Nanoparticle‐Imprinted Polymers for Size‐Selective Recognition of Nanoparticles

Citrate‐stabilized gold nanoparticles 15 nm and 33 nm in diameter were transferred concomitantly with a monolayer of positively charged polyaniline by Langmuir–Blodgett transfer at pH 5 onto a conducting indium‐doped tin oxide (ITO) support. Films consisting of one to three layers of polyaniline with thicknesses of 1–3 nm were prepared and characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), and X‐ray photoelectron spectroscopy. After electro‐oxidation of the Au nanoparticles in 0.1 M KCl, cavities were left behind in the film that could be analyzed by SEM. These cavities were able to recapture analyte nanoparticles from a solution of pH 10 and showed size‐exclusion properties. The amount of nanoparticles taken up by the cavities was conveniently analyzed by measuring the charge associated with the electro‐oxidation of these particles in 0.1 M KCl after the film had been rinsed with water. The size‐exclusion properties improved with the number of Langmuir–Blodgett layers transferred.     

Biosensors for the analysis of food- and waterborne pathogens and their toxins

Biosensors are devices which combine a biochemical recognition element with a physical transducer. There are various types of biosensors, including electrochemical, acoustical, and optical sensors. Biosensors are used for medical applications and for environmental testing. Although biosensors are not commonly used for food microbial analysis, they have great potential for the detection of microbial pathogens and their toxins in food. They enable fast or real-time detection, portability, and multipathogen detection for both field and laboratory analysis. Several applications have been developed for microbial analysis of food pathogens, including E. coli O157:H7, Staphylococcus aureus, Salmonella, and Listeria monocytogenes, as well as various microbial toxins such as staphylococcal enterotoxins and mycotoxins. Biosensors have several potential advantages over other methods of analysis, including sensitivity in the range of ng/mL for microbial toxins and <100 colony-forming units/mL for bacteria. Fast or real-time detection can provide almost immediate interactive information about the sample tested, enabling users to take corrective measures before consumption or further contamination can occur. Miniaturization of biosensors enables biosensor integration into various food production equipment and machinery. Potential uses of biosensors for food microbiology include online process microbial monitoring to provide real-time information in food production and analysis of microbial pathogens and their toxins in finished food. Biosensors can also be integrated into Hazard Analysis and Critical Control Point programs, enabling critical microbial analysis of the entire food manufacturing process. In this review, the main biosensor approaches, technologies, instrumentation, and applications for food microbial analysis are described.     

Derivatives for smooth representations of <Emphasis Type="Italic">GL</Emphasis>(<Emphasis Type="Italic">n</Emphasis>, ℝ) and <Emphasis Type="Italic">GL</Emphasis>(<Emphasis Type="Italic">n</Emphasis>, ℂ)

The notion of derivatives for smooth representations of GL(n, ? _p ) was defined in [BZ77]. In the archimedean case, an analog of the highest derivative was defined for irreducible unitary representations in [Sah89] and called the “adduced” representation. In this paper we define derivatives of all orders for smooth admissible Fréchet representations of moderate growth. The real case is more problematic than the p-adic case; for example, arbitrary derivatives need not be admissible. However, the highest derivative continues being admissible, and for irreducible unitarizable representations coincides with the space of smooth vectors of the adduced representation.In the companion paper [AGS] we prove exactness of the highest derivative functor, and compute highest derivatives of all monomial representations.We apply those results to finish the computation of adduced representations for all irreducible unitary representations and to prove uniqueness of degenerate Whittaker models for unitary representations, thus completing the results of [Sah89, Sah90, SaSt90, GS13a].     

A partial analog of the integrability theorem for distributions on p-adic spaces and applications

Let X be a smooth real algebraic variety. Let ξ be a distribution on it. One can define the singular support of ξ to be the singular support of the D _X -module generated by ξ (sometimes it is also called the characteristic variety). A powerful property of the singular support is that it is a coisotropic subvariety of T*X. This is the integrability theorem (see [KKS, Mal, Gab]). This theorem turned out to be useful in representation theory of real reductive groups (see, e.g., [AG4, AS, Say]). The aim of this paper is to give an analog of this theorem to the non-Archimedean case. The theory of D-modules is not available to us so we need a different definition of the singular support. We use the notion wave front set from [Hef] and define the singular support to be its Zariski closure. Then we prove that the singular support satisfies some property that we call weakly coisotropic, which is weaker than being coisotropic but is enough for some applications. We also prove some other properties of the singular support that were trivial in the Archimedean case (using the algebraic definition) but not obvious in the non-Archimedean case. We provide two applications of those results:

• a non-Archimedean analog of the results of [Say] concerning Gel’fand property of nice symmetric pairs
• a proof of multiplicity one theorems for GL _n which is uniform for all local fields. This theorem was proven for the non-Archimedean case in [AGRS] and for the Archimedean case in [AG4] and [SZ].

