bluuebunny/crossref_metadata_2025 huggingface dataset:
Subchronic Dermal Toxicity and Oral Neurotoxicity of Triethylene Glycol Monomethyl Ether in Cd Rats
Authors: Gill Michael W. , Fowler Edward H. , Gingell Ralph , Lomax Larry G. , Corley Richard A.
Published: October 2002

These studies were conducted to evaluate the potential for repeated subchronic administration of triethylene glycol monomethyl ether (TGME) to produce systemic toxicity in the rat following dermal application, and neurotoxicity in the rat following peroral administration. The route of administration and maximum dose levels for these studies were specified by the U.S. Environmental Protection Agency (EPA) in a testing consent order for TGME. In the subchronic dermal toxicity study, TGME (undiluted) was applied to the clipped backs of CD rats (10 rats/sex/group) for 6 h/day (occluded), 5 days/wk or 13 wk at dose levels of 0, 0.4, 1.2, and 4.0 g/kg/day. Four groups of satellite animals (5 rats/sex/group) employed for interim hematology and clinical chemistry measurements were dosed in the same manner for 31 days. Experimental evaluations included clinical examinations, food consumption, body weight, ophthalmology, estrous cyclicity, hematology, clinical chemistry, urinalysis, and necropsy for all animals and microscopic examination of a complete set of tissues (including bone marrow smears) for animals in the control and high-dose treatment groups. In addition, the testes and epididymides were processed for examination of spermatocyte development. None of the experimental endpoints included in this study to evaluate the potential for systemic toxicity were affected by treatment with TGME. For the neurotoxicity study, TGME was mixed in the drinking water and administered ad libitum to rats
Rat Liver Hyperplasia: Polyamine Concentrations Maintained Despite Ornithine Decarboxylase Inhibition
Authors: Martin F. L. , Maghsoudloo M. , Murphy G. M. , Alison M. R.
Published: October 2002

The polyamines (putrescine, spermidine, spermine) and the key enzyme controlling their synthesis (ornithine decarboxylase, ODC) are considered important for many adaptive growth responses. In most epithelial cell populations enhanced proliferation is preceded by or associated with elevated ODC activity. We investigated whether inhibition of ODC activity reduces hepatic proliferation after mitogenic challenge. Rats maintained on a 2% oral solution of the L-ornithine analogue α-difluoromethylornithine (DFMO) were compared to positive controls in their response to mitogenic challenge. Adaptive growth was induced by partial hepatectomy (PH), or by a single dose of either phenobarbital (PB) (100 mg kg-1, gastric tube), cyproterone acetate (CPA) (100 mg kg-1, ip) or clofibrate (500 mg kg-1, gastric tube). Although these stimuli normally elevate ODC levels, DFMO proved to be a powerful inhibitor. Inhibition of ODC activity correlated with the absence of detectable levels of putrescine; without DFMO, putrescine levels were approximately 200 nmol g-1 wet weight in each case following mitogenic challenge. Proliferation, as measured by 5-bromo-2′-deoxyuridine (BrdUrd) labeling at 24 h following stimulation, was largely unaffected by DFMO, and hepatic levels of spermidine and spermine were not significantly reduced. The hepatic levels of these downstream polyamines were high despite ODC inhibition, indicating an important role for them in these adaptive growth responses. These data suggest that an alternative polyamine metabolism pathway not affected by DFMO might be in operation here, or that an exogenous source of polyamines might exist.
Assay of salsolinol in peripheral blood mononuclear cells of alcoholics and healthy subjects by gas chromatography‐mass spectrometry
Authors: Haber H. , Jahn H. , Ehrenreich H. , Melzig M. F.
Published: October 2002

Endogenous 6,7‐dihydroxy‐1‐methyl‐1,2,3,4‐tetrahydroisoquinoline (salsolinol) could be a potential marker involved in the aetiology of alcoholism.Whereas the amount of salsolinol in plasma and urine depends on several dietary conditions, the salsolinol from peripheral mononuclear cells should be formed endogenously. Salsolinol was quantified in lymphocytes of 10 controls and 11 alcoholics (after 1 and 13 weeks of abstinence) using solid phase extraction and gas chromatography/mass spectrometry. Alcoholics showed significantly lower salsolinol concentration than the controls. After 13 weeks of abstinence a further significant decrease of SAL levels could be seen in the lymphocytes of alcoholics. The findings of this study support the theory that salsolinol might be a trait marker in alcoholism.
Alveolar Soft Part Sarcoma Metastatic to Small Bowel Mucosa Causing Polyposis and Intussuseption
Authors: Sabel Michael S. , Gibbs John F. , Litwin Allan , Mcgrath Brian , Kraybill William B. , Brooks John J.
Published: October 2002

