bluuebunny/crossref_metadata_2025 huggingface dataset:
Benzophenone-Sensitized Peroxidation in Compressed Lipid Monolayers at Air-Water Interface
Authors: Markovic Dejan Z.
Published: July 2002

The paper reports on a study of radical-type lipid peroxidation of biomembrane lipid constituents in compressed monolayers, with incorporated lipoidic benzophenone photosensitizers. Their triplets abstract allylic and double-allylic hydrogen atoms from hydrophobic moieties of the lipid molecules. The results confirmed the H abstraction occurrence (and thus the initiation of the peroxidizing chain mechanism), and absence of lipid peroxide formation at the same time. The reason is in the "cage effect": highly restricted spatial area of compressed lipid monolayers limits mobility of the formed radicals (lipid and ketyl radicals) and leads to their recombination, preventing the propagation step of the chain mechanism. With certain approximation, one may conclude that these results have clear implication for real biomembranes: their structure is one of the main factors in prevention of spreading of the chain reaction, and lipid peroxide formation.
Distribution and determinants of trihalomethane concentrations in indoor swimming pools
Authors: Chu H , Nieuwenhuijsen M J
Published: July 2002

Objectives: For many decades chlorination has been used as a major disinfectant process for public drinking and swimming pool water in many countries. However, there has been rising concern over the possible link between disinfectant byproducts (DBPs) and adverse reproductive outcomes. The purpose of this study was to estimate the concentrations of trihalomethanes (THMs) in some indoor swimming pools in London and their variation within and between pools and any correlation with other factors.

Methods: Water samples were collected from eight different indoor swimming pools in London. A total of 44 pool samples were collected and analysed for total organic content (TOC) and THMs. Water and air temperature were measured along with the pH during the collection of pool samples. The level of turbulence and the number of people in the pool at the time were also assessed.

Results: The geometric mean concentration for all swimming pools of TOC was 5.8 mg/l, of total THMs (TTHMs) 132.4 μg/l, and for chloroform 113.3 μg/l. There was a clear positive linear correlation between the number of people in the swimming pool and concentrations of TTHMs and chloroform (r=0.7, p<0.01), and a good correlation between concentrations of TOC and TTHMs (r=0.5, p<0.05) and water temperature and concentrations of TTHMs (r=0.5, p<0.01). There was a larger variation in THMs within pools than between pools.

Conclusion: Relatively high concentrations of THMs were found in London's indoor swimming pools. The levels correlated with the number of people in the pool, water temperature, and TOC. The variation in concentrations of THMs was greater within pools than between pools.
Hepatocellular adenomatosis associated with hereditary haemochromatosis
Authors: Radhi J M , Loewy J
Published: July 2002

A young healthy man presented with abdominal pain following an accidental fall. Imaging studies and laparoscopy revealed multiple yellowish well-defined hepatic lesions. Liver biopsies showed hepatic adenomas and iron overload. Laboratory investigation confirmed a diagnosis of hereditary haemochromatosis. To our knowledge this represents the first report of an association of hepatic adenomatosis and primary haemochromatosis.
Antiplatelet use in interventional cardiology
Authors: Brodison Adrian , Katira Ravish , More Ranjit S , Chauhan Anoop
Published: July 2002

Thrombosis within the target vessel is one of the most feared complications associated with coronary intervention, as it is often associated with severe adverse clinical sequelae. This thrombosis is mediated via the activation and aggregation of platelets and therefore considerable effort has been directed at ways of inhibiting platelet function. It is now mandatory to consider the use of two and often three different antiplatelet agents, particularly when intracoronary stents are inserted. Using these regimes, many of the adverse clinical outcomes associated with platelet activation can be reduced.
PstI repeat: a family of short interspersed nucleotide element (SINE)-like sequences in the genomes of cattle, goat, and buffalo
Authors: Sheikh Faruk G , Mukhopadhyay Sudit S , Gupta Prabhakar
Published: July 2002

The PstI family of elements are short, highly repetitive DNA sequences interspersed throughout the genome of the Bovidae. We have cloned and sequenced some members of the PstI family from cattle, goat, and buffalo. These elements are approximately 500 bp, have a copy number of 2 × 105  4 × 105, and comprise about 4% of the haploid genome. Studies of nucleotide sequence homology indicate that the buffalo and goat PstI repeats (type II) are similar types of short interspersed nucleotide element (SINE) sequences, but the cattle PstI repeat (type I) is considerably more divergent. Additionally, the goat PstI sequence showed significant sequence homology with bovine serine tRNA, and is therefore likely derived from serine tRNA. Interestingly, Southern hybridization suggests that both types of SINEs (I and II) are present in all the species of Bovidae. Dendrogram analysis indicates that cattle PstI SINE is similar to bovine Alu-like SINEs. Goat and buffalo SINEs formed a separate cluster, suggesting that these two types of SINEs evolved separately in the genome of the Bovidae.Key words: repeat, SINE, Bovidae, genome.
VECTOR ALGORITHMS FOR APPROXIMATE STRING MATCHING
Authors: BERGERON ANNE , HAMEL SYLVIE
Published: July 2002

Vector algorithms allow the computation of an output vector r = r1 r2 ⋯ rm given an input vector e = e1 e2 ⋯ em in a bounded number of operations, independent of m the length of the vectors. The allowable operations are usually restricted to bit-wise operations available in processors, including shifts and binary addition with carry. These restrictions imple that the existence of a vector algorithm for a particular problem opens the way to extremely fast implementations, using the inherent parallelism of bit-wise operations.

