bluuebunny/crossref_metadata_2025 huggingface dataset:
Tools and transformations—rigorous and otherwise—for practical database design
Authors: Rosenthal Arnon , Reiner David
Published: July 2002

We describe the tools and theory of a comprehensive system for database design, and show how they work together to support multiple conceptual and logical design processes. The Database Design and Evaluation Workbench (DDEW) system uses a rigorous, information-content-preserving approach to schema transformation, but combines it with heuristics, guess work, and user interactions. The main contribution lies in illustrating how theory was adapted to a practical system, and how the consistency and power of a design system can be increased by use of theory.

First, we explain why a design system needs multiple data models, and how implementation over a unified underlying model reduces redundancy and inconsistency. Second, we present a core set of small but fundamental algorithms that reaarange a schema without changing its information content. From these reusable components, we easily built larger tools and transformations that were still formally justified. Third, we describe heuristic tools that attempt to improve a schema, often by adding missing information. In these tools, unreliable techniques such as normalization and relationship inference are bolstered by system-guided user interactions to remove errors. We present a rigorous criterion for identifying unnecessary relationships, and discuss an interactive view integrator. Last, we examine the relevance of database theory to building these practically motivated tools and contrast the paradigms of system builders with those of theoreticians.
The statistical security of a statistical database
Authors: Traub J. F. , Yemini Y. , Woźniakowski H.
Published: July 2002

This note proposes a statistical perturbation scheme to protect a statistical database against compromise. The proposed scheme can handle the security of numerical as well as nonnumerical sensitive fields. Furthermore, knowledge of some records in a database does not help to compromise unknown records. We use Chebyshev's inequality to analyze the trade-offs among the magnitude of the perturbations, the error incurred by statistical queries, and the size of the query set to which they apply. We show that if the statistician is given absolute error guarantees, then a compromise is possible, but the cost is made exponential in the size of the database.
Hierarchical triangulation for multiresolution surface description
Authors: De Floriani Leila , Puppo Enrico
Published: July 2002

A new hierarchical triangle-based model for representing surfaces over sampled data is proposed, which is based on the subdivision of the surface domain into nested triangulations, called a
hierarchical triangulation (HT)
. The model allows compression of spatial data and representation of a surface at successively finer degrees of resolution. An HT is a collection of triangulations organized in a tree, where each node, except for the root, is a triangulation refining a face belonging to its parent in the hierarchy. We present a topological model for representing an HT, and algorithms for its construction and for the extraction of a triangulation at a given degree of resolution. The surface model, called a
hierarchical triangulated surface (HTS)
is obtained by associating data values with the vertices of triangles, and by defining suitable functions that describe the surface over each triangular patch. We consider an application of a piecewise-linear version of the HTS to interpolate topographical data, and we describe a specialized version of the construction algorithm that builds an HTS for a terrain starting from a high-resolution rectangular grid of sampled data. Finally, we present an algorithm for extracting representations of terrain at variable resolution over the domain.
Object-oriented parallel computation for plasma simulation
Authors: Norton Charles D. , Szymanski Boleslaw K. , Decyk Viktor K.
Published: July 2002

Object-oriented techniques promise to improve the software design and programming process by providing an application-oriented view of programming while facilitating modification and reuse. Since the software design crisis is particularly acute in parallel computation, these techniques have stirred the interest of the scientific parallel computing community. Large-scale applications of ever-growing complexity, particularly in the physical sciences and engineering, require parallel processing for efficiency. Since its introduction in the 1970s, Fortran 77 has been the language of choice to model these problems, due to its efficiency, its numerical stability, and the body of existing Fortran codes. However, the introduction of object-oriented languages provides new alternatives for parallel software development. Fortran 90 adds modern extensions (including object-oriented concepts) to the established methods of Fortran 77. Alternatively, object-oriented methodologies can be explored through languages such as C++, Eiffel, Smalltalk, and many others. Our selection among these required a language that was widespread and supported across multiple platforms (particularly supercomputers) with strong compiler optimizations. C++, while not a “pure” object-oriented language, was our choice, since it meets these criteria.
Navigating hierarchically clustered networks through fisheye and full-zoom methods
Authors: Schaffer Doug , Zuo Zhengping , Greenberg Saul , Bartram Lyn , Dill John , Dubs Shelli , Roseman Mark
Published: July 2002

Many information structures are represented as two-dimensional networks (connected graphs) of links and nodes. Because these network tend to be large and quite complex, people often perfer to view part or all of the network at varying levels of detail.
Hierarchical clustering
provides a framework for viewing the network at different levels of detail by superimposing a hierarchy on it. Nodes are grouped into clusters, and clusters are themselves place into other clusters. Users can then navigate these clusters until an appropiate level of detail is reached. This article describes an experiment comparing two methods for viewing hierarchically clustered networks. Traditional
full-zoom
techniques provide details of only the current level of the hierarchy.