A report of alveolar soft part sarcoma metastatic to the small bowel is presented. Hematogenous metastases to the small
bowel from primary tumors outside the abdominal cavity are uncommon, and most remain asymptomatic and are not discovered
until autopsy. However, small bowel metastases can lead to intestinal obstruction, intussuseption or even perforation.
While metastases to the small bowel have been described for other tumor types, including melanoma and lung cancer, this
is extremely uncommon for sarcoma, especially alveolar soft part sarcoma. We describe a 42‐year‐old male with a long history
of alveolar soft part sarcoma, metastatic to the lung and brain, who developed an intussuseption from metastases to the small
bowel.
The Treatment and Outcome of Patients With Soft Tissue Sarcomas and Synchronous Metastases
Authors: Kane John M. , Finley J. William , Driscoll Deborah , Kraybill William G. , Gibbs John F.
Published: October 2002

Introduction: There is a strong association between poor overall survival and a short disease‐free interval for patients with
soft tissue sarcomas (STS) and metastatic disease. Patients with STS and synchronous metastases should have a very dismal
prognosis.The role of surgery in this subgroup of patients with STS has not been defined.

Patients and Methods: A single‐institution retrospective review was performed of 48 patients with STS and synchronous
metastases in regard to patient demographics, presentation, tumor characteristics, metastatic sites, treatment, follow‐up, and
survival over a 27‐year period.

Results: Most primary tumors were ≥10 cm (58%), high‐grade histology (77%), and located on the extremity (60%).The
most frequent site of metastatic disease was the lung (63%); 27% of patients had metastases to ≥2 organ sites. Surgery to
the primary tumor was performed in 94% of patients (n = 45) and 68% had additional radiation therapy (n = 32). Thirty‐
five percent of patients underwent at least one metastastectomy (n = 17). Chemotherapy was administered to 90% of patients
(n = 43); 31% received ≥3 different regimens (n = 15) and 25% were given intra‐arterial or intracavitary therapy (n = 12).
Median overall survival was 15 months with a 21% 2‐year survival. Local control of the primary tumor was achieved in 54%
(n = 26), and metastastectomy was performed in 35% (n = 17). No analyzed factors were associated with an improvement
in overall survival

Conclusions: Despite multiple poor prognostic factors, the survival of patients with STS and metastases is comparable to
those who develop delayed metastatic disease. However, unlike patients who present with metachronous disease, there was
no improved survival observed for patients treated with metastastectomy. Consequently, treatment for patients with STS
and synchronous metastases should be approached with caution. Surgical management of STS with synchronous metastases
must be considered palliative and should be reserved for patients requiring palliation of symptoms. Patients must also
be well informed of the noncurative nature of the procedure.
De Novo Osteogenic Sarcoma of Mastoid Bone
Authors: Işikdogan Abdurrahman , Büyükçelik Abdullah , Erekul Selim , Pamir Ali
Published: October 2002

The most common primary malignant tumor of the bone is osteosarcoma. Primary involvement of the craniofacial bones in osteosarcoma is relatively rare. The mandible and the maxillae are the most commonly affected bones of the head. Here, we report a rare case of de novo high‐grade osteogenic sarcoma of the mastoid region of the temporal bone and discuss the
diagnostic and therapeutic properties.
Conservation of the Biotin Regulon and the BirA Regulatory Signal in Eubacteria and Archaea
Authors: Rodionov Dmitry A. , Mironov Andrei A. , Gelfand Mikhail S.
Published: October 2002

Biotin is a necessary cofactor of numerous biotin-dependent carboxylases in a variety of microorganisms. The strict control of biotin biosynthesis in Escherichia coli is mediated by the bifunctional BirA protein, which acts both as a biotin–protein ligase and as a transcriptional repressor of the biotin operon. Little is known about regulation of biotin biosynthesis in other bacteria. Using comparative genomics and phylogenetic analysis, we describe the biotin biosynthetic pathway and the BirA regulon in most available bacterial genomes. Existence of an N-terminal DNA-binding domain in BirA strictly correlates with the presence of putative BirA-binding sites upstream of biotin operons. The predicted BirA-binding sites are well conserved among various eubacterial and archaeal genomes. The possible role of the hypothetical genes bioY and yhfS–yhfT, newly identified members of the BirA regulon, in the biotin metabolism is discussed. Based on analysis of co-occurrence of the biotin biosynthetic genes and bioY in complete genomes, we predict involvement of the transmembrane protein BioY in biotin transport. Various nonorthologous substitutes of the bioC-coupled genebioH from E. coli, observed in several genomes, possibly represent the existence of different pathways for pimeloyl-CoA biosynthesis. Another interesting result of analysis of operon structures and BirA sites is that some biotin-dependent carboxylases from Rhodobacter capsulatus, actinomycetes, and archaea are possibly coregulated with BirA. BirA is the first example of a transcriptional regulator with a conserved binding signal in eubacteria and archaea.
Characterization of Aluminum Honeycomb Material Failure in Large Deformation Compression, Shear, and Tearing
Authors: Zhou Qing , Mayer Robert R.
Published: October 2002

