All-optical 2R-regeneration and continuous wave to pulsed signal wavelength conversion based on fiber nonlinearity

In this paper, we propose a novel all-optical 2R (re-amplification and re-shaping) regenerator based on inducing nonlinear chirp over a continuous wave probe. The regenerator also performs continuous wave to pulsed wavelength conversion. The chirp is induced in a highly nonlinear fiber by the data modulated pulsed signal that is to be regenerated. Offset filtering is employed at the output of the highly nonlinear fiber to extract the frequencies generated as a result of chirping. The regenerator performance has been evaluated with the help of bit-error-rate plots and eye diagrams at different values of optical signal to noise ratios. Apart from re-shaping and re-amplification, inclusion of the regenerator results in better resilience to amplified spontaneous emission noise.     

Study of the kinetics and activation parameters of reduction of Mn(III) to Mn(II) by SO3 2− ion in (MnSiW11O40H2)5- heteropoly ion

In order to gain an insight into the mechanism of reduction of Mn(III) heteropoly ions, and also to establish the conditions for use of some of these ions as oxidizing agent, following measurements have been made. The pseudo-first order rate constants, k_obs, have been determined and specific rate constants, k, were calculated from the plots of k_obs against SO₃ ^2? concentrations. A plot of ln(k₂/T) against inverse temperature gives enthalpy of activation as 10.67 kJ mol^?1 and entropy of activation as ?237.90 J K^?1 mol^?1. Effects of ionic strength and pH have also been studied over a limited range.     

Physicochemical investigation of sulfonamide-derived compounds interacting with conventional cationic surfactants in aqueous media

The sulfonamide core in compounds is effective synthons, which offer exciting perspectives in chemotherapeutic and pharmacological research. In this study, we investigated the molecular interaction of potent sulfonamide derivatives (SDs), 2-benzenesulfonamido-3-methylbutyric acid (BSB) and tetraaquabis{3-methyl-2-[(phenylsulfonyl)amino]butanoate}copper(II) (Cu-BSB), with cationic surfactants, cetyltrimethyl ammonium bromide (CTAB) and ethylhexadecyl dimethyl ammonium bromide (EHDAB), using UV-visible spectroscopy and steady-state fluorescence measurements. Various mathematical models were applied to quantify the effect of cationic surfactants on physicochemical characteristics of BSB and Cu-BSB. These interactions were confirmed by estimating the partition coefficient (K_x), binding capacities (K_b), Stern-Volmer quenching constant (K_sv), and related Gibbs free energies (ΔG_b). The in-depth mechanism revealed that the binding mode in SD–surfactants combinational system is spontaneous and quenching exists in static mode initiated by ground-state complex formation. We believe that the true knowledge of host–guest interaction mechanisms concerning model membrane with entrapped moiety can help in better understanding of molecular recognition in related phospholipid membrane models.     

Effect of substitution of K ions on the structural and electrical properties of nanocrystalline MgAl2O4 spinel oxide

Potassium substituted nanosized magnesium aluminates having a nominal composition Mg_1−xK_xAl₂O₄ where x=0.0, 0.25, 0.5, 0.75, 1.0 have been synthesized by the chemical co-precipitation method. The samples have been characterized by means of X-ray diffraction (XRD), scanning electron microscope (SEM), and dc electrical resistivity measurements. The XRD results reveal that the samples are spinel single phase cubic close packed crystalline materials. The calculated crystallite size ranges between 6 and 8 nm. The behaviour of the lattice constant seems to deviate from the Vegard's law. While X-ray density clearly increases, the bulk density and consequently, the percentage porosity do not exhibit a significant change on increasing the K⁺ content. The SEM micrographs suggest homogeneous distribution of the nanocrystallites in the samples. The dc electrical resistivity exhibits a typical semiconducting behaviour. Substitution of a Mg²⁺ ion by a K⁺ ion provides an extra hole to the system, which forms small polaron. Thermally activated hopping of these small polarons is believed to be the conduction mechanism in the Mg_1−xK_xAl₂O₄. The activation energy of hopping of small polarons has been calculated and found K⁺ ions content dependent.     

Enrichment of HDL proteome and phospholipidome from human serum via IMAC/MOAC affinity

High-density lipoproteins (HDLs) have anti-inflammatory and antioxidant properties and are potentially cardio-protective. Defective HDL function is caused by alterations in both the proteome and lipidome of HDL particles. As potential biomarkers, the development of analytical methods is necessary for the enrichment of HDLs. Therefore, a method for selective enrichment of HDLs using immobilized metal ion affinity chromatography (IMAC) and metal oxide affinity chromatography (MOAC) is presented. SPE-based isolation of HDLs from whole serum is adopted as an alternative to traditional ultracentrifugation methods followed by SDS–PAGE. The enrichment mechanism relies on isoelectric points of lipoproteins and metal oxide. Negatively charged lipoprotein particles interact with positively charged metal oxides and IMAC affinity, which acts as a cation. Identified proteins from HDL through MALDI–MS analysis are apo AI, AII, AIV, CI, CIII, E, J, M, H, serum amyloid A and other nonapoproteins that are part of HDL particles and perform cellular functions. This serum-based proteomics approach gives insight into the functional role of HDL. HDL-associated phospholipids have also been analyzed by LDI–MS. Results suggest that the adopted analytical strategy is a feasible idea to extract lipoproteins from serum. A comparative study of healthy and diseased samples using this approach will provide valuable information in future.     

Dimeric supramolecular motifs of two carboxylate–guanidinium compounds

The structures of N‐benzyl‐N′‐{6‐[(4‐carboxylatobenzyl)aminocarbonyl]‐2‐pyridylmethyl}guanidinium, C₂₃H₂₃N₅O₃, (I), and N‐[2‐(benzylaminocarbonyl)ethyl]‐N′‐{6‐[(4‐carboxylatobenzyl)aminocarbonyl]‐2‐pyridylmethyl}guanidinium monohydrate, C₂₆H₂₈N₆O₄·H₂O, (II), both form three‐dimensional supramolecular hydrogen‐bonded networks based on a dimeric primary synthon involving carboxylate–guanidinium linkages. The differences in the geometries and hydrogen‐bonding connectivities are driven by the additional methylpropionamide group and water of crystallization of (II).     

Functionalized diamond nanopowder for phosphopeptides enrichment from complex biological fluids

Diamond is known for its high affinity and biocompatibility towards biomolecules and is used exclusively in separation sciences and life science research. In present study, diamond nanopowder is derivatized as Immobilized Metal Ion Affinity Chromatographic (IMAC) material for the phosphopeptides enrichment and as Reversed Phase (C-18) media for the desalting of complex mixtures and human serum profiling through MALDI-TOF-MS. Functionalized diamond nanopowder is characterized by Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) spectroscopy. Diamond-IMAC is applied to the standard protein (β-casein), spiked human serum, egg yolk and non-fat milk for the phosphopeptides enrichment. Results show the selectivity of synthesized IMAC-diamond immobilized with Fe³⁺ and La³⁺ ions. To comprehend the elaborated use, diamond-IMAC is also applied to the serum samples from gall bladder carcinoma for the potential biomarkers. Database search is carried out by the Mascot program (www.matrixscience.com) for the assignment of phosphorylation sites. Diamond nanopowder is thus a separation media with multifunctional use and can be applied to cancer protein profiling for the diagnosis and biomarker identification.