in the zebrafish. Each group worked with a gene with an already known mutant phenotype that can be visually scored and a gene that had not been studied in zebrafish previously. Embedded in the course were a series of workshop-styled units or tutorials, including tours to core facilities. The focus was on introducing and developing skills that could be accommodated within the span of a semester. Each group successfully cloned at least one plasmid-encoding CRISPR/sgRNA template, visually analyzed injected embryos, and performed genotyping assays to detect CRISPR-Cas9 activity. In-class discussions, a final end-of-semester written test, and group oral presentations were assessed for an understanding of the CRISPR-Cas9 system, application of the CRISPR-Cas9 system as a gene manipulation tool, and experimental methods used to create plasmid vectors and synthesize sgRNA. In addition, poster presentations were evaluated by faculty, graduate students, and senior undergraduate students at a University research exposition. Self-reflections in the form of group conversations were video recorded. All students (9/9) distinctly showed learning gains after completing the activity, but the extent of the gains was variable, as seen from results of a written test and poster presentation assessment. Qualitative analysis of evaluations and self-reporting data indicated several gains, suggesting that all students found many aspects of the CURE valuable and gained project-specific (conceptual) and transferrable skills (science process and science identity). PMID:29904527

Dielectric monitoring of carbon nanotube network formation in curing thermosetting nanocomposites

NASA Astrophysics Data System (ADS)

Battisti, A.; Skordos, A. A.; Partridge, I. K.

2009-08-01

This paper focuses on monitoring of carbon nanotube (CNT) network development during the cure of unsaturated polyester nanocomposites by means of electrical impedance spectroscopy. A phenomenological model of the dielectric response is developed using equivalent circuit analysis. The model comprises two parallel RC elements connected in series, each of them giving rise to a semicircular arc in impedance complex plane plots. An established inverse modelling methodology is utilized for the estimation of the parameters of the corresponding equivalent circuit. This allows a quantification of the evolution of two separate processes corresponding to the two parallel RC elements. The high frequency process, which is attributed to CNT aggregates, shows a monotonic decrease in characteristic time during the cure. In contrast, the low frequency process, which corresponds to inter-aggregate phenomena, shows a more complex behaviour explained by the interplay between conductive network development and the cross-linking of the polymer.

New Help for MS Patients

NASA Technical Reports Server (NTRS)

1993-01-01

The Mark VII MicroClimate Medical Personal Cooling system enables multiple sclerosis' victims, as well as cerebral palsy, spinabifida patients and others to lower their body temperatures. Although this is not a cure, cooling can produce a dramatic improvement in symptoms. The Multiple Sclerosis Association of America has placed cool suits in MS research care centers. This technology originated in the need for cooling systems in spa@esuits. "Cool Suits" are now used by hazardous materials workers, armored vehicle crews, firefighters and crop dusters. A surgical personal cooling system has also been developed for medical personnel working in hot operating room environments.

The Continuing Umbrella of Research Experiences (CURE): a model for training underserved scientists in cancer research.

PubMed

Franco, Idalid; Bailey, LeeAnn O; Bakos, Alexis D; Springfield, Sanya A

2011-03-01

Mentoring is a critical aspect of research and training; and the adoption of a successful mentoring model for guiding researchers through the educational pipeline is lacking. The Continuing Umbrella of Research Experiences (CURE) program was established in the Comprehensive Minority Biomedical Branch; which is part of the National Cancer Institute. This program offers unique training and career development opportunities to enhance diversity in cancer research. The CURE initiative focuses on broadening the cadre of underserved investigators engaging in cancer research. CURE begins with high school students and fosters scientific, academic and research excellence throughout the trainee's educational progression. The program supports students throughout the entirety of their training career. During this period, the trainee matures into a competitive early stage investigator; capable of securing advanced research project funding in academic and industry workforces. Thus, the CURE program provides a comprehensive vehicle for training and reinforces the critical mass of underserved investigators conducting cancer research.

All-fiber optoelectronic sensor with Bragg gratings for in-situ cure monitoring

NASA Astrophysics Data System (ADS)

Cusano, Andrea; Breglio, Giovanni; Cutolo, Antonello; Calabro, Antonio M.; Giordano, Michele; Nicolais, Luigi, II

2000-08-01

Real-time, in situ monitoring for quality control of the polymer cure process is of high interest, since thermoset polymer-matrix composite are widely used in large industrial areas: aeronautical, aerospace, automotive and civil due to their low cost/low weight features. However, their final properties are strongly dependence on the processing parameters, such as temperature and pressure sequence. The key-point for advanced composite materials is the possibility to have distributed and simultaneous monitoring of chemoreological and physical properties during the cure process. To this aim, we have developed and tested an optoelectronic fiber optic sensor based on the Fresnel principle able to monitor the variations of the refractive index due to the cure process of an epoxy based resin. Experimental results have been obtained on sensor capability to monitor the cure kinetics by assuming the refractive index as reaction co-ordinate. The integration with in-fiber Bragg grating in order to measure the local temperature has been discussed and tested.

Adhesive bonded structural repair. II - Surface preparation procedures, tools, equipment and facilities

NASA Astrophysics Data System (ADS)

Wegman, Raymond F.; Tullos, Thomas R.

1993-10-01

A development status report is presented on the surface preparation procedures, tools, equipment, and facilities used in adhesively-bonded repair of aerospace and similar high-performance structures. These methods extend to both metallic and polymeric surfaces. Attention is given to the phos-anodize containment system, paint removal processes, tools for cutting composite prepreg and fabric materials, autoclaves, curing ovens, vacuum bagging, and controlled atmospheres.

Setting Performance Standards for a Cost-Effective Human Immunodeficiency Virus Cure Strategy in South Africa

PubMed Central

Paltiel, A. David; Zheng, Amy; Weinstein, Milton C.; Gaynes, Melanie R.; Wood, Robin; Freedberg, Kenneth A.; Sax, Paul E.

2017-01-01

Abstract Background. Reports of a single case of human immunodeficiency virus (HIV) eradication suggest that elimination of HIV from individuals is possible. Anticipating both increased research funding and the development of effective, durable cure technologies, we describe the circumstances under which a cure might improve survival and be cost-effective in South Africa. Methods. We adapted a simulation model comparing a hypothetical cure strategy (“Cure”) to the standard of care, lifetime antiretroviral therapy (“LifetimeART”) among adherent South Africans (58% female; mean age 33.8 years; mean CD4 257/µL; virologic suppression ≥1 year). We portrayed cure as a single intervention, producing sustained viral eradication without ART. We considered both a plausible, more imminently achievable “Baseline Scenario” and a more aspirational “Optimistic Scenario”. Inputs (Baseline/Optimistic) included the following: 50%/75% efficacy; 0.6%/0.0% fatal toxicity; 0.37%/0.085% monthly relapse over 5 years (0.185%/0.0425% per month thereafter); and $2000/$500 cost. These inputs were varied extensively in sensitivity analysis. Results. At baseline, Cure was “dominated,” yielding lower discounted life expectancy (19.31 life-years [LY] vs 19.37 LY) and greater discounted lifetime costs ($13 800 vs $13 700) than LifetimeART. Under optimistic assumptions, Cure was “cost-saving,” producing greater survival (19.91 LY) and lower lifetime costs ($11 000) than LifetimeART. Findings were highly sensitive to data assumptions, leaving little middle ground where a tradeoff existed between improved survival and higher costs. Conclusions. Only under the most favorable performance assumptions will an HIV cure strategy prove clinically and economically justifiable in South Africa. The scientific pursuit of a cure should not undermine continued expansions of access to proven, effective, and cost-effective ART. PMID:28680903

Survivability of Affordable High Temperature Polymer Matrix Composites for Propulsion Engine Components

NASA Technical Reports Server (NTRS)

Dean, Derrick; Haque, Anwar; Vaidya, Uday; Meador, Michael A. (Technical Monitor)

2003-01-01

PMR-type polyimides are regarded as state of the art high temperature polymers, due to their excellent thermo-mechanical properties and thermo-oxidative stability. One of their drawbacks, however is the inability to process them using cost-effective processing methods such as Resin Transfer Molding (RTM) and Resin Film Infusion (RFI). Development of low viscosity, high temperature polymers has been the subject of intense research. Recently, a new generation of low viscosity polyimides were synthesized by the introduction of twisted biphenyl or binapthyl groups into the backbone. This report details the progress for Year 1, which has involved acquiring samples and initiating Phases I and II of the proposed research. Specifically, studies of the process-property relationships of a series of polymers using oligomers based on 2,3,3' ,4'-biphenyltertracarboxylic dianhydride (PBDA) and a mixture of a diamine, BAX and a triamine, 1,3,5-Tris (4-aminophenoxybenzene), TAB, where the amount of TAB was varied have been initiated. The sample containing 10 percent TAB possesses a slightly higher degree of crystalline order versus that of the 20 percent TAB sample, based on x-ray diffraction studies of the b-staged oligomers. Both systems lose all of the crystalline order upon curing, however. The chemorheology has been studied as a function of the TAB content. While the magnitude of the viscosity is essentially the same for both systems, the cure kinetics of the 10 percent TAB system is faster than that for the 20 percent TAB system. The sample exhibits a melting-recrystallization-remelting behavior before the crosslinking commences. Correlation of other kinetic parameters, such as the activation energies for curing, the Tg and mechanical properties to the structure of these systems is underway. Future studies will involve characterization of mechanical and thermal properties of the pure resins and the fabrication of fiber reinforced composites using these materials.

Unraveling the chemical identity of meat pigments.

PubMed

Pegg, R B; Shahidi, F

1997-10-01

This review examines the chemistry of nitrite curing of meat and meat products as it relates to the development of cured meat color and provides a detailed account of how nitrite-free processed meats could be prepared using the preformed cooked cured-meat pigment (CCMP). Thus, a chemical description of meat color, both raw and cooked, and characterization of nitrosylheme pigments follows. Based on electron paramagnetic resonance (EPR), visible and infrared spectroscopic studies, evidence has been provided to support the hypothesis that the chemical structure of the preformed CCMP is identical to that of the pigment prepared in situ after thermal processing of nitrite-cured meat and is in fact a mononitrosylheme complex. An appendix, which describes the basic principles of EPR spectroscopy used in the context of this review, is attached.

Cure4Kids for Kids: school-based cancer education outreach.

PubMed

Van Kirk Villalobos, Aubrey; Quintana, Yuri; Ribeiro, Raul C

2012-01-01

In 2006, St. Jude Children's Research Hospital created Cure4Kids for Kids, a school-based outreach program. The objectives of this community education program are to teach about cancer and healthy lifestyles and to inspire an interest in science and health-related careers. A multidisciplinary team of St. Jude and outside experts developed and pilot tested age-appropriate educational materials and activities with 4th grade students. Eight schools and more than 800 children have participated in the program since 2006. Teachers and students have demonstrated a very positive response to the program for it being both fun and educational. Cure4Kids for Kids resources have been collected into a teacher's kit and are now freely available online at www.cure4kids.org/kids.

No-Oven, No-Autoclave Composite Processing

NASA Technical Reports Server (NTRS)

Rauscher, Michael D.

2015-01-01

Very large composite structures, such as those used in NASA's Space Launch System, push the boundaries imposed by current autoclaves. New technology is needed to maintain composite performance and free manufacturing engineers from the restraints of curing equipment size limitations. Recent efforts on a Phase II project by Cornerstone Research Group, Inc. (CRG), have advanced the technology and manufacturing readiness levels of a unique two-part epoxy resin system. Designed for room-temperature infusion of a dry carbon preform, the system includes a no-heat-added cure that delivers 350 F composite performance in a matter of hours. This no-oven, no-autoclave (NONA) composite processing eliminates part-size constraints imposed by infrastructure and lowers costs by increasing throughput and reducing capital-specific, process-flow bottlenecks. As a result of the Phase II activity, NONA materials and processes were used to make high-temperature composite tooling suitable for further production of carbon-epoxy laminates and honeycomb/ sandwich-structure composites with an aluminum core. The technology platform involves tooling design, resin infusion processing, composite part design, and resin chemistry. The various technology elements are combined to achieve a fully cured part. The individual elements are not unusual, but they are combined in such a way that enables proper management of the heat generated by the epoxy resin during cure. The result is a self-cured carbon/ epoxy composite part that is mechanically and chemically stable at temperatures up to 350 F. As a result of the successful SBIR effort, CRG has launched NONA Composites as a spinoff subsidiary. The company sells resin to end users, fabricates finished goods for customers, and sells composite tooling made with NONA materials and processes to composite manufacturers.

Effect of etch-and-rinse and self-etching adhesive systems on hardness uniformity of resin cements after glass fiber post cementation

PubMed Central

Grande da Cruz, Fernanda Zander; Grande, Christiana Zander; Roderjan, Douglas Augusto; Galvão Arrais, César Augusto; Bührer Samra, Adriana Postiglione; Calixto, Abraham Lincoln

2012-01-01

Objective To evaluate the effects of etch-and-rinse and self-etching adhesive systems on Vickers hardness (VHN) uniformity of dual-cured resin cements after fiber post cementation. Methods: Fifty glass fiber posts were cemented into bovine roots using the following cementing systems: Prime&Bond 2.1 Dual Cure and Enforce with light-activation (PBDC-LCEN); Prime&Bond 2.1 and Enforce with light-activation (PB-CLEN); Prime&Bond 2.1 Dual Cure and Enforce without light exposure (PBDC-SCEN); ED Primer and Panavia 21 (ED-SCPN); and Clearfil SE Bond and Panavia 21 (CF-SCPN). The roots were stored in distilled water for 72 h and transversely sectioned into thirds (coronal, medium, and apical). The VHN values of the resin cement layers were measured close to the post and to the dentin wall on the transversely sectioned flat surfaces. The results were analyzed by three-way repeated measures analysis of variance (ANOVA) and Tukey’s post-hoc test (pre-set alpha of 5%). Results: Most resin cements presented higher VHN values near the post than near the dentin wall. The ED-SCPN group showed the highest VHN values regardless of the root third, while the self-cured group PBDC-SCEN exhibited the lowest values. The resin cements from the light-activated groups PBDC-LCEN and PB-LCEN showed lower VHN values at the apical third than at the coronal third. The VHN values were not influenced by the root third in self-cured groups PBDC-SCEN, ED-SCPN, and ED-SCPN. Conclusion: Depending on the product, bonding agents might promote changes in hardness uniformity of resin cements after post cementation. PMID:22904652

Collaborating with Undergraduates To Contribute to Biochemistry Community Resources.

