Search

The corrosion of a number of coarse- and fine-grained copper materials has been studied in an aerated aqueous nitric acid (100 mM) solution. The materials properties and the consequences of corrosion were characterized by scanning electron microscopy, electron back scatter diffraction and confocal laser scanning microscopy. The corrosion of the coarse-grained materials was shown to be strongly influenced by the crystallographic orientations of grains. For fine-grained materials grain boundary etching at high angle grain boundaries and grain boundary pores (for cold sprayed copper) overrode the influences of texture on the corrosion rate.

International audience; Iron as a trace element plays a role in regulating the homeostasis of the human body and therefore the concentration of iron in the body must be carefully monitored. Both deficiency and overload of iron could have a serious effect on health. Iron in excess can be carcinogenic in different ways. As a catalyst of Fenton's reaction it leads to the creation of reactive oxygen species which causes oxidative stress and DNA damage, among other things. Iron can also reduce the response of the immune system to cancer and induce increased cancer cell proliferation. Ovarian cancer is one of the most common neoplasms in women and has a low survival rate. For this reason, there is strong motivation to deepen the understanding of the processes that lead to the disease and take place in ovarian cancer tissue. In this study, cryo micro X-ray absorption near edge structure spectroscopy was used to analyse the oxidation state of iron in ovarian cancer samples. For calibration, organic and inorganic reference samples containing Fe in different oxidation states were used. To determine the trace element in the neoplasm samples, the pre-edge region, white line and absorption edge position of Fe K-edge XANES spectra were examined and compared to those of the recorded reference materials. A comparison of these XANES spectral features shows the existence of differences in the iron oxidation state between the neoplasm samples and suggests the possibility that a combination of iron ions can occur in one sample. Overall, further investigations are required to make a better comparison and determine what organic compounds are contained in the samples and possibly carry out a statistical analysis.

NiMoP/MCM41-γAl2O3 (NiMoP/AMx) supported catalysts have been investigated as a modification of MCM41 by using the sol–gel alumina incorporation method. Different catalysts were synthesized varying the Si/Al molar ratio (5, 10, 25 and 50). The aqueous solution method was used to impregnate the metallic species (NiMoP) on the AMx supports. A surface area high mesoporous solid was synthesized by using an organic template method. The incorporation of sol–gel alumina did modified the hexagonal array of the mesoporous material MCM41 when the preparation of AMx supports was carried out. The XRD patterns of the catalytic supports show that phases, MCM-41 and γ-Al2O3 exist, indicating the presence of the two materials in the synthesized solids. Raman spectroscopy also indicates the formation of NiMoO4 and MoO3 which are more difficult to sulfide and produce MoS2 and Ni3S2 as separated sulfides instead of the NiMoS phase. The symmetries of the materials were determined through UV–vis where octahedral NiO as well as tetrahedral and octahedral Mo were found. The main reaction products were biphenyl (BP), cyclohexylbenzene (CHB) and bicyclohexyl (BCH) when the materials were tested in the HDS of DBT.

Iron-doped TiO 2 nanopowders with different doping amounts have been prepared by co-precipitation method followed by heat treatment. The obtained materials were structurally, morphologically and analytically characterized by X-ray diffraction (XRD), FT-Raman spectroscopy, diffuse reflectance spectroscopy (DRS) and energy dispersive X-ray spectroscopy (EDX) coupled to scanning electron microscopy (SEM). XRD analysis revealed the major presence of the anatasa crystalline phase for iron-doped and undoped TiO 2 . SEM confirmed particles sizes among the nanometer scale along with XRD data. The presence of iron ions was validated by EDX-SEM. Diffuse reflectance techniques were carried out to validate the shift of the band edge absorption spectrum of doped TiO 2 nanoparticles towards the visible region and to confirm the presence of iron atoms in the TiO 2 crystal lattice by the resulting variation of the band gap value of the doped materials. Photocatalytic activity of the nanoparticles under UV and visible radiation was evaluated by means of hydroxyl radicals production through indirect estimation using N,N-dimethyl-p-nitrosoaniline (PNDA)photo-discoloration experiments in aqueous dispersion. Samples containing 1.2 and 5.6 weight % Fe exhibited the highest activities in this study for both conditions.