This paper presents general results on the existence and construction of vertor algorithms, with a particular focus on problems arising from computational biology. We show that efficient vector algorithms exist for the problem of approximate string matching with arbitrary weighted distances, generalizing a previous result by G. Myers. We also characterize a class of automata for which vector algorithms can be automatically derived from the transition table of the automata.
A NOTE ON SYNCHRONIZED AUTOMATA AND ROAD COLORING PROBLEM
Authors: CULIK KAREL , KARHUMÄKI JUHANI , KARI JARKKO
Published: July 2002

We consider the problem of labeling a directed multigraph so that it becomes a synchronized finite automaton, as an ultimate goal to solve the famous Road Coloring Conjecture, cf. [1,2]. We introduce a relabeling method which can be used for a large class of automata to improve their 'degree of synchronization'. This allows, for example, to formulate the conjecture in several equivalent ways.
The Radioprotective Effects of Bu-Zhong-Yi-Qi-Tang: A Prescription of Traditional Chinese Medicine
Authors: Kim Sung-Ho , Lee Song-Eun , Oh Heon , Kim Se-Ra , Yee Sung-Tae , Yu Young-Beob , Byun Myung-Woo , Jo Sung-Kee
Published: July 2002

We evaluated the effect of Bu-Zhong-Yi-Qi-Tang, a prescription of traditional Oriental medicine, and its major ingredients on protection of the intestine and hematopoietic organs against radiation damage in this study. The jejunal crypt survival, endogenous spleen colony formation, and apoptosis in jejunal crypt cells were investigated in mice irradiated with high and low doses of γ-rays. Bu-Zhong-Yi-Qi-Tang administration before irradiation protected the jejunal crypts (p < 0.0001), increased the formation of the endogenous spleen colony (p < 0.05) and reduced the frequency of radiation-induced apoptosis (p < 0.05). In experiments on the effects of the individual ingredient of Bu-Zhong-Yi-Qi-Tang, Rensan (Radix Ginseng), Danggui (Radix Angelicae gigantis), Shengma (Rhizoma Cimicifugae) and Chaihu (Radix Bupleuri) might have major radioprotective effects, and each might have different degrees of effect on these three endpoints. These results indicated that Bu-Zhong-Yi-Qi-Tang might be a better agent than any one of its ingredients to satisfy all three endpoints. Although the mechanisms of this inhibitory effect remain to be elucidated, these results indicated that Bu-Zhong-Yi-Qi-Tang might be a useful radioprotector, especially since it is a relatively non-toxic natural product. Further studies are needed to better characterize the protective nature of Bu-Zhong-Yi-Qi-Tang extract and its ingredients.
THE IMPACT OF THE FINANCIAL CRISIS ON THE PRODUCTIVITY OF THAILAND'S FINANCIAL INSTITUTIONS
Authors: ALAM ILA M. SEMENICK , LEIGHTNER JONATHAN E.
Published: July 2002

Using a new dataset of Thai financial institutions, this paper analyzes the dynamics of productivity over the past decade (1989–1998), including the impact of the financial crisis of recent history. We find productivity increased substantially in the wake of Thailand's financial liberalization (1992–1996); this was followed by a precipitous fall during the crisis (1996–1997). To test the robustness several specifications are undertaken: four models (differing with respect to whether or not risk and deposits are included as inputs), and two frontiers (one where banks and finance companies are treated separately, the other where the data are pooled) are analyzed.
STRING THEORY AS A UNIVERSAL LANGUAGE
Authors: POLYAKOV A. M.
Published: July 2002

This article, based on the Klein lecture, contains some new results and new speculations on various topics. They include discussion of open strings in the AdS space, unusual features of D-branes, conformal gauge theories in higher dimensions. We also comment on the infrared screening of the cosmological constant and on the ''brane worlds.''
HOW TO GET LESS HELIUM AND MORE NEUTRINOS FROM BBN
Authors: Chen Xuelei
Published: July 2002

We discuss BBN in the presence of a non-minimally coupled quintessence model. In some of these models, the gravitational constant and cosmic expansion rate are smaller than standard model predicts. The Helium abundance is then smaller, possibly resolve the marginal disagreement between theory and observation. Furthermore, the constraint on neutrino species may also be relaxed.
TESTING PERTURBATIVE RESULTS WITH NON-PERTURBATIVE METHODS FOR THE HIERARCHICAL MODEL
Authors: MEURICE Y. , OKTAY M. B.
Published: July 2002

We present non-perturbative methods to calculate accurately the renormalized quantities for Dyson's Hierarchical Model. We apply this method and calculate the critical exponent γ with 12 and 4 significant digits in the high and low temperature phases, respectively. We report accurate values for universal ratios of amplitudes and preliminary results concerning the comparison with perturbative results.
SUPERCONDUCTIVITY AND PHASE SEPARATION OF La2CuO4+δ SINGLE CRYSTALS
Authors: CHEN C. , WONDRE F. R. , RYAN J. F.
Published: July 2002