Large deformation failures of aluminum honeycomb materials in dynamic compression, static shear and static tearing are characterized in this comprehensive experimental study. Two low density honeycomb materials that make up the Offset Deformable Barrier (ODB) used in vehicle crash test were tested. Material characterization methods, including one for studying material tearing, have been developed. The honeycomb material data under large deformation, including complete curves of compression and shear stress-strain relations in the three principal directions, are presented and analyzed. Honeycomb material tearing strength, defined as tearing force per unit tearing length, is introduced. Strain-rate dependence of honeycomb materials under dynamic loading is investigated. Local failure mechanisms of honeycombs in compression, shear, and indentation punch tests and their relations with the bulk properties of the materials are studied in detail. The results of this research may be used to improve the material fidelity of finite element simulations of the ODB.
Analysis of Energy Balance When Using Cohesive Zone Models to Simulate Fracture Processes
Authors: Shet C. , Chandra N.
Published: October 2002

Cohesive Zone Models (CZMs) are being increasingly used to simulate fracture and fragmentation processes in metallic, polymeric, and ceramic materials and their composites. Instead of an infinitely sharp crack envisaged in fracture mechanics, CZM presupposes the presence of a fracture process zone where the energy is transferred from external work both in the forward and the wake regions of the propagating crack. In this paper, we examine how the external work flows as recoverable elastic strain energy, inelastic strain energy, and cohesive energy, the latter encompassing the work of fracture and other energy consuming mechanisms within the fracture process zone. It is clearly shown that the plastic energy in the material surrounding the crack is not accounted in the cohesive energy. Thus cohesive zone energy encompasses all the inelastic energy e.g., energy required for grainbridging, cavitation, internal sliding, surface energy but excludes any form of inelastic strain energy in the bounding material.
Flexural vibration of perforated plates and porous elastic materials under acoustic loading
Authors: Takahashi D. , Tanaka M.
Published: October 2002

This paper presents a method of theoretical treatment of acoustic coupling due to flexural vibration of perforated plates and plates of porous elastic materials. The analytical model is developed by introducing flow continuity at the plate surface in a spatially mean sense and air–solid interaction within the plate material. To demonstrate the method of application, some fundamental acoustic problems based on a classical thin-plate theory are analyzed and discussed in relation to the interactive effect of flexural vibration and plate permeability. For acoustic radiation from a vibrating plate excited by a harmonic point-force, the attenuation effect of power radiation appears at frequencies below the critical frequency of coincidence. In the problem of sound absorption of a perforated plate or a plate of porous elastic material backed by an air layer, as permeability decreases, the effect of plate vibration increases. For perforated absorber systems including plate vibration effects, the trend of variation from ordinary theory depends on plate thickness.
Contribution of spectral cues to human sound localization
Authors: Langendijk Erno H. A. , Bronkhorst Adelbert W.
Published: October 2002

The contribution of spectral cues to human sound localization was investigated by removing cues in 12-, 1- or 2-octave bands in the frequency range above 4 kHz. Localization responses were given by placing an acoustic pointer at the same apparent position as a virtual target. The pointer was generated by filtering a 100-ms harmonic complex with equalized head-related transfer functions (HRTFs). Listeners controlled the pointer via a hand-held stick that rotated about a fixed point. In the baseline condition, the target, a 200-ms noise burst, was filtered with the same HRTFs as the pointer. In other conditions, the spectral information within a certain frequency band was removed by replacing the directional transfer function within this band with the average transfer of this band. Analysis of the data showed that removing cues in 12-octave bands did not affect localization, whereas for the 2-octave band correct localization was virtually impossible. The results obtained for the 1-octave bands indicate that up–down cues are located mainly in the 6–12-kHz band, and front–back cues in the 8–16-kHz band. The interindividual spread in response patterns suggests that different listeners use different localization cues. The response patterns in the median plane can be predicted using a model based on spectral comparison of directional transfer functions for target and response directions.
BegoStone—a new stone phantom for shock wave lithotripsy research (L)
Authors: Liu Yunbo , Zhong Pei
Published: October 2002

BegoStone, a commercially available super-hard plaster originally developed for dental applications, was examined as a potential stone phantom material for shock wave lithotripsy (SWL) research. The physical properties of BegoStone were characterized by using an ultrasound pulse transmission method and a microhardness tester with a Vickers indenter. In addition, spherical BegoStone phantoms (D=10 mm) were fabricated and exposed to 25–500 shocks at the beam focus of an HM-3 lithotripter operated at 20 kV and 1-Hz pulse repetition rate. It was found that the physical properties of BegoStone are comparable to that of hard kidney stones such as calcium oxalate monohydrate stones. In comparison to the widely use stone phantoms made of plaster-of-Paris, BegoStone is much denser and harder, and more difficult to fragment in SWL. Yet, both types of stone phantoms comminute progressively in SWL. In addition, BegoStone is abrasion resistant and does not soften in urine. Therefore, BegoStone may provide a reliable and consistent phantom material for both in vitro and in vivo studies of stone comminution in SWL.
Statistically stable ultrasonic imaging in random media
Authors: Berryman James G. , Borcea Liliana , Papanicolaou George C. , Tsogka Chrysoula
Published: October 2002

