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1.
Environ Technol ; 35(1-4): 36-41, 2014.
Artículo en Inglés | MEDLINE | ID: mdl-24600838

RESUMEN

In this paper, the effect of urea-hydrogen peroxide (UHP) solution on desulphurization and demineralization of coal with high sulphur and high ash by using HNO3 and microwave pretreatment was investigated. The oxidation process is strongly dependent on irradiation power and time for microwave pretreatment, UHP concentration, leaching time and temperature of the UHP solution. X-ray diffraction and Fourier transform infrared technique have been performed for the raw and treated coals. Compared with the UHP alone, successive treatments with HNO3 and microwave pretreatment resulted in the significant removal of total sulphur and mineral matter from the coal. The proposed experimental method has the meaning of practical guide to the desulphurization and deashing of coal by microwave.


Asunto(s)
Ceniza del Carbón/aislamiento & purificación , Carbón Mineral/análisis , Carbón Mineral/efectos de la radiación , Peróxido de Hidrógeno/química , Ácido Nítrico/química , Compuestos de Azufre/aislamiento & purificación , Urea/química , Ceniza del Carbón/química , Ceniza del Carbón/efectos de la radiación , Peróxido de Hidrógeno/efectos de la radiación , Microondas , Ácido Nítrico/efectos de la radiación , Oxidación-Reducción/efectos de la radiación , Dosis de Radiación , Compuestos de Azufre/química , Compuestos de Azufre/efectos de la radiación , Urea/efectos de la radiación
2.
J Environ Sci (China) ; 26(12): 2406-11, 2014 Dec 01.
Artículo en Inglés | MEDLINE | ID: mdl-25499488

RESUMEN

Diisopropylthiourea (DPT), an intermediate of a widely used cephalosporin, has been found to be one of the most refractory components in cephalosporin synthesis wastewater. This compound cannot be completely removed by conventional biological processes due to its antimicrobial property. Ionizing radiation has been applied in the decomposition of refractory pollutants in recent years and has proved effective. Therefore, the decomposition of DPT by γ-irradiation was studied. The compound was irradiated at the dose of 150-2000 Gy before a change of concentration and UV absorption of the solutions was detected. Furthermore, the decomposition kinetics and radiation yield (G-value) of DPT was investigated. The results of radiation experiments on DPT-containing aqueous showed that the DPT can be effectively degraded by γ-radiation. DPT concentration decreased with increasing absorbed doses. G-values of radiolytic decomposition for DPT (20 mg/L) were 1.04 and 0.47 for absorbed doses of 150 and 2000 Gy, respectively. The initial concentration and pH of the solutions affected the degradation. As the concentration of substrate increased, the decomposition was reduced. The decrease of removal rate and radiation efficacy under alkaline condition suggested that lower pH values benefit the γ-induced degradation. UV absorption from 190 to 250 nm decreased after radiation while that from 250 to 300 nm increased, indicating the formation of by-products.


Asunto(s)
Urea/análogos & derivados , Urea/efectos de la radiación , Eliminación de Residuos Líquidos/métodos , Contaminantes Químicos del Agua/efectos de la radiación , Cefalosporinas/síntesis química , Rayos gamma , Concentración de Iones de Hidrógeno , Cinética
3.
J Prosthodont ; 18(3): 249-54, 2009 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-19210610

RESUMEN

PURPOSE: This study evaluated the efficacy of tooth whitening and color stability at different time periods after treatment. MATERIALS AND METHODS: Blocks obtained from human molars were divided into 15 groups (n = 5) by bleaching agents: 35% hydrogen peroxide (Whiteness HP and Opalescence Xtra) and 37% carbamide peroxide (Whiteness Super); and light sources: halogen lamp and plasma arc lamp (bleach mode), LED/diode laser, argon laser, and no light source. The efficacy of bleaching was measured using a spectrophotometer. Six bleaching sessions were performed (times 1 to 6). The specimens were submitted to another reading 7, 15, and 30 days after the end of bleaching (times 7, 8, and 9). The results were submitted to ANOVA followed by Tukey test and polynomial regression (p < 0.05). RESULTS: Carbamide peroxide significantly differed from hydrogen peroxide, presenting low reflectance values. Activated versus non-activated bleaching did not differ significantly for any gel tested, except for Whiteness HP activated by argon laser, which presented the lowest mean reflectance values. The results obtained with hydrogen peroxide revealed a decrease in reflectance values one month after the end of treatment. For carbamide peroxide, this decrease was not observed. CONCLUSION: The halogen lamp presented the same or higher efficacy than non-activated bleaching, which had a longer gel contact period. When hydrogen peroxide was used, a decrease in reflectance values was observed 30 days after the end of bleaching.


