bluuebunny/crossref_metadata_2025 huggingface dataset:
COMPARISON OF CARDIAC MAGNETIC FIELD DISTRIBUTIONS DURING DEPOLARIZATION AND REPOLARIZATION
Authors: SMITH F. E. , LANGLEY P. , TRAHMS L. , STEINHOFF U. , BOURKE J. P. , MURRAY A.
Published: January 2004

Multichannel magnetocardiography measures the magnetic field distribution of the human heart noninvasively from many sites over the body surface. Multichannel magnetocardiogram (MCG) analysis enables regional temporal differences in the distribution of cardiac magnetic field strength during depolarization and repolarization to be identified, allowing estimation of the global and local inhomogeneity of the cardiac activation process.

The aim of this study was to compare the spatial distribution of cardiac magnetic field strength during ventricular depolarization and repolarization in both normal subjects and patients with cardiac abnormalities, obtaining amplitude measurements by magnetocardiography.

MCGs were recorded at 49 sites over the heart from three normal subjects and two patients with inverted T-wave conditions. The magnetic field intensity during depolarization and repolarization was measured automatically for each channel and displayed spatially as contour maps. A Pearson correlation was used to determine the spatial relationship between the variables.

For normal subjects, magnetic field strength maps during depolarization (R-wave) showed two asymmetric regions of magnetic field strength with a high positive value in the lower half of the chest and a high negative value above this. The regions of high R-wave amplitude corresponded spatially to concentrated asymmetric regions of high magnetic field strength during repolarization (T-wave). Pearson-r correlation coefficients of 0.7 (p<0.01), 0.8 (p<0.01) and 0.9 (p<0.01) were obtained from this analysis for the three normal subjects. A negative correlation coefficient of -0.7 (p<0.01) was obtained for one of the subjects with inverted T-wave abnormalities, suggesting similar but inverted magnetic field and current distributions to normal subjects. Even with the high correlation values in these four subjects, the MCG was able to identify differences in the distribution of magnetic field strength, with a shift in the T-wave relative to the R-wave.

The measurement of cardiac magnetic field distribution during depolarization and repolarization of normal subjects and patients with clinical abnormalities should enable the improvement of theoretical models for the explanation of the cardiac depolarization and repolarization processes.
EQUILIBRATION OF SCROLL WAVE FILAMENTS IN THE VENTRICULAR WALL AND THE MINIMAL PRINCIPLE
Authors: BERENFELD OMER , WELLNER MARCEL , PERTSOV ARKADY M.
Published: January 2004

Scroll waves of electrical excitation are self-organized reentrant waveforms circling a filament and are a suspected cause of lethal cardiac arrhythmias. The lack of information about the filaments inside the cardiac wall raises the question of what is the dynamics of scroll waves and what equilibrium shape, if any, can we expect for their filaments. Here, we analyze the filament configuration and describe their equilibration in a curved slab of twisted fibers, a reasonably close model of the ventricular wall. We then generalize our findings by the use of the recently developed minimal principle to show that the filaments are predictable; namely, they are aligned with minimal resistance paths (geodesics) determined by the fiber configuration.
Measuring and characterizing end-to-end Internet service performance
Authors: Cherkasova Ludmila , Fu Yun , Tang Wenting , Vahdat Amin
Published: February 2004

Fundamental to the design of reliable, high-performance network services is an understanding of the performance characteristics of the service as perceived by the client population as a whole. Understanding and measuring such end-to-end service performance is a challenging task. Current techniques include periodic sampling of service characteristics from strategic locations in the network and instrumenting Web pages with code that reports client-perceived latency back to a performance server. Limitations to these approaches include potentially nonrepresentative access patterns in the first case and determining the location of a performance bottleneck in the second.This paper presents EtE monitor, a novel approach to measuring Web site performance. Our system passively collects packet traces from a server site to determine service performance characteristics. We introduce a two-pass heuristic and a statistical filtering mechanism to accurately reconstruct different client page accesses and to measure performance characteristics integrated across all client accesses. Relative to existing approaches, EtE monitor offers the following benefits: i) a latency breakdown between the network and server overhead of retrieving a Web page, ii) longitudinal information for all client accesses, not just the subset probed by a third party, iii) characteristics of accesses that are aborted by clients, iv) an understanding of the performance breakdown of accesses to dynamic, multitiered services, and v) quantification of the benefits of network and browser caches on server performance. Our initial implementation and performance analysis across three different commercial Web sites confirm the utility of our approach.
Fractal symbolic analysis
Authors: Menon Vijay , Pingali Keshav , Mateev Nikolay
Published: February 2004

