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Sample records for aging mechanisms expected

  1. Primary Care Clinician Expectations Regarding Aging

    ERIC Educational Resources Information Center

    Davis, Melinda M.; Bond, Lynne A.; Howard, Alan; Sarkisian, Catherine A.

    2011-01-01

    Purpose: Expectations regarding aging (ERA) in community-dwelling older adults are associated with personal health behaviors and health resource usage. Clinicians' age expectations likely influence patients' expectations and care delivery patterns; yet, limited research has explored clinicians' age expectations. The Expectations Regarding Aging…

  2. Changing expectancies: cognitive mechanisms and context effects.

    PubMed

    Wiers, Reinout W; Wood, Mark D; Darkes, Jack; Corbin, William R; Jones, Barry T; Sher, Kenneth J

    2003-02-01

    This article presents the proceedings of a symposium at the 2002 RSA Meeting in San Francisco, organized by Reinout W. Wiers and Mark D. Wood. The symposium combined two topics of recent interest in studies of alcohol expectancies: cognitive mechanisms in expectancy challenge studies, and context-related changes of expectancies. With increasing recognition of the substantial role played by alcohol expectancies in drinking, investigators have begun to develop and evaluate expectancy challenge procedures as a potentially promising new prevention strategy. The two major issues addressed in the symposium were whether expectancy challenges result in changes in expectancies that mediate intervention (outcome relations), and the influence of simulated bar environments ("bar labs," in which challenges are usually done) on expectancies. The presentations were (1) An introduction, by Jack Darkes; (2) Investigating the utility of alcohol expectancy challenge with heavy drinking college students, by Mark D. Wood; (3) Effects of an expectancy challenge on implicit and explicit expectancies and drinking, by Reinout W. Wiers; (4) Effects of graphic feedback and simulated bar assessments on alcohol expectancies and consumption, by William R. Corbin; (5) Implicit alcohol associations and context, by Barry T Jones; and (6) A discussion by Kenneth J. Sher, who pointed out that it is important not only to study changes of expectancies in the paradigm of an expectancy challenge but also to consider the role of changing expectancies in natural development and in treatments not explicitly aimed at changing expectancies.

  3. Brain mechanisms supporting violated expectations of pain.

    PubMed

    Zeidan, Fadel; Lobanov, Oleg V; Kraft, Robert A; Coghill, Robert C

    2015-09-01

    The subjective experience of pain is influenced by interactions between experiences, future predictions, and incoming afferent information. Expectations of high pain can exacerbate pain, whereas expectations of low pain during a consistently noxious stimulus can produce significant reductions in pain. However, the brain mechanisms associated with processing mismatches between expected and experienced pain are poorly understood, but are important for imparting salience to a sensory event to override erroneous top-down expectancy-mediated information. This investigation examined pain-related brain activation when expectations of pain were abruptly violated. After conditioning participants to cues predicting low or high pain, 10 incorrectly cued stimuli were administered across 56 stimulus trials to determine whether expectations would be less influential on pain when there is a high discordance between prestimulus cues and corresponding thermal stimulation. Incorrectly cued stimuli produced pain ratings and pain-related brain activation consistent with placebo analgesia, nocebo hyperalgesia, and violated expectations. Violated expectations of pain were associated with activation in distinct regions of the inferior parietal lobe, including the supramarginal and angular gyrus, and intraparietal sulcus, the superior parietal lobe, cerebellum, and occipital lobe. Thus, violated expectations of pain engage mechanisms supporting salience-driven sensory discrimination, working memory, and associative learning processes. By overriding the influence of expectations on pain, these brain mechanisms are likely engaged in clinical situations in which patients' unrealistic expectations of pain relief diminish the efficacy of pain treatments. Accordingly, these findings underscore the importance of maintaining realistic expectations to augment the effectiveness of pain management.

  4. Brain Mechanisms Supporting Violated Expectations of Pain

    PubMed Central

    Zeidan, Fadel; Lobanov, Oleg V.; Kraft, Robert A.; Coghill, Robert C.

    2015-01-01

    The subjective experience of pain is influenced by interactions between prior experiences, future predictions and incoming afferent information. Expectations of high pain can exacerbate pain while expectations of low pain during a consistently noxious stimulus can produce significant reductions in pain. However, the brain mechanisms associated with processing mismatches between expected and experienced pain are poorly understood, but are important for imparting salience to a sensory event in order to override erroneous top-down expectancy-mediated information. The present investigation examined pain-related brain activation when expectations of pain were abruptly violated. After conditioning participants to cues predicting low or high pain, ten incorrectly cued stimuli were administered across 56 stimulus trials to determine if expectations would be less influential on pain when there is a high discordance between pre-stimulus cues and corresponding thermal stimulation. Incorrectly cued stimuli produced pain ratings and pain-related brain activation consistent with placebo analgesia, nocebo hyperalgesia, and violated expectations. Violated expectations of pain were associated with activation in distinct regions of the inferior parietal lobe, including the supramarginal and angular gyrus, and intraparietal sulcus, the superior parietal lobe, cerebellum and occipital lobe. Thus, violated expectations of pain engage mechanisms supporting salience-driven sensory discrimination, working memory, and associative learning processes. By overriding the influence of expectations on pain, these brain mechanisms are likely engaged in clinical situations where patients’ unrealistic expectations for pain relief diminish the efficacy of pain treatments. Accordingly, these findings underscore the importance of maintaining realistic expectations to augment the effectiveness of pain management. PMID:26083664

  5. The Malleability of Possible Selves and Expectations regarding Aging

    ERIC Educational Resources Information Center

    Bardach, Shoshana H.; Gayer, Christopher C.; Clinkinbeard, Tiffanie; Zanjani, Faika; Watkins, John F.

    2010-01-01

    Many people are apprehensive about old age and their future years. This pilot study sought to improve participants' sense of possibility in, and expectations for, old age. Students and middle-aged volunteers completed a survey including the Expectations Regarding Aging 38-item questionnaire (ERA-38) and a possible-selves questionnaire before and…

  6. Age differences in expected satisfaction with life in retirement.

    PubMed

    Gutierrez, Helen C; Hershey, Douglas A

    2014-01-01

    Research on expected quality of life in retirement has focused on the perceptions of individuals either living in retirement or nearing retirement age. In this article, data are reported that examine expectations of (future) retirement quality of life among younger and middle-aged adults. Toward this end, a new scale--the Satisfaction with Life in Retirement Scale--is introduced. As part of the study, a pair of age-specific, theoretically-driven, hierarchically-structured path models were tested in which individuals' perceptions of future retirement satisfaction were regressed on indicators of financial knowledge, future time perspective, financial risk tolerance, and parental financial values. Models from both age groups were successful in accounting for variability in perceptions of future retirement satisfaction; however, age differences in the model were observed. The results of this investigation have implications for retirement counselors and intervention specialists who seek to cultivate positive perceptions of late life among individuals of different ages.

  7. Who are you expecting? Biases in face perception reveal prior expectations for sex and age.

    PubMed

    Watson, Tamara Lea; Otsuka, Yumiko; Clifford, Colin Walter Giles

    2016-01-01

    A person's appearance contains a wealth of information, including indicators of their sex and age. Because first impressions can set the tone of subsequent relationships, it is crucial we form an accurate initial impression. Yet prior expectation can bias our decisions: Studies have reported biases to respond "male" when asked to report a person's sex from an image of their face and to place their age closer to their own. Perceptual expectation effects and cognitive response biases may both contribute to these inaccuracies. The current research used a Bayesian modeling approach to establish the perceptual biases involved when estimating the sex and age of an individual from their face. We demonstrate a perceptual bias for male and older faces evident under conditions of uncertainty. This suggests the well-established male bias is perceptual in origin and may be impervious to cognitive control. In comparison, the own age anchor effect is not operationalized at the perceptual level: The perceptual expectation is for a face of advanced age. Thus, distinct biases in the estimation of age operate at the perceptual and cognitive levels. PMID:26842858

  8. The aging process and potential interventions to extend life expectancy

    PubMed Central

    Tosato, Matteo; Zamboni, Valentina; Ferrini, Alessandro; Cesari, Matteo

    2007-01-01

    Aging is commonly defined as the accumulation of diverse deleterious changes occurring in cells and tissues with advancing age that are responsible for the increased risk of disease and death. The major theories of aging are all specific of a particular cause of aging, providing useful and important insights for the understanding of age-related physiological changes. However, a global view of them is needed when debating of a process which is still obscure in some of its aspects. In this context, the search for a single cause of aging has recently been replaced by the view of aging as an extremely complex, multifactorial process. Therefore, the different theories of aging should not be considered as mutually exclusive, but complementary of others in the explanation of some or all the features of the normal aging process. To date, no convincing evidence showing the administration of existing “anti-aging” remedies can slow aging or increase longevity in humans is available. Nevertheless, several studies on animal models have shown that aging rates and life expectancy can be modified. The present review provides an overlook of the most commonly accepted theories of aging, providing current evidence of those interventions aimed at modifying the aging process. PMID:18044191

  9. Arts and Ageing; Life Expectancy of Historical Artists in the Low Countries

    PubMed Central

    Engelaer, Frouke M.; Bijwaard, Govert E.; van Bodegom, David; Westendorp, Rudi G. J.; van Poppel, Frans W. A.

    2014-01-01

    Practising arts has been linked to lowering stress, anxiety and blood pressure. These mechanisms are all known to affect the ageing process. Therefore, we examine the relation between long-term involvement in arts and life expectancy at age 50 (LE50), in a cohort of 12,159 male acoustic, literary and visual artists, who were born between 1700 and 1899 in the Low Countries. We compared the life expectancy at age 50 of the various artists with the elite and middle class of that time. In the birth cohorts before 1850, acoustic (LE50:14.5–19.5) and literary artists (LE50:17.8–20.8) had a similar life expectancy at age 50 compared to the elite (LE50:18.0–19.0). Only visual artists (LE50:15.5–17.1) had a lower life expectancy at age 50 compared to the elite at that time. For the most recent birth cohorts from 1850 through 1899, the comparison between artists and the elite reversed and acoustic and literary artist had a lower life expectancy at age 50, while visual artists enjoyed a similar life expectancy at age 50. Although artists belonged to the middle socioeconomic class and lived predominantly in urban areas with poor living conditions, they had a life expectancy similar to the elite population. This is in line with observed favourable effects of practicing arts on health in the short-term. From our historical analysis, we hypothesize several mechanisms through which artistic creativity could influence the ageing process and life expectancy. These hypotheses, however, should be formally tested before any definite conclusions on effects of arts on ageing can be drawn. PMID:24416148

  10. [Life expectancy at older ages and alternative approach to aging measurement (the case of St. Petersburg)].

    PubMed

    Kozlov, L V; Safarova, G L; Lisenenkov, F I; Mikhaĭlova, O N

    2009-01-01

    St. Petersburg Institute of Bioregulation and Gerontology, NWB of RAMS, 3 pr. Dinamo, St. Petersburg 197110; For St. Petersburg, aging issues are of great importance as values of many aging indicators for St. Petersburg are higher than for Russia as a whole. Taper aims at analyzing the dynamics of life expectancy at older ages and comparing traditional (proportion of the elderly, average age, median age) and new (proportion of population with a remaining life expectancy 15 years or less, population average remaining years of life) aging indicators for St. Petersburg in 1990-2006.

  11. Recession and Expected Retirement Age: Another Look at the Evidence

    PubMed Central

    Szinovacz, Maximiliane E.