Asunto(s)
Esmalte Dental/efectos de los fármacos , Iluminación/instrumentación , Oxidantes/uso terapéutico , Blanqueamiento de Dientes/instrumentación , Peróxido de Carbamida , Color , Esmalte Dental/efectos de la radiación , Combinación de Medicamentos , Humanos , Peróxido de Hidrógeno/efectos de la radiación , Peróxido de Hidrógeno/uso terapéutico , Láseres de Excímeros/uso terapéutico , Láseres de Semiconductores/uso terapéutico , Ensayo de Materiales , Oxidantes/efectos de la radiación , Peróxidos/efectos de la radiación , Peróxidos/uso terapéutico , Espectrofotometría , Factores de Tiempo , Blanqueamiento de Dientes/métodos , Urea/análogos & derivados , Urea/efectos de la radiación , Urea/uso terapéutico
4.
Biomol Eng ; 24(1): 97-101, 2007 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-16861034

RESUMEN

In this work we address new results obtained with a thin free standing flexible film (approximately 120 microm) of a urethane/urea copolymer related to the formation of micro and nano size structures [M.H. Godinho, A.C. Trindade, J.L. Figueirinhas, L.V. Melo, P. Brogueira, Synthetic Metals, 147(1-3), 209 (2004); M.H. Godinho, A.C. Trindade, J.L. Figueirinhas, L.V. Melo, P. Brogueira, Molecular Crystals and Liquid Crystals (2005)]. The copolymer was synthesized from a polypropylene oxide-based prepolymer with three isocyanate terminal groups (PU) and polybutadienediol (PBDO) with PBDO content of 40% wt. After casting and curing the film was cut into different samples and each exposed to UV radiation for different periods of time; 23, 25, 26, 31 and 49 h (lambda=254 nm) and later extracted with toluene and dried. The dried films were then studied by polarising optical microscopy (POM), small angle light scattering (SALS) and the surfaces exposed to UV radiation analyzed by means of atomic force microscopy (AFM). Before extraction with toluene a nanometer-flat surface, characterized by a mean roughness value Ra=0.59 nm, was obtained. Depending on exposure time to UV radiation and after extraction with toluene a corrugated surface, with features mum-sized in all axes, resulting in an increase of the overall mean roughness value to Ra=50.7 nm, starts to develop after 25 h of exposure time. This work gives evidence of the non-monotonous time behavior of the wrinkled surface growth that develops under the action of ultraviolet radiation. As the exposure time increases the free-standing films directly exposed surfaces show a decreasing density of the structures observed and an increasing characteristic peak-to-valley height. The peak-to-valley height measured for samples exposed for 23, 25, 26, 31 and 49 h, respectively 193, 383, 381, 1550 and 2039 nm and the corresponding mean roughness values are Ra=50.7 nm, 105.4, 116.8, 438.3 and 515.4 nm, respectively. Between 26 and 31 h exposure time a leap in both values, peak-to-valley and Ra, was observed. The sudden increase in these values is correlated to fabrication of wrinkles by uniaxially stretching PU/PBDO elastomer films.