In contrast,
fisheye views,
generated by the “variable-zoom” algorithm described in this article, provide information about higher levels as well. Subjects using both viewing methods were given problem-solving tasks requiring them to navigate a network, in this case, a simulated telephone system, and to reroute links in it. Results suggest that the greater context provided by fisheye views significantly improved user performance. Users were quicker to complete their task and made fewer unnecessary navigational steps through the hierarchy. This validation of fisheye views in important for designers of interfaces to complicated monitoring systems, such as control rooms for supervisory control and data acquistion systems, where efficient human performance is often critical. However, control room operators remained concerned about the size and visibility tradeoffs between the fine room operators remained concerned about the size and visibility tradeoffs between the fine detail provided by full-zoom techniques and the global context supplied by fisheye views. Specific interface feaures are required to reconcile the differences.
Free-ridership in the standards-setting process
Authors: Weiss Martin B. H. , Toyokuku Ronald T.
Published: July 2002

In many cases, standards have public goods attributes. As a result it is important to consider how the development costs are provided. It is well known that public goods, due to their nonexclusionary nature, are subject to free riders. We consider free-ridership in standardization in general, and examine the case of one standard, IEEE 802.3
i
(10BaseT) in particular. We show that free-ridership existed in the development of the 10BaseT standard, and in the subsequent product market, by specifying the criteria for the existence of free-ridership and by providing the necessary data to show that such an issue actually exists. We discuss the consequences of free-ridership and consider the implications for the standards development process in general.
Logical design for temporal databases with multiple granularities
Authors: Wang X. Sean , Bettini Claudio , Brodsky Alexander , Jajodia Sushil
Published: July 2002

The purpose of good database logical design is to eliminate data redundancy and isertion and deletion anomalies. In order to achieve this objective for temporal databases, the notions of
temporal types
, which formalize time granularities, and
temporal functional dependencies
(TFDs) are intrduced. A temporal type is a monotonic mapping from ticks of time (represented by positive integers) to time sets (represented by subsets of reals) and is used to capture various standard and user-defined calendars. A TFD is a proper extension of the traditional functional dependency and takes the form
X
→
μ
Y,
meaning that there is a unique value for
Y
during one tick of the temporal type μ for one particular
X
value. An axiomatization for TFDs is given. Because a finite set TFDs usually implies an infinite number of TFDs, we introduce the notion of and give an axiomatization for a
finite closure
to effectively capture a finite set of implied TFDs that are essential of the logical design. Temporal normalization procedures with respect to TFDs are given. Specifically, temporal Boyce-Codd normal form (TBCNF) that avoids all data redundancies due to TFDs, and temporal third normal form (T3NF) that allows dependency preservation, are defined. Both normal forms are proper extensions of their traditional counterparts, BCNF and 3NF. Decompositition algorithms are presented that give lossless TBCNF decompositions and lossless, dependency-preserving, T3NF decompositions.
An adaptive data replication algorithm
Authors: Wolfson Ouri , Jajodia Sushil , Huang Yixiu
Published: July 2002

This article addresses the performance of distributed database systems. Specifically, we present an algorithm for dynamic replication of an object in distributed systems. The algorithm is adaptive in the sence that it changes the replication scheme of the object i.e., the set of processors at which the object inreplicated) as changes occur in the read-write patern of the object (i.e., the number of reads and writes issued by each processor). The algorithm continuously moves the replication scheme towards an optimal one. We show that the algorithm can be combined with the concurrency control and recovery mechanisms of ta distributed database management system. The performance of the algorithm is analyzed theoretically and experimentally. On the way we provide a lower bound on the performance of any dynamic replication algorith.
An optimality proof of the LRU-
K
page replacement algorithm
Authors: O'Neil Elizabeth J. , O'Neil Patrick E. , Weikum Gerhard
Published: July 2002

This paper analyzes a recently published algorithm for page replacement in hierarchical paged memory systems [O'Neil et al. 1993]. The algorithm is called the LRU-
K
method, and reduces to the well-known LRU (Least Recently Used) method for
K
= 1. Previous work [O'Neil et al. 1993; Weikum et al. 1994; Johnson and Shasha 1994] has shown the effectiveness for
K
> 1 by simulation, especially in the most common case of
K
= 2. The basic idea in LRU-
K
is to keep track of the times of the last
K
references to memory pages, and to use this statistical information to rank-order the pages as to their expected future behavior. Based on this the page replacement policy decision is made: which memory-resident page to replace when a newly accessed page must be read into memory. In the current paper, we prove, under the assumptions of the independent reference model, that LRU-
K
is optimal. Specifically we show: given the times of the (up to)
K
most recent references to each disk page, no other algorithm
A
making decisions to keep pages in a memory buffer holding
n
- 1 pages based on this infomation can improve on the expected number of I/Os to access pages over the LRU-
K
algorithm using a memory buffer holding
n
pages. The proof uses the Bayesian formula to relate the space of actual page probabilities of the model to the space of observable page numbers on which the replacement decision is acutally made.
Simulation and sensitivity of linear analog circuits under parameter variations by Robust interval analysis
Authors: Shi C.-J. Richard , Tian Michael W.
Published: July 2002

