Abstract Poly(vinylidene fluoride) (PVDF) and PVDF blends with various molecular weights of poly (N- vinylpyrrolidone) (PVP) films were prepared in dimethyl formamide through the solution casting method. Non-isothermal melt crystallization studies of PVDF films were carried out by cooling the molten samples at different temperatures using differential scanning calorimetry (DSC). The obtained films have been characterized by dynamic mechanical thermal analysis (DMTA). Crystallization kinetics of PVDF films were successfully described by the Jeziorney, Mo and Ziabicki models. The Ozawa equation was found to be invalid for describing the crystallization kinetics. Kinetic parameters such as t1/2, Zc and F(T) indicated that the crystallization rate decreased for PVDF/PVP films as compared to neat PVDF films and was affected by the molecular weight of PVP. The results based on Ziabicki's model revealed that the addition of PVP decreased the ability of PVDF to crystallize under non-isothermal melt crystallization conditions. The activation energy was calculated through Friedman and advanced isoconversional methods. Results showed that the addition of PVP to PVDF films caused an increase in activation energy. By comparing DMTA results of PVDF/PVP blends with neat PVDF films, it could be concluded that blending PVDF with PVP caused an increase in the glass transition temperature (Tg) while the storage modulus was decreased.

Se sintetizaron algunas bases de Schiff a partir de pirazol y 4-amino antipirina. La evaluación de la actividad antibacteriana de estos compuestos en dimetil formamida se realizó frente a cuatro bacterias Gram positivas, Bacillus cereus, Staphylococcus aureus, Staphylococcus epidermidids y Micrococcus luteus, y frente a tres bacterias Gram negativas, Proteus mirabilis, Escherichia coli y Klebsiella aerogenes. Se observó mejor inhibición bacteriana frente a las diferentes cepas para las bases de Schiff basadas en pirazol comparadas con aquellas basadas en 4-amino antipirina.

Some Schiff bases of pyrazole and 4-amino antipyrine have been synthesized. The antibacterial screening of these synthesized compounds was done in dimethyl forma-mide against four Gram positive bacteria viz. Bacillus cereus, Staphylococcus aureus, Staphylococcus epidermidids and Micrococcus luteus, and three Gram negative bacteria viz. Proteus mirabilis, Escherichia coli and Klebsiella aerogenes. It is observed that in comparison to Schiff bases of 4-amino antipyrine, pyrazole Schiff bases are better for inhibition for these selected Gram positive and Gram negative bacterial strains.

Dihydropyrimidinthione is an important class of heterocyclic compounds which exhibits wide spectrum of biological activities. In the present study, some bio-active dihydropyrimidinthione derivatives have been synthesized and their characterization was done by IR, NMR and mass spectral data. The antibacterial and antifungal activities of synthesized compounds have also been studied in N,N-dimethyl formamide and Dimethyl sulfoxide

Este trabalho apresenta um novo sensor químico óptico, simples e de baixo custo, para a determinação de íon mercúrio (II) em solução aquosa. A membrana sensível a mercúrio foi preparada pela incorporação de triazina ((E)-1-(2-etoxifenil)-3-(4-nitrofenil) triazol-1-ene como um ligante adequado para Hg(II) sobre uma membrana de triacetilcelulose. O estudo espectrofotométrico do complexo formado entre o ligante triazene (L) e íons Hg2+ em solução de dimetilformamida (DMF) mostrou uma grande constante de estabilidade para o íon mercúrio complexado. A membrana responde ao íon mercúrio pela troca reversível da cor de laranja para verde em solução tamponada em pH 3,0. Uma relação linear foi observada entre a absorbância da membrana em 405 nm, na faixa de 7 a 90 µg mL-1, com um limite de detecção de 64 ng mL-1 em soluções aquosas, em pH 3,0. O sensor óptico for aplicado com sucesso na determinação de mercúrio em amostras de água enriquecidas com o analito.