Analysis of array data from acoustic scattering in a random medium with a small number of isolated targets is performed in order to image and, thereby, localize the spatial position of each target. Because the host medium has random fluctuations in wave speed, the background medium is itself a source of scattered energy. It is assumed, however, that the targets are sufficiently larger and/or more reflective than the background fluctuations so that a clear distinction can be made between targets and background scatterers. In numerical simulations nonreflective boundary conditions are used so as to isolate the effects of the host randomness from those of the spatial boundaries, which can then be treated in a separate analysis. It is shown that the key to successful imaging is finding statistically stable functionals of the data whose extreme values provide estimates of scatterer locations. The best ones are related to the eigenfunctions and eigenvalues of the array response matrix, just as one might expect from prior work on array data processing in complex scattering media having homogeneous backgrounds. The specific imaging functionals studied include matched-field processing and linear subspace methods, such as MUSIC (MUtiple SIgnal Classification). But statistical stability is not characteristic of the frequency domain, which is often the province of these methods. By transforming back into the time domain after first diagonalizing the array data in the frequency domain, one can take advantage of both the time-domain stability and the frequency-domain orthogonality of the relevant eigenfunctions.
Economy of effort in different speaking conditions. I. A preliminary study of intersubject differences and modeling issues
Authors: Perkell Joseph S. , Zandipour Majid , Matthies Melanie L. , Lane Harlan
Published: October 2002

This study explores the hypothesis that clear speech is produced with greater “articulatory effort” than normal speech. Kinematic and acoustic data were gathered from seven subjects as they pronounced multiple repetitions of utterances in different speaking conditions, including normal, fast, clear, and slow. Data were analyzed within a framework based on a dynamical model of single-axis frictionless movements, in which peak movement speed is used as a relative measure of articulatory effort (Nelson, 1983). There were differences in peak movement speed, distance and duration among the conditions and among the speakers. Three speakers produced the “clear” condition utterances with movements that had larger distances and durations than those for “normal” utterances. Analyses of the data within a peak speed, distance, duration “performance space” indicated increased effort (reflected in greater peak speed) in the clear condition for the three speakers, in support of the hypothesis. The remaining four speakers used other combinations of parameters to produce the clear condition. The validity of the simple dynamical model for analyzing these complex movements was considered by examining several additional parameters. Some movement characteristics differed from those required for the model-based analysis, presumably because the articulators are complicated structurally and interact with one another mechanically. More refined tests of control strategies for different speaking styles will depend on future analyses of more complicated movements with more realistic models.
Dynamic typing in a statically typed language
Authors: Abadi Martín , Cardelli Luca , Pierce Benjamin , Plotkin Gordon
Published: October 2002

Statically typed programming languages allow earlier error checking, better enforcement of diciplined programming styles, and the generation of more efficient object code than languages where all type consistency checks are performed at run time. However, even in statically typed languages, there is often the need to deal with datawhose type cannot be determined at compile time. To handle such situations safely, we propose to add a type
Dynamic
whose values are pairs of a value
v
and a type tag
T
where
v
has the type denoted by
T
. Instances of
Dynamic
are built with an explicit tagging construct and inspected with a type safe
typecase
construct.

This paper explores the syntax, operational semantics, and denotational semantics of a simple language that includes the type
Dynamic
. We give examples of how dynamically typed values can be used in programming. Then we discuss an operational semantics for our language and obtain a soundness theorem. We present two formulations of the denotational semantics of this language and relate them to the operational semantics. Finally, we consider the implications of polymorphism and some implementation issues.
A behavioral notion of subtyping
Authors: Liskov Barbara H. , Wing Jeannette M.
Published: October 2002

The use of hierarchy is an important component of object-oriented design. Hierarchy allows the use of type families, in which higher level supertypes capture the behavior that all of their subtypes have in common. For this methodology to be effective, it is necessary to have a clear understanding of how subtypes and supertypes are related. This paper takes the position that the relationship should ensure that any property proved about supertype objects also holds for its subtype objects. It presents two ways of defining the subtype relation, each of which meets this criterion, and each of which is easy for programmers to use. The subtype relation is based on the specifications of the sub- and supertypes; the paper presents a way of specifying types that makes it convenient to define the subtype relation. The paper also discusses the ramifications of this notion of subtyping on the design of type families.
A unified model of pointwise equivalence of procedural computations
Authors: von Bank David G. , Shub Charles M. , Sebesta Robert W.
Published: October 2002

