bluuebunny/crossref_metadata_2025 huggingface dataset:
Opposite Role of Pro‐Inflammatory Alleles in Acute Myocardial Infarction and Longevity
Authors: CANDORE GIUSEPPINA , BALISTRERI CARMELA RITA , GRIMALDI MARIA PAOLA , LISTÌ FLORINDA , VASTO SONYA , CARUSO MARCO , CAIMI GREGORIO , HOFFMANN ENRICO , COLONNA‐ROMANO GIUSEPPINA , LIO DOMENICO , PAOLISSO GIUSEPPE , FRANCESCHI CLAUDIO , CARUSO CALOGERO
Published: June 2006

Abstract:  The major trait characterizing offspring in centenarians is a reduction in the prevalence of cardiovascular disease. Because a pro‐inflammatory genotype seems to contribute significantly to the risk of coronary heart disease, alleles associated with disease susceptibility would not be included in the genetic background favoring longevity, as suggested by our previous studies on inflammatory cytokines. To confirm whether genotypes of inflammatory molecules play an opposite role in atherosclerosis and longevity, we are studying the role of other proinflammatory alleles, such as pyrin and CCR5, in acute myocardial infarction and longevity. The results support the hypothesis that the genetic background favoring cardiovascular diseases is detrimental to longevity. In addition, they suggest that the centenarian genetic background may be useful for investigating genetic key components of age‐associated diseases that are characterized by a multifactorial etiology.
Reduced Expression Levels of the Senescence Biomarker Clusterin/Apolipoprotein J in Lymphocytes from Healthy Centenarians
Authors: TROUGAKOS IOANNIS P. , PETROPOULOU CHARIKLIA , FRANCESCHI CLAUDIO , GONOS EFSTATHIOS S.
Published: June 2006

Abstract:  Clusterin/apolipoprotein J (CLU) is a conserved, ubiquitously expressed secreted glycoprotein that has been implicated in several physiological processes and was found to accumulate in many severe physiological disturbances. We have previously shown that the CLU gene and protein are upregulated during replicative senescence, stress‐induced premature senescence, in vivo aging, and in several age‐related diseases. In this study we have examined the CLU gene relationship to human longevity. We recruited and further analyzed 96 blood samples from Italian and Greek healthy donors of different ages, including 49 centenarians. We found that although the CLU gene expression levels increase during aging, in the centenarians' samples CLU levels were lower than those found in old donors. We then investigated the possible existence of a genetic polymorphism related to longevity at the CLU structural locus. A neutral noncoding sequence variant was detected 35 nucleotides upstream from exon 6, which does not correlate, however, with the age of the donor. We conclude that CLU gene accumulation during in vivo aging does not directly relate to chronological age, but rather indicates increased levels of organismal stress due to a progressive failure of homeostasis and/or to prolonged exposure to a stressful environment.
Possible Associations between Successful Aging and Polymorphic Markers in the Werner Gene Region
Authors: SILD MARI , KOCA CEMILE , BENDIXEN METTE H. , FREDERIKSEN HENRIK , McGUE MATT , KØLVRAA STEEN , CHRISTENSEN KAARE , NEXØ BJØRN
Published: June 2006

Abstract:  Werner syndrome (WS) is an autosomal recessive segmental progeroid syndrome caused by mutations in the Werner (WRN) gene leading to the early onset of many (but not all) aspects of normal aging. To investigate whether the WRN gene affects the course of aging in non‐Werner syndrome individuals, we performed association studies analyzing several single nucleotide polymorphisms (SNPs) in the WRN locus. We found certain close‐set SNPs in the 5′ flanking region and 5′ UTR to be significantly associated with the cognitive functioning level in old age.
Identification of Genes Involved in Healthy Aging and Longevity
Authors: WEIBEL JENS , DRÆBY SØRENSEN MORTEN , KRISTENSEN PETER
Published: June 2006

Abstract:  Studies suggest that the region around microsatellite marker D4S1564 on chromosome 4 is in some way linked to longevity. As a part of the integrated European project Genetics of Healthy Aging (GeHA), we set out to investigate the genes found in this region using a proteomics approach. Here, we report the cloning of six candidate genes.
Kinetin‐Induced Differentiation of Normal Human Keratinocytes Undergoing Aging in Vitro
Authors: BERGE ULRICH , KRISTENSEN PETER , RATTAN SURESH I. S.
Published: June 2006

Abstract:  Kinetin (N6‐furfuryladenine) is a cytokinin growth factor having several anti‐aging effects reported for human cells and fruit flies. We have observed that short‐term culturing of human keratinocytes in the presence of 40 to 200 μM kinetin results in a significant inhibition of cell growth. Studies were undertaken to analyze the process of differentiation as a reason for growth inhibition. Keratinocytes at different passage levels were treated with fetal calf serum (FCS) and calcium as differentiation‐inducing positive controls, with different concentrations of kinetin, and with a combination of kinetin and calcium. The induction and progression of differentiation was monitored by morphological observations and by using several differentiation markers, including keratins (K10 and K14), involucrin, epidermal transglutaminase, and some new keratinocyte‐specific antibodies isolated by the phage display method. In young keratinocytes, two days of calcium treatment reduced the K14 level by 78%, and increased the levels of K10 and involucrin by 40% and 29%, respectively. In comparison, 40 μM kinetin had no effect on the K14 level, but increased the K10 level by 28% and that of involucrin by four‐fold. The combination of calcium and 40 μM kinetin led to a decrease by 23% in the K14 level, to an increase in the level of K10 by 55%, and to a two‐fold rise in the involucrin level. These results suggest that the rate, extent, and quality of differentiation depend on the inducing agent, and that kinetin may be useful in promoting the differentiation of human keratinocytes, especially in the presence of calcium.
MAP Kinases and Heat Shock–Induced Hormesis in Human Fibroblasts during Serial Passaging in Vitro
Authors: NIELSEN ELISE R. , ESKILDSEN‐HELMOND YVONNE E.G. , RATTAN SURESH I.S.
Published: June 2006