    2014-01-01

    Purpose: This article expands on earlier analyses that assessed whether the recent recession influenced retirement expectations. Design and Methods: Acknowledging that planning for retirement is a complex process influenced by personal preferences, resources, economic factors, institutional policies, and social norms, we test more comprehensive models than those used in previous studies, using data from the 2006 and 2008 waves (Waves 8 and 9) of the Health and Retirement Study. Results: Our results confirm that economic changes impinge on retirement expectations, but they also show stronger influences of other factors such as debts and the work environment. Implications: As the baby boom cohorts approach retirement age, it will be important to better understand how workers consider macro factors such as the state of the economy and firm-level factors and personal finances when planning for retirement. PMID:23448961

  12. Coronary artery circumferential stress: departure from Laplace expectations with aging.

    PubMed

    Tracy, Richard E; Eigenbrodt, Marsha L

    2009-09-15

    Normal, youthful arteries generally maintain constant radius/wall thickness ratios, with the relationship being described by the Laplace Law. Whether this relationship is maintained during aging is unclear. This study first examines the Laplace relationships in postmortem coronary arteries using a novel method to correct measurements for postmortem artifacts, uses data from the literature to provide preliminary validation, and then describes histology associated with low circumferential stress. Measurements of radius and wall thickness, taken at sites free from atheromas, were used with national population estimates of age-, gender-, and race-specific blood pressure data to calculate average circumferential stress within demographic groups. The estimated circumferential stress at ages 55-74 years was about half that at ages 18-24 years because of a disproportionate increase of wall thickness relative to artery radius at older ages, violating the expected relationships described by the Laplace Law. Arteries with low circumferential stress (estimated at sites distant from atherosclerosis) had more necrotic atheromas than arteries with high stress. At sites with low stress and intimal thickening, smooth muscle cells (SMCs) were spread apart, thereby diminishing their density within both the intima and media. Thus, older arteries displayed both low circumferential stress and abundant matrix of low cellularity microscopically. Such changes might alter SMC-matrix interactions.

  13. Neural mechanisms of ageing and cognitive decline

    PubMed Central

    Bishop, Nicholas A.; Lu, Tao; Yankner, Bruce A.

    2010-01-01

    During the past century, treatments for the diseases of youth and middle age have helped raise life expectancy significantly. However, cognitive decline has emerged as one of the greatest health threats of old age, with nearly 50% of adults over the age of 85 afflicted with Alzheimer’s disease. Developing therapeutic interventions for such conditions demands a greater understanding of the processes underlying normal and pathological brain ageing. Recent advances in the biology of ageing in model organisms, together with molecular and systems-level studies of the brain, are beginning to shed light on these mechanisms and their potential roles in cognitive decline. PMID:20336135

  14. 29 CFR Appendix D to Part 4044 - Tables Used To Determine Expected Retirement Age

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 29 Labor 9 2013-07-01 2013-07-01 false Tables Used To Determine Expected Retirement Age D Appendix... 4044—Tables Used To Determine Expected Retirement Age Table I-13—Selection of Retirement Rate Category... II-B. 3 Table II-C. Table II-A—Expected Retirement Ages for Individuals in the Low...

  15. 29 CFR Appendix D to Part 4044 - Tables Used To Determine Expected Retirement Age

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 29 Labor 9 2010-07-01 2010-07-01 false Tables Used To Determine Expected Retirement Age D Appendix... 4044—Tables Used To Determine Expected Retirement Age TABLE I-10—Selection of Retirement Rate Category... II-B. 3 Table II-C. Table II-A—Expected Retirement Ages for Individuals in the Low...

  16. 29 CFR Appendix D to Part 4044 - Tables Used To Determine Expected Retirement Age

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 29 Labor 9 2012-07-01 2012-07-01 false Tables Used To Determine Expected Retirement Age D Appendix... 4044—Tables Used To Determine Expected Retirement Age Table I-12— Selection of Retirement Rate Category... II-B. 3 Table II-C. Table II-A—Expected Retirement Ages for Individuals in the Low...

  17. 29 CFR Appendix D to Part 4044 - Tables Used To Determine Expected Retirement Age

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 29 Labor 9 2014-07-01 2014-07-01 false Tables Used To Determine Expected Retirement Age D Appendix... 4044—Tables Used To Determine Expected Retirement Age Table I-14—Selection of Retirement Rate Category... II-B. 3 Table II-C. Table II-A—Expected Retirement Ages for Individuals in the Low...

  18. Face-induced expectancies influence neural mechanisms of performance monitoring.

    PubMed

    Osinsky, Roman; Seeger, Jennifer; Mussel, Patrick; Hewig, Johannes

    2016-04-01

    In many daily situations, the consequences of our actions are predicted by cues that are often social in nature. For instance, seeing the face of an evaluator (e.g., a supervisor at work) may activate certain evaluative expectancies, depending on the history of prior encounters with that particular person. We investigated how such face-induced expectancies influence neurocognitive functions of performance monitoring. We recorded an electroencephalogram while participants completed a time-estimation task, during which they received performance feedback from a strict and a lenient evaluator. During each trial, participants first saw the evaluator's face before performing the task and, finally, receiving feedback. Therefore, faces could be used as predictive cues for the upcoming evaluation. We analyzed electrocortical signatures of performance monitoring at the stages of cue processing, task performance, and feedback reception. Our results indicate that, at the cue stage, seeing the strict evaluator's face results in an anticipatory preparation of fronto-medial monitoring mechanisms, as reflected by a sustained negative-going amplitude shift (i.e., the contingent negative variation). At the performance stage, face-induced expectancies of a strict evaluation rule led to increases of early performance monitoring signals (i.e., frontal-midline theta power). At the final stage of feedback reception, violations of outcome expectancies differentially affected the feedback-related negativity and frontal-midline theta power, pointing to a functional dissociation between these signatures. Altogether, our results indicate that evaluative expectancies induced by face-cues lead to adjustments of internal performance monitoring mechanisms at various stages of task processing.

  19. Face-induced expectancies influence neural mechanisms of performance monitoring.

    PubMed

    Osinsky, Roman; Seeger, Jennifer; Mussel, Patrick; Hewig, Johannes

    2016-04-01

    In many daily situations, the consequences of our actions are predicted by cues that are often social in nature. For instance, seeing the face of an evaluator (e.g., a supervisor at work) may activate certain evaluative expectancies, depending on the history of prior encounters with that particular person. We investigated how such face-induced expectancies influence neurocognitive functions of performance monitoring. We recorded an electroencephalogram while participants completed a time-estimation task, during which they received performance feedback from a strict and a lenient evaluator. During each trial, participants first saw the evaluator's face before performing the task and, finally, receiving feedback. Therefore, faces could be used as predictive cues for the upcoming evaluation. We analyzed electrocortical signatures of performance monitoring at the stages of cue processing, task performance, and feedback reception. Our results indicate that, at the cue stage, seeing the strict evaluator's face results in an anticipatory preparation of fronto-medial monitoring mechanisms, as reflected by a sustained negative-going amplitude shift (i.e., the contingent negative variation). At the performance stage, face-induced expectancies of a strict evaluation rule led to increases of early performance monitoring signals (i.e., frontal-midline theta power). At the final stage of feedback reception, violations of outcome expectancies differentially affected the feedback-related negativity and frontal-midline theta power, pointing to a functional dissociation between these signatures. Altogether, our results indicate that evaluative expectancies induced by face-cues lead to adjustments of internal performance monitoring mechanisms at various stages of task processing. PMID:26527096

  20. Cognitive Skills and the Aging Brain: What to Expect.

    PubMed

    Howieson, Diane B

    2015-01-01

    Whether it's a special episode on the PBS series, "The Secret Life of the Brain" or an entire issue dedicated to the topic in the journal Science, a better understanding of the aging brain is viewed as a key to an improved quality of life in a world where people live longer. Despite dementia and other neurobiological disorders that are associated with aging, improved imaging has revealed that even into our seventies, our brains continue producing new neurons. Our author writes about how mental health functions react to the normal aging process, including why an aging brain may even form the basis for wisdom. PMID:27408669

  1. Better or Worse than Expected? Aging, Learning, and the ERN

    ERIC Educational Resources Information Center

    Eppinger, Ben; Kray, Jutta; Mock, Barbara; Mecklinger, Axel

    2008-01-01

    This study examined age differences in error processing and reinforcement learning. We were interested in whether the electrophysiological correlates of error processing, the error-related negativity (ERN) and the feedback-related negativity (FRN), reflect learning-related changes in younger and older adults. To do so, we applied a probabilistic…

  2. Explaining Optimistic Old Age Disability and Longevity Expectations

    ERIC Educational Resources Information Center

    Costa-Font, Joan; Costa-Font, Montserrat

    2011-01-01

    Biased health care decision making has been regarded as responsible for inefficient behaviours (for example, the limited insurance purchase). This paper empirically examines two sets of biases in the perception of old age disability and longevity. Particularly, we test for the existence of a so called cumulative bias and, secondly, a so called…

  3. Expectation in perceptual decision making: neural and computational mechanisms.

    PubMed

    Summerfield, Christopher; de Lange, Floris P

    2014-11-01

    Sensory signals are highly structured in both space and time. These structural regularities in visual information allow expectations to form about future stimulation, thereby facilitating decisions about visual features and objects. Here, we discuss how expectation modulates neural signals and behaviour in humans and other primates. We consider how expectations bias visual activity before a stimulus occurs, and how neural signals elicited by expected and unexpected stimuli differ. We discuss how expectations may influence decision signals at the computational level. Finally, we consider the relationship between visual expectation and related concepts, such as attention and adaptation.

  4. Longitudinal Change in Happiness during Aging: The Predictive Role of Positive Expectancies

    ERIC Educational Resources Information Center

    Holahan, Carole K.; Holahan, Charles J.; Velasquez, Katherine E.; North, Rebecca J.

    2008-01-01

    This study employed hierarchical linear modeling to document the time course of happiness across 20 years from average ages of 66 to 86 among 717 members of the Terman Study of the Gifted. In addition, the study examined the role of positive expectancies about aging, assessed at an average age of 61, in enhancing happiness in aging. The results…

  5. Chronological definitions and expectations of old age among young adults in Nigeria.

    PubMed

    Togonu-Bickersteth, F

    1987-01-01

    This article examines (1) chronological definition of old age and (2) expectations about old age held by young adults in Ile-Ife, Nigeria. Primary data consist of structured interviews of 113 persons aged 18 to 35. These were supplemented by secondary analysis of data collected from an earlier survey of 432 old persons in Ile-Ife. In respect of chronological definitions of old age, the observed patterns of definition confirm general tendencies reported by previous researchers in Western societies. Concerning expectations about old age, the data points to the centrality of the place of offspring in the definition of a good old age. The article concludes by noting that while chronological definition of old age may show similarity of patterns across cultures and therefore assume the semblance of universal laws, old age expectations are much more culturally specific because of their interdependence with the beliefs, norms, values and other socioeconomic patterns extant in a particular society.

  6. The effect of age and role information on expectations for big five personality traits.

    PubMed

    Wood, Dustin; Roberts, Brent W

    2006-11-01

    In four studies, the authors investigated the extent to which expectations for personality traits in age-graded roles correspond to patterns of personality trait change across the life course. In Studies 1 (N = 43) and 2 (N = 126), the authors examined the age-graded roles of high school student, college student, parent, and grandparent and found that expectations for how people behave in these age-graded roles showed strong parallels to the documented pattern of personality trait development and that this pattern of expectations was largely shared by younger and older participants. In Studies 3 (N = 252) and 4 (N = 123), the authors separated age and role information (e.g., marital, parental, and employment status) and found that people use both sources of information independently in forming expectations of others. The implications for understanding the interplay of expectations and personality trait development are discussed.

