bluuebunny/crossref_metadata_2025 huggingface dataset:
Concepts of cognition and consciousness
Authors: Nardi Bonnie A.
Published: November 2005

This paper considers theories of cognition and consciousness in four traditions: neuroscience, cognitive science, activity theory and the distributed cognition approach. It is most concerned with social theories of consciousness---activity theory and distributed cognition---but briefly considers biological and computational models as a foil or backdrop against which the social theories stand out more clearly.
A file structure supporting traversal recursion
Authors: Larson P.-A. , Deshpande V.
Published: November 2005

Traversal recursion is a class of recursive queries where the evaluation of the query involves traversal of a graph or a tree. This limited type of recursion arises in many applications. In this report we investigate a simple file structure that efficiently supports traversal recursion over large, acyclic graphs. The nodes of the graph are sorted in topological order and stored in a B-tree. Hence, traversal of the graph can be done in a single scan. Nodes and edges can also be inserted, deleted, and modified efficiently.
Concurrency control in groupware systems
Authors: Ellis C. A. , Gibbs S. J.
Published: November 2005

Groupware systems are computer-based systems that support two or more users engaged in a common task, and that provide an interface to a shared environment. These systems frequently require fine-granularity sharing of data and fast response times. This paper distinguishes real-time groupware systems from other multi-user systems and discusses their concurrency control requirements. An algorithm for concurrency control in real-time groupware systems is then presented. The advantages of this algorithm are its simplicity of use and its responsiveness: users can operate directly on the data without obtaining locks. The algorithm must know some semantics of the operations. However the algorithm's overall structure is independent of the semantic information, allowing the algorithm to be adapted to many situations. An example application of the algorithm to group text editing is given, along with a sketch of its proof of correctness in this particular case. We note that the behavior desired in many of these systems is non-serializable.
On the correctness of representing extended entity-relationship structures in the relational model
Authors: Markowitz Victor M. , Shoshani Arie
Published: November 2005

Although the relational representation of
Entity-Relationship
(ER) structures gained extensive coverage, scarce attention has been paid to the issue of
correctness
for such representations. Several mappings have been proposed for the representation of both ER and extended ER (EER) structures by relational schemas. The informal nature of most of these proposals, however, does not allow a precise evaluation of their correctness, nor a comparison of the various mappings. We propose a
canonical
relational representation for EER structures and prove its correctness. We claim that a relational schema represents correctly an EER structure if it has
equivalent
information-capacity with the corresponding canonical representation.

The second problem addressed by this paper is the normalization of relational schemas that represent EER structures. We examine the conditions required by this process and show that ignoring these conditions leads to erroneous analyses and inappropriate design decisions. We show that, under these conditions, the canonical relational representation of any (unrestricted) EER structure has an (information-capacity) equivalent
Boyce-Codd Normal Form
schema.
Issues in data stream management
Authors: Golab Lukasz , Özsu M. Tamer
Published: November 2005

Traditional databases store sets of relatively static records with no pre-defined notion of time, unless timestamp attributes are explicitly added. While this model adequately represents commercial catalogues or repositories of personal information, many current and emerging applications require support for on-line analysis of rapidly changing data streams. Limitations of traditional DBMSs in supporting streaming applications have been recognized, prompting research to augment existing technologies and build new systems to manage streaming data. The purpose of this paper is to review recent work in data stream management systems, with an emphasis on application requirements, data models, continuous query languages, and query evaluation.
Implementing recoverable requests using queues
Authors: Bernstein Philip A. , Hsu Meichun , Mann Bruce
Published: November 2005

Transactions have been rigorously defined and extensively studied in the database and transaction processing literature, but little has been said about the handling of the
requests
for transaction execution in commercial TP systems, especially distributed ones, managing the flow of requests is often as important as executing the transactions themselves.

This paper studies fault-tolerant protocols for managing the flow of transaction requests between clients that issue requests and servers that process them. We discuss how to implement these protocols using transactions and
recoverable queuing systems
. Queuing systems are used to move requests reliably between clients and servers. The protocols use queuing systems to ensure that the server processes each request exactly once and that a client processes each reply at least once. We treat request-reply protocols for single-transaction requests, for multi-transaction requests, and for requests that require interaction with the display after the request is submitted.
Concurrency control in multilevel-secure databases based on replicated architecture
Authors: Kogan Boris , Jajodia S.
Published: November 2005

In a multilevel secure database management system based on the
replicated
architecture, there is a separate database management system to manage data at or below each security level, and lower level data are replicated in all databases containing higher level data. In this paper, we address the open issue of concurrency control in such a system. We give a secure protocol that guarantees one-copy serializability of concurrent transaction executions and can be implemented in such a way that the size of the trusted code (including the code required for concurrency and recovery) is small.
Query graphs, implementing trees, and freely-reorderable outerjoins
Authors: Rosenthal Arnon , Galindo-Legaria Cesar
Published: November 2005

We determine when a join/outerjoin query can be expressed unambiguously as a query graph, without an explicit specification of the order of evaluation. To do so, we first characterize the set of expression trees that implement a given join/outerjoin query graph, and investigate the existence of transformations among the various trees. Our main theorem is that a join/outerjoin query is freely reorderable if the query graph derived from it falls within a particular class, every tree that “implements” such a graph evaluates to the same result.