An interval-mathematic approach is presented for frequency-domain
simulation and sensitivity analysis of linear analog circuits under parameter variations. With uncertain parameters represented as intervals, bounding frequency-domain responses is formulated as the problem of solving systems of linear interval equations. The formulation is based on a variant of modified nodal analysis, and is particularly amenable to interval analysis. Some characterization of the solution sets of systems of linear interval equations are derived. With these characterizations, an elegant and efficient algorithm is proposed to solve systems of linear interval equations. While the widely used Monte Carlo approach requires many circuit simulations to achieve even moderate accuracy, the computational cost of the proposed approach is about twice that of one circuit simulation. The computed response bounds contain provably, or are usually very close to, the actual response bounds. Further, sensitivity under parameter variations can be computed from the response bounds at minor computational cost. The algorithms are implemented in SPICE3F5, using sparse-matrix techniques and tested on several practical analog circuits.
A Mathematical Model for the Analysis of Contour-Line Data
Authors: Morse Stephen P.
Published: July 2002

This paper describes a mathematical model for the study of contour-line data. Formal definitions are given for the various classes of contour lines found on a contour map. The concept of cliff lines is introduced and the properties of both contour lines and cliff lines are investigated. The objective of the paper is to lay a foundation for the development of algorithms that will facilitate the digital computer solutions of problems involving contour-line data.
Interpolation Theorems for Resolution in Lower Predicate Calculus
Authors: Slagle James R.
Published: July 2002

The resolution principle is an inference rule for quantifier-free first-order predicate calculus. In the past, the completeness theorems for resolution and its refinements have been stated and proved for finite sets of clauses. It is easy (by Gödel's Compactness Theorem) and of practical interest to extend them to countable sets, thus allowing schemata representing denumerably many axioms. In addition, some theorems similar to Craig's Interpolation Theorem are proved for deduction by resolution. In propositional calculus, the theorem proved is stronger, whereas in predicate calculus the theorems proved are in some ways stronger and in some ways weaker than Craig's theorem. These interpolation theorems suggest procedures which could be embodied in computer programs for automatic proof finding and consequence finding.
Eigenvalues of a symmetric 3 × 3 matrix
Authors: Smith Oliver K.
Published: July 2002

Recently, in order to find the principal moments of inertia of a large number of rigid bodies, it was necessary to compute the eigenvalues of many real, symmetric 3 × 3 matrices. The available eigenvalue subroutines seemed rather heavy weapons to turn upon this little problem, so an explicit solution was developed. The resulting expressions are remarkably simple and neat, hence this note.
On approaches to the study of social issues in computing
Authors: Mowshowitz Abbe
Published: July 2002

This paper identifies and analyzes technical and nontechnical biases in research on social issues in computing. Five positions—
technicism, progressive individualism, elitism, pluralism,
and
radical criticism
—which reflect major streams of contemporary social thought are examined. The analysis of positions documents the close relationship between research and policy formation and reveals the misleading and dangerous character of the presumption of scholarly objectivity in research on social issues.
Information transfer and area-time tradeoffs for VLSI multiplication
Authors: Abelson Harold , Andreae Peter
Published: July 2002

The need to transfer information between processing elements can be a major factor in determining the performance of a VLSI circuit. We show that communication considerations alone dictate that any VLSI design for computing the 2
n
-bit product of two
n
-bit integers must satisfy the constraint
AT
2
≥
n
2
/64 where
A
is the area of the chip and
T
is the time required to perform the computation. This same tradeoff applies to circuits which can shift
n
-bit words through
n
different positions.
Knowledge in multiagent systems
Authors: Lomuscio Alessio R. , van der Meyden Ron , Ryan Mark
Published: July 2002

The semantic framework for the modal logic of knowledge due to Halpern and Moses provides a way to ascribe knowlegde to agents in distributed and multiagent systems. In this paper we study two special cases of this framework:full systemsandhypercubes. Both model static situtations in which no agents has any information about another agent's state. Full systems and hypercubes are an appropriate model for the initial configurations of many systems of interest. We establish a correspondence between full systems and hypercube systems and certain classes of Kripke frames. We show that these classes of systems correspond to the same logic. Moreover, this logic is also the same as that generated by the larger class ofweakly directed frames. We provide a sound and complete axiomatization, S5WDnof this logic, and study its computational complexity. Finally, we show that under certain natural assumptions, in a model where knowledge evolves over time, S5WDncharacteristics the properties of knowledge not just at the initial configuration, but also at all later configurations. In this particular, this holds forhomogeneous broadcast systems,which capture settings in which agents are intially ignorant of each others local states, operate synchronously, have perfect recall, and can communicate only by broadcasting.
A modification of Warshall's algorithm for the transitive closure of binary relations
Authors: Warren Henry S.
Published: July 2002