     

Miniaturized 96-well ELISA chips for staphylococcal enterotoxin B detection using portable colorimetric detector

A previously developed fluorescence sensing platform, combining spatial illumination using electroluminescence (EL) semiconductor strips with charge coupled device (CCD)-based detection (EL-CCD), was adapted to a new 96-well chip for colorimetric immunological assays, enhancing the capabilities of the EL-CCD platform. The modified system was demonstrated using a colorimetric-based enzyme linked immunosorbent assay (ELISA) for detection of staphylococcal enterotoxin B (SEB). Limits of detection (LODs) of 3.9 ng/mL (±2.4 ng/mL) SEB were determined with the ELISA chip measured using the EL-CCD platform, following a standard 4-h ELISA protocol. The LODs were comparable to those obtained using standard 96-well ELISA plates measured using a standard laboratory 96-well plate reader. The miniature 96-well ELISA chip however required as little as 5-μL samples, representing a tenfold reduction in sample volume compared to a standard 96-well ELISA plates. The ELISA chip also demonstrated detection of SEB spiked into various food matrices (milk, mushrooms, and mayonnaise) using limited-to-no sample preparation, with LODs ranging from 3.9 to 18.5 ng/mL depending on the matrix. The EL-CCD platform is versatile, capable of multi-mode detection (e.g., fluorescent and colorimetric along with solution and solid phase assays), and could readily be applied to other field portable or point-of-care applications. Figure Detection of SEB using miniature ELISA chips coupled with a portable electroluminiscent-charge couple device (EL-CCD) detection system. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

On single input controllability for infinite dimensional linear systems

Given a controllable linear system {A, B} where A is a Volterra operator, there exists a vector b in the range of B such that {A, b} is controllable. The case where A is a convolution operator on L²(0, ∞) is discussed and an example is given where a controllable system is not replaceable by a single input controllable system.     

Binding of amino acids to "smart" sorbents: where does hydrophobicity come into play?

Poly(N-isopropylacrylamide) (PNIPA)-based sorbents have been successfully used as sorbents in temperature-sensitive chromatography. Yet, the mechanisms controlling the binding of biochemicals to these sorbents and, therefore, the separation process are not fully understood. In the current work, the role of hydrophobic interactions in the binding of amino acids of different hydrophobicities to PNIPA microgels was studied. Binding experiments were conducted both below (25 degrees C) and above (37 degrees C) the volume-phase transition temperature of the gel. At 25 degrees C, no straightforward correlation between the partition coefficient and the hydrophobicity could be suggested for low hydrophobicity values. Contrary, at higher hydrophobicities the partition coefficient increases with increasing hydrophobicity. This correlation holds for the whole hydrophobicity range at 37 degrees C; however, the binding data suggests two different binding mechanisms of the hydrophilic amino acids and the hydrophobic ones. Isothermal titration calorimetry measurements confirmed this suggestion: The binding of hydrophobic amino acids seems to be driven by hydrophobic interactions, as evident from the positive binding enthalpy and the clear correlation between the amino acid's hydrophobicity and the binding entropy. Contrary, the binding of the hydrophilic amino acids was exothermic, implying a binding mechanism based on specific interactions, most probably hydrogen bonding.     

Extending the current collector into the nanoporous matrix of dye sensitized electrodes

A new type of high surface area TiO(2) electrode for DSSCs is proposed. The new electrode consists of a transparent conductive nanoporous matrix that is coated with a thin layer of TiO(2). This design ensures a distance of several nanometers between the TiO(2)-electrolyte interface and the current collector throughout the nanoporous electrode, in contrast to several micrometers associated with the standard electrode. In addition the new electrode contains inherent screening capability due to the high doping level of the conducting core matrix. Theoretically, this electrode should overcome the collection and image field problems associated with solid-state DSSCs. Using a flat analogue of the new electrode we show that unless the TiO(2) coating is thicker than 6 nm, the electrode performance is very low due to fast recombination. Two mechanisms for the thickness effect on the recombination rate, that are proposed, provide new insight to the DSSC operation.     

Gravity in hyperspin manifolds

We seek the dynamics of a Bergmann manifold: a manifold of dimensionn=N ² supporting a bundle of spinor spaces of dimensionN, and a map from the tangent spaces to the Hermitian spinor forms. Even though the spin-vector is the fundamental variable of the theory, every invariant analytic function depending on and its firstm derivatives alone can be expressed in terms of the chronometric tensorg and its firstm derivatives. Bergmann manifolds of dimensionn > 4 do not have invariant second-order equations for. We find a family of invariant actions which lead tonth-order quasilinear equations of motion on Bergmann manifolds and reduce to the Einstein-Hilbert action forn=2. The resulting gauge particles have spin, 1/2,1, 3/2, and 2.