bluuebunny/crossref_metadata_2025 huggingface dataset:
Minimum‐cost dynamic flows: The series‐parallel case
Authors: Klinz Bettina , Woeginger Gerhard J.
Published: March 2004

A dynamic network consists of a directed graph with capacities, costs, and integral transit times on the arcs. In the minimum‐cost dynamic flow problem (MCDFP), the goal is to compute, for a given dynamic network with source s, sink t, and two integers v and T, a feasible dynamic flow from s to t of value v, obeying the time bound T, and having minimum total cost. MCDFP contains as subproblems the minimum‐cost maximum dynamic flow problem, where v is fixed to the maximum amount of flow that can be sent from s to t within time T and the minimum‐cost quickest flow problem, where is T is fixed to the minimum time needed for sending v units of flow from s to t. We first prove that both subproblems are NP‐hard even on two‐terminal series‐parallel graphs with unit capacities. As main result, we formulate a greedy algorithm for MCDFP and provide a full characterization via forbidden subgraphs of the class 𝒢 of graphs, for which this greedy algorithm always yields an optimum solution (for arbitrary choices of problem parameters). 𝒢 is a subclass of the class of two‐terminal series‐parallel graphs. We show that the greedy algorithm solves MCDFP restricted to graphs in 𝒢 in polynomial time. © 2004 Wiley Periodicals, Inc.
Low‐connectivity network design on series‐parallel graphs
Authors: Raghavan S.
Published: March 2004

Network survivability is a critical issue for modern fiber‐optic telecommunication networks. Networks with alternate routes between pairs of nodes permit users to communicate in the face of equipment failure. In this paper, we consider the following low‐connectivity network design (LCND) problem: Given a graph G = (N, E) and a connectivity requirement di ∈ {0, 1, 2} for each node and edge costs ce for each edge e ∈ E, design a minimum‐cost network that contains at least dst = min{ds, dt} disjoint paths between nodes s and t. We present linear‐time algorithms for both node‐ and edge‐connectivity versions of the problem on series‐parallel graphs. Due to the sparsity of telecommunications networks, this algorithm can be applied to obtain partial solutions and decompositions that may be embedded in a heuristic solution procedure as well as exact solution algorithms for the problem on general graphs. © 2004 Wiley Periodicals, Inc.
The Ring Star Problem: Polyhedral analysis and exact algorithm
Authors: Labbé Martine , Laporte Gilbert , Martín Inmaculada Rodríguez , González Juan José Salazar
Published: March 2004

In the Ring Star Problem, the aim is to locate a simple cycle through a subset of vertices of a graph with the objective of minimizing the sum of two costs: a ring cost proportional to the length of the cycle and an assignment cost from the vertices not in the cycle to their closest vertex on the cycle. The problem has several applications in telecommunications network design and in rapid transit systems planning. It is an extension of the classical location–allocation problem introduced in the early 1960s, and closely related versions have been recently studied by several authors. This article formulates the problem as a mixed‐integer linear program and strengthens it with the introduction of several families of valid inequalities. These inequalities are shown to be facet‐defining and are used to develop a branch‐and‐cut algorithm. Computational results show that instances involving up to 300 vertices can be solved optimally using the proposed methodology. © 2004 Wiley Periodicals, Inc.
The 2‐path network problem
Authors: Dahl Geir , Johannessen Bjarne
Published: March 2004

Given a graph with nonnegative edge weights and a set D of node pairs, the 2‐path network problem requires a minimum weight set of edges such that the induced subgraph contains a path with one or two edges connecting each pair in D. The problem is NP‐hard. We present two integer programming models for the problem and study properties of associated polytopes, including cutting planes. Two approximation algorithms are suggested and analyzed. Some computational experience is reported. © 2004 Wiley Periodicals, Inc.
Do school accountability systems make it more difficult for low‐performing schools to attract and retain high‐quality teachers?
Authors: Clotfelter Charles T. , Ladd Helen F. , Vigdor Jacob L. , Diaz Roger Aliaga
Published: March 2004

Administrative data from North Carolina are used to explore the extent to which that state's relatively
sophisticated school‐based accountability system has exacerbated the challenges that schools serving
low‐performing students face in retaining and attracting high‐quality teachers. Most clear are the
adverse effects on retention rates, and hence on teacher turnover, in such schools. Less clear is the extent to
which that higher turnover has translated into a decline in the average qualifications of the teachers in the
low‐performing schools. Other states with more primitive accountability systems can expect even greater
adverse effects on teacher turnover in low‐performing schools. © 2004 by the Association for Public
Policy Analysis and Management.
The impact of state enterprise zones on urban manufacturing establishments
Authors: Greenbaum Robert T. , Engberg John B.
Published: March 2004