The execution of a program on a processor is viewed as a representation of that program going through a sequence of states. Each state change is manifested by the execution of a single instruction. Models that depend on this perspective are presented. The first is a static model of a description of a procedural computation. This model formalizes the description of the information in an executable module. Following this dynamic model of a procedural computation is given. This second model describes how a computation transitions from state to state and how the states of a computation are represented. Next, the state of a procedural computation is defined at certain well-defined points in its progression. These points represent potential points of correspondence to another instance of the computation. Then, the equivalence of these well-defined computation states is described. This refinement eliminates the nonmatching potential correspondences. The remaining points describe where the two computations are in the same state. These are precisely the points of equivalence of procedural computations. This final model of pointwise equivalence can be applied to the problem of migrating a computation from one processor to another (possibly architecturally dissimilar) processor.
Conjoining specifications
Authors: Abadi Martín , Lamport Leslie
Published: October 2002

We show how to specify components of concurrent systems. The specification of a system is the conjunction of its components' specifications. Properties of the system are proved by reasoning about its components. We consider both the decomposition of a given system into parts, and the composition of given parts to form a system.
Probabilistic predicate transformers
Authors: Morgan Carroll , McIver Annabelle , Seidel Karen
Published: October 2002

Probabilistic predicates generalize standard predicates over a state space; with probabilistic predicate transformers one thus reasons about imperative programs in terms of probabilistic pre- and postconditions. Probabilistic healthiness conditions generalize the standard ones, characterizing “real” probabilistic programs, and are based on a connection with an underlying relational model for probabilistic execution; in both contexts demonic nondeterminism coexists with probabilistic choice. With the healthiness conditions, the associated weakest-precondition calculus seems suitable for exploring the rigorous derivation of small probabilistic programs.
An abstract machine for tabled execution of fixed-order stratified logic programs
Authors: Sagonas Konstantinos , Swift Terrance
Published: October 2002

SLG resolution uses tabling to evaluate nonfloundering normal logic pr ograms according to the well-founded semantics. The SLG-WAM, which forms the engine of the XSB system, can compute in-memory recursive queries anorder of magnitute fasterthan current deductive databases. At the same time, the SLG-WAM tightly intergrates Prolog code with tabled SLG code, and executes Prolog code with minimal overhead compared to the WAM. As a result, the SLG-WAM brings to logic programming important termination and complexity properties of deductive databases. This article describes the architecture of the SLG-WAM for a powerful class of programs, the class offixed-order dynamically stratified programs. We offer a detailed description of the algorithms, data structures, and instructions that the SLG-WAM adds to the WAM, and a performance analysis of engine overhead due to the extensions.
Within ARM's reach
Authors: Fokkink Wan , Kamperman Jasper , Walters Pum
Published: October 2002

A new compilation technique for left-linear term-rewriting systems is presented, where rewrite rules are transformed into so-called minimal rewrite rules. These minimal rules have such a simple form that they can be viewed as instructions for an abstract rewriting machine (ARM).
Specification and verification of fault-tolerance, timing, and scheduling
Authors: Liu Zhiming , Joseph Mathai
Published: October 2002

Fault-tolerance and timing have often been considered to be
implementation issues of a program, quite distinct from the functional safety and liveness properties. Recent work has shown how these non-functional and functional properties can be verified in a similar way. However, the more practical question of determining whether a real-time program will meet its deadlines, i.e., showing that there is a feasible schedule, is usually done using scheduling theory, quite separately from the verification of other properties of the program. This makes it hard to use the results of scheduling analysis in the design, or redesign, of fault-tolerant and real-time programs. This article shows how fault-tolerance, timing, and schedulability can be specified and verified using a single notation and model. This allows a unified view to be taken of the functional and nonfunctional properties of programs and a simple transformational method to be usedto combine these properties. It also permits results from scheduling theory to be interpreted and used within a formal proof framework. The notation and model are illustrated using a simple example.
Interprocedural pointer alias analysis
Authors: Hind Michael , Burke Michael , Carini Paul , Choi Jong-Deok
Published: October 2002

We present practical approximation methods for computing and representing interprocedural aliases for a program written in a language that includes pointers, reference parameters, and recursion. We present the following contributions: (1) a framework for interprocedural pointer alias analysis that handles function pointers by constructing the program call graph while alias analysis is being performed; (2) a
flow-sensitive
interprocedural pointer alias analysis algorithm; (3) a
flow-insensitive
interprocedural pointer alias analysis algorithm; (4) a
flow-insensitive
interprocedural pointer alias analysis algorithm that incorporates
kill
information to improve precision; (5) empirical measurements of the efficiency and precision of the three interprocedural alias analysis algorithms.
A type system for object initialization in the Java bytecode language
Authors: Freund Stephen N. , Mitchell John C.
Published: October 2002

In the standard Java implementation, a Java language program is compiled to Java bytecode. This bytecode may be sent across the network to another site, where it is then executed by the Java Virtual Machine. Since bytecode may be written by hand, or corrupted during network transmission, the Java Virtual Machine contains a bytecode verifier that performs a number of consistency checks before code is run. These checks include type correctness and, as illus-trated by previous attacks on the Java Virtual Machine, are critical for system security. In order to analyze existing bytecode verifiers and to understand the properties that should be verified, we develop a precise specification of statically correct Java bytecode, in the form of a type system. Our focus in this article is a subset of the bytecode language dealing with object creation and initialization. For this subset, we prove, that, for every Java bytecode program that satisfies our typing constraints, every object is initialized before it is used. The type system is easily combined with a previous system developed by Stata and Abadi for bytecode subroutines. Our analysis of subroutines and object initialization reveals a previously unpub-lished bug in the Sun JDK bytecode verifier.
Dealing with world-model-based programs
Authors: Gini Giuseppina C. , Gini M. L.
Published: October 2002