  7. What Do Children Know about Their Futures: Do Children's Expectations Predict Outcomes in Middle Age?

    ERIC Educational Resources Information Center

    Hallerod, Bjorn

    2011-01-01

    Are children's statements about their futures related to outcomes in middle age? In 1966 almost 13,500 children ages 12-13 were asked whether they thought their futures would be worse, similar or better as compared to others of their own age. It was shown that children with low, and surprisingly high, expectations did suffer from increased…

  8. Survey of Aging Veterans: A Study of the Means, Resources and Future Expectations of Veterans Aged 55 and Over.

    ERIC Educational Resources Information Center

    Veterans Administration, Washington, DC. Office of Information Management and Statistics.

    A national survey of the needs, resources, and future expectations of veterans aged 55 and over produced findings that the Veterans Administration (VA) will use over the next decade to plan facilities and programs to meet those needs. Findings indicated veterans had a higher educational level and were less likely to be at the lower end of the…

  9. Effects of Age Expectations on Oncology Social Workers' Clinical Judgment

    ERIC Educational Resources Information Center

    Conlon, Annemarie; Choi, Namkee G.

    2014-01-01

    Objective: This study examined the influence of oncology social workers' expectations regarding aging (ERA) and ERA with cancer (ERAC) on their clinical judgment. Methods: Oncology social workers (N = 322) were randomly assigned to one of four vignettes describing a patient with lung cancer. The vignettes were identical except for the…

  10. Middle-Aged Working Class Americans at Home. Changing Expectations of Manhood

    ERIC Educational Resources Information Center

    Shostak, Arthur B.

    1972-01-01

    Describes the changing role expectations of the middle-aged blue-collar male as a husband, lover, father, and son, from a formerly stereotyped Archie Bunker" type of role model to one that is aware of improved performance needed in these family roles. (AG)

  11. Epigenetic Mechanisms of Longevity and Aging.

    PubMed

    Sen, Payel; Shah, Parisha P; Nativio, Raffaella; Berger, Shelley L

    2016-08-11

    Aging is an inevitable outcome of life, characterized by progressive decline in tissue and organ function and increased risk of mortality. Accumulating evidence links aging to genetic and epigenetic alterations. Given the reversible nature of epigenetic mechanisms, these pathways provide promising avenues for therapeutics against age-related decline and disease. In this review, we provide a comprehensive overview of epigenetic studies from invertebrate organisms, vertebrate models, tissues, and in vitro systems. We establish links between common operative aging pathways and hallmark chromatin signatures that can be used to identify "druggable" targets to counter human aging and age-related disease. PMID:27518561

  12. Aging expectations are associated with physical activity and health among older adults of low socioeconomic status.

    PubMed

    Dogra, Shilpa; Al-Sahab, Ban; Manson, James; Tamim, Hala

    2015-04-01

    The purpose of the current study was to determine whether aging expectations (AE) are associated with physical activity participation and health among older adults of low socioeconomic status (SES). A cross-sectional analysis of a sample of 170 older adults (mean age 70.9 years) was conducted. Data on AE, physical activity, and health were collected using the 12 item Expectations Regarding Aging instrument, the Healthy Physical Activity Participation Questionnaire, and the Short Form-36, respectively. Adjusted linear regression models showed significant associations between AE and social functioning, energy/vitality, mental health, and self-rated general health, as well as physical activity. These results suggest that AE may help to better explain the established association between low SES, low physical activity uptake, and poor health outcomes among older adults.

  13. Epigenetic mechanisms of dietary restriction induced aging in Drosophila.

    PubMed

    Lian, Ting; Gaur, Uma; Yang, Deying; Li, Diyan; Li, Ying; Yang, Mingyao

    2015-12-01

    Aging is a long-standing problem that people are always interested in. Thus, it is critical to understand the underlying molecular mechanisms in aging and explore the most efficient method to extend life expectancy. To achieve this goal, a wide range of systems including cells, rodent models, budding yeast, worms and flies have been employed for decades. In recent years, the effect of dietary restriction (DR) on lifespan is in the prime focus. Although we have confirmed that reduced insulin and/or insulin-like growth factor (IGF) and the target of rapamycin (TOR) signaling can increase Drosophila lifespan; the precise molecular mechanisms and nutritional response landscape of diet-mediated aging is ambiguous. Epigenetic events have been considered as the major contributors to lifespan extension with response to DR. The role of DNA methylation in aging is well acknowledged in mammals and rodents where it has been shown to impact aging by regulating the transcription, though the mechanism of regulation is not limited to only transcription. In Drosophila, the contribution of methylation during DR in aging is definitely less explored. In this review, we will update the advances in mechanisms of DR, with a particular focus on methylation as an upcoming target for aging studies and discuss Drosophila as a powerful model to understand mechanisms of aging with response to diet.

  14. Estimating life expectancy using an age-cohort model in Taiwan.

    PubMed Central

    Lee, W C; Hsieh, R L

    1996-01-01

    OBJECTIVES: Life expectation is a valuable summary index in public health and actuarial science. The life expectancies published in the vital statistics, however, are derived from the "current" rather than from the "cohort" life table. The former is based on a strong assumption of constant mortality in the population, whereas the latter calls for a recording of the mortality experience of a group of individuals, which is often an impossible task. Thus, a method of calculating cohort life expectancy without actual follow up is much needed. METHODS: Estimation of cohort life expectancy was based on an age-cohort model. Mortality data for the male population in Taiwan from 1951 to 1990 are used to illustrate the methodology. RESULTS: The increment of life expectancy over time in Taiwan is actually steeper than was previously thought using the current life table technique. CONCLUSIONS: The method is easy to implement and the data required are the usual age and period cross classified mortality data. It warrants further investigation. PMID:8762391

  15. Age of pension eligibility, gains in life expectancy, and social policy.

    PubMed

    Denton, Frank T; Spencer, Byron G

    2011-01-01

    Canadians are living longer and retiring younger. When combined with the aging of the baby-boom generation, that means that the “inactive” portion of the population is increasing and there are concerns about possibly large increases in the burden of support on those who are younger. We model the impact of continued future gains in life expectancy on the size of the population that receives public pension benefits. We pay special attention to possible increases in the age of eligibility and the pension contribution rate that would maintain the publicly financed component of the retirement income security system.

  16. Mechanical properties of cells and ageing.

    PubMed

    Starodubtseva, Maria N

    2011-01-01

    Mechanical properties are fundamental properties of the cells and tissues of living organisms. The mechanical properties of a single cell as a biocomposite are determined by the interdependent combination of cellular components mechanical properties. Quantitative estimate of the cell mechanical properties depends on a cell state, method of measurement, and used theoretical model. Predominant tendency for the majority of cells with ageing is an increase of cell stiffness and a decrease of cell ability to undergo reversible large deformations. The mechanical signal transduction in old cells becomes less effective than that in young cells, and with ageing, the cells lose the ability of the rapid functional rearrangements of cellular skeleton. The article reviews the theoretical and experimental facts touching the age-related changes of the mechanical properties of cellular components and cells in the certain systems of an organism (the blood, the vascular system, the musculoskeletal system, the lens, and the epithelium). In fact, the cell mechanical parameters (including elastic modulii) can be useful as specific markers of cell ageing.

  17. Age-related characteristics of risky decision-making and progressive expectation formation.

    PubMed

    Kardos, Zsófia; Kóbor, Andrea; Takács, Ádám; Tóth, Brigitta; Boha, Roland; File, Bálint; Molnár, Márk

    2016-10-01

    During daily encounters, it is inevitable that people take risks. Investigating the sequential processing of risk hazards involve expectation formation about outcome contingencies. The present study aimed to explore risk behavior and its neural correlates in sequences of decision making, particularly in old age, which represents a critical period regarding risk-taking propensity. The Balloon Analogue Risk Task was used in an electrophysiological setting with young and elderly age groups. During the task each additional pump on a virtual balloon increased the likelihood of a balloon burst but also increased the chance to collect more reward. Event-related potentials associated with rewarding feedback were analyzed based on the forthcoming decisions (whether to continue or to stop) in order to differentiate between states of expectation towards gain or loss. In the young, the reward positivity ERP component increased as a function of reward contingencies with the largest amplitude for rewarding feedback followed by the decision to stop. In the elderly, however, reward positivity did not reflect the effect of reward structure. Behavioral indices of risk-taking propensity suggest that the performance of the young and the elderly were dissociable only with respect to response times: The elderly was characterized by hesitation and more deliberative decision making throughout the experiment. These findings signify that sequential tracking of outcome contingencies has a key role in cost-efficient action planning and progressive expectation formation.

  18. Age-related characteristics of risky decision-making and progressive expectation formation.

    PubMed

    Kardos, Zsófia; Kóbor, Andrea; Takács, Ádám; Tóth, Brigitta; Boha, Roland; File, Bálint; Molnár, Márk

    2016-10-01

    During daily encounters, it is inevitable that people take risks. Investigating the sequential processing of risk hazards involve expectation formation about outcome contingencies. The present study aimed to explore risk behavior and its neural correlates in sequences of decision making, particularly in old age, which represents a critical period regarding risk-taking propensity. The Balloon Analogue Risk Task was used in an electrophysiological setting with young and elderly age groups. During the task each additional pump on a virtual balloon increased the likelihood of a balloon burst but also increased the chance to collect more reward. Event-related potentials associated with rewarding feedback were analyzed based on the forthcoming decisions (whether to continue or to stop) in order to differentiate between states of expectation towards gain or loss. In the young, the reward positivity ERP component increased as a function of reward contingencies with the largest amplitude for rewarding feedback followed by the decision to stop. In the elderly, however, reward positivity did not reflect the effect of reward structure. Behavioral indices of risk-taking propensity suggest that the performance of the young and the elderly were dissociable only with respect to response times: The elderly was characterized by hesitation and more deliberative decision making throughout the experiment. These findings signify that sequential tracking of outcome contingencies has a key role in cost-efficient action planning and progressive expectation formation. PMID:27385088

  19. From stage to age in variable environments: life expectancy and survivorship.

    PubMed

    Tuljapurkar, Shripad; Horvitz, Carol C

    2006-06-01

    Stage-based demographic data are now available on many species of plants and some animals, and they often display temporal and spatial variability. We provide exact formulas to compute age-specific life expectancy and survivorship from stage-based data for three models of temporal variability: cycles, serially independent random variation, and a Markov chain. These models provide a comprehensive description of patterns of temporal variation. Our formulas describe the effects of cohort (birth) environmental condition on mortality at all ages, and of the effects on survivorship of environmental variability experienced over the course of life. This paper complements existing methods for time-invariant stage-based data, and adds to the information on population growth and dynamics available from stochastic demography. PMID:16869426

  20. From stage to age in variable environments: life expectancy and survivorship.

    PubMed

    Tuljapurkar, Shripad; Horvitz, Carol C

    2006-06-01

    Stage-based demographic data are now available on many species of plants and some animals, and they often display temporal and spatial variability. We provide exact formulas to compute age-specific life expectancy and survivorship from stage-based data for three models of temporal variability: cycles, serially independent random variation, and a Markov chain. These models provide a comprehensive description of patterns of temporal variation. Our formulas describe the effects of cohort (birth) environmental condition on mortality at all ages, and of the effects on survivorship of environmental variability experienced over the course of life. This paper complements existing methods for time-invariant stage-based data, and adds to the information on population growth and dynamics available from stochastic demography.