An algorithm is given for computing the transitive closure of a binary relation that is represented by a Boolean matrix. The algorithm is similar to Warshall's although it executes faster for sparse matrices on most computers, particularly in a paging environment.
Programming languages
Authors: Sammet Jean E.
Published: July 2002

This paper discusses both the history and future of programming languages ( = higher level languages). Some of the difficulties in writing such a history are indicated. A key part of the paper is a tree showing the chronological development of languages and their interrelationships. Reasons for the proliferation of languages are given. The major languages are listed with the reasons for their importance. A section on chronology indicates the happenings of the significant previous time periods and the major topics of 1972. Key concepts other than specific languages are discussed.
Organizing matrices and matrix operations for paged memory systems
Authors: McKellar A. C. , Coffman E. G.
Published: July 2002

Matrix representations and operations are examined for the purpose of minimizing the page faulting occurring in a paged memory system. It is shown that carefully designed matrix algorithms can lead to enormous savings in the number of page faults occurring when only a small part of the total matrix can be in main memory at one time. Examination of addition, multiplication, and inversion algorithms shows that a partitioned matrix representation (i.e. one submatrix or partition per page) in most cases induced fewer page faults than a row-by-row representation. The number of page-pulls required by these matrix manipulation algorithms is also studied as a function of the number of pages of main memory available to the algorithm.
Peephole optimization
Authors: McKeeman W. M.
Published: July 2002

Redundant instructions may be discarded during the final stage of compilation by using a simple optimizing technique called peephole optimization. The method is described and examples are given.
A serial technique to determine minimum paths
Authors: Weimer Don L.
Published: July 2002

The need to determine minimum paths through a maze very often arises in such fields as traffic, transportation, communication and network studies. Computer analysis of these maze problems has been hampered in many cases due to the excessive size of the network under consideration. A technique has been developed to handle networks of very large magnitude by serially processing the network repetitively until only minimum paths remain.
ALGLIB, a simple symbol-manipulation package
Authors: Shearer J. M. , Wolfe M. A.
Published: July 2002

ALGLIB—a library of procedures that perform analytic differentiation and other simple symbolic manipulations—has certain advantages over existing and more comprehensive packages. It can be implemented in a high-level language of the user's choice using a pseudocode available from the authors, and it is easily interfaced with the user's programs.
Church-Rosser Thue systems and formal languages
Authors: McNaughton Robert , Narendran Paliath , Otto Friedrich
Published: July 2002

Since about 1971, much research has been done on Thue systems that have properties that ensure viable and efficient computation. The strongest of these is the Church-Rosser property, which states that two equivalent strings can each be brought to a unique canonical form by a sequence of length-reducing rules. In this paper three ways in which formal languages can be defined by Thue systems with this property are studied, and some general results about the three families of languages so determined are studied.
A fast algorithm for context-aware buffer insertion
Authors: Jagannathan Ashok , Hur Sung-Woo , Lillis John
Published: July 2002

We study the problem of performing buffer insertion in the context of a given layout. In a practical situation, there are restrictions on where buffers may be inserted; for instance, it may be possible to route wires over a preplaced macro cell, but may not be possible to insert buffers in that region. As a result, it is desirable to perform route planning and buffer insertion simultaneously. Furthermore it is necessary that such an algorithm be aware of the trade-off between cost (e.g., total capacitance) and delay. In this context we propose the delay reduction to cost ratio (DRCR) problem and present a fast algorithm for the same. Solutions identified by the algorithm are characterized with respect to the overall cost versus performance trade-off curve. Computational experiments demonstrate the viability of the approach.
An analytical cache model
Authors: Agarwal A. , Hennessy J. , Horowitz M.
Published: July 2002

Trace-driven simulation and hardware measurement are the techniques most often used to obtain accurate performance figures for caches. The former requires a large amount of simulation time to evaluate each cache configuration while the latter is restricted to measurements of existing caches. An analytical cache model that uses parameters extracted from address traces of programs can efficiently provide estimates of cache performance and show the effects of varying cache parameters. By representing the factors that affect cache performance, we develop an analytical model that gives miss rates for a given trace as a function of cache size, degree of associativity, block size, subblock size, multiprogramming level, task switch interval, and observation interval. The predicted values closely approximate the results of trace-driven simulations, while requiring only a small fraction of the computation cost.
Min-max heaps and generalized priority queues
Authors: Atkinson M. D. , Sack J.-R. , Santoro N. , Strothotte T.
Published: July 2002

A simple implementation of double-ended priority queues is presented. The proposed structure, called a min-max heap, can be built in linear time; in contrast to conventional heaps, it allows both FindMin and FindMax to be performed in constant time; Insert, DeleteMin, and DeleteMax operations can be performed in logarithmic time.