The result has applications to language design and query optimization. Languages that generate queries within such a class do not require the user to indicate priority among join operations, and hence may present a simplified syntax. And it is unnecessary to add extensive analyses to a conventional query optimizer in order to generate legal reorderings for a freely-reorderable language.
The performance of a multiversion access method
Authors: Lomet David , Salzberg Betty
Published: November 2005

The
Time-Split B-tree
is an integrated index structure for a versioned timestamped database. It gradually migrates data from a current database to an historical database, records migrating when nodes split. Records valid at the split time are placed in both an historical node and a current node. This implies some redundancy. Using both analysis and simulation, we characterise the amount of redundancy, the space utilization, and the record addition (insert or update) performance for a spectrum of different rates of insertion versus update. Three splitting policies are studied which alter the conditions under which either time splits or key space splits are performed.
On the design of a query processing strategy in a distributed database environment
Authors: Yu C. T. , Chang C. C.
Published: November 2005

An algorithm is given to process a given query in a fragmented distributed data base environment. Unlike previous algorithms, it has the following desired features.(1) It makes use of redundant relations to reduce communication cost;(2) a copy of each relation referenced by the query is selected so that the set of relations are contained in the minimum number of sites;(3) an efficient algorithm to process fragments is provided;(4) all relations that need not be sent to the assembly site to produce the answer are identified. Thus, unnecessary sending of these relations across sites and processing on these relations, which are common in earlier algorithms, are avoided;(5) useless semi-joins are discarded and "worse" semi-joins are replaced by better ones;(6) a process to estimate the cost and the benefit of a semi-join, based on dynamic execution of semi-joins is introduced. It is expected that the new process is more accurate than earlier estimation process.The algorithm is easy to implement and is operational.
Functional dependencies on cyclic database schemes
Authors: Laver Kent , Mendelzon Alberto O. , Graham Marc H.
Published: November 2005

We study how functional dependencies affect the cyclicity of a database scheme; in particular, when does a set of functional dependencies make a cyclic database scheme behave like an acyclic one.A database scheme is
fd-acyclic
if every pairwise-consistent database state that satisfies the fd's is join-consistent. We give a simple characterization of fd-acyclicity over a restricted class of database schemes. We then give a tableau-based characterization for the general case that leads to an algorithm for testing fd-acyclicity. This algorithm actually solves the more general problem of query equivalence under functional dependencies and typed inclusion dependencies.
An experimental comparison of locking policies in a testbed database system
Authors: Kohler Walter H. , Wilner Kenneth C. , Stankovic John A.
Published: November 2005

Multiuser transaction processing and database systems commonly use well-formed, two-phase locking to maintain data consistency. The preliminary results presented here represent the first step of an experimental investigation of the impact of different locking schemes on transaction performance. Tests were performed using a simplified but functionally complete "testbed" system. The transaction throughput rates for three different locking policies (file level locking, page level locking, and mixed level locking) are compared as a function of the lock mode (exclusive or share) and the file size for a small centralized database application. The experimental results for this environment show that the choice of locking policy and lock mode can have a significant impact on transaction throughput performance. The tests also demonstrate the sensitivity of the conclusions to the choice of workload and system characteristics.
A high performance, universal, key associative access method
Authors: Lomet David B.
Published: November 2005

A new file organization is proposed that combines the advantages of digital B-trees and extendible hashing methods into one organization that can be used universally. The method, like these predecessors, relies on digital searching. The key notions are: (i) that multipage nodes are addressed by the root and can have both data and index entries, the mix of entries changing over time; and (ii) that these nodes can be doubled with file growth and, when this occurs, data nodes at the next level of the tree are absorbed into the pages of these nodes, frequently keeping data closer to the root and simultaneously improving utilization. The result is an unbalanced tree that we call a digital lopsided tree or DL-tree. The paper describes DL-trees and their operations, and examines their properties. The most important engineering issues involve the doubling process and the methods used to optimize the tree properties. Ways of dealing with these issues are suggested.
Remotely-sensed geophysical databases
Authors: Lohman Guy M. , Stoltzfus Joseph C. , Benson Anita N. , Martin Michael D. , Cardenas Alfonso F.
Published: November 2005

