Azolium-based systems: application of an anion exchange resin (A- form) method and 1H NMR analysis of the charged-assisted (CH)+·anion hydrogen bonds

The counteranion exchange of quaternary 1,2,3-triazolium salts was examined using a simple method that permitted halide ions to be swap for a variety of anions using an anion exchange resin (A¯ form). The method was applied to 1,2,3-triazolium-based ionic liquids and the iodideto- anion exchange proceeded in excellent to quantitative yields, concomitantly removing halide impurities. Additionally, an anion exchange resin (N3¯ form) was used to obtain the benzyl azide from benzyl halide under mild reaction. Likewise, following a similar protocol, bis(azidomethyl)arenes were also synthesized in excellent yields. The results of a proton NMR spectroscopic study of simple azolium-based ion pairs are discussed, with attention focused on the significance of the charged-assisted (CH)+···anion hydrogen bonds of simple azolium systems such as 1-butyl-3-methylimidazolium and 1-benzyl-3-methyl-1,2,3-triazolium salts.

Pregabalin in the treatment of inferior alveolar nerve paraesthesia following overfilling of endodontic sealer

A case of orofacial pain and inferior alveolar nerve (IAN) paraesthesia after extrusion of endodontic sealer within the mandibular canal treated with prednisone and pregabalin is described. A 36-year-old woman underwent root canal treatment of the mandibular second right premolar tooth. Post-operative panoramic radiograph revealed the presence of radiopaque canal sealer in the mandibular canal. Damage to IAN consecutive to extrusion of endodontic sealer was diagnosed. Non-surgical management was decided, including: 1 mg/kg/day prednisone 2 times/day, once-daily regimen, and 150 mg/day pregabalin, two doses per day, monitoring the progress with periodic follow-up visits. Six weeks after the incident the signs and symptoms were gone. The complete resolution of paraesthesia and the control of pain achieved suggest that a non-surgical approach, combining prednisone and the GABA analogue pregabalin, is a good option in the management of the IAN damage subsequent to endodontic sealer extrusion

Separation and preconcentration of copper in environmental samples on Amberlite XAD-8 resin after complexation with a carbothioamide derivative

A new solid phase extraction (SPE) method has been developed for the selective separation and preconcentration of Cu (II) ions in food and water samples prior to its flame atomic absorption spectrometry determination. The method is based on the adsorption of the Cu(II) - 2-{[4-Amino-3-(4-methylphenyl-5-oxo-4,5-dihydro-1H-1,2,4-triazol-1-yl]acetyl}-N-phenyl hydrazinecarbothioamide complex on Amberlite XAD-8 resin. The metal complex retained on the resin was eluted with 7.5 mL of 2.0 mol L-1 HCl in acetone. The optimum conditions for the SPE of Cu(II) ions were investigated, and the method was subsequently applied to sea water, stream water, rice, tea, and tobacco samples for the determination of Cu(II) levels.

Separation and purification of three stilbenes from the radix of Polygonum cillinerve (Nakai) Ohwl by macroporous resin column chromatography combined with high-speed counter-current chromatography

An effective method for the rapid separation and purification of three stilbenes from the radix of Polygonum cillinerve (Nakai) Ohwl by macroporous resin column chromatography combined with high-speed counter-current chromatography (HSCCC) was successfully established. In the present study, a two-phase solvent system composed of chloroform-n-butanol-methanol-water (4:1:4:2, v/v/v/v) was used for HSCCC separation. A one-step separation in 4 h from 150 mg of crude extract produced 26.3 mg of trans-resveratrol-3-O-glucoside, 42.0 mg of pieceid-2"-O-gallate, and 17.9 mg of trans-resveratrol with purities of 99.1%, 97.8%, and 99.4%, respectively, as determined by high-performance liquid chromatography (HPLC). The chemical structures of these compounds were identified by nuclear magnetic resonance (NMR) spectroscopy.