Sequential helminth egg inactivation using a solar driven advanced oxidation process (AOP) followed by chlorine was achieved. The photo-assisted Fenton process was tested alone under different H(2)O(2) and/or Fe(II) concentrations to assess its ability to inactivate Ascaris suum eggs. The effect of free chlorine alone was also tested. The lowest egg inactivation results were found using Fe(II) or H(2)O(2) separately (5 and 140 mmol L(-1), respectively) in dark conditions, which showed about 28% inactivation of helminth eggs. By combining Fe(II) and H(2)O(2) at the same concentrations described earlier, 55% of helminth egg inactivation was achieved. By increasing the reagent's concentration two-fold, 83% egg inactivation was achieved after 120 min of reaction time. Process efficiency was enhanced by solar excitation. Using solar disinfection only, the A. suum eggs inactivation reached was the lowest observed (58% egg inactivation after 120 min (120 kJ L(-1))), compared with tests using the photo-Fenton process. The use of the photo-Fenton reaction enhanced the process up to over 99% of egg inactivation after 120 kJ L(-1) when the highest Fe(II) and H(2)O(2) concentration was tested. Practically no effect on the helminth eggs was observed with free chlorine alone after 550 mg min L(-1) was used. Egg inactivation in the range of 25-30% was obtained for sequential processes (AOP then chlorine) using about 150 mg min L(-1).

Photocatalytic activity of UV+visible-activated nitrogen-doped titanium dioxide catalyst was tested for Escherichia coli ATCC 25922 inactivation. A further aspect of this work was to evaluate the effect of selected parameters (pH, irradiation type, and nitrogen-doped TiO2 concentration) on the disinfection efficiency. The following conditions were tested: complete solar radiation (UV–visible) and visible solar radiation alone, four different concentrations of catalyst (0.0, 0.10, 0.25, and 0.5 mg/mL), and six pH values (6.0, 6.5, 7.0, 7.5, 8.0, and 8.5). Dark conditions were used as control experiments. Disinfection process was enhanced under irradiation when the nitrogen-doped photocatalyst was added into the solution. Lower accumulated energy along with higher inactivation rates was observed in the experiments testing nitrogen-doped TiO2 in comparison with the results obtained on the samples without the catalyst. The disinfection effect of the photocatalyst was found depending on the radiation type. pH value has an important role in the inactivation mechanisms that seems to be related with the cell wall permeability and with particle’s surface charge. pH values 6.5 and 8.0 improve the antimicrobial efficiency of the catalyst tested, whereas pH 7 was identified as the less favorable conditions for microbial inactivation.

Liquefied petroleum gas (LPG) is the main fuel used in the residential sector of the Metropolitan Zone in the Valley of Mexico (MZVM). LPG represents 16% of the total fuel consumption in the MZVM and its demand increased 14% from 1986 to 1999. Propane and butanes, the main compounds of LPG, constituted 29% of all non-methane hydrocarbons found in the air of Mexico City. Some researchers have reported that LPG losses are a significant cause of high ozone concentration in MZVM. Three analyses are carried out in this work to estimate LPG's share of responsibility for MZVM pollution problems. First, the correlation between LPG consumption and three ozone pollution indicators was calculated for the period of 1986–1999. The non-significant correlation of these indicators with LPG consumption in a monthly basis suggests that LPG associated emissions are not the foremost cause of ozone formation. Second, a simulation model is applied to three LPG related emission control strategies to estimate the reduction in the maximum ozone concentration. The most noticeable effect was obtained when both hydrocarbon (HC) and oxides of nitrogen (NOx) emissions associated with LPG use were totally reduced. The other two strategies, that only reduce HC emissions, had a minimum effect on the ozone concentration. Third, organic compounds consumption in air samples captured and irradiated in outdoor smog chambers is used to determine the chemical loss rate of LPG associated species and aromatics in the MZVM. The smog chamber results showed that 70% of propane and n-butane remain at the end of a 1-day irradiation, therefore they remain in the MZVM atmosphere for several days being the reason for the high concentration of these compounds. LPG associated compounds only account for 18% of ozone formed but aromatics contribute 35% to ozone in smog chamber.

