Preparo de óxido de nióbio suportado em alumina por deposição química em fase vapor: caracterização por espectroscopia vibracional e termogravimetria

Alumina supported niobium oxide was prepared by chemical vapor deposition (CVD) of NbCl5. The alumina was calcined and pretreated at differents temperatures in order to vary the density of OH groups on the surface which was determined by thermogravimetric analysis. A good correlation was found between the amount of anchored niobium and the total number of anionic sites (oxide and hydroxyl groups) on the surface of the alumina. The infrared spectra on the OH stretching region indicate that OH groups coordinated to at least one tetrahedral aluminum were more reactive towards NbCl5.

Filmes de diamante CVD dopado com boro. Parte I . Histórico, produção e caracterização

This review presents a brief account concerning the production, characterization and evolution of the knowledge in the area of diamond and boron-doped diamond films. The most important methods used for the growth of these films, such as chemical vapor deposition and high pressure/high temperature systems, as well as the several kinds of reactors which can be employed are reviewed. However, larger emphasis is given to the CVD method. Morphological, structural and electric properties of these films, as well as their role in the performance of voltammetric electrodes for electrochemistry and electroanalytical chemistry are also discussed.

A geração química de vapor em espectrometria atômica

The historical development of atomic spectrometry techniques based on chemical vapor generation by both batch and flow injection sampling formats is presented. Detection via atomic absorption spectrometry (AAS), microwave induced plasma optical emission spectrometry (MIP-OES), inductively coupled plasma optical emission spectrometry (ICP-OES) , inductively coupled plasma mass spectrometry (ICP-MS) and furnace atomic nonthermal excitation spectrometry (FANES) are considered. Hydride generation is separately considered in contrast to other methods of generation of volatile derivatives. Hg ¾ CVAAS (cold vapor atomic absorption spectrometry) is not considered here. The current state-of-the-art, including extension, advantages and limitations of this approach is discussed.

Sistema RTP: uma técnica poderosa para o monitoramento da formação de nanotubos de carbono durante o processo por deposição de vapor químico

In this work, a TPR (Temperature Programmed Reduction) system is used as a powerful tool to monitor carbon nanotubes production during CVD (Chemical Vapour Deposition), The experiments were carried out using catalyst precursors based on Fe-Mo supported on Al2O3 and methane as carbon source. As methane reacts on the Fe metal surface, carbon is deposited and H2 is produced. TPR is very sensitive to the presence of H2 and affords information on the temperature where catalyst is active to form different forms of carbon, the reaction kinetics, the catalyst deactivation and carbon yields.

The 21st century chemistry journal

Internet publication will radically alter how chemists will publish their research in the next century. In this article, we describe two fundamental changes: enhanced chemical publication which allows chemists to publish materials that cannot be published on paper and end-user customization which allows readers to read articles prepared to meet their specifications. These concepts have been implemented within the Internet Journal of Chemistry, a new journal designed to employ the latest technologies for chemical publications.

Obtenção de filmes espessos de seleneto de cobre sobre carbono vítreo, ouro, titânio e cobre

Copper selenide (berzelianite) films were prepared on the title substrates using the chemical bath deposition technique (CBD). Film composition was determined by energy dispersion of x-rays. The kinetics of film growth is parabolic and film adherence limits the film thickness. On titanium, copper selenide forms islands that do not completely cover the surface, unless the substrate is prepared with a tin oxide layer; film composition also depends on the titanium oxide layer. On vitreous carbon, CBD and mechanical immobilization techniques lead to films with similar resistances for the electron transfer across the film/substrate interface. On gold, composition studies revealed that film composition is always the same if the pH is in the range from 8 to 12, in contrast to films prepared by an ion-ion combination route. On copper, a new procedure for obtaining copper selenide films as thick as 5 µm has been developed.

Use of thin films obtained by plasma polymerization for grain protection and germination enhancement

In this work, preliminary results of the use of hydrophobic thin films obtained by plasma deposition to protect grains and seeds are presented: grains coated by the films did not present biological degradation when stored in a saturated water vapor environment, but had their germination accelerated in the presence of water. A model that explains the difference of behavior of the films when exposed to water in vapor form or in liquid form, based on the formation of microchannels within the film that lead to water uptake in seeds, is presented. The model was successfully tested using quartz crystal measurements, which showed that the microchannels within the films can favor the adsorption and permeation of water when the films are immersed in water.

Alteração do caráter hidrofílico de filmes de quitosana por tratamento de plasma de HMDS

Alteration in hydrophilicity feature of chitosan films by hexamethyldisilazane (HMDS) cold-plasma treatment is evaluated. All treated films were colorless and transparent with no apparent textural changes. The effect on surfaces was characterized through contact angle measurements, degree of swelling and water vapor permeation. A significant reduction in all of the hydrophilicity parameters was observed. It is assumed that the HMDS treatment forms nonpolar silicone type structures. The goal is to investigate the formation of a stable hydrophobic barrier in order to increase the chitosan films usefulness in packaging applications.