Modern compilers restructure programs to improve their efficiency. Dependence analysis is the most widely used technique for proving the correctness of such transformations, but it suffers from the limitation that it considers only the memory locations read and written by a statement without considering what is being computed by that statement. Exploiting the semantics of program statements permits more transformations to be proved correct, and is critical for automatic restructuring of codes such as LU with partial pivoting.One approach to exploiting the semantics of program statements is symbolic analysis and comparison of programs.In principle, this technique is very powerful, but in practice, it is intractable for all but the simplest programs.In this paper, we propose a new form of symbolic analysis and comparison of programs which is appropriate for use in restructuring compilers.
Fractal
symbolic analysis is an
approximate
symbolic analysis that compares a program and its transformed version by repeatedly simplifying these programs until symbolic analysis becomes tractable while ensuring that equality of the simplified programs is sufficient to guarantee equality of the original programs.Fractal symbolic analysis combines some of the power of symbolic analysis with the tractability of dependence analysis. We discuss a prototype implementation of fractal symbolic analysis, and show how it can be used to solve the long-open problem of verifying the correctness of transformations required to improve the cache performance of LU factorization with partial pivoting.
Bridging the gap
Authors: Theofanos Mary Frances , Redish Janice (Ginny)
Published: February 2004

Guidelines for Accessible---and Usable---Web Sites: Observing Users Who Work With Screenreaders
The perils of data misreporting
Authors: Lorence Daniel P.
Published: February 2004

With physicians, information managers, and payers all influencing health care data classification, data can end up as an injured party. This hurts all of us, as reimbursement levels and error analysis increasingly rely on coded and classified data.
Design, retrieval, and assembly in component-based software development
Authors: Vitharana Padmal , Zahedi Fatemah "Mariam" , Jain Hemant
Published: February 2004

Until recently, anecdotal evidence could only suggest CBSD superiority in requirements identification. Here is a set of testable hypotheses to help distinguish hype from fact.
Introducing a country to Internet-enabled expert networks
Authors: Nordfors David , Bajuk Michel , Norberg Lena , Brinkmann Jochen , Forbush Dan
Published: February 2004

An expert network created in Sweden becomes a cost-effective testing ground for journalists worldwide to use Internet-enabled services for building a base of knowledge, experience, and contacts.
TransLight
Authors: DeFanti Tom , de Laat Cees , Mambretti Joe , Neggers Kees , St. Arnaud Bill
Published: February 2004

This global experiment wants to see if high-end applications needing transport capacities of multiple Gbps for up to hours at a time can be handled through an optical bypass network.
Introduction to Cryptography
Authors: Humphries Jeffrey W. , Carlisle Martin C.
Published: February 2004

This module introduces the concept of cryptography, from the simple Shift Cipher to the more complex Public-Key Cryptography. User will be introduced to some simple classic cryptographic algorithms.
Certificate-based authorization policy in a PKI environment
Authors: Thompson Mary R. , Essiari Abdelilah , Mudumbai Srilekha
Published: February 2004

The major emphasis of public key infrastructure has been to provide a cryptographically secure means of authenticating identities. However, procedures for authorizing the holders of these identities to perform specific actions still need additional research and development. While there are a number of proposed standards for authorization structures and protocols such as KeyNote, SPKI, and SAML based on X.509 or other key-based identities, none have been widely adopted. As part of an effort to use X.509 identities to provide authorization in highly distributed environments, we have developed and deployed an authorization service based on X.509 identified users and access policy contained in certificates signed by X.509 identified stakeholders. The major goal of this system, called Akenti, is to produce a usable authorization system for an environment consisting of distributed resources used by geographically and administratively distributed users. Akenti assumes communication between users and resources over a secure protocol such as transport layer security (TLS) to provide mutual authentication with X.509 certificates. This paper explains the authorization model and policy language used by Akenti, and how we have implemented an Apache authorization module to provide Akenti authorization.
Enforce POLA on processes to control viruses
Authors: Karp Alan H.
Published: February 2004

Applying the Principle of Least Authority on processes, instead of just on people, limits damage from viruses and worms.
Mobile commerce at crossroads
Authors: Jarvenpaa Sirkka L. , Lang Karl Reiner , Takeda Yoko , Tuunainen Virpi Kristiina
Published: February 2004

Lessons learned from an international study of users of mobile handheld devices and services.
Evolution of mobile location-based services
Authors: Rao Bharat , Minakakis Louis
Published: February 2004

Utilizing user location as a key determinant of information requirement needs.
Face recognition
Authors: Zhao W. , Chellappa R. , Phillips P. J. , Rosenfeld A.
Published: February 2004

As one of the most successful applications of image analysis and understanding, face recognition has recently received significant attention, especially during the past several years. At least two reasons account for this trend: the first is the wide range of commercial and law enforcement applications, and the second is the availability of feasible technologies after 30 years of research. Even though current machine recognition systems have reached a certain level of maturity, their success is limited by the conditions imposed by many real applications. For example, recognition of face images acquired in an outdoor environment with changes in illumination and/or pose remains a largely unsolved problem. In other words, current systems are still far away from the capability of the human perception system.This paper provides an up-to-date critical survey of still- and video-based face recognition research. There are two underlying motivations for us to write this survey paper: the first is to provide an up-to-date review of the existing literature, and the second is to offer some insights into the studies of machine recognition of faces. To provide a comprehensive survey, we not only categorize existing recognition techniques but also present detailed descriptions of representative methods within each category. In addition, relevant topics such as psychophysical studies, system evaluation, and issues of illumination and pose variation are covered.
Whatever happened to...?
Authors: Weiss Aaron
Published: February 2004