Lanthanum cuprate ( La 2 CuO 4) is an antiferromagnetic insulator, which becomes superconducting after introducing interstitial oxygen by high-pressure, chemical or electrochemical oxidation. We report here the flux growth of superconducting single crystal in an ambient atmosphere, which the morphology is remarkably different from that of insulating crystal. The behavior of superconductivity is studied by AC-susceptibility measurement. A phase separation makes a strong effect on the superconductivity. The phase separation mainly occurs at the temperature range of 270 to 190 K and the separation is reversible in the solid state. Superconducting transition temperature (Tc) depends on the temperature, the time and the cooling process. Tc reaches an equilibrium value after several hour treatment at constant temperature, which indicates the completion of the phase separation. It increases to a higher value level only by 30 minute cooling from 260 to 230 K, which suggests the stripe nucleation and growth. A mechanism of the stripe formation is discussed based on the staging phase diagram of La 2 CuO 4+δ. Parallel intergrowth of the oxygen-rich phase and the oxygen-poor phase takes place alternatively in the miscibility gap, in result of self-assembling a composite structure in the duplex single crystal.
GENERALIZED INTELLIGENT STATES FOR NONLINEAR OSCILLATORS
Authors: KINANI A. H. EL , DAOUD M.
Published: July 2002

The construction of Generalized Intelligent States (GIS) for the x4-anharmonic oscillator is presented. These GIS families are required to minimize the Robertson–Schrödinger uncertainty relation. As a particular case, we will get the so-called Gazeau–Klauder coherent states. The properties of the latters are discussed in detail. Analytical representation is also considered and its advantage is shown in obtaining the GIS in an analytical way. Further extensions are finally proposed.
SEMICLASSICAL EXPRESSION OF THE SPIN PROPAGATOR
Authors: Park Kee-Su , Stone Michael , Garg Anupam
Published: July 2002

We use a continuous-time path integral to obtain the semiclassical propagator for minimal-spread spin coherent states. We pay attention to the extra phase. This extra correction of phase is related to an anomaly in the fluctuation determinant. We show that if this extra factor is included, the semiclassical propagator has the correct short time behaviour to O(T2), and demonstrate its consistency under dissection of the path.
Comprehensive study of Fröhlich polaron
Authors: Mishchenko A. S. , Prokof'ev N. V. , Svistunov B. V. , Sakamoto A.
Published: July 2002

A study of the Fröhlich polaron model is performed on the basis of diagrammatic quantum Monte Carlo technique which is enhanced by novel method of spectral analysis of the polaron Green function. We make available for the first time precise data for the effective mass, including the region of intermediate and strong couplings, and analyze the structure of the polaron cloud. A non-trivial structure of the spectral density is observed: at high enough couplings the spectral continuum features pronounced peaks that we attribute to unstable excited states of the polaron.
EVOLUTION FROM BCS SUPERCONDUCTIVITY TO BOSE-EINSTEIN CONDENSATION: MAPPING OF THE FERMIONIC ONTO A BOSONIC SYSTEM IN THE STRONG-COUPLING LIMIT
Authors: PISTOLESI F. , STRINATI G. C.
Published: July 2002

We consider a system of fermions with an effective attractive interaction, for which formation of (real-space) bound pairs is expected to occur in the strong-coupling limit. We provide a direct mapping of this fermionic system onto an effective system of bosons with residual boson-boson interaction by means of functional integrals. We determine in this way the strength and the range of the residual boson-boson interaction.
SHORT-TIME CRITICAL BEHAVIOR OF THE GINZBURG–LANDAU MODEL WITH QUENCHED DISORDER
Authors: LI Z. B. , CHEN Y. , GUO S. H.
Published: July 2002

The theoretic renormalization-group approach is applied to the study of short-time dynamics of the d-dimensional n-component spin systems with long-range interactions r-(d+σ) and quenched disorder which has long-range correlations r-(d-ρ). Asymptotic scaling laws are obtained in a frame of double expansions in ∊=2σ-d and ρ with ρ of the order ∊. The static exponents are obtained exactly to all the order. The initial slip exponents θ′ for the order parameter and θ for the response function, as well as the dynamic exponent z, are calculated upto the first order in ∊. In d=2σ, in contrast to the unique logarithmic decay in the long-time regime which does not depend on σ, ρ, n and the disorder, we find rich scaling structures including logarithmic and exponential-logarithmic scalings in the short-time regime. Non-universal critical scalings of Ising systems are also discussed for d=2σ.
FIGURES OF MERIT FOR NIOBIUM THIN FILMS GROWN ON SAPPHIRE SUBSTRATE
Authors: CANIZO-CABRERA ALBERTO , GÓMEZ-BAROJAS E. , TABARES-MUÑOZ C. , VA-GONZÁLEZ R. SIL , GARCÍa-VÁZQUEZ VALENTÍN
Published: July 2002

