Oleogels Of Olive Oil And Soybean Oil For Topical Drug Delivery: A Comparative Analysis

Objective: The objective of the present investigation was to develop olive and soybean oil-based oleogels with Span 40 and/or Tween 80 (as gelator and/or surfactant) and determine the critical gelator concentration (CGC), characterise and compare the rheological, thermal properties and drug release profile of the gels formed for topical delivery. Methods: Olive and soybean oil-based Span 40 and Span 40/Tween 80 oleogel formulations were prepared by solid fiber mechanism and subjected to organoleptic evaluation, FT-IR spectroscopy, thermal analysis, rheological study, kinetic modeling of gelation and drug release. Results: The critical gelator (Span 40) concentration was found to be lower for olive oil (12% w/v) and depend on the type of oil. Tween 80 reduced CGC of soybean oleogels only. Soybean oil-based oleogel containing 18% w/v Span 40 was found to form more flexible, less viscous and thermally less stable formulation with better release of paracetamol as evident from lower melt flow index, Tg value, lower β and higher α value compared to olive oil-based oleogel with 12% w/v Span 40 (CGC). Surfactant addition can be assumed to modify the microarchitecture of the oleogels to a great extent to produce more flexible and thermally stable gels with even better drug release profile. Span-Tween based soybean oleogel formed a gel-matrix whereas matrix in olive oil-based oleogels containing Span only became slightly flexible to release the drug in zero-order fashion on the addition of surfactant cogelator. Conclusion: Nature of oil exerts profound influence on the rheological, thermal and release profile of oleogels containing Span 40 as gelator and/or Tween 80 as surfactant cogelator.

Physicomechanical and thermal analysis of bulk-fill and conventional composites

Abstract The aim of this study was to evaluate the degree of conversion (DC) and the thermal stability of bulk-fill and conventional composite resins. Eleven composite resin samples were prepared to evaluate the DC, Vickers microhardness (VMH), mass and residue/particle loss, glass transition temperature (Tg), enthalpy, and linear coefficient of thermal expansion (CTE) using infrared spectroscopy (FTIR), microdurometer analyses, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and dilatometry (DIL). The data were subjected to statistical analysis, with a significance level of 95%. DC and VMH were not influenced by the polymerized side of the sample, and statistical differences were recorded only among the materials. Decomposition temperature, melting, and mass and residue loss were dependent on the material and on the evaluation condition (polymerized and non-polymerized). Tg values were similar between the composites, without statistically significant difference, and CTE ranged from 10.5 to 37.1 (10-6/°C), with no statistical difference between the materials. There was a moderate negative correlation between CTE and the % of load particles, by weight. Most resins had a DC above that which is reported in the literature. TGA, Tg, and CTE analyses showed the thermal behavior of the evaluated composites, providing data for future research, assisting with the choice of material for direct or semidirect restorations, and helping choose the appropriate temperature for increasing the DC of such materials.

Effect of relining on the misfit of microwavecured acrylic resin denture bases / Efeito do reembasamento na desadaptação de bases de próteses de resina acrílica polimerizada por micro-ondas

Objective: The aim of this study was to evaluate the effect of microwave-energy polymerization on the accuracy and glass transition temperature of acrylic resin denture bases submitted to reline procedure. As denture wearers make up a large portion of the population and often cannot afford a new complete denture, the reline procedure may be the best alternative when indicated. Thus, it is important to evaluate possible changes that would contraindicate this technique. Materials and methods: Twenty denture bases were fabricated from microwave-cured acrylic resin (Onda-Cryl) and randomly divided into control and test groups (n = 10). In the control group, the bases were submitted to measurement of misfit. Bases in the test group were worn down internally and relined. Misfit was measured by cutting the set stone cast/denture base at three predetermined points (canine, molar and tuberosity), measuring the gap between the stone cast and the acrylic resin base at three points using the ImageTool®software suite. Differential scanning calorimetry was used to determine Tg. Data were submitted to t-test for independent- samples (p<0.05). Results: The greatest misfit of canine sections was found at the midpoint of control group (0.280 mm); in molar sections, no significant difference was found. In maxillary tuberosity sections, the greatest misfit occurred at the midpoint of test group (0.352 mm). All gaps were below the maximal clinically acceptable misfit value. There was no significant difference in Tg values between groups. Conclusion: Microwave-energy processing does not affect the fit or Tg of relined denture bases.