Examining the remnants of yesterday's
technologies du jour
When 2 + 2 = 5
Authors: Weiss Aaron
Published: February 2004

It used to be easy to know when someone's ripping you off. If at four o'clock in the morning some guy with an Australian accent is on your TV shouting out the merits of a telescoping mop, there are many good reasons not to buy it. But when you're browsing the aisles at your local ElectronicStuffWarehouse it becomes a whole lot harder to tell. And I'm not even talking about all those "rebates."
A versatile tool for student projects
Authors: Gilder Jason , Peterson Michael , Wright Jason , Doom Travis
Published: February 2004

Finding new and exciting senior design projects for undergraduate computer engineers can be challenging for both students and faculty advisors. The challenge is even more pronounced when attempting to construct interdisciplinary design projects to better meet ABET 2000 criteria and to better prepare graduating students for careers as engineers. We present an interdisciplinary, honors senior design project incorporating robotics control, algorithmic state machine design, reverse-engineering, assembly programming, and language, and basic compiler design. We believe this two-quarter project was extremely successful, and can be used as a model for similar design projects at other undergraduate institutions.
Effective page refresh policies for Web crawlers
Authors: Cho Junghoo , Garcia-Molina Hector
Published: February 2004

In this article, we study how we can maintain local copies of remote data sources "fresh," when the source data is updated autonomously and independently. In particular, we study the problem of
Web crawlers
that maintain local copies of remote Web pages for Web search engines. In this context, remote data sources (Websites) do not notify the copies (Web crawlers) of new changes, so we need to periodically
poll
the sources to maintain the copies up-to-date. Since polling the sources takes significant time and resources, it is very difficult to keep the copies completely up-to-date.This article proposes various refresh policies and studies their effectiveness. We first formalize the notion of "freshness" of copied data by defining two freshness metrics, and we propose a Poisson process as the change model of data sources. Based on this framework, we examine the effectiveness of the proposed refresh policies analytically and experimentally. We show that a Poisson process is a good model to describe the changes of Web pages and we also show that our proposed refresh policies improve the "freshness" of data very significantly. In certain cases, we got orders of magnitude improvement from existing policies.
Index-driven similarity search in metric spaces (Survey Article)
Authors: Hjaltason Gisli R. , Samet Hanan
Published: February 2004

Similarity search is a very important operation in multimedia databases and other database applications involving complex objects, and involves finding objects in a data set
S
similar to a query object
q
, based on some similarity measure. In this article, we focus on methods for similarity search that make the general assumption that similarity is represented with a distance metric
d
. Existing methods for handling similarity search in this setting typically fall into one of two classes. The first directly indexes the objects based on distances (distance-based indexing), while the second is based on mapping to a vector space (mapping-based approach). The main part of this article is dedicated to a survey of distance-based indexing methods, but we also briefly outline how search occurs in mapping-based methods. We also present a general framework for performing search based on distances, and present algorithms for common types of queries that operate on an arbitrary "search hierarchy." These algorithms can be applied on each of the methods presented, provided a suitable search hierarchy is defined.
Managing conflict in software testing
Authors: Cohen Cynthia F. , Birkin Stanley J. , Garfield Monica J. , Webb Harold W.
Published: February 2004

Conflict between software testers and developers is inevitable, but mindful managers minimize its effect on development projects through communication, mutual respect, even social interaction.
Effective practices for IT skills staffing
Authors: Schwarzkopf Albert B. , Mejias Roberto J. , Jasperson `Jon (Sean) , Saunders Carol S. , Gruenwald Hermann
Published: February 2004

How to identify, hire, and keep prized IT professionals with the skills companies need most to compete in uncertain technological and business times.
Understanding meteor burst communications technologies
Authors: Cumberland B. Craig , Valacich Joseph S. , Jessup Leonard M.
Published: February 2004

Seeking to realize the potential of a reemergent communications capability.
Programming languages and gender
Authors: Dattero Ronald , Galup Stuart D.
Published: February 2004

Comparing differences and similarities in programming language usage according to programmer gender.
Multibiometric systems
Authors: Jain Anil K. , Ross Arun
Published: February 2004

The latest research indicates using a combination of biometric avenues for human identification is more effective, and far more challenging.
Containment and equivalence for a fragment of XPath
Authors: Miklau Gerome , Suciu Dan
Published: February 2004

XPath is a language for navigating an XML document and selecting a set of element nodes. XPath expressions are used to query XML data, describe key constraints, express transformations, and reference elements in remote documents. This article studies the containment and equivalence problems for a fragment of the XPath query language, with applications in all these contexts.In particular, we study a class of XPath queries that contain branching, label wildcards and can express descendant relationships between nodes. Prior work has shown that languages that combine any two of these three features have efficient containment algorithms. However, we show that for the combination of features, containment is coNP-complete. We provide a sound and complete algorithm for containment that runs in exponential time, and study parameterized PTIME special cases. While we identify one parameterized class of queries for which containment can be decided efficiently, we also show that even with some bounded parameters, containment remains coNP-complete. In response to these negative results, we describe a sound algorithm that is efficient for all queries, but may return false negatives in some cases.
From discrepancy to declustering
Authors: Chen Chung-Min , Cheng Christine T.
Published: February 2004

