Priority option pricing in an M/M/m queue

We study a system where the service provider offers priority options. We identify the optimal option pricing policy, by deriving the optimal number a customer would buy and the customer’s exercise policy as a function of system congestion, options remaining, time to expiration and possibility of balking.     

A new graph parameter related to bounded rank positive semidefinite matrix completions

The Gram dimension $\mathrm{gd}(G)$ of a graph $G$ is the smallest integer $k\ge 1$ such that any partial real symmetric matrix, whose entries are specified on the diagonal and at the off-diagonal positions corresponding to edges of $G$ , can be completed to a positive semidefinite matrix of rank at most $k$ (assuming a positive semidefinite completion exists). For any fixed $k$ the class of graphs satisfying $\mathrm{gd}(G) \le k$ is minor closed, hence it can be characterized by a finite list of forbidden minors. We show that the only minimal forbidden minor is $K_{k+1}$ for $k\le 3$ and that there are two minimal forbidden minors: $K_5$ and $K_{2,2,2}$ for $k=4$ . We also show some close connections to Euclidean realizations of graphs and to the graph parameter $\nu ^=(G)$ of van der Holst (Combinatorica 23(4):633–651, 2003). In particular, our characterization of the graphs with $\mathrm{gd}(G)\le 4$ implies the forbidden minor characterization of the 3-realizable graphs of Belk (Discret Comput Geom 37:139–162, 2007) and Belk and Connelly (Discret Comput Geom 37:125–137, 2007) and of the graphs with $\nu ^=(G) \le 4$ of van der Holst (Combinatorica 23(4):633–651, 2003).     

Antioxidants and inflammatory disease: synthetic and natural antioxidants with anti-inflammatory activity

Oxidants play a significant role in the pathogenesis of a number of disorders such as inflammation, rheumatoid arthritis, asthma, psoriasis and contact dermatitis leading to oxidative stress. Oxidative stress may be defined as an imbalance between cellular production of reactive oxygen species (ROS) and antioxidant defense mechanisms. ROS (e.g., superoxide radical, peroxynitryl, hydroxyl radical and hydrogen peroxide) are constantly produced as a result of metabolic reactions in living systems. The aim of this review is to describe recent developments in the study of antioxidants and their role in preventing the formation of ROS. The processes associated with inflammatory responses are complex and often involve ROS. There are many mediators, which initiate and amplify the inflammatory response such as histamine, serotonin, pro-inflammatory cytokines (interleukin-1B (IL-1b) and tumor necrosis factor (TNF-alpha), inflammatory cells (leukotrienes, macrophages), metabolic products of arachidonic acid (thomboxane A(2), prostaglandins and leukotrienes). The first part of this review focuses on the role of ROS in inflammation. The second part concerns synthetic antioxidants with antiinflammatory activity, and the third part addresses naturally occurring antioxidants with antiinflammatory activity.     

Determination of polychlorinated biphenyls by liquid chromatography–atmospheric pressure photoionization–mass spectrometry

This study presents the atmospheric pressure photoionization (APPI) of high‐chlorinated (five or more chlorine atoms) polychlorinated biphenyls (PCBs) using toluene as dopant, after liquid chromatographic separation. Mass spectra of PCB 101, 118, 138, 153, 180, 199, 206 and 209 were recorded by using liquid chromatography‐APPI‐tandem mass spectrometry (LC‐APPI‐MS/MS) in negative ion full scan mode. Intense peaks appeared at m/z that correspond to [M ? Cl + O]^? ions, where M is the analyte molecule. Furthermore, a detailed strategy, which includes designs of experiments, for the development and optimization of LC‐APPI‐MS/MS methods is described. Following this strategy, a sensitive and accurate method with low instrumental limits of detection, ranging from 0.29 pg for PCB 209 to 8.3 pg for PCB 101 on column, was developed. For the separation of the analytes, a Waters XSELECT HSS T3 (100 mm × 2.1 mm, 2.5 µm) column was used with methanol/water as elution system. This method was applied for the determination of the above PCBs in water samples (surface water, tap water and treated wastewater). For the extraction of PCBs from water samples, a simple liquid–liquid extraction with dichloromethane was used. Method limits of quantification, ranged from 4.8 ng l^?1, for PCB 199, to 9.4 ng l^?1, for PCB 180, and the recoveries ranged from 73%, for PCB 101, to 96%, for PCB 199. The estimated analytical figures were appropriate for trace analysis of high‐chlorinated PCBs in real samples. Copyright © 2014 John Wiley & Sons, Ltd.     