This paper presents the characteristics of scientific remotely-sensed databases that are relevant to --- and pose unique challenges for --- general-purpose database management systems (DBMSs). We describe a prototype system that integrates geophysical data and its metadata from both satellite and
in situ
sources, using a relational general-purpose DBMS to manage the catalog and observational data, and a video optical disk to archive images. Based upon our experience with this application, we suggest augmentations to DBMSs that would facilitate their use not only for scientific databases, but also for engineering, document, and even commercial database applications.
Relational queries in a domain based DBMS
Authors: Missikoff M. , Scholl M.
Published: November 2005

This paper addresses the problem of relational queries processing in the domain based database machine DBMAC. A brief description of the storage organisation of the domain based DBMS is first given. Then the operating principles of the domain based data-model, called D-model, is described through some examples. The central part of the paper deals with the translation of relational queries into operations on objects of the D-model. Objects of the D-model and a set of operations on these objects are first defined : this set
S
of operations is shown to be complete in that any relational query can be translated into D-model operations belonging to
S
.Finally we give a method for processing relation queries using D-model operations.The basic advantages to be expected from a domain based physical organization of data are :1. fast equi-join execution,2. a compact representation of intermediate results.The latter should lead to efficient processing of complex queries, provided a powerful parallel physical architecture is chosen for implementation.
An empirical comparison of B-trees, compact B-trees and multiway trees
Authors: Arnow David M. , Tenenbaum Aaron M.
Published: November 2005

It is well-known that the B-tree data structure yields excellent worst-case search costs and for that reason is widely employed in the organization of external files and in the implementation of data bases. In this paper, we examine general B-trees empirically and compare them with a less restrictive structure, the general multiway tree, and a more restrictive structure, the compact B-tree. We compare search costs, insertion costs, and space costs of these three structures for both small and large orders and indicate their relative utility for large and small data sets. Although there are cases when general multiway trees are more effective than B-trees, this is not the case for most practical situations. Compact B-trees are also shown to degrade rapidly in the presence of insertions and are therefore only useful for static data sets.
On complementary and independent mappings on databases
Authors: Keller Arthur M , Ullman Jeffrey D
Published: November 2005

We define the notion of independent views to indicate whether the range values of the two views may be achieved independently The concept of complementary views indicates when the domain element can be uniquely determined by the range values of the two complementary views We consider the relationship between independent and complementary views In unrestricted domains, a view (but not the identity or empty view) can have more than one complementary, independent view Databases, however, are more restricted domains They are finite power sets A view is monotonic if it preserves inclusion However, in finite power sets when all views are monotonic, if a given view has another view which is independent and complementary, then this view is unique.
Simplifying distributed database systems design by using a broadcast network
Authors: Chang Jo-Mei
Published: November 2005

Atomic broadcast and failure detection are powerful primitives for distributed database systems In the distributed database system LAMBDA, they are provided as network primitives In this paper, we show how atomic broadcast and failure detection simplify transaction commitment, concurrency control, and crash recovery Specifically, we give a simple
two-phase non-blocking
commit protocol, whereas three phases are required in a point-to-point network We also give a simplified read-one/write-all update algorithm for replicated data and an easily implemented log-based recovery algorithm providing uninterrupted transaction processingThe benefits of performing the atomic broadcast and failure detection at the network level are also discussed Performing these functions at the network level not only simplifies database protocols but also better utilizes the broadcast network fewer messages are transmitted Comparisons between LAMBDA and existing distributed database systems are also made
An implementation model for reasoning with complex objects
Authors: Chen Qiming , Gardarin Georges
Published: November 2005

In this paper, we first propose a natural syntactical extension of DATALOG called NESTED_DATALOG for dealing with complex objects represented as nested predicates. Then, we introduce the token object model which is a simple extension of the relational model with tokens to represent complex objects and support referential information sharing. An implementation model of a NESTED_DATALOG program is defined by mapping it to the token object model which remains a straightforward extension of classical logical databases. Through this work, we can accommodate two basic requirements. The availability of a rule language for reasoning with complex objects, and the mechanism for mapping a complex object rule program to a relational DBMS offering a pure DATALOG rule language. In summary, the main contributions of the paper are the definition of a rule language for complex objects and the development of a technique to compile this complex object rule language to classical DATALOG.
Optimal file distribution for partial match retrieval
Authors: Kim Myoung Ho , Pramanik Sakti
Published: November 2005

In this paper we present data distribution methods for parallel processing environment. The primary objective is to process partial match retrieval type queries for parallel devices.