Asunto(s)
Materiales Biocompatibles/química , Elastómeros/química , Nanoestructuras/química , Nanoestructuras/ultraestructura , Rayos Ultravioleta , Urea/química , Uretano/química , Materiales Biocompatibles/efectos de la radiación , Relación Dosis-Respuesta en la Radiación , Elastómeros/efectos de la radiación , Ensayo de Materiales , Membranas Artificiales , Nanoestructuras/efectos de la radiación , Dosis de Radiación , Propiedades de Superficie , Urea/efectos de la radiación , Uretano/efectos de la radiación
5.
Phys Rev E Stat Nonlin Soft Matter Phys ; 75(5 Pt 1): 050701, 2007 May.
Artículo en Inglés | MEDLINE | ID: mdl-17677013

RESUMEN

The authors have measured the electro-optic Kerr effect in the isotropic phase of a urea derivative. Electric-field-induced birefringence Deltan was observed in the isotropic phase even 30 degrees C above the isotropic-columnar phase transition temperature. The induced birefringence is inversely proportional to temperature, as predicted by the Landau-de Gennes theory. Two distinct regions are identified from the proportionality constants in the isotropic phase; optical second-harmonic generation (SHG) is easily observable in the low-temperature region on applying an electric field, whereas SHG activity does not emerge in the higher-temperature region. The structure of molecular assemblies is discussed based on these experimental results.


Asunto(s)
Cristales Líquidos/química , Cristales Líquidos/efectos de la radiación , Modelos Químicos , Modelos Moleculares , Urea/química , Urea/efectos de la radiación , Anisotropía , Simulación por Computador , Campos Electromagnéticos , Luz , Transición de Fase/efectos de la radiación , Dosis de Radiación
6.
J Air Waste Manag Assoc ; 56(9): 1278-86, 2006 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-17004683

RESUMEN

The research objective was to adapt the ultraviolet (UV)-photolysis method to determine dissolved organic nitrogen (DON) in aqueous extracts of aerosol samples. DON was assumed to be the difference in total concentration of inorganic nitrogen forms before and after sample irradiation. Using a 2(2) factorial design the authors found that the optimal conversion of urea, amino acids (alanine, aspartic acid, glycine, and serine), and methylamine for a reactor temperature of 44 degrees C occurred at pH 2.0 with a 24-hr irradiance period at concentrations <33 microM of organic nitrogen. Different decomposition mechanisms were evident: the photolysis of amino acids and methylamine released mainly ammonium (NH4+), but urea released a near equimolar ratio of NH4+ and nitrate (NO3-). The method was applied to measure DON in the extracts of aerosol samples from Tampa, FL, over a 32-day sampling period. Average dissolved inorganic (DIN) and DON concentrations in the particulate matter fraction PM10 were 78.1 +/- 29.2 nmol-Nm(-3) and 8.3 +/- 4.9 nmol-Nm(-3), respectively. The ratio between DON and total dissolved nitrogen ([TDN] = DIN + DON) was 10.1 +/- 5.7%, and the majority of the DON (79.1 +/- 18.2%) was found in the fine particulate matter (PM2.5) fraction. The average concentrations of DIN and DON in the PM2.5 fraction were 54.4 +/- 25.6 nmol-Nm(-3) and 6.5 +/- 4.4 nmol-Nm(-3), respectively.


Asunto(s)
Aerosoles/efectos de la radiación , Contaminantes Atmosféricos/efectos de la radiación , Monitoreo del Ambiente/métodos , Nitrógeno/análisis , Aerosoles/análisis , Contaminantes Atmosféricos/análisis , Aminoácidos/efectos de la radiación , Concentración de Iones de Hidrógeno , Metilaminas/efectos de la radiación , Nitratos/análisis , Fotólisis , Compuestos de Amonio Cuaternario/análisis , Rayos Ultravioleta , Urea/efectos de la radiación
7.
Photomed Laser Surg ; 22(6): 489-93, 2004 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-15684748

