bluuebunny/crossref_metadata_2025 huggingface dataset:
Travellers in Britain: a minority and the state
Authors: Taylor Becky
Published: October 2004

This article explores the developing relations between Travellers and the British state in the context of the expansion of welfare provision. Using four case studies it highlights the key characteristics of Traveller-state relations: the lack of a unified response to Travellers by the state; how Travellers were simultaneously seen as an important target for welfare provision and less entitled to its benefits; and that settlement and assimilation were the motivating factors for schemes. It goes on to show that these trends were the result of three factors: the dominance of stereotypes surrounding Travellers; the structure of the state; and the agency of Travellers themselves.
Secondary effects induced by the colon carcinogen azoxymethane in BDIX rats
Authors: KOBÆK‐LARSEN MORTEN , FENGER CLAUS , RITSKES‐HOITINGA JELMERA
Published: October 2004

Azoxymethane (AOM) is claimed to be a colon‐specific carcinogen. In our studies, AOM was administered to adult BDIX/OrlIco rats by four weekly subcutaneous injections of 15 mg/kg body weight each – two periods of 2 weeks of AOM treatment separated by a one‐week break. This treatment schedule resulted in colon carcinomas with a high frequency (75–100%) and with a high reproducibility. However, some serious side effects are associated with this carcinogen treatment. In addition to the colorectal tumours, we found small intestinal tumours, hepatic lesions and a high frequency of mesenchymal renal tumours which increased with longer latency periods. The renal tumours were only found in female rats, and this indicates a possible relation to sex hormones. We therefore analyzed both male and female kidneys for the expression of estrogen and progesterone receptors by immunohistochemical methods. A positive nuclear reaction for estrogen receptor was present in most tumour cells in all tumours and occasionally in nuclei of entrapped tubular cells, but never in glomeruli. Normal appearing renal tissue from female rats showed no positive reaction, but in male rats a slight nuclear reaction was seen in tubuli in the peripheral part of the medulla. A similar pattern was seen for progesterone receptors, but less pronounced. No rats developed tumours in the external ear canal, which is in contrast to studies performed in other rat strains. This may therefore be strain related. In order to reduce the secondary effects of the induction of colon cancer by AOM, it is advisable to use male rats only and a maximum latency period of 32 weeks.
Identification of Bartonella species in rodents, shrews and cats in Denmark: detection of two B. henselae variants, one in cats and the other in the long‐tailed field mouse
Authors: ENGBÆK KRÆSTEN , LAWSON PAUL A.
Published: October 2004

Small mammals and stray cats were trapped in two areas of North Zealand, Denmark, and their blood cultured for hemotrophic bacteria. Bacterial isolates were recovered in pure culture and subjected to 16S rDNA gene sequencing. Bartonella species were isolated from five mammalian species: B. grahamii from Microtus agrestis (field vole) and Apodemus flavicollis (yellow‐necked field mouse); B. taylorii from M. agrestis, A. flavicollis and A. sylvaticus (long‐tailed field mouse); B. tribocorum from A. flavicollis; B. vinsonii subsp. vinsonii from M. agrestis and A. sylvaticus; and B. birtlesii from Sorex vulgaris (common shrew). In addition, two variant types of B. henselae were identified: variant I was recovered from three specimens of A. sylvaticus, and B. henselae variant II from 11 cats; in each case this was the only B. henselae variant found. No Bartonella species was isolated from Clethrionomys glareolus (bank vole) or Micromys minutus (harvest mouse). These results suggest that B. henselae occurs in two animal reservoirs in this region, one of variant I in A. sylvaticus, which may be transmitted between mice by the tick Ixodes ricinus, and another of variant II in cats, which may be transmitted by the cat flea (Ctenocephalides felis). To our knowledge, this is the first report of the occurrence of B. henselae and B. tribocorum in Apodemus mice.
The expression and activity of renal nitric oxide synthase and circulating nitric oxide in polycystic kidney disease rats
Authors: WANG DAN , BRAENDSTRUP OTTO , LARSEN SVEND , HORN THOMAS , STRANDGAARD SVEND
Published: October 2004

Nitric oxide (NO) influences tubular fluid and electrolyte transport, and hence possibly also fluid accumulation in renal cysts. The expression and activity of intrarenal constitutive NO synthase (cNOS) [neuronal NOS, nNOS and endothelial NOS, eNOS] and inducible NOS (iNOS) and plasma nitrite/nitrate (PNOx) concentration were assessed in homozygous Han:SPRD polycystic kidney disease (PKD) rats (cy/cy), heterozygous Han:SPRD PKD rats (cy/+), homozygous normal Han:SPRD littermates (+/+) and Sprague Dawley rats (sd). The results showed: 1) nNOS expression was decreased in proximal tubules and thick ascending limbs of the loop of Henle in cy/cy and cy/+ rats compared to +/+ and sd rats (p<0.05). nNOS was weakly expressed in the epithelium of small cysts and unexpressed in epithelium of large cysts. 2) iNOS expression was increased in proximal tubular epithelial cells in cy/+ rats compared to +/+ rats and sd rats (p<0.01). iNOS expression in cyst epithelium was decreased in cy/+ rats (p<0.05) and absent in cy/cy rats. 3) eNOS expression was similar in the endothelium of intrarenal arteries in all groups. 4) The activity of renal cNOS was decreased in cy/cy and cy/+ rats; the activity of iNOS was decreased only in cy/cy rats, with no significant difference among the other three groups. 5) PNOx concentration was higher in cy/cy rats than in the other three groups, and correlated positively with plasma creatinine and urea. In conclusion, NOS expression and activity decreased as cysts developed, suggesting that NO downregulation is involved in the pathogenesis of PKD.
Predicting Change Propagation in Complex Design
Authors: Clarkson P. John , Simons Caroline , Eckert Claudia
Published: October 2004