Min-max heaps can be generalized to support other similar order-statistics operations efficiently (e.g., constant time FindMedian and logarithmic time DeleteMedian); furthermore, the notion of min-max ordering can be extended to other heap-ordered structures, such as leftist trees.
On the storage requirement in the out-of-core multifrontal method for sparse factorization
Authors: Liu Joseph W. H.
Published: July 2002

Two techniques are introduced to reduce the working storage requirement for the recent multifrontal method of Duff and Reid used in the sparse out-of-core factorization of symmetric matrices. For a given core size, the reduction in working storage allows some large problems to be solved without having to use auxiliary storage for the working arrays. Even if the working arrays exceed the core size, it will reduce the amount of input-output traffic necessary to manipulate the working vectors. Experimental results are provided to demonstrate significant storage reduction on practical problems using the proposed techniques.
THE TAO OF STEM CELLS IN THE GERMLINE
Authors: Lin Haifan
Published: July 2002

▪ Abstract  Germline stem cells (GSCs) are the self-renewing population of germ cells that serve as the source for gametogenesis. GSCs exist in diverse forms, from those that undergo strict self-renewing asymmetric divisions in Drosophila to those that maintain their population by balancing between mitosis and differentiation in Caenorhabditis elegans. Most vertebrate spermatogonial GSCs appear to adopt an intermediate strategy. In most animals, GSCs are established during preadult gonadogenesis following the proliferation and migration of embryonic primordial germ cells. GSCs produce numerous gametes throughout the sexually active period of adult life. The establishment and self-renewing division of GSCs are controlled by extracellular signals such as hormones from the hypothalamic-pituitary axis and local interactions between GSCs and their neighboring cells. These extracellular signals may then influence differential gene expression, cell cycle machinery, and cytoskeletal organization of GSCs for their formation and/or divisional asymmetry. In addition, the GSC mechanism is related to that for germline and sex determination. Current knowledge has provided a solid framework for further study of GSCs and stem cells in general.
GENETICS OF LIPOPROTEIN ABNORMALITIES ASSOCIATED WITH CORONARY HEART DISEASE SUSCEPTIBILITY
Authors: Breslow Jan L.
Published: July 2002

▪ Abstract  Coronary heart disease is a complex genetic disease with many genes involved, environmental influences, and important gene-environment interactions. This review discusses the genetic basis of the principal lipoprotein abnormalities associated with coronary heart disease susceptibility in the general population. Individual sections discuss genes regulating LDL cholesterol, HDL cholesterol, and triglyceride levels. A section is included on the effects of the common apo E genetic variation on lipoprotein levels, as well as sections on the genetic regulation of lipoprotein(a) levels, genes regulating the inverse relationship between triglyceride-rich lipoproteins and HDL cholesterol levels, and our current understanding of the genetic basis of familial combined hyperlipidemia. It is clear that the field has progressed, with early studies focused mainly on the association of candidate gene RFLPs with phenotypes, later studies of candidate genes in both parametric and nonparametric linkage studies, and now more and more studies combining linkage analysis with genome scans to identify new loci that influence lipoprotein phenotypes. The future should provide us with the capability to perform reasonable genetic profiling for lipoprotein abnormalities associated with coronary heart disease susceptibility.
PROTEIN AND LIPID REQUIREMENTS FOR ENDOCYTOSIS
Authors: D'Hondt Kathleen , Heese-Peck Antje , Riezman Howard
Published: July 2002

▪ Abstract  Genetic and biochemical studies in yeast and animal cells have led to the identification of many components required for endocytosis. In this review, we summarize our understanding of the endocytic machinery with an emphasis on the proteins regulating the internalization step of endocytosis and endosome fusion. Even though the overall endocytic machinery appears to be conserved between yeast and animals, clear differences exist. We also discuss the roles of phosphoinositides, sterols, and sphingolipid precursors in endocytosis, because in addition to proteins, these lipids have emerged as important determinants in the spatial and most likely temporal specificity of endocytic membrane trafficking events.
Thin Film Synthesis by Energetic Condensation
Authors: Monteiro Othon R
Published: July 2002

▪ Abstract  The use of energetic particles (ions and atoms) has become increasingly important in physical vapor deposition techniques. These deposition processes can be divided in two main classes: ion beam-assisted deposition and energetic condensation (or deposition). This review focuses on the latter, i.e. processes in which the actual depositing species have energies that far exceed ordinary thermal energies, namely energies greater than 20 eV. The phenomenology of the effect of these high-energy particles on the growth of thin films is first broadly presented, and then specific examples of film deposition are given. The examples drawn here are of films that have been prepared by metal plasma immersion implantation and deposition. The observed microstructures and functional properties of these films are discussed in terms of processing conditions.
MALE SEX DETERMINATION: Current Concepts of Male Sexual Differentiation
Authors: Gustafson, M.D Michael L. , Donahoe, M.D Patricia K.
Published: July 2002

