The k 0 and relative INAA methods to determine elements in entire archaeological pottery objects

The advantages of instrumental neutron activation analysis applied to archaeological ceramics have been enhanced through the analysis of entire objects, using both the k ₀ method and the relative method, respectively, to determine the concentrations of chemical elements in aliquots of replicate objects used as comparators and in the sample object. Twenty-two chemical elements of archaeological importance were measured in mud figurines from Caral civilization (5000 year BC), irradiated inside a well-characterized radial channel facility of the nuclear research reactor at IPEN, Peru. The results showed less than 10 % of bias for most of the elements.     

Specific Recognition of β-Galactofuranose-Containing Glycans of Synthetic Neoglycoproteins by Sera of Chronic Chagas Disease Patients

Chagas disease (CD) can be accurately diagnosed by detecting Trypanosoma cruzi in patients’ blood using polymerase chain reaction (PCR). However, parasite-derived biomarkers are of great interest for the serological diagnosis and early evaluation of chemotherapeutic efficacy when PCR may fail, owing to a blood parasite load below the method’s limit of detection. Previously, we focused on the detection of specific anti-α-galactopyranosyl (α-Gal) antibodies in chronic CD (CCD) patients elicited by α-Gal glycotopes copiously expressed on insect-derived and mammal-dwelling infective parasite stages. Nevertheless, these stages also abundantly express cell surface glycosylphosphatidylinositol (GPI)-anchored glycoproteins and glycoinositolphospholipids (GIPLs) bearing nonreducing terminal β-galactofuranosyl (β-Galf) residues, which are equally foreign to humans and, therefore, highly immunogenic. Here we report that CCD patients’ sera react specifically with synthetic β-Galf-containing glycans. We took a reversed immunoglycomics approach that entailed: (a) Synthesis of T. cruzi GIPL-derived Galfβ1,3Manpα-(CH₂)₃SH (glycan G29_SH) and Galfβ1,3Manpα1,2-[Galfβ1,3]Manpα-(CH₂)₃SH (glycan G32_SH); and (b) preparation of neoglycoproteins NGP29b and NGP32b, and their evaluation in a chemiluminescent immunoassay. Receiver-operating characteristic analysis revealed that NGP32b can distinguish CCD sera from sera of healthy individuals with 85.3% sensitivity and 100% specificity. This suggests that Galfβ1,3Manpα1,2-[Galfβ1,3]Manpα is an immunodominant glycotope and that NGP32b could potentially be used as a novel CCD biomarker.     

Development of a chemiluminescent ELISA and a colloidal gold-based LFIA for TNT detection

To identify the explosive used in a terrorist attack, or to obtain an early sign of environmental pollution it is important to use simple and rapid assays able to detect analytes at low levels, possibly on-site. This is particularly true for TNT (2,4,6-trinitrotoluene), one of the most employed explosives in the 20th century and at the same time, because of its toxicity, a well known pollutant. In this work we describe the development of an indirect competitive ELISA with chemiluminescent detection (CL-ELISA) and of a lateral-flow immunoassay (LFIA) based on colloidal gold nanoparticle labels. A commercially available monoclonal antibody was used and 13 specially synthesized conjugates were tested. We optimized the assay by determining the optimal concentration of monoclonal antibody and conjugates and the influence of various non-specific factors such as: tolerance to organic solvents at different concentrations, the washing and competitive step time, and the cross-reactivity with related compounds. The sensitivity and reproducibility of the CL-ELISA were good (LOD and IC₅₀ values in the ng mL⁻¹ range, and CV value about 7%). It has been applied to real samples of various materials involved in a controlled explosion of an “improvised explosive device”. Three extraction procedures were tested on these samples, all employing methanol as the solvent. The lateral flow immunoassay (LFIA), developed by using the same immunoreagents, reached a detection limit of 1 μg mL⁻¹ when tested on the same samples analysed by CL-ELISA.      

Breaking a secure communication scheme based on the phase synchronization of chaotic systems

A security analysis of a recently proposed secure communication scheme based on the phase synchronization of chaotic systems is presented. It is shown that the system parameters directly determine the cipher text waveform, hence it can be readily broken by system parameter estimation from the cipher text signal.     

Coulomb effects in low energy fission

The structures in the total kinetic energy (TKE) distributions in cold fission of²³⁴U and²³⁶U are interpreted in terms of the Coulomb interaction energy (C) between fragments at the scission point. The maximal value ofC, C _max, corresponding to the most compact scission configuration, is calculated for several mass fragmentations. It is shown that withQ being constant,C _max increases if one increases the charge asymmetry for a given primary fragmentation. This condition produces oscillations with a period of approximately 5 amu ofC _max as a function of the light fragment mass which are correlated with the observed oscillations of the maximal value of TKE. Moreover, the enhancement of the yields of the more asymmetric charge fragmentation for a given fragmentation is explained.     