Synchrotron techniques have become key components of the toolbox for studying the mechanisms involved in metal(loid) uptake and metabolism in plants. Most widely used techniques in this field include micro-X-ray fluorescence (µXRF) for imaging the distribution of elements in plant tissues and cells and quantifying them, and X-ray absorption spectroscopy (XAS) for determining their chemical forms. Recent advances in terms of spatial resolution, sensitivity and versatility of the sample environment have opened new perspectives for the study of trace elements at the micro- and nanoscale with a minimal perturbation of the sample. Sample conditioning remains a key issue for the study of metals in plants. Cryogenic sample environments allow work on hydrated systems, with a limited risk of metal remobilization and changes in speciation. Still, radiation damage should be monitored carefully, especially for high-flux spectrometers. In addition, progress in software for data analysis has facilitated data mining and integration of results from various techniques. This chapter presents the principle and the basics of data analysis for µXRF imaging and tomography, XAS and micro-Fourier transform infrared spectromicroscopy (µFTIR). Major results obtained on Ni, Cd, Zn, Se, As, Cu, Mn and nanoparticles in hyperaccumulating and nonaccumulating plants are presented. Complementary approaches including histochemical techniques, micro and nanoscopic techniques using electron- or ion beams, and laser ablation coupled with inductively coupled plasma mass spectrometry (ICP-MS) are also presented, and key results reviewed. Finally, there is also great interest in coupling synchrotron techniques, which is possible on more and more beamlines, and also in coupling synchrotron techniques with other approaches such as the ones mentioned above; perspectives in this area are discussed.

This study reports paleomagnetic results from nine localities (22 sites) of the Uairen Formation, the basal and oldest unit of the Roraima sedimentary sequence (Roraima Group) in the Precambrian Guayana shield (southeastern Venezuela). Three distinct natural remanent magnetizations (NRM's), U1N, U1R, and U2, were isolated by alternating-field and thermal demagnetization. U1N and U1R NRM's have mean directions D = 342°, I = 6° (k = 14, α95 = 10°, N = 14 sites) and D = 155°, I = 10° (k = 8, α95 = 17°, N = 8 sites), respectively. Because of their high coercivities (HC) and high (>580 °C) laboratory unblocking temperatures (TUB), it is believed that these NRM's are carried mainly by fine-grained magnetite and (or) hematite. The U2 NRM has D = 338°, I = −7° (k = 5, α95 = 25°, N = 6 sites). U2 is a low-HC (20 mT) and low-TUB (

To investigate whether GnRH regulates LH synthesis during human development, pituitary cells from second trimester fetuses were incubated with [35S]methionine ([35S]met) and [3H]glucosamine ([3H]gln) for 48 h with 0, 10(-9), and 10(-7) mol/L GnRH. Immunoassayable (i) LH was measured in media and cellular lysates, and dual label scintillation analysis was used to quantitate incorporation of radiolabeled precursors into cells, trichloroacetic acid-precipitable proteins, and immunoprecipitated LH subjected to electrophoresis. Exposure of cells to GnRH did not affect cellular uptake or incorporation of precursors into proteins, but specifically increased total (secreted plus cellular) LH synthesis. Both GnRH concentrations significantly increased iLH release and enhanced secreted and cellular [3H]gln-LH. The secretion of [35S] met-LH was stimulated only by 10(-7) mol/L GnRH. The proportion of newly synthesized LH that was secreted and the 3H/35S ratio of secreted and cellular LH were uninfluenced by GnRH. Although basal LH synthesis was not sex dependent, total iLH content and GnRH-stimulated LH translation were greater in cells from females than in those from males. Therefore, GnRH regulates LH synthesis by second trimester fetal human gonadotrophs without influencing the proportion of total radiolabeled LH that is secreted. The existence of a sex difference in total iLH content and GnRH-stimulated LH translation is consistent with the sexual dimorphism in pituitary LH content occurring during human development.