  1. Degradation mechanisms and accelerated aging test design

    SciTech Connect

    Clough, R L; Gillen, K T

    1985-01-01

    The fundamental mechanisms underlying the chemical degradation of polymers can change as a function of environmental stress level. When this occurs, it greatly complicates any attempt to use accelerated tests for predicting long-term material degradation behaviors. Understanding how degradation mechanisms can change at different stress levels facilitates both the design and the interpretation of aging tests. Oxidative degradation is a predominant mechanism for many polymers exposed to a variety of different environments in the presence of air, and there are two mechanistic considerations which are widely applicable to material oxidation. One involves a physical process, oxygen diffusion, as a rate-limiting step. This mechanism can predominate at high stress levels. The second is a chemical process, the time-dependent decomposition of peroxide species. This leads to chain branching and can become a rate-controlling factor at lower stress levels involving time-scales applicable to use environments. The authors describe methods for identifying the operation of these mechanisms and illustrate the dramatic influence they can have on the degradation behaviors of a number of polymer types. Several commonly used approaches to accelerated aging tests are discussed in light of the behaviors which result from changes in degradation mechanisms. 9 references, 4 figures.

  2. Characterizing mechanical effects of aging damage

    SciTech Connect

    Sewell, T.D.; Chen, S.P.; Schoonover, J.R.; Trent, B.C.; Howe, P.M.; Hjelm, R.P.; Browning, R.V.

    1998-12-01

    This is the final report of a two-year, Laboratory Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). The goal was to develop and apply several different experimental and theoretical/computational tools to better understand physical and chemical aging phenomena in plastic-bonded high explosives, and to develop a methodology for predicting the likely effects of aging on the mechanical properties of the composite based on input from these fundamental studies. Initial comparisons were done for spectra of fresh and aged Esane, as well as PBX-9501, and the authors found differences in the carbonyl region of the spectrum, which possibly reflect differences in hydrogen bonding due to aging phenomena. The micromechanical model of composites was extended to study various volume fractions of HMX with binders. The results showed that, as the binder fraction increases, there is a decrease in the maximum stress that can be supported but an increase in the percent strain at final fracture. A more realistic microstructural model was obtained through the use of a phase field model. Using this model, the authors have studied the microstructural evolution as a function of the grain boundary energy vs. misorientation relationship. The initial results indicate that there are some changes in the grain growth rate when the grain-boundary energy dependence on the angle is not constant. They also find that solute tends to segregate at the grain boundary and slows the grain growth kinetics.

  3. DNA methylation levels at individual age-associated CpG sites can be indicative for life expectancy

    PubMed Central

    Lin, Qiong; Weidner, Carola I.; Costa, Ivan G.; Marioni, Riccardo E.; Ferreira, Marcelo R. P.; Deary, Ian J.; Wagner, Wolfgang

    2016-01-01

    DNA-methylation (DNAm) levels at age-associated CpG sites can be combined into epigenetic aging signatures to estimate donor age. It has been demonstrated that the difference between such epigenetic age-predictions and chronological age is indicative for of all-cause mortality in later life. In this study, we tested alternative epigenetic signatures and followed the hypothesis that even individual age-associated CpG sites might be indicative for life-expectancy. Using a 99-CpG aging model, a five-year higher age-prediction was associated with 11% greater mortality risk in DNAm profiles of the Lothian Birth Cohort 1921 study. However, models based on three CpGs, or even individual CpGs, generally revealed very high offsets in age-predictions if applied to independent microarray datasets. On the other hand, we demonstrate that DNAm levels at several individual age-associated CpGs seem to be associated with life expectancy – e.g., at CpGs associated with the genes PDE4C and CLCN6. Our results support the notion that small aging signatures should rather be analysed by more quantitative methods, such as site-specific pyrosequencing, as the precision of age-predictions is rather low on independent microarray datasets. Nevertheless, the results hold the perspective that simple epigenetic biomarkers, based on few or individual age-associated CpGs, could assist the estimation of biological age. PMID:26928272

  4. Behavioral Autonomy Age Expectations among Mexican-Origin Mother-Daughter Dyads: An Examination of Within-Group Variability

    PubMed Central

    Bámaca-Colbert, Mayra Y.; Umaña-Taylor, Adriana J.; Espinosa-Hernández, Graciela; Brown, Ashley M.

    2011-01-01

    This study examined differences in behavioral autonomy age expectations between Mexican-origin mothers and their adolescent daughters (N = 319 dyads); variability in behavioral autonomy age expectations as a function of nativity and maternal educational attainment also was examined. Findings indicated significant differences between mothers and daughters such that mothers reported later expectations for the timing of behavioral autonomy than did daughters. Follow-up analyses indicated that findings appeared to be driven by maternal nativity, with dyads comprised of Mexico-born mothers reporting the latest age expectations for behavioral autonomy when compared with dyads comprised of U.S.-born mothers. Findings underscore the need to examine normative development among Latino adolescents and their families with a specific focus on how sociocultural characteristics can contribute to within-family differences. PMID:22093152

  5. How did the Elimination of the Earnings Test above the Normal Retirement Age affect Retirement Expectations?1

    PubMed Central

    Michaud, Pierre-Carl

    2010-01-01

    We look at the effect of the 2000 repeal of the earnings test above the normal retirement age on retirement expectations of workers in the Health and Retirement Study, aged 51 to 61 in 1992. For men, we find that those whose marginal wage rate increased when the earnings test was repealed, had the largest increase in the probability to work full-time past normal retirement age. We do not find significant evidence of effects of the repeal of the earnings test on the probability to work past age 62 or the expected claiming age. On the other hand, for those reaching the normal retirement age, deviations between the age at which Social Security benefits are actually claimed and the previously reported expected age are more negative in 2000 than in 1998. Since our calculations show that the tax introduced by the earnings test was small when accounting for actuarial benefit adjustments and differential mortality, our results suggest that although male workers form expectations in a way consistent with forward-looking behavior, they misperceive the complicated rules of the earnings test. Results for females suggest similar patterns but estimates are imprecise. PMID:21037938

  6. Do age-friendly characteristics influence the expectation to age in place? A comparison of low-income and higher income Detroit elders.

    PubMed

    Lehning, Amanda J; Smith, Richard J; Dunkle, Ruth E

    2015-03-01

    Currently there is limited evidence linking age-friendly characteristics to outcomes in elders. Using a representative sample of 1,376 adults aged 60 and older living in Detroit, this study examined the association between age-friendly social and physical environmental characteristics and the expectation to age in place, and the potential differences between low- and higher-income elders. Based on U.S. Environmental Protection Agency's (EPA) age-friendly guide, we identified six factors reflecting age-friendly characteristics. Logistic regression models indicated that regardless of income level only neighborhood problems were significantly associated with expecting to age in place. Low-income elders were more likely to expect to age in place than their higher-income counterparts, and it is unclear whether this resulted from a desire to remain in the home or that there is no place else to go. Future research should address the ways in which financial resources affect the choices, expectations, and outcomes of aging in place.

  7. Do Age-Friendly Characteristics Influence the Expectation to Age in Place? A Comparison of Low-Income and Higher Income Detroit Elders

    PubMed Central

    Lehning, Amanda J.; Smith, Richard J.; Dunkle, Ruth E.

    2015-01-01

    Currently there is limited evidence linking age-friendly characteristics to outcomes in elders. Using a representative sample of 1,376 adults aged 60 and older living in Detroit, this study examined the association between age-friendly social and physical environmental characteristics and the expectation to age in place, and the potential differences between low- and higher-income elders. Based on U.S. Environmental Protection Agency's (EPA) age-friendly guide, we identified six factors reflecting age-friendly characteristics. Logistic regression models indicated that regardless of income level only neighborhood problems were significantly associated with expecting to age in place. Low-income elders were more likely to expect to age in place than their higher-income counterparts, and it is unclear whether this resulted from a desire to remain in the home or that there is no place else to go. Future research should address the ways in which financial resources affect the choices, expectations, and outcomes of aging in place. PMID:24652879

  8. Aging and Neurodegeneration: A Tangle of Models and Mechanisms.

    PubMed

    Chakrabarti, Sasanka; Mohanakumar, Kochupurackal P

    2016-03-01

    The research on aging and age-related diseases, especially the neurodegenerative diseases, is on the fast track. However, the results have so far not been translated to actual benefit for the patients in terms of treatment or diagnosis of age-related degenerative diseases including those of the CNS. As far as the prevention of the cognitive decline during non-pathological aging is concerned, there is nothing much to offer other than calorie restriction and physical exercise. Needless to say, the benefits are not up to our expectations. However, over the years at the experimental level it has been possible to identify several cellular and molecular mechanisms that are intricately associated with aging in general and neurodegenerative diseases in particular. These include oxidative stress and altered redox-signaling, mitochondrial dysfunction, inflammation, proteotoxicity and altered gene expressions. These inter-dependent pathways mediate cellular senescence and often culminate in programmed cell death like apoptosis and autophagy, and in the context of brain these changes are manifested clinically as cognitive decline and pathologically as neurodegeneration. This special issue provides the readers with glimpses of this complex scenario from different angles primarily in the context of brain and also attempts to identify the potential drug targets against neurodegenerative diseases. PMID:27114843

  9. Aging and Neurodegeneration: A Tangle of Models and Mechanisms

    PubMed Central

    Chakrabarti, Sasanka; Mohanakumar, Kochupurackal P.

    2016-01-01

    The research on aging and age-related diseases, especially the neurodegenerative diseases, is on the fast track. However, the results have so far not been translated to actual benefit for the patients in terms of treatment or diagnosis of age-related degenerative diseases including those of the CNS. As far as the prevention of the cognitive decline during non-pathological aging is concerned, there is nothing much to offer other than calorie restriction and physical exercise. Needless to say, the benefits are not up to our expectations. However, over the years at the experimental level it has been possible to identify several cellular and molecular mechanisms that are intricately associated with aging in general and neurodegenerative diseases in particular. These include oxidative stress and altered redox-signaling, mitochondrial dysfunction, inflammation, proteotoxicity and altered gene expressions. These inter-dependent pathways mediate cellular senescence and often culminate in programmed cell death like apoptosis and autophagy, and in the context of brain these changes are manifested clinically as cognitive decline and pathologically as neurodegeneration. This special issue provides the readers with glimpses of this complex scenario from different angles primarily in the context of brain and also attempts to identify the potential drug targets against neurodegenerative diseases. PMID:27114843

  10. Are age-related trends in suicide rates associated with life expectancy and socio-economic factors?

    PubMed

    Shah, Ajit

    2009-01-01

    Background. A recent cross-national study reported that suicide rates increased, decreased or remained unchanged with increasing age in individual countries. The relationship between age-related trends in suicide rates and child mortality rates, life expectancy and socio-economic factors was examined. Methods. Countries with an increase, decrease and no change in suicide rates with increasing age were ascertained from an earlier study (Shah, 2007a, International Psychogeriatrics, 19, 1141), which analysed data from the World Health Organisation (WHO). The relationship between age-related trends in suicide rates and (i) child mortality rates, (ii) life expectancy and (iii) markers of socio-economic status (per capita gross national domestic product (GDP) and the Gini coeffcient) was examined using data from the WHO and the United Nations. Results. The main findings were: (i) child mortality rates were significantly lower in countries with an increase in suicide rates with increasing age when compared to countries without a change in suicide rates with increasing age in males; (ii) life expectancy was significantly higher in countries with an increase in suicide rates with increasing age when compared to countries without a change in suicide rates with increasing age in males; and (iii) the Gini coefficient was significantly lower in countries with an increase in suicide rates with increasing age when compared to countries without a change or a decline in suicide rates with increasing age in females. Conclusions. Potential explanations for these findings and the interaction of life expectancy and socio-economic factors with other factors that differentially influence suicide rates in different age and sex groups requires further examination. PMID:24946117

  11. Are age-related trends in suicide rates associated with life expectancy and socio-economic factors?

    PubMed

    Shah, Ajit

    2009-01-01

    Background. A recent cross-national study reported that suicide rates increased, decreased or remained unchanged with increasing age in individual countries. The relationship between age-related trends in suicide rates and child mortality rates, life expectancy and socio-economic factors was examined. Methods. Countries with an increase, decrease and no change in suicide rates with increasing age were ascertained from an earlier study (Shah, 2007a, International Psychogeriatrics, 19, 1141), which analysed data from the World Health Organisation (WHO). The relationship between age-related trends in suicide rates and (i) child mortality rates, (ii) life expectancy and (iii) markers of socio-economic status (per capita gross national domestic product (GDP) and the Gini coeffcient) was examined using data from the WHO and the United Nations. Results. The main findings were: (i) child mortality rates were significantly lower in countries with an increase in suicide rates with increasing age when compared to countries without a change in suicide rates with increasing age in males; (ii) life expectancy was significantly higher in countries with an increase in suicide rates with increasing age when compared to countries without a change in suicide rates with increasing age in males; and (iii) the Gini coefficient was significantly lower in countries with an increase in suicide rates with increasing age when compared to countries without a change or a decline in suicide rates with increasing age in females. Conclusions. Potential explanations for these findings and the interaction of life expectancy and socio-economic factors with other factors that differentially influence suicide rates in different age and sex groups requires further examination.