In redesign and design for customization, products are changed. During this process a change to one part of the product will, in most cases, result in changes to other parts. The prediction of such change provides a significant challenge in the management of redesign and customization of complex products where many change propagation paths may be possible. This paper reports on an analysis of change behavior based on a case study in Westland Helicopters of rotorcraft design; the development of mathematical models to predict the risk of change propagation in terms of likelihood and impact of change; and the development of a prototype computer support tool to calculate such information for a specific product. With knowledge of likely change propagation paths and their impact on the delivery of the product, design effort can be directed towards avoiding change to “expensive” sub-systems and, where possible, allowing change where it is easier to implement while still achieving the overall changes required.
Five Precision Point Synthesis of Spatial RRR Manipulators Using Interval Analysis
Authors: Lee Eric , Mavroidis Constantinos , Merlet Jean Pierre
Published: October 2004

In this paper, the geometric design problem of serial-link robot manipulators with three revolute (R) joints is solved for the first time using an interval analysis method. In this problem, five spatial positions and orientations are defined and the dimensions of the geometric parameters of the 3-R manipulator are computed so that the manipulator will be able to place its end-effector at these pre-specified locations. Denavit and Hartenberg parameters and 4×4 homogeneous matrices are used to formulate the problem and obtain the design equations and an interval method is used to search for design solutions within a predetermined domain.
Omni-Directional Mobility Using Active Split Offset Castors
Authors: Yu Haoyong , Spenko Matthew , Dubowsky Steven
Published: October 2004

An omni-directional mobility platform design concept using two active split offset castors (ASOC) and one or more conventional castors is presented. An ASOC module consists of two coaxial conventional wheels driven independently and connected to the platform via an offset link. The kinematics and implementation of the omni-directional platform is described and analyzed. Particular attention is paid to the system performance on uneven floors. The fundamental mechanics of the ASOC wheel scrubbing, which is critical to system wear and energy use, is analyzed and compared to conventional active castor designs. The effectiveness of the design is shown experimentally using an intelligent mobility aid for the elderly.
The Composition of Bennett’s Hyperboloids From the Loop Itself
Authors: Baker J. Eddie
Published: October 2004

Despite the tidiness with which the Bennett linkage can be related geometrically to its associated quadric surfaces, the corresponding algebraic determinations have generally turned out to be cumbersome, and so practically noninvertible. In particular, although earlier work has delineated the linkage in terms of parameters peculiar to its quadric surfaces, the inverse dependences could not be given. We here use the loop strictly as a basis for derivation of the surfaces and employ cartesian co-ordinates throughout, thereby effectively completing the conversion process.
Local Metrics for Rigid Body Displacements
Authors: Eberharter Johannes K. , Ravani Bahram
Published: October 2004

One hundred years ago, Eduard Study introduced a very elegant method to describe a rigid body displacement in three-space. He mapped each position of a rigid body onto a point on a quadric, now called the Study quadric. This quadric is a six-dimensional rational hyper-surface, embedded in a seven-dimensional projective real space, called Study’s soma space. More than half a century later Ravani and Roth reconfigured Study’s soma space into a three-dimensional dual projective space, and defined a geometric metric for rigid body displacements. Here, approximately 20 years later, we again use Study’s quadric and define a new metric for rigid body displacements based on an optimized local mapping of the quadric. The local mappings of the quadric are achieved using stereographic projections, resulting in an affine space where the Euclidean definition of a metric can be used for rigid body displacements and techniques from design of curves and surfaces can be directly utilized for motion design. The results are illustrated by examples.
A DBB-Based Kinematic Calibration Method for In-Parallel Actuated Mechanisms Using a Fourier Series
Authors: Takeda Yukio , Shen Gang , Funabashi Hiroaki
Published: October 2004

For kinematic calibration of robots, we proposed using a low order Fourier series obtained by transforming the data for circular measurement paths. The errors of the realized paths were measured using a Double-Ball-Bar (DBB) system. Two nondimensional indices were proposed for evaluating the orthogonalities of the measurement paths and calibration parameters. An index was also proposed to evaluate the accuracy of the calibration with regard to measurement error. An algorithm for determining adequate measurement paths and an optimal set of a specified number of paths using these indices was also proposed. The effectiveness of the proposed method, indices, and algorithm was investigated through simulations and experiments with an experimental 6 dof in-parallel actuated worktable that we developed.
Ciliary Photoreceptors with a Vertebrate-Type Opsin in an Invertebrate Brain
Authors: Arendt Detlev , Tessmar-Raible Kristin , Snyman Heidi , Dorresteijn Adriaan W. , Wittbrodt Joachim
Published: October 2004

For vision, insect and vertebrate eyes use rhabdomeric and ciliary photoreceptor cells, respectively. These cells show distinct architecture and transduce the light signal by different phototransductory cascades. In the marine rag-worm
Platynereis
, we find both cell types: rhabdomeric photoreceptor cells in the eyes and ciliary photoreceptor cells in the brain. The latter use a photopigment closely related to vertebrate rod and cone opsins. Comparative analysis indicates that both types of photoreceptors, with distinct opsins, coexisted in Urbilateria, the last common ancestor of insects and vertebrates, and sheds new light on vertebrate eye evolution.
A PINOID-Dependent Binary Switch in Apical-Basal PIN Polar Targeting Directs Auxin Efflux
Authors: Friml Jiří , Yang Xiong , Michniewicz Marta , Weijers Dolf , Quint Ab , Tietz Olaf , Benjamins René , Ouwerkerk Pieter B. F. , Ljung Karin , Sandberg Göran , Hooykaas Paul J. J. , Palme Klaus , Offringa Remko
Published: October 2004