Abstract:  Adult human skin fibroblasts were exposed repeatedly to 41°C or 42°C heat shock (HS) for 1 h twice a week during serial passaging throughout their replicative life span. On the basis of longevity curves, cell size, and morphology, we observed that repeated mild heat shock (RMHS) at 41,°C had strong anti‐aging hormetic effects, including 20% extension of cellular longevity. The basal levels of the MAP kinases JNK1, JNK2, and p38 increased during serial passaging, while that of ERK2 decreased. RMHS further exaggerated these effects, which suggests that age‐related changes in MAP kinases may be an adaptive response for better cell survival.
The Roles of Satellite Cells and Hematopoietic Stem Cells in Impaired Regeneration of Skeletal Muscle in Old Rats
Authors: MACHIDA SHUICHI , NARUSAWA MITSUO
Published: June 2006

Abstract:  Sarcopenia is the involuntary loss of skeletal muscle mass and strength that occurs with aging, resulting in physical frailty. One potential explanation for sarcopenia is the failure of muscle to regenerate after damage, some of which may be due to changes in the function of satellite cells. Recent studies have identified novel populations of adult stem cells in skeletal muscle, such as hematopoietic stem cells. To understand the cellular mechanisms of sarcopenia, we examined the expression of satellite cells and hematopoietic stem cells in old regenerating muscles based on the expression profiles of several markers related to those cells.
Age‐Related Effects of Dexamethasone Administration in Adrenal Zona Reticularis
Authors: ALMEIDA HENRIQUE , MATOS LILIANA , FERREIRA JORGE , NEVES DELMINDA
Published: June 2006

Abstract:  Suppression of adrenocorticotropic hormone results in reduced adrenal steroid output, adrenocortical cell atrophy, and apoptosis in young rats. To verify such effects during aging, dexamethasone was injected into rats for 3 days at five different ages; at day 4, adrenals and blood were collected for morphologic and corticosterone assay. Adrenal structure was similar at all ages, but in dexamethasone‐injected animals there were ultrastructural features of apoptosis and a higher percentage of TUNEL and caspase‐3‐labeled nuclei and cytoplasm; their corticosterone decreased significantly. In both groups, there was age‐related decrease in the percentage of apoptotic cells, significant only in dexamethasone‐injected rats. The data suggest that aged adrenocortical cells are less susceptible to the lack of adrenocorticotropic hormone (ACTH), possibly as a result of their decreased functional ability.
Would Carnosine or a Carnivorous Diet Help Suppress Aging and Associated Pathologies?
Authors: HIPKISS ALAN R.
Published: June 2006

Abstract: Carnosine (β‐alanyl‐l‐histidine) is found exclusively in animal tissues. Carnosine has the potential to suppress many of the biochemical changes (e.g., protein oxidation, glycation, AGE formation, and cross‐linking) that accompany aging and associated pathologies. Glycation, generation of advanced glycosylation end‐products (AGEs), and formation of protein carbonyl groups play important roles in aging, diabetes, its secondary complications, and neurodegenerative conditions. Due to carnosine's antiglycating activity, reactivity toward deleterious carbonyls, zinc‐ and copper‐chelating activity and low toxicity, carnosine and related structures could be effective against age‐related protein carbonyl stress. It is suggested that carnivorous diets could be beneficial because of their carnosine content, as the dipeptide has been shown to suppress some diabetic complications in mice. It is also suggested that carnosine's therapeutic potential should be explored with respect to neurodegeneration. Olfactory tissue is normally enriched in carnosine, but olfactory dysfunction is frequently associated with neurodegeneration. Olfactory administration of carnosine could provide a direct route to compromised tissue, avoiding serum carnosinases.
Nutraceutical Supplementation: Effect of a Fermented Papaya Preparation on Redox Status and DNA Damage in Healthy Elderly Individuals and Relationship with GSTM1 Genotype
Authors: MAROTTA FRANCESO , WEKSLER MARK , NAITO YASUHIRO , YOSHIDA CHISATO , YOSHIOKA MAYUMI , MARANDOLA PAOLO
Published: June 2006