Since the early 1980s, the vast majority of states have implemented enterprise zones. This paper analyzes
urban zones in six states, examining the factors that states use to choose zone locations and the subsequent
effect of the zones on business activity and employment. The source of outcome data is the U.S. Bureau of
Census' longitudinal research database (LRD), which tracks manufacturing establishments over
time. Matched sample and geographic comparison groups are created to measure the impact of zone policy on
employment, establishment, shipment, payroll, and capital spending outcomes. Consistent with previous findings,
the difference‐in‐difference estimates indicate that zones have little effect, on average.
However, by exploiting the establishment‐level data to examine gross as well as net changes, the
analysis finds that zones have a positive effect on the outcomes of new establishments and a negative effect on
the outcomes of previously existing establishments. © 2004 by the Association for Public Policy Analysis
and Management.
Using laboratory experiments for policymaking: An example from the Georgia irrigation reduction auction
Authors: Cummings Ronald G. , Holt Charles A. , Laury Susan K.
Published: March 2004

In recent years, interest has been growing in policy applications of different auction systems. This paper
reports a series of experiments that were used to design and implement an auction in a unique policymaking
environment. In April 2000, the Georgia legislature passed a law that mandated that the state hold an auction in
drought years to pay some farmers to suspend irrigation. This paper reports the results of laboratory
experiments state policymakers used to determine the auction institution that would be used to fulfill the
requirements of this new law. Experimental results are compared with farmers' bidding behavior in the
state‐run irrigation auction used to reduce water usage in Georgia. © 2004 by the Association for
Public Policy Analysis and Management.
Solvation effects of H2O and DMSO on the O—H bond dissociation energies of substituted phenols
Authors: Fu Yao , Liu Rui , Liu Lei , Guo Qing‐Xiang
Published: March 2004

Solvation effects on the O—H homolytic bond dissociation energies (BDEs) of substituted phenols were studied. It was demonstrated that the BDEs measured in solution in general do not equal the BDEs in the gas phase. Detailed theoretical analyses indicated that a long‐range solvation effect (i.e. the interaction between the solvent and the overall dipole moment of the solute) and a short‐range solvation effect (i.e. the hydrogen bonding between the solute and solvent) were both important for the O—H BDEs in water and in DMSO. Neither one of these two factors by itself could fully explain the experimentally observed solvation effect. However, a combination of these two factors, estimated through a semi‐continuum solvation model, was shown to be reasonably successful in explaining the experimental results. Copyright © 2004 John Wiley & Sons, Ltd.
Effect of neighbouring amide group bulkiness on anchimerically assisted ether bond cleavage: Part 7
Authors: Arcelli Antonio , Porzi Gianni , Rinaldi Samuele , Sandri Sergio
Published: March 2004

The effect of the bulkiness of the amide group vicinal to the ether bond on the acid hydrolysis rate of substrates 1b–d was investigated. The kinetic data showed that increased bulkiness of the acyl group has a considerable effect on the reaction rate, accelerating the anchimerically assisted hydrolytic process of the ether bond. A different mechanism is proposed for 1d, which is supported by the thermodynamic activation parameters values. The hydrolysis rate of 1d is about 3 × 105‐fold higher than that of the reference compound. Copyright © 2004 John Wiley & Sons, Ltd.
Theoretical study of the thermolysis reaction of methyl β‐hydroxycarboxylates in the gas phase
Authors: Sánchez Claudia , Quijano Jairo , Notario Rafael
Published: March 2004

Theoretical studies on the thermolysis in the gas phase of three methyl β‐hydroxycarboxylates RR′C(OH)CH2COOCH3, methyl 3‐hydroxypropanoate (primary alcohol, I), methyl 3‐hydroxybutanoate (secondary alcohol, II) and methyl 3‐hydroxy‐3‐methylbutanoate (tertiary alcohol, III), were carried out using ab initio theoretical methods at the MP2/6–31G(d) and MP2/6–311+G(d,p) levels of theory. The pathways describe a mechanism via a six‐membered cyclic transition state, with the formation of an aldehyde or a ketone and an enol intermediate, followed by the tautomerization of this intermediate to methyl acetate. The progress of the reactions was followed by means of the Wiberg bond indices. The results indicate that the transition states are late, and the proton transfer is the more advanced process. The kinetic parameters calculated for the reactions studied agree well with the available experimental results. A theoretical study on the kinetic deuterium isotope primary and α‐ and β‐secondary effects was also carried out. Copyright © 2004 John Wiley & Sons, Ltd.
Kinetic analysis of the asymmetric amplification exhibited by B‐chlorodiisopinocampheylborane
Authors: Moeder Charles W. , Sowa John R.
Published: March 2004