Polar transport–dependent local accumulation of auxin provides positional cues for multiple plant patterning processes. This directional auxin flow depends on the polar subcellular localization of the PIN auxin efflux regulators. Overexpression of the PINOID protein kinase induces a basal-to-apical shift in PIN localization, resulting in the loss of auxin gradients and strong defects in embryo and seedling roots. Conversely,
pid
loss of function induces an apical-to-basal shift in PIN1 polar targeting at the inflorescence apex, accompanied by defective organogenesis. Our results show that a PINOID-dependent binary switch controls PIN polarity and mediates changes in auxin flow to create local gradients for patterning processes.
Staphylococcus aureus
AgrA Binding to the RNAIII-
agr
Regulatory Region
Authors: Koenig Robbin L. , Ray Jessica L. , Maleki Soheila J. , Smeltzer Mark S. , Hurlburt Barry K.
Published: October 2004

The control of virulence gene expression in the human pathogen
Staphylococcus aureus
is under the partial control of the two-component quorum-sensing system encoded by genes of the
agr
locus. The product of the
agrA
gene has been shown by amino acid sequence similarity to be the putative response regulator; however, binding of AgrA to promoters under its control has not yet been demonstrated. In this study, we isolated and purified soluble AgrA by expression under osmotic shock conditions and ion-exchange chromatography. Purified AgrA showed high-affinity binding to the RNAIII-
agr
intergenic region by electrophoretic mobility shift assays. Binding was localized by DNase I protection assays to a pair of direct repeats in the P2 and P3 promoter regions of the
agr
locus. We found that this binding was enhanced by the addition of the small phosphoryl donor, acetyl phosphate. The difference in binding affinity between these two promoters was found to result from a 2-bp difference between the downstream direct repeats of the P2 and P3 sites. Mutation of these base pairs in the P3 site to match those found in the P2 site increased the affinity of AgrA for the P3 site relative to that for the P2 site. These results are consistent with the function of AgrA as a response regulator with recognition sites in the promoter regions of RNAIII and the
agr
locus.
MucA-Mediated Coordination of Type III Secretion and Alginate Synthesis in
Pseudomonas aeruginosa
Authors: Wu Weihui , Badrane Hassan , Arora Shiwani , Baker Henry V. , Jin Shouguang
Published: October 2004

The type III secretion system (T3SS) of
Pseudomonas aeruginosa
is an important virulence factor. The T3SS of
P. aeruginosa
can be induced by a low calcium signal or upon direct contact with the host cells. The exact pathway of signal sensing and T3SS activation is not clear. By screening a transposon insertion mutant library of the PAK strain, mutation in the
mucA
gene was found to cause repression of T3SS expression under both type III-inducing and -noninducing conditions. Mutation in the
mucA
gene is known to cause alginate overproduction, resulting in a mucoid phenotype. Alginate production responds to various environmental stresses and plays a protective role for
P. aeruginosa
. Comparison of global gene expression of
mucA
mutant and wild-type PAK under T3SS-inducing conditions confirmed the down regulation of T3SS genes and up regulation of genes involved in alginate biosynthesis. Further analysis indicated that the repression of T3SS in the
mucA
mutant was AlgU and AlgR dependent, as double mutants
mucA/algU
and
mucA/algR
showed normal type III expression. An
algR
::
Gm
mutant showed a higher level of type III expression, while overexpression of the
algR
gene inhibited type III gene expression; thus, it seems that the AlgR-regulated product inhibits the expression of the T3SS genes. It is likely that
P. aeruginosa
has evolved tight regulatory networks to turn off the energy-expensive T3SS when striving for survival under environmental stresses.
The Operator and Early Promoter Region of the Shiga Toxin Type 2-Encoding Bacteriophage 933W and Control of Toxin Expression
Authors: Tyler Jessica S. , Mills Melissa J. , Friedman David I.
Published: October 2004

The genes encoding Shiga toxin (Stx), the major virulence factor of Shiga toxin-producing
Escherichia coli
, are carried in the genomes of bacteriophages that belong to the lambdoid family of phages. Previous studies demonstrated that induction of prophages encoding
stx
significantly enhances the production and/or release of Stx from the bacterium. Therefore, factors that regulate the switch between lysogeny and lytic growth, e.g., repressor, operator sites, and associated phage promoters, play important roles in regulating the production and/or release of Stx. We report the results of genetic and biochemical studies characterizing these elements of the Stx-encoding bacteriophage 933W. Like λ, 933W has three operator repeats in the right operator region (
O
R
), but unlike λ and all other studied lambdoid phages, which have three operator repeats in the left operator region (
O
L
), 933W only has two operator repeats in
O
L
. As was observed with λ, the 933W
O
R
and
O
L
regions regulate transcription from the early
P
R
and
P
L
promoters, respectively. A lysogen carrying a 933W derivative encoding a noncleavable repressor fails to produce Stx, unlike a lysogen carrying a 933W derivative encoding a cleavable repressor. This finding provides direct evidence that measurable expression of the
stx
genes encoded by a 933W prophage requires induction of that prophage with the concomitant initiation of phage gene expression.
SCHEDULING OF THE DAG ASSOCIATED WITH PIPELINE INVERSION OF TRIANGULAR MATRICES
Authors: DJAMEGNI CLEMENTIN TAYOU , TCHUENTE MAURICE
Published: October 2004