PubMed

Haas, Kathryn L; Heemstra, Jennifer M; Medema, Marnix H; Charkoudian, Louise K

2018-01-30

Course-based undergraduate research experiences (CUREs) have gained traction as effective ways to expand the impact of undergraduate research while fulfilling pedagogical goals. In this Perspective, we present innovative ways to incorporate fundamental benefits and principles of CUREs into a classroom environment through information/technology-based research projects that lead to student-generated contributions to digital community resources (CoRes). These projects represent an attractive class of CUREs because they are less resource-intensive than laboratory-based CUREs, and the projects align with the expectations of today's students to create rapid and publicly accessible contributions to society. We provide a detailed discussion of two example types of CoRe projects that can be implemented in courses to impact research and education at the chemistry-biology interface: bioinformatics annotations and development of educational tools. Finally, we present current resources available for faculty interested in incorporating CUREs or CoRe projects into their pedagogical practices. In sharing these stories and resources, we hope to lower the barrier for widespread adoption of CURE and CoRe approaches and generate discussions about how to utilize the classroom experience to make a positive impact on our students and the future of the field of biochemistry.

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

Pern, F.J.; Glick, S.H.; Czanderna, A.W.

Results from extensive studies of the commercial ethylene vinyl acetate (EVA) formulations show that the UV absorber and curing-generated UV-excitable, {alpha},{beta}-unsaturated carbonyl chromophores facilitate the EVA discoloration, which is further enhanced by curing-generated acetic acid and probably residual peroxide curing agent also. Formation and concentration of the UV-excitable chromophores are substantially promoted by the antioxidant, Naugard P. The discoloration rate is greater under higher UV light intensity and temperatures. Heating in the dark at elevated temperatures (e.g., 85&hthinsp;{degree}C) in the air for {approximately}200 days only results in light yellowing. The discoloration reactions compete with photobleaching reactions, which destroy curing-generated chromophoresmore » and result in non-discoloring of EVA. By using better performance stabilizers to minimize the curing-generated UV-excitable chromophores, a new fast curing agent, and no UV absorber, the NREL-developed EVA formulations show a superior photothermal stability against browning to the commercial counterparts. Alternatively, the discoloration rate of the commercial EVA pottants can be considerably reduced by using UV-filtering glass superstrates that largely inhibit the UV-induced photooxidation reactions, or completely eliminated by using air-permeable polymer superstrate films that enable photobleaching reactions. {copyright} {ital 1999 American Institute of Physics.}« less

Vanilla--its science of cultivation, curing, chemistry, and nutraceutical properties.

PubMed

Anuradha, Krushnamurthy; Shyamala, Bellur Nanjundaiah; Naidu, Madeneni Madhava

2013-01-01

Vanilla is a tropical orchid belonging to the family Orchidaceae and it is mainly used in food, perfumery, and pharmaceutical preparations. The quality of the bean depends on the volatile constituent's, viz., the vanillin content, the species of the vine used, and the processing conditions adopted. Hence, proper pollination during flowering and curing by exercising utmost care are the important aspects of vanilla cultivation. There are different methods of curing, and each one is unique and named after the places of its origin like Mexican process and Bourbon process. Recently, Central Food Technological Research Institute, Mysore has developed know-how of improved curing process, where the green vanilla beans are cured immediately after harvest and this process takes only 32 days, which otherwise requires minimum of 150-180 days as reported in traditional curing methods. Vanillin is the most essential component of the 200 and odd such compounds present in vanilla beans. Vanillin as such has not shown any antioxidant properties, it is along with other compounds has got nutraceutical properties and therefore its wide usage. The medicinal future of vanilla may definitely lie in further research on basic science and clinical studies on the constituents and their mechanism of action.

[Methods Used for Monitoring Cure Reactions in Real-time in an Autoclave

NASA Technical Reports Server (NTRS)

Cooper, John B.; Wise, Kent L.; Jensen, Brian J. (Technical Monitor)

2000-01-01

The goal of the research was to investigate methods for monitoring cure reactions in real-time in an autoclave. This is of particular importance to NASA Langley Research Center because polyimides were proposed for use in the High Speed Civil Transport (HSCT) program. Understanding the cure chemistry behind the polyimides would allow for intelligent processing of the composites made from their use. This work has led to two publications in peer-reviewed journals and a patent. The journal articles are listed as Appendix A which is on the instrument design of the research and Appendix B which is on the cure chemistry. Also, a patent has been awarded for the instrumental design developed under this grant which is given as Appendix C. There has been a significant amount of research directed at developing methods for monitoring cure reactions in real-time within the autoclave. The various research efforts can be categorized as methods providing either direct chemical bonding information or methods that provide indirect chemical bonding information. Methods falling into the latter category are fluorescence, dielectric loss, ultrasonic and similar type methods. Correlation of such measurements with the underlying chemistry is often quite difficult since these techniques do not allow monitoring of the curing chemistry which is ultimately responsible for material properties. Direct methods such as vibrational spectroscopy, however, can often be easily correlated with the underlying chemistry of a reaction. Such methods include Raman spectroscopy, mid-IR absorbance, and near-IR absorbance. With the recent advances in fiber-optics, these spectroscopic techniques can be applied to remote on-line monitoring.

[Transgenic cell cultures that synthesize neurotrophic factors and the possibility of therapeutic use of its cells].

PubMed

Pavlova, G V; Kanaĭkina, N N; Panteleev, D Iu; Okhotin, V E; Revishchin, A V

2012-01-01

Under the leadership of Corresponding Member of the Russian Academy of Sciences L.I. Korochkin, the Laboratory of Neurogenetics and Developmental Genetics (Institute of Gene Biology, Russian Academy of Sciences) for many years has been conducting studies of nervous system development, neural cell differentiation, and application of gene and cell technology to cure neurodegenerative diseases. The results of the study initiated by L.I. Korochkin and continued by his scientific successors support the direction of allocation of transgenic neurotrofic factors and heat-shock proteins as neuroprotectors for cell therapy. Potential for usage of promoter of HSP70 heat-shock gene of Drosophila to create transgenic constructs for therapy has been shown. Further improvement of technology of nonvirus transfer for therapeutic genes, as well as production of multicomponent genetic constructs coding several therapeutic factors with synergy effect, would stimulate creation of efficient cell medicals to cure neurodegenerative diseases.

Low cost tooling material and process for graphite and Kevlar composites

NASA Technical Reports Server (NTRS)

Childs, William I.

1987-01-01

An Extruded Sheet Tooling Compound (ESTC) was developed for use in quickly building low cost molds for fabricating composites. The ESTC is a very highly mineral-filled resin system formed into a 6 mm thick sheet. The sheet is laid on the pattern, vacuum (bag) is applied to remove air from the pattern surface, and the assembly is heat cured. The formed ESTC is then backed and/or framed and ready for use. The cured ESTC exhibits low coefficient of thermal expansion and maintains strength at temperatures of 180 to 200 C. Tools were made and used successfully for: Compression molding of high strength epoxy sheet molding compound, stamping of aluminum, resin transfer molding of polyester, and liquid resin molding of polyester. Several variations of ESTC can be made for specific requirements. Higher thermal conductivity can be achieved by using an aluminum particle filler. Room temperature gel is possible to allow use of foam patterns.

Evaluation of selected antiprotozoal drugs in the Babesia microti-hamster model.

PubMed Central

Marley, S E; Eberhard, M L; Steurer, F J; Ellis, W L; McGreevy, P B; Ruebush, T K

1997-01-01

The presently used therapy for Babesia microti infections, a combination of quinine and clindamycin, does not always result in parasitologic cures. To identify possible alternative chemotherapeutic agents for such infections, we screened, in the hamster-B. microti system, 12 antiprotozoal drugs that have either recently been released for human use or were in experimental stages of development at the Walter Reed Army Institute of Research for the treatment of malaria and leishmaniasis. Several well-recognized antimalarial drugs, such as mefloquine, halofantrine, artesunate, and artelenic acid, exhibited little or no effect on parasitemia. Two 8-aminoquinolines, WR006026 [8-(6-diethylaminohexylamino)-6-methoxy-4-methylquinoline dihydrochloride] and WR238605 [8-[(4-amino-1-methylbutyl)amino]-2,6-dimethoxy-4-methyl-5 -(3-trifluoromethylphenoxy-7) quinoline succinate], produced clearance of patent parasitemia. Furthermore, blood from infected hamsters treated with WR238605 via an intramuscular injection failed to infect naive hamsters on subpassage, thus producing a parasitologic cure. These two compounds merit further screening in other systems and may prove useful in treating human babesiosis. PMID:8980761

A New Kind of Curing

NASA Technical Reports Server (NTRS)

2001-01-01

A new curing method using automated tape placement (ATP) with electron beam (EB), or e-beam, produces a combination known as in situ e-beam curing. Through a Small Business Innovation Research (SBIR) contract from NASA's Marshall Space Flight Center, Science Research Laboratory, Inc., created the in situ e-beam curing technique, which uses a low-energy electron beam gun to cure various composite materials. One important benefit is the technique's utilization of room temperature curing, which lessens the chance of mismatching the thermal expansion coefficients of different materials. For instance, metals and composites will expand at different rates when heated, but the low-energy e-beam gun reduces the expansion differential. Using a low-energy gun also results in less x-ray shielding, significantly reduced capital costs, reduced facility space, and increased processing capabilities for larger parts. However, using a low-energy gun also means that each tape layer is treated individually because the gun can penetrate only one layer at a time. The e-beam gun emits lower energy x-rays, which are more easily shielded than those emitted by previous guns. The low-energy system is relatively portable due to its light weight and small size. The gun weighs about 70 pounds and can be easily mounted on a robotic arm or an ATP head.

High energy electron beam curing of epoxy resin systems incorporating cationic photoinitiators

DOEpatents

Janke, C.J.; Lopata, V.J.; Havens, S.J.; Dorsey, G.F.; Moulton, R.J.

1999-03-02

A mixture of epoxy resins such as a semi-solid triglycidyl ether of tris (hydroxyphenyl) methane and a low viscosity bisphenol A glycidyl ether and a cationic photoinitiator such as a diaryliodonium salt is cured by irradiating with a dosage of electron beams from about 50 to about 150 kGy, forming a cross-linked epoxy resin polymer.

High energy electron beam curing of epoxy resin systems incorporating cationic photoinitiators

DOEpatents

Janke, Christopher J.; Lopata, Vincent J.; Havens, Stephen J.; Dorsey, George F.; Moulton, Richard J.

1999-01-01

A mixture of epoxy resins such as a semi-solid triglycidyl ether of tris (hydroxyphenyl) methane and a low viscosity bisphenol A glycidyl ether and a cationic photoinitiator such as a diaryliodonium salt is cured by irradiating with a dosage of electron beams from about 50 to about 150 kGy, forming a cross-linked epoxy resin polymer.

Effects of cure temperature, electron radiation, and thermal cycling on P75/930 composites

NASA Technical Reports Server (NTRS)

Funk, Joan G.

1990-01-01

Graphite/epoxy composites are candidates for future space structures due to high stiffness and dimensional stability requirements of these structures. Typical graphite/epoxy composites are brittle and have high residual stresses which often result in microcracking during the thermal cycling typical of the space environment. Composite materials used in geosynchronous orbit applications will also be exposed to high levels of radiation. The purpose of the present study was to determine the effects of cure temperature and radiation exposure on the shear strength and thermal cycling-induced microcrack density of a high modulus, 275 F cure epoxy, P75/930. The results from the P75/930 are compared to previously reported data on P75/934 and T300/934 where 934 is a standard 350 F cure epoxy. The results of this study reveal that P75/930 is significantly degraded by total doses of electron radiation greater than 10(exp 8) rads and by thermally cycling between -250 F and 150 F. The P75/930 did not have improved microcrack resistance over the P75/934, and the 930 resin system appears to be more sensitive to electron radiation-induced degradation than the 934 resin system.

Systemic antifungals to treat onychomycosis in children: a systematic review.

PubMed

Gupta, Aditya K; Paquet, Maryse

2013-01-01

Because of the low prevalence of onychomycosis in children, little is known about the efficacy and safety of systemic antifungals in this population. PubMed and Embase databases and the references of related publications were searched in March 2012 for clinical trials (CTs), retrospective analyses (RAs), and case reports (CRs) on the use of systemic antifungals for onychomycosis in children (<18 years). Twenty-six studies (5 CTs, 3 RAs, and 18 CRs) were published between 1976 and 2011. Most of these studies reported the use of systemic terbinafine and itraconazole for the treatment of onychomycosis in children. Therapy with systemic antifungals alone in children ages 1 to 17 years resulted in a complete cure rate of 70.8% (n = 151), whereas combined systemic and topical antifungal therapy in one infant and 19 children age 8 and older resulted in a complete cure rate of 80.0% (n = 20). The efficacy and safety profiles of terbinafine, itraconazole, griseofulvin, and fluconazole in children were similar to those previously reported for adults. In conclusion, based on the little information available on onychomycosis in children, systemic antifungal therapies in children are safe and cure rates are similar to the rates achieved in adults. © 2012 Wiley Periodicals, Inc.

Practical application of cure mixture model for long-term censored survivor data from a withdrawal clinical trial of patients with major depressive disorder.

PubMed

Arano, Ichiro; Sugimoto, Tomoyuki; Hamasaki, Toshimitsu; Ohno, Yuko

2010-04-23

Survival analysis methods such as the Kaplan-Meier method, log-rank test, and Cox proportional hazards regression (Cox regression) are commonly used to analyze data from randomized withdrawal studies in patients with major depressive disorder. However, unfortunately, such common methods may be inappropriate when a long-term censored relapse-free time appears in data as the methods assume that if complete follow-up were possible for all individuals, each would eventually experience the event of interest. In this paper, to analyse data including such a long-term censored relapse-free time, we discuss a semi-parametric cure regression (Cox cure regression), which combines a logistic formulation for the probability of occurrence of an event with a Cox proportional hazards specification for the time of occurrence of the event. In specifying the treatment's effect on disease-free survival, we consider the fraction of long-term survivors and the risks associated with a relapse of the disease. In addition, we develop a tree-based method for the time to event data to identify groups of patients with differing prognoses (cure survival CART). Although analysis methods typically adapt the log-rank statistic for recursive partitioning procedures, the method applied here used a likelihood ratio (LR) test statistic from a fitting of cure survival regression assuming exponential and Weibull distributions for the latency time of relapse. The method is illustrated using data from a sertraline randomized withdrawal study in patients with major depressive disorder. We concluded that Cox cure regression reveals facts on who may be cured, and how the treatment and other factors effect on the cured incidence and on the relapse time of uncured patients, and that cure survival CART output provides easily understandable and interpretable information, useful both in identifying groups of patients with differing prognoses and in utilizing Cox cure regression models leading to meaningful interpretations.

Discovery – Methotrexate: Chemotherapy Treatment for Cancer

Cancer.gov

Prior to the 1950s, treatment for the majority of cancers was limited to either surgery or the use of radiation. The discovery of the use of methotrexate in curing a rare cancer marked the first time a cancer had been cured. This led to the development of many of today’s common cancer treatments.

The Laboratory Course Assessment Survey: A Tool to Measure Three Dimensions of Research-Course Design

ERIC Educational Resources Information Center

Corwin, Lisa A.; Runyon, Christopher; Robinson, Aspen; Dolan, Erin L.

