Quantum Dots Emitting in the Third Biological Window as Bimodal Contrast Agents for Cardiovascular Imaging

Physicians are demanding innovative technologies for multimodal imaging of the cardiovascular system that would lead to the appearance of advanced diagnosis and therapy procedures. This implies the simultaneous development of new imaging techniques and contrast agents whose synergy would make it possible. Optical coherence tomography (OCT) has recently emerged as a versatile and high‐resolution clinical technique for cardiovascular imaging. Unfortunately, the lack of adequate contrast agents impedes the use of OCT for intracoronary multimodal imaging. In this work, the hitherto unexplored capability of semiconductor quantum dots (IR‐QDs) emitting in the third infrared biological window (1.55–1.87 µm) to act as multimodal agents for intracoronary imaging is demonstrated. Under single line laser excitation at 1.3 µm, IR‐QDs are capable of providing simultaneous backscattering contrast and efficient luminescence at 1.6 µm. In this work, backscattered radiation is successfully employed to construct OCT images in both fluids and tissues whereas the infrared luminescence of the IR‐QDs provides the possibility for simultaneous acquisition of high penetrating fluorescence images. The first multimodal (fluorescence + OCT) imaging of an artery using IR‐QDs as contrast agents is provided herein demonstrating their outstanding potential for future clinical applications.     

An algorithm for robust linear estimation with grouped data

An algorithm which is valid to estimate the parameters of linear models under several robust conditions is presented. With respect to the robust conditions, firstly, the dependent variables may be either non-grouped or grouped. Secondly, the distribution of the errors may vary within the wide class of the strongly unimodal distributions, either symmetrical or non-symmetrical. Finally, the variance of the errors is unknown. Under these circumstances the algorithm is not only capable of estimating the parameters (slopes and error variance) of the linear model, but also the asymptotic covariance matrix of the linear parameters. This opens the possibility of making inferences in terms of either multiple confidence regions or hypothesis testing.     

Fractional models,non-locality,and complex systems

In this paper, a new approach to the deterministic modelling of dynamics of certain processes in an anomalous environment is proposed. To this end, the standard assumptions that are usually justified by the experiments and led to the classical dynamics models are rewritten in the way that takes into consideration the non-local features of the anomalous environment. The new class of models obtained in this way is characterized by the memory functions that have to be properly determined for a concrete process. In particular, the so-called fractional dynamics models described in terms of the fractional differential equations are among particular cases of the general model. When a concrete process is observed and its characteristics are measured within a certain time interval, the memory functions that characterize the non-locality of the medium can be found by solving an inverse problem for a system of the Volterra integral equations. Special attention is given to the population dynamics examples to highlight the advantages of the new way to focus the model of the dynamics of complex processes compared with the classical ones.     

Prediction of immunoglobulin G content in bovine colostrum by near-infrared spectroscopy

The objective of this work was to assess the potential of near infrared spectroscopy to predict the immunoglobulin G (IgG) content in bovine colostrum. Liquid colostrum samples (n=157) were collected from Holstein cows from 2 dairy farms in southern Chile. Samples were obtained within 1h of parturition and scanned in folded transmission (transflectance) in the visible-near infrared range. Multivariate regression models (modified partial least squares) were developed with spectral data against IgG content measured by radial immunodiffusion. The best calibration included a mathematical treatment of the spectra by a second derivative plus standard normal variate and detrending. The best equation explained a high proportion of the variation in IgG content (R(2) of 0.95 in calibration and 0.94 in cross-validation). Average (91.5 g/L), standard deviation (37.6g/L), and range, as highest minus lowest values (171.9 g/L) of reference values were 10.1, 4.2, and 19 times the value of the root mean square error of cross-validation (9.03 g/L) respectively. Near-infrared spectroscopy, scanned in folded transmission, is an effective tool to predict the IgG content in liquid colostrum.     

An antibacterial submicron fiber mat with in situ synthesized silver nanoparticles

This work presents an alternative approach for fabricating electrospun submicron highly hydrophilic fiber mats loaded with silver nanoparticles. These fiber mats show a high efficient antibacterial behavior, very attractive for applications like wound healing and skin regeneration processes. The fabrication method is divided in two steps. First, poly(acrylic acid) (PAA) and β‐cyclodextrin (β‐CD) submicron fibers were electrospun and further stabilized using a thermal treatment, yielding stable hydrogel‐like fibers with diameters ranging from 100 nm up to several microns. In the second step, silver ions were loaded into the fibers and then reduced to silver nanoparticles in‐situ. The electrospinning parameters were adjusted to achieve the desired properties of the fiber mat (density, size) and afterwards, the characteristics of the silver nanoparticles (amount, size, aggregation) were tuned by controlling the silver ion loading mechanism. Highly biocide surfaces were achieved showing more than 99.99% of killing efficiency. The two‐step process improves the reproducibility and tunability of the fiber mats. To our knowledge, this is the first time that stable hydrogel fibers with a highly biocide behavior have been fabricated using electrospinning. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Furan resin as a replacement of phenolics: influence of the clay addition on its thermal degradation and fire behaviour

Nanocomposites based on a furan resin and different types of clays were obtained. Their thermal and fire behaviours were compared with traditional phenolic resins, which are known by their excellent flame resistance. Three types of montmorillonite clays were in situ added to the thermosetting matrix. A cone calorimeter and a smoke chamber were used to evaluate the performance of the materials against fire and their smokes generation. Global parameters were calculated for comparison purposes. Fires derived from the furan resin combustion grow faster than the phenolic ones, but they are extinguished more rapidly. This effect is enhanced by the incorporation of inorganic nanofillers. The only addition of any clay causes shorter fires but slightly speeds up the degradation process. A homogeneous nanofiller dispersion was found to be crucial to achieve good fire behaviour. Nevertheless, for materials with similar dispersion, the crosslinking degree of the polymer matrix appears as a secondary factor that determines slighter differences in the performance. Nanocomposites with organomodified clays showed a quite similar fire performance, though the composite containing the clay (Southern Clay Products, Inc., Louisville, Ky, USA) Cloisite®30B showed the best performance taking into account both the fire risk and the smoke evolution and obscuration. Copyright © 2013 John Wiley & Sons, Ltd.     

Synthesis and characterization of nanocomposites based on a furan resin

Formaldehyde emissions are nowadays trying to be reduced because of its atmospheric pollutant character. Besides, it is encouraged the use of polymeric materials synthesized from biomass wastes as row materials. For this reason, furan resins would be an alternative to phenolic resins, where formaldehyde is replaced by furfural as a reactant. Regarding, the addition of nanoparticles to the furan resin should enhance their performance as metal coatings with good thermal and oxidative resistance. The aim of this article is to study the influence of the in situ addition of different type of nanoparticles on the chemical reactions involved in the synthesis of a furan resin. From the viscosity measurements it was observed that the addition of the nanoreinforcements led to a higher resin reaction rate. Differences in the final chemical structure among the materials were also observed by infrared spectroscopy analyses. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Synthesis of basic aluminum sulfate assisted by microwave heating

The synthesis of basic aluminum sulfate (BAS) was promoted by the microwave heating of a mixture of aluminum sulfate, aluminum nitrate, and sodium hydroxide. The heating process was facilitated by microwaves set at different temperatures and reaction time durations. The obtained products were characterized by X-ray diffraction and scanning electronic microscopy. Crystallographic and morphological analysis revealed BAS, boehmite, or a mixture of both products, depending on the reaction conditions.