We are interested in methods which compute the inverse of a triangular matrix A of order n by solving the n linear systems Ax=ei, i=1,…, n, where ei is the i-th element of the canonical basis of Rn. More precisely, we consider the dependence graph associated with algorithms where the entries of matrix A are read only once and used in pipeline for the solution of these systems. We exhibit a new scheduling which induces an algorithm with time complexity T*=2n−1. The number n2/8+O(n) of processors required by this scheduling improves the best previously known bound n2/6+O(n), and is quite close to the lower bound n2/8.5+O(n).
A PARALLEL SCHEDULING ALGORITHM FOR TREE STRUCTURED INTERCONNECTION NETWORKS
Authors: WU MIN-YOU
Published: October 2004

Global parallel scheduling is a new approach for runtime load balancing. In parallel scheduling, all processors cooperate together to schedule work. Parallel scheduling accurately balances the load by using global load information. As an alternative strategy to the commonly used dynamic scheduling, it provides a high-quality, low-overhead load balancing. This paper presents a parallel scheduling algorithm for interconnection networks of the tree topology. This algorithm minimizes communications and maximize locality.
FAULT TOLERANT ROUTING IN HYPERCUBES AND STAR GRAPHS
Authors: GU QIAN-PING , PENG SHIETUNG
Published: October 2004

In this paper, we give two linear time algorithms for node-to-node fault tolerant routing problem in n-dimensional hypercubes Hn and star graphs Gn. The first algorithm, given at most n−1 arbitrary fault nodes and two non-fault nodes s and t in Hn, finds a fault-free path s→t of length at most [Formula: see text] in O(n) time, where d(s, t) is the distance between s and t. Our second algorithm, given at most n−2 fault nodes and two non-fault nodes s and t in Gn, finds a fault-free path s→t of length at most d(Gn)+3 in O(n) time, where [Formula: see text] is the diameter of Gn. When the time efficiency of finding the routing path is more important than the length of the path, the algorithms in this paper are better than the previous ones.
AN OPTIMAL RANDOMIZED PARALLEL ALGORITHM FOR THE SINGLE FUNCTION COARSEST PARTITION PROBLEM
Authors: JÁJÁ JOSEPH , RYU KWAN WOO
Published: October 2004

We describe a randomized parallel algorithm to solve the single function coarsest partition problem. The algorithm runs in O( log n) time using O(n) operations with high probability on the Priority CRCW PRAM. The previous best known algorithms run in O( log 2 n) time using O(n log 2 n) operations on the CREW PRAM and O( log n) time using O(n log log n) operations on the Arbitrary CRCW PRAM. The technique presented can be used to generate the Euler tour of a rooted tree optimally from the parent representation.
AN Ω(log n−k log k) TIME LINEAR COST LOWER BOUND FOR THE k FUNCTIONS COARSEST PARTITION PROBLEM
Authors: GALLEY CLIVE N.
Published: October 2004

We consider the k functions coarsest partition problem for a set S, where |S|=n, and k functions from S to S. We present an Ω(log n−k log k) time, linear work, lower bound for this problem on the CRCW PRAM model of computation.
ON THE PARALLEL COMPLEXITY OF ACYCLIC LOGIC PROGRAMS
Authors: CHAUDHURI SHIVA , DIMOPOULOS YANNIS , ZAROLIAGIS CHRISTOS D.
Published: October 2004

In this paper we investigate the parallel complexity of computing the stable model of acyclic general logic programs. Within this class of logic programs, we consider the cases of negative and definite logic programs. Both cases are proved to be [Formula: see text]-complete. We prove the same for a related problem, namely that of computing the kernel of a directed acyclic graph.
BOUNDED TIMESTAMPS IN PROCESS NETWORKS
Authors: SINGH AMBUJ K.
Published: October 2004

Timestamps have been used for designing and analyzing a number of algorithms in distributed systems. The reusability of timestamps is investigated in the setting of a message-passing system and a simple implementation is presented for bounded timestamps.
PARALLELISM VIA HOMOMORPHISMS
Authors: GRANT-DUFF ZULLY N. , HARRISON PETER G.
Published: October 2004

A methodology for the identification of homomorphisms in high level functional language specifications is presented and their role illustrated with a series of examples. These include the synthesis of a fractal-based algorithm for image decompression and a logarithmic parallel simulation of a single server, first-come-first-served queue.
OPTIMAL PARALLEL SUPERPRIMITIVITY TESTING FOR SQUARE ARRAYS
Authors: ILIOPOULOS COSTAS S. , KORDA MAUREEN
Published: October 2004

We present an optimal O( log log n) time algorithm on the CRCW PRAM which tests whether a square array, A, of size n×n, is superprimitive. If A is not superprimitive, the algorithm returns the quasiperiod, i.e., the smallest square array that covers A.
PARALLEL EDGE COLORING APPROXIMATION
Authors: FÜRER MARTIN , RAGHAVACHARI BALAJI
Published: October 2004

Let G be a graph with n vertices and m edges and let its maximum degree be Δ. It is shown that a valid edge coloring of G using at most 2Δ−1 colors can be computed in O( log n log Δ) time using O(m+n) processors on a CREW PRAM. Based on this, for any constant c>1, a valid edge coloring for G using at most max([cΔ], Δ+1) colors can be computed in O( log 2 n) time, using O(m+n) processors. Employing different techniques, we show that it is possible to compute a Δ2 coloring in O( log * n) time, with O(m+n) processors. Also, a maximal matching of G can be computed in O( log 2 n log Δ) time using O(m+n) processors on a CREW PRAM.
AN OPTIMAL PARALLEL ALGORITHM TO COLOR AN INTERVAL GRAPH
Authors: PAL MADHUMANGAL , BHATTACHARJEE G.P.
Published: October 2004