RESUMEN

OBJECTIVE: This in vitro study examines the efficacy of two different dental whitening agents, Opalescence Xtra and Opus White, by analyzing the change in color achieved by the treatment and the temperature increase induced in the pulpal chamber. BACKGROUND DATA: Bleaching techniques achieved significant advances with the use of coherent or incoherent radiation sources to activate the bleaching chemicals. METHODS: The bleaching agents, containing 35% of hydrogen peroxide, were stimulated with 0.9 W of xenon arc lamp and 0.9 W or 2 W of a 960-nm diode laser during 60 sec (0.9 W) and 30 sec (2 W) on 33 extracted human teeth. During irradiation, the temperature in the pulpal cavity was monitored. The color change was evaluated using the CIE L*a*b* color space measurement system. RESULTS: The treated groups showed an increase in color saturation (DeltaC*) of 3-32% and a change in whiteness (DeltaL*) of 0-8%. This study found that only some of the irradiated groups show statistically significant difference (p < 0.05) in the effectiveness of their treatment when compared to the control, whereas no significant statistical difference was obtained in between the irradiated groups. Temperature increase was 2-4 degrees C when using the xenon arc lamp, 2-8 degrees C and 4-12 degrees C when using the diode laser at 0.9 W and 2 W, respectively. CONCLUSIONS: The results of this study suggest that Opalescence Extra and Opus White are both effective to provide brighter teeth. However, according to the conditions used in this study, only the xenon arc lamp induced a safer temperature increase.


Asunto(s)
Calor/uso terapéutico , Terapia por Láser , Peróxidos/efectos de la radiación , Polivinilos/efectos de la radiación , Blanqueamiento de Dientes , Urea/análogos & derivados , Urea/efectos de la radiación , Temperatura Corporal , Color , Pulpa Dental , Combinación de Medicamentos , Humanos , Blanqueamiento de Dientes/métodos , Xenón
8.
Vopr Med Khim ; 27(4): 523-7, 1981.
Artículo en Ruso | MEDLINE | ID: mdl-7293085

RESUMEN

Liver of X-ray irradiated rats /a dose of 18.06.10(-2) Ci per kg of body mass/, deprived of the body homeostatic influences, exhibited increased functional activity within the first day after irradiation: intensity of transamination was increased in mitochondria and supernatant as well as output of glucose and urea was elevated. Sensitivity to substrate stimulation of transamination and gluconeogenesis reactions was decreased in the liver within 3 days after irradiation.


Asunto(s)
Hígado/efectos de la radiación , Alanina Transaminasa/efectos de la radiación , Animales , Aspartato Aminotransferasas/efectos de la radiación , Gluconeogénesis/efectos de la radiación , Hígado/metabolismo , Masculino , Mitocondrias Hepáticas/efectos de la radiación , Perfusión , Ratas , Factores de Tiempo , Urea/efectos de la radiación
9.
Fiziol Zh (1978) ; 36(3): 30-4, 1990.
Artículo en Ruso | MEDLINE | ID: mdl-2394245

RESUMEN

The action of electrostatic field (320 kV/m) on the adaptability has been studied in experiments on young Wistar rats (females). Some parameters of carbohydrate, lipid and protein metabolism, and the process of lipid peroxidation were observed in blood serum, liver and brain. Glucose content was observed to increase in all the tissues, liver glycogen, cholesterol/phospholipid ratio. The urea and malondialdehyde increased in the liver and brain. The experiments have shown that the physiological adaptability is high.


Asunto(s)
Encéfalo/efectos de la radiación , Campos Electromagnéticos , Fenómenos Electromagnéticos , Hígado/efectos de la radiación , Animales , Encéfalo/metabolismo , Femenino , Glucosa/metabolismo , Glucosa/efectos de la radiación , Metabolismo de los Lípidos , Peroxidación de Lípido/fisiología , Peroxidación de Lípido/efectos de la radiación , Lípidos/efectos de la radiación , Hígado/metabolismo , Glucógeno Hepático/metabolismo , Glucógeno Hepático/efectos de la radiación , Malondialdehído/metabolismo , Malondialdehído/efectos de la radiación , Ratas , Urea/metabolismo , Urea/efectos de la radiación
10.
Free Radic Res ; 45(5): 507-17, 2011 May.
Artículo en Inglés | MEDLINE | ID: mdl-21284490