2015-01-01

Course-based undergraduate research experiences (CUREs) are increasingly being offered as scalable ways to involve undergraduates in research. Yet few if any design features that make CUREs effective have been identified. We developed a 17-item survey instrument, the Laboratory Course Assessment Survey (LCAS), that measures students' perceptions…

Composite lamination method

NASA Technical Reports Server (NTRS)

Dickerson, G. E. (Inventor)

1977-01-01

A process was developed for preparing relatively thick composite laminate structure wherein thin layers of prepreg tapes are assembled, these thin layers are cut into strips that are partially cured, and stacked into the desired thickness with uncured prepreg disposed between each layer of strips. The formed laminate is finally cured and thereafter machined to the desired final dimensions.

Study of microtip-based extraction and purification of DNA from human samples for portable devices

NASA Astrophysics Data System (ADS)

Fotouhi, Gareth

DNA sample preparation is essential for genetic analysis. However, rapid and easy-to-use methods are a major challenge to obtaining genetic information. Furthermore, DNA sample preparation technology must follow the growing need for point-of-care (POC) diagnostics. The current use of centrifuges, large robots, and laboratory-intensive protocols has to be minimized to meet the global challenge of limited access healthcare by bringing the lab to patients through POC devices. To address these challenges, a novel extraction method of genomic DNA from human samples is presented by using heat-cured polyethyleneimine-coated microtips generating a high electric field. The microtip extraction method is based on recent work using an electric field and capillary action integrated into an automated device. The main challenges to the method are: (1) to obtain a stable microtip surface for the controlled capture and release of DNA and (2) to improve the recovery of DNA from samples with a high concentration of inhibitors, such as human samples. The present study addresses these challenges by investigating the heat curing of polyethyleneimine (PEI) coated on the surface of the microtip. Heat-cured PEI-coated microtips are shown to control the capture and release of DNA. Protocols are developed for the extraction and purification of DNA from human samples. Heat-cured PEI-coated microtip methods of DNA sample preparation are used to extract genomic DNA from human samples. It is discovered through experiment that heat curing of a PEI layer on a gold-coated surface below 150°C could inhibit the signal of polymerase chain reaction (PCR). Below 150°C, the PEI layer is not completely cured and dissolved off the gold-coated surface. Dissolved PEI binds with DNA to inhibit PCR. Heat curing of a PEI layer above 150°C on a gold-coated surface prevents inhibition to PCR and gel electrophoresis. In comparison to gold-coated microtips, the 225°C-cured PEI-coated microtips improve the recovery of DNA to 45% efficiency. Furthermore, the 225°C-cured PEI-coated microtips recover more DNA than gold-coated microtips when the surface is washed. Heat-cured (225°C) PEI-coated microtips are used for the recovery of human genomic DNA from whole blood. A washing protocol is developed to remove inhibiting particles bound to the PEI-coated microtip surface after DNA extraction. From 1.25 muL of whole blood, an average of 1.83 ng of human genomic DNA is captured, purified, and released using a 225°C-cured PEI-coated microtip in less than 30 minutes. The extracted DNA is profiled by short tandem repeat analysis (STR). For forensic and medical applications, genomic DNA is extracted from dried samples using heat-cured PEI-coated microtips that are integrated into an automated device. DNA extraction from dried samples is critical for forensics. The use of dried samples in the medical field is increasing because dried samples are convenient for storage, biosafety, and contamination. The main challenge is the time required to properly extract DNA in a purified form. Typically, a 1 hour incubation period is required to complete this process. Overnight incubation is sometimes necessary. To address this challenge, a pre-extraction washing step is investigated to remove inhibiting particles from dried blood spots (DBS) before DNA is released from dried form into solution for microtip extraction. The developed protocol is expanded to extract DNA from a variety of dried samples including nasal swabs, buccal swabs, and other forensic samples. In comparison to a commercial kit, the microtip-based extraction reduced the processing time from 1.5 hours to 30 minutes or less with an equivalent concentration of extracted DNA from dried blood spots. The developed assay will benefit genetic studies on newborn screening, forensic investigation, and POC diagnostics.

High-Temperature Adhesive Strain Gage Developed

NASA Technical Reports Server (NTRS)

Pereira, J. Michael; Roberts, Gary D.

1997-01-01

Researchers at the NASA Lewis Research Center have developed a unique strain gage and adhesive system for measuring the mechanical properties of polymers and polymer composites at elevated temperatures. This system overcomes some of the problems encountered in using commercial strain gages and adhesives. For example, typical commercial strain gage adhesives require a postcure at temperatures substantially higher than the maximum test temperature. The exposure of the specimen to this temperature may affect subsequent results, and in some cases may be higher than the glass-transition temperature of the polymer. In addition, although typical commercial strain gages can be used for short times at temperatures up to 370 C, their long-term use is limited to 230 C. This precludes their use for testing some high-temperature polyimides near their maximum temperature capability. Lewis' strain gage and adhesive system consists of a nonencapsulated, unbacked gage grid that is bonded directly to the polymer after the specimen has been cured but prior to the normal postcure cycle. The gage is applied with an adhesive specially formulated to cure under the specimen postcure conditions. Special handling, mounting, and electrical connection procedures were developed, and a fixture was designed to calibrate each strain gage after it was applied to a specimen. A variety of tests was conducted to determine the performance characteristics of the gages at elevated temperatures on PMR-15 neat resin and titanium specimens. For these tests, which included static tension, thermal exposure, and creep tests, the gage and adhesive system performed within normal strain gage specifications at 315 C. An example of the performance characteristics of the gage can be seen in the figure, which compares the strain gage measurement on a polyimide specimen at 315 C with an extensometer measurement.

Predictive Modeling of Fast-Curing Thermosets in Nozzle-Based Extrusion

NASA Technical Reports Server (NTRS)

Xie, Jingjin; Randolph, Robert; Simmons, Gary; Hull, Patrick V.; Mazzeo, Aaron D.

2017-01-01

This work presents an approach to modeling the dynamic spreading and curing behavior of thermosets in nozzle-based extrusions. Thermosets cover a wide range of materials, some of which permit low-temperature processing with subsequent high-temperature and high-strength working properties. Extruding thermosets may overcome the limited working temperatures and strengths of conventional thermoplastic materials used in additive manufacturing. This project aims to produce technology for the fabrication of thermoset-based structures leveraging advances made in nozzle-based extrusion, such as fused deposition modeling (FDM), material jetting, and direct writing. Understanding the synergistic interactions between spreading and fast curing of extruded thermosetting materials will provide essential insights for applications that require accurate dimensional controls, such as additive manufacturing [1], [2] and centrifugal coating/forming [3]. Two types of thermally curing thermosets -- one being a soft silicone (Ecoflex 0050) and the other being a toughened epoxy (G/Flex) -- served as the test materials in this work to obtain models for cure kinetics and viscosity. The developed models align with extensive measurements made with differential scanning calorimetry (DSC) and rheology. DSC monitors the change in the heat of reaction, which reflects the rate and degree of cure at different crosslinking stages. Rheology measures the change in complex viscosity, shear moduli, yield stress, and other properties dictated by chemical composition. By combining DSC and rheological measurements, it is possible to establish a set of models profiling the cure kinetics and chemorheology without prior knowledge of chemical composition, which is usually necessary for sophisticated mechanistic modeling. In this work, we conducted both isothermal and dynamic measurements with both DSC and rheology. With the developed models, numerical simulations yielded predictions of diameter and height of droplets, along with width and height of extruded lines cured at varied temperatures. Experimental results carried out on a goniometric platform and a nozzle-based 3D printer showed agreement with the numerical simulations. Finally, this presentation will show how the models are adaptable to the planning of tool paths and designs in additive manufacturing.

Effect of saliva decontamination procedures on shear bond strength of a one-step adhesive system.

PubMed

Ülker, E; Bilgin, S; Kahvecioğlu, F; Erkan, A I

2017-09-01

To evaluate the effect of different saliva decontamination procedures on the shear bond strength of a one-step universal adhesive system (Single Bond™ Universal Adhesive, 3M ESPE, St. Paul, MN, USA). The occlusal surfaces of 75 human third molars were ground to expose dentin. The teeth were divided into the following groups: Group 1 (control group): Single Bond™ Universal Adhesive was applied to the prepared tooth according to the manufacturer's recommendations and light cured; no contamination procedure was performed. Group 2: Bonding, light curing, saliva contamination, and dry. Group 3: Bonding, light curing, saliva contamination, rinse, and dry. Group 4: After the procedure performed in Group 2, reapplication of bonding. Group 5: After the procedure performed in Group 3, reapplication of bonding. Then, composite resins were applied with cylindrical-shaped plastic matrixes and light cured. For shear bond testing, a notch-shaped force transducer apparatus was applied to each specimen at the interface between the tooth and composite until failure occurred. The data were statistically analyzed using one-way ANOVA. One-way ANOVA revealed significant differences in shear bond strength between the control group and experimental Groups 2 and 4 (P < 0.05). No significant difference was found for experimental Groups 3 and 5 when compared to the control group (P > 0.05). The present in vitro study showed that water rinsing is necessary if cured adhesive resin is contaminated with saliva to ensure adequate bond strength.

Engineering hematopoietic stem cells toward a functional cure of human immunodeficiency virus infection.

PubMed

Wang, Jianbin; Holmes, Michael C

2016-11-01

The battle with human immunodeficiency virus (HIV) has been ongoing for more than 30 years, and although progress has been made, there are still significant challenges remaining. A few unique features render HIV to be one of the toughest viruses to conquer in the modern medicine era, such as the ability to target the host immune system, persist by integrating into the host genome and adapt to a hostile environment such as a single anti-HIV medication by continuously evolving. The finding of combination anti-retroviral therapy (cART) about 2 decades ago has transformed the treatment options for HIV-infected patients and significantly improved patient outcomes. However, finding an HIV cure has proven to be extremely challenging with the only known exception being the so-called "Berlin patient," whose immune system was replaced by stem cell transplants from a donor missing one of HIV's key co-receptors (CCR5). The broad application of this approach is limited by the requirement of an HLA-matched donor who is also homozygous for the rare CCR5 delta32 deletion. On the other hand, the Berlin patient provided the proof of concept of a potential cure for HIV using HIV-resistant hematopoietic stem cells (HSCs), revitalizing the hope to find an HIV cure that is broadly applicable. Here we will review strategies and recent attempts to engineer HIV-resistant HSCs as a path to an HIV cure. Copyright © 2016 International Society for Cellular Therapy. Published by Elsevier Inc. All rights reserved.

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

Li, Yuzhan; Zhang, Yuehong; Rios, Orlando

In this study, a liquid crystalline epoxy network (LCEN) with exchangeable disulfide bonds is synthesized by polymerizing a biphenyl-based epoxy monomer with an aliphatic dicarboxylic acid curing agent containing a disulfide bond. The effect of disulfide bonds on curing behavior and liquid crystalline (LC) phase formation of the LCEN is investigated. The presence of the disulfide bonds results in an increase in the reaction rate, leading to a reduction in liquid crystallinity of the LCEN. In order to promote LC phase formation and stabilize the self-assembled LC domains, a similar aliphatic dicarboxylic acid without the disulfide bond is used asmore » a co-curing agent to reduce the amount of exchangeable disulfide bonds in the system. After optimizing the molar ratio of the two curing agents, the resulting LCEN exhibits improved reprocessability and recyclability because of the disulfide exchange reactions, while preserving LC properties, such as the reversible LC phase transition and macroscopic LC orientation, for shape memory applications.« less

Subtle cognitive impairments in patients with long-term cure of Cushing's disease.

PubMed

Tiemensma, Jitske; Kokshoorn, Nieke E; Biermasz, Nienke R; Keijser, Bart-Jan S A; Wassenaar, Moniek J E; Middelkoop, Huub A M; Pereira, Alberto M; Romijn, Johannes A

2010-06-01

Active Cushing's disease is associated with cognitive impairments. We hypothesized that previous hypercortisolism in patients with Cushing's disease results in irreversible impairments in cognitive functioning. Therefore, our aim was to assess cognitive functioning after long-term cure of Cushing's disease. Cognitive assessment consisted of 11 tests, which evaluated global cognitive functioning, memory, and executive functioning. We included 74 patients cured of Cushing's disease and 74 controls matched for age, gender, and education. Furthermore, we included 54 patients previously treated for nonfunctioning pituitary macroadenomas (NFMA) and 54 controls matched for age, gender, and education. Compared with NFMA patients, patients cured from Cushing's disease had lower scores on the Mini Mental State Examination (P = 0.001), and on the memory quotient of the Wechsler Memory Scale (P = 0.050). Furthermore, patients cured from Cushing's disease tended to recall fewer words on the imprinting (P = 0.013), immediate recall (P = 0.012), and delayed recall (P = 0.003) trials of the Verbal Learning Test of Rey. On the Rey Complex Figure Test, patients cured from Cushing's disease had lower scores on both trials (P = 0.002 and P = 0.007) compared with NFMA patients. Patients cured from Cushing's disease also made fewer correct substitutions on the Letter-Digit Substitution Test (P = 0.039) and came up with fewer correct patterns on the Figure Fluency Test (P = 0.003) compared with treated NFMA patients. Cognitive function, reflecting memory and executive functions, is impaired in patients despite long-term cure of Cushing's disease. These observations indicate irreversible effects of previous hypercortisolism on cognitive function and, thus, on the central nervous system. These observations may also be of relevance for patients treated with high-dose exogenous glucocorticoids.

Comparison of halogen, plasma and LED curing units.

PubMed

Nomoto, Rie; McCabe, John F; Hirano, Susumu

2004-01-01

This study evaluated the characteristics of two kinds of recently developed light-curing unit; plasma arc and blue light emitting diodes (LED), in comparison with a conventional tungsten-halogen light-curing unit. The light intensity and spectral distribution of light from these light-curing units, the temperature rise of the bovine enamel surface and the depth of cure of composites exposed to each unit were investigated. The light intensity and depth of cure were determined according to ISO standards. The spectral distributions of emitted light were measured using a spectro-radiometer. The temperature increase induced by irradiation was measured by using a thermocouple. Generally, light intensities in the range 400-515 nm emitted from the plasma arc were greater than those from other types. Light in the UV-A region was emitted from some plasma arc units. The required irradiation times were six to nine seconds for the plasma arc units and 40 to 60 seconds for the LED units to create a depth of cure equal to that produced by the tungsten-halogen light with 20 seconds of irradiation. The temperature increased by increasing the irradiation time for every light-curing unit. The temperature increases were 15 degrees C to 60 degrees C for plasma arc units, around 15 degrees C for a conventional halogen unit and under 10 degrees C for LED units. Both the plasma arc and LED units required longer irradiation times than those recommended by their respective manufacturers. Clinicians should be aware of potential thermal rise and UV-A hazard when using plasma arc units.

Development and characterization of orthotropic-birefringent materials

NASA Technical Reports Server (NTRS)

Daniel, I. M.; Koller, G. M.; Niiro, T.