  12. Mechanisms of age-related macular degeneration

    PubMed Central

    Ambati, Jayakrishna; Fowler, Benjamin J.

    2012-01-01

    Age-related macular degeneration (AMD), a progressive condition that is untreatable in up to 90% of patients, is a leading cause of blindness in the elderly worldwide. The two forms of AMD, wet and dry, are classified based on the presence or absence of blood vessels that have disruptively invaded the retina, respectively. A detailed understanding of the molecular mechanisms underlying wet AMD has led to several robust FDA-approved therapies. In contrast, there are not any approved treatments for dry AMD. In this review, we provide insight into the critical effector pathways that mediate each form of disease. The interplay of immune and vascular systems for wet AMD, and the proliferating interest in hunting for gene variants to explain AMD pathogenesis, are placed in the context of the latest clinical and experimental data. Emerging models of dry AMD pathogenesis are presented, with a focus on DICER1 deficit and the toxic accumulation of retinal debris. A recurring theme that spans most aspects of AMD pathogenesis is defective immune modulation in the classically immune-privileged ocular haven. Interestingly, the latest advances in AMD research highlight common molecular disease pathways with other common neurodegenerations. Finally, the therapeutic potential of intervening at known mechanisms of AMD pathogenesis is discussed. PMID:22794258

  13. Epigenetic Mechanisms of the Aging Human Retina

    PubMed Central

    Pennington, Katie L.; DeAngelis, Margaret M.

    2015-01-01

    Degenerative retinal diseases, such as glaucoma, age-related macular degeneration, and diabetic retinopathy, have complex etiologies with environmental, genetic, and epigenetic contributions to disease pathology. Much effort has gone into elucidating both the genetic and the environmental risk factors for these retinal diseases. However, little is known about how these genetic and environmental risk factors bring about molecular changes that lead to pathology. Epigenetic mechanisms have received extensive attention of late for their promise of bridging the gap between environmental exposures and disease development via their influence on gene expression. Recent studies have identified epigenetic changes that associate with the incidence and/or progression of each of these retinal diseases. Therefore, these epigenetic modifications may be involved in the underlying pathological mechanisms leading to blindness. Further genome-wide epigenetic studies that incorporate well-characterized tissue samples, consider challenges similar to those relevant to gene expression studies, and combine the genome-wide epigenetic data with genome-wide genetic and expression data to identify additional potentially causative agents of disease are needed. Such studies will allow researchers to create much-needed therapeutics to prevent and/or intervene in disease progression. Improved therapeutics will greatly enhance the quality of life and reduce the burden of disease management for millions of patients living with these potentially blinding conditions. PMID:26966390

  14. The Intricate Interplay between Mechanisms Underlying Aging and Cancer.

    PubMed

    Piano, Amanda; Titorenko, Vladimir I

    2015-02-01

    Age is the major risk factor in the incidence of cancer, a hyperplastic disease associated with aging. Here, we discuss the complex interplay between mechanisms underlying aging and cancer as a reciprocal relationship. This relationship progresses with organismal age, follows the history of cell proliferation and senescence, is driven by common or antagonistic causes underlying aging and cancer in an age-dependent fashion, and is maintained via age-related convergent and divergent mechanisms. We summarize our knowledge of these mechanisms, outline the most important unanswered questions and suggest directions for future research.

  15. The temporal derivative of expected utility: a neural mechanism for dynamic decision-making.

    PubMed

    Zhang, Xian; Hirsch, Joy

    2013-01-15

    Real world tasks involving moving targets, such as driving a vehicle, are performed based on continuous decisions thought to depend upon the temporal derivative of the expected utility (∂V/∂t), where the expected utility (V) is the effective value of a future reward. However, the neural mechanisms that underlie dynamic decision-making are not well understood. This study investigates human neural correlates of both V and ∂V/∂t using fMRI and a novel experimental paradigm based on a pursuit-evasion game optimized to isolate components of dynamic decision processes. Our behavioral data show that players of the pursuit-evasion game adopt an exponential discounting function, supporting the expected utility theory. The continuous functions of V and ∂V/∂t were derived from the behavioral data and applied as regressors in fMRI analysis, enabling temporal resolution that exceeded the sampling rate of image acquisition, hyper-temporal resolution, by taking advantage of numerous trials that provide rich and independent manipulation of those variables. V and ∂V/∂t were each associated with distinct neural activity. Specifically, ∂V/∂t was associated with anterior and posterior cingulate cortices, superior parietal lobule, and ventral pallidum, whereas V was primarily associated with supplementary motor, pre and post central gyri, cerebellum, and thalamus. The association between the ∂V/∂t and brain regions previously related to decision-making is consistent with the primary role of the temporal derivative of expected utility in dynamic decision-making. PMID:22963852

  16. The risk of stillbirth and infant death by each additional week of expectant management stratified by maternal age

    PubMed Central

    Page, Jessica M.; Snowden, Jonathan M.; Cheng, Yvonne W.; Doss, Amy; Rosenstein, Melissa G.; Caughey, Aaron B.

    2016-01-01

    OBJECTIVE The objective of the study was to examine fetal/infant mortality by gestational age at term stratified by maternal age. STUDY DESIGN A retrospective cohort study was conducted using 2005 US national birth certificate data. For each week of term gestation, the risk of mortality associated with delivery was compared with composite mortality risk of expectant management. The expectant management measure included stillbirth and infant death. This expectant management risk was calculated to estimate the composite mortality risk with remaining pregnant an additional week by combining the risk of stillbirth during the additional week of pregnancy and infant death risk following delivery at the next week. Maternal age was stratified by 35 years or more compared with women younger than 35 years as well as subgroup analyses of younger than 20, 20–34, 35–39, or 40 years old or older. RESULTS The fetal/infant mortality risk of expectant management is greater than the risk of infant death at 39 weeks’ gestation in women 35 years old or older (15.2 vs 10.9 of 10,000, P < .05). In women younger than 35 years old, the risk of expectant management also exceeded that of infant death at 39 weeks (21.3 vs 18.8 of 10,000, P < .05). For women younger than 35 years old, the overall expectant management risk is influenced by higher infant death risk and does not rise significantly until 41 weeks compared with women 35 years old or older in which it increased at 40 weeks. CONCLUSION Risk varies by maternal age, and delivery at 39 weeks minimizes fetal/infant mortality for both groups, although the magnitude of the risk reduction is greater in older women. PMID:23707677

  17. AGING & HEALTH Expectations About Future Use Of Long-Term Services And Supports Vary By CurrentLiving Arrangement

    PubMed Central

    Henning-Smith, Carrie; Shippee, Tetyana

    2014-01-01

    Most Americans know little about options for long-term services and supports and underestimate their likely future needs for such assistance. Using data from the 2012 National Health Interview Survey, we examined expectations about future use of long-term services and supports among adults ages 40–65 and how these expectations varied by current living arrangement. We found differences by living arrangement in expectations about both future need for long-term services and supports and who would provide such care if needed. Respondents living with minor children were the least likely to expect to need long-term services and supports and to require paid care if the need arose. In contrast, respondents living alone were the most likely to expect that it was “very likely” that they would need long-term services and supports and to rely on paid care. Overall, we found a disconnect between expectations of use and likely future reality: 60 percent of respondents believed that they were unlikely to need long-term services and supports in the future, whereas the evidence suggests that nearly 70 percent of older adults will need them at some point. These findings both underscore the need for programs that encourage people to plan for long-term services and supports and indicate that information about living arrangements can be useful in developing and targeting such programs. PMID:25561642

  18. Age-related changes in semen quality characteristics and expectations of reproductive longevity in Duroc boars.

    PubMed

    Huang, Yu Hung; Lo, Ling Ling; Liu, Shyh Hwa; Yang, Tien Shuh

    2010-08-01

    Quadratic fitting was used to regress semen characteristics of 1441 samples consisting of 12-month collection from 58 Duroc boars against animal age varied from 10 to 80 months. Data was divided into two groups of cool (14.0-22.7 degrees C, RH 81.5%) and hot season (22.9-29.9 degrees C, RH 86.6%), to test effects of age, season and their interactions. Results revealed that young boars of around 1 year old could endure the hot season. The endurance gradually diminished as animals grew. In the hot season animals exhibited peak performance at age around 33 month and it remained for 1 month, while cool-season kept boars could last for 48 months from 16 months old onward. The reproductive longevity should be 51 month in a subtropical environment and it may extend to 70 month if heat stress can be avoided. The estimated total sperm contribution of a Duroc boar would be 1.8 times more when kept below 22 degrees C than in a natural subtropical environment. It is concluded that to maintain Duroc boars as semen donor to at least 4 years of age is feasible in a subtropical environment and boar longevity could reach 6 years old if well kept in a temperate region. PMID:20662811

  19. Genetic contribution to aging: deleterious and helpful genes define life expectancy.

    PubMed

    Lao, J I; Montoriol, C; Morer, I; Beyer, K

    2005-12-01

    For the best understanding of aging, we must consider a genetic pool in which genes with negative effects (deleterious genes that shorten the life span) interact with genes with positive effects (helpful genes that promote longevity) in a constant epistatic relationship that results in a modulation of the final expression under particular environmental influences. Examples of deleterious genes affecting aging (predisposition to early-life pathology and disease) are those that confer risk for developing vascular disease in the heart, brain, or peripheral vessels (APOE, ACE, MTFHR, and mutation at factor II and factor V genes), a gene associated with sporadic late-onset Alzheimer's disease (APOE E4), a polymorphism (COLIA1 Sp1) associated with an increased fracture risk, and several genetic polymorphisms involved in hormonal metabolism that affect adverse reactions to estrogen replacement in postmenopausal women. In summary, the process of aging can be regarded as a multifactorial trait that results from an interaction between stochastic events and sets of epistatic alleles that have pleiotropic age-dependent effects. Lacking those alleles that predispose to disease and having the longevity-enabling genes (those beneficial genetic variants that confer disease resistance) are probably both important to such a remarkable survival advantage.