▪ Abstract  In order for an infant to develop as a phenotypically complete male or female, a cascade of complex molecular and morphological events must occur at the appropriate time and in the correct sequence during ontogeny. The male embryo's genetic sex is determined by its chromosomal constituents, the most important of which is the sex-determining gene, or testis-determining factor (TDF), on the Y chromosome. Male gonadal sex, or testis formation, is subsequently thought to be determined by this gene and by other secondary pathways. The male gonad, in turn, normally produces hormones such as testosterone and Mullerian inhibiting substance (MIS) that regulate differentiation of the internal and external genitalia, thus determining phenotypic sex. When an abnormality develops in any of the above three processes, an intersex infant with ambiguous genitalia results from the incongruent genetic, gonadal, and phenotypic sex. Clinically, such 46XY males with intersex abnormalities present challenges for gender assignment, timely surgical intervention, and appropriate hormonal therapy.
RISKS OF HIV INFECTION IN THE HEALTH CARE SETTING
Authors: Fraser, M.D Victoria J. , Powderly, M.D., F.R.C.P.I William G.
Published: July 2002

▪ Abstract  Health care workers exposed to blood and body fluids have a low but measurable risk of occupational infection with human immunodeficiency virus (HIV). This risk is related to the prevalence of HIV among patients, the frequency of exposure to infected blood, and the method of exposure. The magnitude of risk is thus difficult to assess for any given situation, although the overall risk following percutaneous exposure is approximately 0.3%. Risk can be reduced by paying close attention to infection control procedures and by minimizing risky procedures. Exposure management should include preexposure education and immediate postexposure care and counseling. Chemoprophylaxis is widely used despite doubts as to its effectiveness, and much research is clearly needed to develop more effective prophylaxis. For patients, the risk of nosocomial acquisition of HIV remains extremely low and can be minimized by strict adherence to proper infection control procedures.
Renal Artery Stenosis: A Common, Treatable Cause of Renal Failure?
Authors: Textor Stephen C. , Wilcox Christopher S.
Published: July 2002

▪ Abstract  Chronic azotemic renovascular disease is common in patients with atherosclerosis. Its prevalence appears to be increasing in the aging population. How often it is the primary cause of end-stage renal disease (ESRD) is not yet certain. Some studies suggest that 10%–40% of elderly hypertensive patients with newly documented ESRD and no demonstrable primary renal disease have significant renal artery stenosis (RAS). Atherosclerotic vascular occlusive disease of the renal arteries does progress, but current rates of progression and occlusion are lower than those reported a decade ago. Methods of identifying patients whose renal function is at true risk from vascular occlusive disease and determining who will benefit from intervention remain elusive. The presence of RAS in an azotemic patient can be assessed with noninvasive and risk-free radiologic techniques, including Duplex doppler velicometry and magnetic resonance angiography. Functional tests that predict the change in renal function after revascularization are not yet available. However, a renal length of greater than 7.5 cm in the absence of renal cysts and a short history of renal functional deterioration indicate a good prognosis. Patients with recent deterioration in renal function, those with bilateral renal artery stenosis or stenosis to a single functioning kidney, those with flash pulmonary edema, advanced chronic renal failure, or ESRD (who have much to gain), those with reversible azotemia during angiotensin-converting enzyme inhibitor (ACEI) or angiotensin receptor antagonist (ARB) therapy, and those whose conditions cannot be managed medically should be considered for revascularization. Results from recent controlled clinical trials of the response to percutaneous transluminal renal artery angioplasty (PTRA) and stenting indicate that improvement in blood pressure control or renal function is not a predictable outcome of renal revascularization. In azotemic groups, 25%–30% of patients achieve important recovery of renal function. Thus, significant progress has been made recently in determining whether RAS is a frequent, treatable cause of renal failure. The decision to recommend revascularization remains a difficult balance between the risks and expense of the procedure and the undoubted benefits that accrue if renal function is successfully stabilized.
STATUS OF CACAO WITCHES' BROOM: Biology, Epidemiology, and Management
Authors: Purdy LH , Schmidt RA
Published: July 2002

▪ Abstract  Origins of Theobroma cacao and Crinipellis perniciosa occurred in the Amazon Basin region of South America, and their interaction, the witches' broom disease, was first described in the late 1700s. The 100 years of scientific investigations of witches' broom of cacao that began in the 1890s developed the present state of knowledge of the biology and epidemiology of witches' broom that are discussed. Recommended management to reduce the deleterious effects of witches' broom on cacao production include the use of phytosanitation (removal of diseased plant parts), applications of chemical fungicides, and the use of host resistance. At present, there is a paucity of resistant planting materials, and efforts to evaluate germplasm for resistance to witches' broom are described. Research topics to augment present knowledge about witches' broom of cacao are presented with the hope that disease management can be improved.
Renoprotective Effect of Chronic Adrenomedullin Infusion in Dahl Salt-Sensitive Rats
Authors: Nishikimi Toshio , Mori Yosuke , Kobayashi Naohiko , Tadokoro Kazuyoshi , Wang Xin , Akimoto Kazumi , Yoshihara Fumiki , Kangawa Kenji , Matsuoka Hiroaki
Published: July 2002

