Ethyl magnesium bromide as an efficient anionic initiator for controlled polymerization of ε-caprolactone

The ring-opening polymerization of ε-caprolactone initiated by ethyl magnesium bromide was studied. Because ring-opening polymerization is extremely fast in the monomer phase, we focused on solution polymerization in toluene. The solution polymerization of ε-caprolactone was characterized by the linear dependence of degree of conversion on polymerization time, which we described by a first-order kinetic equation. The molar mass, determined by SEC using a light scattering detector, was in agreement with that calculated from the degree of conversion attained and the ratio of ε-caprolactone to ethyl magnesium bromide. On this basis, we propose a mechanism for the effect of ethyl magnesium bromide on ε-caprolactone polymerization and provide evidence for this mechanism by isolating a novel stable complex of magnesium bromide with ε-caprolactone.     

Pronase-immobilized enzyme reactor: an approach for automation in glycoprotein analysis by LC/LC-ESI/MSn

An automated analytical approach is proposed for simultaneous characterization of glycan and peptide moieties in pronase-generated glycopeptides. The proposed method is based on the use of a new pronase-immobilized enzyme reactor for the on-line rapid digestion of the target glycoprotein. By coupling the bioreactor to a Hypercarb chromatographic trap column, on-line selective glycopeptide enrichment prior to normal-phase liquid chromatography-mass spectrometry was obtained. A detailed study was carried out for integration and automation of each phase of the proposed analytical procedure. On-line digestion allowed extensive cleavage of the model protein (ribonuclease B), yielding to glycopeptides with peptide moieties up to eight amino acids, carrying the Man5-Man9 N-glycans each, selectively resolved on an Amide-80 column. The use of a linear ion trap instrument resulted in efficient ion capture and led to MS3 acquisition times and spectra quality similar to those for MS2, allowing the unambiguous identification of glycan (MS2) and peptide (MS3) sequences. The proposed procedure reduces the glycoprotein analysis time from approximately 3 days, as in most of the traditional off-line methods, to approximately 1 h.     

Organization of nanoparticles on hard substrates using block copolymer films as templates

We present a technique for the organization of pre-synthesized nanoparticles on hard substrates, using block copolymer films as sacrificial templates. A thin block copolymer film is dip-coated on the substrate of interest and the sample is exposed to a solution containing nanoparticles. Spontaneous preferential adsorption of the nanoparticles on one phase of the block copolymer film results in their lateral organization. An oxygen plasma etch is used to remove the polymer film; the nanoparticles end up organized on the substrate. We demonstrate that this is a general approach for the patterning of inorganic nanoparticles on hard substrates, showing the organization of metal and semiconductor nanoparticles having different chemistries at the particle/solvent and solvent/polymer interfaces. The nanoparticle patterns that we present have typical periodicities in the nanometer scale. In some cases, microcontact printing is used to create a double length scale of organization, on the micrometer and on the nanometer level. The characteristic periodicity of the template is studied with respect to the nanoparticle size in order to optimize the organization. Finally, we describe how to extend this technique for the production of continuous gold nanowires on hard substrates. We expect that the flexibility of this approach and the degree of control that can be obtained over nanoparticle organization should make it a powerful tool for nanoscale fabrication.     

Lower Bounds for Dynamic Algebraic Problems

We consider dynamic evaluation of algebraic functions (matrix multiplication, determinant, convolution, Fourier transform, etc.) in the model of Reif and Tate; i.e., if f(x₁,…, x_n)=(y₁, …, y_m) is an algebraic problem, we consider serving online requests of the form “change input x_i to value v” or “what is the value of output y_i?” We present techniques for showing lower bounds on the worst case time complexity per operation for such problems. The first gives lower bounds in a wide range of rather powerful models (for instance, history dependent algebraic computation trees over any infinite subset of a field, the integer RAM, and the generalized real RAM model of Ben-Amram and Galil). Using this technique, we show optimal Ω(n) bounds for dynamic matrix–vector product, dynamic matrix multiplication, and dynamic discriminant and an Ω( ) lower bound for dynamic polynomial multiplication (convolution), providing a good match with Reif and Tate's O( ) upper bound. We also show linear lower bounds for dynamic determinant, matrix adjoint, and matrix inverse and an Ω( ) lower bound for the elementary symmetric functions. The second technique is the communication complexity technique of Miltersen, Nisan, Safra, and Wigderson which we apply to the setting of dynamic algebraic problems, obtaining similar lower bounds in the word RAM model. The third technique gives lower bounds in the weaker straight line program model. Using this technique, we show an Ω((log n)²/log log n) lower bound for dynamic discrete Fourier transform. Technical ingredients of our techniques are the incompressibility technique of Ben-Amram and Galil and the lower bound for depth-two superconcentrators of Radhakrishnan and Ta-Shma. The incompressibility technique is extended to arithmetic computation in arbitrary fields.     