A quantitative investigation was undertaken to determine experimentally the relative reaction rates of the heterochiral and homochiral species of B‐chlorodiisopinocampheylborane (Dip‐Cl), a reagent that exhibits asymmetric amplification. Using the method of flooding to reduce the apparent second‐order reaction to pseudo‐first‐order conditions, rate constants of 3.8 (±1.0) × 10−4 and 1.7 (±0.8) × 10−5 m−1 s−1 (at −15°C) were found for the homochiral and heterochiral species, respectively. The resulting relative reaction rate, the value of g in Kagan and co‐workers' model, was 0.04 ± 0.03. Additional experiments were conducted to confirm this value. The deterioration of the chiral purity of the final product was simulated throughout reaction conversion and compared with actual values. Through minimization, a relative reaction rate (g) of 0.08 ± 0.04 was determined. Finally, using 8‐hydroxyquinoline complexation, the change in isomeric ratio of the Dip‐Cl remaining in the reaction solution was measured. The relative reaction rate (g) required to consume the isomers at the observed rate was determined as 0.08 ± 0.01. Thus, three independent methods have been used to determine the relative reaction rate (g) of the heterochiral to homochiral species with good agreement to give an average value of 0.07 ± 0.03. Copyright © 2004 John Wiley & Sons, Ltd.
Mechanism of acid‐catalysed decomposition of 3‐alkyl‐1,3‐diphenyltriazenes by trichloroacetic acid in hexane
Authors: Pytela Oldřich , Bednář Roman , Kaválek Jaromír
Published: March 2004

Eight 3‐alkyl‐1,3‐diaryltriazenes with methyl, ethyl, propyl, butyl, pentyl, isopropyl, sec‐butyl and cyclohexyl substituents were synthesized and their rate constants of decomposition by trichloroacetic acid (0.01–0.25 mol dm−3) in hexane at 25°C were measured. The kinetic model and mechanism thereof were studied by modelling of the dependences of kobs on the concentration of trichloracetic acid. On the basis of this kinetic model and the interpretation of solvent effects, a reaction mechanism was suggested according to which the triazene reacts with monomer and obviously also opens the dimer of trichloroacetic acid in a single reaction step. At the same time, a non‐reactive associate between the N1 nitrogen of triazene and two molecules of trichloroacetic acid is formed in the reaction mixture. The equilibrium and rate constants depend on the addition of trichloroacetic acid as the co‐solvent. Copyright © 2004 John Wiley & Sons, Ltd.
Stochastic Maxwell–Lorentz equation in radiation damping
Authors: Petrosky T.
Published: March 2004

Radiation damping of an accelerated particle coupled with the field is a classical problem. Still there are difficulties. Time symmetry is broken. So the radiation damping belongs to a class of phenomena that includes transport properties. In a series of our recent articles we proposed a radically new approach based on the extension of the dynamics of integrable systems. There, we considered a simple model: a harmonic oscillator interacting with a field. For integrable systems, it is well known that there exists a unitary transformation U. However, in the radiation damping we have resonances between the action of a charged particle and the actions of the field modes. This makes the system an example of Poincaré nonintegrable systems. We extended the unitary operator to a nonunitary operator Λ. This changes the dynamical description of radiation damping. Once we know the Hamiltonian, we can write the Hamilton equations. But we have the opportunity to go to new descriptions. The invertible Λ transformation gives many new aspects, which are hidden in the initial description. For example, we showed that there are fluctuations in the emitted field. In the current article we apply the Λ transformation to describe the evolution of the emitted field from the charged particle and show that the fluctuations lead to a Langevin equation for the field modes. As a consequence, we have a stochastic wave equation that is an extension of Maxwell–Lorentz equation for classical matter–field interacting systems. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2004
Dissipative extension of quantum mechanics
Authors: de Haan M. , George C. D.
Published: March 2004

A challenging problem facing physicists is the compatibility of irreversibility, as expressed by the second law of thermodynamics, with ordinary quantum mechanics. We present a solution through an extension of the latter. The presence of self‐energy processes (already found in quantum electrodynamics) is fully exploited to get an extension of a reversible formalism. They enable the widening of the dynamics by the introduction of specific auxiliary variables, leading to the recognition of such processes. A projection technique modeled on the one introduced long ago by the Brussels group defines a subdynamics that is shown to contain entirely the starting formulation (it corresponds to a restricted class of initial conditions, namely, the reversible one). A new kinetic description is obtained in which, for example, collision processes for privileged components arise from the original interaction. A very simple model and its generalizations are considered. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2004
Equilibrium and nonequilibrium theory of dilute Bose gases
Authors: Pomeau Yves
Published: March 2004

The explanation of the phenomenon of superfluidity requires an in‐depth analysis of both equilibrium and nonequilibrium statistics. This can be done in dilute gases by a systematic expansion in powers of the density, as done for classical gases in Prigogine's book on kinetic theory. Following the method of expansion of Prigogine and Résibois, the thermodynamics of a dilute gas of N identical Bosons with condensate can be studied in the case of a superflow, that is, of a finite and uniform velocity difference between the normal and superfluid component (assumed at rest). The microscopic interactions between the two components conserve the momentum of the normal component, making it a thermodynamic parameter. No thermal equilibrium exists if the velocity difference is larger than a critical value far below the onset of dissipation given by Landau's criterion. Consequences of this are discussed. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2004
Anomalous transport in plasmas
Authors: Balescu R. , Vlad M. , Spineanu F. , Misguich J.
Published: March 2004