Abstract:  Our study group consisted of 54 elderly patients without major invalidating diseases who were randomly divided into two fully matched groups. Group A was given a certified fermented papaya preparation 9 g/day by mouth, while group B received placebo. Treatment was carried out in a cross‐over manner with a 3‐month supplementation followed by a 6‐week washout period. Blood samples were drawn at entry and on a monthly basis to check routine parameters, redox status, and 8‐OHdG in circulating leukocyte DNA. Polymorphism analysis of GSTM1 was carried out as well. The glutathune‐S transferase M1 (GSTM1) genotype was null (−) in 40% and 46% of groups A and B, respectively. GSTM1 (−) smokers had a significantly higher level of plasma DNA adducts and leukocytes level of 8‐OHdG than their GSTM1 (+) counterparts (P < 0.01). There was a weak correlation between cigarettes smoked/day and DNA adduct (r: 0.61, P < 0.05), which also correlated with antioxidant concentrations, but only in GSTM1 (−) smokers (P < 0.01). The fermented papaya preparation (FPP)–supplemented group showed a significant enhancement of the antioxidant protection (P < 0.01 vs. A) within the subgroups with GSTM1 (−) and of plasma DNA adduct, irrespective of the GSTM1 genotype. Only the GSTM1 (−) subgroup was the one that, under FPP treatment, increased lymphocyte 8‐OHdG (P < 0.01). Such preliminary data show that FPP is a promising nutraceutical for improving antioxidant‐defense in elderly patients even without any overt antioxidant‐deficiency state while helping explain some inconsistent results of prior interventional studies.
Redox Status Impairment in Liver and Kidney of Prematurely Senescent Mice
Authors: MAROTTA F. , LORENZETTI F. , HARADA M. , ONO‐NITA S. K. , MINELLI E. , MARANDOLA P.
Published: June 2006

Abstract:  T‐maze test–selected prematurely senescent mice (PSM) were allocated into two groups: (A) those given DTS (150 mg/kg) orally for 30 days and (B) untreated PSM with age‐matched fast T‐maze performers as control. After sacrifice, the liver and kidney were analyzed for catalase (CAT) activity, glutathione peroxidase (GPx), superoxide dismutase (SOD), malondyaldehyde (MDA), and plasma thiols. Untreated PSM showed decreased plasma thiols and tissue level of CAT, SOD, GPx, with higher MDA (P < 0.01 vs. fast performers), while DTS (Denshichi–Tochiu–Sen) significantly improved glutathione and cysteine (P < 0.05) and tissue concentration of the above parameters (P < 0.05). Such preliminary data suggest that DTS mitigated oxidative damage in PSM, with likely action on the cytoplasm and mitochondrial matrix.
A Dietary Supplement Improves Outcome in an Experimental Influenza Model in Old Mice
Authors: CERVI J. , MAROTTA F. , BATER C. , MASULAIR K. , MINELLI E. , HARADA M. , MARANDOLA P.
Published: June 2006

Abstract:  Twenty‐month‐old Swiss mice were allocated into three groups: (A) control; (B) infected group; and (C) infected but treated with 5 mg of the phytocompound MMT. Mice were infected intranasally with 30 μL of 75 HA viral units. MMT markedly blunted the nasal signs of virus infection and the febrile response. Formazan‐positive cells, lung and plasma lipoperoxides, and TNF‐α in lung tissue increased during viral infection, but improvement was seen in the MMT‐treated group (P < 0.05). MMT also normalized SOD, catalase activities, and ascorbic acid and determined a significant decrease of lung but not nasal viral titer, although nasal inflammatory infiltrate dropped significantly. MMT has potential clinical applications with and has an excellent safety profile even in old animals.
Exercise and Hormesis
Authors: JI LI LI , GOMEZ‐CABRERA MARIA‐CARMEN , VINA JOSE
Published: June 2006

Abstract:  Contraction‐induced production of reactive oxygen species (ROS) has been shown to cause oxidative stress to skeletal muscle. As an adaptive response, muscle antioxidant defense systems are upregulated after heavy exercise. Nuclear factor (NF) κB and mitogen‐activated protein kinases (MAPKs) are the major oxidative stress–sensitive signal transduction pathways in mammalian tissues. Activation of NF‐κB signaling cascade has been shown to enhance the gene expression of important enzymes, such as mitochondrial superoxide dismutase (MnSOD) and inducible nitric oxide synthase (iNOS). MAPK activations are involved in a variety of cellular functions including growth, proliferation, and adaptation. We investigated the effect of an acute bout of exercise on NF‐κB and MAPK signaling, as well as on the time course of activation, in rat skeletal muscle. In addition, we studied the role of ROS in the exercise‐induced upregulation of MnSOD and iNOS, and the potential interactions of NF‐κB and MAPK in the signaling of these enzymes. Our data suggest that ROS may serve as messenger molecules to activate adaptive responses through these redox‐sensitive signaling pathways to maintain cellular oxidant‐antioxidant homeostasis during exercise.
Stem Cells
Authors: KASSEM MOUSTAPHA
Published: June 2006