In the manufacture of optoelectronics devices, including solar cells, a very important parameter is the degree of chemical purity of the materials used during their fabrication process. There are two figures of merit that allow the comparison in quality of devices prepared by sputtering. The first figure of merit, the impurity concentration, directly depends on the sputtering pressure and the effective leak rate of impurities into the sputtering system. The second figure of merit, the fraction of an impurity monolayer that can be formed, depends on the time a clean surface is exposed to impurities in the growth chamber until the next layer is deposited. In this work, a study to correlate tIle sputtering pressure with the first figure of merit for Nb thin films grown on 90° oriented sapphire substrates is presented. These films were deposited by DC magnetron sputtering, using a Nb disk as the target in a high vacuum system with a base pressure of 5×10-8 torr in Ar plasma. Niobium was chosen because its electrical properties allow easy measurement and comparison. The Nb films were grown at room temperature, keeping fixed all growth parameters but the plasma pressure. Morphology, elemental composition, and structure of the films were determined by scanning electron microscopy (SEM), X-ray energy dispersive spectroscopy (EDS), and x-ray powder diffraction, respectively. Resistance versus temperature profiles in the 10-300 K range are presented, where a correlation between the plasma pressure and the electrical properties can be observed as an indication that the impurity concentration directly depends on the sputtering pressure.
AN EXACT SOLUBLE PATH INTEGRAL MODEL FOR STOCHASTIC BELTRAMI FLUXES AND ITS STRING PROPERTIES
Authors: BOTELHO LUIZ C. L.
Published: July 2002

We propose an exactly soluble path integral model for stochastic Beltrami fluxes in three-dimensional space-time with a fixed eddie scale. We show further the appearance of a three-dimensional self-avoiding random surface structure for the spatial vortex loop in our exactly soluble turbulence reduced model.
TUNNELING TIME BETWEEN TWO BIASED QUANTUM WELLS
Authors: ZHAO XIAN-GENG , ZHU MING JUN
Published: July 2002

We study the dynamics of double-well systems under the influence of time-dependent external fields. A tunneling time describing the coherent tunneling between two quantum wells is obtained analytically by the use of perturbation theory. We illustrate two examples to show the advantage of our theory, in which the phenomenon of localization/delocalization can be addressed uniformly by the tunneling time.
RECOGNIZING PARTIALLY OCCLUDED OBJECTS USING MARKOV MODEL
Authors: CHAN CHAU-JIN , CHEN SHU-YUAN
Published: July 2002

A novel method to recognize occluded objects using Markov model is proposed in this paper. In addition to Markov model having a high tolerance to noise, spatial distribution of features can be incorporated into Markov model in a natural and elegant way. Thus, high recognition accuracy can be achieved by the proposed method. More specifically, for each occluded object in the scene image, its translation, rotation and scale parameters can all be determined by our method even when it may have transformation parameters different from others or it may be duplicated in the scene image with transformation parameters different from each other. Moreover, the recognition process can be performed step by step to find out all of the objects in the scene image according to the confidence measure. Finally, the recognition process can be terminated automatically without knowing the number of objects included in the scene image since hypothesis verification and termination test are performed in our method. Actually, the solution of our method is useful for depth-search applications such as inspection of printed circuit board with multiple layers, underwater diving for searching objects, underground drilling for exploring mine, etc. The proposed method has been applied on two types of databases: puzzle and tool. The effectiveness and practicability of the proposed approach have been proven by various experimental results.
NEW CHARACTERISERS OF BIFURCATIONS FROM KINK SOLUTIONS IN A COUPLED SINE CIRCLE MAP LATTICE
Authors: PRADHAN GAURI R. , GUPTE NEELIMA
Published: July 2002

Kink solutions in coupled sine circle map lattices demonstrate interesting bifurcation behavior. These are illustrated by the study of spatial period two kink solutions for this system. Different types of spatiotemporal solutions such as temporally frozen kinks, spatiotemporally synchronized solutions and kink induced temporally intermittent solutions appear in different regions of parameter space for this system and bifurcations are seen from one type of solution to another. The upper boundaries of the regions where the kinks are stable can be picked up by linear stability analysis. However, the eigenvalues of the stability matrix do not cross the unit circle along the lower stability boundaries, although the nature of the solution changes. Thus linear stability analysis is not sufficient to identify these lower boundaries. Hence we have proposed new characterisers which are capable of identifying such boundaries. Our identifiers successfully pick up the lower boundaries missed by linear stability analysis as well as the upper boundaries. Our characterisers could be of utility in other situations as well.
SYMMETRY, GENERIC BIFURCATIONS, AND MODE INTERACTION IN NONLINEAR RAILWAY DYNAMICS
Authors: JENSEN CARSTEN NORDSTRØM , GOLUBITSKY MARTIN , TRUE HANS
Published: July 2002

We investigate Cooperrider's complex bogie, a mathematical model of a railway bogie running on an ideal straight track. The speed of the bogie v is the control parameter. Taking symmetry into account, we find that the generic bifurcations from a symmetric periodic solution of the model are Hopf bifurcations for maps (or Neimark bifurcations), saddle-node bifurcations, and pitchfork bifurcations. The last ones are symmetry-breaking bifurcations. By variation of an additional parameter, bifurcations of higher degeneracy are possible. In particular, we consider mode interactions near a degenerate bifurcation. The bifurcation analysis and path-finding are done numerically.
INVERSE DISPERSION RELATION OF BZ-WAVES IN NONSTATIONARY GELS
Authors: HANKE W.
Published: July 2002