The application of stochastic methods to the problem of particle and energy transport in turbulent plasmas is briefly reviewed. The “classical” Corrsin approximation is shown to be valid only in the limit of weak turbulence. The recently developed method of decorrelation trajectories is applicable over the whole range of turbulence intensities and yields the correct asymptotic behavior in the limit of very strong turbulence (subdiffusion). © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2004
Thermodynamics of a system with long‐time correlations
Authors: Hasegawa Hiroshi H. , Li Chun‐Biu , Ohtaki Yoshikazu
Published: March 2004

We continue our study of the thermodynamics of a system with long‐time correlations. We first demonstrate a fluctuation–dissipation theorem, which relates the excess heat production and the autocorrelation function of entropy change. Using the theorem, we show the validity of the second law. We estimate excess heat production of a system with long‐time correlations. We derive fractional power scaling of excess heat production with respect to the period of an external transformation. There is a simple relation between the scaling power and the power α of 1/fα noise. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2004
Probability from chaos
Authors: Antoniou I. , Christidis Th. , Gustafson K.
Published: March 2004

Chaos is argued to lie at the origin of probability in nature. This is supported by several results: natural probabilistic processes are components of Markov processes; and Markov processes arise as projections of chaotic dynamics. We also discuss the quantum analogue of the latter. No quantum analogue of the former has yet been found. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2004
Spontaneous generation and propagation of chiral asymmetry
Authors: Kondepudi Dilip K.
Published: March 2004

Significant enantiomeric excesses and chiral symmetry breaking can be generated by chirally autocatalytic systems. Although several theoretical models were proposed some time ago, chirally autocatalytic systems have been hard to find. During the 1990's, however, several chirally autocatalytic systems have been identified. A survey of these systems points to the general fact that chiral selectivity near a chiral surface could be substantial. In our effort to identify the mechanisms that could have produced the amino acid enantiomeric excess observed in meteorites, such processes should be taken into account. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2004
Stochastic models for circadian oscillations: Emergence of a biological rhythm
Authors: Gonze Didier , Halloy José , Goldbeter Albert
Published: March 2004

Nearly all living organisms display circadian oscillations characterized by a period close to 24 h. These rhythms originate from the negative autoregulation of gene expression. Deterministic models based on such genetic regulatory processes account for the occurrence of circadian rhythms in constant environmental conditions (e.g., constant darkness), for entrainment of these rhythms by light–dark cycles, and for their phase‐shifting by light pulses. When the numbers of protein and mRNA molecules involved in the oscillations are small, as may occur in cellular conditions, it becomes necessary to resort to stochastic simulations to assess the influence of molecular noise on circadian oscillations. We address the effect of molecular noise by considering the stochastic version of a core deterministic model previously proposed for circadian oscillations of the PER protein and its mRNA in Drosophila. The model is based on cooperative repression of the per gene by the PER protein. Numerical simulations of the stochastic version of the model are performed by means of the Gillespie method. The predictions of the stochastic approach compare well with those of the deterministic model with respect to both sustained oscillations of the limit cycle type and the influence of the proximity from a bifurcation point below which the system evolves to a stable steady state. Stochastic simulations indicate that robust circadian oscillations can emerge at the cellular level, even when the maximum numbers of mRNA and protein molecules involved in the oscillations are of the order of only a few tens or hundreds. The stochastic simulations also reproduce the evolution toward a strange attractor in conditions where an extended version of the deterministic model admits chaotic behavior. These results show how regulatory feedback processes at the cellular level allow the emergence of a coherent biological rhythm out of molecular noise. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2004
Reaction–diffusion approach to nanostructure formation and texture evolution in adsorbed monoatomic layers
Authors: Walgraef Daniel
Published: March 2004

It is shown that coverage evolution, during atomic deposition on a substrate, may be described, on mesoscopic scales, by dynamical models of the reaction–diffusion type. The models combine reaction terms representing adsorption–desorption processes and nonlinear diffusion terms of the Cahn–Hilliard type. The combination may lead, below a critical temperature, to the instability of uniform deposited layers. The instability induces to the formation of nanostructures that correspond to regular spatial variations of atomic coverage. Such models also may describe texture evolution during the deposition of polycrystalline films. In this case, grains with different orientations with respect to the substrate may coexist. Grains with lower surface energy usually dominate, except at high temperatures, where grains with faster lateral diffusion may override energetically favored ones. Furthermore, at sufficiently low temperatures, uniform grain distributions may become unstable versus regular spatial variations of grain orientations. The relevance of this approach to the deposition of Al or Cu on TiN or Ta substrates is discussed. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2004
Vegetation spots and stripes: Dissipative structures in arid landscapes
Authors: Lejeune Olivier , Tlidi Mustapha , Lefever René
Published: March 2004