Objetivo: Avaliar o efeito da polimerização utilizando energia de micro-ondas na adaptação e na temperatura de transição vítrea de bases de prótese submetidas ao procedimento de reembasamento. Uma vez que usuários de próteses totais constituem grande parte da população, o procedimento de reembasamento pode ser a melhor alternativa, quando indicado. Assim, se faz importante a avaliação de possíveis alterações que contraindicariam esta técnica. Materiais e Métodos: Foram confeccionadas 20 bases de prótese utilizando resina acrílica polimerizada por micro-ondas (Onda-Cryl) e divididas aleatoriamente em grupo controle e teste (n=10). No grupo controle as bases foram submetidas à mensuração da desadaptação. Já no grupo teste as bases foram desgastadas internamente e submetidas ao procedimento de reembasamento utilizando a mesma resina acrílica e a polimerização por energia de micro-ondas. A desadaptação foi mensurada por meio do corte do conjunto modelo de gesso/ base de prótese, em três pontos pré-determinados, em ambos os grupos. Cada área seccionada foi mensurada em três pontos, utilizando o programa ImageTool®software. O ensaio de calorimetria exploratória diferencial foi utilizado para determinar a Tg em ambos os grupos. Os dados foram submetidos ao teste t para amostras independentes (p<0,05). Resultados: No bloco de canino, a maior desadaptação foi observada no ponto mediano do grupo controle (0,280 mm); no bloco de molares não houve diferença estatística entre os grupos. Já na comparação dos blocos de tuber, a maior desadaptação ocorreu no ponto mediano do grupo teste (0,352 mm). Apesar dos valores de desadaptação encontrados, nenhum foi igual ou superior ao valor máximo aceito clinicamente. Conclusão: A polimerização utilizando energia de micro-ondas não afetou a adaptação ou a Tg das bases de prótese submetidas ao reembasamento.

Glass transition of Chinese medicine extract powder and its application / 中国中药杂志

Glass transition theory is an important theory in polymer science, which is used to characterize the physical properties. It refers to the transition of amorphous polymer from the glassy state to the rubber state due to heating or the transition from rubber state to glassy state due to cooling. In this paper, the glassy state and glass transition of food and the similar relationship between the composition of Chinese medicine extract powder and food ingredients were described; the determination method for glass transition temperature (Tg) of Chinese medicine extract powder was established and its main influencing factors were analyzed. Meanwhile, the problems in drying process, granulation process and Chinese medicine extract powder and solid preparation storage were analyzed and investigated based on Tg, and then the control strategy was put forward to provide guidance for the research and production of Chinese medicine solid preparation.

Determination of Phase-transition Temperature of White Vaseline Produced by Different Processes by DSC / 中国药师

Objective:To determine the phase-transition temperature of white vaseline produced by different processes by differen-tial scanning calorimetry ( DSC) in order to analyze the relevance between the melting point and the phase-transition temperature and the relevance between different production processes and the phase-transition temperature. Methods: Hermertic aluminum pans were used to encapsulate the samples, and the testing conditions were optimized. The sample weight was about 10 mg, and the range of measuring temperature was -20-100℃. The heating rate was 5℃·min-1 and the flow rate of nitrogen was 30 ml·min-1 . Results:The phase-transition temperature and the melting point were significantly different. The phase-transition temperature of white vaseline samples produced by different processes was quite different. Conclusion:Melting point determination in the current standard method of white vaseline exists defects, and the composition of white vaseline produced by various processes is quite different.

Root surface temperatura variation during mechanical removal of root canal filling material: an in vitro study / Variaciones térmicas en la superficie radiculardurante la desobturación mecánica del conducto. estudio in vitro

The aim of this study was to analyze in vitro temperature changeson the outer surface of the dental root during mechanical fillingremoval procedures.Thirty recently extracted single­rooted lower premolars were cuttransversally at 16 mm from the apex in order to standardizesample length. Endodontic treatment was performed on them. Thefilling material was subsequently removed using Gates Glidden(G1, G2, G3); Peeso (P1, P2, P3) and PostecPlus FRC (FRC)reamers while temperatures were measured on the outer surfaceusing a digital device with thermocouple at 0, 2, 4, 6, 8, 10 and 15seconds. Temperatures were compared using repeated measuresANOVA followed by pairwise comparison with Tukey’s test.All reamers caused significant temperature variation betweendifferent times (p<0.05). Pairwise comparisons indicated thattemperature increased with time for all reamers (p<0.05).Significant differences in temperature were found betweendifferent reamers after 0, 2, 4, 6, 8, 10 and 15 seconds (p<0.05)...