We introduce POINTY, an interactive system for constructing world-model-based programs for robots. POINTY combines an interactive programming environment with the teaching-by-guiding methodology that has been successful in industrial robotics. Owing to its ability to control robots in real time, and to interact with the user, POINTY provides a friendly and powerful programming environment for robot applications. In the past few years, POINTY has been in use at Stanford to write, test, and debug various robot programs.
Local type inference
Authors: Pierce Benjamin C. , Turner David N.
Published: October 2002

We study two partial type inference methods for a language combining subtyping and impredicative polymorphism. Both methods are
local
in the sense that missing annotations are recovered using only information from adjacent nodes in the syntax tree, without long-distance constraints such as unification variables. One method infers type arguments in polymorphic applications using a local constraint solver. The other infers annotations on bound variables in function abstractions by propagating type constraints downward from enclosing application nodes. We motivate our design choices by a statistical analysis of the uses of type inference in a sizable body of existing ML code.
Ada exception handling: an axiomatic approach
Authors: Luckham David C. , Polak W.
Published: October 2002

A method of documenting exception propagation and handling in Ada programs is proposed. Exception propagation declarations are introduced as a new component of Ada specifications, permitting documentation of those exceptions that can be propagated by a subprogram. Exception handlers are documented by entry assertions. Axioms and proof rules for Ada exceptions given. These rules are simple extensions of previous rules for Pascal and define an axiomatic semantics of Ada exceptions. As a result, Ada programs specified according to the method can be analyzed by formal proof techniques for consistency with their specifications, even if they employ exception propagation and handling to achieve required results (i.e., nonerror situations). Example verifications are given.
Using types to analyze and optimize object-oriented programs
Authors: Diwan Amer , McKinley Kathryn S. , Moss J. Eliot B.
Published: October 2002

Object-oriented programming languages provide many software engineering benefits, but these often come at a performance cost. Object-oriented programs make extensive use of method invocations and pointer dereferences, both of which are potentially costly on modern machines. We show how to use types to produce effective, yet simple, techniques that reduce the costs of these features in Modula-3, a statically typed, object-oriented language. Our compiler performs type-based alias analysis to disambiguate memory references. It uses the results of the type-based alias analysis to eliminate redundant memory references and to replace monomorphic method invocation sites with direct calls. Using limit, static, and running time evaluation, we demonstrate that these techniques are effective, and sometimes perfect for a set of Modula-3 benchmarks.
Distributed cooperation with action systems
Authors: Back R. J. R. , Kurki-Suonio F.
Published: October 2002

Action systems provide a method to program distributed systems that emphasizes the overall behavior of the system. System behavior is described in terms of the possible interactions (actions) that the processes can engage in, rather than in terms of the sequential code that the processes execute. The actions provide a symmetric communication mechanism that permits an arbitrary number of processes to be synchronized by a common handshake. This is a generalization of the usual approach, employed in languages like CSP and Ada, in which communication is asymmetric and restricted to involve only two processes. Two different execution models are given for action systems: a sequential one and a concurrent one. The sequential model is easier to use for reasoning, and is essentially equivalent to the guarded iteration statement by Dijkstra. It is well suited for reasoning about system properties in temporal logic, but requires a stronger fairness notion than it is reasonable to assume a distributed implementation will support. The concurrent execution model reflects the true concurrency that is present in a distributed execution, and corresponds to the way in which the system is actually implemented. An efficient distributed implementation of action systems on a local area network is described. The fairness assumptions of the concurrent model can be guaranteed in this implementation. The relationship between the two execution models is studied in detail in the paper. For systems that will be called fairly serializable, the two models are shown to be equivalent. Proof methods are given for verifying this property of action systems. It is shown that for fairly serializable systems, properties that hold for any concurrent execution of the system can be established by temporal proofs that are conducted entirely within the simpler sequential execution model.
Web-enabled transformation of the brokerage industry
Authors: Looney Clayton A. , Chatterjee Debabroto
Published: October 2002

Understanding the strengths and limitations of emerging business models.
Gender differences in perceptions of web-based shopping
Authors: Van Slyke Craig , Comunale Christie L. , Belanger France
Published: October 2002

Women have yet to welcome Web-based shopping as readily as men. A primary factor for this state is how men and women view shopping. Understanding those differences will help vendors address this vital pool of consumers.
Hypercomputation
Authors: Teuscher Christof , Sipper Moshe
Published: October 2002

Can we physically implement a hypercomputer? So far no one has.
Photographic tone reproduction for digital images
Authors: Reinhard Erik , Stark Michael , Shirley Peter , Ferwerda James
Published: October 2002