The large‐scale vegetation patterns observed in many arid regions are due to the existence of facilitative and competitive interactions that affect the communal development of plants. For the patterns to form, it is necessary that competitive interactions be of longer range than facilitative interactions. Aridity affects the pattern's symmetry properties. As it increases, one first finds patterns constituted of spots of sparser vegetation, which then transform into an alternation of stripes of sparser and thicker vegetation, and finally into a pattern of vegetation spots separated by bare ground. The model and nonlinear analysis presented below explains the observations. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2004
Solitons as dissipative structures
Authors: Velarde Manuel G.
Published: March 2004

I review here recent results regarding the excitation of nonlinear interfacial oscillations, and hence waves, at the surface of a liquid or at the interface separating two liquids when a thermal gradient is imposed or there is adsorption, and subsequent absorption in the bulk, of a (light) surfactant, hence creating tangential stresses due to the surface tension gradient (Marangoni effect). I also recall their solitonic features upon collisions and boundary reflections, etc., even though the proposed evolution equations are not hyperbolic but a parabolic–hyperbolic combination like a dissipation‐modified Boussinesq–Korteweg–de Vries equation. Theory, numerics, and experiments support my claim that solitons can exist and survive in a dissipative medium provided, for example, past an instability threshold, there is an appropriate input–output energy balance. This is very much like (steady) dissipative structures and, indeed, (nonlinear) waves traveling with constant velocity in the moving frame are steady dissipative structures. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2004
Performance improvements of large‐scale video servers by video segment allocation
Authors: Tanaka Kiyoshi , Sakamoto Hideki , Suzuki Hideharu , Nishimura Katzutoshi
Published: March 2004

As large‐scale commercial video‐on‐demand services develop, the creation of large‐scale video servers that can provide video to over 10,000 terminals is needed. A large‐scale video server distributes and stores video in segments using striping technology on many hard disks. Segment duplication is an effective way to improve the performance of video servers, but unless the allocation of segments to several hard disks is appropriate, retrieval requests become concentrated on a particular hard disk, and retrieval delays result. Thus, in this paper the authors describe a method to find a segment allocation that improves video server performance, including the number of retrieval streams and response time, and without creating retrieval delays, by taking into consideration the allocation to hard disk of video segments stored in a video server. In the authors' method, segments to be duplicated are determined and an allocation found by solving a limited satisfaction problem using the access probability for segments. Based on simulation experiments, the authors confirmed that their method was able to create a segment allocation which allowed for better retrieval performance than allocation methods used in the past. © 2004 Wiley Periodicals, Inc. Syst Comp Jpn, 35(4): 27–35, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/scj.10187
Server‐allocation policy for improving response to web‐access peaks
Authors: Yoshimura Yutaka , Tarui Toshiaki , Shonai Toru , Kawabe Shun , Sugie Mamoru
Published: March 2004

A prototype VPDC (Virtual Private Data Center)—a data‐center system for automated server‐allocation control aimed at response time improvement during access peaks—was developed. The causes of degradation in web‐system performance were determined by measurements on this prototype. It was shown that the CPU‐utilization ratio dominates the response time in the case of dynamic‐content sites, while the data‐transfer rate through networks dominates it in the case of static content sites. Behavior analysis of the prototype showed that the web‐response time during access peaks can be improved by an automated server‐allocation control algorithm with a CPU utilization of 50% and a network data‐transfer rate of 30 Mbps as thresholds. © 2004 Wiley Periodicals, Inc. Syst Comp Jpn, 35(5): 55–66, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/scj.10444
Automatic segmentation of liver region based on extracted blood vessels
Authors: Saitoh Takeshi , Tamura Yuta , Kaneko Toyohisa
Published: March 2004

With the rapid progress of CT (Computed Tomography) scanners, four‐phase CT images with resolutions as high as 1 mm have started to be used for diagnosing liver diseases. The first‐, second‐, third‐, and fourth‐phase CT images correspond to before dye injection, the early stage, the full stage, and the wash‐out stage of the injected dye. Such CT data offer useful information for diagnosing hepatic cancer. This paper describes an automatic method for segmenting the liver region using the blood vessel stream in the first‐ and third‐phase CTs by tracing the portal vein and then the hepatic vein. First, the tracing of the veins is carried out by performing a 3D labeling operation in the region extracted with a threshold that separates blood vessels from liver soft tissue. The adjoining stomach and spleen regions are separated by applying erosion and dilation, which are 3D morphological operations. Then, an operation for determining the accurate liver region is carried out to derive an approximate liver region, by enlarging the liver blood vessel region by morphological dilation and then extracting the liver region with an optimal threshold. This method was applied to eight CT data. The resulting regions agree well with the manually detected regions. © 2004 Wiley Periodicals, Inc. Syst Comp Jpn, 35(5): 1–10, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/scj.10592
Alias analysis method for object‐oriented programs using alias flow graphs
Authors: Ohata Fumiaki , Kondou Kazuhiro , Inoue Katsuro
Published: March 2004