El objetivo del presente trabajo fue estudiar los cambios térmicosin vitro en la superficie externa de la raíz del diente, generadosdurante los procedimientos de desobturación mecánica.Se utilizaron 30 premolares inferiores unirradiculares reciente ­mente extraídos, que fueron seccionados transversalmente a16 mm del ápice para estandardizar la longitud de lasmuestras. Se realizó luego su tratamiento endodóntico. Lasmediciones de temperatura fueron realizadas mediante undispositivo digital con termocupla, en la superficie externa adiferentes tiempos (t = 0, 2, 4, 6, 8, 10 y 15 segundos), durantela desobturación con fresas de Gates Glidden (G1, G2, G3);de Peeso (P1, P2, P3) y la correspondiente a PostecPlus FRC(FRC). Los registros de temperatura fueron comparadosmediante pruebas de ANOVA de medidas repetidas, seguidaspor comparaciones entre pares mediante la prueba de Tukey.Con todas las fresas se encontró una variación significativa dela temperatura entre los diferentes tiempos (p<0.05). Las compa ­raciones entre pares indicaron que la temperatura se incrementócon el tiempo en todas las fresas (p<0.05). Se detectarondiferencias significativas de temperatura entre diferentes fresasdespués de 0, 2, 4, 6, 8, 10 y 15 segundos (p<0.05)...

Effect of different DE values of malto-dextrin on properties for Schisandrae Chinensis Fructus spray-dried powder / 中国中药杂志

The purpose of this study was to compare the effect of different DE values of malto-dextrin on Schisandrae Chinensis Fructus spray-dried powder. The glass transition temperature (Tg) of the spray-dried powder, powder properties and microscopic morphology were determined, and then the moisture absorption isotherms and the glass transition temperature were used to predict its storage stability. The study showed that after adding malto-dextrin, the powder rate was increased; moisture content was decreased; Tg was increased; mobility got better; produced spherical microstructure; and Tg was increased with the decrease of DE value. The water activity-equilibrium moisture content (aw-EMC) relationship in GAB models showed, the moisture absorption of powder was increased with the rising of DE value; and the equilibrium moisture content-glass transition temperature (EMC-Tg) relationship in Gordon-Taylor models showed that, Tg was decreased with the increase of moisture content. As a result, the storage critical condition of the spray-dried powder was improved, and along with the decrease of DE value, the critical water activity and the critical water content were increased. Therefore, the smaller the DE value, the greater the stability of the spray-dried powder.

Evaluation on rheological properties of Dange ophthalmic in-situ gel and its common gel / 中草药

Objective: To determine the rheological properties of Dange ophthalmic in-situ gel and its common gel by using dynamic rheological experiments. Methods: Dange ophthalmic in-situ gel was prepared by adopting Poloxamer as thermosensitive material, and Dange gel was prepared by carbopol. Anton Paar MCR302 Rheometer was used to determine the rheological parameters of above two kinds of gel at different temperatures which speculated the phase transition time and gelling temperature of in-situ gel. Results: Dange ophthalmic in-situ gel was Newtonian liquid at low temperature, with its viscous modulus dominated. It was shear-thinning pseudoplastic fluid under the conditions of phase transition at room temperature, with its elastic modulus dominated. The phase transition temperature (Tg) was (24.4 ± 0.1)°C, and the gelling time was 9 s. Dange gel existed in network structure among a certain temperature range, it was stable and did not change with temperature. Conclusion: The test has established the rheological evaluation system of Dange ophthalmic in-situ gel or its common gel, accurately evaluated the rheological properties of the two gels by dynamic rheological parameters, and it can be used as the basis for the quality control of products.

