Interlayer expansion of dimethyl ditallowylammonium montmorillonite as a function of 2-chloroaniline adsorption

The expansion behaviour of an organically modified montmorillonite during the adsorption of increasing amounts of an organic pollutant: 2-chloroaniline (2-CA). The organophilic montmorillonite, a commercial product, was obtained exchanging the inorganic cation with dimethyl ditallowylammonium ions (DMDTA). 2-CA was added to the organoclay, starting from 193.9 ppm up to 23,531.7 ppm going through twenty-two steps of growing quantities of 2-CA. For each of these twenty-two steps – corresponding to a range of adsorbed 2-CA (C_s) between 0.029 mol/kg (grams of 2-CA per kg of organoclay) and 2.763 mol/kg – the basal spacings were determined.The adsorption isotherm was performed according to ASTM D 4646-87 Standard and, by comparing the experimental C_s data with the corresponding d₀₀₁ values, the basal expansion of the polluted organoclay is characterized by a steep rise for the first steps of adsorption of 2-CA (concentration in water at equilibrium C_w < 0.00373 mol/L), then the d₀₀₁ remains almost constant up to the higher amounts of pollutant adsorbed.The 001 reflections are sharper, their intensity higher, and up to four orders of 00l reflections are observed as the uptake of 2-CA increased. Since in aqueous solution the staking of organoclay platelets is poorly ordered, the observed behaviour may be partially explained by the 2-CA sorbed on the external surface of the clay mineral particles, which brings the silicate layers together.Finally, a tentative interpretation of the adsorption phenomena was carried out by fitting the experimental data according to the most common theoretical models: Freundlich, Langmuir, Dual Mode and Dual Langmuir Model.     

Efficient MILP formulations for the simultaneous optimal peptide tag design and downstream processing synthesis

Novel and efficient linear formulations are developed for the problem of simultaneously performing an optimal synthesis of chromatographic protein purification processes, and the concomitant selection of peptide purification tags, that result in a maximal process improvement. To this end, two formulations are developed for the solution of this problem: (1) a model that minimizes both the number of chromatographic steps in the final purification process flow sheet and the composition of the tag, by use of weighted objectives, while satisfying minimal purity requirements for the final product; and (2) a model that attempts to find the maximal attainable purity under constraints on the maximum number of separation techniques and tag size. Both models are linearized using a previously developed strategy for obtaining optimal piecewise linear approximations of nonlinear functions. Proposed are models to two case studies based on protein mixtures with different numbers of proteins. Results show that the models are capable of solving to optimality all the implemented cases with computational time requirements of under 1 s, on average. The results obtained are further compared with previous nonlinear and linear models attempting to solve the same problem, and, thus, show that the approach represents significant gains in robustness and efficiency. © 2009 American Institute of Chemical Engineers AIChE J, 2009     

Silver coated lead coins: An appraisal of ancient technology

In this paper we report some experimental archaeology research consisting in applying a two-step electrochemical displacement procedure in order to simulate the fabrication route which could have been used by coin counterfeiters of the 3rd century BC for the silvering of a Pb substrate. A material characterisation of a relevant archaeological item [5] has revealed a bi-layer coating, with a Cu interlayer and an Ag top layer. SEM morphology and XRD textures of the Cu and Ag layers cannot be explained with thermal or mechanical procedures and exhibit typical features of electrochemical displacement processes. We replicated a coating process with materials that are documented for the historical period of interest and that lead to the formation of a bi-layer coating exhibiting essentially the same morphological and structural properties of the archaeological object. The direct displacement coating of Pb with Ag has been shown not to be feasible with period chemicals, whilst the duplex coating could be achieved by sequential use of a Cu(II)-acetate solution, displacing Pb, and of a Ag(I) solution obtained by dissolving AgCl in dilute ammonia. The coatings obtained have been characterised by SEM; XRD and colorimetry. The double displacement process yields a cauliflower-like agglomerate structure, showing close similarities with the morphology of residual white-metal coating of the coin. Cu and Ag displacement layers exhibit a typical (111) texture that cannot be reconciled with that obtained by thermal or mechanical plating techniques and that matches the texture found in the counterfeit coin. The spectral reflectivity and colorimetric parameters of the final Ag layer perfectly match those of bulk Ag.     

The mu-opioid receptor is necessary for [D-Pen2,D-Pen5]enkephalin-induced analgesia

Endomorphin-1 and -2, recently isolated endogenous peptides specific for the mu-opioid receptor, inhibited Ca2+ channel currents with EC50 of 6 and 9 nM, respectively, in NG108-15 cells transformed to express the cloned rat mu-opioid receptor. On the other hand, they elicited no response in nontransfected NG108-15 cells. It is concluded that endomorphin-1 and -2 induce Ca2+ channel inhibition by selectively activating the mu-opioid receptor.     