A classic photographic task is the mapping of the potentially high dynamic range of real world luminances to the low dynamic range of the photographic print. This tone reproduction problem is also faced by computer graphics practitioners who map digital images to a low dynamic range print or screen. The work presented in this paper leverages the time-tested techniques of photographic practice to develop a new tone reproduction operator. In particular, we use and extend the techniques developed by Ansel Adams to deal with digital images. The resulting algorithm is simple and produces good results for a wide variety of images.
Motion graphs
Authors: Kovar Lucas , Gleicher Michael , Pighin Frédéric
Published: October 2002

In this paper we present a novel method for creating realistic, controllable motion. Given a corpus of motion capture data, we automatically construct a directed graph called a
motion graph
that encapsulates connections among the database. The motion graph consists both of pieces of original motion and automatically generated transitions. Motion can be generated simply by building walks on the graph. We present a general framework for extracting particular graph walks that meet a user's specifications. We then show how this framework can be applied to the specific problem of generating different styles of locomotion along arbitrary paths.
Precomputed radiance transfer for real-time rendering in dynamic, low-frequency lighting environments
Authors: Sloan Peter-Pike , Kautz Jan , Snyder John
Published: October 2002

We present a new, real-time method for rendering diffuse and glossy objects in low-frequency lighting environments that captures soft shadows, interreflections, and caustics. As a preprocess, a novel global transport simulator creates functions over the object's surface representing transfer of arbitrary, low-frequency incident lighting into
transferred radiance
which includes global effects like shadows and interreflections from the object onto itself. At run-time, these transfer functions are applied to actual incident lighting. Dynamic, local lighting is handled by sampling it close to the object every frame; the object can also be rigidly rotated with respect to the lighting and vice versa. Lighting and transfer functions are represented using low-order spherical harmonics. This avoids aliasing and evaluates efficiently on graphics hardware by reducing the shading integral to a dot product of 9 to 25 element vectors for diffuse receivers. Glossy objects are handled using matrices rather than vectors. We further introduce functions for radiance transfer from a dynamic lighting environment through a preprocessed object to neighboring points in space. These allow soft shadows and caustics from rigidly moving objects to be cast onto arbitrary, dynamic receivers. We demonstrate real-time global lighting effects with this approach.
A user interface for interactive cinematic shadow design
Authors: Pellacini Fabio , Tole Parag , Greenberg Donald P.
Published: October 2002

Placing shadows is difficult task since shadows depend on the relative positions of lights and objects in an unintuitive manner. To simplify the task of the modeler, we present a user interface for designing shadows in 3d environments. In our interface, shadows are treated as first-class modeling primitives just like objects and lights. To transform a shadow, the user can simply move, rescale or rotate the shadow as if it was a 2d object on the scene's surfaces.When the user transforms a shadow, the system moves lights or objects in the scene as required and updates the shadows in realtime during mouse movement. To facilitate interaction, the user can also specify constraints that the shadows must obey, such as never casting a shadow on the face of a character. These constraints are then verified in real-time, limiting mouse movement when necessary. We also integrate in our interface fake shadows typically used in computer animation. This allows the user to draw shadowed and non-shadowed regions directly on surfaces in the scene.
Robust treatment of collisions, contact and friction for cloth animation
Authors: Bridson Robert , Fedkiw Ronald , Anderson John
Published: October 2002

We present an algorithm to efficiently and robustly process collisions, contact and friction in cloth simulation. It works with any technique for simulating the internal dynamics of the cloth, and allows true modeling of cloth thickness. We also show how our simulation data can be post-processed with a collision-aware subdivision scheme to produce smooth and interference free data for rendering.
Modeling and rendering of realistic feathers
Authors: Chen Yanyun , Xu Yingqing , Guo Baining , Shum Heung-Yeung
Published: October 2002

We present techniques for realistic modeling and rendering of feathers and birds. Our approach is motivated by the observation that a feather is a branching structure that can be described by an L-system. The parametric L-system we derived allows the user to easily create feathers of different types and shapes by changing a few parameters. The randomness in feather geometry is also incorporated into this L-system. To render a feather realistically, we have derived an efficient form of the bidirectional texture function (BTF), which describes the small but visible geometry details on the feather blade. A rendering algorithm combining the L-system and the BTF displays feathers photorealistically while capitalizing on graphics hardware for efficiency. Based on this framework of feather modeling and rendering, we developed a system that can automatically generate appropriate feathers to cover different parts of a bird's body from a few "key feathers" supplied by the user, and produce realistic renderings of the bird.
All pairs shortest paths using bridging sets and rectangular matrix multiplication
Authors: Zwick Uri
Published: October 2002

