Tapering photonic crystal fibres for supercontinuum generation with nanosecond pulses at 532 nm

Experimental results on supercontinuum generation in photonic crystal fibre tapers using pump pulses of 7 ns duration at 532 nm are presented. Photonic crystal fibre tapers with the first wavelength of zero dispersion around 532 nm were fabricated. The generation of supercontinuum was investigated in normal and anomalous dispersion regimes. Supercontinuum spectra spanning more than 400 nm in the visible region are reported.     

Characterization of the Effects of Aryl-azido Compounds and UVA Irradiation on the Viral Proteins and Infectivity of Human Immunodeficiency Virus Type 1

Hydrophobic UV-activatable compounds have been shown to partition into the hydrophobic region of biological membranes to selectively label transmembrane proteins, and to inactivate enveloped viruses. Here, we analyze various UV-activatable azido- and iodo-based hydrophobic compounds for their ability to inactivate a model-enveloped virus, human immunodeficiency virus (HIV-1 MN). Treatment of HIV-1 with 1,5-diazidonapthalene (DAN), 1-iodo, 5-azidonaphthalene (INA), 1-azidonaphthalene (AzNAP) or 4,4′-diazidobiphenyl (DABIPH) followed by UVA irradiation for 2 min resulted in complete viral inactivation, whereas treatment using analogous non–azido-containing controls had no effect. Incorporation of an azido moiety within these hydrophobic compounds to promote photoinduced covalent reactions with proteins was found to be the primary mechanism of viral inactivation for this class of compounds. Prolonged UVA irradiation of the virus in the presence of these azido compounds resulted in further modifications of viral proteins, due to the generation of reactive oxygen species, leading to aggregation as visualized via Western blot analysis, providing additional viral modifications that may inhibit viral infectivity. Furthermore, inactivation using these compounds resulted in the preservation of surface antigenic structures (recognized by neutralizing antibodies b12, 2g12 and 4e10), which is favorable for the creation of vaccines from these inactivated virus preparations.     

Control production of polyester resins by NIR spectroscopy

The control of the esterification reaction for production of polyester saturated resins is followed usually by determination of the acid value (AV) and hydroxyl value (OHV).These parameters are determined by titrimetry, but these methods are slow, intensity working and produce waste. In this paper an alternative methodology is proposed, based in the construction of multivariate models on NIR spectroscopic data and different models are constructed in order to apply to different steps of the production process. The ensuing methodology provides models of good predictive ability and constitute an advantageous alternative to existing titrimetric reference methods as regards expeditiousness and environmentally compatible. The multivariate calibration models established were also used with a different instrument; to this end, the spectra recorded with the original equipment were subjected to Piecewise Direct Standardization (PDS) in order to make them equivalent to those provided by the new equipment. Also, PLS calibration was reproduced by using the same samples, spectral treatment, wavenumber range and number of factors as in the original model, and the AV and OHV results thus obtained were similarly good.     

Dynamics of supply chain networks with corporate social responsibility through integrated environmental decision-making

In this paper, we develop a dynamic framework for the modeling and analysis of supply chain networks with corporate social responsibility through integrated environmental decision-making. Through a multilevel supply chain network, we model the multicriteria decision-making behavior of the various decision-makers (manufacturers, retailers, and consumers), which includes the maximization of profit, the minimization of emission (waste), and the minimization of risk. We explore the dynamic evolution of the product flows, the associated product prices, as well as the levels of social responsibility activities on the network until an equilibrium pattern is achieved. We provide some qualitative properties of the dynamic trajectories, under suitable assumptions, and propose a discrete-time algorithm which is then applied to track the evolution of the levels of social responsibility activities, product flows and prices over time. We illustrate the model and computational procedure with several numerical examples.     

Reducing Variability in Pollution Data: The Use of Lipid Classes for Normalization of Pollution Data in Marine Biota

Abstract

Organochlorine residues (PCBs and pesticides) are usually normalized on lipid content, gravimetrically quantified after extraction in organic solvents. In this study, the lipid content of different biotic groups (e.g. phytoplankton, shrimp, bivalves, fish), obtained through different types of extraction (total extraction versus specific extraction of apolar lipids) and quantification techniques (total gravimetric determinations versus specific determinations of lipid classes (latroscan)) were compared. The different lipid quantification methods were interrelated. An overestimation of lipid content due to non-lipid co-extracts was shown to interfere with gravimetric lipid quantifications. The relative contribution of these co-extracts depended on the type of sample studied. Differences in pollution levels (individual PCB congeners) between different biotic groups (phytoplankton, shrimp, cockles, fish) and between different fish tissues are discussed in relation to lipid content, determined by the different methods. An important reduction in the variability of pollution levels was noted when data were normalized on total neutral lipid content (latroscan). Highly significant linear regression parameters were obtained between the pollutant and the total neutral lipid content of marine biotic samples from the same water mass. Water mass specific bio-lipid contamination levels, characteristic for the whole biotic community (excluding seabirds and sea mammals), were determined for the different PCB congeners, normalized on total neutral lipid content. These bio-lipid contamination levels were related to the K_ow of the congeners. This functional relationship could be described by a second order polynomial regression.     