Creative destruction of computing systems: analysis and modeling

The paper analyzes the problem of rational replacement of computing systems. Such systems, especially high-performance computers, are expensive, but quickly become obsolete. A system analysis of the replacement problem is provided and the relevant modeling problems are identified and studied. The obtained results give certain rules for calculating the optimal lifetime of computing systems, which are based on the given rates of technological change in the related computer industry. Two simulation examples estimate the optimal lifetime of PCs and high-performance computers in the current US economy. The results are in good agreement with other recommendations and existing business practice.     

Applications of Brazilian pine-fruit shell in natural and carbonized forms as adsorbents to removal of methylene blue from aqueous solutions--kinetic and equilibrium study

The Brazilian pine-fruit shell (Araucaria angustifolia) is a food residue, which was used in natural and carbonized forms, as low-cost adsorbents for the removal of methylene blue (MB) from aqueous solutions. Chemical treatment of Brazilian pine-fruit shell (PW), with sulfuric acid produced a non-activated carbonaceous material (C-PW). Both PW and C-PW were tested as low-cost adsorbents for the removal of MB from aqueous effluents. It was observed that C-PW leaded to a remarkable increase in the specific surface area, average porous volume, and average porous diameter of the adsorbent when compared to PW. The effects of shaking time, adsorbent dosage and pH on adsorption capacity were studied. In basic pH region (pH 8.5) the adsorption of MB was favorable. The contact time required to obtain the equilibrium was 6 and 4h at 25 degrees C, using PW and C-PW as adsorbents, respectively. Based on error function values (F(error)) the kinetic data were better fitted to fractionary-order kinetic model when compared to pseudo-first order, pseudo-second order, and chemisorption kinetic models. The equilibrium data were fitted to Langmuir, Freundlich, Sips and Redlich-Peterson isotherm models. For MB dye the equilibrium data were better fitted to the Sips isotherm model using PW and C-PW as adsorbents.     

Recombinant anti-human melanoma antibodies are versatile molecules

The low cost, high versatility, and reliable production of bacterially produced recombinant antibody fragments speeds up the development of tumor-targeting agents. High-quality recombinant anti-melanoma antibodies are much sought after in the scientific community. We cloned the murine antibody 225.28S, currently used in radioimmunoimaging of human melanoma lesions, in single-chain Fv configuration (scFv) for soluble expression in bacteria. The recombinant antibody fragment conserved the binding specificity of the parental antibody. In order to arm the scFv(225.28S) with biologically useful effector functions, we developed vectors for soluble expression of scFv(225.28S) in bacteria that allow both covalent and noncovalent chemical antibody modification at positions that do not interfere with antigen binding. An expression vector was developed that appends a cysteine residue at the C-terminal extremity of the recombinant antibody, thus allowing reaction with thiol-specific reagents, including 99mTc labeling, at a position that does not interfere with antigen binding. The scFv(225.28S) was also successfully expressed with a casein kinase II substrate tag that enables efficient and stable 32P labeling. For noncovalent antibody modification, we developed an expression vector that appends the human calmodulin gene at the C-terminal extremity of scFv(225.28S). The calmodulin domain is poorly immunogenic and can be targeted with chemically modified high-affinity calmodulin ligands. The recombinant anti-human melanoma antibodies described in this article should prove useful "building blocks" for the development of anti-melanoma diagnostic and therapeutic strategies.     

Toxicological and chemical characterization of organic micropollutants in river po waters (Italy)

River Po waters were collected at the end of the drainage basin, extracted by means of XAD-2 resins and tested for toxicity on aquatic organisms (Daphnia magna and Selenastrum capricornutum) and for mutagenicity with a modified Ames test. The extracts were analyzed by HRGC/FID and selective detectors for the determination of the most common classes of toxic compounds. The relationships between toxicological responses and analytical results are discussed.     

Nanostructured phenolic matrices: Effect of different nanofillers on the thermal degradation properties and reaction to fire of a resol

In this work, the effect of 6 different fillers as a nanomodifier of phenolic matrix was evaluated in thermal stability and reaction to fire. The chosen nanoparticles were montmorillonite, silica, carbon black, and 3 carbides—boron, silicon, and zirconium carbides. The nanofillers were mechanically dispersed in the matrix, and the dispersion and distribution of the nanosized particles in the matrix was evaluated by transmission electron microscopy. The thermal stability of nanocomposites was investigated by thermogravimetric analysis both in nitrogen and in air while the thermal combustion properties were measured using a microscale combustion calorimeter. The experimental data highlighted the remarkable effects of nanoboron carbide on the thermal properties it can confer to the phenolic matrix. Rheological behavior of the blends was also investigated to evaluate the effect of the different fillers on the viscosity of the nanostructured matrices.