1984-01-01

Materials were selected and fabrication procedures developed for orthotropic birefringent materials. An epoxy resin (Maraset 658/558 system) was selected as the matrix material. Fibers obtained from style 3733 glass cloth and type 1062 glass roving were used as reinforcement. Two different fabrication procedures were used. In the first one, layers of unidirectional fibers removed from the glass cloth were stacked, impregnated with resin, bagged and cured in the autoclave at an elevated temperature. In the second procedure, the glass roving was drywound over metal frames, impregnated with resin and cured at room temperature under pressure and vacuum in an autoclave. Unidirectional, angle-ply and quasi-isotropic laminates of two thicknesses and with embedded flaws were fabricated. The matrix and the unidirectional glass/epoxy material were fully characterized. The density, fiber volume ratio, mechanical, and optical properties were determined. The fiber volume ratio was over 0.50. Birefringent properties were in good agreement with predictions based on a stress proportioning concept and also, with one exception, with properties predicted by a finite element analysis. Previously announced in STAR as N81-26183

Mechanical Reinforcement of Epoxy Composites with Carbon Fibers and HDPE

NASA Astrophysics Data System (ADS)

He, R.; Chang, Q.; Huang, X.; Li, J.

2018-01-01

Silanized carbon fibers (CFs) and a high-density polyethylene with amino terminal groups (HDPE) were introduced into epoxy resins to fabricate high-performance composites. A. mechanical characterization of the composites was performed to investigate the effect of CFs in cured epoxy/HDPE systems. The composites revealed a noticeable improvement in the tensile strength, elongation at break, flexural strength, and impact strength in comparison with those of neat epoxy and cured epoxy/HDPE systems. SEM micrographs showed that the toughening effect could be explained by yield deformations, phase separation, and microcracking.

Method of controlling a resin curing process. [for fiber reinforced composites

NASA Technical Reports Server (NTRS)

Webster, Charles Neal (Inventor); Scott, Robert O. (Inventor)

1989-01-01

The invention relates to an analytical technique for controlling the curing process of fiber-reinforced composite materials that are formed using thermosetting resins. The technique is the percent gel method and involves development of a time-to-gel equation as a function of temperature. From this equation a rate-of-gel equation is then determined, and a percent gel is calculated which is the product of rate-of-gel times time. Percent gel accounting is used to control the proper pressure application point in an autoclave cure process to achieve desired properties in a production composite part.

Molecular Modeling of Aerospace Polymer Matrices Including Carbon Nanotube-Enhanced Epoxy

NASA Astrophysics Data System (ADS)

Radue, Matthew S.

Carbon fiber (CF) composites are increasingly replacing metals used in major structural parts of aircraft, spacecraft, and automobiles. The current limitations of carbon fiber composites are addressed through computational material design by modeling the salient aerospace matrix materials. Molecular Dynamics (MD) models of epoxies with and without carbon nanotube (CNT) reinforcement and models of pure bismaleimides (BMIs) were developed to elucidate structure-property relationships for improved selection and tailoring of matrices. The influence of monomer functionality on the mechanical properties of epoxies is studied using the Reax Force Field (ReaxFF). From deformation simulations, the Young's modulus, yield point, and Poisson's ratio are calculated and analyzed. The results demonstrate an increase in stiffness and yield strength with increasing resin functionality. Comparison between the network structures of distinct epoxies is further advanced by the Monomeric Degree Index (MDI). Experimental validation demonstrates the MD results correctly predict the relationship in Young's moduli for all epoxies modeled. Therefore, the ReaxFF is confirmed to be a useful tool for studying the mechanical behavior of epoxies. While epoxies have been well-studied using MD, there has been no concerted effort to model cured BMI polymers due to the complexity of the network-forming reactions. A novel, adaptable crosslinking framework is developed for implementing 5 distinct cure reactions of Matrimid-5292 (a BMI resin) and investigating the network structure using MD simulations. The influence of different cure reactions and extent of curing are analyzed on the several thermo-mechanical properties such as mass density, glass transition temperature, coefficient of thermal expansion, elastic moduli, and thermal conductivity. The developed crosslinked models correctly predict experimentally observed trends for various properties. Finally, the epoxies modeled (di-, tri-, and tetra-functionalresins) are simulated with embedded CNT to understand how the affinity to nanoparticles affects the mechanical response. Multiscale modeling techniques are then employed to translate the molecular phenomena observed to predict the behavior of realistic composites. The effective stiffness of hybrid composites are predicted for CNT/epoxy composites with randomly oriented CNTs, for CF/CNT/epoxy systems with aligned CFs and randomly oriented CNTs, and for woven CF/CNT/epoxy fabric with randomly oriented CNTs. The results indicate that in the CNT/epoxy systems the epoxy type has a significant influence on the elastic properties. For the CF/CNT/epoxy hybrid composites, the axial modulus is highly influenced by CF concentration, while the transverse modulus is primarily affected by the CNT weight fraction.

Design of intelligent composites with life-cycle health management capabilities

NASA Astrophysics Data System (ADS)

Rosania, Colleen L.; Larrosa, Cecilia C.; Chang, Fu-Kuo

2015-03-01

Use of carbon fiber reinforced polymers (CFRPs) presents challenges because of their complex manufacturing processes and different damage mechanics in relation to legacy metal materials. New monitoring methods for manufacturing, quality verification, damage estimation, and prognosis are needed to use CFRPs safely and efficiently. This work evaluates the development of intelligent composite materials using integrated piezoelectric sensors to monitor the material during cure and throughout service life. These sensors are used to propagate ultrasonic waves through the structure for health monitoring. During manufacturing, data is collected at different stages during the cure cycle, detecting the changing material properties during cure and verifying quality and degree of cure. The same sensors can then be used with previously developed techniques to perform damage detection, such as impact detection and matrix crack density estimation. Real-time damage estimation can be combined with prognostic models to predict future propagation of damage in the material. In this work experimental results will be presented from composite coupons with embedded piezoelectric sensors. Cure monitoring and damage detection results derived from analysis of the ultrasonic sensor signal will be shown. Sensitive signal parameters to the different stimuli in both the time and frequency domains will be explored for this analysis. From these results, use of the same sensor networks from manufacturing throughout the life of the composite material will demonstrate the full life-cycle monitoring capability of these intelligent materials.

Light curing in orthodontics; should we be concerned?

PubMed

McCusker, Neil; Lee, Siu Man; Robinson, Stephen; Patel, Naresh; Sandy, Jonathan R; Ireland, Anthony J

2013-06-01

Light cured materials are increasingly used in orthodontic clinical practice and concurrent with developments in materials have been developments in light curing unit technology. In recent years the irradiances of these units have increased. The aim of this study was to determine the safe exposure times to both direct and reflected light. The weighted irradiance and safe exposure times of 11 dental curing lights (1 plasma arc, 2 halogen and 8 LED lights) were determined at 6 distances (2-60 cm) from the light guide tip using a spectroradiometer. In addition, using the single most powerful light, the same two parameters were determined for reflected light. This was done at a distance of 10 cm from the reflected light, but during simulated bonding of 8 different orthodontic brackets of three material types, namely stainless steel, ceramic and composite. The results indicate that the LED Fusion lamp had the highest weighted irradiance and the shortest safe exposure time. With this light the maximum safe exposure time without additional eye protection for the patient (at 10 cm), the operator (at 30 cm) and the assistant (at 60 cm) ranged from 2.5 min, 22.1 min and 88.8 min respectively. This indicates a relatively low short term risk during normal operation of dental curing lights. For reflected light at a distance of 10 cm the risk was even lower, but was affected by the material and shape of the orthodontic bracket under test. The short term risks associated with the use of dental curing lights, halogen, LED or plasma, appear to be low, particularly if as is the case adequate safety precautions are employed. The same is true for reflected light from orthodontic brackets during bonding. What is still unclear is the potential long term ocular effects of prolonged exposure to the blue light generated from dental curing lights. Copyright © 2013 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Solid freeform fabrication of biomaterials

NASA Astrophysics Data System (ADS)

Chu, Tien-Min Gabriel

1999-12-01

The biological performance of porous Hydroxyapatite (HA) is closely related to the pore architecture in the implants. The study on the effect of architecture to the biological performance of porous HA requires new manufacturing methods that can fabricate implants with controlled pores channels. In this thesis, four highly loaded HA and alumina suspensions were formulated and three different processes involving Solid Freeform Fabrication (SFF) were developed. An aqueous HA suspension in acrylamides was first formulated and the UV-curing properties were evaluated. With a medical grade HA powder, two non-aqueous HA suspensions were formulated: a 40 vol.% HA suspension in Hexanediol Diacrylate (HDDA) and a 40 vol.% HA suspension in 1:1 mix of Propoxylated Neopentyl Glycol Diacrylate (PNPGDA) and Isobomyl Acrylate (EBA). A 50 vol.% Alumina suspension in PNPGDA/IBA was also formulated. The effect of dispersant to the viscosity of the suspensions was characterized. In the Stereolithography (SL) method, the curing parameters of HA/HDDA and HA/PNPGDA/IBA were determined. Prototype HA implants with 1,700 mum internal channels were built directly on an SL Apparatus (SLA). The designed internal channel patterns were preserved after sintering. In the Ink-jet printing method, the high temperature flow behaviors of the suspensions were characterized. The effects of solids loading to the viscosity of the suspensions were modeled with Krieger-Dougherty equation. Leveling theory developed in paint industry was employed to analyze the self-leveling capability of the suspensions. In the indirect SL method, the thermal curing behavior of HA and alumina suspensions were characterized. The total cure time was measured and the curing kinetics was modeled. Negative molds for the implants were designed and built on SLA with epoxy resin. HA/PNPGDA/IBA was cast into the mold and cured in an oven. The binders and the epoxy mold were pyrolyzed and the green bodies sintered. Internal channels with sizes in the range of 420 to 968 gm with standard deviation less than 50 mum were successfully built. The formulation and characterization techniques developed in this thesis were useful for evaluating the suspensions for SFF process. The manufacturing process developed in this thesis have provided new methods for controlling the channel size in porous HA implants.

A brief history of LED photopolymerization.

PubMed

Jandt, Klaus D; Mills, Robin W

2013-06-01

The majority of modern resin-based oral restorative biomaterials are cured via photopolymerization processes. A variety of light sources are available for this light curing of dental materials, such as composites or fissure sealants. Quartz-tungsten-halogen (QTH) light curing units (LCUs) have dominated light curing of dental materials for decades and are now almost entirely replaced by modern light emitting diode light curing units (LED LCUs). Exactly 50 years ago, visible LEDs were invented. Nevertheless, it was not before the 1990s that LEDs were seriously considered by scientists or manufactures of commercial LCUs as light sources to photopolymerize dental composites and other dental materials. The objective of this review paper is to give an overview of the scientific development and state-of-the-art of LED photopolymerization of oral biomaterials. The materials science of LED LCU devices and dental materials photopolymerized with LED LCU, as well as advantages and limits of LED photopolymerization of oral biomaterials, are discussed. This is mainly based on a review of the most frequently cited scientific papers in international peer reviewed journals. The developments of commercial LED LCUs as well as aspects of their clinical use are considered in this review. The development of LED LCUs has progressed in steps and was made possible by (i) the invention of visible light emitting diodes 50 years ago; (ii) the introduction of high brightness blue light emitting GaN LEDs in 1994; and (iii) the creation of the first blue LED LCUs for the photopolymerization of oral biomaterials. The proof of concept of LED LCUs had to be demonstrated by the satisfactory performance of resin based restorative dental materials photopolymerized by these devices, before LED photopolymerization was generally accepted. Hallmarks of LED LCUs include a unique light emission spectrum, high curing efficiency, long life, low energy consumption and compact device form factor. By understanding the physical principles of LEDs, the development of LED LCUs, their strengths and limitations and the specific benefits of LED photopolymerization will be better appreciated. Copyright © 2013 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Heat transfer properties and thermal cure of glass-ionomer dental cements.

PubMed

Gavic, Lidia; Gorseta, Kristina; Glavina, Domagoj; Czarnecka, Beata; Nicholson, John W

2015-10-01

Under clinical conditions, conventional glass-ionomer dental cements can be cured by application of heat from dental cure lamps, which causes acceleration in the setting. In order for this to be successful, such heat must be able to spread sufficiently through the cement to enhance cure, but not transmit heat so effectively that the underlying dental pulp of the tooth is damaged. The current study was aimed at measuring heat transfer properties of modern restorative glass-ionomers to determine the extent to which they meet these twin requirements. Three commercial glass ionomer cements (Ionofil Molar, Ketac Molar and Equia™ Fill) were used in association with three different light emitting diode cure lamps designed for clinical use. In addition, for each cement, one set of specimens was allowed to cure without application of a lamp. Temperature changes were measured at three different depths (2, 3 and 4 mm) after cure times of 20, 40 and 60 s. The difference among the tested groups was evaluated by ANOVA (P < 0.05) and post hoc Newman-Keuls test. All brands of glass-ionomer showed a small inherent setting exotherm in the absence of heat irradiation, but much greater temperature increases when exposed to the cure lamp. However, temperature rises did not exceed 12.9 °C. Application of the cure lamp led to the establishment of a temperature gradient throughout each specimen. Differences were typically significant (P < 0.05) and did not reflect the nominal power of the lamps, because those lamps have variable cooling systems, and are designed to optimize light output, not heating effect. Because the thermal conductivity of glass-ionomers is low, temperature rises at 4 mm depths were much lower than at 2 mm. At no time did the temperature rise sufficiently to cause concern about potential damage to the pulp.

Recent developments in the effort to cure HIV infection: going beyond N = 1.

PubMed

Siliciano, Janet D; Siliciano, Robert F

2016-02-01

Combination antiretroviral therapy (ART) can suppress plasma HIV to undetectable levels, allowing HIV-infected individuals who are treated early a nearly normal life span. Despite the clear ability of ART to prevent morbidity and mortality, it is not curative. Even in individuals who have full suppression of viral replication on ART, there are resting memory CD4+ T cells that harbor stably integrated HIV genomes, which are capable of producing infectious virus upon T cell activation. This latent viral reservoir is considered the primary obstacle to the development of an HIV cure, and recent efforts in multiple areas of HIV research have been brought to bear on the development of strategies to eradicate or develop a functional cure for HIV. Reviews in this series detail progress in our understanding of the molecular and cellular mechanisms of viral latency, efforts to accurately assess the size and composition of the latent reservoir, the characterization and development of HIV-targeted broadly neutralizing antibodies and cytolytic T lymphocytes, and animal models for the study HIV latency and therapeutic strategies.

The cure: design and evaluation of a crowdsourcing game for gene selection for breast cancer survival prediction.