Abstract:  Aging is associated with a progressive failing of tissues and organs of the human body leading to a large number of age‐related diseases. Regenerative medicine is an emerging clinical discipline that aims to employ cellular medicines (normal cells, ex vivo expanded cells, or tissue‐engineered organs) to restore the functions of damaged or defective tissues and organs and thus to “rejuvenate” the failing aging body. One of the most important sources for cellular medicine is embryonic and adult (somatic) stem cells (SSCs). One example of SCCs with enormous clinical potential is the mesenchymal stem cells (MSCs) that are present in the bone marrow and are able to differentiate into cell types such as osteoblasts, chondrocytes, endothelial cells, and probably also neuron‐like cells. Because of the ease of their isolation and their extensive differentiation potential, MSCs are among the first stem cell types to be introduced in the clinic. Some recent studies have demonstrated the possible use of MSCs in systemic transplantation for systemic diseases, local implantation for local tissue defects, as a vehicle for genes in gene therapy protocols, or to generate transplantable tissues and organs in tissue‐engineering protocols. However, several challenges confront the use of these cells in the clinic, ranging from biological challenges (e.g., how to isolate a homogenous populations of the cells with specific criteria from the bone marrow and how to expand them ex vivo without affecting their differentiation potential) to biotechnological challenges (e.g., how to develop easy methods for quality control of the cellular‐based products). While it is expected that cellular medicines will decrease the burden of several age‐related diseases, it is not clear whether they can change the course of the aging process itself and thus prolong human life.
RNA Regulation in Mammals
Authors: SZYMANSKI MACIEJ , BARCISZEWSKI JAN
Published: June 2006

Abstract:  Noncoding RNAs (ncRNA) are ubiquitous regulatory factors affecting gene expression in all organisms. In eukaryotes ncRNAs have been shown to operate on virtually every level of transmission of genetic information. They are implicated in processes that are crucial for the correct growth and development of multicellular organisms. Changes in their expression are often related to stress conditions or associated with diseases or developmental disorders.
Techniques Used in Studies of Age‐Related DNA Methylation Changes
Authors: WOJDACZ TOMASZ K. , HANSEN LISE LOTTE
Published: June 2006

Abstract:  Epigenetic modification of CpG islands (CGIs) in promoter regions is an important regulatory mechanism of gene expression in eukaryotic cells. Hypermethylation of CGIs may silence a gene, whereas hypomethylation of previously methylated CGIs allows gene expression. The pattern of methylation is cell‐type‐specific and established during development of the organisms. Changes in the methylation pattern have been found in all cancer forms and in aging cells. The epigenetic‐related alternations of gene expression status may significantly contribute to the initiation and maintenance of malignant growth. Cancer incidence increases dramatically with age and correlates strongly with age‐related methylation changes. Many techniques have been developed to analyze the genome‐wide methylation content and the methylation status of specific loci. The majority of methylation screening protocols utilizes methylation‐sensitive endonuclease digestion or bisulfite treatment of the template followed by subsequent PCR amplification of a specific sequence. All methods either examine only one specific DNA sequence at a time, or provide limited genomic information on the screened sequences. The principle of our new approach is to combine methylation‐sensitive enzyme digestion with the comparative genomic hybridization (CGH) technique to develop an array‐based method to screen the entire genome for changes of methylation pattern. The new technique will serve as an efficient tool in understanding the nature of epigenetic changes and their significance to the aging process and cancer development.
The Influence of Race and Gender on Time to Initial Electrocardiogram for Patients with Chest Pain
Authors: Takakuwa Kevin M. , Shofer Frances S. , Hollander Judd E.
Published: June 2006

Objectives:
To determine whether race or gender affected time to initial electrocardiogram (ECG) for patients who presented to an emergency department with chest pain.

Methods:
This was a prospective cohort study of patients with chest pain. Patients were divided into three groups based on final diagnosis of acute myocardial infarction or unstable angina and all others with noncardiac chest pain. Data were analyzed using ranks in a two‐way analysis of covariance adjusted for age.

Results:
A total of 4,358 patients were studied; 58.6% were women and 41.4% men, and 70.3% were African American, 26.0% white, and 3.6% other. Overall, nonwhite patients had longer times to initial ECG compared with white patients. These effects were consistent regardless of ultimate diagnosis. Overall, women had longer times to initial ECG than men. However, ECG time differed by final diagnosis. There were no differences in time to ECG for women compared with men with acute myocardial infarction or unstable angina, but women received an ECG significantly slower than men for noncardiac chest pain.

Conclusions:
The first screening test for acute coronary syndrome, the ECG, took longer to obtain for nonwhite patients, regardless of final diagnosis. This was unfortunately consistent with the literature that shows racial disparities in all aspects of emergent cardiac care. For women, the overall delay in ECG time can be explained by delays for those women with noncardiac chest pain.
Equipment, Supplies, and Pharmaceuticals: How Much Might It Cost to Achieve Basic Surge Capacity?
Authors: Hanfling Dan
Published: June 2006

The ability to deliver optimal medical care in the setting of a disaster event, regardless of its cause, will in large part be contingent on an immediately available supply of key medical equipment, supplies, and pharmaceuticals. Although the Department of Health and Human Services Strategic National Stockpile program makes these available through its 12‐hour “push packs” and vendor‐managed inventory, every local community should be funded to create a local cache for these items. This report explores the funding requirements for this suggested approach. Furthermore, the response to a surge in demand for care will be contingent on keeping available staff close to the hospitals for a sustained period. A proposal for accomplishing this, with associated costs, is discussed as well.
Overcoming Resistance to Interferon-Induced Apoptosis of Renal Carcinoma and Melanoma Cells by DNA Demethylation
Authors: Reu Frederic J. , Bae Soo In , Cherkassky Leonid , Leaman Douglas W. , Lindner Daniel , Beaulieu Normand , MacLeod A. Robert , Borden Ernest C.
Published: June 2006