Caracterização de resinas para base de prótese e reembasamento: propriedades físico-químicas e mecânicas / Characterization of denture base and reline resins: physical, chemical and mechanical properties

Este estudo avaliou propriedades físico-químicas e mecânicas de resinas para base de prótese, uma fotoativada (Eclipse - E) à base de UDMA e outra termicamente ativada por micro-ondas (Nature Cryl MC - NC) à base de PMMA, e um reembasador quimicamente ativado (Tokuyama Rebase Fast II - TR II) à base de PEMA. Propriedades viscoelásticas (E', tan δ e Tg), contração linear de polimerização (CLP), sorção (Sor) e solubilidade (Sol) em água e em saliva artificial, grau de conversão (GC) e coeficiente de inchamento (CI) foram avaliados para a caracterização dos polímeros. A resistência à flexão dos materiais intactos (E, NC, TR II) e reembasados (E-E, E-TRII, NC-NC- NC-TR II) também foi avaliada. As propriedades viscoelásticas foram avaliadas em corpos-de-prova retangulares (64 x 10 x 3,3 mm), submetidos (n=2) à análise térmica dinâmico-mecânica (DMTA) em dois ciclos de varredura após confecção (controle) e armazenagem em saliva. O módulo de armazenamento (E') e o amortecimento mecânico (tan δ) a 37 ºC e a temperatura de transição vítrea (Tg) foram registrados durante o 1º ciclo da DMTA. A CLP (%) foi avaliada (n=10), em projetor de perfil (Nikon 6C), em corpos-de-prova circulares (50 x 0,5 mm). A Sor e a Sol (µg/mm3) foram mensuradas (n=5) seguindo as recomendações da ISO 1567. O GC (%) foi avaliado (n=5) por espectroscopia de infravermelho por transformadas de Fourier (32 leituras; resolução 4,0 cm-1 ). O coeficiente de inchamento foi realizado (n=5) de acordo com a teoria de Flory-Rhener. Os ensaios mecânicos de flexão (0,5 mm/min) foram realizados (n=10) em corpos-de-prova (64 x 10 x 3,3 mm) intactos ou reembasados e a resistência (MPa) calculada na tensão máxima (RFM) e no limite de proporcionalidade (RFLP). Os dados foram avaliados por ANOVA, seguida por Tukey HSD (α=0,05) ou Dunnett (α=0,05). As resinas E e NC apresentaram similar E', superior a TR II. O tan δ foi ordenado como TR II > NC > E. A Tg não foi alterada após armazenagem em saliva artificial. Os maiores valores de Tg nos grupos controle e armazenados foram apresentados, respectivamente, pelos materiais E e NC. Houve deslocamento dos picos de tan δ após o segundo ciclo de DMTA. Independente do meio de imersão, a Sor (µg/mm3 ) foi ordenada em NC > E > TR II. A armazenagem em saliva reduziu a Sol (µg/mm3 ) dos materiais. A resina E exibiu os menores valores de CLP, CI e o maior GC. NC exibiu a maior CLP e CI. TR II exibiu valores intermediários de CLP, CI e o menor GC. Os maiores valores de RFM e RFLP foram produzidos por E. A RFM e RFLP dos materiais reembasados foi ordenada em E-E > NC-NC > E-TRII> NC-TR II. A armazenagem em saliva não influenciou a resistência à flexão dos materiais intactos ou reembasados. No geral, a resina para base de prótese E apresentou propriedades físico-químicas e mecânicas superiores à NC e TR II

This study evaluated the physical-chemical and mechanical properties of denture base resins, one UDMA light-activated (Eclipse-E) and one PMMA heat-polymerized (Nature Cryl MC - NC). The PEMA autopolymerizing reliner (Tokuyama Rebase Fast II - TR II) was also evaluated. Viscoelastic properties (E', tan δ e Tg), linear shrinkage polymerization (LPS), sorption (Sor) and solubility (Sol) in water and in artificial saliva, degree of conversion (DC) and coefficient of swelling (CS) were employed for polymer characterization. The flexural strength of intact (E, NC, TR II) and relined samples (E-E, E-TRII, NC-NC- NC-TR II) was also made. The viscoelastic properties were evaluated by two cycles of dynamic mechanical thermal analysis (DMTA) on each rectangular (64 x 10 x 3.3 mm) samples (n=2). The storage modulus (E') and loss tangent (tan δ) at 37 ºC and the glass transition temperature (Tg) were recorded from the 1st DMTA cycle. LPS (%) was evaluated (n=10) by a Nikon 6C optical comparator, on circular samples (50 x 0.5 mm). Sor and Sol (µg/mm3 ) were measured (n=6) according to ISO 1567. DC (%) was evaluated (n=5) by FTIR spectroscopy (32 scans; resolution 4.0 cm-1). CS was evaluated (n=5) by Flory-Rhener theory. A three-point flexural tests (0.5 mm/min) was applied (n=10) on rectangular intact and relined samples. The ultimate flexural strength (FSU) and the flexural strength at the proportional limit (FSPl) were recorded in MPa. Data were analyzed with ANOVA, followed by Tukey HSD (α=0.05) ou Dunnett (α=0.05). E and NC had similar E', higher than TR II. Tan δ was arranged as TR II > NC > E. The Tg was not affected after saliva storage. The higher Tg values were obtained for E and NC. Tan δ peaks were shifted after 2 DMTA cycles. Regardless the medium immersion, Sor (µg/mm3 was arranged as NC > E > TR II. Saliva storage reduced Sol (µg/mm3) of the materials. E showed the lowest values of LPS, CS and the highest value of DC. NC showed the highest LPS and CS.TR II showed intermediated values of LPS, CS and the lowest DC. The highest FSU and FSPl values were exhibited by E. The FSU and FSPl of relined samples were arranged as E-E > NC-NC > E-TRII > NC-TR II. Saliva storage did not affect the flexural strength of intact and relined samples. Overall, the denture base resin E showed higher physicochemical and mechanical properties than NC and TR II