Flow injection spectrophotometric determination of adrenaline using a solid-phase reactor containing triiodide ions immobilized in an anion-exchange resin

A flow injection spectrophotometric procedure with on-line solid-phase reactor containing ion triiodide immobilized in an anion-exchange resin is proposed for the determination of adrenaline (epinephrine) in pharmaceutical products. Adrenaline is oxidized by triiodide ion immobilized in an anionic-exchange resin yielding adrenochrome which is transported by the carrier solution and detected at a wavelength of 488 nm. Adrenaline was determined in three pharmaceutical products in the 6.4 x 10-6 to 3.0 x 10-4 mol L-1 concentration range with a detection limit of 4.8 x 10-7 mol L-1. The recovery of this analyte in three samples ranged from 96.0 to 105 %. The analytical frequency was 80 determinations per hour and the RSDs were less than 1 % for adrenaline concentrations of 6.4 x 10-5 and 2.0 x 10-4 mol L-1 (n=10). A paired t-test showed that all results obtained for adrenaline in commercial formulations using the proposed flow injection procedure and a spectrophotometric batch procedure agree at the 95% confidence level.

Rigid Rod Polymer Fillers in Acrylic Denture and Dental Adhesive Resin Systems

Polymeric materials have been used in dental applications for decades. Adhesion of polymeric materials to each other and to the tooth substrate is essential to their successful use. The aim of this series of studies was two-folded. First, to improve adhesion of poly(paraphenylene) based rigid rod polymer (RRP) to other dental polymers, and secondly, to evaluate the usability of a new dentin primer system based on RRP fillers. Poly(paraphenylene) based RRP would be a tempting material for dental applications because of its good mechanical properties. To be used in dental applications, reliable adhesion between RRP and other dental polymers is required. In this series of studies, the adhesion of RRP to denture base polymer and the mechanical properties of RRP-denture base polymer-material combination were evaluated. Also adhesion of BisGMA-TEGDMA-resin to RRP was determined. Different surface treatments were tested to improve the adhesion of BisGMA-TEGDMA-resin to RRP. Results were based on three-point bending testing, Vickers surface hardness test and scanning electron microscope analysis (SEM), which showed that no reliable adhesion between RRP and denture base polymer was formed. Addition of RRP filler to denture base polymer increased surface hardness and flexural modulus but flexural strength decreased. Results from the shear bond strength test and SEM revealed that adhesion between resin and RRP was possible to improve by surface treatment with dichloromethane (DCM) based primer and a new kind of adhesive surface can be designed. The current dentin bonding agents have good immediate bond strength, but in long term the bond strength may decrease due to the detrimental effect of water and perhaps by matrix metalloproteinases. This leads to problems in longevity of restorations. Current bonding agents use organic monomers. In this series of studies, RRP filled dentin primer was tested in order to decrease the water sorption of the monomer system of the primers. The properties of new dentin primer system were evaluated in vitro by comparing it to commercial etch and rinse adhesive system. The results from the contact angle measurements and SEM showed that experimental primer with RRP reinforcement provided similar resin infiltration to dentin collagen and formed the resin-dentin interface as the control primer. Microtensile bond strength test and SEM revealed that in short term water storing, RRP increased bond strength and primer with BMEP-monomer (bis[2-(methacryloyloxy)-ethyl]phosphate) and high solvent concentration provided comparable bonding properties to the commercial control primers. In long term water storing, the high solvent-monomer concentration of the experimental primers decreased bond strength. However, in low solvent-monomer concentration groups, the long-term water storing did not decrease the bond strength despite the existence of hydrophilic monomers which were used in the system. These studies demonstrated that new dentin primer system reached the mechanical properties of current traditional etch and rinse adhesive system in short time water storing. Improved properties can be achieved by further modifications of the monomer system. Studies of the adhesion of RRP to other polymers suggest that adhesion between RRP and other dental polymers is possible to obtain by certain surface treatments.

