DNA reorientation on Au nanoparticles: label-free detection of hybridization by surface enhanced Raman spectroscopy

DNA sequences attached to Au nanoparticles via thiol linkers stand up from the surface, giving preferential enhancement of the adenine ring breathing SERS band. Non-specific binding via the nucleobases reorients the DNA, reducing this effect. This change in intensity on reorientation was utilised for label-free detection of hybridization of a molecular beacon.     

Synthesis,Photophysical, and Two‐Photon Absorption Properties of Elongated Phosphane Oxide and Sulfide Derivatives

A series of rod‐shaped and related three‐branched push–pull derivatives containing phosphane oxide or phosphane sulfide (PO or PS)—as an electron‐withdrawing group conjugated to electron‐donating groups, such as amino or ether groups, with a conjugated rod consisting of arylene–vinylene or arylene–ethynylene building blocks—were prepared. These compounds were efficiently synthesized by a Grignard reaction followed by Sonogashira coupling. Their photophysical properties including absorption, emission, time‐resolved fluorescence, and two‐photon absorption (TPA) were investigated with special attention to structure–property relationships. These fluorophores show high fluorescence quantum yields and solvent‐dependent experiments reveal that efficient intramolecular charge transfer occurs upon excitation, thereby leading to highly polar excited states, the polarity of which can be significantly enhanced by playing on the end groups and conjugated linker. Rod‐shaped and related three‐branched systems show similar fluorescence properties in agreement with excitation localization on one of the push–pull branches. By using stronger electron donors or replacing the arylene–ethynylene linkers with an arylene–vinylene one induces significant redshifts of both the low‐energy one‐photon absorption and TPA bands. Interestingly, a major enhancement in TPA responses is observed, whereas OPA intensities are only weakly affected. Similarly, phosphane oxide derivatives show similar OPA responses than the corresponding sulfides but their TPA responses are significantly larger. Finally, the electronic coupling between dipolar branches promoted by common PO or PS acceptor moieties induces either slight enhancement of the TPA responses or broadening of the TPA band in the near infrared (NIR) region. Such behavior markedly contrasts with triphenylamine‐core‐mediated coupling, which gives evidence for the different types of interactions between branches.     

Rings with Commuting Nilpotents and Zero Divisors

We explore the consequences of certain commutativity hypotheses on a single nilpotent element or the set N of all nilpotent elements. We give several sufficient conditions for N to be an ideal. We present some nontrivial examples, including an example in which N is commutative (in fact, N ² = {0}) and N is not an ideal. Received: April 27, 2006. Revised: July 31, 2006.     

Optimality conditions at junctions of singular and nonsingular controls

Some necessary conditions for the optimality of junctions between singular and nonsingular subarcs arising in optimal control problems are well established. The second part of McDanell's conjecture has been proved false. The first part still awaits verification or otherwise. This paper briefly summarizes previous work and presents some evidence to suggest that the first part of the conjecture is also false.     

A Near-Commutativity Property for Rings

We revisit rings with the property that |A ²| ≤ 3 for each 2-subset A. We then investigate commutativity of rings R with the property that for each pair a, b of noncommuting elements of R, there exists an integer n > 1 for which a ⁿ = b ⁿ .     

The effect of market segmentation with demand leakage between market segments on a firm’s price and inventory decisions

In this paper, we address the simultaneous determination of price and inventory replenishment in a newsvendor setting when the firm faces demand from two or more market segments in which the firm can set different prices. We allow for demand leakage from higher-priced segments to lower-priced segments and assume that unsatisfied demand can be backlogged. We examine the case where the demands occur concurrently without priority and are met from a single inventory. We consider customer’s buy-down behavior explicitly by modeling demand leakage as a function of segment price differentiation, and characterize the structure of optimal inventory and pricing policies.     

Management decision-making in the single period optimum pricing problem

Management of the firm implementing revenue management has many decisions to make regarding the details of the implementation. In this article we examine seven different decisions surrounding the implementation of aggressive ‘revenue management’ pricing in the context of a firm facing a single period stochastic pricing and stocking problem. We demonstrate through use of an example, that some of the decisions have a large financial impact, while other options that require considerable computational work to implement may provide little financial impact.