Search Results
You are looking at 1 - 10 of 15 items for
- Author or Editor: T. Martins x
- Refine by Access: All Content x
Abstract
The Californium User Facility for Neutron Science has been established at Oak Ridge National Laboratory (ORNL). The Californium Use Facility (CUF) is a part of the larger Californium Facility, which fabricates and stores compact252Cf neutron sources for worldwide distribution. The CUF can provide a cost-effective option for research with252Cf sources. Three projects at the CUF that demonstrate the versatility of252Cf for biological and biomedical neutron-based research are described: future establishment of a252Cf-based neutron activation analysis system, ongoing work to produce miniature high-intensity, remotely afterloaded252Cf sources for tumors therapy, and a recent experiment that irradiated living human lung cancer cells impregnated with experimental boron compounds to test their effectiveness for boron neutron capture therapy.
Abstract
Rare earth picrate complexes with L-leucine (Leu) were synthesized and characterized. Elemental analysis (CHN), EDTA titrations and thermogravimetric data suggest a general formula RE(pic)32Leu⋅5H2O (RE=La–Lu, Y and pic=picrate). IR spectra indicate the presence of water and suggest that L-leucine is coordinated to the central ion through the nitrogen of the aminogroup. The absorption spectrum of the solid Nd compound indicates that the metal-ligand bonds show a weak covalent character. Emission spectra and biexponential behavior of the luminescence decay of the Eu compound suggest the existence of polymeric species. Thermal analysis results indicate that all the compounds present a similar behavior, with five major thermal decomposition steps. The final products are rare earth oxides. A slow heating rate is necessary to observe all decomposition steps.
The parasitization behaviour of Chelonus oculator (F.), egg-larval parasitoid of noctuid lepidopteran species, has been studied under laboratory conditions, using Ephestia kuehniella Zeller as host, at four different temperature levels (10,20, 30 and 40±1 °C) and five densities of host eggs (50,100,150, 200 and 250). A significant effect of temperature and parasitism density was observed. At 10 °C, there was no parasitism, whilst at 40 °C it was very low; presenting adequate values at the two other temperatures (20 and 30 °C). With regard to these facts, the functional responses of this parasitoid species were adjusted and we noted that they display Holling type III. Estimating the handling times from the respective mathematical expressions, we obtained 10.944 and 15.250 min, at 20 and 30°C, respectively. These values are considerably higher than the respective times obtained by direct observation, 0.597 and 0.560 min for these temperatures (this difference is due to the fact that in the first case, unlike the second one, the time used for the search of the host is also included). The results obtained from the parasitization behaviour of Ch. oculator are discussed, also considering it as a candidate biological control agent against Spdoptera exigua (Hübner), beet armyworm, with a view to its possible use in greenhouse crops in Spain.
The aim of the present study was to compare running economy between competitive and recreational level athletes at their individual ventilatory thresholds on track and to compare body composition parameters that are related to the individual running economy measured on track. We performed a cross-sectional analysis of a total 45 male runners classified as competitive runners (CR; n = 28) and recreational runners (RR; n = 17). All runners performed an incremental test on treadmill until voluntary exhaustion and at least 48 h later a 2 × 2000 m test at indoor track with intensities according to ventilatory threshold 1, ventilator threshold 2. During the running tests, athletes wore portable oxygen analyzer. Body composition was measured with Dual energy X-ray absorptiometry (DXA) method. Running economy at the first ventilatory threshold was not significantly related to any of the measured body composition values or leg mass ratios either in the competitive or in the recreational runners group. This study showed that there was no difference in the running economy between distance runners with different performance level when running on track, while there was a difference in the second ventilatory threshold speed in different groups of distance runners. Differences in running economy between competitive and recreational athletes cannot be explained by body composition and/or different leg mass ratios.
Abstract
The tomato culture demands large quantities of mineral nutrients, which are supplied by synthetic fertilizers in the conventional cultivation system. In the organic cultivation system only alternative fertilizers are allowed by the certifiers and accepted as safe for humans and environment. The chemical composition of rice bran, oyster flour, cattle manure and ground charcoal, as well as soils and tomato fruits were evaluated by instrumental neutron activation analysis (INAA). The potential contribution of organic fertilizers to the enrichment of chemical elements in soil and their transfer to fruits was investigated using concentration ratios for fertilizer and soil samples, and also for soil and tomato. Results evidenced that these alternative fertilizers could be taken as important sources of Br, Ca, Ce, K, Na and Zn for the organic tomato culture.