RESUMEN

The bioactive flavonoid baicalein has been shown to have radioprotective activity, although the molecular mechanism is poorly understood in vivo. C57BL/6 mice were irradiated with X-rays (15 Gy) with and without baicalein treatment (5 mg/kg/day). Irradiation groups showed an increase of NF-κB-mediated inflammatory factors with oxidative damage and showed inactivation of FOXO and its target genes, catalase and SOD. However, baicalein suppressed radiation-induced inflammatory response by negatively regulating NF-κB and up-regulating FOXO activation and catalase and SOD activities. Furthermore, baicalein inhibited radiation-induced phosphorylation of MAPKs and Akt, which are the upstream kinases of NF-κB and FOXOs. Based on these findings, it is concluded that baicalein has a radioprotective effect against NF-κB-mediated inflammatory response through MAPKs and the Akt pathway, which is accompanied by the protective effects on FOXO and its target genes, catalase and SOD. Thus, these findings provide new insights into the molecular mechanism underlying the radioprotective role of baicalein in mice.


Asunto(s)
Flavanonas/farmacología , Factores de Transcripción Forkhead/metabolismo , FN-kappa B/metabolismo , Nefritis/metabolismo , Nefritis/prevención & control , Traumatismos Experimentales por Radiación/tratamiento farmacológico , Protectores contra Radiación/farmacología , Animales , Antioxidantes/farmacología , Catalasa/metabolismo , Catalasa/efectos de la radiación , Creatinina/metabolismo , Creatinina/efectos de la radiación , Creatinina/orina , Quinasas MAP Reguladas por Señal Extracelular/efectos de los fármacos , Quinasas MAP Reguladas por Señal Extracelular/metabolismo , Quinasas MAP Reguladas por Señal Extracelular/efectos de la radiación , Proteína Forkhead Box O1 , Factores de Transcripción Forkhead/efectos de los fármacos , Factores de Transcripción Forkhead/efectos de la radiación , Glutatión/efectos de los fármacos , Glutatión/metabolismo , Glutatión/efectos de la radiación , Inflamación/metabolismo , Inflamación/prevención & control , Riñón/efectos de los fármacos , Riñón/metabolismo , Riñón/efectos de la radiación , Peroxidación de Lípido/efectos de los fármacos , Peroxidación de Lípido/efectos de la radiación , Ratones , Ratones Endogámicos C57BL , FN-kappa B/efectos de los fármacos , FN-kappa B/efectos de la radiación , Proteína Oncogénica v-akt/efectos de los fármacos , Proteína Oncogénica v-akt/metabolismo , Proteína Oncogénica v-akt/efectos de la radiación , Oxidación-Reducción/efectos de los fármacos , Oxidación-Reducción/efectos de la radiación , Fosforilación/efectos de los fármacos , Traumatismos Experimentales por Radiación/metabolismo , Transducción de Señal/efectos de los fármacos , Transducción de Señal/efectos de la radiación , Superóxido Dismutasa/efectos de los fármacos , Superóxido Dismutasa/metabolismo , Superóxido Dismutasa/efectos de la radiación , Urea/metabolismo , Urea/efectos de la radiación , Urea/orina , Rayos X
11.
Ultrason Sonochem ; 17(1): 55-7, 2010 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-19467908

RESUMEN

Synthesis of the glycolurils catalyzed by potassium hydroxide was carried out in 17-75% yield at 40 degrees C in EtOH under ultrasound irradiation. Compared to the method using stirring, the main advantage of the present procedure is milder conditions and shorter reaction time.


Asunto(s)
Alquinos/síntesis química , Alquinos/efectos de la radiación , Hidróxidos/química , Hidróxidos/efectos de la radiación , Imidazoles/síntesis química , Imidazoles/efectos de la radiación , Fenilglioxal/análogos & derivados , Compuestos de Potasio/química , Compuestos de Potasio/efectos de la radiación , Sonicación/métodos , Urea/química , Catálisis , Fenilglioxal/química , Fenilglioxal/efectos de la radiación , Dosis de Radiación , Urea/efectos de la radiación
13.
J Appl Bacteriol ; 58(1): 21-5, 1985 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-3980295

RESUMEN

Urea broth, a medium used for the identification of the genus Proteus, was sterilized by gamma radiation, using radiation doses of 1-1.5 Mrad. The radiation-sterilized medium, modified by adding sodium ascorbate and increasing its phenol red and yeast extract content, performed as well as the commercial formulation prepared aseptically, when tested with different Proteus and non-Proteus species. Gamma-irradiation appears to be an attractive and economical method for sterilizing nutrient media in sealed tubes, avoiding the risk of contamination during processing.