The main contribution of this paper is the development of a new approach called FX (Fieldwise eXclusive) distribution for maximizing data access concurrency. An algebraic property of exclusive-or operation, and field transformation techniques are fundamental to this data distribution techniques. We have shown through theorems and corollaries that this FX distribution approach performs better than other methods proposed earlier. We have also shown, by computing probability of optimal distribution and query response time, that FX distribution gives better performance than others over a large class of partial match queries. This approach presents a new basis in which optimal data distribution for more general type of queries can be formulated.
A specialized data management system for parallel execution of particle physics codes
Authors: Bell Jean L.
Published: November 2005

The specialized data management system described in this paper was motivated by the need for much more efficient data management than a standard database management system could provide for particle physics codes in shared memory multiprocessor environments. The special characteristics of data and access patterns in particle physics codes need to be fully exploited in order to effect efficient data management. The data management system allows parameteric user control over system features not usually available to them, especially details of physical design and retrieval such as horizontal clustering, asynchronous I/O, and automatic distribution across processors. In the past, each physics code has constructed the equivalent of a primitive data management system from scratch. The system described in this paper is a generic system that can now be interfaced with a variety of physics codes.
Processing queries aganist database procedures: a performance analysis
Authors: Hanson Eric N.
Published: November 2005

A database procedure is a collection of queries stored in the database. Several methods are possible for processing queries that retrieve the value returned by a database procedure. The conventional algorithm is to execute the queries in a procedure whenever it is accessed. A second strategy requires caching the previous value returned by the database procedure. If the cached value is valid at the time of a query, the value is returned immediately. If the cached value has been invalidated by an update, the value is recomputed, stored back into the cache, and then returned. A third strategy uses a differential view maintenance algorithm to maintain an up-to-date copy of the value returned by the procedure. This paper compares the performance of these three alternatives. The results show that which algorithm is preferred depends heavily on the database environment, particularly, the frequency of updates and the size of objects retrieved by database procedures.
O2, an object-oriented data model
Authors: Lecluse C. , Richard P. , Velez F.
Published: November 2005

The
Altair
group is currently designing an object-oriented data base system called O
2
. This paper presents a formal description of the object-oriented data model of this system. It proposes a type system defined in the framework of a set-and-tuple data model. It models the well known inheritance mechanism and enforces strong typing.
HELPing writer and product team communication through online document design
Authors: McDuffee Julie S.
Published: November 2005

As technology advances, software companies must reevaluate and adapt their policies toward product development. The specific product addressed in this paper is an Asset/Liability Management System (ALMS) for the financial industry. The project involves three programmers, who will design and code the ALMS application and one writer, who will design and code an online help system. The end users sees one product, a diskette, that contains both the application and the documentation.
Documentation design based upon intuitive feature taxonomy and use logging
Authors: Berghel Hal , Roach David
Published: November 2005

Although the quality of documentation of office automation software has increased significantly in the past few years, current offerings are not without problems. Those difficulties which have to do with the design and organization of the documentation are addressed in this paper.

To illustrate, consider the following situations: 1) the command and control information which is commonly needed is either omitted or hard to find on the 'command card' or 'keyboard template' provided by the vendor, 2) the command or control information which we intuitively feel should be discussed in one section of the manual is actually located in an unrelated section, 3) the manual's table of contents does not seem to correspond well with the functional characteristics of the product, 4) the most appropriate command is not to be found in the manual's index, and 5) the 'help' facility frequently wastes rather than conserves time by providing the user with inappropriate alternatives. We maintain that these sorts of obstructions arise in many cases because insufficient attention has been given to an common sensical and intuitive analysis of the product's functionality as well as empirical use studies. We describe how these difficulties may be overcome by appeal to research results reported in the literature. Word processing software will be used to illustrate the technique.
Usability and hardcopy manuals: evaluating research designs and methods
Authors: Mirel Barbara
Published: November 2005

For the past decade, testing the usability of print software manuals has become a mature area of study, characterized by a wide range of qualitative and quantitative methods. Some of the most common methods include field observations, surveys, interviews, protocol analyses, focus groups, iterative testing, and quasi-experimental lab simulations [1]. Such diverse approaches to usability testing offer an opportunity for complementary inquiries and analyses. For example, findings from focus groups can provide key questions for experimental researchers to pursue in greater depth and with greater possibility for generalizability. Essentially, this complementary approach envisions an interaction between the academy, with its propensity toward pure, experimental research, and industry, with its more applied approaches for alpha and beta testing.

Patricia Wright, a specialist in usability studies, has long argued that integrating pure and applied research is the best means for expanding our knowledge about effective document design [2; 3]. Such integration reveals both the immediately applicable aspects of effective manuals and the more theoretical boundaries in textual features that make a difference for general types of tasks, readers, and contexts of use.

In order to realize the potential of conducting a conversation between pure and applied research, documentation researchers and practitioners must clearly understand the limitations that exist in the conclusions that investigators derive from specific methods of inquiry. In this article, I look solely at experimental usability tests that rely on quantitative methods of analysis. I analyze the ways in which the research designs and questions of the past ten years of experimental studies affect the strength of cumulative conclusions and the confidence we can have in those conclusions. My purpose is not to give preference to experimental research as the most important approach to usability testing. Far from it. Rather my critical review has two purposes: (1) to facilitate the dialogue between academic and industrial researchers by identifying the limits of current experimental findings; and (2) to propose research agendas and designs for future experimental usability tests that can strengthen the conclusions that such researchers offer for practical consideration.