Epigenetic editing of gene expression by aberrant methylation of DNA may help tumor cells escape attack from the innate and acquired immune systems. Resistance to antiproliferative effects and apoptosis induction by interferons (IFNs) was postulated to result from silencing of IFN response genes by promoter hypermethylation. Treatment of human ACHN renal cell carcinoma (RCC) and A375 melanoma cells with the DNA demethylating nucleoside analog 5-AZA-2′-deoxycytidine (5-AZA-dC) synergistically augmented antiproliferative effects of IFN- alpha (α) 2 and IFN-beta (β). Either 5-AZA-dC or an antisense to DNA methyltransferase 1 (DNMT1) overcame resistance to apoptosis induction by IFNs with up to 85% apoptotic cells resulting from the combinations. No similar potentiation occurred in normal kidney epithelial cells. IFN response genes were augmented more than 10 times in expression by 5-AZA-dC. Demethylation by 5-AZA-dC of the promoter of the prototypic, apoptosis-associated IFN response gene XAF1 was confirmed by methylation-specific polymerase chain reaction. siRNA to XAF1 inhibited IFN-induced apoptosis; conversely, overexpression of XAF1 overcame resistance to apoptosis induction by IFN-β. As occurred with apoptosis-resistant melanoma cells in vitro, tumor growth inhibition in the nude mouse of human A375 melanoma xenografts resulted from treatment with 5-AZA-dC in combination with IFN-β, an effect not resulting from either single agent. The importance of epigenetic remodeling of expression of immune-modifying genes in tumor cells was further suggested by identifying reactivation of the cancer-testis antigens MAGE and RAGE in ACHN cells after DNMT1 depletion. Thus, inhibitors of DNMT1 may have clinical relevance for immune modulation by augmentation of cytokine effects and/or expression of tumor-associated antigens.
Breast-Conserving Treatment With or Without Radiotherapy in Ductal Carcinoma-In-Situ: Ten-Year Results of European Organisation for Research and Treatment of Cancer Randomized Phase III Trial 10853—A Study by the EORTC Breast Cancer Cooperative Group and EORTC Radiotherapy Group
Authors: Bijker Nina , Meijnen Philip , Peterse Johannes L. , Bogaerts Jan , Van Hoorebeeck Irène , Julien Jean-Pierre , Gennaro Massimiliano , Rouanet Philippe , Avril Antoine , Fentiman Ian S. , Bartelink Harry , Rutgers Emiel J. Th.
Published: June 2006

Purpose

The European Organisation for Research and Treatment of Cancer conducted a randomized trial investigating the role of radiotherapy (RT) after local excision (LE) of ductal carcinoma-in-situ (DCIS) of the breast. We analyzed the efficacy of RT with 10 years follow-up on both the overall risk of local recurrence (LR) and related to clinical, histologic, and treatment factors.

Patients and Methods

After complete LE, women with DCIS were randomly assigned to no further treatment or RT (50 Gy). One thousand ten women with mostly (71%) mammographically detected DCIS were included. The median follow-up was 10.5 years.

Results

The 10-year LR-free rate was 74% in the group treated with LE alone compared with 85% in the women treated by LE plus RT (log-rank P < .0001; hazard ratio [HR] = 0.53). The risk of DCIS and invasive LR was reduced by 48% (P = .0011) and 42% (P = .0065) respectively. Both groups had similar low risks of metastases and death. At multivariate analysis, factors significantly associated with an increased LR risk were young age (≤ 40 years; HR = 1.89), symptomatic detection (HR = 1.55), intermediately or poorly differentiated DCIS (as opposed to well-differentiated DCIS; HR = 1.85 and HR = 1.61 respectively), cribriform or solid growth pattern (as opposed to clinging/micropapillary subtypes; HR = 2.39 and HR = 2.25 respectively), doubtful margins (HR = 1.84), and treatment by LE alone (HR = 1.82). The effect of RT was homogeneous across all assessed risk factors.

Conclusion

With long-term follow-up, RT after LE for DCIS continued to reduce the risk of LR, with a 47% reduction at 10 years. All patient subgroups benefited from RT.
Generating stationary random graphs on ℤ with prescribed independent, identically distributed degrees
Authors: Deijfen Maria , Meester Ronald
Published: June 2006

Let F be a probability distribution with support on the nonnegative integers. We describe two algorithms for generating a stationary random graph, with vertex set ℤ, in which the degrees of the vertices are independent, identically distributed random variables with distribution F. Focus is on an algorithm generating a graph in which, initially, a random number of ‘stubs’ with distribution F is attached to each vertex. Each stub is then randomly assigned a direction (left or right) and the edge configuration obtained by pairing stubs pointing to each other, first exhausting all possible connections between nearest neighbors, then linking second-nearest neighbors, and so on. Under the assumption that F has finite mean, it is shown that this algorithm leads to a well-defined configuration, but that the expected length of the shortest edge attached to a given vertex is infinite. It is also shown that any stationary algorithm for pairing stubs with random, independent directions causes the total length of the edges attached to a given vertex to have infinite mean. Connections to the problem of constructing finitary isomorphisms between Bernoulli shifts are discussed.
Data network models of burstiness
Authors: D'Auria Bernardo , Resnick Sidney I.
Published: June 2006