  20. Molecular mechanisms of proteasome plasticity in aging

    PubMed Central

    Rodriguez, Karl; Gaczynska, Maria; Osmulski, Pawel A.

    2010-01-01

    The ubiquitin-proteasome pathway plays a crucial role in regulation of intracellular protein turnover. Proteasome, the central protease of the pathway, encompasses multisubunit assemblies sharing a common catalytic core supplemented by regulatory modules and localizing to different subcellular compartments. To better comprehend age-related functions of the proteasome we surveyed content, composition and catalytic properties of the enzyme in cytosolic, microsomal and nuclear fractions. obtained from mouse livers subjected to organismal aging. We found that during aging subunit composition and subcellular distribution of proteasomes changed without substantial alterations in the total level of core complexes. We observed that the general decline in proteasomes functions was limited to nuclear and cytosolic compartments. Surprisingly, the observed changes in activity and specificity were linked to the amount of the activator module and distinct composition of the catalytic subunits. In contrast, activity, specificity and composition of the microsomal-associated proteasomes remained mostly unaffected by aging; however their relative contribution to the total activity was substantially elevated. Unexpectedly, the nuclear proteasomes were affected most profoundly by aging possibly triggering significant changes in cellular signaling and transcription. Collectively, the data indicate an age-related refocusing of proteasome from the compartment specific functions towards general protein maintenance. PMID:20080121

  1. Parental Spending on School-Age Children: Structural Stratification and Parental Expectation

    PubMed Central

    Hao, Lingxin; Yeung, Wei-Jun Jean

    2015-01-01

    As consumption expenditures are increasingly recognized as direct measures of children’s material well-being, they provide new insights into the process of intergenerational transfers from parents to children. Little is known, however, about how parents allocate financial resources to individual children. To fill this gap, we develop a conceptual framework based on stratification theory, human capital theory, and the child-development perspective; exploit unique child-level expenditure data from Child Supplements of the PSID; and employ quantile regression to model the distribution of parental spending on children. Overall, we find strong evidence supporting our hypotheses regarding the effects of socioeconomic status (SES), race, and parental expectation. Our nuanced estimates suggest that (1) parental education, occupation, and family income have differential effects on parental spending, with education being the most influential determinant; (2) net of SES, race continues to be a significant predictor of parental spending on children; and (3) parental expectation plays a crucial role in determining whether parents place a premium on child development in spending and how parents prioritize different categories of spending. PMID:25933638

  2. Age Related Decline in Postural Control Mechanisms.

    ERIC Educational Resources Information Center

    Stelmach, George E.; And Others

    1989-01-01

    Studied voluntary and reflexive mechanisms of postural control of young (N=8) and elderly (N=8) adults through measurement of reflexive reactions to large-fast and small-slow ankle rotation postural disturbances. Found reflexive mechanisms relatively intact for both groups although elderly appeared more disadvantaged when posture was under the…

  3. Cell-Nonautonomous Mechanisms Underlying Cellular and Organismal Aging.

    PubMed

    Medkour, Younes; Svistkova, Veronika; Titorenko, Vladimir I

    2016-01-01

    Cell-autonomous mechanisms underlying cellular and organismal aging in evolutionarily distant eukaryotes have been established; these mechanisms regulate longevity-defining processes within a single eukaryotic cell. Recent findings have provided valuable insight into cell-nonautonomous mechanisms modulating cellular and organismal aging in eukaryotes across phyla; these mechanisms involve a transmission of various longevity factors between different cells, tissues, and organisms. Herein, we review such cell-nonautonomous mechanisms of aging in eukaryotes. We discuss the following: (1) how low molecular weight transmissible longevity factors modulate aging and define longevity of cells in yeast populations cultured in liquid media or on solid surfaces, (2) how communications between proteostasis stress networks operating in neurons and nonneuronal somatic tissues define longevity of the nematode Caenorhabditis elegans by modulating the rates of aging in different tissues, and (3) how different bacterial species colonizing the gut lumen of C. elegans define nematode longevity by modulating the rate of organismal aging.

  4. Factors of skin ageing share common mechanisms.

    PubMed

    Giacomoni, P U; Rein, G

    2001-01-01

    Ageing has been defined as the accumulation of molecular modifications which manifest as macroscopic clinical changes. Human skin, unique among mammalians insofar as it is deprived of fur, is particularly sensitive to environmental stress. Major environmental factors have been recognized to induce modifications of the morphological and biophysical properties of the skin. Metabolites from ingested or inhaled substances do affect skin, which is also sensitive to endogenous hormone levels. Factors as diverse as ultraviolet radiation, atmospheric pollution, wounds, infections, traumatisms, anoxya, cigarette smoke, and hormonal status have a role in increasing the rate of accumulation of molecular modifications and have thus been termed 'factors of ageing'. All these factors share as a common feature, the capability to directly or indirectly induce one of the steps of the micro-inflammatory cycle, which includes the expression of ICAM-1 in endothelial cells. This triggers a process leading to the accumulation of damages in the skin resulting in skin ageing since ICAM-1 expression provokes recruitment and diapedesis of circulating immune cells, which digest the extracellular matrix (ECM) by secreting collagenases, myeloperoxidases and reactive oxygen species. The activation of these lytic processes provokes random damage to resident cells, which in turn secrete prostaglandines and leukotrienes. These signaling molecules induce the degranulation of resident mast cells which release the autacoid histamine and the cytokine TNF-alpha thus activating endothelial cells lining adjacent capillaries which release P-selectin and synthesize ICAM-1. This closes a self-maintained micro-inflammatory cycle, which results in the accumulation of ECM damage, i.e. skin aging. In this paper we review the evidence that two factors able to induce macroscopical and molecular modifications in the skin, protein glycation and stretch, activate the micro-inflammatory cycle. We further present

  5. Treatment of Chronic Hepatitis C in the Aged – Does It Impact Life Expectancy? A Decision Analysis

    PubMed Central

    Maor, Yaakov; Malnick, Stephen D. H.; Melzer, Ehud; Leshno, Moshe

    2016-01-01

    Background and Aims Recent studies have demonstrated that the efficacy of interferon-free direct-acting antiviral agents (DAAs) in patients over 70 is similar to that of younger age groups. Evidence continues to mount that life expectancy (LE) increases with successful treatment of hepatitis C (HCV) patients with advanced fibrosis. The evidence in older people is more limited. Our aim was to estimate the life year (LY) and quality-adjusted life year (QALY) gained by treatment of naïve patients with HCV as a function of patient's age and fibrosis stage. Methods We constructed a Markov model of HCV progression toward advanced liver disease. The primary outcome was LY and QALY saved. The model and the sustained virological response of HCV infected subjects treated with a fixed-dose combination of the NS5B polymerase inhibitor Sofosbuvir and the NS5A replication complex inhibitor Ledipasvir were based on the published literature and expert opinion. Results Generally, both the number of LY gained and QALY gained gradually decreased with advancing age but the rate of decline was slower with more advanced fibrosis stage. For patients with fibrosis stage F1, F2 and F3, LY gained dropped below six months if treated by the age of 55, 65 or 70 years, respectively, while for a patient with fibrosis stage F4, the gain was one LY if treated by the age of 75. The QALY gained for treated over untreated elderly were reasonably high even for those treated at early fibrosis stage. Conclusions There is a significant life expectancy benefit to HCV treatment in patients up to age 75 with advanced-stage fibrosis. PMID:27410963

  6. An Update on Inflamm-Aging: Mechanisms, Prevention, and Treatment.

    PubMed

    Xia, Shijin; Zhang, Xinyan; Zheng, Songbai; Khanabdali, Ramin; Kalionis, Bill; Wu, Junzhen; Wan, Wenbin; Tai, Xiantao

    2016-01-01

    Inflamm-aging is a challenging and promising new branch of aging-related research fields that includes areas such as immunosenescence. Increasing evidence indicates that inflamm-aging is intensively associated with many aging diseases, such as Alzheimer's disease, atherosclerosis, heart disease, type II diabetes, and cancer. Mounting studies have focused on the role of inflamm-aging in disease progression and many advances have been made in the last decade. However, the underlying mechanisms by which inflamm-aging affects pathological changes and disease development are still unclear. Here, we review studies of inflamm-aging that explore the concept, pathological features, mechanisms, intervention, and the therapeutic strategies of inflamm-aging in disease progression. PMID:27493973

  7. An Update on Inflamm-Aging: Mechanisms, Prevention, and Treatment

    PubMed Central

    Wu, Junzhen

    2016-01-01

    Inflamm-aging is a challenging and promising new branch of aging-related research fields that includes areas such as immunosenescence. Increasing evidence indicates that inflamm-aging is intensively associated with many aging diseases, such as Alzheimer's disease, atherosclerosis, heart disease, type II diabetes, and cancer. Mounting studies have focused on the role of inflamm-aging in disease progression and many advances have been made in the last decade. However, the underlying mechanisms by which inflamm-aging affects pathological changes and disease development are still unclear. Here, we review studies of inflamm-aging that explore the concept, pathological features, mechanisms, intervention, and the therapeutic strategies of inflamm-aging in disease progression. PMID:27493973

  8. An Observational Study of Teachers' Expectancy Effects and Their Mediating Mechanisms.

    ERIC Educational Resources Information Center

    Crowe, Patricia B.

    The theory that teachers treat students from whom they expect superior achievement differently than those from whom they expect inferior performance is examined. Five ways of reacting on the part of the teacher are identified for the purpose of this study--teacher warmth, teacher feedback, teacher selection of materials, opportunity offered for…

  9. Smoking abstinence-related expectancies among American Indians, African Americans, and women: potential mechanisms of tobacco-related disparities.

    PubMed

    Hendricks, Peter S; Westmaas, J Lee; Ta Park, Van M; Thorne, Christopher B; Wood, Sabrina B; Baker, Majel R; Lawler, R Marsh; Webb Hooper, Monica; Delucchi, Kevin L; Hall, Sharon M

    2014-03-01

    Research has documented tobacco-related health disparities by race and gender. Prior research, however, has not examined expectancies about the smoking cessation process (i.e., abstinence-related expectancies) as potential contributors to tobacco-related disparities in special populations. This cross-sectional study compared abstinence-related expectancies between American Indian (n = 87), African American (n = 151), and White (n = 185) smokers, and between women (n = 231) and men (n = 270) smokers. Abstinence-related expectancies also were examined as mediators of race and gender relationships with motivation to quit and abstinence self efficacy. Results indicated that American Indians and African Americans were less likely than Whites to expect withdrawal effects, and more likely to expect that quitting would be unproblematic. African Americans also were less likely than Whites to expect smoking cessation interventions to be effective. Compared with men, women were more likely to expect withdrawal effects and weight gain. These expectancy differences mediated race and gender relationships with motivation to quit and abstinence self-efficacy. Findings emphasize potential mechanisms underlying tobacco-related health disparities among American Indians, African Americans, and women and suggest a number of specific approaches for targeting tobacco dependence interventions to these populations. PMID:23528192

  10. Low-Temperature Aging Mechanisms in U-6wt% Nb

    SciTech Connect

    Hsiung, L L

    2004-12-07

    Phase stability and aging mechanisms in a water-quenched (WQ) U-6wt% Nb (U-14at% Nb) alloy artificially aged at 200 C and naturally aged at ambient temperature for 15 years have been investigated and studied using Vickers-hardness measurement, X-ray diffraction (XRD) analysis, and transmission electron microscopy (TEM) techniques. Age hardening/softening phenomenon is recorded from the artificially aged samples based upon the microhardness measurement. The age hardening can be readily rationalized by the occurrence of fine-scaled Nb segregation, or spinodal decomposition, within the {alpha}'' domains, which results in the formation of a modulated structure containing nano-scaled Nb-rich and Nb-lean domains. Prolonged aging leads to age softening of the alloy by coarsening of the modulated structure. Chemical ordering, or disorder-order phase transformation, is found within the naturally aged alloy according to TEM observations of antiphase domain boundaries (APBs) and superlattice diffraction patterns. A possible superlattice structure for the ordered {alpha}'' phase observed in the naturally aged sample and underlying low-temperature aging mechanisms are proposed.