PubMed

Good, Benjamin M; Loguercio, Salvatore; Griffith, Obi L; Nanis, Max; Wu, Chunlei; Su, Andrew I

2014-07-29

Molecular signatures for predicting breast cancer prognosis could greatly improve care through personalization of treatment. Computational analyses of genome-wide expression datasets have identified such signatures, but these signatures leave much to be desired in terms of accuracy, reproducibility, and biological interpretability. Methods that take advantage of structured prior knowledge (eg, protein interaction networks) show promise in helping to define better signatures, but most knowledge remains unstructured. Crowdsourcing via scientific discovery games is an emerging methodology that has the potential to tap into human intelligence at scales and in modes unheard of before. The main objective of this study was to test the hypothesis that knowledge linking expression patterns of specific genes to breast cancer outcomes could be captured from players of an open, Web-based game. We envisioned capturing knowledge both from the player's prior experience and from their ability to interpret text related to candidate genes presented to them in the context of the game. We developed and evaluated an online game called The Cure that captured information from players regarding genes for use as predictors of breast cancer survival. Information gathered from game play was aggregated using a voting approach, and used to create rankings of genes. The top genes from these rankings were evaluated using annotation enrichment analysis, comparison to prior predictor gene sets, and by using them to train and test machine learning systems for predicting 10 year survival. Between its launch in September 2012 and September 2013, The Cure attracted more than 1000 registered players, who collectively played nearly 10,000 games. Gene sets assembled through aggregation of the collected data showed significant enrichment for genes known to be related to key concepts such as cancer, disease progression, and recurrence. In terms of the predictive accuracy of models trained using this information, these gene sets provided comparable performance to gene sets generated using other methods, including those used in commercial tests. The Cure is available on the Internet. The principal contribution of this work is to show that crowdsourcing games can be developed as a means to address problems involving domain knowledge. While most prior work on scientific discovery games and crowdsourcing in general takes as a premise that contributors have little or no expertise, here we demonstrated a crowdsourcing system that succeeded in capturing expert knowledge.

Defining cure.

PubMed

Hilton, Paul; Robinson, Dudley

2011-06-01

This paper is a summary of the presentations made as Proposal 2-"Defining cure" to the 2nd Annual meeting of the ICI-Research Society, in Bristol, 16th June 2010. It reviews definitions of 'cure' and 'outcome', and considers the impact that varying definition may have on prevalence studies and cure rates. The difference between subjective and objective outcomes is considered, and the significance that these different outcomes may have for different stakeholders (e.g. clinicians, patients, carers, industry etc.) is discussed. The development of patient reported outcome measures and patient defined goals is reviewed, and consideration given to the use of composite end-points. A series of proposals are made by authors and discussants as to how currently validated outcomes should be applied, and where our future research activity in this area might be directed. Copyright © 2011 Wiley-Liss, Inc.

Interpenetrating polymer networks from acetylene terminated materials

NASA Technical Reports Server (NTRS)

Connell, J. W.; Hergenrother, P. M.

1989-01-01

As part of a program to develop high temperature/high performance structural resins for aerospace applications, the chemistry and properties of a novel class of interpenetrating polymer networks (IPNs) were investigated. These IPNs consist of a simple diacetylenic compound (aspartimide) blended with an acetylene terminated arylene ether oligomer. Various compositional blends were prepared and thermally cured to evaluate the effect of crosslink density on resin properties. The cured IPNs exhibited glass transition temperatures ranging from 197 to 254 C depending upon the composition and cure temperature. The solvent resistance, fracture toughness and coefficient of thermal expansion of the cured blends were related to the crosslink density. Isothermal aging of neat resin moldings, adhesive and composite specimens showed a postcure effect which resulted in improved elevated temperature properties. The chemistry, physical and mechanical properties of these materials will be discussed.

Computational methods for yeast prion curing curves.

PubMed

Ridout, Martin S

2008-10-01

If the chemical guanidine hydrochloride is added to a dividing culture of yeast cells in which some of the protein Sup35p is in its prion form, the proportion of cells that carry replicating units of the prion, termed propagons, decreases gradually over time. Stochastic models to describe this process of 'curing' have been developed in earlier work. The present paper investigates the use of numerical methods of Laplace transform inversion to calculate curing curves and contrasts this with an alternative, more direct, approach that involves numerical integration. Transform inversion is found to provide a much more efficient computational approach that allows different models to be investigated with minimal programming effort. The method is used to investigate the robustness of the curing curve to changes in the assumed distribution of cell generation times. Matlab code is available for carrying out the calculations.

Process simulations for manufacturing of thick composites

NASA Astrophysics Data System (ADS)

Kempner, Evan A.

The availability of manufacturing simulations for composites can significantly reduce the costs associated with process development. Simulations provide a tool for evaluating the effect of processing conditions on the quality of parts produced without requiring numerous experiments. This is especially significant in parts that have troublesome features such as large thickness. The development of simulations for thick walled composites has been approached by examining the mechanics of resin flow and fiber deformation during processing, applying these evaluations to develop simulations, and evaluating the simulation with experimental results. A unified analysis is developed to describe the three-dimensional resin flow and fiber preform deformation during processing regardless of the manufacturing process used. It is shown how the generic governing evaluations in the unified analysis can be applied to autoclave molding, compression molding, pultrusion, filament winding, and resin transfer molding. A comparison is provided with earlier models derived individually for these processes. The evaluations described for autoclave curing were used to produce a one-dimensional cure simulation for autoclave curing of thick composites. The simulation consists of an analysis for heat transfer and resin flow in the composite as well as bleeder plies used to absorb resin removed from the part. Experiments were performed in a hot press to approximate curing in an autoclave. Graphite/epoxy laminates of 3 cm and 5 cm thickness were cured while monitoring temperatures at several points inside the laminate and thickness. The simulation predicted temperatures fairly closely, but difficulties were encountered in correlation of thickness results. This simulation was also used to study the effects of prepreg aging on processing of thick composites. An investigation was also performed on filament winding with prepreg tow. Cylinders were wound of approximately 12 mm thickness with pressure gages at the mandrel-composite interface. Cylinders were hoop wound with tensions ranging from 13-34 N. An analytical model was developed to calculate change in stress due to relaxation during winding. Although compressive circumferential stresses occurred throughout each of the cylinders, the magnitude was fairly low.

Purinergic system in psychiatric diseases.

PubMed

Cheffer, A; Castillo, A R G; Corrêa-Velloso, J; Gonçalves, M C B; Naaldijk, Y; Nascimento, I C; Burnstock, G; Ulrich, H

2018-01-01

Psychiatric disorders are debilitating diseases, affecting >80 million people worldwide. There are no causal cures for psychiatric disorders and available therapies only treat the symptoms. The etiology of psychiatric disorders is unknown, although it has been speculated to be a combination of environmental, stress and genetic factors. One of the neurotransmitter systems implicated in the biology of psychiatric disorders is the purinergic system. In this review, we performed a comprehensive search of the literature about the role and function of the purinergic system in the development and predisposition to psychiatric disorders, with a focus on depression, schizophrenia, bipolar disorder, autism, anxiety and attention deficit/hyperactivity disorder. We also describe how therapeutics used for psychiatric disorders act on the purinergic system.

Effect of CNT addition on cure kinetics of glass fiber/epoxy composite

NASA Astrophysics Data System (ADS)

Fulmali, A. O.; Kattaguri, R.; Mahato, K. K.; Prusty, R. K.; Ray, B. C.

2018-03-01

In present time, developments in reinforced polymer composites have acquired preferential attention for high performance and high precision applications like aerospace, marine and transportation. Fibre reinforced polymer (FRP) composites are being substituted because of their low density, higher strength, stiffness, impact resistance, and improved corrosion resistance. Further laminated composites exhibit superior in-plane mechanical properties that are mostly governed by the fibers. However, laminated FRP composites suffer from poor out of plane properties in some applications. These properties can further be improved by the addition of Nano fillers like carbon nanotube (CNT), graphene and so on. Curing cycle plays a very important role in drawing out the optimum property of glass fiber/epoxy (GE) composite. It is expected that the cure kinetics can further be altered by addition of CNT due to its higher aspect ratio. The main objective of this work is to study the effect of CNT addition on cure kinetics of GE composite as multi-segment adsorption of polymer takes place on the CNT surface. In this study effects of curing parameters on mechanical properties and glass transition temperature of CNT embedded glass fiber/epoxy composite (CNT-GE) has been evaluated. For this study control GE and CNT-GE (with 0.1 wt. %) laminates were fabricated using hand lay-up technique followed by hot compression. The curing parameters that were considered in the present investigation were temperature (80°C, 110°C, and 140°C) and time (0.5 hr, 3 hr and 6 hr). For different combination of above mentioned temperature and time, samples of GE and CNT-GE composites were post cured. Mechanical properties were determined by flexural testing using 3 point bending fixture on INSTRON-5967 and thermal properties i.e. glass transition temperature (Tg) determined by Differential Scanning Calorimeter (DSC) to evaluate the effects of curing parameters. For CNT-GE samples, No much variation observed in flexural modulus with increase in post curing temperature and time, but swift increment was observed in flexural strength at 140°C with increase in post cure time. Elevation in Tg observed with increase in temperature and time duration of post curing; highest Tg noted at 140°C-6hr. Optimum post curing parameters for CNT-GE composite observed to be 140°C-6hr.

Cure Monitoring Techniques for Adhesive Bonding Techniques.

DTIC Science & Technology

1980-11-01

l TABLE OF CONTIW Section Pase I INTRODUCTION 1. Program Overviev 1 2. Smary 2 II MONITORING SYSTEM IMPROVEMENTS 3 1. Development of a...encountered in the electronics/signal/ computer interfaces, although solvable, have slowed progress and starting a bondline monitoring program to do a...AIWAL/MLBC) as Project Engineer. The program manager is Mr. C. A. May. The principal investigator is Dr. A. Wereta, Jr., assisted by Mass. W. G. Caple, J

Formaldehyde emission and high-temperature stability of cured urea-formaldehyde resins

Treesearch

Shin-ichiro Tohmura; Chung-Yun Hse; Mitsuo Higuchi

2000-01-01

A test method for measuring formaldehyde from urea-formaldehyde (UF) resins at high temperature was developed and used to assess the influence of the reaction pH on the formaldehyde emission and heat stability of the cured resins. Additionally, solid-state 13C CP/MAS nuclear magnetic resonance (NMR) techniques were used to investigate the...

Barrier layers against oxygen transmission on the basis of electron beam cured methacrylated gelatin

NASA Astrophysics Data System (ADS)

Scherzer, Tom

1997-08-01

The development of barrier layers against oxygen transmission on the basis of radiation-curable methacrylated gelatin will be reported. The electron beam cured gelatin coatings show an extremely low oxygen permeability and a high resistance against boiling water. Moreover, the methacrylated gelatins possess good adhesion characteristics. Therefore, they are suited as barrier adhesives in laminates for food packaging applications. If substrate foils from biodegradable polymers are used, the development of completely biodegradable packaging materials seems to be possible.

Genomics and cure: understanding narratives of patients with Duchenne muscular dystrophy in Japan.

PubMed

Kato, Masae

2018-04-01

Globally, genomics research is expected to enhance the health of patients with intractable diseases such as Duchenne muscular dystrophy (DMD). But how do patients perceive medical and scientific attempts at creating drugs and finding cure, and why? Since the 1990s, a number of clinical trials for patients of DMD have been organized. Among them are a gene therapy and exon skipping, and they indicate the possibility of finding therapies for DMD patients. Since 2011, Japanese medical institutions have been participating in Global Clinical Trials so that Japanese DMD patients can have access to them once developed. Despite ongoing global clinical trials, however, field research shows that the DMD patients the author encountered were neither enthusiastic nor well informed about gene therapies developed in Japan or elsewhere. Why not? The author observed that the desire for a cure among DMD patients is not self-evident, but is framed by sociocultural conditions surrounding the patients, the local history of discrimination against genetic disorders, and the way care is organised. These factors further interplay with physical and mental conditions particular to DMD, affecting patients' desire for a cure. This paper discusses the perception of genomics research and the possibility of a cure of DMD patients the author encountered in Japan, indicating that such perceptions are a result of the deeply-related interactions of the conditions in which patients live. Finally, the author suggests how commonly held views of patients and patients' desire for cure need to be nuanced in genomic medicine. Data in this paper were collected between April and July 2014, and between 1996 and 2005 in Japan.

Underlying Mechanisms of Tinnitus: Review and Clinical Implications

PubMed Central

Henry, James A.; Roberts, Larry E.; Caspary, Donald M.; Theodoroff, Sarah M.; Salvi, Richard J.

2016-01-01

Background The study of tinnitus mechanisms has increased tenfold in the last decade. The common denominator for all of these studies is the goal of elucidating the underlying neural mechanisms of tinnitus with the ultimate purpose of finding a cure. While these basic science findings may not be immediately applicable to the clinician who works directly with patients to assist them in managing their reactions to tinnitus, a clear understanding of these findings is needed to develop the most effective procedures for alleviating tinnitus. Purpose The goal of this review is to provide audiologists and other health-care professionals with a basic understanding of the neurophysiological changes in the auditory system likely to be responsible for tinnitus. Results It is increasingly clear that tinnitus is a pathology involving neuroplastic changes in central auditory structures that take place when the brain is deprived of its normal input by pathology in the cochlea. Cochlear pathology is not always expressed in the audiogram but may be detected by more sensitive measures. Neural changes can occur at the level of synapses between inner hair cells and the auditory nerve and within multiple levels of the central auditory pathway. Long-term maintenance of tinnitus is likely a function of a complex network of structures involving central auditory and nonauditory systems. Conclusions Patients often have expectations that a treatment exists to cure their tinnitus. They should be made aware that research is increasing to discover such a cure and that their reactions to tinnitus can be mitigated through the use of evidence-based behavioral interventions. PMID:24622858

Prepreg cure monitoring using diffuse reflectance-FTIR. [Fourier Transform Infrared Technique

NASA Technical Reports Server (NTRS)

Young, P. R.; Chang, A. C.

1984-01-01

An in situ diffuse reflectance-Fourier transform infrared technique was developed to determine infrared spectra of graphite fiber prepregs as they were being cured. A bismaleimide, an epoxy, and addition polyimide matrix resin prepregs were studied. An experimental polyimide adhesive was also examined. Samples were positioned on a small heater at the focal point of diffuse reflectance optics and programmed at 15 F/min while FTIR spectra were being scanned, averaged, and stored. An analysis of the resulting spectra provided basic insights into changes in matrix resin molecular structure which accompanied reactions such as imidization and crosslinking. An endo-exothermal isomerization involving reactive end-caps was confirmed for the addition polyimide prepregs. The results of this study contribute to a fundamental understanding of the processing of composites and adhesives. Such understanding will promote the development of more efficient cure cycles.

Simultaneous acoustic and dielectric real time curing monitoring of epoxy systems

NASA Astrophysics Data System (ADS)

Gkikas, G.; Saganas, Ch.; Grammatikos, S. A.; Aggelis, D. G.; Paipetis, A. S.