Plasma cortisol levels in captive wild felines after chemical restraint

Eight Panthera onca (Po), 13 Felis concolor (Fc), 7 Felis yagouaroundi (Fy), 7 Felis tigrina (Ft) and 5 Felis pardalis (Fp) specimens from São Paulo State zoos were used. All animals were restrained with darts containing 10 mg/kg ketamine and 1 mg/kg xylazine. Venous blood samples were collected as soon as possible (within 15-20 min) and serum was frozen until the time for cortisol quantification. Cortisol was determined using a solid phase radioimmunoassay with an intra-assay coefficient of 8.51%. Data were analyzed statistically by the Kruskal-Wallis test, followed by Dunn's multiple comparisons test, and the one-sample t-test, with the level of significance set at P<0.05. Data are reported as means ± SEM. Cortisol levels differed among the captive felines: Po = 166 ± 33a, Fc = 670 ± 118b, Fy = 480 ± 83b, Ft = 237 ± 42ab, Fp = 97 ± 12a nmol/l (values followed by different superscript letters were significantly different (P<0.001)). Since most of the veterinary procedures on these species involve chemical restraint, these results show the necessity of preventive measures in order to minimize the effect of restraint stress on more susceptible species

Availability of heavy metals in contaminated soil evidenced by chemical extractants

Heavy metals have been accumulating in Brazilian soils, due to natural processes, such as atmospheric deposition, or human industrial activities. For certain heavy metals, when in high concentrations in the soil, there is no specific extractant to determine the availability of these elements in the soil. The objective of the present study was to evaluate the availability of Cd, Cu, Fe, Mn, Pb and Zn for rice and soybeans, using different chemical extractants. In this study we used seven soil samples with different levels of contamination, in completely randomized experimental design with four replications. We determined the available concentrations of Cd, Cu, Fe, Mn, Pb and Zn extracted by Mehlich-1, HCl 0.1 mol L-1, DTPA, and organic acid extractants and the contents in rice and soybeans, which extracts were analyzed by ICP-OES. It was observed that Mehlich-1, HCl 0.1 mol L-1 and DTPA extractants were effective to assess the availability of Cd, Cu, Pb and Zn for rice and soybeans. However, the same was not observed for the organic acid extractant.

Analysis of the chemical components of hydatid fluid from Echinococcus granulosus

Introduction The aim of this study was to explore the environment of Echinococcus granulosus (E. granulosus) protoscolices and their relationship with their host. Methods Proteins from the hydatid-cyst fluid (HCF) from E. granulosus were identified by proteomics. An inductively coupled plasma atomic emission spectrometer (ICP-AES) was used to determine the elements, an automatic biochemical analyzer was used to detect the types and levels of biochemical indices, and an automatic amino acid analyzer was used to detect the types and levels of amino acids in the E. granulosus HCF. Results I) Approximately 30 protein spots and 21 peptide mass fingerprints (PMF) were acquired in the two-dimensional gel electrophoresis (2-DE) pattern of hydatid fluid; II) We detected 10 chemical elements in the cyst fluid, including sodium, potassium, calcium, magnesium, copper, and zinc; III) We measured 19 biochemical metabolites in the cyst fluid, and the amount of most of these metabolites was lower than that in normal human serum; IV) We detected 17 free amino acids and measured some of these, including alanine, glycine, and valine. Conclusions We identified and measured many chemical components of the cyst fluid, providing a theoretical basis for developing new drugs to prevent and treat hydatid disease by inhibiting or blocking nutrition, metabolism, and other functions of the pathogen.

Chemical composition of phytoplankton from the estuaries of Eastern Amazonia

Phytoplankton is important bioindicator of chemical and biological modifications of natural ecosystems. The objective of this study was to determine the total chemical composition of the phytoplankton of the Pará and Mocajuba estuaries on the eastern coast of the Amazon region in the Brazilian state of Pará. The chemical composition of the surface water, bottom sediments (total sample and bioavailable fraction), and the phytoplankton were determined by inductively coupled plasma optical emission spectrometry. Phytoplankton contained high concentrations of Ca, P, Mn, Fe, Zn, Al, Ba, and Pb. The phytoplankton of the Mocajuba estuary is rich in Fe (2,967-84,750 µg g-1), while those from the Pará is rich in Al (1,216-15,389 µgg-1), probably reflecting divergent anthropogenic inputs. Both samples indicated a high bioconcentration factor derived from both the water and the bioavailable fraction, reflecting the efficiency of these organisms in the concentration of metals.