A new simple and inexpensive optical chemical sensor for mercury(II) ion in aqueous solutions is presented. The mercury sensing membrane was prepared by incorporating of triazene ((E)-1-(2-ethoxyphenyl)-3-(4-nitrophenyl) triaze-1-ene) (L) as a suitable ligand for Hg(II) on triacetylcellulose membrane. Spectrophotometric study of complex formation between the triazene ligand L and Hg2+ in dimethyl formamide solution indicated a large stability constant for the mercury ion complex. The membrane responds to mercury ion by changing color reversibly from orange to green in buffer solution at pH 3.0. A linear relationship was observed between the membrane absorbance at 405 nm in a range from 7 to 90 µg mL-1 with a limit of detection of 64 ng mL-1 in aqueous solutions at pH 3.0. The optical sensor was successfully applied to the determination of mercury in spiked water samples.

Ultrasonic velocities and density of various concentrations (0.01 to 0.10M) of anti protozoal drog "Diloxanide Furoate" in methanol, dimethyl formamide and 1,4-dioxan have been measured at 308.15 K by using single crystal variable path ultrasonic interferometer operating at 2 MHz and pycnometer respectively. Using these experimental data, some acoustical parameters have been evaluated and they are interpreted in terms of solute-solute and solute-solvent interactions in these solutions

Resumen. La criopreservación de semen es un proceso fundamental en el desarrollo de biotecnologías para la reproducción asistida en equinos. El uso de diferentes técnicas de criopreservación con cambios en las concentraciones y la naturaleza de los crioprotectores, así como en los diferentes tipos de soportes para el almacenamiento del semen, se ha constituido en una alternativa para mejorar los protocolos empleados. El objetivo de este trabajo fue evaluar el efecto de dos protocolos de criopreservación (congelación y vitrificación), sobre la capacidad fecundante del semen equino. El estudio se realizó con equinos de la raza Criollo Colombiano. Para la congelación se empleó un diluyente suplementado con de yema de huevo (4%) y dimetilformamida (5%), y pajillas de 0,5 mL como soportes; mientras que para la vitrificación, el diluyente fue suplementado con yema de huevo (8%) y dimetilformamida (8%) y se usaron crioviales como soportes. Post-descongelación, se evaluaron los parámetros: movilidad progresiva, vitalidad, morfología normal e integridad de la membrana plasmática (HOS). Para la evaluación estadística se ajustó un modelo lineal generalizado (GLM) y las medias se compararon por la prueba de Tukey. Se encontraron porcentajes promedio de movilidad progresiva, vitalidad, morfología normal y HOS de 41,6±11,8 y 37,0±8,5, 54,3±10,2 y 52,3±7,8, 83,1±5,4 y 83,6±5,8, 41,7±9,8 y 38,9±3,6, para el semen criopreservado por congelación y vitrificación, respectivamente. No se encontraron diferencias estadísticamente significativas (P ≤ 0,05) entre los tratamientos para ninguno de los parámetros evaluados. La capacidad fecundante del semen equino criopreservado por vitrificación es equiparable a la obtenida por congelación convencional.

Abstract. Semen cryopreservation is a fundamental process for the development of biotechnologies for assisted reproduction in horses. The use of cryopreservation techniques with changes in concentrations and the nature of the cryoprotectant, as well as, the different types of vials for storage of semen, have become an alternative to improve the protocols used. The objective of this work was to evaluate the effect of two protocols of cryopreservation (freezing and vitrification) on the fertilizing capacity of stallion semen. The study was conducted with horses of the Criollo Colombiano breed. For freezing was used a extender supplemented with egg yolk (4%) and dimethyl formamide (5%), and 0.5 mL straws as vials, whereas for vitrification, the extender was supplemented with egg yolk (8%) and dimethyl formamide (8%), and cryovials were used as carriers. As post thaw parameters were evaluated: progressive motility, vitality, normal morphology and integrity of the plasma membrane through the hypoosmotic swelling test (HOS). For statistical evaluation was fitted a generalized linear model (GLM) and means were compared by the Tukey test. Were found average percentages of progressive motility, vitality, normal morphology and HOS of 41.6 ± 11.8 and 37 ± 8.5, 54.3 ± 10.2 and 52.3 ± 7.8, 83.1 ± 5.4 and 83.6 ± 5.8, 41.7 ± 9.8 and 38.9 ± 3.6, for cryopreserved semen by freezing and vitrification, respectively. There were no statistically significant differences (P ≤ 0.05) between treatments for any of the parameters evaluated. The fertilizing capacity of equine semen cryopreserved by vitrification is comparable to that obtained by conventional freezing.