2012-04-01

The attainment of structural integrity of the reinforcing matrix in composite materials is of primary importance for the final properties of the composite structure. The detailed monitoring of the curing process on the other hand is paramount (i) in defining the optimal conditions for the impregnation of the reinforcement by the matrix (ii) in limiting the effects of the exotherm produced by the polymerization reaction which create unwanted thermal stresses and (iii) in securing optimal behavior in matrix controlled properties, such as off axis or shear properties and in general the durability of the composite. Dielectric curing monitoring is a well known technique for distinguishing between the different stages of the polymerization of a typical epoxy system. The technique successfully predicts the gelation and the vitrification of the epoxy and has been extended for the monitoring of prepregs. Recent work has shown that distinct changes in the properties of the propagated sound in the epoxy which undergoes polymerization is as well directly related to the gelation and vitrification of the resin, as well as to the attainment of the final properties of the resin system. In this work, a typical epoxy is simultaneously monitored using acoustic and dielectric methods. The system is isothermally cured in an oven to avoid effects from the polymerization exotherm. Typical broadband sensors are employed for the acoustic monitoring, while flat interdigital sensors are employed for the dielectric scans. All stages of the polymerization process were successfully monitored and the validity of both methods was cross checked and verified.

Relationship between ecophysiological factors, growth and ochratoxin A contamination of dry-cured sausage based matrices.

PubMed

Rodríguez, Alicia; Capela, Daniela; Medina, Ángel; Córdoba, Juan J; Magan, Naresh

2015-02-02

Dry-cured sausages are colonised by moulds during the ripening process. The temperature and the salt content (which affects water activity, aw) predispose the surface to colonisation by Penicillium species, including Penicillium nordicum and Penicillium verrucosum which can lead to contamination of the sausages with ochratoxin A (OTA). The objective of this work was to obtain scientific data on the impact that interaction between ionic water stress (aw; 0.97, 0.94, 0.90, 0.87 and 0.84) and temperature (30, 25, 20, 15 and 10°C) may have on lag phases prior to growth, growth and OTA production by some P. verrucosum and P. nordicum strains isolated from dry-cured meat products on a dry-cured sausage-based medium over a period of 12days. Although P. nordicum had shorter lag phases than P. verrucosum, the latter grew faster than P. nordicum in most conditions tested. For both species, there was no growth and OTA production at 0.84 aw at all the temperatures tested. The fungi were more tolerant at moderate ionic aw conditions (0.94 and 0.90) and 20 and 25°C. In contrast, the patterns of production of OTA were very different from those for growth. Different OTA production profiles between the two OTA-producing species were found. While P. nordicum began producing OTA in most of the conditions tested by day 6, P. verrucosum only produced the toxin in these conditions when the temperature and aw were >10°C and >0.90, respectively. However, the P. verrucosum strain produced much higher concentrations of OTA than the P. nordicum strain in all conditions. We developed contour maps of the optimum and marginal aw×temperature conditions for growth/OTA production on dry-cured sausage-based medium for the first time. This suggests that these interacting conditions during the early phases of production must be effectively controlled as these favour growth of the toxigenic Penicillia. Knowledge on the ecophysiology of these two important Penicillium species on these matrices could help to make appropriate technological modifications during the sausage ripening process. Thus, our findings may help in informed decision-making in relation to temperature and salt additions at the beginning of processing/curing. Such changes may favour colonisation of starter cultures over OTA producing Penicillia and minimise OTA contamination risks in dry-cured sausages. This may be then effectively incorporated into the hygienic production system in the framework of HACCP. Copyright © 2014 Elsevier B.V. All rights reserved.

Sodium nitrite: the "cure" for nitric oxide insufficiency.

PubMed

Parthasarathy, Deepa K; Bryan, Nathan S

2012-11-01

This process of "curing" food is a long practice that dates back thousands of years long before refrigeration or food safety regulations. Today food safety and mass manufacturing are dependent upon safe and effective means to cure and preserve foods including meats. Nitrite remains the most effective curing agent to prevent food spoilage and bacterial contamination. Despite decades of rigorous research on its safety and efficacy as a curing agent, it is still regarded by many as a toxic undesirable food additive. However, research within the biomedical science community has revealed enormous therapeutic benefits of nitrite that is currently being developed as novel therapies for conditions associated with nitric oxide (NO) insufficiency. Much of the same biochemistry that has been understood for decades in the meat industry has been rediscovered in human physiology. This review will highlight the fundamental biochemistry of nitrite in human physiology and highlight the risk benefit evaluation surrounding nitrite in food and meat products. Foods or diets enriched with nitrite can have profound positive health benefits. Copyright © 2012 Elsevier Ltd. All rights reserved.

Measuring UV Curing Parameters of Commercial Photopolymers used in Additive Manufacturing.

PubMed

Bennett, Joe

2017-12-01

A testing methodology was developed to expose photopolymer resins and measure the cured material to determine two key parameters related to the photopolymerization process: E c (critical energy to initiate polymerization) and D p (penetration depth of curing light). Five commercially available resins were evaluated under exposure from 365 nm and 405 nm light at varying power densities and energies. Three different methods for determining the thickness of the cured resin were evaluated. Caliper measurements, stylus profilometry, and confocal laser scanning microscopy showed similar results for hard materials while caliper measurement of a soft, elastomeric material proved inaccurate. Working curves for the five photopolymers showed unique behavior both within and among the resins as a function of curing light wavelength. E c and D p for the five resins showed variations as large as 10×. Variations of this magnitude, if unknown to the user and not controlled for, will clearly affect printed part quality. This points to the need for a standardized approach for determining and disseminating these, and perhaps, other key parameters.

Electronic nose for the identification of pig feeding and ripening time in Iberian hams.

PubMed

Santos, J P; García, M; Aleixandre, M; Horrillo, M C; Gutiérrez, J; Sayago, I; Fernández, M J; Arés, L

2004-03-01

An electronic nose system to control the processing of dry-cured Iberian ham is presented. The sensors involved are tin oxide semiconductors thin films. They were prepared by RF sputtering. Some of the sensors were doped with metal catalysts as Pt and Pd, in order to improve the selectivity of the sensors. The multisensor with 16 semiconductor sensors, gave different responses from two types of dry-cured Iberian hams which differ in the feeding and curing time. The data has been analysed using the PCA (principal component analysis) and backpropagation and probabilistic neural networks. The analysis shows that different types of Iberian ham can be discriminated and identified successfully.

Influence of etching time and bonding strategies on the microshear bond strength of self- and light-cured pit-and-fissure sealants.

PubMed

Souza-Junior, Eduardo José; Borges, Boniek Castillo Dutra; Montes, Marcos Antônio Japiassú Resende; Alonso, Roberta Caroline Bruschi; Ambrosano, Glaucia Maria Bovi; Sinhoreti, Mário Alexandre Coelho

2012-01-01

This study evaluated the impact of extended etching and bonding strategies on the microshear bond strength of three sealant materials. Two pit-and-fissure sealants [FluroShield, Dentsply (light-cured) and AlphaSeal, DFL (self-cured)] and one light-cured flowable composite resin (Permaflo, Ultradent) were evaluated according to different enamel etching times (15 s or 30 s) and bonding procedures (no adhesive application, application of primer/hydrophobic resin or hydrophobic resin only). Intact enamel blocks were obtained from bovine teeth and sealed via the tested protocols. After 24 h, the microshear bond strength test was performed in a universal testing machine at a crosshead speed of 0.5 mm/min. Failure modes were classified by stereomicroscopy. Data were submitted to a three-way ANOVA and to Tukey's test (α=0.05). There was no statistically significant difference (p>0.05) among the materials. Permaflo showed higher bond strength when etched for 30 s alone. Enamel overetching decreased the bond strength of the light-cured sealant. Primer/bond previous treatment improved bond performance for AlphaSeal. In conclusion, from the tested conditions, all sealant materials presented similar bond strength values in relation to bonding protocol and etching time. The flowable composite can be used as a pit-and-fissure sealant. The use of a three-step adhesive system was essential for the self-cured sealant application.

Synthesis and cure mechanism characterization of phenylethynyl-terminated imide oligomers

NASA Astrophysics Data System (ADS)

Back, Susanna Branion

Polymer matrix composites (PMC) are being investigated by the Air Force for use in engine applications, which are comprised of an intermediate carbon fiber-reinforced high temperature phenylethynyl-terminated fluorinated polyimide resin. The high-temperature phenylethynyl-terminated fluorinated polyimide resin is prepared from 4-(phenylethynyl)phthalic anhydride (4-PEPA), p-phenylenediamine (p-PDA), and hexafluoroisopropylidene bisphthalic dianhydride (6FDA). In order for these materials to be exploited to their full potential, many fundamental aspects of the polymer system need to be better understood. For this study, the high-temperature cure mechanism, the chemical structures of cure reaction products, and the effect of physical properties of impurities in the 4-PEPA monomer were investigated. A phenylethynyl-terminated imide model compound, N-(3-phenoxybenzene)-4-phenylethynylphthalimide (N-PBPEP), was prepared using both industrial 4-PEPA and recrystallized 4-PEPA. The thermal cure of this low molecular weight compound was studied using a variety of analytical techniques including differential scanning calorimetry, Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance spectroscopy (NMR), and mass spectrometry (MS). N-PBPEP made from industrial 4-PEPA begins curing 25°C later than N-PBPEP made from recrystallized 4-PEPA, indicating that thermal cure is affected by the purity of the 4-PEPA starting material. Also, both versions form an 830 g/mol dimer with three possible mechanistic pathways.

Studies on Various Functional Properties of Titania Thin Film Developed on Glazed Ceramic Wall Tiles

NASA Astrophysics Data System (ADS)

Anil, Asha; Darshana R, Bangoria; Misra, S. N.

A sol-gel based TiO2 thin film was applied on glazed wall tiles for studying its various functional properties. Thin film was deposited by spin coating on the substrate and subjected to curing at different temperatures such as 600°C, 650, 700°C, 750°C and 800°C with 10 minutes soaking. The gel powder was characterized by FTIR, DTA/TG and XRD. Microstructure of thin film was analyzed by FESEM and EDX. Surface properties of the coatings such as gloss, colour difference, stain resistance, mineral hardness and wettability were extensively studied. The antibacterial activity of the surface of coated substrate against E. coli was also examined. The durability of the coated substrate in comparison to the uncoated was tested against alkali in accordance with ISO: 10545 (Part 13):1995 standard. FESEM images showed that thin films are dense and homogeneous. Coated substrates after firing results in lustre with high gloss, which increased from 330 to 420 GU as the curing temperature increases compared to that of uncoated one (72 GU). Coated substrate cured at 800°C shows higher mineral hardness (5 Mohs’) compared to uncoated one (4 Mohs’) and films cured at all temperatures showed stain resistance. The experimental results showed that the resistance towards alkali attack increase with increase in curing temperature and alkali resistance of sample cured at 800 °C was found to be superior compared to uncoated substrate. Contact angle of water on coated surface of substrates decreased with increase in temperature. Bacterial reduction percentages of the coated surface was 97% for sample cured at 700°C and it decreased from 97% to 87% as the curing temperature increased to 800 °C when treated with E. coli bacteria.

Effect of Molarity of Sodium Hydroxide and Curing Method on the Compressive Strength of Ternary Blend Geopolymer Concrete

NASA Astrophysics Data System (ADS)

Sathish Kumar, V.; Ganesan, N.; Indira, P. V.

2017-07-01

Concrete plays a vital role in the development of infrastructure and buildings all over the world. Geopolymer based cement-less concrete is one of the current findings in the construction industry which leads to a green environment. This research paper deals with the results of the use of Fly ash (FA), Ground Granulated Blast Furnace Slag (GGBS) and Metakaolin (MK) as a ternary blend source material in Geopolymer concrete (GPC). The aspects that govern the compressive strength of GPC like the proportion of source material, Molarity of Sodium Hydroxide (NaOH) and Curing methods were investigated. The purpose of this research is to optimise the local waste material and use them effectively as a ternary blend in GPC. Seven combinations of binder were made in this study with replacement of FA with GGBS and MK by 35%, 30%, 25%, 20%, 15%, 10%, 5% and 5%, 10%, 15%, 20%, 25%, 30%, 35% respectively. The molarity of NaOH solution was varied by 12M, 14M and 16M and two types of curing method were adopted, viz. Hot air oven curing and closed steam curing for 24 hours at 60°C (140°F). The samples were kept at ambient temperature till testing. The compressive strength was obtained after 7 days and 28 days for the GPC cubes. The test data reveals that the ternary blend GPC with molarity 14M cured by hot air oven produces the maximum compressive strength. It was also observed that the compressive strength of the oven cured GPC is approximately 10% higher than the steam cured GPC using the ternary blend.

The effect of filler content and processing variables on dimensional accuracy of experimental composite inlay material.

PubMed

Razak, A A; Harrison, A

1997-04-01

Dimensional accuracy of a composite inlay restoration is important to ensure an accurate fit and to minimize cementation stresses. A method was developed to measure dimensional accuracy and stability of a composite inlay. A standard Class II (MOD) inlay cavity stainless steel mold was made with six circular indentations placed on the occlusal floor of the cavity and four indentations on each gingival floor to act as datum points in the measurement of linear polymerization shrinkage. The inlay restorations were prepared from an inlay-onlay composite material of different filler contents (50%, 65%, and 79% by weight). For each filler content group, three curing methods were used: light curing only, light curing and heat curing at 100 degrees C for 5 minutes, and light curing and heat curing at 100 degrees C for 5 minutes and then storage in distilled water for 7 days. The accuracy of the MOD inlays was determined by measuring the shrinkage of the restoration on the occlusal floor areas and the gingival seats. The results demonstrated an inverse linear relationship between filler content and polymerization shrinkage. There was a tendency for the light-curing and heat-curing method to show an increase in polymerization shrinkage. An expansion was recorded between the mesial and distal boxes when the specimens were soaked in water for 7 days. This study suggested that the inlay mold limits the physical shrinkage that can occur between the mesial and distal axial walls of the inlay restoration because the inlay cannot shrink to a smaller dimension than the mold. Water sorption then causes hygroscopic expansion, which enlarges the distance between the mesial and distal walls.

Dissipation kinetics and effect of processing on imidacloprid and its metabolites in cardamom (Elettaria cardamomum Maton).

PubMed

Pratheeshkumar, N; Chandran, M; Beevi, S Naseema; Mathew, Thomas Biju; George, Thomas; Paul, Ambily; Xavier, George; Ravi, K Prathibha; Kumar, S Visal; Rajith, R

2016-01-01

Dissipation behaviour of the chloronicotinyl insecticide, imidacloprid (Tatamida 17.8 % SL), in fresh and cured cardamom capsules was studied following application at doses 20 and 40 g a.i. ha(-1) in a cardamom plantation of Indian Cardamom Hills (ICH), Idukki, Kerala, India. A single-laboratory ultra performance liquid chromatography mass spectrometry (UPLC-MS/MS) method was developed and validated for the estimation of imidacloprid and its six metabolites (5-hydroxy, olefin, guanidine, urea, 6-chloronicotinic acid and nitrosimine) in fresh and cured cardamom. At the lower dose, the initial deposits of total imidacloprid residues were 1.91 and 7.23 μg g(-1), respectively, in fresh and cured cardamom. At the higher dose, the initial residues were 3.94 and 14.72 μg g(-1), respectively, in fresh and cured capsules. The residues dissipated below the quantitation level of 0.01 μg g(-1) after 21 and 28 days at lower dose and after 28 days for both at higher dose. The half-lives of imidacloprid in fresh and cured cardamom were 4.02 and 3.63 days, respectively, at lower dose and 3.61 days for both at higher dose. The waiting periods of imidacloprid on fresh and cured cardamom at lower and higher doses were 21.40, 27.10, 23.85 and 30.70 days, respectively. The mean processing factor of imidacloprid was 3.96 at 20 g a.i. ha(-1). Amongst metabolites of imidacloprid, urea had maximum residues in fresh and cured cardamom followed by 5-hydroxy and guanidine. Other metabolites such as 6-chloronicotinic acid, olefin and nitrosimine were not detected either in fresh or cured cardamom.