A Diastereoselective Synthesis of trans/cis Octahydronaphthoquinolizine

The tetracyclic system of 2,3,6,7,7a,8,12b,12c-octahydro-lH,5H-naphtho[1,2,3,i,j]quinolizine with trans/cis fusions of the B/D and B/C rings has been diastereospecifically synthesized in nine steps and in 23% total yield.     

Development of an in vitro confinement test to predict the clinical handling of polymer-based injectable bone substitutes

The objective of the current study was to present a simple and standardized system as a preliminary attempt to assess the confinement of polymer-based injectable bone substitutes (IBSs) in vitro. Four different types of polymer-based IBSs were selected as model compounds, a thermosensitive collagen gel, a colloidal gelatin gel, a covalently crosslinked oligo(poly(ethylene glycol)fumarate (OPF) gel and a OPF-calcium phosphate composite. A ceramic-based IBS (i.e. a self-setting calcium phosphate cement) was used as reference. The confinement of all IBSs was tested under three different conditions: (1) no flow (as control), (2) dynamic flow after injection and (3) dynamic flow during injection. The results presented herein confirmed that the proposed test can be used to quantify the confinement of various IBSs within artificial defects under static or dynamic flow conditions, thereby offering a potential tool for predictive quantitative determination of the confinement of IBSs in vivo.     

Selective and Wash‐Resistant Fluorescent Dihydrocodeinone Derivatives Allow Single‐Molecule Imaging of μ‐Opioid Receptor Dimerization

μ‐Opioid receptors (μ‐ORs) play a critical role in the modulation of pain and mediate the effects of the most powerful analgesic drugs. Despite extensive efforts, it remains insufficiently understood how μ‐ORs produce specific effects in living cells. We developed new fluorescent ligands based on the μ‐OR antagonist E‐p‐nitrocinnamoylamino‐dihydrocodeinone (CACO), that display high affinity, long residence time and pronounced selectivity. Using these ligands, we achieved single‐molecule imaging of μ‐ORs on the surface of living cells at physiological expression levels. Our results reveal a high heterogeneity in the diffusion of μ‐ORs, with a relevant immobile fraction. Using a pair of fluorescent ligands of different color, we provide evidence that μ‐ORs interact with each other to form short‐lived homodimers on the plasma membrane. This approach provides a new strategy to investigate μ‐OR pharmacology at single‐molecule level.     

Complex frequency shifted convolution PML for FDTD modelling of elastic waves

The perfectly matched layer (PML) is nowadays considered as the best optimum absorbing boundary condition available. However, the PML with the classical stretching tensor has certain limitations. Strangely, these limitations have rarely been addressed in elastic wave modelling. For example, substantial reflections occur when strong evanescent waves are propagating parallel to the interface. To circumvent problems like this, the complex frequency shifted stretching tensor has been introduced in electromagnetic modelling. In this paper we show that the convolution PML with this stretching tensor as used in electromagnetic modelling can be adapted for elastic wave modelling. Numerical results of a model where the presence of evanescent waves is predominant show that the PML based on the complex frequency shifted stretching tensor can improve the performance of the absorbing boundary layer considerably.     

Δ(1232) axial charge and form factors from lattice QCD

We present the first calculation on the Δ axial?vector and pseudoscalar form factors using lattice QCD. Two Goldberger-Treiman relations are derived and examined. A combined chiral fit is performed to the nucleon axial charge, N to Δ axial transition coupling constant and Δ axial charge.