The present study was designed to examine whether chronic adrenomedullin infusion has renoprotective effects in hypertensive renal failure and the mechanism by which chronic adrenomedullin infusion exerts its effects. Dahl salt-sensitive rats and Dahl salt-resistant rats were fed a high salt diet starting at 6 weeks of age. Recombinant human adrenomedullin or vehicle was infused for 7 weeks in 11-week-old Dahl salt-sensitive rats. Dahl salt-resistant rat was used as a control. After 7 weeks, untreated Dahl salt-sensitive rats were characterized by decreased kidney function, abnormal morphological findings, increased hormone levels, increased renal tissue angiotensin II levels, and altered mRNA expressions of transforming growth factor β (TGF-β) and components of the renin-angiotensin system compared with Dahl salt-resistant rats. Chronic adrenomedullin treatment significantly improved renal function (serum creatinine −87%, creatinine clearance +114%, urinary protein excretion −59%) and histological findings (glomerular injury score −54%) without changing mean arterial pressure compared with untreated Dahl salt-sensitive rats. Interestingly, long-term human adrenomedullin infusion decreased the endogenous rat adrenomedullin level (−97%) with a slight increase of human adrenomedullin level. Chronic adrenomedullin treatment also significantly inhibited the increase of plasma renin concentration (−269%), aldosterone level (−82%), and renal tissue angiotensin II levels (−60%). Furthermore, adrenomedullin infusion significantly decreased the increases of mRNA expressions of TGF-β (− 63%), angiotensin-converting enzyme (−137%), renin (−230%), and angiotensinogen (−38%) in renal cortex. These results suggest that increased endogenous adrenomedullin plays a compensatory role in chronic hypertensive renal failure and that long-term adrenomedullin infusion has renoprotective effects in this type of hypertension model, partly via inhibition of the circulating and renal renin-angiotensin system.
Fertile Spaces: The Productivity of Urban Space in Northern Europe
Authors: Arnade Peter , Howell Martha C. , Simons Walter
Published: July 2002

Spatial theory—the study of the relationship between material and discursive spatial practices—has great potential for recasting our understanding of urban life in Europe during the late medieval and early modern period, a formative moment in the history of Western urbanity. Urban space—and spaces— acquired powerful, effective valences in this age, producing new social possibilities and new historical actors while simulataneously eliminating others. Examining spatial practices through the lens of legal space, ritual space, and textual space not only exposes the assumptions about early modern urbanity that underlay existing historiography on city space in the period but also points toward the spatial histories that have not yet been written on markets, gender, and the public.
Urban Space and Political Conflict in Late Medieval Flanders
Authors: Boone Marc
Published: July 2002

Urban public space was a forum for political contests between cities of the Low Countries—particularly Ghent—and the late medieval Burgundian state. Contrary to much of the scholarship on the Low Countries' urban history of the late Middle Ages, civic space was independentof marketact ivities, however important these activities were. In the long fierce contests over rights and privileges waged by the late medieval cities of the southern Low Countries against princely hegemony, possession of civic spaces became the ultimate sign of political legitimacy. But their ultimate possessors often destroyed them, thus ending their power to confer legitimacy on future challengers and/or erasing memory of their defilement at the hands of pretenders.
Condition R
Authors: Lidz Jeffrey
Published: July 2002

Reinhart and Reuland (1993) partition the set of anaphors into two syntactic subclasses: SELF anaphors, which reflexivize predicates, and, SE anaphors, which, like pronominals, do not. This partition is intended to capture the antilocality of the SE anaphors. I argue that the appropriate partitioning of anaphors is semantic and not syntactic. Reinhart and Reuland's SELF anaphors are “near-reflexives,” interpreted as a representation of their antecedents, whereas their SE anaphors are “pure-reflexives,” requiring identity with their antecedents. The antilocality effects with pure reflexives are due to Condition R, a principle requiring reflexivity to be lexically expressed. The Condition R approach correctly accounts for the meanings of the two kinds of anaphors, grouping the near reflexives with pronominals and names, and correctly dissociates semantic reflexivity from the calculation of syntactic binding domains.
When True Recognition Suppresses False Recognition: Evidence from Amnesic Patients
Authors: Schacter Daniel L. , Verfaellie Mieke , Anes Michael D. , Racine Carrie
Published: July 2002