Objetivo. Evaluar el efecto del colesterol y la dimetilformamida (DMF) sobre la criosupervivencia del semen de caballos criollos colombianos. Materiales y métodos. Se recolectó semen de diez caballos y se congeló bajo el mismo protocolo, con variaciones del crioprotector (glicerol 5% o DMF 5%) y la adición o ausencia de colesterol como modificador de membrana (1.5 mg ciclodextrinas con colesterol por cada 120 x 10(6) células). La criosupervivencia se evaluó estimando movilidad mediante el software SCA. La vitalidad e integridad de membrana posdescongelación se estimó usando eosina-nigrosina y test hipo-osmótico respectivamente. Resultados. Incubar el semen con el colesterol, tuvo un aumento significativo del porcentaje de movilidad total y progresiva, en la velocidad de los espermatozoides y el porcentaje de espermatozoides rápidos y una disminución del porcentaje de espermatozoides con movilidad lenta. Adicionalmente se incrementó el porcentaje de espermatozoides vivos y con integridad de membrana (p<0.05). La DMF como agente crioprotector, mejoró todos los parametros evaluados al ser comparada el glicerol (p<0.05). Conclusiones. Ambos procedimientos mejoraron los parámetros evaluados debido a efectos aditivos del crioprotector y del modificador de membrana, pero no hubo interacción entre estos dos factores.

Objective. To evaluate the effect of cholesterol and dimethyl formamide on the cryosurvival of colombian creole stallion sperm. Materials and methods. Semen from ten stallions was collected and frozen using the same protocol, with variations in the cryoprotectant (glycerol 5% or 5% DMF) and the addition or absence of cholesterol as membrane modifier (1.5 mg cholesterol loaded cyclodextrins for each 120 x 10Z6 cells). The cryosurvival was evaluated by estimating motility using the SCA software. The vitality and membrane integrity was estimated using eosin nigrosine staining and by hypo-osmotic test respectively. Results. Sperm incubated with cholesterol had a significant effect in improving the percentage of total motility, progressive motility, sperm velocity and percentage of rapid sperm along with a decreased percentage of sperm with slow motility. Additionally, there was an improvement in the percentage of live spermatozoa and spermatozoa with membrane integrity (p<0.05). Dimethyl formamide (DMF) as a cryoprotectant, improved all the evaluated parameters in comparison with glycerol (p<0.05). Conclusions. Both procedures improved the evaluated parameters due to the additive effects of the cryoprotectant and the membrane modifier, but there was no interaction between these two factors.

Nitrate is quantitatively retained with 2,6-bis(4-methoxyphenyl)-4-phenyl pyrylium perchlorate (PPP) on microcrystalline naphthalene in the pH range of 6.5-9.0 from a large volume of aqueous solutions of various samples. The method was based on the complexation between PPP and nitrate and then, extraction of the resulted complex from aqueous solution by microcrystalline naphthalene. The solid mass consisting of the nitrate complex and naphthalene was then dissolved in dimethyl formamide (DMF) and absorption of the resulted solution was obtained at 328 nm. The linear calibration range for the determination of nitrate was 15-135 μg L-1 with the detection limit of 10 μg L-1.