Re-absorption process in the upconversion green emission of the erbium ion-doped fluorozirconate glass system

In this paper we report the upconversion emission for the ⁴S_3/2→⁴I_15/2 Stark components of Er³⁺ ion-doped fluorozirconate glass at T=2 K. The spectrum shows only seven peaks, one less than expected theoretically, being missing the peak at the wave number 17,996 cm⁻¹ (λ=555 nm). This result is compared with the luminescence for the same transition at the same conditions which exhibits the eight expected lines. Such a discrepancy is attributed to a re-absorption process (ESRA) between the energy levels ⁴I_13/2 and ²H_9/2.     

9‐Benzoyl‐3,3,6,6‐tetramethyl‐1,2,3,4,5,6,7,8‐octahydroxanthene‐1,8‐dione: molecular conformation and supramolecular aggregation in xanthenediones

In the title compound, C₂₄H₂₆O₄, (I), the central ring of the fused tricyclic ring system adopts a shallow boat conformation, while the two outer rings adopt envelope conformations. The molecules are linked into C(9) chains by a single C—H...O hydrogen bond. The significance of this study lies in its comparison of the conformation and supramolecular aggregation of (I) with those of related compounds in the published literature.     

Synthesis and characterization of acrylamide/acrylic acid hydrogels crosslinked using a novel diacrylate of glycerol to produce multistructured materials

In this work we propose a new crosslinking agent and the method to use it for the synthesis of acrylate based hydrogels. The use of this diacrylate of glycerol, synthesized in our laboratory, allows the generation of materials with well defined micro‐structures in the dry state, unique meso‐ and macro‐structures during swelling, and enhanced mechanical properties and swelling capacity in water. These properties depend on the crosslinking agent concentration, as well as synthesis thermal history. Poly(acrylamide‐co‐acrylic acid) hydrogels are commonly crosslinked with N, N′‐methylenebisacrylamide or N‐isopropylacrylamide. Here we obtain and use a new crosslinking agent, obtained from the reaction between glycerol and acrylic acid to produce a Diacrylate of glycerol (DAG). Two synthesis methods at equivalent molar ratio of acrylamide/acrylic acid (AM/AA) were analyzed. The mechanical properties, the swelling capacity, and the morphology at microscale of these hydrogels showed a well defined transition at a critical concentration of crosslinking agent. DAG induces the generation of hydrogels with hierarchichal structure. The micro‐structure surface morphology was investigated by scanning electron microscopy, the meso‐structure by polarized light microscopy and the macro‐structure by CCD imaging. The hydrogels with hierarchical structures showed improved mechanical properties when compared with structureless hydrogels. Control of the microstructure allows the generation of materials for different applications, i.e. templates or smart materials that interact with electromagnetic radiation. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2667–2679, 2008     

Optimization of headspace experimental factors to determine chlorophenols in water by means of headspace solid-phase microextraction and gas chromatography coupled with mass spectrometry and parallel factor analysis

In this work an analytical procedure based on headspace solid-phase microextraction and gas chromatography coupled with mass spectrometry (HS-SPME–GC/MS) is proposed to determine chlorophenols with prior derivatization step to improve analyte volatility and therefore the decision limit (CCα). After optimization, the analytical procedure was applied to analyze river water samples. The following analytes are studied: 2,4-dichlorophenol (2,4-DCP), 2,4,6-trichlorophenol (2,4,6-TrCP), 2,3,4,6-tetrachlorophenol (2,4,6-TeCP) and pentachlorophenol (PCP). A D-optimal design is used to study the parameters affecting the HS-SPME process and the derivatization step. Four experimental factors at two levels and one factor at three levels were considered: (i) equilibrium/extraction temperature, (ii) extraction time, (iii) sample volume, (iv) agitation time and (v) equilibrium time. In addition two interactions between four of them were considered. The D-optimal design enables the reduction of the number of experiments from 48 to 18 while maintaining enough precision in the estimation of the effects. As every analysis took 1 h, the design is blocked in 2 days.