Asunto(s)
Medios de Cultivo/efectos de la radiación , Proteus/crecimiento & desarrollo , Esterilización , Urea/efectos de la radiación , Concentración de Iones de Hidrógeno
14.
Strahlenther Onkol ; 163(6): 400-2, 1987 Jun.
Artículo en Alemán | MEDLINE | ID: mdl-3603367

RESUMEN

The authors compare two different methods to determine the activity of the air induced by the bremsstrahlung of medical accelerators. The activities of the air resulting from maximum photon energies of 16 to 42 MeV are measured with a proportional counter tube ("direct measurement") and by means of activation analyses of imidazole, triazole, malonic acid, and urea specimens ("indirect measurement"). The results are compared.


Asunto(s)
Contaminación Radiactiva del Aire/análisis , Aceleradores de Partículas , Radiometría/métodos , Análisis por Activación , Humanos , Imidazoles/efectos de la radiación , Malonatos/efectos de la radiación , Triazoles/efectos de la radiación , Urea/efectos de la radiación
15.
Arch Geschwulstforsch ; 45(8): 737-45, 1975.
Artículo en Inglés | MEDLINE | ID: mdl-1230121

RESUMEN

This report describes measurements in a tissue equivalent phantom. At first the depth-dose curve is determined. Then the distribution of dose orthogonal to the central beam is determinated. On the base of these results single field distributions are constructed and also distributions in case of irradiations from both sides. Any influence of different ti-sues (fat, bone) to the distribution of isodose could not be pointed out. Distributions of isodose from Co60-moving fields added to the distributions of neutrons are described.


Asunto(s)
Neutrones Rápidos , Neutrones , Radioterapia/métodos , Carbohidratos/efectos de la radiación , Radioisótopos de Cobalto , Alemania Oriental , Glicerol/efectos de la radiación , Modelos Estructurales , Dosis de Radiación , Monitoreo de Radiación , Urea/efectos de la radiación , Agua/efectos de la radiación
16.
Physiol Chem Phys ; 8(3): 253-8, 1976.
Artículo en Inglés | MEDLINE | ID: mdl-796856

RESUMEN

Characteristic alterations of enzymatic reaction rates by irradiation of the crystalline substrates for fixed periods with an Hg vapor lamp were reported by Comorosan in 1969. Results of single- and double-blind studies reported here support the validity of the key features of this striking and potentially important phenomenon.


Asunto(s)
Luz , Urea/efectos de la radiación , Ureasa/metabolismo , Amoníaco/metabolismo , Ensayos Clínicos como Asunto , Técnicas In Vitro , Factores de Tiempo , Urea/metabolismo , Ureasa/efectos de la radiación
17.
Orig Life Evol Biosph ; 32(2): 91-8, 2002 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-12185677

RESUMEN

The photochemistry of a mixture of urea and maleic acid, which are thought to have been widely present on the primitive Earth, was studied in order to examine a possibility of the formation of amino acids. When an aqueous solution of urea and maleic acid was irradiated with an ultraviolet light of wavelength 172 nm, urea was revealed to be rather resistant to photochemical decomposition. In contrast, maleic acid was completely decomposed within 4 h, reflecting the reactivity of a C-C double bond in the molecule. In the reaction mixture, 2-isoureidosuccinic acid was detected. The acid was considered to be formed by addition of an isoureido radical which had been produced from urea by the action of a hydroxyl radical, to a C-C double bond of maleic acid. The isoureido group of the product was revealed to undergo thermal rearrangement to afford 2-ureidosuccinic acid (N-carbamoylaspartic acid). The result suggested a novel pathway leading to the formation of aspartic acid from non-amino acid precursors, possibly effected by UV-light on the primitive Earth. The formation of ureidocarboxylic acids is of another significance, since they are capable of undergoing thermal polymerization, resulting in formation of polyamino acids.