The behavior of wave propagation, as well that of isolated waves as that of self-sustained activity, in excitable media is characterized by the dispersion relation of the system. For the Belousov–Zhabotinsky (BZ)-reaction as by far the best described system, a number of theoretical considerations and experimental investigations do exist. From the theoretical point of view the dispersion relation of the BZ-reaction has two branches, an upper "fast" or stable branch typified by singular solutions and a lower "slow" branch whose solutions are regular, with a connection between the two branches, defining the smallest possible period and the absolute refractory period of the system. Experimental data are usually located on the upper branch giving higher propagation velocity at increasing period. Only one set of results was published in the early 1970s with velocity being an increasing function of frequency. This set of data was stated to be "difficult to believe" in later papers.

We now present here a more detailed study of a BZ-system with a dispersion relation with an increasing velocity at decreasing period, verifying the existence of an "inverse" dispersion relation at least in the nonstationary gels we have used.
HIGH PERFORMANCE SERVICE DISCOVERY IN LARGE-SCALE MULTI-AGENT AND MOBILE-AGENT SYSTEMS
Authors: CAO JUNWEI , KERBYSON DARREN J. , NUDD GRAHAM R.
Published: July 2002

With increasing requirements of distributed software systems, software agents are becoming a mainstream technology for software engineering and data management. Scalability and adaptability are two key challenges that must be addressed. In this work a new model is introduced for building large-scale distributed software systems with high dynamics, using a hierarchy of homogeneous agents that has the capability of service discovery. The performance of the agent system can be improved using different combinations of optimisation strategies. A modelling and simulation environment has been developed to aid the performance evaluation process. Two case studies are given and simulation results are included that show the impact of the agent mobility and the choice of performance optimisation strategies on the overall system performance.
NONRIBBON 2-LINKS ALL OF WHOSE COMPONENTS ARE TRIVIAL KNOTS AND SOME OF WHOSE BAND-SUMS ARE NONRIBBON KNOTS
Authors: OGASA EIJI
Published: July 2002

There is a nonribbon 2-link all of whose components are trivial 2-knots and one of whose band-sums is a nonribbon 2-knot.
LOCOMOTION OF A TWO DIMENSIONAL KERATOCYTE MODEL
Authors: SAMBETH R. , BAUMGAERTNER A.
Published: July 2002

The polymerization-induced propulsion of a model cell consisting of a cell membrane enclosing mobile actin molecules and polymerizing actin filaments is studied using Monte Carlo methods. It is shown that asymmetric polymerization alone induces a rectified motion of the cell. The structural organization of the locomoting cell exhibits an anisotropic shape induced by the anisotropic distribution of actin within the cell. This nonequilibrium distribution is maintained by a constant flow of actin molecules from the rear to the front of the cell. The efficiency of the rectification process, and hence the cell velocity, depends cooperatively on the density of actin molecules. The maximum of the cell velocity is determined by the optimal interplay between the number of filaments and the fluctuation of the cell membrane.
BIOMECHANICAL EVALUATION ON GAIT PATTERN OF PREGNANT SUBJECTS
Authors: ABU OSMAN N. A. , MAT GHAZALI R.
Published: July 2002

Many physiological and anatomical changes occurring during the pregnancy period have been widely documented and reported in the literature. This study involved the participation of pregnant subjects, divided into their respective trimester periods, with post-partum normal subjects. Kinetics analyses were performed on each subject using the Peak Motus 2000 system, and comparison between the pregnant subjects in different trimester, and also the post-partum normal subjects, were conducted. The step width generally increases as the subject is progressing through her pregnancy periods. From the average, the step width increases from 0.168 m in the first trimester to 0.350 m in the third trimester, which is an increase of nearly 50%. It can be generally appreciated that the step width increases as the pregnancy period progresses. It shows that these increases may be attributed to the increase of the body weight of the subject as she gains more weight towards the end of her pregnancy.
Interprocedural static analysis of sequencing constraints
Authors: Olender Kurt M. , Osterweil Leon J.
Published: July 2002

This paper describes a system that automatically performs static interprocedural sequencing analysis from programmable constraint specifications. We describe the algorithms used for interprocedural analysis, relate the problems arising from the analysis of real-world programs, and show how these difficulties were overcome. Finally, we sketch the architecture of our prototype analysis system (called Cesar) and describe our experiences to date with its use, citing performance and error detection characteristics.
On modeling of information retrieval concepts in vector spaces
Authors: Wong S. K.M. , Ziarko W. , Raghavan V. V. , Wong P. C.N.
Published: July 2002

The Vector Space Model (VSM) has been adopted in information retrieval as a means of coping with inexact representation of documents and queries, and the resulting difficulties in determining the relevance of a document relative to a given query. The major problem in employing this approach is that the explicit representation of term vectors is not known a priori. Consequently, earlier researchers made the assumption that the vectors corresponding to terms are pairwise orthogonal. Such an assumption is clearly unrealistic. Although attempts have been made to compensate for this assumption by some separate, corrective steps, such methods are ad hoc and, in most cases, formally inconsistent.

