Transport of surface-modified iron nanoparticle in porous media and application to arsenic(III) remediation

The surface-modified iron nanoparticles (S-INP) were synthesized, characterized and tested for the remediation of arsenite (As(III)), a well known toxic groundwater contaminant of concern. The S-INP material was fully dispersed in the aqueous phase with a particle size distribution of 2–10 nm estimated from high-resolution transmission electron microscopy (HR-TEM). X-ray photoelectron spectroscopy (XPS) revealed that an Fe(III) oxide surface film was present on S-INP in addition to the bulk zero-valent Fe⁰ oxidation state. Transport of S-INP through porous media packed in 10 cm length column showed particle breakthroughs of 22.1, 47.4 and 60 pore volumes in glass beads, unbaked sand, and baked sand, respectively. Un-modified INP was immobile and aggregated on porous media surfaces in the column inlet area. Results using S-INP pretreated 10 cm sand-packed columns containing ∼2 g of S-INP showed that 100 % of As(III) was removed from influent solutions (flow rate 1.8 mL min⁻¹) containing 0.2, 0.5 and 1.0 mg L⁻¹ As(III) for 9, 7 and 4 days providing 23.3, 20.7 and 10.4 L of arsenic free water, respectively. In addition, it was found that 100% of As(III) in 0.5 mg/L solution (flow rate 1.8 mL min⁻¹) was removed by S-INP pretreated 50 cm sand packed column containing 12 g of S-INP for more than 2.5 months providing 194.4 L of arsenic free water. Field emission scanning electron microscopy (FE-SEM) showed S-INP had transformed to elongated, rod-like shaped corrosion product particles after reaction with As(III) in the presence of sand. These results suggest that S-INP has great potential to be used as a mobile, injectable reactive material for in-situ sandy groundwater aquifer treatment of As(III).     

Lysozyme coated DNA and DNA/SWNT fibers by solution spinning

DNA fibers were prepared by solution spinning of DNA in a lysozyme (LSZ) coagulation/gelation bath. Strong positive charges carried by LSZ protein condensed the DNA (strong negative charged) molecules resulting in self‐assembly and the formation of fibrillar structures in a gel‐like network. DNA/LSZ fibril formation was found to be dependent on the ratio of DNA to LSZ. A minimum 0.1 wt.‐% of LSZ was necessary to condense 0.1 wt.‐% of DNA into micro‐fibrils. Macroscopic fiber spinning was possible by introducing a 0.1 wt.‐% DNA aqueous solution into a 0.2 wt.‐% LSZ coagulation bath which resulted in fibers with ≈20 µm diameter. Single‐walled carbon nanotubes (SWNT) were also incorporated into these fibers to explore the possibility for creating hybrid materials. All DNA‐based fibers exhibit strong birefringence confirming molecular orientation along the fiber axis. Due to the presence of LSZ, the fibers exhibit antimicrobial activity against bacteria like Micrococcus lysodeikticus.

     

Spectral statistics of random Schrödinger operator with growing potential

In this work we investigate the spectral statistics of random Schrödinger operators acting on where are i.i.d random variables distributed uniformly on [0,1].     

The Fischer–Marsden conjecture and contact geometry

In this paper, we consider the Fischer–Marsden conjecture within the frame-work of K-contact manifolds and \((\kappa ,\mu )\)-contact manifolds. First, we prove that a complete K-contact metric satisfying \(\mathcal {L}^{*}_g(\lambda )=0\) is Einstein and is isometric to a unit sphere \(S^{2n+1}\). Next, we prove that if a non-Sasakian \((\kappa ,\mu )\)-contact metric satisfies \(\mathcal {L}^{*}_g(\lambda )=0\), then \( M^{3} \) is flat, and for \(n > 1\), \(M^{2n+1}\) is locally isometric to the product of a Euclidean space \(E^{n+1}\) and a sphere \(S^n(4)\) of constant curvature \(+\,4\).     

Fluorimetric assay of interaction of protein with ferrofluids

Magnetic iron oxide nanoparticles are inherently biocompatible and are amenable to post synthesis surface modification, making them excellent candidates for many important applications. If the above can be achieved in a single-step i.e., in situ synthesis and functionalization, the results are expected to be more dramatic for sensitive detection of biomolecules. For any application, it is necessary to confer a high level of binding specificity through surface chemistry, which can be introduced by using biological moieties that possess lock-and-key interactions, like those observed in antibody-antigen and enzyme-substrate recognition. In this paper, we have synthesized water based ferrofluids with serum albumin, the major protein component of blood. A series of other ferrofluids using different biocompatible polymers have also been studied with respect to their size determined by transmission electron microscopy, magnetic behavior with the aid of vibrating sample magnetometry and binding capability to bovine serum albumin by quenching of its native fluorescence. From our results, it can be inferred that binding has taken place between magnetic particles and biomolecules, the binding constants of which indirectly reveal the efficiency of the interaction.     