We review characteristics of data traffic which we termstylized facts: burstiness, long-range dependence, heavy tails, bursty behavior determined by high-bandwidth users, and dependence determined by users without high transmission rates. We propose an infinite-source Poisson input model which supplies traffic in adjacent time slots. We study properties of the model as slot width decreases and traffic intensity increases. This model has the ability to account for many of the stylized facts.
Coalescent lineage distributions
Authors: Griffiths Robert C.
Published: June 2006

We study identities for the distribution of the number of edges at time t back (i.e. measured backwards) in a coalescent tree whose subtrees have no mutations. This distribution is important in the infinitely-many-alleles model of mutation, where every mutation is unique. The model includes, as a special case, the number of edges in a coalescent tree at time t back when mutation is ignored. The identities take the form of expected values of functions of Zt=eiXt, where Xt is distributed as standard Brownian motion. Associated identities are also found for the distributions of the time to the most recent common ancestor, the time until loss of ancestral lines by coalescence or mutation, and the age of a mutation. Hypergeometric functions play an important role in the identities. The identities are of mathematical interest, as well as potentially being formulae to use for numerical integration or simulation to compute distributions that are usually expressed as alternating-sign series expansions, which are difficult to compute.
Harmonic moments of inhomogeneous branching processes
Authors: Piau Didier
Published: June 2006

We study the harmonic moments of Galton-Watson processes that are possibly inhomogeneous and have positive values. Good estimates of these are needed to compute unbiased estimators for noncanonical branching Markov processes, which occur, for instance, in the modelling of the polymerase chain reaction. By convexity, the ratio of the harmonic mean to the mean is at most 1. We prove that, for every square-integrable branching mechanism, this ratio lies between 1-A/k and 1-A/k for every initial population of size k>A. The positive constants A and Aͤ are such that A≥Aͤ, are explicit, and depend only on the generation-by-generation branching mechanisms. In particular, we do not use the distribution of the limit of the classical martingale associated with the Galton-Watson process. Thus, emphasis is put on nonasymptotic bounds and on the dependence of the harmonic mean upon the size of the initial population. In the Bernoulli case, which is relevant for the modelling of the polymerase chain reaction, we prove essentially optimal bounds that are valid for every initial population size k≥1. Finally, in the general case and for sufficiently large initial populations, similar techniques yield sharp estimates of the harmonic moments of higher degree.
Improved algorithms for rare event simulation with heavy tails
Authors: Asmussen Søren , Kroese Dirk P.
Published: June 2006

The estimation of P(Sn>u) by simulation, where Sn is the sum of independent, identically distributed random varibles Y1,…,Yn, is of importance in many applications. We propose two simulation estimators based upon the identity P(Sn>u)=nP(Sn>u, Mn=Yn), where Mn=max(Y1,…,Yn). One estimator uses importance sampling (for Yn only), and the other uses conditional Monte Carlo conditioning upon Y1,…,Yn−1. Properties of the relative error of the estimators are derived and a numerical study given in terms of the M/G/1 queue in which n is replaced by an independent geometric random variable N. The conclusion is that the new estimators compare extremely favorably with previous ones. In particular, the conditional Monte Carlo estimator is the first heavy-tailed example of an estimator with bounded relative error. Further improvements are obtained in the random-N case, by incorporating control variates and stratification techniques into the new estimation procedures.
Effects of Staged Cooling in Shrink-Fitting Compounded Cylinders
Authors: Collier N. O , Kaw A. K , Besterfield G. H , Rahman M. M
Published: June 2006

This paper studies the effect of staged cooling of compounded cylinders in avoiding cracking due to the presence of large interference stresses and low fracture toughness in the presence of cryogenic temperatures. This study is motivated by the assembly procedure of the fulcrum (a compounded trunnion-hub assembly) of bascule bridges, where the fulcrum is shrunk by immersion in liquid nitrogen so that it can then be fitted into the girder of the bridge. In a few cases, the fulcrum developed cracks during the immersion in liquid nitrogen. To study the effect of staged cooling to avoid such cracking, a finite difference model was developed of a long compounded cylinder with axisymmetric response with temperature-dependent properties. The study showed that the resistance to failure was increased by as much as 50 per cent when the compounded cylinder is cooled first in a refrigerated air chamber and followed by immersion in liquid nitrogen.
Eigenstrain Analysis of Synchrotron X-Ray Diffraction Measurement of Residual Strains in Machined Nickel Alloy Plates
Authors: Korsunsky A M , Regino G M , Latham D , Liu Jian , Nowell D , Walsh M
Published: June 2006

Manufacturing processes such as machining, surface treatment, welding, plastic forming, and stretching introduce permanent strains into workpieces and engineering components, leading to the creation of residual stresses. Residual stresses exert a significant influence on the deformation behaviour of components, e.g. inducing distortion during further machining, and also affecting their response to thermal and mechanical loading in service. This has important implications for dimensional stability and durability of components and engineering assemblies. In the present study a combined experimental and modelling analysis of a particular case of residual stresses induced in a nickel superalloy plate by heavy surface machining is presented. The residual elastic strain profile in the plate is determined using high-energy synchrotron diffraction. A variational procedure is then used to evaluate the underlying eigenstrain distribution responsible for the observed residual strain state. The relaxation of this residual strain state during subsequent sectioning of the plate is then considered. This example is used in order to assess the difference in the modelled residual strain and stress state obtained using three-dimensional, plane strain, and plane stress models of the coupon. The implications of these results for residual stress interpretation using eigenstrain procedures are discussed.
An Alternative Approach to Analysis of Plane-Strain Pure Bending at Large Strains
Authors: Alexandrov S , Hoon Kim Ji , Chung Kwansoo , Jin Kang Tae
Published: June 2006