Density, ultrasonic velocity and viscosity of Schiff bases have been studied in dimethyl formamide at 308.15 K. From the experimental data, various acoustical parameters such as specific Impedance (Z), isentropic compressibility (?s), Rao's molar sound function (Rm), Van der Waals constant (b), relaxation strength (r), intermolecular free length (Lf), internal pressure (p), solvation number (Sn) etc. have been evaluated, which helps in understanding the molecular interactions occurring in these solutions.

Cinco novas poliamidas-iminas (PAIs) oticamente ativas 6a-e foram preparadas pela reação de policondensação direta da N,N´-(biciclo[2,2,2]octa-7-eno-2,3,5,6-tetracarboxila)-bis-L-alanina 4 com várias diaminas aromáticas 5a-e usando solventes polares apróticos como a N-metil-2-pirrolidona (NMP). Neste procedimento, trifenil fosfito (TPP) e piridina foram usados como agentes de condensação para formar poliamidas-imidas através dos sais de N-fosfônio-piridina. Todos os polímeros foram obtidos com rendimentos quantitativos com uma viscosidade intrínseca entre 0,29-0,46 dL g-1, sendo altamente solúveis em solventes polares apróticos como N,N-dimetil acetamida (DMAc), N,N-dimetilformamida (DMF), dimetil sulfóxido (DMSO), N-metil-2-pirrolidona (NMP) e ainda em solventes como o ácido sulfúrico. Os compostos foram caracterizados por espectroscopia de RMN ¹H, espectroscopia no infravermelho, análise elementar, viscosidade intrínseca, testes de solubilidade, rotação específica e as propriedades térmicas desses polímeros foram investigadas usando técnicas termogravimétricas de análise (TGA e DTG).

Five new optically active poly(amide-imide)s (PAIs) 6a-e were prepared by direct polycondensation reaction of the newly synthesized N,N´-(bicyclo[2,2,2]oct-7-ene-2,3,5,6-tetra carboxylic)-bis-L-alanine 4 with various aromatic diamines 5a-e using polar aprotic solvents such as N-methyl-2-pyrrolidone (NMP). In this technique triphenyl phosphite (TPP) and pyridine were used as condensing agents to form poly(amide-imide)s through the N-phosphonium salts of pyridine. All of the polymers were obtained in quantitative yields with inherent viscosities between 0.29-0.46 dL g-1 and were highly soluble in polar aprotic solvents such as N,N-dimethyl acetamide (DMAc), N,N-dimethyl formamide (DMF), dimethyl sulfoxide (DMSO), N-methyl-2-pyrrolidone (NMP) and solvents such as sulfuric acid. They were fully characterized by means of ¹H NMR, FTIR spectroscopy, elemental analyses, inherent viscosity, solubility test, specific rotation and thermal properties of these polymers were investigated using thermogravimetric analysis techniques (TGA and DTG).

A rapid, simple, sensitive and selective spectrophotometric method is developed for the determination of molybdenum (VI) in aqueous dimethyl formamide (DMF). Molybdenum (VI) forms a yellow coloured complex with 2-hydroxy-3-methoxy benzaldehyde thiosemicarbazone in the pH range 1.0-6.0. The complex shows maximum absorbance at 375nm and in the pH range 1.0-2.0. However, at this wave length, the reagent shows considerable absorbance. At 385nm, the complex shows large absorbance while the reagent blank shows negligible absorbance. Hence, analytical studies are carried out at 385nm and at pH 1.5 against reagent blank. Beer's law is obeyed in the range 0.24-4.32 µg ml-1. The molar absorptivity and Sandell's sensitivity forthe coloured solution are found to be 2.3 x 10-4 1 mol-1 cm-1 and 0.0042 µg cm-2 respectively. The interference effect of various diverse ions has been studied. The complex shows 1:1 [Mo (VI): HMBATSC] stoichiometry with a stability constant 2.35 x 10(6). The standard deviation of the method in the determination of 2.396 µg ml-1 of Mo(VI) is calculated as ± 0.0012. A second order derivative spectroscopic method is developed for the determination of molybdenum(VI), which is more sensitive than the zero order method.. The developed method has been employed for the determination of molybdenum (VI) in food stuffs and in alloy steels. The results are in excellent agreement with the certified values