Effect of tackifier and crosslinkers on electron beam curable polyurethane pressure sensitive adhesive

Polyurethane based pressure sensitive adhesive using monofunctional urethane acrylate and difunctional urethane acrylate has been made using electron beam irradiation. The effect of varying electron beam doses on the adhesion properties viz., peel adhesion, shear adhesion and initial tack has been studied. Effect of tackifier and crosslinkers viz., polymeric methylene diphenyl diisocynate, carbodiimide modified methylene diphenyl diisocynate and triallyl cynurate on adhesion properties as well as on moisture vapor transmission rate and gel content of the polyurethane based pressure sensitive adhesive has also been studied. It was found that with increasing dose, tackifier and crosslinkers concentration, all the adhesion properties viz., peel adhesion, shear adhesion strength and initial tack were increased upto a certain dose, concentration of tackifier and crosslinkers, reached a plateau and then levelled off with further increasing the dose, tackifier and crosslinkers concentration. Similarly, moisture vapor transmission rate was decreased and the gel content increased with increasing dose of electron beam.     

Do topological parameters of amino acids within protein contact networks depend on their physico-chemical properties?

The three dimensional structure of a protein is determined by the interactions of its constituent amino acids. Considering the amino acids as nodes and the non-bonded interactions among them in 3D space as edges, researchers have constructed protein contact networks and analyzed the values of several topological parameters to uncover different important aspects of proteins. Here, we have analyzed some of the topological parameters such as degree, strength, clustering coefficients, betweenness and closeness centrality of each of the twenty amino acids in a set of non-redundant proteins covering all classes and folds. The results show that the values of these topological parameters vary widely with different amino acids. Also, these values differ significantly with different length scales of proteins. Most of the hydrophobic residues along with Cys, Arg and His have larger contributions to the long range connectivities than short range. We have also studied whether the values of topological parameters have any significant dependency on the physico-chemical properties of the amino acids. While the clustering coefficients show a strong negative correlation with residual volumes, surface areas and number of atoms in the side chains of amino acids; the degrees, strengths and betweenness show positive correlations with the mentioned properties. All the topological parameters show high dependency on bulkiness and average area buried of the amino acid residues in all-range residue networks. The average degree shows higher dependency on hydrophobicity, while the average strength is more able to capture the essences of surface area, residual volume and number of atoms of amino acids. The hydrophobicities of the amino acids and their corresponding degrees show a higher positive correlation in long range networks (LRNs) than short range networks (SRNs). The closeness centrality shows high correlation with two hydrophobic scales and no correlation with surface area, residual volume or number of atoms in LRNs. We have further explored the relationship in hydrophobic, hydrophilic and charged residues separately. Interestingly, charged residues show a higher dependency on the number of atoms than their residual volumes and surface areas. Finally, we present a linear regression model relating the network parameters with physico-chemical properties of amino acids.     

Refrigerated shelf-life evaluation of high pressure processed,raw and sous vide cooked lobster

ABSTRACT

High pressure processing (HPP) and sous vide may increase the shelf-life of high value seafood products without the use of additives. This study investigated the effects of 150MPa or 350MPa for 10min on microbial, sensory, and physicochemical qualities of raw and subsequently sous vide cooked (65°C) lobster tails during 28 days of refrigerated storage. Raw lobster pressurized at 350MPa or sous vide cooked maintained significantly lower microbial counts, total volatile base nitrogen, and biogenic amine levels. Due to off-odors, 90% and 60% of sensory respondents rejected the control and 150MPa raw samples, respectively, by day 7, while 70% rated the 350MPa samples as still acceptable on day 28. For cooked lobster, only 20% of the respondents rejected any samples by day 28. Moderate HPP conditions were effective in extending refrigerated shelf-life of vacuum-packaged raw lobster tails. However, HPP pretreatment did not contribute to additional shelf-life extension for sous vide cooked products.     

Poly(azomethine) Rotaxanes: Novel Water Soluble Supramolecular Polymers with High Molar Mass

A novel type of supramolecular poly(azomethine) was synthesized by the polycondensation of an inclusion complex of β‐cyclodextrin/poly(oxypropylene)diamine with one of β‐cyclodextrin/terephthaldehyde and a subsequent reaction with [60]fullerene as the end capping agent. Molar mass determination by gel permeation chromatography showed that the polymers had a high molar mass (about 150 kg · mol⁻¹) with a very narrow polydispersity. Isothermal titration calorimetric studies confirmed that each poly‐(oxypropylene)diamine unit could host seven cyclodextrin molecules, which was further supported by ¹H NMR spectroscopy and molecular modeling studies. Additional characterization by ¹³C NMR and FT‐IR spectroscopy, as well as by thermogravimetric analysis, confirmed the structure of the cyclodextrin‐based polyrotaxane.