In this paper, a generalization of the VSM, called the GVSM, is advanced. The developments provide a solution not only for the computation of a measure of similarity (correlation) between terms, but also for the incorporation of these similarities into the retrieval process.

The major strength of the GVSM derives from the fact that it is theoretically sound and elegant. Furthermore, experimental evaluation of the model on several test collections indicates that the performance is better than that of the VSM. Experiments have been performed on some variations of the GVSM, and all these results have also been compared to those of the VSM, based on inverse document frequency weighting. These results and some ideas for the efficient implementation of the GVSM are discussed.
Approximating shortest paths on a convex polytope in three dimensions
Authors: Agarwal Pankaj K. , Har-Peled Sariel , Sharir Micha , Varadarajan Kasturi R.
Published: July 2002

Given a convex polytope
P
with
n
faces in ℝ
3
, points ∈ ∂P, and a parameter 0 < ϵ ≤ 1, we present an algorithm that constructs a path on ∂P from
s
to
t
whose length is at most (1 + ϵ)

d
p
(s, t)

, where

d
p
(s, t)

is the length of the shortest path between
s
and
t
on ∂P. The algorithm runs in

O(n log 1/ϵ + 1/ϵ
3
)

time, and is relatively simple. The running time is

O(n + 1/ϵ
3
)

if we only want the approximate shortest path distance and not the path itself. We also present an extension of the algorithm that computes approximate shortest path distances from a given source point on ∂P to all vertices of
P
.
Towards a polynomial-time randomized algorithm for closed product-form networks
Authors: Chen Wu-Lin , O'Cinneide Colm Art
Published: July 2002

We present a Markov chain Monte Carlo method for class throughputs in closed multiclass product-form networks. The method is as follows. For a given network, we construct a “regularized” network with a highly simplified structure that has the same steady-state distribution. We then simulate the regularized network. The method has performed reasonably well across a broad range of problems. We give a heuristic explanation of this and prove that the regularized network “mixes in polynomial time” in some special cases.
Improving the human factors aspect of database interactions
Authors: Shneiderman Ben
Published: July 2002

The widespread dissemination of computer and information systems to nontechnically trained individuals requires a new approach to the design and development of database interfaces. This paper provides the motivational background for controlled psychological experimentation in exploring the person/machine interface. Frameworks for the reductionist approach are given, research methods discussed, research issues presented, and a small experiment is offered as an example of what can be accomplished. This experiment is a comparison of natural and artificial language query facilities. Although subjects posed approximately equal numbers of valid queries with either facility, natural language users made significantly more invalid queries which could not be answered from the database that was described.
A flexible datapath allocation method for architectural synthesis
Authors: Choi Kyumyung , Levitan Steven P.
Published: July 2002

We present a robust datapath allocation method that is flexible enough to handle constraints imposed by a variety of target architectures. Key features of this method are its ability to handle accurate modeling of datapath units and the simultaneous optimization of direct objective functions. The proposed method consists of a new binding model construction scheme and an optimization technique based on simulated annealing. To illustrate the flexibility of this method, two datapath allocation procedures have been developed for two problem enviroments: (1) a procedure that incorporates interconnection area and delay estimates, where floor-planning is tightly integrated into datapath allocation; and (2) a procedure that handles registers, register files, and multiport memories for data storage, as well as random and linear topologies for interconnection architectures. Results from these two applications show our method produces competitive designs for benchmark circuits, as well as being flexible enough to be used for a variety of different domains.
Join and Semijoin Algorithms for a Multiprocessor Database Machine
Authors: Valduriez Patrick , Gardarin Georges
Published: July 2002

This paper presents and analyzes algorithms for computing joins and semijoins of relations in a multiprocessor database machine. First, a model of the multiprocessor architecture is described, incorporating parameters defining I/O, CPU, and message transmission times that permit calculation of the execution times of these algorithms. Then, three join algorithms are presented and compared. It is shown that, for a given configuration, each algorithm has an application domain defined by the characteristics of the operand and result relations. Since a semijoin operator is useful for decreasing I/O and transmission times in a multiprocessor system, we present and compare two equi-semijoin algorithms and one non-equi-semijoin algorithm. The execution times of these algorithms are generally linearly proportional to the size of the operand and result relations, and inversely proportional to the number of processors. We then compare a method which consists of joining two relations to a method whereby one joins their semijoins. Finally, it is shown that the latter method, using semijoins, is generally better. The various algorithms presented are implemented in the SABRE database system; an evaluation model selects the best algorithm for performing a join according to the results presented here. A first version of the SABRE system is currently operational at INRIA.
Flowcharts versus program design languages
Authors: Ramsey H. Rudy , Atwood Michael E. , Van Doren James R.
Published: July 2002

An experiment was performed to assess the relative merits of program design languages (PDLs) and flowcharts as techniques for the development and documentation of detailed designs for computer programs. The use of a PDL by a software designer, for the development and description of a detailed program design, produced better results than did the use of flowcharts. Specifically, the designs appeared to be of significantly better quality, involving more algorithmic or procedural detail, than those produced using flowcharts. In addition, flowchart designs exhibited considerably more abbreviation and other space-saving practices than did PDL designs, with a possible adverse effect on their readability. When equivalent, highly readable designs were presented to subjects in both PDL and flowchart form, no pattern of short-term or long-term differences in comprehension of the design was observed. No significant differences were detected in the quality or other properties of programs written as implementations of the designs. Subjective ratings indicated a mild preference for PDLs. Overall, the results suggest that software design performance and designer-programmer communication might be significantly improved by the adoption of informal PDLs rather than flowcharts as a standard documentation method for detailed computer program designs.
On the security of multiple encryption
Authors: Merkle Ralph C. , Hellman Martin E.
Published: July 2002