An optimal parallel algorithm is presented for coloring an interval graph using minimum number of colors. The proposed parallel algorithm takes [Formula: see text] time with P processors on an EREW PRAM.
COMMUNICATION PIPELINING IN HYPERCUBES
Authors: CERIO LUIS DÍAZ DE , GONZÁLEZ ANTONIO , VALERO-GARCÍA MIGUEL
Published: October 2004

Many parallel algorithms exhibit a hypercube communication topology. Such algorithms can easily be executed on a multicomputer with a hypercube interconnection topology. However, in most cases these parallel algorithms only make use of a small fraction of the interconnection bandwidth offered by the multicomputer. In particular, each processor of a hypercube multicomputer is connected to d different neighbors by d different links. Nevertheless, hypercube algorithms usually do not use more than one of these d links at the same time. This paper presents a technique called communication pipelining that enables a more efficient use of the interconnection network and, in consequence, a significant reduction in the execution time. This technique is based on a transformation of the original algorithm. The resulting equivalent algorithm makes use of several links of each node simultaneously. Given a particular problem and a particular architecture. the degree of pipelining to be applied is a design parameter that must be decided when transforming the original algorithm. The paper presents analytical models that allow for an optimal choice of the degree of pipelining for each problem and a given architecture. To illustrate the performance of the communication pipelining technique, its application to the FFT computation is presented as an example. It is shown that an optimal choice of the degree of pipelining can achieve a reduction by a factor of d in the communication overhead of the algorithm.
ON THE SPACE-TIME MAPPING OF A CLASS OF DIVIDE-AND-CONQUER RECURSIONS
Authors: HERRMANN CHRISTOPH , LENGAUER CHRISTIAN
Published: October 2004

We propose a functional program skeleton for balanced fixed-degree divide-and-conquer and a method for its parallel implementation on message-passing multiprocessors. In the method, the operations of the skeleton are first mapped to a geometric computational model which is then mapped to space-time in order to expose the inherent parallelism. This approach is inspired by the method of parallelizing nested loops in the polytope model.
A PROCESSOR-TIME-MINIMAL DESIGN FOR 3D RECTILINEAR MESH ALGORITHMS
Authors: SCHEIMAN CHRIS , CAPPELLO PETER
Published: October 2004

The paper, using a directed acyclic graph (dag) model of algorithms, investigates precedence constrained multiprocessor schedules for the nx×ny×nz directed rectilinear mesh. Its completion requires at least nx+ny+nz−2 multiprocessor steps. Time-minimal multiprocessor schedules that use as few processors as possible are called processor-time-minimal. Lower bounds are shown for the nx×ny×nz directed mesh, and these bounds are shown to be exact by constructing a processor-time-minimal multiprocessor schedule that can be realized on a systolic array whose topology is either a two dimensional mesh or skewed cylinder.
OPTIMAL AGE-DEPENDENT PREVENTIVE MAINTENANCE POLICIES WITH IMPERFECT MAINTENANCE
Authors: WANG HONGZHOU , PHAM HOANG
Published: October 2004

This paper proposes three age-dependent preventive maintenance models with imperfect repair and/or imperfect preventive maintenance (pm). In these models imperfect repair is treated in a way that after repair the lifetime of a unit will decrease to a fraction of its immediately previous one and its repair time will increase to a multiple of immediately previous one. In this paper, the expected maintenance cost rate and asymptotic average availability are derived with a consideration that the maintenance and repair times are not negligible. The optimum maintenance policies are then determined for the three imperfect maintenance models respectively. A class of related optimization problems is also discussed. Finally, a numerical example is presented to illustrate the results.
FAILURE MECHANISMS AND LIFE MODELS
Authors: RAUSAND MARVIN , REINERTSEN RUNE
Published: October 2004

This paper discusses stochastic models for the lifelength of non-repairable items under the influence of dominant failure mechanisms like fatigue, corrosion and wear. The Weibull, the lognormal, the inverse Gaussian, and the Birnbaum-Saunders distributions are discussed and compared. Model selection problems based on both field performance data and laboratory data are focused. The consequences of choosing a wrong life model are highlighted. It is concluded that model selection must be based on a thorough knowledge of actual failure mechanisms, and the associated time dependent deterioration. Current knowledge on the relation between some dominant failure mechanisms and the associated life distributions is presented.
ApoE-mediated cholesterol efflux from macrophages: separation of autocrine and paracrine effects
Authors: Dove Dwayne E. , Linton MacRae F. , Fazio Sergio
Published: October 2004

Macrophages in the vessel wall secrete high levels of apolipoprotein E (apoE). Cholesterol efflux from macrophages to apoE has been shown to decrease foam cell formation and prevent atherosclerosis. An apoE molecule can mediate cholesterol efflux from the macrophage that originally secreted it (autocrine effect) or from surrounding macrophages (paracrine effect). Traditional methodologies have not been able to separate these serial effects. The novel methodology presented here was developed to separate autocrine and paracrine effects by using a simple mathematical model to interpret the effects of dilution on apoE-mediated cholesterol efflux. Our results show that, at very dilute concentrations, the paracrine effect of apoE is not evident and the autocrine effect becomes the dominant mediator of efflux. However, at saturating concentrations, paracrine apoE causes 80–90% of the apoE-mediated cholesterol efflux, whereas autocrine apoE is responsible for the remaining 10–20%. These results suggest that the relative importance of autocrine and paracrine apoE depends on the size of the local distribution volume, a factor not considered in previous in vitro studies of apoE function. Furthermore, autocrine effects of apoE could be critical in the prevention of foam cell formation in vivo. This novel methodology may be applicable to other types of mixed autocrine/paracrine systems, such as signal transduction systems.
MAPK signaling regulates endothelial cell assembly into networks and expression of MT1-MMP and MMP-2
Authors: Boyd Pamela J. , Doyle Jennifer , Gee Eric , Pallan Shelley , Haas Tara L.
Published: October 2004