When a pair of expressions (or partial expressions) on a program text point to the same object (memory area), these expressions are said to be in an alias relation. These occur by indirect references etc. via a parameter passing with delivery, reference variable, pointer, etc. The existing alias analysis methods are insufficient in terms of reusability of analysis results, not allowing the reusability of object‐oriented programs in the alias analyses. Furthermore, although various proposals of alias analysis methods have been published in the past, practical tools have not yet been available. This study proposes an alias analysis method for object‐oriented programs that considers moduling and reutilization of alias analysis results. The Java alias analysis tool that realizes the proposed method can analyze a large‐scale program such as a class library attached to the JDK (Java Developer's Kit) in a practical time. © 2004 Wiley Periodicals, Inc. Syst Comp Jpn, 35(4): 49–59, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/scj.1231
View space representation and viewpoint planning computation for automatic 3D object modeling
Authors: Morooka Ken'ichi , Zha Hongbin , Hasegawa Tsutomu
Published: March 2004

Viewpoint planning plays an important role in automatic 3D model generation. We have proposed an optimal viewpoint planning [9] for the purpose of model generation by merging images acquired from multiple viewpoints on a sphere that encircles object. This method uses a discretized approximate sphere which involves problems of sphere tessellation and of sphere representation. One must consider that the scanned surface of an object is projected onto a sphere, and that the computational cost increases directly with the number of images. However, there are no appropriate sphere representation methods available. This paper proposes a new representation method based on a 2D array, and develops a new viewpoint planning algorithm. The proposed system is verified by algorithmic analysis and experiments using a real modeling system. © 2004 Wiley Periodicals, Inc. Syst Comp Jpn, 35(4): 60–71, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/scj.1232
Toxicity of ammonia to three marine fish and three marine invertebrates
Authors: Boardman Gregory D. , Starbuck Steven M. , Hudgins Douglas B. , Li Xiayoun , Kuhn David D.
Published: March 2004

Laboratory toxicity tests were performed to obtain more data on the toxicity of ammonia to saltwater organisms. The standards for in‐stream ammonia limits in marine environments presently are based on toxicity tests involving both freshwater and saltwater organisms. Acute tests (48 and 96 h) were performed at 20°C, and chronic tests (7 days) were performed at 25°C. Synthetic seawater and natural seawater from the Chesapeake Bay were used and compared. Included among the organisms tested were sheepshead minnow (14 days old), summer flounder (2 months old), Atlantic silverside (14 days old), mysid shrimp (less than 2 days old), ghost shrimp (10 days old), and quahog clam (9 months old). Based on these results, it seems the chronic criterion for ammonia in marine environments could be increased from 0.035 to 0.081 mg/L un‐ionized ammonia, which would, of course, increase the chronic limit for total ammonia under typical saltwater conditions by a factor of 2.31. No difference was observed in the toxicity of ammonia in natural water compared to synthetic water for both the summer flounder and Atlantic silverside. Furthermore, the Atlantic silverside became more sensitive to ammonia as the salinity was increased from 14 to 22 ppt, but exhibited no change in toxicity response from 22 to 30 ppt. © 2004 Wiley Periodicals, Inc. Environ Toxicol 19: 134–142, 2004
TCP performance over mobile ad hoc networks: a quantitative study
Authors: Anantharaman Vaidyanathan , Park Seung‐Jong , Sundaresan Karthikeyan , Sivakumar Raghupathy
Published: March 2004

In this paper, we study the performance of the transmission control protocol (TCP) over mobile ad‐hoc networks. We present a comprehensive set of simulation results and identify the key factors that impact TCP's performance over ad‐hoc networks. We use a variety of parameters including link failure detection latency, route computation latency, packet level route unavailability index, and flow level route unavailability index to capture the impact of mobility. We relate the impact of mobility on the different parameters to TCP's performance by studying the throughput, loss‐rate and retransmission timeout values at the TCP layer. We conclude from our results that existing approaches to improve TCP performance over mobile ad‐hoc networks have identified and hence focused only on a subset of the affecting factors. In the process, we identify a comprehensive set of factors influencing TCP performance. Finally, using the insights gained through the performance evaluations, we propose a framework calledAtraconsisting of three simple and easily implementable mechanisms at the MAC and routing layers to improve TCP's performance over ad‐hoc networks. We demonstrate thatAtraimproves on the throughput performance of a default protocol stack by 50%–100%. Copyright © 2004 John Wiley & Sons, Ltd.
Compositional Action System Refinement
Authors: Back R. J. R. , Wright J. von
Published: March 2004

We show how a parallel composition of action systems can be refined by refining the components separately, and checking non-interference against invariants and guarantee conditions, which are abstract and stable. The guarantee condition can be thought of as a very abstract specification of how a system affects the global state, and it allows us to show that an action system refinement is valid in a given environment, even if we do not know any of the details of that environment. The paper extends the traditional notion of action systems slightly, and it makes use of a generalisation of the attribute model for program variables.
Relational Concurrent Refinement
Authors: Derrick John , Boiten Eerke
Published: March 2004