Declustering schemes allocate data blocks among multiple disks to enable parallel retrieval. Given a declustering schemeD, itsresponse timewith respect to a queryQ,rt(Q), is defined to be the maximum number of data blocks of the query stored by the scheme in any one of the disks. If |Q| is the number of data blocks inQandMis the number of disks, thenrt(Q) is at least ⌈|Q|/M⌉. One way to evaluate the performance ofDwith respect to a set of range queries Q is to measure itsadditive error---the maximum difference ofrt(Q) from ⌈|Q|/M⌉ over all range queriesQ∈ Q.In this article, we consider the problem of designing declustering schemes for uniform multidimensional data arranged in ad-dimensional grid so that their additive errors with respect to range queries are as small as possible. It has been shown that for a fixed dimensiond≥ 2, any declustering scheme on anMdgrid, a grid with lengthMon each dimension, will always incur an additive error with respect to range queries of Ω(logM) whend= 2 and Ω(logd−1/2M) whend> 2.Asymptotically optimal declustering schemes exist for 2-dimensional data. However, the best general upper bound known so far for the worst-case additive errors ofd-dimensional declustering schemes,d≥ 3, isO(Md−1), which is large when compared to the lower bound. In this article, we propose two declustering schemes based on low-discrepancy points ind-dimensions. Whendis fixed, both schemes have an additive error ofO(logd−1M) with respect to range queries, provided that certain conditions are satisfied: the first scheme requires that the side lengths of the grid grow at a rate polynomial inM, while the second scheme requiresd≥ 2 andM=ptwhered≤p≤C,Ca constant, andtis a positive integer such thatt(d− 1) ≥ 2. These are the first multidimensional declustering schemes with additive errors proven to be near optimal.
Monadic datalog and the expressive power of languages for Web information extraction
Authors: Gottlob Georg , Koch Christoph
Published: February 2004

Research on information extraction from Web pages (wrapping) has seen much activity recently (particularly systems implementations), but little work has been done on formally studying the expressiveness of the formalisms proposed or on the theoretical foundations of wrapping. In this paper, we first study monadic datalog over trees as a wrapping language. We show that this simple language is equivalent to monadic second order logic (MSO) in its ability to specify wrappers. We believe that MSO has the right expressiveness required for Web information extraction and propose MSO as a yardstick for evaluating and comparing wrappers. Along the way, several other results on the complexity of query evaluation and query containment for monadic datalog over trees are established, and a simple normal form for this language is presented. Using the above results, we subsequently study the kernel fragment Elog
−
of the Elog wrapping language used in the Lixto system (a visual wrapper generator). Curiously, Elog
−
exactly captures MSO, yet is easier to use. Indeed, programs in this language can be entirely visually specified.
Evaluating collaborative filtering recommender systems
Authors: Herlocker Jonathan L. , Konstan Joseph A. , Terveen Loren G. , Riedl John T.
Published: February 2004

Recommender systems have been evaluated in many, often incomparable, ways. In this article, we review the key decisions in evaluating collaborative filtering recommender systems: the user tasks being evaluated, the types of analysis and datasets being used, the ways in which prediction quality is measured, the evaluation of prediction attributes other than quality, and the user-based evaluation of the system as a whole. In addition to reviewing the evaluation strategies used by prior researchers, we present empirical results from the analysis of various accuracy metrics on one content domain where all the tested metrics collapsed roughly into three equivalence classes. Metrics within each equivalency class were strongly correlated, while metrics from different equivalency classes were uncorrelated.
Latent semantic models for collaborative filtering
Authors: Hofmann Thomas
Published: February 2004

Collaborative filtering aims at learning predictive models of user preferences, interests or behavior from community data, that is, a database of available user preferences. In this article, we describe a new family of model-based algorithms designed for this task. These algorithms rely on a statistical modelling technique that introduces latent class variables in a mixture model setting to discover user communities and prototypical interest profiles. We investigate several variations to deal with discrete and continuous response variables as well as with different objective functions. The main advantages of this technique over standard memory-based methods are higher accuracy, constant time prediction, and an explicit and compact model representation. The latter can also be used to mine for user communitites. The experimental evaluation shows that substantial improvements in accucracy over existing methods and published results can be obtained.
Item-based top-Nrecommendation algorithms
Authors: Deshpande Mukund , Karypis George
Published: February 2004

The explosive growth of the world-wide-web and the emergence of e-commerce has led to the development ofrecommender systems---a personalized information filtering technology used to identify a set of items that will be of interest to a certain user. User-based collaborative filtering is the most successful technology for building recommender systems to date and is extensively used in many commercial recommender systems. Unfortunately, the computational complexity of these methods grows linearly with the number of customers, which in typical commercial applications can be several millions. To address these scalability concerns model-based recommendation techniques have been developed. These techniques analyze the user--item matrix to discover relations between the different items and use these relations to compute the list of recommendations.In this article, we present one such class of model-based recommendation algorithms that first determines the similarities between the various items and then uses them to identify the set of items to be recommended. The key steps in this class of algorithms are (i) the method used to compute the similarity between the items, and (ii) the method used to combine these similarities in order to compute the similarity between abasketof items and a candidate recommender item. Our experimental evaluation on eight real datasets shows that theseitem-basedalgorithms are up to two orders of magnitude faster than the traditional user-neighborhood based recommender systems and provide recommendations with comparable or better quality.
An interval constraint system for lattice domains
Authors: Fernández Antonio J. , Hill Patricia M.
Published: February 2004