Microvascular endothelial cells embedded within three-dimensional (3D) type I collagen matrixes assemble into cellular networks, a process that requires the upregulation of membrane type 1 (MT1) matrix metalloproteinase (MMP) and MMP-2. The purpose of this study was to identify the signaling pathways responsible for the transcriptional activation of MT1-MMP and MMP-2 in endothelial cells in 3D collagen lattices. We hypothesized that the 3D type I collagen induction of MT1-MMP and MMP-2 is mediated by the mitogen-activated protein kinase family of enzymes. Here, we show that 3D type I collagen elicits a persistent increase in ERK1/2 and JNK activation and a decrease in p38 activation. Inhibition of ERK1/2 or JNK disrupted endothelial network formation in 3D type I collagen lattices, whereas inhibition of p38 promoted network formation. mRNA levels of both MT1-MMP and MMP-2 were attenuated by ERK1/2 inhibition but unaffected by either JNK or p38 inhibition. By contrast, expression of constitutively active MEK was sufficient to stimulate MMP-2 production in a monolayer of endothelial cells cultured on type I collagen. These results provide evidence that signaling through both ERK1/2 and JNK regulates endothelial assembly into cellular networks but that the ERK1/2 signaling cascade specifically regulates network formation and the production of both MT1-MMP and MMP-2 genes in response to 3D type I collagen.
Dietary lipids modify the age-associated changes in intestinal uptake of fructose in rats
Authors: Drozdowski L. , Woudstra T. , Wild G. , Clandinin M. T. , Thomson A. B. R.
Published: October 2004

Because reduced nutrient absorption may contribute to malnourishment in the elderly, age and diet modulate fructose uptake in mice, and alterations in fructose uptake may be paralleled by changes in the abundance of fructose transporters, the objectives of this study were to determine 1) the effects of aging on fructose absorption in rats, 2) the effect of feeding diets enriched with saturated fatty acids (SFA) vs. polyunsaturated fatty acids (PUFA), and 3) the mechanisms of these age-and diet-associated changes. Male Fischer 344 rats aged 1, 9, and 24 mo received isocaloric diets enriched with SFA or PUFA. The uptake of 14C-labeled d-fructose was determined in vitro using the intestinal sheet method. Northern and Western blot analyses and immunohistochemistry were used to determine the abundance of sodium-independent glucose and fructose transporters (GLUT)2 and GLUT5. When expressed on the basis of mucosal surface area, jejunal fructose uptake was increased in 9 and 24 mo compared with 1-mo-old animals fed SFA. PUFA-fed animals demonstrated increased fructose uptake at 24 mo compared with younger animals. Ileal fructose uptake was increased with SFA vs. PUFA in 9-mo-old rats but was reduced with SFA in 1- and 24-mo-old rats. Variations in GLUT2 and GLUT5 abundance did not parallel changes in uptake. These results indicate that 1) age increases fructose uptake when expressed on the basis of mucosal surface area, 2) age influences the adaptive response to dietary lipid modifications, and 3) alterations in fructose uptake are not explained by variations in GLUT2 or GLUT5.
Measurement of myocardial mechanics in mice before and after infarction using multislice displacement-encoded MRI with 3D motion encoding
Authors: Gilson Wesley D. , Yang Zequan , French Brent A. , Epstein Frederick H.
Published: October 2004

Cardiac MRI is an accurate, noninvasive modality for assessing the structure and function of the murine heart. In addition to conventional imaging, MRI tissue tracking methods can quantify numerous aspects of myocardial mechanics, including intramyocardial displacement, strain, twist, and torsion. In the present study, we developed and applied a novel pulse sequence based on displacement-encoded imaging using stimulated echoes (DENSE) that achieves multislice coverage, high spatial resolution, and three-dimensional (3D) displacement encoding. With the use of this technique, myocardial mechanics of C57Bl/6 mice were measured at baseline and 1 day after experimental myocardial infarction. At baseline, the mean systolic transmural circumferential strain was −0.14 ± 0.02 and the mean systolic radial strain was 0.30 ± 0.05. Changes in circumferential and radial strains from the subepicardium to the subendocardium were detected at baseline ( P < 0.05). One day after infarction, significantly reduced 3D displacements and strain were detected in infarcted and noninfarcted myocardium. Infarction also reduced normalized systolic torsion from its baseline value of 1.35 ± 0.27°/mm ( R = 0.99) to 0.07 ± 0.54°/mm ( R = 0.96, P < 0.05). DENSE MRI can assess the 3D myocardial mechanics of the murine heart in <1 h of scan time at 4.7 T and may be applied to studies of myocardial mechanics in genetically engineered mice.
Evolution of a “falx lunatica” in demarcation of critically ischemic myocutaneous tissue
Authors: Harder Yves , Amon Michaela , Georgi Mirko , Banic Andrej , Erni Dominique , Menger Michael D.
Published: October 2004