Refinement in a concurrent context, as typified by a process algebra, takes a number of different forms depending on what is considered observable. Observations record, for example, which events a system is prepared to accept or refuse. Concurrent refinement relations include trace refinement, failures–divergences refinement, readiness refinement and bisimulation. Refinement in a state-based language such as Z, on the other hand, is defined using a relational model in terms of the input–output behaviour of abstract programs. These refinements are normally verified by using two simulation rules which help make the verification tractable. This paper unifies these two standpoints by generalising the standard relational model to include additional observable aspects. These are chosen in such a way that they represent exactly the notions of observation embedded in the various concurrent refinement relations. As a consequence, simulation rules for the tractable verification of concurrent refinement can be derived. We develop such simulation rules for failures–divergences refinement and readiness refinement in particular, using an alternative relational model in the latter case.
The Variety of Variables in Automated Real-Time Refinement
Authors: Wildman Luke , Fidge Colin , Carrington David
Published: March 2004

The refinement calculus is a well-established theory for deriving program code from specifications. Recent research has extended the theory to handle timing requirements, as well as functional ones, and we have developed an interactive programming tool based on these extensions. Through a number of case studies completed using the tool, this paper explains how the tool helps the programmer by supporting the many forms of variables needed in the theory. These include simple state variables as in the untimed calculus, trace variables that model the evolution of properties over time, auxiliary variables that exist only to support formal reasoning, subroutine parameters, and variables shared between parallel processes.
Exploring Tabular Verification and Refinement
Authors: Sekerinski Emil
Published: March 2004

Tabular representations have been proposed for structuring complex mathematical expressions as they appear in the specification of programs. We argue that tables not only help in writing and checking complex expressions, but also in their formal manipulation. More specifically, we explore the use of tabular predicates and tabular relations in program verification and refinement.
Lateral Pancreaticojejunostomy for Chronic Pancreatitis
Authors: O’Neil Stephen J. , Aranha Gerard V.
Published: March 2004

Chronic pancreatitis is a progressive fibrosis of the pancreas that leads to loss of endocrine and exocrine function. The most common symptom in this disease is intractable pain. The etiology of pain in chronic pancreatitis is not clearly understood. However, many of these patients have dilated ducts consisting of saccular dilations and intervening constructions referred to as the “chain of lakes” phenomenon. These patients can be diagnosed with either endoscopic retrograde cholangiopancreatography (ERCP) or computed tomography (CT). These patients are best treated by the Partington Rochelle modification of the Puestow Procedure otherwise known as lateral pancreaticojejunostomy. Overall pain relief in published studies occurs in 50‐90% of patients. Another proposed advantage of the lateral pancreaticojejunostomy is preservation of endocrine and exocrine pancreatic function as long as the pancreas is not further damaged by alcohol.
Management of Biliary and Duodenal Complications of Chronic Pancreatitis
Authors: Vijungco Joseph D. , Prinz Richard A.
Published: March 2004

Biliary stricture and duodenal obstruction have been increasingly recognized as complications of chronic pancreatitis. The anatomical relationship of the distal common bile duct and the duodenum with the head of the pancreas is the main factor for their involvement in chronic pancreatitis. In hospitalized patients with pancreatitis, the incidence of biliary stricture and duodenal obstruction is reported to be about 6% and 1.2%, respectively. For patients requiring an operation for chronic pancreatitis the incidence increases to 35% for biliary stricture and 12% for duodenal obstruction. Fibrosis around the distal common bile duct can cause stenosis with obstruction of bile flow. Clinically, the presentation of these patients ranges from being asymptomatic with elevated alkaline phosphatase or bilirubin, or both, to being septic with cholangitis. Jaundice, cholangitis, hyperbilirubinemia, and persistent elevation of serum alkaline phosphatase occur more frequently in patients with pancreatitis with a biliary stricture. A twofold elevation of alkaline phosphatase is a marker of possible common duct stenosis in patients with chronic pancreatitis. The incidence of both biliary cirrhosis and cholangitis in these patients is about 10%. ERCP reveals a characteristic long, smoothly tapered stricture of the intrapancreatic common bile duct. In duodenal obstruction, the factors that convert self‐limiting edema to chronic fibrosis and stricture formation are unknown, but ischemia superimposed on inflammation may be the major cause. These patients present with a prolonged history of nausea and vomiting. Barium studies typically show a long constricting lesion of the duodenum, and endoscopy reveals reactive inflammatory changes in a narrowed duodenum. Operation is indicated in patients with common bile duct strictures secondary to chronic pancreatitis when there is evidence of cholangitis, biliary cirrhosis, common duct stones, progression of stricture, elevation of alkaline phophatase and/or bilirubin for over a month, and an inability to rule out cancer. The operation of choice is either choledochoduodenostomy or choledochojejunostomy. A cholecystoenterostomy is less favored because of its higher failure rate (23%). Endoscopic stenting plays a role in patients who are unfit for surgery, but it is not recommended as definitive therapy. For duodenal obstruction, failure to resolve the obstruction with 1–2 weeks of conservative therapy is an indication for bypass. The operation of choice is a gastrojejunostomy. Not uncommonly, combined obstruction of the pancreatic duct, common bile duct, and duodenum will develop. Combined drainage procedures or resection are used to manage these problems.
Heterotopic Pancreatic Tissue Presenting as a Solid and Cystic Lung Lesion: A Very Unusual Bronchopulmonary Foregut Malformation
Authors: De Krijger Ronald R. , Albers Marcel J.I.J. , Bogers Ad J.J.C. , Mooi Wolter J.
Published: March 2004