We present two new algorithms for solving the All Pairs Shortest Paths (APSP) problem for weighted directed graphs. Both algorithms use fast matrix multiplication algorithms.The first algorithm solves the APSP problem for weighted directed graphs in which the edge weights are integers of small absolute value in
Õ
(
n
2+μ
) time, where μ satisfies the equation ω(1, μ, 1) = 1 + 2μ and ω(1, μ, 1) is the exponent of the multiplication of an
n
×
n
μ
matrix by an
n
μ
×
n
matrix. Currently, the best available bounds on ω(1, μ, 1), obtained by Coppersmith, imply that μ < 0.575. The running time of our algorithm is therefore
O
(
n
2.575
). Our algorithm improves on the
Õ
(
n
(3c+ω)/2
) time algorithm, where ω = ω(1, 1, 1) < 2.376 is the usual exponent of matrix multiplication, obtained by Alon et al., whose running time is only known to be
O
(
n
2.688
).The second algorithm solves the APSP problem
almost
exactly for directed graphs with
arbitrary
nonnegative real weights. The algorithm runs in Õ((
n
ω
/ϵ) log(
W
/ϵ)) time, where ϵ > 0 is an error parameter and
W
is the largest edge weight in the graph, after the edge weights are scaled so that the smallest non-zero edge weight in the graph is 1. It returns estimates of all the distances in the graph with a stretch of at most 1 + ϵ. Corresponding paths can also be found efficiently.
Recent advances in direct methods for solving unsymmetric sparse systems of linear equations
Authors: Gupta Anshul
Published: October 2002

During the past few years, algorithmic improvements alone have reduced the time required for the direct solution of unsymmetric sparse systems of linear equations by almost an order of magnitude. This paper compares the performance of some well-known software packages for solving general sparse systems. In particular, it demonstrates the consistently high level of performance achieved by WSMP---the most recent of such solvers. It compares the various algorithmic components of these solvers and discusses their impact on solver performance. Our experiments show that the algorithmic choices made in WSMP enable it to run more than twice as fast as the best among similar solvers and that WSMP can factor some of the largest sparse matrices available from real applications in only a few seconds on a 4-CPU workstation. Thus, the combination of advances in hardware and algorithms makes it possible to solve those general sparse linear systems quickly and easily that might have been considered too large until recently.
Enhancing creative design via software tools
Authors: Thomas John C. , Lee Alison , Danis Catalina
Published: October 2002

Why creative design is important.
Practical byzantine fault tolerance and proactive recovery
Authors: Castro Miguel , Liskov Barbara
Published: October 2002

Our growing reliance on online services accessible on the Internet demands highly available systems that provide correct service without interruptions. Software bugs, operator mistakes, and malicious attacks are a major cause of service interruptions and they can cause arbitrary behavior, that is, Byzantine faults. This article describes a new replication algorithm, BFT, that can be used to build highly available systems that tolerate Byzantine faults. BFT can be used in practice to implement real services: it performs well, it is safe in asynchronous environments such as the Internet, it incorporates mechanisms to defend against Byzantine-faulty clients, and it recovers replicas proactively. The recovery mechanism allows the algorithm to tolerate any number of faults over the lifetime of the system provided fewer than 1/3 of the replicas become faulty within a small window of vulnerability. BFT has been implemented as a generic program library with a simple interface. We used the library to implement the first Byzantine-fault-tolerant NFS file system, BFS. The BFT library and BFS perform well because the library incorporates several important optimizations, the most important of which is the use of symmetric cryptography to authenticate messages. The performance results show that BFS performs 2% faster to 24% slower than production implementations of the NFS protocol that are not replicated. This supports our claim that the BFT library can be used to build practical systems that tolerate Byzantine faults.
Smoothing an overlay grid to minimize linear distortion in texture mapping
Authors: Sheffer Alla , de Sturler Eric
Published: October 2002

Texture is an essential component of computer generated models. For a texture mapping procedure to be effective it has to generate continuous textures and cause only small mapping distortion. The
Angle Based Flattening (ABF)
parameterization method is guaranteed to provide a continuous (no foldovers) mapping. It also minimizes the angular distortion of the parameterization, including locating the optimal planar domain boundary. However, since it concentrates on minimizing the angular distortion of the mapping, it can introduce relatively large linear distortion.In this paper we introduce a new procedure for reducing length distortion of an existing parameterization and apply it to ABF results. The linear distortion reduction is added as a second step in a texture mapping computation. The new method is based on computing a mapping from the plane to itself which has length distortion very similar to that of the ABF parameterization. By applying the inverse mapping to the result of the initial parameterization, we obtain a new parameterization with low length distortion. We notice that the procedure for computing the inverse mapping can be applied to any other (convenient) mapping from the three-dimensional surface to the plane in order to improve it.The mapping in the plane is computed by applying weighted Laplacian smoothing to a Cartesian grid covering the planar domain of the initial mapping. Both the mapping and its inverse are provably continuous. Since angle preserving (conformal) mappings, such as ABF, locally preserve distances as well, the planar mapping has small local deformation. As a result, the inverse mapping does not significantly increase the angular distortion.The combined texture mapping procedure provides a mapping with low distance and angular distortion, which is guaranteed to be continuous.