Summary
Rare earth picrate (RE) complexes with L-lysine (Lys) were synthesized and characterized. Elemental analysis (CHN), EDTA titrations and thermogravimetry data suggest a general formula RE(pic)32Lys2H2O, where RE=La-Lu (without Pm) and Y, pic=picrate). IR spectra suggest that Lys is coordinated to the central ion through the nitrogen of the α-amino group. Parameters obtained from the absorption spectrum of the Nd compound indicated that the metal-ligand bonds are essentially electrostatic. Emission spectrum and biexponential behavior of the luminescence decay of the Eu compound suggest the existence of polymeric species. Thermogravimetric/derivative thermogravimetric (TG/DTG) and differential scanning calorimetry (DSC) curves of all complexes are very similar, with five events. The final products are the corresponding rare earth oxides and their X-ray diffraction patterns are identical to the calcinated oxides.</o:p>
Abstract
Inclusion complex between the essential oil of Mentha x villosa Hudson and β-cyclodextrin, with a 1:9 mass/mass oil–β-cyclodextrin ratio was prepared by co-precipitation and kneading methods in a hydroethanolic medium. The GC/MS analysis showed a total volatile content of 99.5% in the Mentha x villosa oil. The characterization of the complex involved the analysis of the original essential oil, the surface and the total extracted oils. Among 28 detected compounds in the original essential oil, 13 are monoterpenes and 10 sesquiterpenes, furthermore, piperitenone-oxide is the major component (35.4%). 12 compounds were totally and 11 partially complexed, 3 have been adsorbed only on the surface of the β-CD and 2 have not been detected neither in the surface oil nor in the complexed oil. A 13.6% encapsulation efficiency was observed, while the total oil and volatiles retention was 15 and 77%, respectively. Non-parametric statistic analysis of the data showed that the profile of the volatiles were not significantly different comparing the original oil and the complexed oil (p>0.04). The results of thermogravimetry-mass spectrometry and XRD analysis have proven the inclusion complex formation between the essential oil and cyclodextrin.
Abstract
Tomato is amongst the most consumed vegetables in the world, not only for its culinary versatility but also for its high nutritional value. In the last years, consumers have shown an increased concern regarding food origin and safety. The organic tomato production has been a promising alternative for the consumer offering a safer food in relation to environmental, social and nutritional aspects. This study assessed the chemical composition of tomato seeds produced in both conventional and organic systems by INAA. The results showed significant differences (p≤0.05) in the mass fractions of Br, Cs, Eu, Fe, K, Mo, Na, Rb and Sm between both systems, indicating influence of the crop management adopted in the different tomato production systems.
Abstract
The agricultural supplies used in the organic system to control pests and diseases as well as to fertilize soil are claimed to be beneficial to plants and innocuous to human health and to the environment. The chemical composition of six agricultural supplies commonly used in the organic tomato culture, was evaluated by instrumental neutron activation analysis (INAA). Results were compared to the maximum limits established by the Environment Control Agency of the São Paulo State (CETESB) and the Guidelines for Organic Quality Standard of Instituto Biodinâmico (IBD). Concentrations above reference values were found for Co, Cr and Zn in compost, Cr and Zn in cattle manure and Zn in rice bran.
Immobilization of ethylenesulfide on silica surface using acid and base catalysts
Adsorption and thermodynamic data
Abstract
The reaction of cyclic ethylene sulfide with 3-aminopropyltrimethoxysilane resulted in a new silylating agent, which was anchored onto a silica surface via the sol-gel procedure using hydrochloric acid or ammonium hydroxide as acid or base catalysts, respectively. Both organofunctionalized surfaces have the ability to adsorb divalent cations from aqueous nitrate solution. Through calorimetric titrations, the thermodynamic data of cation-basic center interactions were obtained. Exothermic enthalpy values were obtained for all interaction processes. The calculated free Gibbs energy is in agreement with the spontaneity of the reactions and the positive entropy values for all reactions are favorable for these systems.