Double encryption has been suggested to strengthen the Federal Data Encryption Standard (DES). A recent proposal suggests that using two 56-bit keys but enciphering 3 times (encrypt with a first key, decrypt with a second key, then encrypt with the first key again) increases security over simple double encryption. This paper shows that although either technique significantly improves security over single encryption, the new technique does not significantly increase security over simple double encryption. Cryptanalysis of the 112-bit key requires about 2
56
operations and words of memory, using a chosen plaintext attack. While DES is used as an example, the technique is applicable to any similar cipher.
A sorting problem and its complexity
Authors: Pohl Ira
Published: July 2002

A technique for proving min-max norms of sorting algorithms is given. One new algorithm for finding the minimum and maximum elements of a set with fewest comparisons is proved optimal with this technique.
Three-dimensional computer display
Authors: Ophir D. , Spinrad R. J.
Published: July 2002

A stereographic display terminal has been produced using the raster display (BRAD) recently developed at Brookhaven. The system uses a rotating refresh memory to feed standard television monitors.

To produce a stereographic display the computer calculates the projected video images of an object, viewed from two separated points. The resulting video maps are stored on separate refresh bands of the rotating memory. The two output signals are connected to separate color guns of a color television monitor, thus creating a superimposed image on the screen. Optical separation is achieved by viewing the image through color filters.

The display is interactive and can be viewed by a large group of people at the same time.
PIP
Authors: Rudloe Harry , Deutsch Martin , Marill Thomas
Published: July 2002

Sorting techniques using an IBM 1401 with a random access storage device are evaluated.
A dynamic framework for object projection views
Authors: Vianu Victor
Published: July 2002

User views in a relational database obtained through a single projection ("projection views") are considered in a new framework. Specifically, such views, where each tuple in the view represents an object ("object-projection views"), are studied using the dynamic relational model, which captures the evolution of the database through consecutive updates. Attribute sets that yield object-projection views are characterized using the static and dynamic functional dependencies satisfied by the database. Object-projection views are then described using the static and dynamic functional dependencies “inherited” from the original database. Finally, the impact of dynamic constraints on the view update problem is studied in a limited context. This paper demonstrates that new, useful information about views can be obtained by looking at the evolution of the database as captured by the dynamic relational model.
Using induction to design algorithms
Authors: Manber Udi
Published: July 2002

An analogy between proving mathematical theorems and designing computer algorithms provides an elegant methodology for designing algorithms, explaining their behavior, and understanding their key ideas.
The status of helpdesk support
Authors: Govindarajulu Chittibabu
Published: July 2002

What do end users want? A survey of helpdesk services found they're more likely to turn to informal and online sources of support, including friends and vendors.
Methodology for allocating resources for data quality enhancement
Authors: Ballou Donald P. , Tayi Giri Kumar.
Published: July 2002

The issue of effective use of resources committed to data integrity maintenance is addressed via a heuristic which uses parameter estimates that are iteratively refined to partition available resources among multiple data sets.
Smart game board and go explorer: a study in software and knowledge engineering
Authors: Kierulf Anders , Chen Ken , Nievergelt Jurg
Published: July 2002

Software engineering is an established discipline that has accumulated and codified more than two decades worth of know-how. Knowledge engineering, on the other hand, is an emerging discipline with lots of issues but, at least so far, little structure. Despite its lack of maturity the practice of knowledge engineering promises to have a noticeable impact on software engineering doctrine. The experimental nature of knowledge engineering goes hand-in-hand with a style of software development best characterized as ‘exploratory,’ which has not been much studied in traditional software engineering.
Automatic parsing of degenerate quadric-surface intersections
Authors: Farouki R. T. , Neff C. , O'Conner M. A.
Published: July 2002

In general, two quadric surfaces intersect in a nonsingular quartic space curve. Under special circumstances, however, this intersection may “degenerate” into a quartic with a double point, or a composite of lines, conics, and twisted cubics whose degrees, counted over the complex projective domain, sum to four. Such degenerate forms are important since they occur with surprising frequency in practice and, unlike the generic case, they admit rational parameterizations. Invoking concepts from classical algebraic geometry, we formulate the condition for a degenerate intersection in terms of the vanishing of a polynomial expression in the quadric coefficients. When this is satisfied, we apply a multivariate polynomial factorization algorithm to the projecting cone of the intersection curve. Factors of this cone which correspond to intersection components “at infinity” may be removed a priori. A careful examination of the remaining cone factors then facilitates the identification and parameterization of the various real, affine intersection elements that may arise: isolated points, lines, conics, cubics, and singular quartics. The procedure is essentially automatic (avoiding the tedium of case-by-case analyses), encompasses the full range of quadric forms, and is amenable to implementation in exact (symbolic) arithmetic.
EVOLUTION OF LIGHT-REGULATED PLANT PROMOTERS
Authors: Argüello-Astorga Gerardo , Herrera-Estrella Luis
Published: July 2002