A uniform analysis of plane-strain bending for different rigid/plastic and elastic/plastic constitutive laws is performed. In most cases numerical treatment is reduced to solving an ordinary differential equation. The solutions obtained either coincide with known exact solutions or show the same tendencies as known approximate solutions. In addition, new solutions are obtained, including an elastic/plastic solution at large strains. The through-thickness distribution of the principal stresses and the variation in the bending moment as well as the thickness of the layer with a time-like parameter are illustrated.
Vehicle Stability Control with Regenerative Braking and Electronic Brake Force Distribution for a Four-Wheel Drive Hybrid Electric Vehicle
Authors: Kim Donghyun , Kim Hyunsoo
Published: June 2006

Vehicle stability control for a four-wheel drive (4WD) hybrid electric vehicle is investigated using the regenerative braking of the rear motor and electrohydraulic brake (EHB). A fuzzy-rule-based control algorithm is proposed, which generates the direct yaw moment to compensate for the errors of the sideslip angle and yaw rate. Performance of the stability control logic is evaluated for J-turn and single-lane change. It is found from the simulation results that the regenerative braking of the rear motor is able to provide improved stability compared with the vehicle performance without any control. It is found that better performance can be achieved by applying the regenerative braking plus the EHB control. In addition, the optimal distribution ratio of the EHB force is presented to minimize the EHB power consumption. The simulation results show that the required torque level by the optimal EHB distribution ratio control is much lower than that of the fixed distribution ratio, while providing almost the same control performance. It is expected that the vehicle stability control algorithm suggested in this study is able to offer improved vehicle stability.
A Crash Severity Algorithm for All Frontal Crash Modes Using Compensation Factors
Authors: Park T-W , Jeong H-Y , Park S-W
Published: June 2006

In advanced air bag systems, there are normally two satellite accelerometers at the front and one accelerometer in the air bag electronic control unit (ACU) at the central tunnel. By using the deceleration signals from these accelerometers, crash algorithms in the ACU should determine whether or not and when air bag deployment is required, and how severe the crash is. In order to modulate the air bag power, the information on the crash severity as well as on the occupant position, occupant weight, and belt usage is essential. In this paper, a new crash discrimination algorithm and a new crash severity algorithm were developed for a sedan. For the crash discrimination algorithm, two metrics were proposed to be used, and the times to fire air bags were determined only when both metrics became bigger than their respective thresholds. For the crash severity algorithm, two compensation factors for an oblique, an offset, or a pole crash were proposed to be used, and crash severity levels were determined for all crash tests without classifying the crash modes but by comparing a metric with its thresholds set the same for all crash modes. The reliability of the algorithms was also evaluated for numerous crash signals generated by the Monte-Carlo method, and both algorithms were proven to be robust.
Effect of Injector Type on Fuel-Air Mixture Formation of High-Speed Diesel Sprays
Authors: Park Sung Wook , Kim Jae Wouk , Lee Chang Sik
Published: June 2006

This study was performed to analyse the characteristics of fuel sprays issued from a piezo-driven injector and to compare both experimental results and numerical predictions with those from a solenoid-driven injector. In order to study the effect of the injector type, two injectors with the same specifications - except for their drive type - were used in the experiments. In this work, the profiles of injection rates, processes of spray development, mean droplet size distributions, and mean velocities were obtained using an injection rate meter, a spray visualization system, and a phase Doppler particle analyser (PDPA) system.

In order to calculate the atomization process of the injected spray, the Kelvin-Helmholtz instability/droplet deformation and break-up ((KH-DDB) model was used, and the prediction accuracies were verified by comparing them with experimental results. For the numerical approach using the KIVA code, the nozzle flow and droplet break-up models were modified to consider the conditions of a common-rail injection system. The input parameters for the KIVA calculations were determined based on the nozzle flow model considering the effect of cavitation. In addition, the effects of injector type on the evaporation characteristics were calculated using the modified Spalding evaporation model.

This study reveals that the injection delay of the piezo-driven injector is shorter than that of the solenoid-driven injector by 0.06 ms, and that the atomization and evaporation performances of the fuel spray can be enhanced by using the piezo injector instead of the solenoid injector.
Thermomechanical Analysis of an Engine Cylinder Head
Authors: Shojaefard M H , Ghaffarpour M R , Noorpoor A R , Alizadehnia S
Published: June 2006

A large-scale, high-resolution finite element methodology for thermomechanical analysis of complex engine components has been developed. This paper describes the process and presents an example evaluation of an engine cylinder head. Because of its non-symmetric configuration, the cylinder head was entirely modelled. The geometric nature of the cylinder head requires very precise three-dimensional analysis techniques. The geometry modelling was carried out using a computer-aided engineering tool. Full multidimensional mechanical and thermal stress analysis in the cylinder head is made by using a finite element analysis commercial code. Validation of the simulation is achieved by comparison between simulation and experimental test results. The results of this analysis show high stresses at the valve bridge. These stresses result from a constrained thermal expansion of the cylinder head, and are generally compressive and radial in nature. Finite element analysis (FEA) and computational fluid dynamics (CFD) used in conjunction with experimental verification were found to be very powerful analysis tools for engine component development and design.
Four-Wheel Drive Control System using a Clutchless Centre Limited Slip Differential
Authors: Lee Hyeongcheol
Published: June 2006