Preparation and characterization of a new kind of firm/soft adjusted poly(D,L-lactic acid)-polyurethane / 中国组织工程研究

10.3969/j.issn.2095-4344.2013.25.017

PCR-based techniques for the detection of minority mutations / 中华检验医学杂志

With the development of molecular biology and molecular genetics,more attention has been taken to the advanced techniques which can be used to detect minority mutations.In recent years,many techniques such as amplification refractory mutation system,PCR clamping,pyrophosphorolysis-activated polymerization,co-amplification at lower denaturation temperature-PCR and digital PCR have been developed,which will make the hereditary disease diagnosis,cancer detection,noninvasive antenatal diagnosis step into a new stage in the near future.This review presents an overview of the principles,aoolications,advantages and disadvantages of these techniques.

Surface characteristics of thermally treated titanium surfaces

PURPOSE: The characteristics of oxidized titanium (Ti) surfaces varied according to treatment conditions such as duration time and temperature. Thermal oxidation can change Ti surface characteristics, which affect many cellular responses such as cell adhesion, proliferation, and differentiation. Thus, this study was conducted to evaluate the surface characteristics and cell response of thermally treated Ti surfaces. METHODS: The samples were divided into 4 groups. Control: machined smooth titanium (Ti-S) was untreated. Group I: Ti-S was treated in a furnace at 300degrees C for 30 minutes. Group II: Ti-S was treated at 500degrees C for 30 minutes. Group III: Ti-S was treated at 750degrees C for 30 minutes. A scanning electron microscope, atomic force microscope, and X-ray diffraction were used to assess surface characteristics and chemical composition. The water contact angle and surface energy were measured to assess physical properties. RESULTS: The titanium dioxide (TiO2) thickness increased as the treatment temperature increased. Additional peaks belonging to rutile TiO2 were only found in group III. The contact angle in group III was significantly lower than any of the other groups. The surface energy significantly increased as the treatment temperature increased, especially in group III. In the 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay, after 24 hours of incubation, the assessment of cell viability showed that the optical density of the control had a higher tendency than any other group, but there was no significant difference. However, the alkaline phosphatase activity increased as the temperature increased, especially in group III. CONCLUSIONS: Consequently, the surface characteristics and biocompatibility increased as the temperature increased. This indicates that surface modification by thermal treatment could be another useful method for medical and dental implants.

Herramientas para el diseño de las condiciones del proceso de secado por aspersión de extractos vegetales para uso farmacéutico / Design tools for vegetable extract spray drying processes for pharmaceutical use

INTRODUCCIÓN: para la obtención en forma de polvo de los extractos y jugos de origen vegetal se emplea el secado por aspersión, porque es un método que preserva los componentes naturales presentes en estos productos. La presencia de compuestos como los azúcares impiden que estos puedan ser secados por aspersión sin que se adhieran a las superficies internas del equipo, lo que trae como consecuencia el bajo rendimiento en la recuperación del producto. El uso de aditivos inertes como el almidón soluble, celulosa o maltodextrina, favorece la recuperación del producto, elevando la temperatura de transición vítrea. OBJETIVOS: aplicar herramientas para el diseño del proceso de secado por aspersión de extractos de plantas. MÉTODOS: se determinaron las temperaturas de transición vítrea de diferentes extractos por calorimetría de barrido diferencial. Se calcularon las temperaturas de apelmazamiento y los índices individuales de secado. RESULTADOS: se determinó, que el uso de aditivos en el proceso de secado por aspersión de extractos de plantas permite obtener extractos en polvo en aquellos casos que no es posible secarlos solos. La metodología empleada, puede ser aplicada a distintos extractos. CONCLUSIONES: se demostró la factibilidad de la metodología propuesta como herramienta para definir la concentración de coadyuvante del secado y las temperaturas de secado