Using intravital microscopy in a chronic in vivo mouse model, we studied the demarcation of myocutaneous flaps and evaluated microvascular determinants for tissue survival and necrosis. Chronic ischemia resulted in a transition zone, characterized by a red fringe and a distally adjacent white falx, which defined the demarcation by dividing the proximally normal from the distally necrotic tissue. Tissue survival in the red zone was determined by hyperemia, as indicated by recovery of the transiently reduced functional capillary density, and capillary remodeling, including dilation, hyperperfusion, and increased tortuosity. Angiogenesis and neovascularization were not observed over the 10-day observation period. The white rim distal to the red zone, appearing as “falx lunatica,” showed a progressive decrease of functional capillary density similar to that of the necrotic distal area but without desiccation, and thus transparency, of the tissue. Development of the distinct zones of the critically ischemic tissue could be predicted by partial tissue oxygen tension (Pt[Formula: see text]) analysis by the time of flap elevation. The falx lunatica evolved at a Pt[Formula: see text] between 6.2 ± 1.3 and 3.8 ± 0.7 mmHg, whereas tissue necrosis developed at <3.8 ± 0.7 mmHg. Histological analysis within the falx lunatica revealed interstitial edema formation and muscle fiber nuclear rarefaction but an absence of necrosis. We have thus demonstrated that ischemia-induced necrosis does not demarcate sharply from normal tissue but develops beside a fringe of tissue with capillary remodeling an adjacent falx lunatica that survives despite nutritive capillary perfusion failure, probably by direct oxygen diffusion.
Nitric oxide contributes to right coronary vasodilation during systemic hypoxia
Authors: Martinez Rodolfo R. , Setty Srinath , Zong Pu , Tune Johnathan D. , Downey H. Fred
Published: October 2004

As arterial partial pressure of O2 (PaO2) is reduced during systemic hypoxia, right ventricular (RV) work and myocardial O2 consumption (MV̇o2) increase. Mechanisms responsible for maintaining RV O2 demand/supply balance during hypoxia have not been delineated. To address this problem, right coronary (RC) blood flow and RV O2 extraction were measured in nine conscious, instrumented dogs exposed to normobaric hypoxia. Catheters were implanted in the right ventricle for measuring pressure, in the ascending aorta for measuring arterial pressure and for sampling arterial blood, and in an RC vein. A flow transducer was placed around the RC artery. After recovery from surgery, dogs were exposed to hypoxia in a chamber ventilated with N2, and blood samples and hemodynamic data were collected as chamber O2 was reduced progressively to ∼8%. After control measurements were made, the chamber was opened and the dog was allowed to recover. Nω-nitro-l-arginine (l-NNA) was then administered (35 mg/kg, via RV catheter) to inhibit nitric oxide (NO) production, and the hypoxia protocol was repeated. RC blood flow increased during hypoxia due to coronary vasodilation, because RC conductance increased from 0.65 ± 0.05 to 1.32 ± 0.12 ml·min−1·100 g−1. l-NNA blunted the hypoxia-induced increase in RC conductance. RV O2 extraction remained constant at 64 ± 4% as PaO2 was decreased, but after l-NNA, extraction increased to 70 ± 3% during normoxia and then to 78 ± 3% during hypoxia. RV MV̇o2 increased during hypoxia, but after l-NNA, MV̇o2 was lower at any respective PaO2. The relationship between heart rate times RV systolic pressure (rate-pressure product) and RV MV̇o2 was not altered by l-NNA. To account for l-NNA-mediated decreases in RV MV̇o2, O2 demand/supply variables were plotted as functions of MV̇o2. Slope of the conductance-MV̇o2 relationship was depressed by l-NNA ( P = 0.03), whereas the slope of the extraction-MV̇o2 relationship increased ( P = 0.003). In summary, increases in RV MV̇o2 during hypoxia are met normally by increasing RC blood flow. When NO synthesis is blocked, the large RV O2 extraction reserve is mobilized to maintain RV O2 demand/supply balance. We conclude that NO contributes to RC vasodilation during systemic hypoxia.
Akt Activation Is Necessary for Growth Factor–Induced Trafficking of Functional KCaChannels in Developing Parasympathetic Neurons
Authors: Chae Kwon-Seok , Martin-Caraballo Miguel , Anderson Marc , Dryer Stuart E.
Published: October 2004

The protein kinase Akt is a crucial regulator of neuronal survival and apoptosis. Here we show that Akt activation is necessary for mobilization of large-conductance KCachannels in ciliary ganglion (CG) neurons evoked by β-neuregulin-1 (NRG1) and transforming growth factor-β1 (TGFβ1). Application of NRG1 to embryonic day 9 (E9) CG neurons increased Akt phosphorylation, as observed previously for TGFβ1. NRG1- and TGFβ1-evoked stimulation of KCais blocked by inhibitors of PI3K by overexpression of a dominant-negative form of Akt, by overexpression of CTMP, an endogenous negative regulator of Akt, and by application of the Akt inhibitor 1L-6-hydroxymethyl-chiro-inositol 2-( R)-2- O-methyl-3- O-octadecylcarbonate (HIMO). Conversely, overexpression of a constitutively-active form of Akt was sufficient by itself to increase mobilization of functional KCachannels. NRG1 and TGFβ1 evoked an Akt-dependent increase in cell-surface SLO α-subunits. These procedures have no effect on voltage-activated Ca2+currents. Thus Akt plays an essential role in the developmental regulation of excitability in CG neurons.
ℋ∞ constant gain state feedback stabilization of stochastic hybrid systems with Wiener process
Authors: Boukas E. K. , Al-Muthairi N. F.
Published: October 2004

This paper considers the stabilization problem of the class of continuous‐time linear stochastic hybrid systems with Wiener process. The ℋ∞ state feedback stabilization problem is treated. A state feedback controller with constant gain that does not require access to the system mode is designed. LMI‐based conditions are developed to design the state feedback controller with constant gain that stochastically stabilizes the studied class of systems and, at the same time, achieve the disturbance rejection of a desired level. The minimum disturbance rejection is also determined. Numerical examples are given to show the usefulness of the proposed results.
The beta Gumbel distribution
Authors: Nadarajah Saralees , Kotz Samuel
Published: October 2004

