A single server queue with cyclically indexed arrival and service rates

In this paper we consider a queueing model that results from at least two apparently unrelated areas. One motivation to study a system of this type results from a test case of a computer simulation factor screening technique calledfrequency domain methodology. A second motivation comes from manufacturing, where due to cyclic scheduling of upstream machines, the arrival process to downstream machines is periodic. The model is a single server queue with FIFO service discipline and exponential interarrival and service times where the arrival and/or service rates are deterministic cyclic functions of the customer sequence number. We provide steady state results for the mean number in the system for the model with cyclic arrival and fixed service rates and for the model with fixed arrival and cyclic service rates. For the model with both cyclic arrival and service rates, upper and lower bounds are developed for the steady state mean waiting time in the system. Throughout the paper various implications and/or insights derived from the results of this study are discussed for frequency domain methodology.The authors acknowledge the financial support of the CBA/GSB Faculty Research Committee of the College of Business Administration, The University of Texas at Austin.     

Silica chloride: An efficient promoter for oxidation of arylboronic acids to phenols

This work reports simple, highly efficient protocol for the oxidation of arylboronic acids. Various arylboronic acids were selectively and completely converted into their corresponding oxidized phenols using H₂O₂ as an oxidant in presence of catalytic amount of silica chloride. The results show that silica chloride is a suitable and efficient promoter for the oxidation of arylboronic acids. Heterogeneous catalyst, mild reaction conditions, easy availability of the reagent, easy work-up, excellent yield of corresponding phenols, short reaction time and broad substrate scope makes this protocol attractive and a practical alternative to the existing methods.     

CARBON-14 LABELING AND BIOLOGICAL ACTIVITY OF THE TUMOR-LOCALIZING DERIVATIVE OF HEMATOPORPHYRIN

Abstract— Carbon-14-labeled hematoporphyrin ([¹⁴C]HP) was synthesized by two methods, (i) Using an in vitro avian whole-blood system, [¹⁴C]protoheme was obtained biosynthetically by incorporating [⁴C]aminolevulinic acid into the porphyrin ring structure. Subsequently, the [¹⁴C]protoheme was converted to [⁴C]HP by standard procedures, (ii) By adopting several well-characterized chemical reactions, deuteroporphyrin was treated with [¹⁴C]acetyl chloride, giving [¹⁴C]diacetyl deuteroporphy-rin which was readily reduced and hydrolyzed to [¹⁴C]HP (with thecarbon–14 label on the hydroxyethyl side-chains). These two methods are simple and afford good yields of [¹⁴C]HP with moderate to high specific activities. The [¹⁴C]HP was then treated with acetic acid/sulfuric acid followed by sodium hydroxide to give [¹⁴C]HPD. Upon gel- and ultra-filtration, the [¹⁴C]HPD was enriched in the so-called tumor-localizing fraction of HPD, giving [¹⁴C]PII with specific activities of 0.4 Ci/mol (biosynthesis) and 10 Ci/mol (chemical synthesis). These [¹⁴C]PII preparations were equivalent with respect to chromatographic and spectrophotometric characteristics, as well as tumoricidal photodynamic activity in the DBA/2 Ha-DD mouse: SMT-F tumor system, to the unlabeled commercial product Photofrin^? II. The distribution of [¹⁴C]PII in mouse tissues was in close agreement to that previously reported, after adjustment for dose, for [¹⁴C]HPD biosynthetically labeled in vivo (Gomer and Dougherty, 1979), as well as for Photofrin^? II, where tissue levels were determined spectrophotometrically after extraction (Dougherty and Mang, unpublished).     

New network architecture for stoichiometrically,thermodynamically and kinetically balanced metabolic reaction systems

The conventional way of assembling the metabolic reactions into networks by placing the metabolites on the nodes and associating the edges with reactions is shown to violate the mass balance, thermodynamics and kinetics. A new type of metabolic networks referred to as reaction route (RR) networks is discussed. The distinct feature of the RR networks is that both the nodes and edges are subject to mass balance, thermodynamic and kinetic constraints. To satisfy these constraints, it is necessary to introduce two different types of nodes. One of these, referred to as terminal nodes, satisfy the mass balance conditions for external metabolites. The other type of nodes, referred to as intermediate nodes, satisfy the quasi steady-state conditions for internal metabolites. It is further required that every cycle in the network be thermodynamically consistent in that the sum of affinities (Gibbs free energy changes) of the reactions comprising the cycle should add up to zero. A balanced RR metabolic network possesses a remarkable property, namely, every conceivable walk between two terminal nodes involves a sequence of metabolic reaction steps that produce an overall reaction (OR), i.e., a reaction comprising only external metabolites. A key result is that many metabolic reaction networks may be balanced if and only if the network is allowed to be infinite and periodic.     

Graphene as membrane for encapsulation of yeast cells: protective and electrically conducting

Graphene sheets (chemically reduced), a high modulus and high thermal and electrically conductive material are coupled with yeast cells to form an encapsulating inorganic functional layer. The coupling of the high modulus sheets with the cells increases their stability to osmotic stresses. The sheets also allow the direct visualization of the cells in an electron microscope.     

One-pot efficient synthesis of dimeric, trimeric, and tetrameric BODIPY dyes for panchromatic absorption

One-pot Knoevenagel self-condensation reaction of β-formyl BODIPY dye bearing a formyl group at 2-position offered dimeric, trimeric and tetrameric BODIPY dyes containing a formyl capping end group, exhibiting panchromatic absorption.     

Enantioselective syntheses of (+)-sertraline and (+)-indatraline using lithiation/borylation-protodeboronation methodology

The lithiation/borylation-protodeboronation of a homoallyl carbamate was applied to the synthesis of (+)-sertraline and (+)-indatraline. Due to the presence of the alkene, significant modifications of the methodology were required (use of 12-crown-4, TMSCl, H(2)O), or a solvent switch to CHCl(3), to achieve high yields and high selectivities.     

Development and validation of a highly sensitive LC-MS/MS method for simultaneous quantitation of acetyl-CoA and malonyl-CoA in animal tissues

A highly sensitive and specific LC‐MS/MS method was developed for simultaneous estimation of acetyl co‐enzyme A (ACoA) and malonyl co‐enzyme A (MCoA) in surrogate matrix using n‐propionyl co‐enzyme A as an internal standard (IS). LC‐MS/MS was operated under the multiple reaction‐monitoring mode using the electrospray ionization technique. Simple acidification followed by dilution using an assay buffer process was used to extract ACoA, MCoA and IS from surrogate matrix and tissue samples. The total run time was 3 min and the elution of both analytes (ACoA, MCoA) and IS occurred at 1.28 min; this was achieved with a mobile phase consisting of 5 mM ammonium formate (pH 7.5)–acetonitrile (30:70, v/v) delivered at a flow rate of 1 mL/min on a monolithic RP‐18e column. A linear response function was established for the range of concentrations 1.09–2187 and 1.09–2193 ng/mL for ACoA and MCoA, respectively. The intra‐ and inter‐day precision values for ACoA and MCoA met the acceptance as per FDA guidelines. ACoA and MCoA were stable in a battery of stability studies viz. bench‐top, auto‐sampler and long‐term. The developed assay was used to quantitate ACoA and MCoA levels in various tissues of rat. Copyright © 2011 John Wiley & Sons, Ltd.