INTRODUCTION: to obtain extracts and juices of vegetal origin as powders, it is necessary to use the spray drying because this method preserves the natural compounds present in these products. Compounds like sugars prevent them from being spray dried without sticking to the inner surfaces of the dryer, all of which results in poor product recovery. The use of inert additives as soluble starch, cellulose or maltodextrin, favors the product recovery by increasing the glass transition temperature. OBJECTIVES: to use design tools for plant extract spray drying process. METHODS: the glass transition temperature was estimated for different extracts by differential scanning calorimetry. Sticking temperature as well as individual drying indexes were calculated. RESULTS: it was demonstrated that the use of additives in plant extract spray drying processes allows obtaining powdered extracts when it is not possible to dry the extract alone. This methodology can be applied to various extracts. CONCLUSIONS: the feasibility of the submitted methodology as a tool for defining adjuvant concentration and drying temperatures was shown

Use of glass transition temperature for stabilization of board's cracks of Eucalyptus grandis

The Eucalyptus grandis logs temperatures were determined and correlated with the board's cracks during steaming. Thermocouples were inserted in the logs center, registering their temperatures during steaming at 90"C. The logs were sawed and the board's cracks measured. It was concluded that: (1) the logistic S-shaped curve explains the logs temperature variation; (2) the logs with diameter of 20 to <25, 25 to <30 and 30 to <35 cm presented, respectively, 84.2"C, 73.1"C and 45.8"C in the steaming; and (3) the cracks lengths significantly decreased in logs that reached the glass transition temperature.

As temperaturas em toras de Eucalyptus grandis, durante a vaporização, foram determinadas e correlacionadas com as rachaduras das tábuas. Nos centros das toras foram inseridos termopares e registradas suas temperaturas durante a vaporização à 90"C. As toras foram desdobradas e as rachaduras das tábuas mensuradas. Concluiu-se que: (1) o modelo estatístico sigmoidal logístico explica a variação da temperatura nas toras; (2) as toras com 20 a <25, 25 a <30 e 30 a <35 cm de diâmetro apresentaram, respectivamente, 84,2"C, 73,1"C e 45,8"C ao final da vaporização; e (3) as rachaduras foramsignificativamente menores nas toras que atingiram a temperatura de transição vítrea.

Comparison of transition temperature range and phase transformation behavior of nickel-titanium wires / 대한치과교정학회지

OBJECTIVE: The aim of this research was to evaluate the mechanical properties (MP) and degree of the phase transformation (PT) of martensitic (M-NiTi), austenitic (A-NiTi) and thermodynamic nickel-titanium wire (T-NiTi). METHODS: The samples consisted of 0.016 x 0.022 inch M-NiTi (Nitinol Classic, NC), A-NiTi (Optimalloy, OPTI) and T-NiTi (Neo-Sentalloy, NEO). Differential scanning calorimetry (DSC), three-point bending test, X-ray diffraction (XRD), and microstructure examination were used. Statistical evaluation was undertaken using ANOVA test. RESULTS: In DSC analysis, OPTI and NEO showed two peaks in the heating curves and one peak in the cooling curves. However, NC revealed one single broad and weak peak in the heating and cooling curves. Austenite finishing (Af) temperatures were 19.7degrees C for OPTI, 24.6degrees C for NEO and 52.4degrees C for NC. In the three-point bending test, residual deflection was observed for NC, OPTI and NEO. The load ranges of NC and OPTI were broader and higher than NEO. XRD and microstructure analyses showed that OPTI and NEO had a mixture of martensite and austenite at temperatures below Martensite finishing (Mf). NEO and OPTI showed improved MP and PT behavior than NC. CONCLUSIONS: The mechanical and thermal behaviors of NiTi wire cannot be completely explained by the expected degree of PT because of complicated martensite variants and independent PT induced by heat and stress.