Aspects of electronic transport in YBaCo4O7+δ pellets

YBaCo₄O_7+δ powders were obtained by standard solid state reaction und their structural, morphological and electrical properties carefully analyzed. The X-ray powder diffraction patterns showed reflexes corresponding to a pure hexagonal structure (space group P6₃mc). The lattice parameters resulted to be very close to those reported in the literature for high-quality samples. Raman spectra at room temperature allowed for identifying bands associated with vibrating modes of CoO₄ and Y₂O₆ in tetrahedral and octahedral coordination, respectively. Additional bands, which seemed to stem from CoO in octahedral coordination, were also clearly identified. The dependence of the resistivity on temperature showed a semiconducting-like behavior and no indication of structural phase transition was observed up to temperatures as low as 20 K. The electronic transport mechanism in this material was analyzed within the framework of standard models as thermal activation, polaronic-type conductivity or Mott variable-range hopping. Contrary to some reports in the literature in which thermal activation was reported to be the main transport mechanism, careful analysis of the obtained resistivity data (this work) favored the variable-range hopping conduction model. Certainly, the experimental data recorded in a wide temperature range were well described by the function ρ(T) = ρ₀exp[(T^*/T)^1/4]. The fit procedure yielded a temperature scale T^* ～ 10⁶ K, similar to that found in other transition metal oxides. This parameter, in turn, allowed for estimating the density of states at the Fermi level N(E_F) for this compound.     

Branch-and-price approach for the multi-skill project scheduling problem

This work introduces a procedure to solve the multi-skill project scheduling problem (MSPSP) (Néron and Baptista, International symposium on combinatorial, optimization (CO’2002), 2002). The MSPSP mixes both the classical resource constrained project scheduling problem and the multi-purpose machine model. The aim is to find a schedule that minimizes the completion time (makespan) of a project, composed of a set of activities. In addition, precedence relations and resources constraints are considered. In this problem, resources are staff members that master several skills. Thus, a given number of workers must be assigned to perform each skill required by an activity. Practical applications include the construction of buildings, as well as production and software development planning. We present a column generation approach embedded within a branch-and-price (B&P) procedure that considers a given activity and time-based decomposition approach. Obtained results show that the proposed B&P procedure is able to reach optimal solutions for several small and medium sized instances in an acceptable computational time. Furthermore, some previously open instances were optimally solved.     

The corrections for non-ideal behavior of the epithermal neutron spectrum and the restitution of the simplicity in parametric activation analysis

The errors occurred when α, the parameter that accounts for the non-ideal behavior of the epithermal flux, are neglected, have been evaluated for the determination of twenty elements in biological materials, using. gold and sodium comparators, and zirconium to measure the thermal to epithermal flux ratio (f). Sodium allows the determination of 15 elements, and up to 18 elements can be determined in positions relatively well thermalized by the simultaneous use of gold and sodium comparators, in all the cases with errors ≦2%, when α is not considered. Results obtained for reference materials are presented.     

Imidazolinone herbicides in strongly acidic media: Speciation and electroreduction

From UV-visible measurements and potentiometric titrations it follows that the lowest pK values (pK₁) of imidazolinone herbicides correspond to the simultaneous protonation/dissociation equilibria of both the pyridinic (or quinolinic) nitrogen and the carboxyl group, the following pK (pK₂) to the imminium nitrogen and the basic pK (pK₃) to the dissociation of the imido nitrogen. Below pH 6 and down to pH c.a. 2.5, the dominant form of the herbicide is a double ion having both positive and negative charges, this being important in discussing the effect of pH in the natural dynamics of imidazolinone herbicides, especially in their soil sorption. Electrochemical studies of the reduction of the herbicides were made on mercury and carbon electrodes in strongly acidic media (0.1 to 2.7 M H₂SO₄) as well up to pH 7. The reduction signals were all attributed to the reduction of the imidazolinone ring except the second peak/wave that was found to have originated by the reduction of the pyridine/quinoline ring. A signal observed in strongly acidic media and at highly negative overpotentials was attributed to the reduction of the imidazolinone ring of the product of the previous reduction in a process consisting of two reversible electron transfers followed by a protonation reaction.     

Regioselective formation of N-alkyl-3,5-pyrazole derived ligands. A synthetic and computational study

New N-alkyl-3,5-pyrazole derived ligands were synthesized by reaction between 3,5-pyrazole derived ligands and the appropriate haloalkane in toluene or THF using NaOEt or NaH as base. When the precursor ligand bears a pyridyl substituent the alkylation reaction presents a large regioselectivity. Theoretical calculations have been carried out to rationalize the experimental observations. It has been shown that regioselectivity is governed by the formation of Na⁺-pyrazolide chelate complexes.