An approximation analysis for an assembly-like queueing system with time-constraint items

We study an assembly-like queueing system one of whose queues has items with generally distributed time-constraints, where this system has a single server providing services using each item individually. It is well-known that analysis of a queueing system which has items with time-constraint (i.e., impatient items) is difficult since the analytical model must involve all the departure times of these impatient items. We therefore propose to employ the techniques of Whitt’s approximation and show the method for obtaining the stationary distribution of the model. Through some simulation experiments, we discuss the validation of our approximation model, and show that the approximation is accurate in various kinds of situations (e.g., service time distribution and the number of queues).     

Formation of an exciplex with mixed ligands in the mercury-photosensitized luminescence of alcohol-amine mixtures in the liquid phase

The liquid-phase mercury-photosensitized luminescence of tert-butyl alcohol (TL)-tert-butylamine (TM) mixtures has been investigated by a steady-state illumination method over a wide range of substrate concentrations. The emission bands from exciplexes (HgTL* and HgTM*) between an excited mercury atom and an alcohol or an amine molecule were observed at about 330 nm and 370 nm, respectively, in TL and TM solutions in cyclohexane. Two other bands appeared at 405 nm and 455 nm for TM at high concentrations. These bands were previously assigned to two types of 1:2 exciplexes (HgTM(2)* and HgTM(2)**). In TL-TM mixed solutions, a new band appeared at about 400 nm. The intensity of this band increased with increasing concentrations of TL and TM. This band was attributed to an exciplex with mixed ligands (HgTLTM*). This band was observed for the first time in this study. The energized intermediate, (HgTLTM*)(not equal), formed between HgAL* and AM can be effectively stabilized by collisions with solvent molecules in solution, while it decomposes to HgAM* and AL in the gas phase. The results for TL-TM mixtures can be explained by the proposed reaction mechanism.     

Photoinduced omega-bond dissociation of m-halomethylbenzophenones studied by laser photolysis techniques and DFT calculations. Substituted position effects

Photochemical profiles of omega-cleavage of carbon-X (X = Br and Cl) bonds in m-bromo- and m-chloromethylbenzophenones (m-BMBP and m-CMBP) were investigated by laser photolysis techniques and DFT calculations. m-BMBP and m-CMBP were found to undergo omega-bond cleavage to yield the m-benzoylbenzyl radical (m-BBR) at 295 K, and the quantum yields were determined. No CIDEP signal was detected upon 308 nm laser photolysis of both the compounds. From these observations, it was inferred that the omega-bond of these m-halomethylbenzophenones (m-HMBP) cleaves in the lowest excited singlet state (S(1)(n,pi(*))) upon direct excitation. Upon triplet sensitization of acetone (Ac), the m-BBR formation was observed in transient absorption for an Ac-m-BMBP system, and an efficiency of the C-Br bond cleavage in the lowest triplet state (T(1)(n,pi(*))) of m-BMBP was determined. In contrast, formation of triplet m-CMBP was seen for an Ac-m-CMBP system. Absence of C-Cl bond cleavage in the triplet state of m-CMBP indicated the reactive state of m-CMBP for omega-cleavage is only the S(1)(n,pi(*)) state. Based on the efficiencies and DFT calculations for excited state energies, photoinduced omega-bond dissociation of m- and p-HMBPs was characterized.     

Ising vectors and automorphism groups of commutant subalgebras related to root systems

In this article we study and obtain a classification of Ising vectors in vertex operator algebras (VOAs) associated to binary codes and times root lattices, where an Ising vector is a conformal vector with central charge 1/2 generating a simple Virasoro sub-VOA. Then we apply our results to study certain commutant subalgebras related to root systems. We completely classify all Ising vectors in such commutant subalgebras and determine their full automorphism groups. C. H. Lam was supported by NSC grant 93-2115-M-006-012 of Taiwan and National Center for Theoretical Sciences, Taiwan, S. Sakuma was supported by JSPS Research Fellowships for Young Scientists and H. Yamauchi was supported by JSPS Research Fellowships for Young Scientists     

Synthesis of phenyl furyl sulfides and phenyl furyl ethers by nucleophilic substitution of nitrofurans

Phenyl furyl sulfides ( 3a‐j ) and phenyl furyl ethers ( 3k‐n ), which are useful in synthesizing furocondensed 3‐ring compounds, can be synthesized by nucleophilic substitution of nitrofurans having electron withdrawal groups. In our experiments using 5‐nitrofurans having electron withdrawal groups ( 2a‐i ), nucleophilic substitution readily occurred with the benzenethiolate anion of thiosalicylic acid ( 1a ), the benzenethiolate anion of thiosalicylate ester ( 1b ), and the phenylate anions of salicylate esters ( 1c‐d ) to yield phenyl furyl sulfides ( 3a‐j ) and phenyl furyl ethers ( 3k‐n ).     