Avaliou-se a eficácia de três diluidores, tris-gema com 5% de etileno glycol (T1), lactose-gema com 5% de etileno glicol (T2) e lactose-gema com 5% de dimetil-formamida (T3) na criopreservação do sêmen de cães. Foram obtidos três ejaculados por cão de um total de cinco animais. O sêmen foi envasado em palhetas de 0,5ml e resfriado até 4°C por 120min. As palhetas foram congeladas 4cm acima do nitrogênio líquido por 15min e descongeladas em banho-maria a 37°C por 60seg e 75°C por 7seg. A motilidade progressiva e o vigor foram avaliados imediatamente após a descongelação (tempo 0) e aos 30, 60, 90 e 120min. A integridade estrutural e funcional da membrana plasmática do espermatozóide foi avaliada, respectivamente, por meio da coloração de fluorescência e pelo teste hiposmótico. Os diluidores à base de lactose gema foram mais eficazes em preservar a viabilidade espermática pós-descongelação e a dimetil-formamida é um crioprotetor eficaz para espermatozóides de cães.

The efficacy of three extenders, tris-egg yolk-5% ethylene glycol (T1), lactose-egg yolk-5% ethylene glycol (T2) and lactose-egg yolk-5% dimethyl formamide (T3) on preserving the viability of post-thawing canine spermatozoa was evaluated. Three ejaculates per dog were obtained of five animals. The semen was packaged in 0.5ml straws and cooled to 4°C for 120min. The straws were frozen 4cm above the nitrogen level for 15min and thawed in water-bath at 37°C for 60sec and at 75°C for 7sec. Progressive motility and vigour were evaluated immediately after thawing (time 0) and at 30, 60, 90 and 120min. Structural and functional integrity of plasma membrane of the spermatozoa were evaluated, respectively, by fluorescent staining probes and hypoosmotic swelling test. Lactose-egg yolk based extenders showed better cryoprotectant capability and dimethyl formamide was an alternative cryoprotectant agent for dog sperm cells.

Foi desenvolvido um método altamente sensível, seletivo e rápido para a determinação de mercúrio, a partir da reação rápida de mercúrio(II) com 5-(p-aminobenzilideno)-tiorodanina (ABTR) e posterior extração em fase sólida do quelato colorido, utilizando discos C18. Em pH 3,5 e na presença do emulsificante-OP, ABTR reage com mercúrio(II) para formar um quelato vermelho na razão molar 1:2 (mercúrio:ABTR). O quelato foi enriquecido pela extração em fase sólida com discos C18 e o quelato retido, eluído com dimethyl formamida (DMF). Um fator de enriquecimento na ordem de 50 foi obtido. Em DMF, a absortividade molar do quelato é 1,21<FONT FACE=Symbol>´</FONT>10(5) L mol-1 cm-1 a 545 nm, e a lei de Beer é obedecida no intervalo 0,01~3 µg mL-1 na solução medida. O desvio padrão relativo para onze replicatas a 0,01 µg mL-1 é 1,7%. Este método foi aplicado para a determinação de mercúrio em tabaco e aditivos de tabaco. Bom coeficiente de preconcentração foi encontrado, comparando-se o método proposto com outros similares.