Asunto(s)
Ácido Aspártico/efectos de la radiación , Maleatos/química , Rayos Ultravioleta , Urea/química , Ácido Aspártico/química , Maleatos/efectos de la radiación , Modelos Moleculares , Estructura Molecular , Urea/efectos de la radiación
18.
Biomacromolecules ; 2(4): 1260-6, 2001.
Artículo en Inglés | MEDLINE | ID: mdl-11777401

RESUMEN

The chemical changes induced by electron-beam irradiation of mixtures of N-allylurea (AU) and amorphized starch were studied by spectroscopic methods for identifying and monitoring the reactions providing the blend with stabilized physical properties. Spectral modifications essentially concerned the AU constituent in the irradiated mixtures. FTIR and NMR analyses were used to quantify the progress of AU conversion upon irradiation and to gain information on the structure of the products. The influence of sample temperature and moisture on AU conversion rate was examined. The kinetic treatment of conversion vs dose data, from blends with different contents in AU, suggested that the phenomenological order for the reaction rate was zero, relative to the concentration in AU. The grafting yield was determined from combined (1)H NMR data recorded after selective solubilization of the constituents allowing for extraction of AU monomer and homopolymer from the grafted polysaccharide. Graft polymerization was more efficient than homopolymerization in samples containing AU in amounts less than its limiting solubility and relatively less efficient in thermodynamically unstable blends.


Asunto(s)
Almidón/química , Urea/análogos & derivados , Urea/química , Relación Dosis-Respuesta en la Radiación , Electrones , Estructura Molecular , Resonancia Magnética Nuclear Biomolecular , Polímeros/síntesis química , Polímeros/química , Resinas Sintéticas/síntesis química , Resinas Sintéticas/química , Almidón/efectos de la radiación , Urea/efectos de la radiación
19.
J Esthet Restor Dent ; 13(6): 370-8, 2001.
Artículo en Inglés | MEDLINE | ID: mdl-11778856

RESUMEN

PURPOSE: This study investigated the effect of the presence, absence, and aging of a heat-enhancing compound (colorant) added to bleaching gel on the temperature rise of the gel itself, as well as the temperature rise within the pulp chamber, when a tooth was exposed to a variety of light-curing units in vitro. MATERIALS AND METHODS: An extracted human upper central incisor was fitted with thermocouples placed in the pulp chamber as well as on the facial tooth surface. A temperature-controlled simulated intrapulpal fluid flow was provided to the tooth, and bleaching agent (Opalesence XTRA, Ultradent) containing heat-enhancing colorant, aged colorant, or no colorant was applied to the facial surface. The tooth and light-curing unit were placed in a thermostatically controlled oven at 37 degrees C, and real-time gel and intrapulpal temperature values were recorded digitally. Light-curing units used were a plasma arc light (PAC) (PowerPac, ADT), a conventional quartz tungsten halogen source (QTH) (Optilux 501, Demetron/Kerr), the QTH light used in high-power (bleaching) mode, and an argon ion laser (AccuCure 3000, LaserMed). An exposure scenario simulating light-enhanced bleaching of 10 upper teeth was developed. Temperature rise over the pre-exposure, baseline value associated with the last light exposure in the bleaching sequence was calculated for each curing and bleaching combination. Five replications for each test condition were made. Temperature rise values were compared using analysis of variance (ANOVA) at a preset alpha of 0.05. RESULTS: When fresh colorant-containing bleach was used, the PAC light increased bleach temperature 39.3 degrees C above baseline. With no added colorant, temperature rise was 37.1 degrees C. The QTH light in bleach mode resulted in gel temperature 24.8 degrees C above baseline, whereas the temperature increase was only 11.5 degrees C when no colorant was used. Conventional QTH light use increased fresh bleach temperature by 17.7 degrees C, whereas an increase of only 11.1 degrees C was measured without colorant. The argon ion laser produced equivalent temperature rise regardless of the presence or freshness of the colorant, approximately 9.4 degrees C. Intrapulpal temperatures were all significantly lower than those recorded in the bleaching gel and ranged from 5 degrees to 8 degrees C. As a rule, the presence of fresh heat-enhancing colorant in the bleaching gel resulted in a significant intrapulpal temperature increase (approximately 1 degrees C) over that reached using other lights. The PAC and the QTH light used in bleach mode induced greater intrapulpal temperature rise than the laser. CLINICAL SIGNIFICANCE: Freshness of bleaching agent incorporating light-activated, heat-enhancing colorant influences temperature rise of bleaching gel and also may increase intrapulpal temperature values. Use of intense lights does elevate bleach temperature and also results in increased intrapulpal temperature that may further impact on patient sensitivity and pulpal health resulting from this treatment.