Mathematical programming algorithms for regression-based nonlinearfiltering in RN

This paper is concerned with regression under a “sum” of partial order constraints. Examples include locally monotonic, piecewise monotonic, runlength constrained, and unimodal and oligomodal regression. These are of interest not only in nonlinear filtering but also in density estimation and chromatographic analysis. It is shown that under a least absolute error criterion, these problems can be transformed into appropriate finite problems, which can then be efficiently solved via dynamic programming techniques. Although the result does not carry over to least squares regression, hybrid programming algorithms can be developed to solve least squares counterparts of certain problems in the class     

Fusarium DNA traceability along the bread production chain

Wheat grain contamination with toxigenic Fusarium spp. is of great economic concern to cereal producers and to the grain processing industry and is of great relevance for the quality and safety of the final products. In particular, the bread production chain can potentially be a vehicle for mycotoxin ingestion above the tolerable total daily intake. A quantitative polymerase chain reaction‐based analytical approach has been developed as a possible tool to estimate and control the risk of mycotoxins, particularly deoxynivalenol (DON). This DNA‐based analytical method has been applied to detect and quantify contamination levels of Fusarium graminearum and Fusarium culmorum in naturally infected wheat grain samples. The persistence of Fusarium contamination was also detected along the bread production chain in wholemeal, flour and bread. A significant correlation was found between Fusarium DNA and DON concentration in all samples.     

Diagnostic Performance of 1→3-β-d-Glucan in Neonatal and Pediatric Patients with Candidemia

Fungal sepsis is one of the major problems in neonatal and pediatric care unit settings. The availability of new diagnostic techniques could allow medical practitioners to rapidly identify septic patients and to improve their outcome. The aim of this study was to evaluate the performance of the 1→3-β-d-glucan (BDG), individually and in comparison with the Candida mannan (CM) antigen, in ten preterm infants and five onco-haematological pediatric patients with Candida bloodstream infections already proven by positive culture. The serum levels of BDG were >80 pg/mL on the same day as a positive blood culture in all examined patients, while CM antigen was negative in the patients with C. parapsilosis fungemia and in one further case due to C. albicans. These results suggest that a regular monitoring of serum circulating antigens (i.e., 1→3-β-d-glucan) combined with other microbiological and clinical information, may allow earlier and accurate diagnosis. However, further studies are necessary to confirm its usefulness in routine clinical practice.     

High-Temperature Oxidation and Oxide Scale Formation in Plasma-Sprayed CoNiCrAlYRe Coatings

MCrAlY coatings are usually adopted to improve the environmental resistance of Ni-based superalloy components of turbine engines against high-temperature oxidation and hot corrosion. In this work, CoNiCrAlYRe coatings were produced by atmospheric plasma spraying. The coatings exhibited relatively low oxygen content and porosity. X-ray diffraction, scanning electron microscopy, and energy dispersive spectroscopy analyses revealed that the high-temperature exposure at 1383 K (1110 °C) promoted the growth of an oxide scale on the top surface being composed of a continuous and dense Al₂O₃ inner layer followed by an outer mixed layer (Cr₂O₃ and spinels). The oxide scale was mainly composed of Al₂O₃, while the formation of mixed oxides occurred at lesser extent. After high-temperature exposure, the formation of internal oxides in some areas reduced the inter-lamellar cohesion, so that a decrease in microhardness was found.     

Application of real-time PCR (qPCR) for characterization of microbial populations and type of milk in dairy food products

Dairy foods represent an important sector of the food market for their nutritional qualities and their organoleptic characteristics, which are often linked to tradition and to region. These products are typically protected by labels such as PDO (Protected Designation of Origin) and PGI (Protected Geographical Indication). Real-time PCR (qPCR) is a fundamental tool in “Food Genomics;” a discipline concerned with the residual DNA in food, which, alongside traditional physical and chemical methods, is frequently used to determine product safety, quality and authenticity. Compared to conventional or “end-point” PCR, qPCR incorporates continuous monitoring of reaction progress, thereby enabling quantification of target DNA. This review describes qPCR applications to the analysis of microbiota, and to the identification of the animal species source of milk from which dairy products have been made. These are important aspects for ensuring safety and authenticity. The various applications of qPCR are discussed, as well as advantages and disadvantages in comparison with other analytical methods.