RESUMEN
Aqueous colloidal solutions of quantum sized particles of titanium dioxide (Q-TiO2) undergo an aging process since the moment of their preparation. In course of time, the mean size of nanoparticles is gradually increasing and some of their physicochemical properties are changing as well. In the present study, the decrease of the blue spectral shift of the semiconductor absorption threshold was measured to determine the corresponding changes of band gap energy of the Q-TiO2 particles. In parallel, the decrease of the specific surface area of these particles was followed through their complexation with 2-coumaric acid. The formation kinetics and thermodynamic equilibrium of these surface charge-transfer complexes were investigated in detail by means of UV/vis absorption spectroscopy. Besides, the size and shape of the Q-TiO2 particles aged 2, 4, and 10 years were compared employing direct observation by means of high resolution transmission electron microscopy. On the basis of real particle images, a model of nanocrystalline anatase was developed. The specific surface areas estimated through complexation with 2-coumaric acid were confronted with the numbers of appropriate titanium atoms located on the particle surface that were calculated from a model of anatase nanocrystals of different sizes. The photocatalytic activity, which represents the most important quality of anatase from practical point of view, was repeatedly determined through photocatalytic degradation of 4-chlorophenol in a colloidal solution of Q-TiO2 particles during its aging at 4 degrees C for three years. The corresponding reaction rate was increasing rapidly in the first weeks; it almost tripled in 68 days, and afterward it approached a limiting value. On the whole, the initial value increased four times in three years. Voltammetry at hanging mercury drop as the last method for aging description did not show any significant change of voltammetric behavior in a short two months period. However, while compared to preceding results of a similar TiO2 system, new redox processes of Q-TiO2 colloids were observed in the negative potential range. Besides the reduction of surface protons reported previously, two new pairs of peaks appeared.
RESUMEN
Kinetics of the oxidative photodegradation of monuron (3-(4-chlorophenyl)-1-1-dimethylurea) in both homogeneous solution of Fe(ClO4)3 and heterogeneous suspension of TiO2, were investigated and compared. In the homogeneous system (Fe(II)), the speciation of Fe(III) aquacomplexes was shown to play an essential role in the rate of photodegradation. For high concentrations of TiO2 (> 500 mg L(-1)), the photodegradation rate was similar to the reaction rate obtained with a freshly prepared solution of Fe(II) (3 x 10(-4) mol L(-1)). In the combined system (TiO2 + Fe(III)), a synergy effect accelerating the monuron photodegradation was observed. Actually, in the presence of Fe(III) (in concentration compatible with a safe environment), a similar reaction rate for monuron photodegradation was obtained with a TiO2 concentration lower by a factor of 20.
Asunto(s)
Colorantes/química , Hierro/química , Titanio/química , Contaminantes del Agua/aislamiento & purificación , Purificación del Agua/métodos , Catálisis , FotoquímicaRESUMEN
Metamitron (1) does not undergo hydrolysis at pH 1-8 and up to 5 M H(2)SO(4). The product of its two-electron reduction, 1, 6-dihydrometamitron (2), on the other hand, undergoes at pH <3 relatively fast hydrolysis. The dependence of the measured rate constant on acidity indicates that the completely protonated form (AH(2)(2+)) predominating in strongly acidic media undergoes hydrolysis slower than the species bearing one less proton (AH(+)). The latter most reactive species is present in highest concentration in solutions of pH between 0 and 2. This species is protonated on the 2,3-azomethine bond and yields as final products 2-hydrazino-2-phenylacetic acid (4) and acethydrazide (5). Kinetic, polarographic, and spectrophotometric measurements indicated for the first dissociation an average value pK(a) = -0.8, for the second pK(a) = 0.95. These observations together with the easy reduction of the 1,6-bond in metamitron (1) indicate that in nature the cleavage of metamitron may be preceded by its reduction to 1, 6-dihydrometamitron (2), which is then hydrolyzed. Thus, anaerobic, reductive conditions are likely preferable for the total microbial degradation of metamitron.
Asunto(s)
Herbicidas/química , Triazinas/química , Concentración de Iones de Hidrógeno , Hidrólisis , Estructura Molecular , Oxidación-ReducciónRESUMEN
The investigation assessed, whether a nonspecific single and repeated immunization induced by Listeria monocytogenes Ei factor, BCG vaccine and their combination influences the growth of transplanted syngenic methylcholanthrene tumour depending on tumour graft cellularity. The cellularity of 10(4) and 10(5) were investigated. Tumour growth was examined 10 and 17 days after the inoculation. It has been found that single Ei factor administration did not influence the tumour growth. Single BCG vaccine favourably influenced the tumour growth, but in progressing time and cellularity the effect was failing. In combination of BCG vaccine and Listeria Ei factor the antitumour effect appeared to be most profound. In progressing time after the tumour grafting and graft cellularity the effect was disappearing. It was probably due to the fact that immunotherapy fails to control tumour mass with high cellularity. The antitumour effect potentiation by combination of BCG vaccine with Ei factor suggests a way to a possible combined antitumour immunotherapy.