My evaluation of ten years of experimental usability studies shows that many of the conclusions of these studies are not strong enough to serve as valid, generalizable, and replicable foundations for subsequent research, be it pure or applied. These conclusions can be strengthened by designing studies that pay more attention to the sequencing and integration of related investigations and that institute better controls for sample selection, size, and composition. This article discusses my overall findings, the details of which I will develop more fully in my presentation.
Documenting the software development process
Authors: Hopkins June S. , Jernow Jean M.
Published: November 2005

The Software Engineering Process Group (SEPG) at the Data Systems Division of Litton Systems, Inc., was given the task of documenting the software development process used within the division. This paper describes how the SEPG at Litton accomplished this task. It discusses the sources we used for guidance and describes the resulting documentation for defining the software development process and the methods and tools that support the process.

After reviewing the existing software process documentation at Litton, the SEPG concluded that three separate documents were required: a revised set of Software Policies and Procedures (PPGs), a Software Engineering Handbook, and a Software Management Handbook. The SEPG established working groups to develop these documents. The working group responsible for the Software Engineering Handbook decided to develop it as a user manual for the software development process. Following Weiss' guidelines for developing a usable user manual, the working group developed storyboards for sections of the manual. A model initially developed at IBM and refined by SEI and others was used to describe the software development process as a series of work tasks, each of which has entry criteria, exit criteria, objectives, and steps to perform.

Several authors developed the storyboards and the corresponding modules of the handbook. The handbook was partitioned into short modules, each of which has a topic sentence and a figure (where applicable). The result is a modular Software Engineering Handbook that is easy to read and maintain.

The use of working groups and the development of the Software Engineering Handbook as a user manual proved to be efficient and effective methods for generating high quality software process documentation.
Playing detective with full text searching software
Authors: Raymond Darrell R. , Fawcett Heather J.
Published: November 2005

Searching large text databases often resembles detective work. We explored this notion with an experiment in which subjects used powerful full text searching software to solve problems about the Arthur Conan Doyle story
The Hound of the Baskervilles
. The experiment was conducted in two parts: in the first part subjects attempted to teach themselves about the software using only the documentation; in the second part, subjects used the software to answer questions such as
What brand of cigarette does Watson smoke?
The experiment provided a great deal of feedback about the usability of the software and the documentation. Among the results that have wider implications are the need for better display of context, and a need for careful documentation of the characteristics of full text searching.
TRANSFORMING GROWTH FACTOR-β REGULATION OF IMMUNE RESPONSES
Authors: Li Ming O. , Wan Yisong Y. , Sanjabi Shomyseh , Robertson Anna-Karin L. , Flavell Richard A.
Published: November 2005

Transforming growth factor-β (TGF-β) is a potent regulatory cytokine with diverse effects on hemopoietic cells. The pivotal function of TGF-β in the immune system is to maintain tolerance via the regulation of lymphocyte proliferation, differentiation, and survival. In addition, TGF-β controls the initiation and resolution of inflammatory responses through the regulation of chemotaxis, activation, and survival of lymphocytes, natural killer cells, dendritic cells, macrophages, mast cells, and granulocytes. The regulatory activity of TGF-β is modulated by the cell differentiation state and by the presence of inflammatory cytokines and costimulatory molecules. Collectively, TGF-β inhibits the development of immunopathology to self or nonharmful antigens without compromising immune responses to pathogens. This review highlights the findings that have advanced our understanding of TGF-β in the immune system and in disease.
COMMENTARY ON THE PLEASURES OF SOLVING IMPOSSIBLE PROBLEMS OF EXPERIMENTAL PHYSIOLOGY
Authors: Webb Watt W.
Published: November 2005

▪ Abstract  This commentary presents a series of examples of “impossible experimental problems” that we have encountered over the years in addressing various challenging questions in physiology. We aim to show how stimulating the challenges of physiology can be and demonstrate how our naive invocation of methods from disparate fields of science and engineering has led to delightful resolutions of physiological challenges that were utterly new to this intrepid interdisciplinary researcher.
Effects of sodium nitrite on ischemia-reperfusion injury in the rat kidney
Authors: Basireddy Mahesh , Isbell T. Scott , Teng Xinjun , Patel Rakesh P. , Agarwal Anupam
Published: November 2005