Glass transition and degree of conversion of a light-cured orthodontic composite

OBJECTIVE: This study evaluated the glass transition temperature (Tg) and degree of conversion (DC) of a light-cured (Fill Magic) versus a chemically cured (Concise) orthodontic composite. MATERIAL AND METHODS: Anelastic relaxation spectroscopy was used for the first time to determine the Tg of a dental composite, while the DC was evaluated by infrared spectroscopy. The light-cured composite specimens were irradiated with a commercial LED light-curing unit using different exposure times (40, 90 and 120 s). RESULTS: Fill Magic presented lower Tg than Concise (35-84ºC versus 135ºC), but reached a higher DC. CONCLUSIONS: The results of this study suggest that Fill Magic has lower Tg than Concise due to its higher organic phase content, and that when this light-cured composite is used to bond orthodontic brackets, a minimum energy density of 7.8 J/cm² is necessary to reach adequate conversion level and obtain satisfactory adhesion.

Efeito da irradiação por microondas sobre as propriedades viscoelásticas de resinas para base de prótese e reembasamento / Effect of microwave irradiation on the viscoelastic properties of denture base and reline acrylic resins

Este estudo avaliou o efeito da irradiação por microondas e da armazenagem em água sobre as propriedades viscoelásticas de duas resinas para base de prótese (Lucitone 550- L e Vipi Wave- VW) e duas resinas para reembasamento imediato (Kooliner- K e Tokuyama Rebase Fast II- TR II). Oito corpos-de-prova (40 x 10 x 3,3 mm) de cada material foram avaliados por meio de análise térmica dinâmico-mecânica (DMTA) após: acabamento (controle 1), armazenagem em água por 7 dias (controle 2), um (MW1) e 7 ciclos de irradiação por microondas (MW7). Para cada corpo-de-prova, ciclos de DMTA foram realizados dentro de intervalos de temperatura diferentes. Os valores do módulo de armazenamento (E') e de amortecimento mecânico (tan ) a 37ºC foram obtidos no primeiro e último ciclos de DMTA. A partir do último ciclo, os valores de E' na temperatura de transição vítrea (Tg) e o máximo de tan também foram obtidos. Os dados foram submetidos à análise de variância a dois critérios e ao teste de Student-Newman-Keuls (=0,05). Além disso, mensurações de temperatura no interior de corpos-de-prova de cada material, durante a irradiação por microondas (650 W/ 3 min), foram realizadas por meio da utilização de sensor de fibra óptica. Seis corpos-de-prova de cada material foram avaliados. Durante a irradiação por microondas, todos os corpos-de-prova atingiram a temperatura de ebulição da água em aproximadamente 130 s. A partir do primeiro ciclo de DMTA, MW 1 e controle 2 aumentaram significantemente os valores de E' e reduziram os valores de tan de K a 37ºC (P<0,05). No último ciclo de DMTA, o tan de K e TR II foi significantemente reduzido após MW1 (P<0,05). MW7 reduziu os valores de tan de K (P<0,05). Os valores de E' de L e VW foram semelhantes entre si e superiores aqueles produzidos por K e TR II (P<0,05). Na Tg, K produziu o menor E' e seu máximo de tan foi aumentado após MW1 (P<0,05). Os valores médios da Tg foram ordenados como: L>VW>TR II>K (P<0.05). A irradiação por microondas e a armazenagem em água não comprometeram as propriedades viscoelásticas das resinas para base de prótese e reembasamento

This study evaluated the effect of microwave irradiation and water storage on the viscoelastic properties of two denture base resins (Lucitone 550-L and Vipi Wave-VW) and two reline resins (Kooliner-K and Tokuyama Rebase Fast II-TR II). Eight specimens (40x10x3.3mm) of each material were evaluated by dynamic mechanical thermal analysis (DMTA) after: processing, water storage for 7 days (WS), one (MW1) and 7 cycles of microwave irradiation (MW7). For each specimen, DMTA runs were carried out within different temperature intervals. Values of storage modulus (E') and loss tangent (tan ) at 37ºC were obtained from the first and last runs. From the last run, values of E' at the glass transition temperature (Tg) and maximum tan were also recorded. Data were analyzed by 2-way ANOVA followed by Student-Newman-Keuls test (=0.05). In addition, measurements of the inside temperature of each specimen during microwave irradiation (650W/3min) were conducted using a fiber optic temperature sensor. Six specimens of each material were evaluated. During microwave irradiation, all specimens reached the boiling temperature of water at approximately 130 s. From the first DMTA run, MW1 and WS significantly increased the E' and decreased the tan of K at 37°C (P<0.05). From the last run, the tan of K and TR II was significantly decreased after MW1 (P<0.05). MW7 decreased the tan of K (P<0.05). The E' of L and VW was similar and higher than K and TR II (P<0.05). At Tg, K produced the lowest E' and its maximum tan was increased after MW1 (P<0.05). The Tg mean values were arranged as: L>VW>TR II>K (P<0.05). Microwave irradiation and WS did not detrimentally affect the viscoelastic properties of the denture base and reline resins evaluated