Asunto(s)
Peróxidos/química , Peróxidos/efectos de la radiación , Blanqueamiento de Dientes/métodos , Urea/análogos & derivados , Urea/química , Urea/efectos de la radiación , Análisis de Varianza , Temperatura Corporal , Peróxido de Carbamida , Color , Pulpa Dental/fisiología , Combinación de Medicamentos , Calor , Humanos , Incisivo , Rayos Infrarrojos , Rayos Láser , Luz , Estadísticas no Paramétricas , Rayos Ultravioleta
20.
Pharmacol Res ; 43(2): 185-91, 2001 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-11243721

RESUMEN

Pharmacological and cytogenetic evaluations of the protective effects of polyethoxylated castor oil cremophor-EL (cremophor) against hepato, renal and bone marrow toxicity induced by gamma irradiation in normal rats were carried out. A single dose of irradiation (6 Gy) caused hepatic and renal damage manifested biochemically as an elevation in levels of serum alanine and aspartate aminotransferase as well as an increase in blood urea. Cremophor administration at a dose level of 50 microl kg-1 intravenously 1 day before exposure to irradiation (6 Gy) protected the liver and kidney as indicated by the recovery of levels of hepatic aminotransferase, urea and lipid profiles to normal values. Gamma irradiation of male rats caused a decrease in reduced glutathione and an increase in the oxidized form in rat-liver homogenate. A highly significant increase in the incidence of micronucleated normochromatic erythrocytes and micronucleated polychromatic erythrocytes was observed after irradiation exposure. The induced genotoxicity in the bone marrow cells was corrected by pretreatment with cremophor. The findings of this study suggest that cremophor pretreatment can potentially be used clinically to prevent irradiation-induced hepato, renal and bone marrow toxicity without interference with its cytotoxic activity.


Asunto(s)
Rayos gamma , Glicerol/farmacología , Hiperlipidemias/sangre , Riñón/efectos de los fármacos , Hígado/efectos de los fármacos , Tensoactivos/farmacología , Alanina Transaminasa/sangre , Alanina Transaminasa/efectos de los fármacos , Alanina Transaminasa/efectos de la radiación , Animales , Aspartato Aminotransferasas/sangre , Aspartato Aminotransferasas/efectos de los fármacos , Aspartato Aminotransferasas/efectos de la radiación , Células de la Médula Ósea/efectos de los fármacos , Células de la Médula Ósea/efectos de la radiación , Colesterol/sangre , Colesterol/efectos de la radiación , Creatinina/sangre , Creatinina/efectos de la radiación , Rayos gamma/efectos adversos , Glutatión/efectos de los fármacos , Glutatión/metabolismo , Glutatión/efectos de la radiación , Glicerol/análogos & derivados , Glicerol/uso terapéutico , Hiperlipidemias/tratamiento farmacológico , Riñón/metabolismo , Riñón/efectos de la radiación , Hígado/metabolismo , Hígado/efectos de la radiación , Masculino , Ratones , Micronúcleos con Defecto Cromosómico/efectos de los fármacos , Micronúcleos con Defecto Cromosómico/metabolismo , Micronúcleos con Defecto Cromosómico/efectos de la radiación , Ratas , Ratas Wistar , Tensoactivos/uso terapéutico , Triglicéridos/sangre , Triglicéridos/efectos de la radiación , Células Tumorales Cultivadas , Urea/sangre , Urea/efectos de la radiación
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