analysis was done to determine the temperatures of thermal reactions, phase
transformations or melting reaction during continuous heating. These reactions
are a direct response to the steel composition and to the sintering atmosphere.
Simultaneous thermal analysis TG-DTA (STA) shows up the sintering behaviour
of sintered low prealloyed chromium steels and their peculiarities. Given
the high oxygen affinity of chromium, graphite additions can modify their
thermal reactions, and hence the sintering behaviour of the steel. Evidence
is given of the effect of carbon on the sintering process and the nature of
Authors:J. Dweck, L. Morais, M. Fonseca, V. Campos, and P. Büchler
Aiming the use of the sewage sludge produced in one of the largest Brazilian wastewater treatment stations as a raw material
for the ceramic industry, the sintering process of the ashes produced from its calcination was evaluated by heating microscopy
thermal analysis (HMTA). From the microprocessed images, a method was developed to obtain HMTA dimensional change curves as
a function of temperature, equivalent to those usually obtained from dilatometers or by thermomechanical analysis (TMA). The
final product after sintering at 1050°C, characterized by X-ray fluorescence spectrometry, scanning electron microscopy and
X-ray dispersive energy, indicates the presence of a vitreous phase containing phosphorus, which explains the good sintering
properties of the studied calcined sludge, as shown from its HMTA dimensional change curve.
Authors:L. Campos, A. Amaral, N. Colas-Linhart, and E. Hindié
Thyroid cells are arranged in spheres called follicles of different sizes, in which most of the iodine in the body concentrates.
For dose assessment in follicles, it is necessary to consider specific emissions of iodine isotopes in the calculation. Hence,
the aim of this work was to evaluate the contribution of 131I and short-lived iodines to the absorbed dose in thyroid cells. Thus, the interaction of emissions from isotopes with follicles
was carried out using the MCNP4C code. The results showed that the contribution of short-lived iodines for absorbed dose per
disintegration is about 70%.
Authors:M. S. Casare, P. Spencer, L. A. Campos, and N. Nascimento
Crotoxin is a 23 kDa neurotoxin from Crotalus durissus terrificus and is composed of a 9 kDa acidic subunit (crotapotin) and a 14 kDa basic subunit (phospholipase A2). Crotamine is 4882 Da, basic polypeptide with myotoxic activity. These toxins, when submitted to gamma-rays, in aqueous
solution, present structural modifications, preserving their immunogenic properties. In the present work, we investigated
some structural modifications on both crotoxin and crotamine after gamma-radiation using various doses, in the presence or
not of “scavenger” substances. Our results indicate that irradiation leads to progressive changes in the structure of the
toxin, which could explain the lower toxicity observed.
Authors:J. M. Navarrete, J. Campos, T. Martínez, and L. Cabrera
After the Chernobyl accident in April 1986, Mexico imported from one European country a shipment of 28,000 tons of milk powder contaminated with the fission product 137Cs. Since then, the local authorities of Public Health have established as a compulsory condition to obtain through gamma-spectroscopy a certificate of no radioactive contamination either to imported or exported foodstuffs. But at the same time, the absence of long-lived, gamma-emitters fission products is certified, it is also possible to find the concentration of the important trace element K in foodstuffs, by the peak of 1461 keV from 40K, invariably present in the gamma-spectra. Taking advantage of the fact that it does not require any previous manipulation of the sample, this paper describes the general procedure in milk powder or any other foodstuff.
Authors:E. Orozco-Guareño, A. Campos Almaraz, G. Reyes, L. López-Ureta, and A. Gonzalez-Alvarez
The thermal behavior
of hydrogels synthesized by solution polymerization between acrylamide, acrylic
acid and diglycidyl acrylate (DGA) as a crosslinking agent was investigated.
The structure of the hydrogel can be tightly controlled with the reaction
temperature. This method produces a new type of hydrogels, which exhibit well
defined structures at various scales of length simultaneously. These multi-structured
hydrogels are hydrophilic, elastic, water insoluble, and soft polymers with
an anisotropic optical response. The structure was observed by scanning electron
microscopy (SEM), polarized light microscopy (PLM) and macroscopic visualization
(CCD camera). In addition, structural transitions in the hydrogels were monitored
by temperature modulated differential scanning calorimetry (TMDSC). Severe
heating tests in an adiabatic oven were performed to analyze decomposition
of the material. Fourier transform infrared (FTIR) spectroscopy was used to
qualitatively analyze the hydrogels samples exposed to a sudden thermal treatment.
Authors:J. Baptista, D. Vieira, A. Galisteo Júnior, O. Higa, M. Casare, C. Yonamine, P. Caproni, L. Campos, H. de Andrade Júnior, P. Spencer, and N. Nascimento
In this work, the authors investigated the immunological behavior of bothropstoxin-I (BTHX-1), before and after irradiation
process, and also the influence of scavengers substances on protein alterations induced by free radical production. Structural
modifications were investigated by SDS-PAGE in reducing or non-reducing conditions. In vitro cytotoxicity assay was performed
to test average toxic activities of BTHX-I. BALB/c Isogenic mice were immunized with irradiated or non-irradiated (native)
forms of BTHX-I and antibody titers and isotypes were determined by ELISA method. Expression of murine cytokines was analyzed
by using expression data obtained by quantitative real-time PCR (qPCR) assays. The results indicate that irradiation of proteins
leads to significant structural modifications, and also changes the cytokines profile during immunization process, regarding
a suitable approach to new immunogenic production.
Authors:F.A. Rodríguez-Zaragoza, M. Ortiz, F. Berrios, L. Campos, A. de Jesús-Navarrete, J. Castro-Pérez, A. Hernández-Flores, M. García-Rivas, F. Fonseca-Peralta, and E. Gallegos-Aguilar
Banco Chinchorro is the largest reef in the Mexican Caribbean. Historically, spiny lobster, queen conch and over 20 other reef species have been exploited here. Multispecies intervention management from an ecosystem perspective has been developed in this area; however, an assessment of the effects of such practices on ecosystem health is required. Five quantitative trophic models were constructed using Ecopath with Ecosim. The results show that, in terms of biomass, benthic autotrophs are the dominant group in all communities. Ecosystem Network Analysis indices showed that Cueva de Tiburones was the most mature, developed, complex and healthy subsystem, but, El Colorado and La Baliza were the subsystems most resistant to disturbances. The fisheries mainly concentrate on primary (La Baliza and Cueva de Tiburones sites) and secondary consumers (La Caldera, Chancay, and El Colorado). The greatest propagation of direct and indirect effects, estimated by Mixed Trophic Impacts and Ecosim simulations, were generated by the benthic autotrophs, small benthic epifauna, benthic-pelagic carnivorous fish and benthic carnivorous fish, among others. In contrast, the System Recovery Time showed different patterns among subsystems, indicating several compartments that reduce resilience. Considering the structure, dynamics, trophic functioning and ecosystem health of Banco Chinchorro, its ecological heterogeneity highlights the need for the design of a specific (by subsystem) management strategy, particularly because different species or functional groups present greater sensitivity to human interventions in each community.