Polimerización ee ácido (dl) láctico mediante plicondensación por fusión direccta. estudio cinético de la etapa de oligomerización / Polymerizatio off dl lactic aid by direct melt polycondensation. kinetics sttudy of oligomerizatio stage

La reacción de polimerización del ácido láctico por el mecanismo de policondensación por fusión directa es de gran importancia cuando se desean obtener polímeros de bajo peso molecular, principalmente para aplicaciones médicas, debido a la facilidad del proceso y el bajo costo. Un ejemplo de esto es la elaboración de dispositivos para la liberación controlada de medicamentos. En este trabajo se estudiaron las diferentes etapas que involucra la policondensación (oligomerización y polimerización) para obtener PAL. La etapa de oligomerización se estudió en un estrecho intervalo de temperatura, 100-150 °C, donde el modelo cinético que describe la reacción es una ley de potencias de orden tres con Ea y factor preexponencial de 22,7 kcal/mol °K y 3,28x10-7 L²/mol²h respectivamente. Para la etapa de polimerización se estudiaron la influencia de la temperatura, el porcentaje de catalizador (SnCl2 2H2O) y el tiempo de reacción tomando como variable de respuesta la temperatur a de transición vítrea.

The polymerization reaction of d,1-lactic acid through polycondensation by direct melting is very important when low molecular weight polymers are desired, mainly for biomedical uses due to the easiness and low cost of process. And example of this is the manufacture of controlled delivery devices for drugs. In this work the steps involved on the polycondensation (oligomerization and polymerization) to obtain PLA were studied. The oligomerization was studied in a narrow range of temperatures 100-150°C where the kinetics model that describes the reaction is a kinetic law of powers of third order, with Ea and preexponential factor at 298.15K being 22,7 kcal/molK and 3.28x10-7 L²/mol²h respectively. For the polymerization step was studied the influence of temperature, the catalyst ratio (SnCL2.2H2O) and the time of reaction at the glassy transition temperature.

PHONON-EXCITON MECHANISM IN YBa2Cu3O7-δ SYSTEM / 药物分析学报

In this paper, based on the phonon-exciton mechanism, the superconductivity of yttrium barium copper oxide (YBCO) system is explained. The transition temperature (Tc) 's formula is derived by the extended BCS-Eliashberg theory, i.e. phonon-exciton mechanism and McMillan's energy gap function, and the Tc's expressions isreduced by using the Einstein spectrum. Last, the calculating method of element metal effective phonon spectrum is used to the high Tc cuprate YBCO system by using a crystal average atom approximation model. The theoretical analysis and calculational results show that the superconductivity of high Tc YBCO system maybe described by phonon-exciton model.

Preparation and evaluation of pilocarpine nitrate in situ gel for ophthalmic use / 中草药

Objective To develop and charaterize a series of Poloxamer-and Carbopol-based in situ gel for ophthalmic use as to enhance the ability of drug to retain in eyes and delay drug release.Methods The gel was prepared using Poloxamer 407/188 and Carbopol 974P as gelling agent and viscosity enhancer,respectively.Rheological characteristics were evaluated and behaviour of drug release in vitro was investigated by modified Franz diffusion cells.Results The rheological study indicated that the gel was physically entangled polymer solutions at 20 ℃ and then converted into a network structure with secondary bonds at 35 ℃.The gel released the drug molecules slowly in 4 h.The best fit model was Higuchi matrix model(r=0.992 3).Formulations consisting of Poloxamer 188 and Carbopol 974P were proved to be able to decrease the drug release speed efficiently.The impact on elastic modulus G" of the gel caused by those two were different.Conclusion An in situ gel with suitable sol-gel transition temperature and satisfactory release pattern could be achieved by adjusting the ratio of Poloxamer 407 to Poloxamer 188.The developed formulations have the ability to prolong the ocular residence time,which suggests it may be a new durg delivery system with bright future.