Advantages and drawbacks of Thiol-ene based resins for 3D-printing

NASA Astrophysics Data System (ADS)

Leonards, Holger; Engelhardt, Sascha; Hoffmann, Andreas; Pongratz, Ludwig; Schriever, Sascha; Bläsius, Jana; Wehner, Martin; Gillner, Arnold

2015-03-01

The technology of 3D printing is conquering the world and awakens the interest of many users in the most varying of applications. New formulation approaches for photo-sensitive thiol-ene resins in combination with various printing technologies, like stereolithography (SLA), projection based printing/digital light processing (DLP) or two-photon polymerization (TPP) are presented. Thiol-ene polymerizations are known for its fast and quantitative reaction and to form highly homogeneous polymer networks. As the resins are locally and temporally photo-curable the polymerization type is very promising for 3D-printing. By using suitable wavelengths, photoinitiator-free fabrication is feasible for single- and two photon induced polymerization. In this paper divinyl ethers of polyethylene glycols in combination with star-shaped tetrathiols were used to design a simple test-system for photo-curable thiol-ene resins. In order to control and improve curing depth and lateral resolution in 3D-polymerization processes, either additives in chemical formulation or process parameters can be changed. The achieved curing depth and resolution limits depend on the applied fabrication method. While two-/multiphoton induced lithography offers the possibility of micron- to sub-micron resolution it lacks in built-up speed. Hence single-photon polymerization is a fast alternative with optimization potential in sub-10-micron resolution. Absorber- and initiator free compositions were developed in order to avoid aging, yellowing and toxicity of resulting products. They can be cured with UV-laser radiation below 300 nm. The development at Fraunhofer ILT is focusing on new applications in the field of medical products and implants, technical products with respect to mechanical properties or optical properties of 3D-printed objects. Recent process results with model system (polyethylene glycol divinylether/ Pentaerithrytol tetrakis (3-mercaptopropionat), Raman measurements of polymer conversion and surface modifications using bifunctional crosslinkers are presented with advantages, drawbacks and a general outlook.

Persisting PET-CT lesion activity and M. tuberculosis mRNA after pulmonary tuberculosis cure

PubMed Central

Malherbe, Stephanus T.; Shenai, Shubhada; Ronacher, Katharina; Loxton, Andre G.; Dolganov, Gregory; Kriel, Magdalena; Van, Tran; Chen, Ray Y.; Warwick, James; Via, Laura E.; Song, Taeksun; Lee, Myungsun; Schoolnik, Gary; Tromp, Gerard; Alland, David; Barry, Clifton E.; Winter, Jill; Walzl, Gerhard

2016-01-01

The absence of a gold standard to determine when antibiotics have induced sterilizing cure confounds the development of new approaches to treat pulmonary tuberculosis (PTB). We detected PET-CT imaging response patterns consistent with active disease along with the presence of Mycobacterium tuberculosis mRNA in sputum and bronchoalveolar lavage samples in a substantial proportion of adult, HIV-negative PTB patients after standard 6-month treatment plus one year follow-up, including patients with a durable cure and others who later developed recurrent disease. The presence of MTB mRNA in the context of non-resolving and intensifying lesions on PET-CT might indicate ongoing transcription, suggesting that even apparently curative PTB treatment may not eradicate all organisms in most patients. This suggests an important complementary role for the immune response in maintaining a disease-free state. Sterilizing drugs or host-directed therapies and better treatment response markers are likely needed for the successful development of improved and shortened PTB treatment strategies. PMID:27595324

Solid Rocket Fuel Constitutive Theory and Polymer Cure

NASA Technical Reports Server (NTRS)

Ream, Robert

2006-01-01

Solid Rocket Fuel is a complex composite material for which no general constitutive theory, based on first principles, has been developed. One of the principles such a relation would depend on is the morphology of the binder. A theory of polymer curing is required to determine this morphology. During work on such a theory an algorithm was developed for counting the number of ways a polymer chain could assemble. The methods used to develop and check this algorithm led to an analytic solution to the problem. This solution is used in a probability distribution function which characterizes the morphology of the polymer.

Microwave-Assisted Curing of Silicon Carbide-Reinforced Epoxy Composites: Role of Dielectric Properties

NASA Astrophysics Data System (ADS)

Pal, Ranu; Akhtar, M. J.; Kar, Kamal K.

2018-05-01

In this work, the dielectric properties of epoxy-based composites are significantly improved with the help of the silicon carbide (SiC) filler at an operating frequency of 2.45 GHz to make them ideal candidates for microwave curing. The improvement is due to enhancement of the interfacial polarization because of the presence of the SiC filler. The dielectric properties are measured using the microwave cavity perturbation method. The cavity structure is simulated using the COMSOL@Multiphysics software to verify the measured data in terms of the resonant frequency. Finally, all the SiC-based composites including the neat epoxy resin are heated in the 2.45 GHz microwave oven at 300 W for 20 min. The thermal and mechanical properties of all the cured composites are measured, and the data are compared with their room temperature pre-cured counterparts. The dielectric properties of composite samples using SiC as a reinforcing agent in the epoxy are found to be substantially improved compared with those of the pure epoxy sample, which actually leads to better curing of these composite using the 2.45 GHz microwave system.

Modeling HCV cure after an ultra-short duration of therapy with direct acting agents

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

Goyal, Ashish; Lurie, Yoav; Meissner, Eric G.

In cases of sustained-virological response (SVR or cure) after an ultra-short duration (≤ 27 days) of direct-acting antiviral (DAA)-based therapy, despite HCV being detected at end of treatment (EOT), have been reported. Established HCV mathematical models that predict the treatment duration required to achieve cure do not take into account the possibility that the infectivity of virus produced during treatment might be reduced. The aim of this study was to develop a new mathematical model that considers the fundamental and critical concept that HCV RNA in serum represents both infectious virus (V i) and non-infectious virus (V ni) in ordermore » to explain the observation of cure with ultrashort DAA therapy. Established HCV models were compared to the new mathematical model to retrospectively explain cure in 2 patients who achieved cure after 24 or 27 days of paritaprevir, ombitasvir, dasabuvir, ritonavir and ribavirin or sofosbuvir plus ribavirin, respectively. Fitting established models with measured longitudinal HCV viral loads indicated that in both cases, cure would not have been expected without an additional 3–6 weeks of therapy after the actual EOT. In contrast, the new model fits the observed outcome by considering that in addition to blocking V i and V ni production (ε~0.998), these DAA + ribavirin treatments further enhanced the ratio of V ni to V i, thus increasing the log (V ni/V i) from 1 at pretreatment to 6 by EOT, which led to <1 infectious-virus particle in the extracellular body fluid (i.e., cure) prior to EOT. This new model can explain cure after short duration of DAA + ribavirin therapy by suggesting that a minimum 6-fold increase of log (V ni/V i) results from drug-induced enhancement of the V ni/V i.« less

Modeling HCV cure after an ultra-short duration of therapy with direct acting agents

DOE PAGES

Goyal, Ashish; Lurie, Yoav; Meissner, Eric G.; ...

2017-06-30

In cases of sustained-virological response (SVR or cure) after an ultra-short duration (≤ 27 days) of direct-acting antiviral (DAA)-based therapy, despite HCV being detected at end of treatment (EOT), have been reported. Established HCV mathematical models that predict the treatment duration required to achieve cure do not take into account the possibility that the infectivity of virus produced during treatment might be reduced. The aim of this study was to develop a new mathematical model that considers the fundamental and critical concept that HCV RNA in serum represents both infectious virus (V i) and non-infectious virus (V ni) in ordermore » to explain the observation of cure with ultrashort DAA therapy. Established HCV models were compared to the new mathematical model to retrospectively explain cure in 2 patients who achieved cure after 24 or 27 days of paritaprevir, ombitasvir, dasabuvir, ritonavir and ribavirin or sofosbuvir plus ribavirin, respectively. Fitting established models with measured longitudinal HCV viral loads indicated that in both cases, cure would not have been expected without an additional 3–6 weeks of therapy after the actual EOT. In contrast, the new model fits the observed outcome by considering that in addition to blocking V i and V ni production (ε~0.998), these DAA + ribavirin treatments further enhanced the ratio of V ni to V i, thus increasing the log (V ni/V i) from 1 at pretreatment to 6 by EOT, which led to <1 infectious-virus particle in the extracellular body fluid (i.e., cure) prior to EOT. This new model can explain cure after short duration of DAA + ribavirin therapy by suggesting that a minimum 6-fold increase of log (V ni/V i) results from drug-induced enhancement of the V ni/V i.« less

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

Rao, Rekha R.; Celina, Mathias C.; Giron, Nicholas Henry

We are developing computational models to help understand manufacturing processes, final properties and aging of structural foam, polyurethane PMDI. Th e resulting model predictions of density and cure gradients from the manufacturing process will be used as input to foam heat transfer and mechanical models. BKC 44306 PMDI-10 and BKC 44307 PMDI-18 are the most prevalent foams used in structural parts. Experiments needed to parameterize models of the reaction kinetics and the equations of motion during the foam blowing stages were described for BKC 44306 PMDI-10 in the first of this report series (Mondy et al. 2014). BKC 44307 PMDI-18more » is a new foam that will be used to make relatively dense structural supports via over packing. It uses a different catalyst than those in the BKC 44306 family of foams; hence, we expect that the reaction kineti cs models must be modified. Here we detail the experiments needed to characteriz e the reaction kinetics of BKC 44307 PMDI-18 and suggest parameters for the model based on these experiments. In additi on, the second part of this report describes data taken to provide input to the preliminary nonlinear visco elastic structural response model developed for BKC 44306 PMDI-10 foam. We show that the standard cu re schedule used by KCP does not fully cure the material, and, upon temperature elevation above 150°C, oxidation or decomposition reactions occur that alter the composition of the foam. These findings suggest that achieving a fully cured foam part with this formulation may be not be possible through therma l curing. As such, visco elastic characterization procedures developed for curing thermosets can provide only approximate material properties, since the state of the material continuously evolves during tests.« less

A cure-rate model for the Shuttle filament-wound case

NASA Technical Reports Server (NTRS)

Cagliostro, D. E.; Islas, A.; Hsu, Ming-Ta

1987-01-01

An epoxy and carbon fiber composite has been used to produce a light-weight rocket case for the Space Shuttle. A kinetic model is developed which can predict the extent of epoxy conversion during the winding and curing of the case. The model accounts for both chemical and physical kinetics. In the model, chemical kinetics occur exclusively up to the time the transition temperature equals the reaction temperature. At this point the resin begins to solidify and the rate of this process limits the rate of epoxy conversion. A comparison of predicted and actual epoxy conversion is presented for isothermal and temperature programmed cure schedules.

Unraveling the "known unknowns": lessons and reflections from the new directions in leukemia research 2012 conference.

PubMed

White, Deborah L; Brown, Anna L; D'Andrea, Richard J; Rice, Alison M

2012-09-01

Patients diagnosed with leukemia approach their treatment with the hope of cure despite the effect on their quality of life. Some patients will be cured, others will die from treatment, and some will die of their disease. A common theme at the New Directions in Leukemia Research (NDLR 2012) meeting was that cure will come if the drivers of the disease are better understood. Key messages included the power of combination platforms to understand the genetic and epigenetic modifications in leukemia to enable development of rational therapies, which can be tested via new clinical trial designs ensuring rapid clinical implementation. ©2012 AACR.

Coating and curing apparatus and methods

DOEpatents

Brophy, Brenor L; Maghsoodi, Sina; Neyman, Patrick J; Gonsalves, Peter R; Hirsch, Jeffrey G; Yang, Yu S

2015-02-24

Disclosed are coating apparatus including flow coating and roll-coating that may be used for uniform sol-gel coating of substrates such as glass, solar panels, windows or part of an electronic display. Also disclosed are methods for substrate preparation, flow coating and roll coating. Lastly systems and methods for skin curing sol-gel coatings deposited onto the surface of glass substrates using a high temperature air-knife are disclosed.

A class of semiparametric cure models with current status data.

PubMed

Diao, Guoqing; Yuan, Ao

2018-02-08

Current status data occur in many biomedical studies where we only know whether the event of interest occurs before or after a particular time point. In practice, some subjects may never experience the event of interest, i.e., a certain fraction of the population is cured or is not susceptible to the event of interest. We consider a class of semiparametric transformation cure models for current status data with a survival fraction. This class includes both the proportional hazards and the proportional odds cure models as two special cases. We develop efficient likelihood-based estimation and inference procedures. We show that the maximum likelihood estimators for the regression coefficients are consistent, asymptotically normal, and asymptotically efficient. Simulation studies demonstrate that the proposed methods perform well in finite samples. For illustration, we provide an application of the models to a study on the calcification of the hydrogel intraocular lenses.

From Diabetes Care to Diabetes Cure-The Integration of Systems Biology, eHealth, and Behavioral Change.

PubMed

van Ommen, Ben; Wopereis, Suzan; van Empelen, Pepijn; van Keulen, Hilde M; Otten, Wilma; Kasteleyn, Marise; Molema, Johanna J W; de Hoogh, Iris M; Chavannes, Niels H; Numans, Mattijs E; Evers, Andrea W M; Pijl, Hanno

2017-01-01

From a biological view, most of the processes involved in insulin resistance, which drives the pathobiology of type 2 diabetes, are reversible. This theoretically makes the disease reversible and curable by changing dietary habits and physical activity, particularly when adopted early in the disease process. Yet, this is not fully implemented and exploited in health care due to numerous obstacles. This article reviews the state of the art in all areas involved in a diabetes cure-focused therapy and discusses the scientific and technological advancements that need to be integrated into a systems approach sustainable lifestyle-based healthcare system and economy. The implementation of lifestyle as cure necessitates personalized and sustained lifestyle adaptations, which can only be established by a systems approach, including all relevant aspects (personalized diagnosis and diet, physical activity and stress management, self-empowerment, motivation, participation and health literacy, all facilitated by blended care and ehealth). Introduction of such a systems approach in type 2 diabetes therapy not only requires a concerted action of many stakeholders but also a change in healthcare economy, with new winners and losers. A "call for action" is put forward to actually initiate this transition. The solution provided for type 2 diabetes is translatable to other lifestyle-related disorders.