Reactive oxygen and nitrogen species play a key role in the pathophysiology of renal ischemia-reperfusion (I/R) injury. Recent studies have shown that nitrite (NO2−) serves as an endogenous source of nitric oxide (NO), particularly in the presence of hypoxia and acidosis. Nanomolar concentrations of NO2−reduce injury following I/R in the liver and heart in vivo. The purpose of this study was to evaluate the role of NO2−in renal I/R injury. Male Sprague-Dawley rats underwent a unilateral nephrectomy followed by 45 min of ischemia of the contralateral kidney or sham surgery under isoflurane anesthesia. Animals received normal saline, sodium NO2−, or sodium nitrate (NO3−; 1.2 nmol/g body wt ip) at 22.5 min after induction of ischemia or 15 min before ischemia. A separate set of animals received saline, NO2−, or NO3−(0.12, 1.2, or 12 nmol/g body wt iv) 45 min before ischemia. Serum creatinine and blood urea nitrogen were increased following I/R injury but were not significantly different among treatment groups at 24 and 48 h after acute renal injury. Interestingly, NO3−administration appeared to worsen renal injury. Histological scoring for loss of brush border, tubular necrosis, and red blood cell extravasation showed no significant differences among the treatment groups. The results indicate that, contrary to the protective effects of NO2−in I/R injury of the liver and heart, NO2−does not provide protection in renal I/R injury and suggest a unique metabolism of NO2−in the kidney.
Characterization of the speed of a two‐phase interface in a porous medium
Authors: Abbassi Adil , Namah Gawtum
Published: November 2005

A typical situation of oil reservoir simulation is considered in a porous medium where the resident oil is displaced by water injection. An explicit expression of the speed of the oil‐water interface is given in a pseudo‐2D case via the resolution of an auxiliary Riemann problem. The explicit 2D solution is then corroborated with numerical simulations by solving the transport equation with a generalized scheme of Harten type.
Peristaltic transport of Johnson‐Segalman fluid under effect of a magnetic field
Authors: Elshahed Moustafa , Haroun Mohamed H.
Published: November 2005

The peristaltic transport of Johnson‐Segalman fluid by means of an infinite train of sinusoidal waves traveling along the walls of a two‐dimensional flexible channel is investigated. The fluid is electrically conducted by a transverse magnetic field. A perturbation solution is obtained for the case in which amplitude ratio is small. Numerical results are reported for various values of the physical parameters of interest.
Serotonin Transporter Function Is an Early Step in Left-Right Patterning in Chick and Frog Embryos
Authors: Fukumoto Takahiro , Blakely Randy , Levin Michael
Published: November 2005

The neurotransmitter serotonin has been shown to regulate a number of embryonic patterning events in addition to its crucial role in the nervous system. Here, we examine the role of two serotonin transporters, the plasma membrane serotonin transporter (SERT) and the vesicular monoamine transporter (VMAT), in embryonic left-right asymmetry. Pharmacological or genetic inhibitors of either SERT or VMAT specifically randomized the laterality of the heart and viscera in Xenopus embryos. This effect takes place during cleavage stages, and is upstream of the left-sided gene XNR-1. Targeted microinjection of an SERT-dominant negative construct confirmed the necessity for SERT function in embryonic laterality and revealed that the descendants of the right ventral blastomere are the most dependant upon SERT signaling in left-right patterning. Moreover, the importance of SERT and VMAT in laterality is conserved in chick embryos, being upstream of the early left-sided gene Shh. Endogenous transcripts of SERT and VMAT are expressed from the initiation of the primitive streak in chick and are asymmetrically expressed in Hensen’s node. Taken together our data characterize two new right-sided markers in chick gastrulation, identify a novel, early component of the left-right pathway in two vertebrate species, and reveal a new biological role for serotonin transport.
Gliogenic Radial Glial Cells Show Heterogeneity in the Developing Mouse Spinal Cord
Authors: Ogawa Yasuhiro , Takebayashi Hirohide , Takahashi Masanori , Osumi Noriko , Iwasaki Yasuno , Ikenaka Kazuhiro
Published: November 2005

The central nervous system of the mammalian embryo is organized according to the expression of region-specific transcription factors along the anteroposterior and/or the dorsoventral axis. For example, the dorsal ventricular zone (VZ) of the embryonic spinal cord expresses Pax3 and Pax7, the ventral VZ expresses Pax6, and the more ventral VZ expresses Nkx2.2. Properties of neuronal precursors located in the VZ are determined by the characteristic expression patterns of these transcription factors, leading to the generation of distinct classes of neurons. Recent studies demonstrated that radial glial cells produce neurons in addition to glia during central nervous system development. Thus, neuronal precursor diversity may be dependent upon the diversity of radial glial cells. To investigate this hypothesis, we analyzed the expression of radial glial cell markers and transcription factors in the mouse embryonic spinal cord. We show that radial glial cells indeed express domain-specific transcription factor. Moreover, they varied in expression of the astrocyte-specific glutamate transporter. The region where the astrocyte-specific glutamate transporter is strongly expressed in the ventral radial glial cells is closely related to the Pax6-expressing domain, and the weakly expressing region corresponding to the Nkx2.2-expressing domain. Furthermore, dorsal radial fibers expressed ephrin-B1. Thus, different types of radial glial cells exist in different domains defined by the transcription factor expression at E12.5. We also show that this diversity continues to the gliogenic stage of radial glial cells. This raises the idea that astrocytes generated from different domains along the dorsoventral axis in the mouse spinal cord have distinct characteristics.
Matrix Metalloproteinases and Their Inhibitors in the Developing Mouse Brain and Spinal Cord: A Reverse Transcription Quantitative Polymerase Chain Reaction Study
Authors: Ulrich Reiner , Gerhauser Ingo , Seeliger Frank , Baumgärtner Wolfgang , Alldinger Susanne
Published: November 2005