Lipoprotein (a): Structure, Pathophysiology and Clinical Implications

The chemical structure of lipoprotein (a) is similar to that of LDL, from which it differs due to the presence of apolipoprotein (a) bound to apo B100 via one disulfide bridge. Lipoprotein (a) is synthesized in the liver and its plasma concentration, which can be determined by use of monoclonal antibody-based methods, ranges from < 1 mg to > 1,000 mg/dL. Lipoprotein (a) levels over 20-30 mg/dL are associated with a two-fold risk of developing coronary artery disease. Usually, black subjects have higher lipoprotein (a) levels that, differently from Caucasians and Orientals, are not related to coronary artery disease. However, the risk of black subjects must be considered. Sex and age have little influence on lipoprotein (a) levels. Lipoprotein (a) homology with plasminogen might lead to interference with the fibrinolytic cascade, accounting for an atherogenic mechanism of that lipoprotein. Nevertheless, direct deposition of lipoprotein (a) on arterial wall is also a possible mechanism, lipoprotein (a) being more prone to oxidation than LDL. Most prospective studies have confirmed lipoprotein (a) as a predisposing factor to atherosclerosis. Statin treatment does not lower lipoprotein (a) levels, differently from niacin and ezetimibe, which tend to reduce lipoprotein (a), although confirmation of ezetimibe effects is pending. The reduction in lipoprotein (a) concentrations has not been demonstrated to reduce the risk for coronary artery disease. Whenever higher lipoprotein (a) concentrations are found, and in the absence of more effective and well-tolerated drugs, a more strict and vigorous control of the other coronary artery disease risk factors should be sought.

Role of enhanced detoxication in a deltamethrin-resistant population of Triatoma infestans (Hemiptera, Reduviidae) from Argentina

Deltamethrin and other pyrethroids have been extensively used in Argentina since 1980, for the chemical control of Triatoma infestans Klug (Hemiptera: Reduviidae). Recently, resistance to deltamethrin was detected in field populations by the survival of bugs exposed by topical application to the diagnostic dose estimated on the CIPEIN susceptible strain. Results of the current study showed low resistant ratios (RRs) to deltamethrin for the resistant populations (RR ranged from 2.0 for San Luis colony to 7.9 for Salta colony). Biochemical studies were made on the most resistant colony (Salta) and the susceptible strain (CIPEIN), in order to establish the importance of degradative mechanisms as a cause of the detected resistance. Esterase activity was measured on 3 days old first instars through phenylthioacetate and a-naphtyl acetate activities. The results showed a significant difference in no cholinesterase esterase activity from susceptible (7.6 ± 0,7 µM S./i.min.) and Salta resistant colony (9.5 ± 0.8 µM S./i.min.). Cytochrome P450 mono-oxygenase (P450) activity was measured on individual insects through ethoxycoumarine deethylase (ECOD) activity using a fluorescence micro plate reader. The dependence of ECOD activity on age and body region of the nymphs, and pH and time of incubation were studied in order to optimize the measurement. As a result, comparative studies were performed on abdomens of 2 days old first instars at pH 7.2 and 4 h incubation time. ECOD activity of first nymphs was significantly lower in the susceptible colony (61.3 ± 9.08 pg ECOD/ insect) than in the resistant one (108.1± 5.7 pg ECOD/ insect). These results suggest that degradative esterases (no-cholinesterase) and mono-oxygenases cytochrome P450, play an important role in the resistance to deltamethrin in Salta colony from Argentina.

In vivo antileishmanial activity and chemical profile of polar extract from Selaginella sellowii

The polar hydroethanolic extract from Selaginella sellowii(SSPHE) has been previously proven active on intracellular amastigotes (in vitro test) and now was tested on hamsters infected with Leishmania (Leishmania) amazonensis (in vivo test). SSPHE suppressed a 100% of the parasite load in the infection site and draining lymph nodes at an intralesional dose of 50 mg/kg/day × 5, which was similar to the results observed in hamsters treated with N-methylglucamine antimonate (Sb) (28 mg/Kg/day × 5). When orally administered, SSPHE (50 mg/kg/day × 20) suppressed 99.2% of the parasite load in infected footpads, while Sb suppressed 98.5%. SSPHE also enhanced the release of nitric oxide through the intralesional route in comparison to Sb. The chemical fingerprint of SSPHE by high-performance liquid chromatography with diode-array detection and tandem mass spectrometry showed the presence of biflavonoids and high molecular weight phenylpropanoid glycosides. These compounds may have a synergistic action in vivo. Histopathological study revealed that the intralesional treatment with SSPHE induced an intense inflammatory infiltrate, composed mainly of mononuclear cells. The present findings reinforce the potential of this natural product as a source of future drug candidates for American cutaneous leishmaniasis.