We present a generic framework for defining and solving interval constraints on any set of domains (finite or infinite) that are lattices. The approach is based on the use of a single form of constraint similar to that of an indexical used by CLP for finite domains and on a particular generic definition of an interval domain built from an arbitrary lattice. We provide the theoretical foundations for this framework and a schematic procedure for the operational semantics. Examples are provided that illustrate how new (compound) constraint solvers can be constructed from existing solvers using lattice combinators and how different solvers (possibly on distinct domains) can communicate and hence, cooperate in solving a problem. We describe the language
clp
(
L
), which is a prototype implementation of this framework and discuss ways in which this implementation may be improved.
Synthesis of fault-tolerant concurrent programs
Authors: Attie Paul C. , Arora Anish , Emerson E. Allen
Published: February 2004

Methods for mechanically synthesizing concurrent programs from temporal logic specifications obviate the need to manually construct a program and compose a proof of its correctness. A serious drawback of extant synthesis methods, however, is that they produce concurrent programs for models of computation that are often unrealistic. In particular, these methods assume completely fault-free operation, that is, the programs they produce are fault-intolerant. In this paper, we show how to mechanically synthesize fault-tolerant concurrent programs for various fault classes. We illustrate our method by synthesizing fault-tolerant solutions to the mutual exclusion and barrier synchronization problems.
On exponential-time completeness of the circularity problem for attribute grammars
Authors: Wu Pei-Chi
Published: February 2004

Attribute grammars (AGs) are a formal technique for defining semantics of programming languages. Existing complexity proofs on the circularity problem of AGs are based on automata theory, such as writing pushdown acceptor and alternating Turing machines. They reduced the acceptance problems of above automata, which are exponential-time (EXPTIME) complete, to the AG circularity problem. These proofs thus show that the circularity problem is EXPTIME-
hard
, at least as hard as the most difficult problems in EXPTIME. However, none has shown that the problem is EXPTIME-complete. This paper presents an alternating Turing machine for the circularity problem. The alternating Turing machine requires polynomial space. Thus, the circularity problem is in EXPTIME and is then EXPTIME-complete.
A modal logic for mobile agents
Authors: De Nicola Rocco , Loreti Michele
Published: February 2004

Klaim is an experimental programming language that supports a programming paradigm where both processes and data can be moved across different computing environments. The language relies on the use of explicit localities. This paper presents a temporal logic for specifying properties of Klaim programs. The logic is inspired by Hennessy-Milner Logic (HML) and the μ-calculus, but has novel features that permit dealing with state properties and impact of actions and movements over the different sites. The logic is equipped with a complete proof system that enables one to prove properties of mobile systems.
Power minimization algorithms for LUT-based FPGA technology mapping
Authors: Li Hao , Katkoori Srinivas , Mak Wai-Kei
Published: February 2004

We study the technology mapping problem for LUT-based FPGAs targeting at power minimization. The problem has been proved to be NP-hard previously. Therefore, we present an efficient heuristic algorithm to generate low-power mapping solutions. The key idea is to compute and select low-power
K
-feasible cuts by an efficient incremental network flow computation method. Experimental results show that our algorithm reduces power consumption as well as area over the best algorithms reported in the literature. In addition, we present an extension to compute depth-optimal low-power mappings. Compared with Cutmap, a depth-optimal mapper with simultaneous area minimization, we achieve a 14% power savings on average without any depth penalty.
Fast memory bank assignment for fixed-point digital signal processors
Authors: Cho Jeonghun , Paek Yunheung , Whalley David
Published: February 2004

Most vendors of
digital signal processors
(DSPs) support a Harvard architecture, which has two or more memory buses, one for program and one or more for data and allow the processor to access multiple words of data from memory in a single instruction cycle. Also, many existing
fixed-point
DSPs are known to have an irregular architecture with
heterogeneous
registers, which contains multiple register files that are distributed and dedicated to different sets of instructions. Although there have been several studies conducted to efficiently assign data to multimemory banks, most of them assumed processors with relatively simple, homogeneous general-purpose registers. Thus, several vendor-provided compilers for DSPs that we examined were unable to efficiently assign data to multiple data memory banks, thereby often failing to generate highly optimized code for their machines. As a consequence, programmers for these DSPs often manually assign program variables to memories so as to fully utilize multimemory banks in their code. This paper reports on our recent attempt to address this problem by presenting an algorithm that helps the compiler to efficiently assign data to multimemory banks. Our algorithm differs from previous work in that it assigns variables to memory banks in separate,
decoupled
code generation phases, instead of a single, tightly coupled phase. The experimental results have revealed that our decoupled algorithm greatly simplifies our code generation process; thus our compiler runs extremely fast, yet generates target code that is comparable in quality to the code generated by a coupled approach.
What makes a Web site popular?
Authors: Kavassalis Petros , Lelis Stelios , Rafea Mahmoud , Haridi Seif
Published: February 2004