Bonding of Composite Resin to Alumina and Zirconia Ceramics with Special Emphasis on Surface Conditioning and Use of Coupling Agents

Dental oxide ceramics have been inspired by their biocompability and mechanical properties which have made durable all-ceramic structures possible. Clinical longevity of the prosthetic structures is dependent on effective bonding with luting cements. As the initial shear bond strength values can be comparable with several materials and procedures, long-term durability is affected by ageing. Aims of the current study were: to measure the shear bond strength of resin composite-to-ceramics and to evaluate the longevity of the bond; to analyze factors affecting the bond, with special emphasis on: the form of silicatization of the ceramic surface; form of silanization; type of resin primer and the effect of the type of the resin composite luting cement; the effect of ageing in water was studied regarding its effect to the endurance of the bond. Ceramic substrates were alumina and yttrium stabilized zirconia. Ceramic conditioning methods included tribochemical silicatization and use of two silane couplings agents. A commercial silane primer was used as a control silane. Various combinations of conditioning methods, primers and resin cements were tested. Bond strengths were measured by shear bond strength method. The longevity of the bond was generally studied by thermocycling the materials in water. Additionally, in one of the studies thermal cycling was compared with long-term water storaging. Results were analysed statistically with ANOVA and Weibull analysis. Tribochemical treatment utilizing air pressure of 150 kPa resulted shear bond strengths of 11.2 MPa to 18.4 MPa and air pressure of 450 kPa 18.2 MPa to 30.5 MPa, respectively. Thermocycling of 8000 cycles or four years water storaging both decreased shear bond strength values to a range of 3.8 MPa to 7.2 MPa whereas initial situation varied from 16.8. Mpa to 23.0 MPa. The silane used in studies had no statistical significance. The use of primers without 10-MDP resulted spontaneous debonding during thermocycling or shear bond strengths below 5 MPa. As conclusion, the results showed superior long-term bonding with primers containing 10-MDP. Silicatization with silanizing showed improved initial shear bond strength values which considerably decreased with ageing in water. Thermal cycling and water storing for up to four years played the major role in reduction of bond strength, which could be due to thermal fatigue of the bonding interface and hydrolytic degradation of the silane coupled interface.

Rat hindlimb joint immobilization with acrylic resin orthoses

The objective of the present study was to propose an orthosis of light material that would be functional for the animal and that would maintain only the ankle joint immobilized. Male Wistar rats (3 to 4 months old, 250-300 g) were divided into 2 groups (N = 6): control and immobilized for 7 days. Rats were anesthetized with sodium pentobarbital (40 mg/kg weight) and the left hindlimb was immobilized with the orthoses composed of acrylic resin model, abdominal belt and lateral supports. The following analyses were performed: glycogen content of the soleus, extensor digitorum longus, white gastrocnemius, red gastrocnemius, and tibialis anterior muscles by the phenol sulfuric method, and the weight, fiber area and intramuscular connective tissue of the soleus by the planimetric system. Data were analyzed statistically by the Kolmogorov-Smirnov, Student t and Wilcoxon tests. Immobilization decreased glycogen in all muscles (P < 0.05; soleus: 31.6%, white gastrocnemius: 56.6%, red gastrocnemius: 39%, extensor digitorum longus: 41.7%, tibialis anterior: 45.2%) in addition to reducing soleus weight by 34% (P < 0.05). Furthermore, immobilization promoted reduction of the fiber area (43%, P < 0.05) and increased the connective tissue (200%, P < 0.05). The orthosis model was efficient comparing with another alternative immobilization model, like plaster casts, in promoting skeletal muscle alterations, indicating that it could be used as a new model in other studies related to muscle disuse.