Matrix metalloproteinases (MMPs) and their inhibitors (TIMPs) are essential for coordinated extracellular matrix turnover during central nervous system development. Reverse transcription quantitative polymerase chain reaction was employed to evaluate the mRNA expression of MMP-2, -3, -7, -9, -10, -11, -12, -13, -14, -15, and -24, and TIMP-1, -2, -3, and -4 in the prosencephalon, rhombencephalon, and spinal cord of 1- to 40-week-old mice. The molecular data were interpreted in the context of morphological observations. Significantly higher expression levels of MMP-2, -11, -13, -14, -15, and -24, and TIMP-1 and -3 were found in the brain and spinal cord 1 week after birth compared to later time points, while MMP-9 and TIMP-2 upregulation was restricted to the brain. This upregulation coincided with the maximal extension of the transient cerebellar external granular layer, a marker of neuronal progenitor proliferation and migration. MMP-12 was significantly upregulated at later time points and found to be positively correlated with myelination in the rhombencephalon and spinal cord. MMP-3, -7, and -10 mRNA expressions remained unchanged or were negligible. In summary, while most of the MMPs and TIMPs studied seem to be involved in cell proliferation and migration, MMP-12 might be decisive for myelination.
Risk Factors for Primary Intracerebral Hemorrhage
Authors: Zia Elisabet , Pessah-Rasmussen Hélène , Khan Farhad Ali , Norrving Bo , Janzon Lars , Berglund Göran , Engström Gunnar
Published: November 2005

Purpose: In this population-based study, risk factors for primary intracerebral hemorrhage (PICH) and PICH subtypes were explored in a nested case-control design. Method: Risk factors were determined in 22,444 men and 10,902 women (mean age 47 years) who participated in a health-screening programme between 1974 and 1991. 147 subjects with CT or autopsy-verified first-ever PICH during the follow-up period (mean 14 years) were compared with 1,029 stroke-free controls, matched for age, sex and screening-year. Results: As compared to controls, PICH cases had significantly higher blood pres- sure (135/91 vs. 127/85 mm Hg), triglycerides (1.7 vs. 1.4 mmol/l), BMI (25.5 vs. 24.8) and shorter stature (1.73 vs. 1.74 m). Diabetes (6.9 vs. 2.8 %) and history of psychiatric morbidity (19.7 vs. 11.0 %) were more common in PICH cases and more of them were living alone (35.4 vs. 25.5%). After adjustment in a backward logistic regression model, high systolic blood pressure, diabetes, high triglycerides, short stature and psychiatric morbidity remained significantly associated with PICH. As compared to the control group, high systolic blood pressure was significantly associated both with nonlobar and lobar PICH. Diabetes and psychiatric morbidity were associated with nonlobar PICH. Smoking doubled the risk for lobar PICH, but was unrelated to nonlobar PICH. Conclusion: In this prospective population-based study, hypertension, diabetes, height, triglycerides and psychiatric morbidity were risk factors for PICH. Smoking was a risk factor for lobar PICH only.
Nucleosomes in Serum of Patients with Early Cerebral Stroke
Authors: Geiger Sandra , Holdenrieder Stefan , Stieber Petra , Hamann Gerhard F. , Bruening Roland , Ma Jun , Nagel Dorothea , Seidel Dietrich
Published: November 2005