▪ Abstract  In this review, we address the phylogenetic and structural relationships between light-responsive promoter regions from a range of plant genes, that could explain both their common dependence on specific photoreceptor-associated transduction pathways and their functional versatility. The well-known multipartite light-responsive elements (LREs) of flowering plants share sequences very similar to motifs in the promoters of orthologous genes from conifers, ferns, and mosses, whose genes are expressed in absence of light. Therefore, composite LREs have apparently evolved from cis-regulatory units involved in other promoter functions, a notion with significant implications to our understanding of the structural and functional organization of angiosperm LREs.
FIFTY YEARS AS A PLANT PHYSIOLOGIST
Authors: Henderson James HM
Published: July 2002

▪ Abstract  This chapter is a chronological and biographical sketch of the professional life of a botanist-plant physiologist. He just happens to be of African-American descent. He cites his early education and through college and graduate school, as well as his war years at the University of Chicago. His postdoc appointment at Caltech with James Bonner was really his professional beginning and highlight. Most of his teaching and research years were spent at Tuskegee University and the George Washington Carver Research Foundation. He spent several tours of research activity, in both the United States and foreign countries. His contact with plant physiologists was quite broad, both in the United States and overseas. Finally, in his senior years, he has turned to mentoring young students into careers in the biological and allied sciences. This activity, he states, has “kept me young beyond my chronological age.”
Catalysis By Metal-Activated Hydroxide in Zinc and Manganese Metalloenzymes
Authors: Christianson David W. , Cox J. David
Published: July 2002

▪ Abstract  The metal-activated hydroxide ion is a critical nucleophile in metalloenzymes that catalyze hydrolysis or hydration reactions. The most common metal used is zinc; occasionally, other transition metals such as manganese are required. Human carbonic anhydrase II and rat liver arginase serve as well-studied paradigms of zinc and manganese metalloenzymes, respectively. Comparative structure-function relationships between these two metalloenzymes highlight parallels in the chemistry of metal-activated hydroxide: (a) the protein environment of metal-bound hydroxide modulates its reactivity; (b) a hydrogen bond with metal-bound hydroxide holds it in the proper orientation for catalysis; (c) nonmetal substrate-binding sites are implicated in both enzyme mechanisms; and (d) regeneration of metal-bound hydroxide ion from a metal-bound water molecule requires proton transfer to bulk solvent mediated by a histidine proton shuttle residue. Interestingly, the electrostatics of catalysis differ between the two enzymes, in that the first step of catalysis requires formation of a negatively charged transition state in the carbonic anhydrase II mechanism, whereas a neutral transition state is approached in the arginase mechanism. This electrostatic feature may contribute to the differences in the chemistry, the metal binding sites, and the metal specificity between these two enzymes.
LESSONS FROM ZINC-BINDING PEPTIDES
Authors: Berg Jeremy M. , Godwin Hilary Arnold
Published: July 2002

▪ Abstract  Zinc-finger domains are small metal-binding modules that are found in a wide range of gene regulatory proteins. Peptides corresponding to these domains have provided valuable model systems for examining a number of biophysical parameters entirely unrelated to their nucleic acid binding properties. These include the chemical basis for metal-ion affinity and selectivity, thermodynamic properties related to hydrophobic packing and beta-sheet propensities, and constraints on the generation of ligand-binding and potential catalytic sites. These studies have laid the foundation for applications such as the generation of optically detected zinc probes and the design of metal-binding peptides and proteins with desired spectroscopic and chemical properties.
THE EVOLUTION OF AN ENERGY CONTRARIAN
Authors: Linden Henry R.
Published: July 2002

[Figure: see text]

▪ Abstract  An analysis of the forces that have shaped energy and energy-related environmental policies is presented through the eyes of an active participant in their evolution over the past 53 years. The problem of self-interest in taking energy and environmental policy positions is addressed candidly. The “energy crisis” is cited as an example. Its credibility depended on excessive demand projections, coupled with erroneous assessments of US and global hydrocarbon resources and of prospects for making these resources economically recoverable through technology advances. Many energy crisis proponents benefited from the misguided government response and from the large investments in uneconomic synthetic fuel technologies. Today, proponents of catastrophic anthropogenic climate change, again claiming scientific consensus, threaten to create even greater energy market distortions at large social and economic costs. The author traces his conversion to energy contrarian to the general failure of consensus and to his own misjudgments in these critical policy areas.
From Physics to Development Strategies
Authors: Goldemberg José
Published: July 2002

The evolution of my career from purely academic research in experimental nuclear physics to science, followed by involvement in public affairs and administration, is described. Highlights in this trajectory are my involvement with the efforts to improve support for science activities and the protection of human rights of scientists in Brazil during the period of military government (1964–1984). The future role of nuclear energy in Brazil marked my transition toward a growing interest in energy alternatives and renewables. Finally, my activities first as the Rector of the University of São Paulo and then as a cabinet member in the federal government are described, as are the role I played in defusing the nuclear race between Argentina and Brazil and my participation in the Climate Conference in Rio in 1992.