To ensure a constant increase in user interest, clicks, recommendations, loyalty, and market share, first understand the information flows and connection networks surrounding each Web site in cyberspace.
How to quickly find articles in the top IS journals
Authors: Schwartz Ruth Bolotin , Russo Michele C.
Published: February 2004

Informed searches begin by determining which indexes to use.
Stateful distributed interposition
Authors: Reumann John , Shin Kang G.
Published: February 2004

Interposition-based system enhancements for multitiered servers are difficult to build because important system context is typically lost at application and machine boundaries. For example, resource quotas and user identities do not propagate easily between cooperating services that execute on different hosts or that communicate with each other via intermediary services. Application-transparent system enhancement is difficult to achieve when such context information is obscured by complex service interaction patterns. We propose a basic mechanism for sharing contextual information across the tiers of multitier computations to support system enhancement for multitier servers and applications.This article introduces generic, cluster-wide context as a new, configurable abstraction for the OS. System administrator- or application-specified context tracking rules determine how context is associated with system processes, sockets, messages, how it is relayed along the interapplication communication channels, and how it is to be interpreted by system interpositions, thus realizing Stateful Distributed Interposition.
Role of Adrenergic Activity in Pressor Responses to Chronic Melanocortin Receptor Activation
Authors: Kuo Jay J. , da Silva Alexandre A. , Tallam Lakshmi S. , Hall John E.
Published: January 2004

Acute studies have shown that MC3/4-R stimulation increases sympathetic activity, but the role of adrenergic activation in mediating the cardiovascular and renal responses to chronic melanocortin 3- and 4-receptor (MC3/4-R) activation is unknown. The present study tested whether chronic MC3/4-R activation raises blood pressure and whether these changes are attenuated by α
1
+β-adrenergic blockade. Rats were instrumented with an intracerebroventricular (ICV) cannula and arterial and venous catheters for measurements of mean arterial pressure (MAP) and heart rate (HR) 24 hours per day, and intravenous infusions. After control measurements, rats were intravenously infused with either saline vehicle (n=7) or α
1
+ β-adrenergic antagonists (n=6, terazosin+propranolol, 10 mg/kg per day each) for 21 days. Five days after starting the vehicle or adrenergic blockade, the MC3/4-R agonist, MTII (10 ng/h), was infused ICV for 11 days followed by a 5-day recovery period. Another group of rats was infused with the adrenergic antagonists for 21 days but received the saline vehicle ICV for 11 days (n=7). MC3/4-R activation decreased food intake from 21±1 to 8±2 g/d by day 3 of MC3/4-R activation, and increased MAP and HR by an average of 8±2 mm Hg and 9±5 bpm, respectively. Adrenergic blockade did not alter the MC3/4-R-mediated decrease in food intake but abolished the increases in MAP and HR (1±2 mm Hg and −12±5 bpm, respectively, compared with control). ICV vehicle infusion during adrenergic blockade did not alter food intake or MAP. Glomerular filtration rate was unchanged in both the vehicle-infused and adrenergic blocked rats during MC3/4-R activation. These results indicate that the chronic actions of MC3/4-R activation on MAP and HR are mediated by adrenergic activation.
Prolonged Activation of the Baroreflex Produces Sustained Hypotension
Authors: Lohmeier Thomas E. , Irwin Eric D. , Rossing Martin A. , Serdar David J. , Kieval Robert S.
Published: January 2004

The role of baroreflexes in long-term control of arterial pressure is unresolved. To determine whether chronic activation of the baroreflex produces sustained hypotension, we developed a method for prolonged activation of the carotid baroreflex in conscious dogs. This was achieved by chronically implanting electrodes around both carotid sinuses and using an externally adjustable pulse generator to electrically activate the carotid baroreflex. Control values for mean arterial pressure (MAP) and heart rate were 93±3 mm Hg and 64±4 bpm, respectively. After control measurements, the carotid baroreflex was activated bilaterally for 7 days at a level that produced a prompt and substantial reduction in MAP, and for day 1 MAP was reduced to 75±4 mm Hg. Moreover, this hypotensive response was sustained throughout the entire 7 days of baroreflex activation (day 7, MAP=72±5 mm Hg). During prolonged baroreflex activation, heart rate decreased in parallel with MAP, although the changes were not as pronounced (day 7, heart rate=51±3 bpm). Prolonged baroreflex activation was also associated with ≈35% reduction in plasma norepinephrine concentration (control=87±15 pg/mL). After baroreflex activation, hemodynamic measures and plasma levels of norepinephrine returned to control levels. Interestingly, despite the pronounced fall in MAP, plasma renin activity did not increase during prolonged baroreflex activation. These data indicate that prolonged baroreflex activation can lead to substantial reductions in MAP by suppressing the sympathetic nervous system. Furthermore, sustained sympathoinhibitory effects on renin secretion may play an important role in mediating the long-term hypotensive response.
Persistent Remodeling of Resistance Arteries in Type 2 Diabetic Patients on Antihypertensive Treatment
Authors: Endemann Dierk H. , Pu Qian , De Ciuceis Carolina , Savoia Carmine , Virdis Agostino , Neves Mario F. , Touyz Rhian M. , Schiffrin Ernesto L.
Published: January 2004