Construction of 2D transparent micromodels in polyester resin with porosity similar to carrots

Microscopic visualization, especially in transparent micromodels, can provide valuable information to understand the transport phenomena at pore scale in different process occurring in porous materials (food, timber, soils, etc.). Micromodels studies focus mainly on the observation of multi-phase flow, which presents a greater proximity to reality. The aim of this study was to study the process of flexography and its application in the manufacture of polyester resin transparent micromodels and its application to carrots. Materials used to implement a flexo station for micromodels construction were thermoregulated water bath, exposure chamber to UV light, photosensitive substance (photopolymer), RTV silicone polyester resin, and glass plates. In this paper, data on size distribution of a particular kind of carrot we used, and a transparent micromodel with square cross-section as well as a Log-normal pore size distribution with pore radii ranging from 10 to 110 µm (average of 22 µm and micromodel size of 10 × 10 cm) were built. Finally, it stresses that it has successfully implemented the protocol processing 2D polyester resin transparent micromodels.

Effect of treatment with adsorbent resin on the volatile profile and physicochemical characteristics of clarified cashew apple juice

Increased preference for healthy and functional foods could be an opportunity to increase the consumption of clarified cashew apple juice. Given its level of fructose, glucose, and vitamin C, it can be used as a base in blends. However, its characteristic odor can interfere with the acceptance of these formulations, especially by consumers who are not familiar with cashew aroma. The aim of this study was to evaluate the effect of treatment with macroporous resins (FPA54, FPX66, XAD761, and XAD4) on the volatile profile and physicochemical characteristics of clarified cashew apple juice. After the treatment with the resins, the volatile profile was evaluated using solid-phase microextraction (SPME) and gas chromatography/mass spectrometry (GC/MS). The physicochemical analyses performed were: pH, soluble solids (ºBrix), total titrable acidity, reducing sugars, and vitamin C. Gas chromatography analyses showed that XAD4 and FPX66 led to a reduction of the initial amount of volatile compounds to 14.05% and 15.72%, respectively. These two resins also did not affect the physicochemical characteristics of the clarified cashew apple juice.

Optimal distance of the light-curing tip for light transmission through the resin composite

Hammaslääketieteessä käytetettävien komposiittien valonläpäisevyys vaihtelee. Samoin LED-valokovettimet eroavat toisistaan valotehonsa ja muotoilunsa perusteella. On yleisesti tiedossa, että valokovettimesta tulevan valon intensiteetti pinta-alayksikköä kohden heikkenee, kun kovettimen etäisyys kasvaa. Toisaalta ei ole tiedossa, miten valokovetettavan kohteen ja valokovettimen kärjen väliin sijoitettu materiaali tarkalleenottaen vaikuttaa valon intensiteettiin eri etäisyyksiä käytettäessä. Tämän tutkimuksen tarkoituksena on selvittää, miten valokovetettavan kohteen ja valokovettimen kärjen väliin asetettava etukäteen polymerisoitu materiaali vaikuttaa valon intensiteettiin eri etäisyyksillä. Tutkimus suoritettiin käyttämällä kahta eri valokovetinta. Jotta etäisyyden vaikutusta valotustehoon voitiin demonstroida, vaihdettiin kovettimen etäisyyttä sensorista 0,2,4,6,8,10mm välillä. Valotehot rekisteröitiin MARC resin calibrator -laitteella. Sensorin ja valokovettimen kärjen väliin asetettavat erilaiset komposiittilevyt olivat valmiiksi kovetettuja,1mm paksuisia, filleripitoisuuksiltaan neljää erilaista muovia. Valotehot rekisteröitiin jokaiselta etäisyydeltä komposiitin ollessa sensorin päällä. Rinnakkaisesti verrattiin myös etäisyyden vaikutusta valotehoon ilman esikovetettua materiaalia kovettimen kärjen ja valoa mittaavan sensorin välissä. Vertailun suorittamiseksi laskettiin intensiteettisuhdeluku muovillisen ja muovittoman arvon välillä aina tietyllä etäisyydellä Valokovettimen kärjen etäisyyden kasvattaminen sensorista (eli valokovetettavasta kohteesta) odotusten mukaisesti pienensi valotehoa. Laittamalla sensorin ja kovettimen väliin komposiittilevy, valoteho pieneni odotetusti vielä enemmän. Tutkittaessa intensiteettisuhdetta (valoteho muovin kanssa : valoteho ilman muovia) kuitenkin huomattiin, että 4-6mm:n kohdalla suhdeluku oli suurempi kuin 0,2,8 ja 10mm kohdalla. Johtopäätöksenä oli, että suurin mahdollinen valokovetusteho saavutetan laittamalla kovetuskärki mahdollisimman lähelle kohdetta. Jos valokovetettavan kohteen ja valokovettimen kärjen välissä oli kiinteä komposiittipalanen, suurin mahdollinen valokovetusteho kohteeseen saavutetaan edelleen laittamalla kovetuskärki kiinni muoviin. Jos etäisyyttä muovin pinnasta sen sijaan kasvatettiin, valokovetusteho ei laskenutkaan niin nopeasti kuin oli odotettu. Tämä voi liittyä siihen, että tehokkaan valokeilan halkaisijan koko on suurempi verrattuna komposiitin sekä sensorin halkaisian kokoon. Toiseksi on arvioitu, että resiinikomposiitin täyteaineet voisivat fokusoida läpi kulkevaa valoa sensoriin. Se, pitääkö tämä ilmiö paikkansa, vaatii kuitenkin enemmän tutkimusta