  11. Distinct Mechanisms of Impairment in Cognitive Ageing and Alzheimer's Disease

    ERIC Educational Resources Information Center

    Mapstone, Mark; Dickerson, Kathryn; Duffy, Charles J.

    2008-01-01

    Similar manifestations of functional decline in ageing and Alzheimer's disease obscure differences in the underlying cognitive mechanisms of impairment. We sought to examine the contributions of top-down attentional and bottom-up perceptual factors to visual self-movement processing in ageing and Alzheimer's disease. We administered a novel…

  12. Recursive expectation-maximization clustering: A method for identifying buffering mechanisms composed of phenomic modules

    NASA Astrophysics Data System (ADS)

    Guo, Jingyu; Tian, Dehua; McKinney, Brett A.; Hartman, John L.

    2010-06-01

    Interactions between genetic and/or environmental factors are ubiquitous, affecting the phenotypes of organisms in complex ways. Knowledge about such interactions is becoming rate-limiting for our understanding of human disease and other biological phenomena. Phenomics refers to the integrative analysis of how all genes contribute to phenotype variation, entailing genome and organism level information. A systems biology view of gene interactions is critical for phenomics. Unfortunately the problem is intractable in humans; however, it can be addressed in simpler genetic model systems. Our research group has focused on the concept of genetic buffering of phenotypic variation, in studies employing the single-cell eukaryotic organism, S. cerevisiae. We have developed a methodology, quantitative high throughput cellular phenotyping (Q-HTCP), for high-resolution measurements of gene-gene and gene-environment interactions on a genome-wide scale. Q-HTCP is being applied to the complete set of S. cerevisiae gene deletion strains, a unique resource for systematically mapping gene interactions. Genetic buffering is the idea that comprehensive and quantitative knowledge about how genes interact with respect to phenotypes will lead to an appreciation of how genes and pathways are functionally connected at a systems level to maintain homeostasis. However, extracting biologically useful information from Q-HTCP data is challenging, due to the multidimensional and nonlinear nature of gene interactions, together with a relative lack of prior biological information. Here we describe a new approach for mining quantitative genetic interaction data called recursive expectation-maximization clustering (REMc). We developed REMc to help discover phenomic modules, defined as sets of genes with similar patterns of interaction across a series of genetic or environmental perturbations. Such modules are reflective of buffering mechanisms, i.e., genes that play a related role in the maintenance

  13. Molecular Mechanisms of Biological Aging in Intervertebral Discs

    PubMed Central

    Vo, Nam V.; Hartman, Robert A.; Patil, Prashanti R.; Risbud, Makarand V.; Kletsas, Dimitris; Iatridis, James C.; Hoyland, Judith A.; Le Maitre, Christine L.; Sowa, Gwendolyn A.; Kang, James D.

    2016-01-01

    Advanced age is the greatest risk factor for the majority of human ailments, including spine-related chronic disability and back pain, which stem from age-associated intervertebral disc degeneration (IDD). Given the rapid global rise in the aging population, understanding the biology of intervertebral disc aging in order to develop effective therapeutic interventions to combat the adverse effects of aging on disc health is now imperative. Fortunately, recent advances in aging research have begun to shed light on the basic biological process of aging. Here we review some of these insights and organize the complex process of disc aging into three different phases to guide research efforts to understand the biology of disc aging. The objective of this review is to provide an overview of the current knowledge and the recent progress made to elucidate specific molecular mechanisms underlying disc aging. In particular, studies over the last few years have uncovered cellular senescence and genomic instability as important drivers of disc aging. Supporting evidence comes from DNA repair-deficient animal models that show increased disc cellular senescence and accelerated disc aging. Additionally, stress-induced senescent cells have now been well documented to secrete catabolic factors, which can negatively impact the physiology of neighboring cells and ECM. These along with other molecular drivers of aging are reviewed in depth to shed crucial insights into the underlying mechanisms of age-related disc degeneration. We also highlight molecular targets for novel therapies and emerging candidate therapeutics that may mitigate age-associated IDD. PMID:26890203

  14. Aging and emotional memory: cognitive mechanisms underlying the positivity effect.

    PubMed

    Spaniol, Julia; Voss, Andreas; Grady, Cheryl L

    2008-12-01

    Younger adults tend to remember negative information better than positive or neutral information (negativity bias). The negativity bias is reduced in aging, with older adults occasionally exhibiting superior memory for positive, as opposed to negative or neutral, information (positivity bias). Two experiments with younger (N=24 in Experiment 1, N=25 in Experiment 2; age range: 18-35 years) and older adults (N=24 in both experiments; age range: 60-85 years) investigated the cognitive mechanisms responsible for age-related differences in recognition memory for emotional information. Results from diffusion model analyses (R. Ratcliff, 1978) indicated that the effects of valence on response bias were similar in both age groups but that Age x Valence interactions emerged in memory retrieval. Specifically, older adults experienced greater overall familiarity for positive items than younger adults. We interpret this finding in terms of an age-related increase in the accessibility of positive information in long-term memory. PMID:19140656

  15. Hygrothermal ageing effect on mechanical properties of FRP laminates

    NASA Astrophysics Data System (ADS)

    Larbi, S.; Bensaada, R.; Bilek, A.; Djebali, S.

    2015-03-01

    The aim of this work is to study the effect of hygrothermal aging on mechanical properties of two composite materials (carbon fiber / epoxy and glass fiber E / vinylester). Two stratifications are studied for each material. Both materials are exposed to two different environments, the sea water and the deionized water at a temperature of 40°C. The kinetic of material absorption is plotted. We see an irreversible degradation of material caused by exposure time. The characterization of samples in the virgin state and the aged condition is achieved with three points bending tests. We can see significant loss of mechanical properties due to hygrothermal aging.

  16. Mechanisms of the anorexia of aging-a review.

    PubMed

    Wysokiński, Adam; Sobów, Tomasz; Kłoszewska, Iwona; Kostka, Tomasz

    2015-08-01

    Many, even healthy, older people fail to adequately regulate food intake and experience loss of weight. Aging-associated changes in the regulation of appetite and the lack of hunger have been termed as the anorexia of aging. The etiology of the anorexia of aging is multi-factorial and includes a combination of physiological changes associated with aging (decline in smell and taste, reduced central and peripheral drive to eat, delayed gastric emptying), pathological conditions (depression, dementia, somatic diseases, medications and iatrogenic interventions, oral-health status), and social factors (poverty, loneliness). However, exact mechanisms of the anorexia of aging remain to be elucidated. Many neurobiological mechanisms may be secondary to age-related changes in body composition and not associated with anorexia per se. Therefore, further studies on pathophysiological mechanisms of the anorexia of aging should employ accurate measurement of body fat and lean mass. The anorexia of aging is associated with protein-energy malnutrition, sarcopenia, frailty, functional deterioration, morbidity, and mortality. Since this symptom can lead to dramatic consequences, early identification and effective interventions are needed. One of the most important goals in the geriatric care is to optimize nutritional status of the elderly.

  17. National Health Expenditure Projections, 2015-25: Economy, Prices, And Aging Expected To Shape Spending And Enrollment.

    PubMed

    Keehan, Sean P; Poisal, John A; Cuckler, Gigi A; Sisko, Andrea M; Smith, Sheila D; Madison, Andrew J; Stone, Devin A; Wolfe, Christian J; Lizonitz, Joseph M

    2016-08-01

    Health spending growth in the United States for 2015-25 is projected to average 5.8 percent-1.3 percentage points faster than growth in the gross domestic product-and to represent 20.1 percent of the total economy by 2025. As the initial impacts associated with the Affordable Care Act's coverage expansions fade, growth in health spending is expected to be influenced by changes in economic growth, faster growth in medical prices, and population aging. Projected national health spending growth, though faster than observed in the recent history, is slower than in the two decades before the recent Great Recession, in part because of trends such as increasing cost sharing in private health insurance plans and various Medicare payment update provisions. In addition, the share of total health expenditures paid for by federal, state, and local governments is projected to increase to 47 percent by 2025. PMID:27411572

  18. National Health Expenditure Projections, 2015-25: Economy, Prices, And Aging Expected To Shape Spending And Enrollment.

    PubMed

    Keehan, Sean P; Poisal, John A; Cuckler, Gigi A; Sisko, Andrea M; Smith, Sheila D; Madison, Andrew J; Stone, Devin A; Wolfe, Christian J; Lizonitz, Joseph M

    2016-08-01

    Health spending growth in the United States for 2015-25 is projected to average 5.8 percent-1.3 percentage points faster than growth in the gross domestic product-and to represent 20.1 percent of the total economy by 2025. As the initial impacts associated with the Affordable Care Act's coverage expansions fade, growth in health spending is expected to be influenced by changes in economic growth, faster growth in medical prices, and population aging. Projected national health spending growth, though faster than observed in the recent history, is slower than in the two decades before the recent Great Recession, in part because of trends such as increasing cost sharing in private health insurance plans and various Medicare payment update provisions. In addition, the share of total health expenditures paid for by federal, state, and local governments is projected to increase to 47 percent by 2025.

  19. Functional Significance of Conflicting Age and Wealth Cross-Categorization: The Dominant Role of Categories That Violate Stereotypical Expectations

    PubMed Central

    Song, Jingjing; Zuo, Bin

    2016-01-01

    The purpose of the current study was to identify the functional significance of conflicting stereotypes and to identify the dominant category in such conflicts. In the present research we examined the conflicting crossed categories of age and wealth with regard to warmth and competence perceptions. It was found (Pilot Study and Study 1) that the old-rich targets presented a conflicting stereotype group in the perception of warmth, whereas young-poor targets presented a conflicting stereotype group in the perception of competence. In addition, the old stereotype dominated the warmth evaluation of old-rich targets, whereas the poor stereotype dominated the competence evaluation of young-poor targets. In Study 2, participants provided warmth and competence evaluations after they learned about the targets' behaviors which demonstrated high or low warmth and high or low competence. The results suggest that for the warmth evaluation of the old-rich target the category that did not match the behavior (i.e., contradicted the stereotype expectation) was more salient and drove judgments. However, the effect of stereotype expectation violation was not found in the competence evaluation of the young-poor target. The results are discussed in terms of their implications for understanding factors that activate and inhibit stereotyped perceptions.