How to optimize tuberculosis case finding: explorations for Indonesia with a health system model

PubMed Central

2009-01-01

Background A mathematical model was designed to explore the impact of three strategies for better tuberculosis case finding. Strategies included: (1) reducing the number of tuberculosis patients who do not seek care; (2) reducing diagnostic delay; and (3) engaging non-DOTS providers in the referral of tuberculosis suspects to DOTS services in the Indonesian health system context. The impact of these strategies on tuberculosis mortality and treatment outcome was estimated using a mathematical model of the Indonesian health system. Methods The model consists of multiple compartments representing logical movement of a respiratory symptomatic (tuberculosis suspect) through the health system, including patient- and health system delays. Main outputs of the model are tuberculosis death rate and treatment outcome (i.e. full or partial cure). We quantified the model parameters for the Jogjakarta province context, using a two round Delphi survey with five Indonesian tuberculosis experts. Results The model validation shows that four critical model outputs (average duration of symptom onset to treatment, detection rate, cure rate, and death rate) were reasonably close to existing available data, erring towards more optimistic outcomes than are actually reported. The model predicted that an intervention to reduce the proportion of tuberculosis patients who never seek care would have the biggest impact on tuberculosis death prevention, while an intervention resulting in more referrals of tuberculosis suspects to DOTS facilities would yield higher cure rates. This finding is similar for situations where the alternative sector is a more important health resource, such as in most other parts of Indonesia. Conclusion We used mathematical modeling to explore the impact of Indonesian health system interventions on tuberculosis treatment outcome and deaths. Because detailed data were not available regarding the current Indonesian population, we relied on expert opinion to quantify the parameters. The fact that the model output showed similar results to epidemiological data suggests that the experts had an accurate understanding of this subject, thereby reassuring the quality of our predictions. The model highlighted the potential effectiveness of active case finding of tuberculosis patients with limited access to DOTS facilities in the developing country setting. PMID:19505296

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

Janke, C.J.

Electron beam (EB) curing is a technology that promises, in certain applications, to deliver lower cost and higher performance polymer matrix composite (PMC) structures compared to conventional thermal curing processes. PMCs enhance performance by making products lighter, stronger, more durable, and less energy demanding. They are essential in weight- and performance-dominated applications. Affordable PMCs can enhance US economic prosperity and national security. US industry expects rapid implementation of electron beam cured composites in aircraft and aerospace applications as satisfactory properties are demonstrated, and implementation in lower performance applications will likely follow thereafter. In fact, at this time and partly becausemore » of discoveries made in this project, field demonstrations are underway that may result in the first fielded applications of electron beam cured composites. Serious obstacles preventing the widespread use of electron beam cured PMCs in many applications are their relatively poor interfacial properties and resin toughness. The composite shear strength and resin toughness of electron beam cured carbon fiber reinforced epoxy composites were about 25% and 50% lower, respectively, than those of thermally cured composites of similar formulations. The essential purpose of this project was to improve the mechanical properties of electron beam cured, carbon fiber reinforced epoxy composites, with a specific focus on composite shear properties for high performance aerospace applications. Many partners, sponsors, and subcontractors participated in this project. There were four government sponsors from three federal agencies, with the US Department of Energy (DOE) being the principal sponsor. The project was executed by Oak Ridge National Laboratory (ORNL), NASA and Department of Defense (DOD) participants, eleven private CRADA partners, and two subcontractors. A list of key project contacts is provided in Appendix A. In order to properly manage the large project team and properly address the various technical tasks, the CRADA team was organized into integrated project teams (IPT's) with each team focused on specific research areas. Early in the project, the end user partners developed ''exit criteria'', recorded in Appendix B, against which the project's success was to be judged. The project team made several important discoveries. A number of fiber coatings or treatments were developed that improved fiber-matrix adhesion by 40% or more, according to microdebond testing. The effects of dose-time and temperature-time profiles during the cure were investigated, and it was determined that fiber-matrix adhesion is relatively insensitive to the irradiation procedure, but can be elevated appreciably by thermal postcuring. Electron beam curable resin properties were improved substantially, with 80% increase in electron beam 798 resin toughness, and {approx}25% and 50% improvement, respectively, in ultimate tensile strength and ultimate tensile strain vs. earlier generation electron beam curable resins. Additionally, a new resin electron beam 800E was developed with generally good properties, and a very notable 120% improvement in transverse composite tensile strength vs. earlier generation electron beam cured carbon fiber reinforced epoxies. Chemical kinetics studies showed that reaction pathways can be affected by the irradiation parameters, although no consequential effects on material properties have been noted to date. Preliminary thermal kinetics models were developed to predict degree of cure vs. irradiation and thermal parameters. These models are continually being refined and validated. Despite the aforementioned impressive accomplishments, the project team did not fully realize the project objectives. The best methods for improving adhesion were combined with the improved electron beam 3K resin to make prepreg and uni-directional test laminates from which composite properties could be determined. Nevertheless, only minor improvements in the composite shear strength, and moderate improvements in the transverse tensile strength, were achieved. The project team was not satisfied with the laminate quality achieved, and low quality (specifically, high void fraction) laminates will compromise the composite properties. There were several problems with the prepregging and fabrication, many of them related to the use of new fiber treatments.« less

Effects of Discovery, Iteration, and Collaboration in Laboratory Courses on Undergraduates' Research Career Intentions Fully Mediated by Student Ownership

ERIC Educational Resources Information Center

Corwin, Lisa A.; Runyon, Christopher R.; Ghanem, Eman; Sandy, Moriah; Clark, Greg; Palmer, Gregory C.; Reichler, Stuart; Rodenbusch, Stacia E.; Dolan, Erin L.

2018-01-01

Course-based undergraduate research experiences (CUREs) provide a promising avenue to attract a larger and more diverse group of students into research careers. CUREs are thought to be distinctive in offering students opportunities to make discoveries, collaborate, engage in iterative work, and develop a sense of ownership of their lab course…

Development of an alternative low salt bovine hide preservation using PEG and crude glycerol, part 1: evaluation of PEG molecular weight fractions

USDA-ARS?s Scientific Manuscript database

Brine curing using sodium chloride is widely used for the short-term preservation of cattle hides. Due to economics and efficiency, it has become the traditional method of hide preservation used by meat packers, hide processors, and tanners worldwide. But brine curing is known to cause serious efflu...

Strength and Durability Performance of Alkali-Activated Rice Husk Ash Geopolymer Mortar

PubMed Central

Kim, Yun Yong; Lee, Byung-Jae; Saraswathy, Velu

2014-01-01

This paper describes the experimental investigation carried out to develop the geopolymer concrete based on alkali-activated rice husk ash (RHA) by sodium hydroxide with sodium silicate. Effect on method of curing and concentration of NaOH on compressive strength as well as the optimum mix proportion of geopolymer mortar was investigated. It is possible to achieve compressive strengths of 31 N/mm2 and 45 N/mm2, respectively for the 10 M alkali-activated geopolymer mortar after 7 and 28 days of casting when cured for 24 hours at 60°C. Results indicated that the increase in curing period and concentration of alkali activator increased the compressive strength. Durability studies were carried out in acid and sulfate media such as H2SO4, HCl, Na2SO4, and MgSO4 environments and found that geopolymer concrete showed very less weight loss when compared to steam-cured mortar specimens. In addition, fluorescent optical microscopy and X-ray diffraction (XRD) studies have shown the formation of new peaks and enhanced the polymerization reaction which is responsible for strength development and hence RHA has great potential as a substitute for ordinary Portland cement concrete. PMID:25506063

Strength and durability performance of alkali-activated rice husk ash geopolymer mortar.

PubMed

Kim, Yun Yong; Lee, Byung-Jae; Saraswathy, Velu; Kwon, Seung-Jun

2014-01-01

This paper describes the experimental investigation carried out to develop the geopolymer concrete based on alkali-activated rice husk ash (RHA) by sodium hydroxide with sodium silicate. Effect on method of curing and concentration of NaOH on compressive strength as well as the optimum mix proportion of geopolymer mortar was investigated. It is possible to achieve compressive strengths of 31 N/mm(2) and 45 N/mm(2), respectively for the 10 M alkali-activated geopolymer mortar after 7 and 28 days of casting when cured for 24 hours at 60°C. Results indicated that the increase in curing period and concentration of alkali activator increased the compressive strength. Durability studies were carried out in acid and sulfate media such as H2SO4, HCl, Na2SO4, and MgSO4 environments and found that geopolymer concrete showed very less weight loss when compared to steam-cured mortar specimens. In addition, fluorescent optical microscopy and X-ray diffraction (XRD) studies have shown the formation of new peaks and enhanced the polymerization reaction which is responsible for strength development and hence RHA has great potential as a substitute for ordinary Portland cement concrete.

Lamination cooling system formation method

DOEpatents

Rippel, Wally E [Altadena, CA; Kobayashi, Daryl M [Monrovia, CA

2012-06-19

An electric motor, transformer or inductor having a cooling system. A stack of laminations have apertures at least partially coincident with apertures of adjacent laminations. The apertures define straight or angled cooling-fluid passageways through the lamination stack. Gaps between the adjacent laminations are sealed by injecting a heat-cured sealant into the passageways, expelling excess sealant, and heat-curing the lamination stack. Manifold members adjoin opposite ends of the lamination stack, and each is configured with one or more cavities to act as a manifold to adjacent passageway ends. Complex manifold arrangements can create bidirectional flow in a variety of patterns.

Lamination cooling system formation method

DOEpatents

Rippel, Wally E [Altadena, CA; Kobayashi, Daryl M [Monrovia, CA

2009-05-12

An electric motor, transformer or inductor having a cooling system. A stack of laminations have apertures at least partially coincident with apertures of adjacent laminations. The apertures define straight or angled cooling-fluid passageways through the lamination stack. Gaps between the adjacent laminations are sealed by injecting a heat-cured sealant into the passageways, expelling excess sealant, and heat-curing the lamination stack. Manifold members adjoin opposite ends of the lamination stack, and each is configured with one or more cavities to act as a manifold to adjacent passageway ends. Complex manifold arrangements can create bidirectional flow in a variety of patterns.

New methods to quantify the cracking performance of cementitious systems made with internal curing

NASA Astrophysics Data System (ADS)

Schlitter, John L.

The use of high performance concretes that utilize low water-cement ratios have been promoted for use in infrastructure based on their potential to increase durability and service life because they are stronger and less porous. Unfortunately, these benefits are not always realized due to the susceptibility of high performance concrete to undergo early age cracking caused by shrinkage. This problem is widespread and effects federal, state, and local budgets that must maintain or replace deterioration caused by cracking. As a result, methods to reduce or eliminate early age shrinkage cracking have been investigated. Internal curing is one such method in which a prewetted lightweight sand is incorporated into the concrete mixture to provide internal water as the concrete cures. This action can significantly reduce or eliminate shrinkage and in some cases causes a beneficial early age expansion. Standard laboratory tests have been developed to quantify the shrinkage cracking potential of concrete. Unfortunately, many of these tests may not be appropriate for use with internally cured mixtures and only provide limited amounts of information. Most standard tests are not designed to capture the expansive behavior of internally cured mixtures. This thesis describes the design and implementation of two new testing devices that overcome the limitations of current standards. The first device discussed in this thesis is called the dual ring. The dual ring is a testing device that quantifies the early age restrained shrinkage performance of cementitious mixtures. The design of the dual ring is based on the current ASTM C 1581-04 standard test which utilizes one steel ring to restrain a cementitious specimen. The dual ring overcomes two important limitations of the standard test. First, the standard single ring test cannot restrain the expansion that takes place at early ages which is not representative of field conditions. The dual ring incorporates a second restraining ring which is located outside of the sample to provide restraint against expansion. Second, the standard ring test is a passive test that only relies on the autogenous and drying shrinkage of the mixture to induce cracking. The dual ring test can be an active test because it has the ability to vary the temperature of the specimen in order to induce thermal stress and produce cracking. This ability enables the study of the restrained cracking capacity as the mixture ages in order to quantify crack sensitive periods of time. Measurements made with the dual ring quantify the benefits from using larger amounts of internal curing. Mixtures that resupplied internal curing water to match that of chemical shrinkage could sustain three times the magnitude of thermal change before cracking. The second device discussed in this thesis is a large scale slab testing device. This device tests the cracking potential of 15' long by 4" thick by 24" wide slab specimens in an environmentally controlled chamber. The current standard testing devices can be considered small scale and encounter problems when linking their results to the field due to size effects. Therefore, the large scale slab testing device was developed in order to calibrate the results of smaller scale tests to real world field conditions such as a pavement or bridge deck. Measurements made with the large scale testing device showed that the cracking propensity of the internally cured mixtures was reduced and that a significant benefit could be realized.

Identifying Immune Drivers of Gulf War Illness Using Novel Daily Sampling Approach

DTIC Science & Technology

2013-10-01

of Gulf War Illness (GWI). We are targeting an enrollment of 60 men (40 veterans with GWI, 10 veterans with no GWI, and 10 with fibromyalgia ) over... treatment of the disorder. In order to make gains in curing GWI, it is essential that we develop objective, physiologic-based tests for the disorder...and identify physiological targets for treatments . The major aim of this research project is to identify aspects of the immune system that are

Durability and Strength of Sustainable Self-Consolidating Concrete Containing Fly Ash

NASA Astrophysics Data System (ADS)

Mohamed, O.; Hawat, W. Al

2018-03-01

In this paper, the durability and strength of self-consolidating concrete (SCC) is assessed through development and testing of six binary mixes at fixed water-to-binder (w/b) ratio of 0.36. In each of the six SCC mixes, a different percentage of cement is replaced with fly ash. The development of compressive strength for each of the mixes is assessed by testing samples after 3, 7, and 28 days of curing. Durability of each of the six SCC mixes is assessed by measuring the charge passed in Rapid Chloride Permeability (RCP) test. Charge passed was measured in samples cured for 1, 3, 7, 14, 28, and 40 days of curing. All mixes out-performed the control mix in terms of resistance to chloride penetration. Binary mix in which 20% of cement is replaced with fly ash exhibited 28-day strength slightly surpassing the control mix.

Development and demonstration of manufacturing processes for fabricating graphite/Larc-160 polyimide structural elements, part 4, paragraph C

NASA Technical Reports Server (NTRS)

1981-01-01

Progress in the development of processes for production of Celion/LARC-160 graphite-polyimide materials, quality control methods, and the fabrication of Space Shuttle composite structure components is reported. The formulation and processing limits for three batches of resin are presented. Process improvements for simplification of the imidizing and autoclave cure cycles are described. Imidized and autoclave cured test panels were prepared. Celion/LARC-160 cure process verification and the fabrication of honeycomb sandwich panel elements and skin/stringer panels are described. C-scans of laminates imidized at 163 C to 218 C for periods from 30 to 180 minutes, and of process verification laminates made from different batches of prepreg are presented. Failure modes and load/strain characteristics of sandwich elements and C-scans of stringer to skin bond joints are also given.