We hypothesized that resistance arteries from diabetic patients with controlled hypertension have less remodeling than vessels from untreated hypertensive subjects. Eight normotensive subjects (aged 44±3 years, 3 men; values are mean±SEM), 19 untreated hypertensive subjects (46±2 years, 9 men), and 23 hypertensive subjects with type 2 diabetes mellitus under antihypertensive treatment (58±1 years, 15 men) were studied. Resistance arteries dissected from gluteal subcutaneous tissue were assessed on a pressurized myograph. Most diabetic patients (70%) were being treated with angiotensin-converting enzyme inhibitors. Although systolic blood pressure was still above the normotensive range in these patients (144±2 versus 150±3 mm Hg in hypertensive and 114±4 mm Hg in normotensive subjects), diastolic blood pressure was well controlled (83±2 mm Hg) and significantly lower compared with that in untreated hypertensives (100±1 mm Hg;
P
<0.001) but higher than in normotensives (76±3 mm Hg;
P
<0.05). Thus, pulse pressure was higher in diabetic patients (
P
<0.05). The media-to-lumen ratio of resistance arteries was greater in hypertensives (0.083±0.002) compared with normotensive controls (0.059±0.003;
P
<0.05) and was even higher in diabetic hypertensive subjects (0.105±0.004;
P
<0.001 versus normotensive controls). The medial cross-sectional area was greater in diabetic and hypertensive patients compared with normotensive controls (
P
<0.001). Acetylcholine-induced relaxation was impaired in vessels from hypertensive patients and from patients with both diabetes mellitus and hypertension (
P
<0.05 versus normotensive controls), whereas endothelium-independent vasorelaxation was similar in all groups. Despite effective antihypertensive treatment, resistance arteries from hypertensive diabetic patients showed marked remodeling, greater than that of vessels from untreated, nondiabetic, hypertensive subjects, in agreement with the high cardiovascular risk of subjects suffering from both diabetes and hypertension.
20-HETE and Circulating Insulin in Essential Hypertension With Obesity
Authors: Laffer Cheryl L. , Laniado-Schwartzman Michal , Nasjletti Alberto , Elijovich Fernando
Published: January 2004

Analogous to observations in Dahl salt-sensitive (SS) rats, we have shown that 20-hydroxyeicosatetraenoic acid (20-HETE) is involved in the pathogenesis of SS essential hypertension. A strong negative correlation between urine 20-HETE and body mass index (BMI) remains unexplained. We measured BP, urine sodium (UNaV), and 20-HETE in obese hypertensive subjects during a 24-hour salt load (160 mmol NaCl diet+2 L intravenous saline). We classified them into insulin-resistant (IR) (n=14) and insulin-sensitive (IS) (n=12), with the average insulin sensitivity index (SI=22.5×[fasting glucose×insulin]
−1
) of 3 days (cutoff for IR, SI <0.161 mL · L/μU · mmol). IR were older (50±1 versus 44±2,
P
<0.03), more obese (BMI 38.2±1.4 versus 32.0±1.5 kg/m
2
,
P
<0.01), and had higher insulin (39.2±2.3 versus 22.0±1.1 μU/mL,
P
<0.0001) and lower SI (0.084±0.009 versus 0.222±0.013,
P
<0.0001) than IS. Blood pressure, UNaV, and sodium balance did not differ between groups. SI correlated negatively with age (
r
=−0.39,
P
<0.05) and BMI (
r
=−0.53,
P
<0.01). Urine 20-HETE was less in IR than in IS when normalized by serum insulin (0.91±0.25 versus 2.24±0.46 μg · 24 hours
−1
/μU · mL
−1
,
P
<0.02), but not if uncorrected. Urinary 20-HETE excretion correlated negatively with insulin (
r
=−0.40,
P
<0.04), whereas the relationship between 20-HETE and SI was not statistically significant. Our data suggest that increased circulating insulin, not the state of insulin resistance, suppresses urine 20-HETE excretion in obese hypertensive subjects. Findings in experimental models suggest that an inhibitory effect of insulin on cytochrome P4504A, rather than effects of insulin on membrane-bound arachidonic acid or on its release to the cytosol, may explain our observation.
Effect of Dietary Sodium Intake on Blood Lipids
Authors: Harsha David W. , Sacks Frank M. , Obarzanek Eva , Svetkey Laura P. , Lin Pao-Hwa , Bray George A. , Aickin Mikel , Conlin Paul R. , Miller Edgar R. , Appel Lawrence J.
Published: January 2004