A highly sensitive, selective and rapid method for the determination of mercury based on the rapid reaction of mercury(II) with 5-(p-aminobenzylidene)-thiorhodanine (ABTR) and the solid phase extraction of the colored chelate with C18 disks has been developed. At pH 3.5 and in the presence of emulsifier-OP medium, ABTR reacts with mercury(II) to form a red chelate of a 1:2 (mercury to ABTR) molar ratio. This chelate was enriched by solid phase extraction with C18 disks and the retained chelate eluted form the disks with dimethyl formamide (DMF). An enrichment factor of 50 was achieved. In the DMF medium, the molar absorptivity of the chelate is 1.21<FONT FACE=Symbol>´</FONT>10(5) L mol-1 cm-1 at 545 nm, and Beer's law is obeyed in the 0.01~3 µg mL-1 range in the measured solution. The relative standard deviation for eleven sample replicate measurements at the 0.01 µg mL-1 level is 1.7%. This method was applied to the determination of mercury in tobacco and tobacco additives and good preconcentration was found between proposed and comparative methods results.

O objetivo neste trabalho foi avaliar os efeitos da dimetil-formamida na criopreservação de sêmen caprino, por meio de testes in vitro. As partidas de sêmen foram congeladas com os diluidores leite desnatado-gema, associado a diferentes crioprotetores e concentrações: 7% de glicerol (T1); 3,5% de glicerol e 3,5% de dimetil-formamida (T2) e 5% de dimetil-formamida (T3). O sêmen foi centrifugado e envasado em palhetas de 0,5 mL, sendo resfriado por 40 minutos, atingindo 5,0°C e permanecendo nesta temperatura por mais 1 hora e 20 minutos. Os parâmetros avaliados in vitro foram a motilidade progressiva e o vigor espermático, a integridade acrossômica, a integridade da membrana plasmática (HO) e a reação acrossômica. Observou-se perda de 30,0% da motilidade inicial quando as amostras foram submetidas aos procedimentos de criopreservação. A perda de integridade da membrana plasmática, avaliada pelo teste hiposmótico (HO) foi de 19%. As lesões de acrossoma aumentaram em 3% durante o teste de termo-resistência (TTR) lento. Não houve diferença entre os tratamentos quanto aos aspectos de motilidade nos tempos de 0,00; 0,05; e 1,00 horas do TTR e vigor em todos os tempos. No tempo de 2,00 horas do TTR, registrou-se diferença entre os tratamentos 1 e 2, de modo que a motilidade no tratamento 2 foi superior às demais. Os valores de integridade de membrana plasmática, integridade acrossômica e reação acrossômica pós-descongelamento não diferiram entre os tratamentos, indicando que a dimetil-formamida não foi superior ao glicerol na manutenção da qualidade espermática após a criopreservação.

The objective of this trial was to evaluate the efficiency of dimethylformamide on cryopreservation of goat semen using semen physical analyses and complementary tests. Alpine and Saanen bucks from the Dairy Goat Experimental Station- DZO were used. Semen samples were frozen with a yolk-skimmed milk diluent and cryoprotectors with different concentrations as follows: 7% glycerol (T1), 3.5% glycerol plus 3.5% dimethylformamide (T2) or 5% dimethylformamide (T3). Semen was centrifuged, diluted, and bottled in 0.5 mL straws followed by cooling for 40 minutes until reach 5.0°C and kept at this temperature for additional 80 minutes. Samples were then exposed to liquid nitrogen vapor for 15 minutes and finally frozen. Thawing was done in a waterbath at 37°C for 50 seconds. The following variables were evaluated in vitro: sperm progressive motility and vigor, acrosomal integrity and reaction, and plasmatic membrane integrity. The cryopreservation procedures reduced 30.0% of the initial motility and 19% of plasmatic membrane integrity that was evaluated using the hyposmotic swelling test (HOST). It was observed an increaseof 3% in acrosomal lesions when samples were submitted to a slow thermoresistance test (TRT). No significant differences in sperm motility were observed among treatments at 0, 5, and 60 minutes of TRT as well as in sperm vigor at all TRT times. However, at 120 minutes of TRT a significant difference in sperm motility was found comparing T1 and T2 while T3 was intermediate. There were no significant differences on plasmatic membrane integrity, acrosomal integrity, and post-thawing acrossomal reaction across treatments. It can be concluded that dimethylformamide can be a viable alternative for goat semen cryopreservation used alone or in association with glycerol.