Linear block copolymers of L–lactide and 2–dimethylaminoethyl methacrylate : synthesis and properties

Part of the research described in this thesis is conducted in collaboration with Centre d' étude et de Recherche sur les Macromolécules (CERM), Université de Liège, Sart-Tilman, Belgium

Rheological Characteristics of Short Nylon -6 Fiber Reinforced Styrene Butadiene Rubber Containing Epoxy Resin as Bonding Agent

The rheological characteristics of short Nylon-6 fiber-reinforced Styrene Butadiene rubber (SBR) in the presence of epoxy resin-based bonding agent were studied with respect to the effect of shear rate, fiber concentration , and temperature on shear viscosity and die swell using a capillary rheonzeter. All the composites containing bonding agent showed a pseudoplastic nature, which decreased with increasing temperature. Shear viscosity was increased in the presence of fibers. The temperature sensitivity of the SBR matrices was reduced on introduction of fibers. The temperature sensitivity of the melts was found to be lower at higher shear rates. Die swell was reduced in the presence of fibers. Relative viscosity of the composites increased with shear rate. In the presence of epoxy resin bonding agent the temperature sensitivity of the mixes increased. Die swell was larger in the presence of bonding agent.

Photoacoustic study on photobleaching of Rhodamine 6G doped in poly(methyl methacrylate)

The photobleaching of the lasing dye Rhodamine 6G embedded in the solid matrix poly(methyl methacrylate) was investigated using a photoacoustic technique. Chopped laser radiation from an argon ion laser at four different wavelengths was used for the study. Experimental results indicate that the photobleaching rate is directly proportional to the incident laser power while it decreases with increase in concentration of the dye molecules. In the present case we have not observed any dependence of photobleaching on the chopping frequency. One-photon absorption is found to be responsible for the photobleaching of the dye within the selected range of laser power

Photoacoustic study on photobleaching of Rhodamine 6G doped in poly(methyl methacrylate)

The photobleaching of the lasing dye Rhodamine 6G embedded in the solid matrix poly(methyl methacrylate) was investigated using a photoacoustic technique. Chopped laser radiation from an argon ion laser at four different wavelengths was used for the study. Experimental results indicate that the photobleaching rate is directly proportional to the incident laser power while it decreases with increase in concentration of the dye molecules. In the present case we have not observed any dependence of photobleaching on the chopping frequency. One-photon absorption is found to be responsible for the photobleaching of the dye within the selected range of laser power.