The Gumbel distribution is perhaps the most widely applied statistical distribution for problems in engineering. In this paper, we introduce a generalization—referred to as the beta Gumbel distribution—generated from the logit of a beta random variable. We provide a comprehensive treatment of the mathematical properties of this new distribution. We derive the analytical shapes of the corresponding probability density function and the hazard rate function and provide graphical illustrations. We calculate expressions for the nth moment and the asymptotic distribution of the extreme order statistics. We investigate the variation of the skewness and kurtosis measures. We also discuss estimation by the method of maximum likelihood. We hope that this generalization will attract wider applicability in engineering.
Itô‐Skorohod stochastic equations and applications to finance
Authors: Tudor Ciprian A.
Published: October 2004

We prove an existence and uniqueness theorem for a class of
Itô‐Skorohod stochastic equations. As an application, we
introduce a Black‐Scholes market model where the price of the
risky asset follows a nonadapted equation.
A finite capacity bulk service queue with single vacation and Markovian arrival process
Authors: Gupta U. C. , Sikdar Karabi
Published: October 2004

Vacation time queues with Markovian arrival process (MAP) are
mainly useful in modeling and performance analysis of
telecommunication networks based on asynchronous transfer mode
(ATM) environment. This paper analyzes a single‐server finite
capacity queue wherein service is performed in batches of maximum
size “b” with a minimum threshold “a” and arrivals are
governed by MAP. The server takes a single vacation when he finds
less than “a” customers after service completion. The
distributions of buffer contents at various epochs (service
completion, vacation termination, departure, arbitrary and
pre‐arrival) have been obtained. Finally, some performance
measures such as loss probability and average queue length are
discussed. Numerical results are also presented in some cases.
Vascular Injury Induces Expression of Periostin
Authors: Lindner Volkhard , Wang Qiaozeng , Conley Barbara A. , Friesel Robert E. , Vary Calvin P.H.
Published: October 2004

Objective—

Periostin mRNA is among the most strongly upregulated transcripts in rat carotid arteries after balloon injury. The goal of the present study was to gain insight into the significance of periostin in the vasculature.

Methods and Results—

Periostin expression after injury was localized to smooth muscle cells of the neointima and the adventitia. The expression of periostin in smooth muscle cells in vitro was not regulated by cytokines such as fibroblast growth factor-2 (FGF-2). In contrast, stimulation of MC3T3-E1 osteoblastic cells, NIH3T3 fibroblasts, or mesenchymal C3H10T1/2 cells with FGF-2 reduced periostin mRNA levels to <5% of controls, whereas conversely bone morphogenetic protein-2 (BMP-2) increased periostin mRNA levels. Periostin expression was induced and maintained during retinoic acid-induced smooth muscle cell differentiation in A404 cells. In addition, overexpression of periostin in C3H10T1/2 cells caused an increase in cell migration that could be blocked with an anti-periostin antibody.

Conclusions—

Periostin expression is associated with smooth muscle cell differentiation in vitro and promotes cell migration. Unlike other mesenchymally derived cell lines, periostin expression is not regulated by FGF-2 in smooth muscle cells. This distinction may be useful in discriminating smooth muscle and fibroblast lineages.
Superoxide Mediates Sympathoexcitation in Heart Failure
Authors: Gao Lie , Wang Wei , Li Yu-Long , Schultz Harold D. , Liu Dongmei , Cornish Kurtis G. , Zucker Irving H.
Published: October 2004

Chronic heart failure (CHF) is often associated with excitation of the sympathetic nervous system. This event is thought to be a negative predictor of survival in CHF. Sympathoexcitation and central angiotensin II (Ang II) have been causally linked. Recent studies have shown that NAD(P)H oxidase-derived reactive oxidant species (ROS) are important mediators of Ang II signaling. In the present study, we tested the hypothesis that central Ang II activates sympathetic outflow by stimulation of NAD(P)H oxidase and ROS in the CHF state. CHF was induced in male New Zealand White rabbits by chronic ventricular tachycardia. Using radio telemetry of arterial pressure and intracerebroventricular infusions, experiments were performed in the conscious state. Renal sympathetic nerve activity (RSNA) was recorded as a direct measure of sympathetic outflow. Intracerebroventricular Ang II significantly increased RSNA in sham (131.5±13.3% of control) and CHF (193.6±11.9% of control) rabbits. The increase in CHF rabbits was significantly greater than in sham rabbits (
P
<0.01). These responses were abolished by intracerebroventricular losartan, tempol, or apocynin. Resting RSNA was significantly reduced by intracerebroventricular losartan, tempol, or apocynin in CHF rabbits but not in sham rabbits. Intracerebroventricular administration of the superoxide dismutase inhibitor diethyldithio-carbamic acid increased RSNA significantly more in sham compared with CHF rabbits. NADPH-dependent superoxide anion production in the rostral ventrolateral medulla (RVLM) was increased by 2.9-fold in CHF rabbits compared with sham rabbits. Finally, increases in the RVLM mRNA and protein expression of Ang II type 1 (AT
1
) receptor and subunits of NAD(P)H oxidase (p40

phox

,
p47

phox

, and gp91

phox

) were demonstrated in CHF rabbits. These data demonstrate intense radical stress in autonomic areas of the brain in experimental CHF and provide evidence for a tight relationship between Ang II and ROS as contributors to sympathoexcitation in CHF.