We describe the history and lung pathology of a premature female infant, who presented with respiratory distress immediately after birth. A thoracic computerized tomography scan showed abnormalities suggestive of congenital cystic adenomatoid malformation of the left lung. In addition, echocardiography revealed a tetralogy of Fallot. A left thoracotomy was performed and the lower lobe of the left lung was removed. Despite intensive supportive therapy, pulmonary hypoperfusion resulted in severe hypoxemia and death. Gross and microscopic analysis of the resected lobe revealed a partly cystic and solid lesion with multiple bronchus-derived cysts and an exuberant multifocal proliferation of glandular tissue, resembling bronchial glands, mixed with heterotopic cartilage surrounding ducts. Immunohistochemical analysis showed the presence of chromogranin A-reactive islet-like structures amidst exocrine tissue showing trypsin and chymotrypsin immunoreactivity, establishing the diagnosis of pulmonary pancreatic heterotopy. In the remaining pulmonary parenchyma, there were secondary changes consistent with partial obstruction and lymphangiectasis which was attributed to the presence of the cardiac malformation. To our knowledge, this is only the fourth reported case of heterotopic pancreatic tissue in the lung, and the first case where this bronchopulmonary foregut anomaly is not associated with a enteric duplication.
Subglottic Ductal Cysts Associated with Complete Tracheal Ring Deformity: Coexistence of Two Rare Airway Abnormalities with Fatal Outcome
Authors: Bokhari Aqiba , Heller Debra S. , Fonseca Carlos , Mirani Neena
Published: March 2004

Subglottic cysts are rare and may cause airway obstruction. Most cases are acquired secondary to endotracheal intubation, even short-term, particularly in the premature neonate. Complete tracheal rings are rare anomalies associated with tracheal stenosis. To our knowledge, the two have not been reported coexisting. A 16-month-old ex-premature boy was found unresponsive, with his tracheostomy tube dislodged. Tracheomalacia, subglottic stenosis, and a laryngeal cyst had been diagnosed shortly after birth, and the cyst was surgically treated at that time. At autopsy, a complete tracheal ring was noted in the subglottic region, above the tracheostomy site, and the tracheal diameter was markedly decreased in this area. In addition, multiloculated cysts were present at that level, arising from both anterolateral tracheal walls. These completely occluded the airway. To our knowledge, this is the first case of a combination of tracheal ring anomaly and subglottic cysts. Pediatric pathologists must be aware of iatrogenic lesions associated with care of the premature neonate, particularly as the age of viability continues to decrease.
Congenital Fibrosarcoma with Metastasis in a Fetus
Authors: Nonaka Daisuke , Sun Chen-Chih J.
Published: March 2004

It is well known that congenital or infantile fibrosarcoma has a much less aggressive behavior than fibrosarcoma in adults, and it rarely metastasizes. We report a case of congenital fibrosarcoma in a 26-wk-old fetus, the diagnosis of which was made by an in utero needle core biopsy. Metastatic tumors were identified at autopsy when the pregnancy was terminated 3 wk later. English literature of metastatic congenital fibrosarcoma was also reviewed.
Reflux Esophagitis: Sequelae and Differential Diagnosis in Infants and Children Including Eosinophilic Esophagitis
Authors: Dahms Beverly Barrett
Published: March 2004

Gastroesophageal reflux disease (GERD) is a common condition in infants and children and has many clinical mimics. Most pediatric pathology departments process many mucosal biopsies from the proximal gastrointestinal tract to evaluate the presence or absence of reflux esophagitis. Since this subject was last reviewed in the 1997 edition of Perspectives in Pediatric Pathology devoted to gastrointestinal diseases in children (Dahms BB. Reflux esophagitis and sequelae in infants and children. In: Dahms BB, Qualman SJ, eds. Gastrointestinal Disease. Perspectives in Pediatric Pathology, vol. 20. Basel: Karger, 1997;14–34), progress in the field has allowed recognition of additional presenting symptoms and treatments of GERD. Histologic criteria for diagnosing reflux esophagitis have not changed. However, the entity of eosinophilic esophagitis has emerged since 1997 and has been defined well enough to allow it to be distinguished from reflux esophagitis, with which it was probably previously confused. Refinements (though not simplification!) in the definition of Barrett esophagus are still in evolution. This review will summarize these newer concepts and briefly review the standards of diagnosis of reflux esophagitis.