A simple colorimetric determination of the free amino groups in water soluble chitin derivatives using genipin

A colorimetric method for quantitative measurement of free amino groups of water soluble chitin derivatives is described. The method utilizes genipin as a natural and specific reagent for determining the concentration of free amino groups in samples of water soluble chitin derivatives. The blue color adduct (complex) formed during genipin reaction with free amino groups was measured at about 589 nm and Beer-Lambert’s law obeyed over the concentration range of 50 to 300 mg/L. Parameters of analytical conditions were considered and kept constant during the experimental procedure. Highly acetylated water soluble chitin derivatives can be differentiated from water soluble chitosan using this genipin method. The colorimetric method with genipin was proved to be a rapid and efficient technique to determine the free amino groups in water soluble chitin derivatives. This method can also be applied for the detection of the enzymatic activity of chitindeacetylase.     

Solution and quasi‐bulk copolymerizations of styrene and methyl methacrylate in the presence of polybutadiene: Mathematical model

A mathematical model was developed for simulating the batch copolymerization of styrene (St) and methyl methacrylate (MMA) in the presence of polybutadiene (PB). It was adjusted to the measurements of three reactions carried out at 65°C, with initial comonomers ratio at the azeotropic condition, THF as solvent, and benzoyl peroxide as initiator. The measurements included: (a) conversions and grafting efficiencies by gravimetry; (b) molecular weight distributions (MWDs) by size exclusion chromatography; and (c) global mass fractions of St in the co‐ and terpolymer, by UV‐Vis spectroscopy. The model predicts the MWDs of the three polymeric components of MBS: free St‐MMA copolymer, St‐MMA‐g‐PB graft terpolymer (GT), and residual PB. In addition, it predicts the bivariate chain length distributions of the different GT topologies, with each topology characterized by the number of branches per molecule. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Analysis of the behaviour of the structural concrete after the fire at the Windsor Building in Madrid

The analysis of the concrete subjected to high temperatures is usually undertaken by means of tests specifically designed and carried out in the laboratory, or by using theoretical approaches using standardized curves for theoretical fires. An analysis by different techniques has been carried out on structural concrete to real fire of Windsor Building in Madrid, which was severally damaged by a fire in 2005. These techniques are X‐ray diffraction, differential thermal and thermogravimetric analysis and backscattered electron microscopy with dispersive X‐ray microanalysis. Samples of the concrete were taken from different floors in the building and analyses were carried out at different depths starting from the surface exposed to the fire itself. The analysis allows the damaged area to be limited as well as situating the 500^°C isotherm in the concrete element. In accordance with the results obtained, the damage is limited to just a few centimeters from the surface exposed to the fire itself, in spite of its prolonged exposure to the fire. This would justify that the concrete has demonstrated a suitable resistant behaviour. Likewise, it can be deduced from the results obtained that the fire, to which the concrete was subjected, can be qualified as severe. Also, these results can confirm that the calculation hypothesis in the project is correct in relation to the fire resistance exigencies of the concrete. Copyright © 2009 John Wiley & Sons, Ltd.     

Development and neuronal dependence of cutaneous sensory nerve formations: Lessons from neurotrophins

Null mutations of genes from the NGF family of NTs and their receptors (NTRs) lead to loss/reduction of specific neurons in sensory ganglia; conversely, cutaneous overexpression of NTs results in skin hyperinnervation and increase or no changes in the number of sensory neurons innervating the skin. These neuronal changes are paralleled with loss of specific types of sensory nerve formations in the skin. Therefore, mice carrying mutations in NT or NTR genes represent an ideal model to identify the neuronal dependence of each type of cutaneous sensory nerve ending from a concrete subtype of sensory neuron, since the development, maintenance, and structural integrity of sensory nerve formations depend upon sensory neurons. Results obtained from these mouse strains suggest that TrkA positive neurons are connected to intraepithelial nerve fibers and other sensory nerve formations depending from C and Aδ nerve fibers; the neurons expressing TrkB and responding to BDNF and NT‐4 innervate Meissner corpuscles, a subpopulation of Merkell cells, some mechanoreceptors of the piloneural complex, and the Ruffini's corpuscles; finally, a subpopulation of neurons, which are responsive to NT‐3, support postnatal survival of some intraepithelial nerve fibers and Merkel cells in addition to the muscle mechanoreceptors. On the other hand, changes in NTs and NTRs affect the structure of non‐nervous structures of the skin and are at the basis of several cutaneous pathologies. This review is an update about the role of NTs and NTRs in the maintenance of normal cutaneous innervation and maintenance of skin integrity. Microsc. Res. Tech. 2010. © 2009 Wiley‐Liss, Inc.     