Background: Nucleosomes are cell death products that are elevated in serum of patients with diseases that are associated with massive cell destruction. We investigated the kinetics of circulating nucleosomes after cerebral stroke and their correlation with the clinical status. Methods: In total, we analyzed nucleosomes by ELISA in sera of 63 patients with early stroke daily during the first week after onset. For correlation with the clinical pathology, patients were grouped into those with medium to slight functional impairment (Barthel Index BI ≧50) and those with severe functional impairment (BI <50). Results: Patients with BI ≧50 showed a continuous increase in nucleosomes until day 5 (median: 523 arbitrary units, AU) followed by a slow decline. In contrast, patients with BI <50 showed a steeper initial increase reaching a maximum already on day 3 (869 AU). Both, days after stroke (p < 0.001) and BI (p < 0.001), had a significant influence on nucleosome concentrations, respectively. Consistently, patients with BI <50 had a significantly larger area under the curve (AUC/day) of nucleosome values during the first week after stroke (800 AU) than patients with BI ≧50 (497 AU; p = 0.031). Concerning the infarction volume, nucleosomes showed significant correlations for the concentrations on day 3 (r = 0.43; p = 0.001) and for the area under the curve (r = 0.34; p = 0.016). Conclusion: Even if nucleosomes are nonspecific cell death markers, their release into serum after cerebral stroke correlates with the gross functional status as well as with the infarction volume and can be considered as biochemical correlative to the severity of stroke.
The Effect of Tiotropium on Hyperinflation and Exercise Capacity in Chronic Obstructive Pulmonary Disease
Authors: Verkindre C. , Bart F. , Aguilaniu B. , Fortin F. , Guérin J.-C. , Le Merre C. , Iacono P. , Huchon G.
Published: November 2005

Background: Chronic obstructive pulmonary disease (COPD) is characterized by airflow limitation, which results in the progressive development of dyspnea and exercise limitation. Objective and Methods: To compare the effect of tiotropium with placebo on forced vital capacity (FVC) in patients with moderate-to-severe COPD and lung hyperinflation, using exercise endurance, dyspnea and health-related quality of life (HRQoL) as secondary endpoints. One hundred patients were randomized to receive either tiotropium 18 µg once daily or placebo for 12 weeks. Results: Trough (predose) FVC was significantly improved with tiotropium compared to placebo on day 42 (0.27 ± 0.08 liters) and 84 (0.20 ± 0.08 liters; p < 0.05 for both). Trough inspiratory capacity (IC) was also significantly improved with tiotropium compared to placebo on day 42 (0.16 ± 0.07 liters) and 84 (0.15 ± 0.07 liters; p < 0.05 for both). Tiotropium increased the mean distance walked during the shuttle walking test by 33 ± 12 (day 42) and 36 ± 14 m (day 84) compared to placebo (p < 0.05 for both). On day 84, 59% of the patients in the tiotropium group and 35% of the patients in the placebo group had significant and clinically meaningful improvements in the St. George’s Respiratory Questionnaire total score (p < 0.05). Numerical decreases in the focal score in the Transition Dyspnea Index in patients receiving tiotropium versus placebo suggest that tiotropium also improved dyspnea during activities of daily living. Conclusion: Tiotropium 18 µg once daily reduced hyperinflation with consequent improvements in walking distance and HRQoL in patients with COPD and lung hyperinflation.
Plasma Lipoproteins and Apolipoproteins as Predictors of Cardiovascular Risk and Treatment Benefit in the PROspective Study of Pravastatin in the Elderly at Risk (PROSPER)
Authors: Packard Chris J. , Ford Ian , Robertson Michele , Shepherd James , Blauw Gerard J. , Murphy Michael B. , Bollen Edward L.E.M. , Buckley Brendan M. , Cobbe Stuart M. , Gaw Allan , Hyland Michael , Jukema J. Wouter , Kamper Adriaan M. , Macfarlane Peter W. , Perry Ivan J. , Stott David J. , Sweeney Brian J. , Twomey Cillian , Westendorp Rudi G.J.
Published: November 2005

Background—

Statins are important in vascular disease prevention in the elderly. However, the best method of selecting older patients for treatment is uncertain. We assessed the role of plasma lipoproteins as predictors of risk and of treatment benefit in the PROspective Study of Pravastatin in the Elderly at Risk (PROSPER).

Method and Results—

The association of LDLc and HDLc with risk was examined in the 5804 70- to 82-year-old subjects of PROSPER. Baseline LDLc showed no relation to risk of the primary end point in the placebo group (
P
=0.27), nor did on-treatment LDLc in the pravastatin group (
P
=0.12). HDLc was inversely associated with risk in subjects on placebo (
P
=0.0019) but not in those on pravastatin (
P
=0.24). Risk reduction on pravastatin treatment was unrelated to baseline LDLc (
P
=0.38) but exhibited a significant interaction with HDLc (
P
=0.012). Subjects in the lowest 2 quintiles of HDLc (<1.15 mmol/L) had a risk reduction of 33% (hazard ratio, 0.67; 95% confidence limits, 0.55, 0.81;
P
<0.0001), whereas those with higher HDLc showed no benefit (RR, 1.06; 95% confidence limits, 0.88, 1.27;
P
=0.53). During follow-up, there was no relation between achieved level of LDLc or HDLc and risk. However, the change in the LDLc/HDLc ratio on statin treatment appeared to account for the effects of therapy.

Conclusions—

In people >70 years old, HDLc appears to be a key predictor of risk and of treatment benefit. Findings in PROSPER suggest that statin therapy could usefully be targeted to those with HDLc <1.15 mmol/L or an LDLc/HDLc ratio >3.3.