This paper presents a control system design procedure for a four-wheel drive (4WD) system that uses a clutchless centre limited slip differential (CC-LSD) as the torque biasing device between the front and rear driveshafts. The paper describes mathematical analysis and modelling of the CC-LSD. It also presents a new analytical 4WD control method based on the vehicle dynamics by introducing several breakthrough control techniques, such as the control map with three different control modes, the vehicle turning estimation, and the forgetting factor concept. Simulation results show the feasibility and effectiveness of the model and the control method.
Effects of Design Parameters on the Slipping Torque of an Overrunning Clutch
Authors: Chen Yung-Chuan , Chen Li-Wen
Published: June 2006

In this study, both finite element analysis and experimental tests are conducted to explore the effects of design parameters on the slipping torque of overrunning clutches. The parameters discussed are: the friction coefficient, the tolerance of roller radius, the eccentric of the outer ring, and the number of rollers. Contact elements are used to model the contact between rings and rollers in finite element analyses. The experimental results are compared with the simulation results and are used to estimate the friction coefficient used in the finite element analysis. The results indicate that the friction coefficient, tolerance of roller radius, eccentric of outer ring, and number of rollers significantly affect the slipping torque. This study has also proposed a set-up for experimental tests of overrunning clutches.
Numerical Study of Friction and Heat Transfer Influence on Spark Ignition Engine Manifolds
Authors: Muñoz M , Morea-Roy J , Moreno F
Published: June 2006

A model has been developed in order to analyse the influence of friction and heat transfer between the exhaust gases and the inside wall of the exhaust manifold on spark ignition engine performance. One-dimensional unsteady compressible flow equations are used to describe instantaneous evolution of the flow inside the manifolds. Special attention is paid to friction and convective heat transfer source terms. A high-order total variation diminishing (TVD) scheme is applied to compute a second-order accurate numerical solution of the unsteady flow in engine manifolds. The combustion process in the spark ignition engine cylinder is described by a two-zone thermodynamic model. A series of numerical tests has been carried out. The influence of friction and convective heat transfer between the exhaust flow and the inside wall manifolds has been studied by analysing computed and experimental engine performance curves. Also, the instantaneous pressure at the exhaust manifold has been studied. The manifold pressure predicted by the developed model is successfully compared with experimental data from a spark ignition engine. From these comparisons it has been found that friction and heat transfer in exhaust manifolds play an important role in engine performance. Furthermore, it has been checked that the performance is not very sensitive to which friction factor correlation is chosen, whereas the engine performance is rather dependent on the constant factor set in the heat transfer correlation.
Temperature Analysis of a Gasket for an Internal Combustion Engine
Authors: Baek Dae Kyun , Khonsari M M
Published: June 2006

This paper presents a heat transfer analysis of a head gasket for an internal combustion (IC) engine. A steady state temperature analysis was conducted to investigate the effect of engine material on gasket temperature. Transient temperature analysis was also conducted to investigate temperature variations of gasket materials and the required time to reach steady state temperature. The transfer of heat from the combustion chamber into the wall (a positive heat flux) which occurs after the ignition and the reverse of this process during the expansion stroke (a negative heat flux) were mathematically represented using the Fourier series.
Diesel Engine Indicated and Load Torque Estimation Using a Non-Linear Observer
Authors: Zweiri Y H , Seneviratne L D
Published: June 2006

This paper presents a non-linear observer to estimate the indicated torque and the load torque of a single-cylinder diesel engine from crankshaft and coupling angular velocity measurements. Since these variables can be measured using low-cost sensors, the observer may be useful in the implementation of the control or diagnostics strategies that require cylinder indicated torque and load torque, variables that are not easily measured and need expensive sensors. The observer operates in the crank angle domain and is based on a nonlinear dynamic engine model that includes an instantaneous friction model. The effects of inertia variations of the crankshaft assembly with piston pin offset are also included, which significantly increases the accuracy of the pressure estimation at high speeds. Strong chattering is avoided by modifying the sliding gain as a non-linear function of the crank angle. The stability of the observer is proved, and simulation results of the engine indicated torque and load torque are presented, which indicate good agreement with experimental data.
An Investigation into the Effects of Initial Track Tension on Soft Ground Mobility of Tracked Vehicles Using an Advanced Computer Simulation Model
Authors: Wong J Y , Huang Wei
Published: June 2006

This paper describes the results of a detailed investigation into the effects of initial track tension (i.e. the tension in the track system when the vehicle is stationary on a level, hard surface) on soft ground mobility of tracked vehicles. The investigation was carried out using the latest version of an advanced computer simulation model, known as NTVPM, developed under the auspices of Vehicle Systems Development Corporation. The results show that the initial track tension has significant effects on the peak normal pressure and mean maximum pressure on the track-terrain interface, sinkage of the track, and the drawbar pull and tractive efficiency of a vehicle on unprepared terrain. The impact of initial track tension on tractive performance is however dependent upon vehicle design features, including suspension characteristics. This investigation demonstrates that the simulation model NTVPM can play a significant role in the detailed evaluation of the design of tracked vehicles from a traction perspective.