We evaluated the effect on serum lipids of sodium intake in 2 diets. Participants were randomly assigned to a typical American control diet or the Dietary Approaches to Stop Hypertension (DASH) diet, each prepared with 3 levels of sodium (targeted at 50, 100, and 150 mmol/d per 2100 kcal). The DASH diet is increased in fruits, vegetables, and low-fat dairy products and is reduced in saturated and total fat. Within assigned diet, participants ate each sodium level for 30 days. The order of sodium intake was random. Participants were 390 adults, age 22 years or older, with blood pressure of 120 to 159 mm Hg systolic and 80 to 95 mm Hg diastolic. Serum lipids were measured at baseline and at the end of each sodium period. Within each diet, sodium intake did not significantly affect serum total cholesterol, LDL cholesterol, HDL cholesterol, or triglycerides. On the control diet, the ratio of total cholesterol-to-HDL cholesterol increased by 2% from 4.53 on higher sodium to 4.63 on lower sodium intake (
P
=0.04). On the DASH diet, sodium intake did not affect this ratio. There was no dose-response of sodium intake on serum lipids or the cholesterol ratio in either diet. At each sodium level, total cholesterol, LDL cholesterol, and HDL cholesterol were lower on the DASH diet versus the typical American diet. There were no significant interactions between the effects of sodium and the DASH diet on serum lipids. In conclusion, changes in dietary sodium intake over the range of 50 to 150 mmol/d did not affect blood lipid concentrations.
Calcium Channel Blocker Azelnidipine Enhances Vascular Protective Effects of AT
1
Receptor Blocker Olmesartan
Authors: Jinno Toyohisa , Iwai Masaru , Li Zhen , Li Jian-Mei , Liu Hong-Wei , Cui Tai-Xing , Rakugi Hiromi , Ogihara Toshio , Horiuchi Masatsugu
Published: January 2004

The present studies were undertaken to investigate the potential effect of a calcium channel blocker (CCB) to enhance the inhibitory effect of an angiotensin (Ang) II type 1 (AT
1
) receptor blocker (ARB) on vascular injury and the cellular mechanism of the effect of CCB on vascular remodeling. In polyethylene cuff-induced vascular injury of the mouse femoral artery, proliferation of vascular smooth muscle cells (VSMCs) and neointimal formation associated with activation of extracellular signal-regulated kinase (ERK), and tyrosine-phosphorylation of signal transducer and activator of transcription (STAT)1 and STAT3, inflammatory response assessed by monocyte chemoattractant protein-1 and tumor necrosis factor-α expression, as well as oxidative stress such as expression of NADH/NADPH oxidase p22
phox
subunit and superoxide production, were less in AT
1a
receptor null mice. Administration of nonhypotensive doses of a CCB, azelnidipine (0.5 or 1 mg/kg per day) attenuated these parameters in wild-type and AT
1
a receptor null mice. Coadministration of lower doses of an ARB, olmesartan (0.5 mg/kg per day), and azelnidipine (0.1 mg/kg per day), which did not affect vascular remodeling, significantly inhibited these parameters in wild-type mice. Moreover, the effective dose of azelnidipine (1 mg/kg per day) exaggerated the inhibitory action of olmesartan at effective doses of 1 or 3 mg/kg per day on VSMC proliferation in the injured arteries. These results suggest that azelnidipine could inhibit vascular injury at least partly independent of the inhibition of AT
1
receptor activation and that azelnidipine could exaggerate the vascular protective effects of olmesartan, suggesting clinical possibility that the combination of CCB and ARB could be more effective in the treatment of vascular diseases.
Stroke in a Biracial Population
Authors: Kissela Brett , Schneider Alexander , Kleindorfer Dawn , Khoury Jane , Miller Rosemary , Alwell Kathleen , Woo Daniel , Szaflarski Jerzy , Gebel James , Moomaw Charles , Pancioli Arthur , Jauch Edward , Shukla Rakesh , Broderick Joseph
Published: February 2004

Background and Purpose—

Excess mortality resulting from stroke is an important reason why blacks have higher age-adjusted mortality rates than whites. This observation has 2 possible explanations: Strokes occur more commonly among blacks or blacks have higher mortality rates after stroke. Our population-based epidemiological study is set in the Greater Cincinnati/Northern Kentucky region of 1.31 million people, which is representative of the US white and black populations with regard to many demographic and socioeconomic characteristics.

Methods—

Hospitalized cases were ascertained by
International Classification of Diseases
(ninth revision) discharge codes, prospective screening of emergency department admission logs, and review of coroner’s cases. A sampling scheme was used to ascertain cases in the out-of-hospital setting. All potential cases underwent detailed chart abstraction by study nurses, followed by physician review. Race-specific incidence and case fatality rates were calculated.

Results—

We identified 3136 strokes during the study period (January 1, 1993, to June 30, 1994). Stroke incidence rates were higher for blacks at every age, with the greatest risk (2- to 5-fold) seen in young and middle-aged blacks (<65 years of age). Case fatality rates did not differ significantly in blacks compared with whites. Applying the resulting age- and race-specific rates to the US population in 2002, we estimate that 705 000 to 740 000 strokes have occurred in the United States, with a minimum of 616 000 cerebral infarctions, 67 000 intracerebral hemorrhages, and 22 000 subarachnoid hemorrhages.

Conclusions—

Excess stroke-related mortality in blacks is due to higher stroke incidence rates, particularly in the young and middle-aged. This excess burden of stroke incidence among blacks represents one of the most serious public health problems facing the United States.