Asunto(s)
Vacuna BCG/administración & dosificación , Factores Biológicos/administración & dosificación , Neoplasias Experimentales/patología , Animales , Vacuna BCG/uso terapéutico , Factores Biológicos/uso terapéutico , Metilcolantreno , Ratones , Ratones Endogámicos C3H , Trasplante de Neoplasias , Neoplasias Experimentales/inducido químicamente , Neoplasias Experimentales/terapiaRESUMEN
The investigation assessed, whether a nonspecific single and repeated immunization induced by Listeria monocytogenes Ei factor, BCG vaccine and their combination influences the growth of transplanted syngenic methylcholanthrene tumour depending on tumor graft cellularity. The cellularity of 10(4) and 10(5) were investigated. Tumour growth was examined 10 and 17 days after the inoculation. It has been found that single Ei factor administration did not influence the tumour growth. Single BCG vaccine favourably influenced the tumour growth, but in progressing time and cellularity the effect was failing. In combination of BCG vaccine and Listeria Ei factor the antitumour effect appeared to be most profound. In progressing time after the tumour grafting and graft cellularity the effect was disappearing. It was probably due to the fact that immunotherapy fails to control tumour mass with high cellularity. The antitumour effect potentiation by combination of BCG vaccine with Ei factor suggests a way to a possible combined antitumour immunotherapy.
Asunto(s)
Vacuna BCG/administración & dosificación , Factores Biológicos/administración & dosificación , Neoplasias Experimentales/patología , Animales , Inmunoterapia , Masculino , Metilcolantreno , Ratones , Ratones Endogámicos C3H , Neoplasias Experimentales/inducido químicamente , Trasplante IsogénicoRESUMEN
The authors report on the results of combined chemotherapy using cyclical alternations with several non-crossed resistant combinations in patients with gastric carcinoma in the adjuvant and palliative indication. The report includes also a small group of 6 patients with locally inoperable carcinoma, treated by radio-chemotherapy, followed by subsequent second-look resection and postoperative chemotherapy. Prolongation of survival in these patients indicates that possible benefit of the treatment regimens administered may be expected. Prospective randomized study is recommended to check the obtained results.
Asunto(s)
Protocolos de Quimioterapia Combinada Antineoplásica/uso terapéutico , Neoplasias Gástricas/terapia , Anciano , Protocolos de Quimioterapia Combinada Antineoplásica/efectos adversos , Terapia Combinada , Femenino , Humanos , Masculino , Persona de Mediana Edad , Cuidados Paliativos , Neoplasias Gástricas/mortalidadRESUMEN
On the basis of a simple examination of the phagocytic activity of leukocytes of the peripheral blood., with the help of the yeast cells Saccharomyces cerevisiae, we determined the functional ability of leukocytes in untreated patients with the Hodgkin's disease, in the course of the primary chemotherapy, during the complete remission and in the relapse of the disease. In all the periods we found only changes in the absolute number of phagocytic cells, corresponding to the changes in the leukocyte count (increased numbers in untreated patients and in relapse, decreased number in the course of the chemotherapy). The value of the phagocytic and activity indices in untreated patients were only moderately reduced. In the course of chemotherapy there was a more remarkable drop of the phagocytic activity only in the first half of the treatment series. In the complete remission the phagocytic activity values were normal. We did not observe significant differences between clinical stages of the Hodgkin's disease in any group. Our results correspond to the clinical course of the disease (absence of infectious complications) in the patients followed. The presented conclusions do not concern bactericidal ability of leukocytes, which is not reflected by the test method used. The test described here does not provide more data for monitoring the clinical course and chemotherapy of Hodgkin's disease than do routine examinations of the erythrocyte sedimentation and white blood count.
Asunto(s)
Enfermedad de Hodgkin/inmunología , Leucocitos/inmunología , Fagocitosis , Femenino , Enfermedad de Hodgkin/diagnóstico , Enfermedad de Hodgkin/tratamiento farmacológico , Humanos , Masculino , Saccharomyces cerevisiaeRESUMEN
The authors examined a course of immunoglobulin values (IgA, IgG, IgM) in 40 patients with the Hodgkin's disease and repeatedly in 11 healthy persons. In the patients they followed the levels of the immunoglobulins during the disease, up to 5 years. In untreated patients there were statistically significant increased IgA levels and insignificant increase of IgG. In the course of remission the immunoglobulin values were normalized. The radiotherapy did not affect significantly the value of immunoglobulins, the combined chemotherapy (COPP) led to a drop of this level. The levels of immunoglobulins are recovered after chemotherapy in the case of successful treatment. In terms of the prognosis the authors consider as unfavorable high increase in the immunoglobulin levels in untreated patients and their rapid drop during the chemotherapy. They observed an average preterminal drop of the IgA by 27%, IgG by 23% and IgM by 44% with respect to controls.