Thin films can be grown in super‐lattice, multilayers and graded form, having each one advantages and disadvantages. The difference between multilayer and graded coatings is the interface. In multilayers the interface is abrupt and in graded coatings it is diffuse. The interface influences many chemical and physical properties of the materials, and its choice depends on the application. Graded coatings have the advantage of having gradual properties such as thermal expansion coefficient and lattice parameter, avoiding adherence problems due to good match between their component materials. In this work the comparison between some properties of coatings grown as multilayer and graded is performed. The materials are produced using the sputtering DC technique because of its facility to control the deposition parameters and generate a slow growth. The target is a disc of titanium and the samples are made of stainless steel 304. The working gases are argon, nitrogen and methane, which are mixed according to the material to be produced, i.e. Ti layer is grown with argon, the TiN film is produced with a mixture of argon and nitrogen, and the TiCN material is obtained mixing argon, nitrogen and methane. These materials are characterized with AFM in order to determine grain size and with XPS studying the chemical composition and performing depth profiles.

Tungsten carbide is considered a very important material used for industrial applications due to their high hardness. In this work the production of W/WC coatings used a repetitive pulsed arc system is employed. During the grown process, the substrate temperature is varied in order to identify the influence of this parameter in the structure, composition and morphology of the coatings. The layer of W is grown to improve the adherence of the WC material on the stainless steel 304. To grown the coatings, it was used a W target in the cathode. The gas of work is methane and as it is knew, to use a gas as precursor for WC production causes the apparition of different phases as WC and W2C. The power supply allows varying the active and passive time of pulses, which in this case have a value of 1 s. the coatings produced are characterized by X‐ray diffraction (XRD), X‐photoelectron spectroscopy (XPS) and scanning probe microscopy (SPM). All of these techniques allow determining properties such as chemical composition, structure, stoichiometry, thickness and grain size.

This study was motivated by the need to develop new methods to predict tumor response to chemotherapeutic agents. Using implantable cell-growth chambers, squamous carcinoma cells from head and neck tumors were xenografted into the peritoneal cavity of immunocompetent rats. Animals were divided into control and treatment groups. The treatment groups received intravenous cisplatin (CDDP) or 5-fluorouracil (5-FU) v normal saline solution for the control. Animals from each group were randomly selected and killed on days 3, 5, and 7 postimplantation. The chambers were retrieved, the media aspirated, and cells counted. Exponential growth curves were derived for the control and treatment groups. Statistically significant growth inhibition was observed for both treatment arms, compared with controls. This method of chemosensitivity testing proved to be inexpensive and reliable, and demonstrated tumor cell killing by 5-FU and CDDP.

Quercetin exhibits antitumor activity. We investigated the effect of quercetin on the in vitro and in vivo growth of two squamous cell carcinoma cell lines and a normal human lung fibroblast-like cell line. The in vivo effect was evaluated using implantable cell growth chambers implanted subcutaneously in immunocompetent rats. Quercetin was injected intraperitoneally, and multiple dosages were tested. Cells were counted on days 1, 3, 5, and 7, and growth curves were constructed. Quercetin caused inhibition of growth in both squamous cell carcinoma lines. Effect on the fibroblast-like human lung cells was noted only at the maximum concentration. Significant growth inhibition of squamous cell carcinoma was observed in implantable cell growth chambers retrieved 3 days after quercetin treatment. Quercetin appears to possess a cytotoxic effect on squamous cell carcinoma of head and neck origin both in vivo and in vitro. The inhibitory effect on malignant cells appears to be selective and dose-dependent.

The radiation dose in the vicinity of metal mandibular implants was measured using lithium fluoride (TLD-100) thermoluminescent dosimeters. Dosimeters were positioned in contact with Vitallium and stainless steel (AO) reconstruction plates. Simple transmission was measured with a solid state detector removed from the implant at a depth of 2.5 cm in a polystyrene phantom. The measurements were made for a 6 mV photon beam from a linear accelerator. At points in front of, but in contact with the metal implants, the dose was greater by 23 percent for Vitallium and 17 percent for stainless steel than that with no implant. At contact behind the implant, the dose was reduced considerably: 14 percent for Vitallium and 13 percent for stainless steel. At remote points behind the implant, the dose was reduced due to attenuation.