Effect of methanol content on enzymatic production of biodiesel from waste frying oil

The enzymatic production of biodiesel from waste frying oil with methanol has been studied using immobilized lipase Novozym 435 as catalyst. The effects of methanol to oil molar ratio, dosage of enzyme and reaction time were investigated. The optimum reaction conditions were methanol to oil molar ratio of 25:1, 10% of Novozym 435 based on oil weight and reaction period of 4 h at 50 °C obtaining a biodiesel yield of 89.1%. Moreover, the reusability of the lipase over repeated cycles was also investigated under standard conditions.     

The role of the interface in melt linear viscoelastic properties of LLDPE/LDPE blends: Effect of the molecular architecture of the matrix

The rheological properties of blends consisting of a long chain branched low‐density polyethylene (LDPE) and two linear low‐density polyethylenes (LLDPE) are studied in detail. The weight fractions of the LDPE used in the blends are 5 and 15%. The linear viscoelastic characterization is performed at different temperatures for all the blends to check thermorheological behavior and miscibility in the melt state. Blends containing metallocene LLDPE as the matrix display thermorheologically complex behavior and show evidences of immiscibility in the melt state. The linear viscoelastic response exhibits the typical additional relaxation ascribed to the form deformation mechanism of dispersed phase droplets (LDPE). The Palierne model satisfactorily describes the behavior of these blends in the whole frequency range explored. However, those blends with Ziegler‐Natta LLDPE as the matrix fulfill the time‐temperature superposition, but exhibit a broad linear viscoelastic response, further than the expected for an immiscible system with a sharp interface. The rheological analysis reveals that, in addition to the droplets form relaxation, another mechanism at lower frequencies exists. The broad linear response of the blends with the Ziegler‐Natta LLDPE can be explained by hypothesizing a strong interaction between the high molecular weight linear fraction of the LLDPE and the low molecular weight (almost linear) chains of the LDPE phase, forming a thick interface with its own viscoelastic properties. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

ZnO nanowire co-growth on SiO2 and C by carbothermal reduction and vapour advection

Vertically aligned ZnO nanowires (NWs) were grown on Au-nanocluster-seeded amorphous SiO(2) films by the advective transport and deposition of Zn vapours obtained from the carbothermal reaction of graphite and ZnO powders. Both the NW volume and visible-to-UV photoluminescence ratio were found to be strong functions of, and hence could be tailored by, the (ZnO+C) source-SiO(2) substrate distance. We observe C flakes on the ZnO NWs/SiO(2) substrates which exhibit short NWs that developed on both sides. The SiO(2) and C substrates/NW interfaces were studied in detail to determine growth mechanisms. NWs on Au-seeded SiO(2) were promoted by a rough ZnO seed layer whose formation was catalysed by the Au clusters. In contrast, NWs grew without any seed on C. A correlation comprising three orders of magnitude between the visible-to-UV photoluminescence intensity ratio and the NW volume is found, which results from a characteristic Zn partial pressure profile that fixes both O deficiency defect concentration and growth rate.     

Fluorescence Liquid Biopsy for Cancer Detection Is Improved by Using Cationic Dendronized Hyperbranched Polymer

(1) Background: Biophysical techniques applied to serum samples characterization could promote the development of new diagnostic tools. Fluorescence spectroscopy has been previously applied to biological samples from cancer patients and differences from healthy individuals were observed. Dendronized hyperbranched polymers (DHP) based on bis(hydroxymethyl)propionic acid (bis-MPA) were developed in our group and their potential biomedical applications explored. (2) Methods: A total of 94 serum samples from diagnosed cancer patients and healthy individuals were studied (20 pancreatic ductal adenocarcinoma, 25 blood donor, 24 ovarian cancer, and 25 benign ovarian cyst samples). (3) Results: Fluorescence spectra of serum samples (fluorescence liquid biopsy, FLB) in the presence and the absence of DHP-bMPA were recorded and two parameters from the signal curves obtained. A secondary parameter, the fluorescence spectrum score (FS_score), was calculated, and the diagnostic model assessed. For pancreatic ductal adenocarcinoma (PDAC) and ovarian cancer, the classification performance was improved when including DHP-bMPA, achieving high values of statistical sensitivity and specificity (over 85% for both pathologies). (4) Conclusions: We have applied FLB as a quick, simple, and minimally invasive promising technique in cancer diagnosis. The classification performance of the diagnostic method was further improved by using DHP-bMPA, which interacted differentially with serum samples from healthy and diseased subjects. These preliminary results set the basis for a larger study and move FLB closer to its clinical application, providing useful information for the oncologist during patient diagnosis.