Ab initio MO study of the chlorophyll dimer in the photosynthetic reaction center. I. A theoretical treatment of the electrostatic field created by the surrounding proteins

The charge separation occurring in the photosynthetic reaction center is the primary subject in order to understand the whole photosynthetic process. In this article, the electronic structures of the chlorophyll dimer, in which photoexcitation occurs, are investigated by using the ab initio molecular orbital scheme and pseudocharges and dipoles method which takes into account the electrostatic effect of the surrounding proteins, pigments, and aqueous solvent. As a first step, the ionization potentials of BCmp, BCIp, and the dimer of Rhodopseudomonas viridis are computed to study the characteristic of each molecule toward the elucidation of the primary charge separation. It has been found, from the present calculations, that BCmp and BClp constituting the dimer are not equivalent in their electronic ground states, since the electron could be removed more easily from BCmp than from BClp for two reasons: (1) the distorted molecular plane of Cmp, and (2) the effects of the surrounding electrostatic potentials to BCmp and BCIp. This tendency is further strengthened by the polarization of the environment, when, to the ab initio MO calculation, the contribution from the induced dipoles of the neighboring atoms in the proteins and other chromophores is included. From the present application, induced electric dipoles are found to be important to describe the molecular electronic structures affected by proteins. © 1997 John Wiley & Sons, Inc.     

A counterexample to the bold conjecture

A pair of vertices (x,y) of a graph G is an o-critical pair if o(G + xy) > o(G), where G + xy denotes the graph obtained by adding the edge xy to G and o(H) is the clique number of H. The o-critical pairs are never edges in G. A maximal stable set S of G is called a forced color class of G if S meets every o-clique of G, and o-critical pairs within S form a connected graph. In 1993, G. Bacsó raised the following conjecture which implies the famous Strong Perfect Graph Conjecture: If G is a uniquely o-colorable perfect graph, then G has at least one forced color class. This conjecture is called the Bold Conjecture. Here we show a simple counterexample to it. © 1997 John Wiley & Sons, Inc. J Graph Theory 25: 165–168, 1997     

Detection of diminished response to cold pressor test in smokers: Assessment using phase-contrast cine magnetic resonance imaging of the coronary sinus

Purpose

The purposes of this study were to evaluate the reproducibility for measuring the cold pressor test (CPT)-induced myocardial blood flow (MBF) alteration using phase-contrast (PC) cine MRI, and to determine if this approach could detect altered MBF response to CPT in smokers.

Materials and methods

After obtaining informed consent, ten healthy male non-smokers (mean age: 28 ± 5 years) and ten age-matched male smokers (smoking duration ≥ 5 years, mean age: 28 ± 3 years) were examined in this institutional review board approved study. Breath-hold PC cine MR images of the coronary sinus were obtained with a 3 T MR imager with 32 channel coils at rest and during a CPT performed after immersing one foot in ice water. MBF was calculated as coronary sinus flow divided by the left ventricular (LV) mass which was given as a total LV myocardial volume measured on cine MRI multiplied by the specific gravity (1.05 g/mL).

Results

In non-smokers, MBF was 0.86 ± 0.25 mL/min/g at rest, with a significant increase to 1.20 ± 0.36 mL/min/g seen during CPT (percentage change of MBF (?MBF (%)); 39.2% ± 14.4%, p < 0.001). Inter-study reproducibility for ?MBF (%) measurements by different MR technologist was good, as indicated by the intraclass correlation coefficient of 0.93 and reproducibility coefficient of 10.5%. There was no significant difference between smokers and non-smokers for resting MBF (0.85 ± 0.32 mL/min/g, p = 0.91). However, ?MBF (%) in smokers was significantly reduced (-4.0 ± 32.2% vs. 39.2 ± 14.4%, p = 0.011).

Conclusion

PC cine MRI can be used to reproducibly quantify MBF response to CPT and to detect impaired flow response in smokers. This MR approach may be useful for monitoring the sequential change of coronary blood flow in various potentially pathologic conditions and for investigating its relationship with cardiovascular risk.     

Free Infinite Divisibility of Free Multiplicative Mixtures of the Wigner Distribution

Let I ^* and I ^⊞ be the classes of all classical infinitely divisible distributions and free infinitely divisible distributions, respectively, and let Λ be the Bercovici–Pata bijection between I ^* and I ^⊞ . The class type W of symmetric distributions in I ^⊞ that can be represented as free multiplicative convolutions of the Wigner distribution is studied. A characterization of this class under the condition that the mixing distribution is 2-divisible with respect to free multiplicative convolution is given. A correspondence between symmetric distributions in I ^⊞ and the free counterpart under Λ of the positive distributions in I ^* is established. It is shown that the class type W does not include all symmetric distributions in I ^⊞ and that it does not coincide with the image under Λ of the mixtures of the Gaussian distribution in I ^*. Similar results for free multiplicative convolutions with the symmetric arcsine measure are obtained. Several well-known and new concrete examples are presented.     

Rhodium(I)-catalyzed asymmetric 1,4-addition of arylboronic acids to alpha,beta-unsaturated amides.

The conjugate addition of arylboronic acids to alpha,beta-unsaturated amides was carried out in the presence of a chiral rhodium catalyst and an aqueous base. The catalyst prepared in situ from Rh(acac)(CH(2)=CH(2))(2) and (S)-binap provided (R)-N-benzyl-3-phenylbutanamide with 93% ee in the addition of phenylboronic acid to N-benzyl crotonamide. The reaction suffered from incomplete conversion resulting in moderate yields, but addition of an aqueous base, such as K(2)CO(3) (10-50 mol%) was found to be highly effective to improve the chemical yields. The role of the base giving a RhOH species active for transmetalation with arylboronic acids was discussed.