False recognition occurs when people mistakenly claim that a novel item is familiar. After studying lists of semantically related words, healthy controls show extraordinarily high levels of false recognition to nonstudied lures that are semantic associates of study list words. In previous experiments, we found that both Korsakoff and non-Korsakoff amnesic patients show reduced levels of false recognition to semantic associates, implying that the medial temporal/diencephalic structures that are damaged in amnesic patients are involved in the encoding and/or retrieval of information that underlies false recognition. These data contrast with earlier results indicating greater false recognition in Korsakoff amnesics than in control subjects. The present experiment tests the hypothesis that greater or lesser false recognition of semantic associates in amnesic patients, relative to normal controls, can be demonstrated by creating conditions that are more or less conducive to allowing true recognition to suppress false recognition. With repeated presentation and testing of lists of semantic associates, control subjects and both Korsakoff and non-Korsakoff amnesics showed increasing levels of true recognition across trials. However, control subjects exhibited decreasing levels of false recognition across trials, whereas Korsakoff amnesic patients showed increases across trials and non-Korsakoff amnesics showed a fluctuating pattern. Consideration of signal detection analyses and differences between the two types of amnesic patients provides insight into how mechanisms of veridical episodic memory can be used to suppress false recognition.
Gaussian Processes for Classification: Mean-Field Algorithms
Authors: Opper Manfred , Winther Ole
Published: July 2002

We derive a mean-field algorithm for binary classification with gaussian processes that is based on the TAP approach originally proposed in statistical physics of disordered systems. The theory also yields an approximate leave-one-out estimator for the generalization error, which is computed with no extra computational cost. We show that from the TAP approach, it is possible to derive both a simpler “naive” mean-field theory and support vector machines (SVMs) as limiting cases. For both mean-field algorithms and support vector machines, simulation results for three small benchmark data sets are presented. They show that one may get state-of-the-art performance by using the leave-one-out estimator for model selection and the built-in leave-one-out estimators are extremely precise when compared to the exact leave-one-out estimate. The second result is taken as strong support for the internal consistency of the mean-field approach.
Random Neural Networks with Multiple Classes of Signals
Authors: Gelenbe Erol , Fourneau Jean-Michel
Published: July 2002

By extending the pulsed recurrent random neural network (RNN) discussed in Gelenbe (1989, 1990, 1991), we propose a recurrent random neural network model in which each neuron processes several distinctly characterized streams of “signals” or data. The idea that neurons may be able to distinguish between the pulses they receive and use them in a distinct manner is biologically plausible. In engineering applications, the need to process different streams of information simultaneously is commonplace (e.g., in image processing, sensor fusion, or parallel processing systems). In the model we propose, each distinct stream is a class of signals in the form of spikes. Signals may arrive to a neuron from either the outside world (exogenous signals) or other neurons (endogenous signals). As a function of the signals it has received, a neuron can fire and then send signals of some class to another neuron or to the outside world. We show that the multiple signal class random model with exponential interfiring times, Poisson external signal arrivals, and Markovian signal movements between neurons has product form; this implies that the distribution of its state (i.e., the probability that each neuron of the network is excited) can be computed simply from the solution of a system of 2Cn simultaneous nonlinear equations where C is the number of signal classes and n is the number of neurons. Here we derive the stationary solution for the multiple class model and establish necessary and sufficient conditions for the existence of the stationary solution. The recurrent random neural network model with multiple classes has already been successfully applied to image texture generation (Atalay & Gelenbe, 1992), where multiple signal classes are used to model different colors in the image.
Tanzanian Theatre, From Marx to the Marketplace
Authors: Riccio Thomas
Published: July 2002

This is one of two articles in this TDR about Tanzanian perfor-mance. Riccio asks, What has been the “journey of Tanzania” from tribalism through colonialism to Marxism, and then to capital-ism and globalization as represented in performance?
Human-Centered Design of a Spine Biopsy Simulator and the Effects of Visual and Force Feedback on Path-Tracking Performance
Authors: Lathan Corinna , Cleary Kevin , Traynor Laura
Published: July 2002

Computed tomography (CT)-directed needle biopsies are routinely performed to gather tissue samples near the spine. As currently practiced, this procedure requires a great deal of spatial reasoning, skill, and training on the part of the interventional radiologist. Our goal was to evaluate the procedure through a task analysis and to make recommendations as to how the procedure could be improved through technological intervention. To this end, a spine biopsy surgical simulator was developed to mimic the current procedure and to serve as a development testbed for procedure innovation. Our methods for looking at the biopsy procedure itself included a task analysis (which produces a detailed list of tasks needed to complete a goal, their order, and time to completion) and an evaluation of human performance measures related to our simulator interface. Experiments were run to examine the effects of force and visual feedback on path-tracking performance and to determine the effects of time delay in the visual feedback on path-tracking performance. Force feedback improved performance in the conditions with visual feedback and in the conditions with visual feedback and time delay.
Fitness Landscapes and Evolvability
Authors: Smith Tom , Husbands Phil , O'Shea Michael
Published: July 2002

In this paper, we develop techniques based on evolvability statistics of the fitness land-scape surrounding sampled solutions. Averaging the measures over a sample of equal fitness solutions allows us to build up fitness evolvability portraits of the fitness land-scape, which we show can be used to compare both the ruggedness and neutrality in a set of tunably rugged and tunably neutral landscapes. We further show that the tech-niques can be used with solution samples collected through both random sampling of the landscapes and online sampling during optimization. Finally, we apply the techniques to two real evolutionary electronics search spaces and highlight differences between the two search spaces, comparing with the time taken to find good solutions through search.