  20. Distressed Mothers and Their Infants Use a Less Efficient Timing Mechanism in Creating Expectancies of Each Other's Looking Patterns

    ERIC Educational Resources Information Center

    Beebe, Beatrice; Badalamenti, Anthony; Jaffe, Joseph; Feldstein, Stanley; Marquette, Lisa; Helbraun, Elizabeth; Demetri-Friedman, Donna; Flaster, Caroline; Goodman, Patricia; Kaminer, Tammy; Kaufman-Balamuth, Limor; Putterman, Jill; Stepakoff, Shanee; Ellman, Lauren

    2008-01-01

    The prediction of events and the creation of expectancies about their time course is a crucial aspect of an infant's mental life, but temporal mechanisms underlying these predictions are obscure. Scalar timing, in which the ratio of mean durations to their standard deviations is held constant, enables a person to use an estimate of the mean for…

  1. Mechanical Properties and Corrosion Characteristics of Thermally Aged Alloy 22

    SciTech Connect

    Rebak, R B; Crook, P

    2002-05-30

    Alloy 22 (UNS N06022) is a candidate material for the external wall of the high level nuclear waste containers for the potential repository site at Yucca Mountain. In the mill-annealed (MA) condition, Alloy 22 is a single face centered cubic phase. When exposed to temperatures on the order of 600 C and above for times higher than 1 h, this alloy may develop secondary phases that reduce its mechanical toughness and corrosion resistance. The objective of this work was to age Alloy 22 at temperatures between 482 C and 760 C for times between 0.25 h and 6,000 h and to study the mechanical and corrosion performance of the resulting material. Aging was carried out using wrought specimens as well as gas tungsten arc welded (GTAW) specimens. Mechanical and corrosion testing was carried out using ASTM standards. Results show-that the higher the aging temperature and the longer the aging time, the lower the impact toughness of the aged material and the lower its corrosion resistance. However, extrapolating both mechanical and corrosion laboratory data predicts that Alloy 22 will remain corrosion resistant and mechanically robust for the projected lifetime of the waste container.

  2. Mechanisms Involved in the Aging-Induced Vascular Dysfunction

    PubMed Central

    El Assar, Mariam; Angulo, Javier; Vallejo, Susana; Peiró, Concepción; Sánchez-Ferrer, Carlos F.; Rodríguez-Mañas, Leocadio

    2012-01-01

    Vascular aging is a key process determining health status of aged population. Aging is an independent cardiovascular risk factor associated to an impairment of endothelial function, which is a very early and important event leading to cardiovascular disease. Vascular aging, formerly being considered an immutable and inexorable risk factor, is now viewed as a target process for intervention in order to achieve a healthier old age. A further knowledge of the mechanisms underlying the age-related vascular dysfunction is required to design an adequate therapeutic strategy to prevent or restore this impairment of vascular functionality. Among the proposed mechanisms that contribute to age-dependent endothelial dysfunction, this review is focused on the following aspects occurring into the vascular wall: (1) the reduction of nitric oxide (NO) bioavailability, caused by diminished NO synthesis and/or by augmented NO scavenging due to oxidative stress, leading to peroxynitrite formation (ONOO−); (2) the possible sources involved in the enhancement of oxidative stress; (3) the increased activity of vasoconstrictor factors; and (4) the development of a low-grade pro-inflammatory environment. Synergisms and interactions between all these pathways are also analyzed. Finally, a brief summary of some cellular mechanisms related to endothelial cell senescence (including telomere and telomerase, stress-induced senescence, as well as sirtuins) are implemented, as they are likely involved in the age-dependent endothelial dysfunction, as well as in the lower vascular repairing capacity observed in the elderly. Prevention or reversion of those mechanisms leading to endothelial dysfunction through life style modifications or pharmacological interventions could markedly improve cardiovascular health in older people. PMID:22783194

  3. Effects of aging on the mechanical behavior of human dentin.

    PubMed

    Arola, D; Reprogel, R K

    2005-06-01

    An experimental study on the mechanical behavior of human dentin and the influence of age was conducted. Beams with rectangular cross-section were sectioned from the coronal dentin of virgin extracted molars (N = 76) that were obtained from (N = 70) patients between 17 and 80 years of age. The beams were loaded in either quasi-static 4-point flexure or 4-point flexural fatigue to failure and the stiffness, strength and fatigue properties were evaluated. In characterizing the fatigue response the beams were divided into two age groups that were regarded as young (17 < or = age < or = 30, mean +/- std. dev. = 25 +/- 5 years) and old (50 < or = age < or = 80, mean +/- std. dev. = 64 +/- 9 years) dentin. Results from monotonic loading showed that both the flexural strength and strain to fracture of dentin decreased significantly with age. The fatigue life of dentin increased with a reduction in cyclic stress amplitude and the fatigue strength of young dentin was greater than that of old dentin at all cyclic stress amplitudes. The endurance strength of young dentin (at 10(7) cycles) was approximately 44 MPa, whereas the old dentin exhibited an endurance strength of approximately 23 MPa. Based on differences in the mechanical behavior and microscopic features of the fracture surfaces from the young and old specimens, aging appears to result in an increase in both the rate of damage initiation and propagation in dentin.

  4. Hot topics in epigenetic mechanisms of aging: 2011.

    PubMed

    Berdasco, María; Esteller, Manel

    2012-04-01

    Aging is a complex process that results in compromised biological functions of the organism and increased susceptibility to disease and death. Although the molecular basis of aging is currently being investigated in many experimental contexts, there is no consensus theory to fully explain the aging process. Epigenetic factors, including DNA methylation, histone modifications, and microRNA expression, may play central roles in controlling changes in gene expression and genomic instability during aging. In this Hot Topic review, we first examine the mechanisms by which these epigenetic factors contribute to aging in diverse eukaryotic species including experimental models of yeasts, worms, and mammals. In a second section, we will emphasize in the mammalian epigenetic alterations and how they may affect human longevity by altering stem cell function and/or somatic cell decline. The field of aging epigenetics is ripe with potential, but is still in its infancy, as new layers of complexity are emerging in the epigenetic network. As an example, we are only beginning to understand the relevance of non-coding genome to organism aging or the existence of an epigenetic memory with transgenerational inheritance. Addressing these topics will be fundamental for exploiting epigenetics phenomena as markers of aging-related diseases or as therapeutic targets.

  5. Neuronal mechanisms of motor learning are age dependent.

    PubMed

    Berghuis, Kelly M M; De Rond, Veerle; Zijdewind, Inge; Koch, Giacomo; Veldman, Menno P; Hortobágyi, Tibor

    2016-10-01

    There is controversy whether age-related neuroanatomical and neurophysiological changes in the central nervous system affect healthy old adults' abilities to acquire and retain motor skills. We examined the effects of age on motor skill acquisition and retention and potential underlying mechanisms by measuring corticospinal and intracortical excitability, using transcranial magnetic stimulation. Healthy young (n = 24, 22 years) and old (n = 22, 71 years) adults practiced a wrist flexion-extention visuomotor task or only watched the templates as an attentional control for 20 minutes. Old compared with young adults performed less well at baseline. Although the absolute magnitude of skill acquisition and retention was similar in the 2 age groups (age × intervention × time, p = 0.425), a comparison of baseline-similar age sub-groups revealed impaired skill acquisition but not retention in old versus young. Furthermore, the neuronal mechanisms differed as revealed by an opposite direction of associations in the age-groups between relative skill acquisition and intracortical facilitation during the task, and opposite changes during skill retention in corticospinal excitability at rest and during the task and intracortical inhibition during the task. PMID:27494184

  6. Neuronal mechanisms of motor learning are age dependent.

    PubMed

    Berghuis, Kelly M M; De Rond, Veerle; Zijdewind, Inge; Koch, Giacomo; Veldman, Menno P; Hortobágyi, Tibor

    2016-10-01

    There is controversy whether age-related neuroanatomical and neurophysiological changes in the central nervous system affect healthy old adults' abilities to acquire and retain motor skills. We examined the effects of age on motor skill acquisition and retention and potential underlying mechanisms by measuring corticospinal and intracortical excitability, using transcranial magnetic stimulation. Healthy young (n = 24, 22 years) and old (n = 22, 71 years) adults practiced a wrist flexion-extention visuomotor task or only watched the templates as an attentional control for 20 minutes. Old compared with young adults performed less well at baseline. Although the absolute magnitude of skill acquisition and retention was similar in the 2 age groups (age × intervention × time, p = 0.425), a comparison of baseline-similar age sub-groups revealed impaired skill acquisition but not retention in old versus young. Furthermore, the neuronal mechanisms differed as revealed by an opposite direction of associations in the age-groups between relative skill acquisition and intracortical facilitation during the task, and opposite changes during skill retention in corticospinal excitability at rest and during the task and intracortical inhibition during the task.

  7. Thermal ageing mechanisms of VVER-1000 reactor pressure vessel steels

    NASA Astrophysics Data System (ADS)

    Shtrombakh, Yaroslav I.; Gurovich, Boris A.; Kuleshova, Evgenia A.; Maltsev, Dmitry A.; Fedotova, Svetlana V.; Chernobaeva, Anna A.

    2014-09-01

    In this paper a complex of microstructural studies (TEM and SEM) and a comparative analysis of the results of these studies with the data of mechanical tests of temperature sets of VVER-1000 RPV surveillance specimens with exposure times up to ∼200,000 h were conducted. Special annealing of control and temperature sets of SS which provides the dissolution of grain boundary segregation was performed to clarify the mechanisms of thermal ageing. It was demonstrated that during long-term exposures up to 200,000 h at the operating temperature of about 310-320 °C thermal ageing effects reveal themselves only for the weld metal (Ni content ⩾ 1.35%) and are the result of grain boundary segregation accumulation (development of reversible temper brittleness). The obtained results improve the accuracy of prediction of the thermal ageing rate of VVER-1000 materials in case of RPV service life extension up to 60 years.

  8. ROS, Cell Senescence, and Novel Molecular Mechanisms in Aging and Age-Related Diseases

    PubMed Central

    Davalli, Pierpaola; Mitic, Tijana; Caporali, Andrea; Lauriola, Angela; D'Arca, Domenico

    2016-01-01

    The aging process worsens the human body functions at multiple levels, thus causing its gradual decrease to resist stress, damage, and disease. Besides changes in gene expression and metabolic control, the aging rate has been associated with the production of high levels of Reactive Oxygen Species (ROS) and/or Reactive Nitrosative Species (RNS). Specific increases of ROS level have been demonstrated as potentially critical for induction and maintenance of cell senescence process. Causal connection between ROS, aging, age-related pathologies, and cell senescence is studied intensely. Senescent cells have been proposed as a target for interventions to delay the aging and its related diseases or to improve the diseases treatment. Therapeutic interventions towards senescent cells might allow restoring the health and curing the diseases that share basal processes, rather than curing each disease in separate and symptomatic way. Here, we review observations on ROS ability of inducing cell senescence through novel mechanisms that underpin aging processes. Particular emphasis is addressed to the novel mechanisms of ROS involvement in epigenetic regulation of cell senescence and aging, with the aim to individuate specific pathways, which might promote healthy lifespan and improve aging. PMID:27247702

  9. Malignant pleural mesothelioma in US automotive mechanics: reported vs expected number of cases from 1975 to 2007.

    PubMed

    Finley, Brent L; Pierce, Jennifer S; Paustenbach, Dennis J; Scott, Laura L F; Lievense, Laura; Scott, Paul K; Galbraith, David A

    2012-10-01

    Until the 1980s, chrysotile asbestos was a component of automotive brakes manufactured in the US. The current OSHA Bulletin (2006) for brake repair cites a single study (Lemen, 2004) which concluded that the number of mesothelioma cases reported in the literature in "end-product users of friction materials" indicated an asbestos-related risk for auto mechanics. However, Lemen (2004) did not compare the reported number of cases to an "expected" value, even though pleural mesothelioma occurs in the general population in the absence of asbestos exposure. We compare the number of malignant pleural mesothelioma (MPM) cases reported in the US literature among auto mechanics between 1975-2007 to an expected value derived from estimated numbers of current and former auto mechanics. A total of 106 cases categorized as mesothelioma or malignant neoplasm of the pleura were found in the literature. Using background incidence rates for MPM of two and three cases per million individuals per year, we estimated that a range of 278-515 cases of non-asbestos-related MPM, respectively, would have occurred in current or former auto mechanics from 1975-2007. Our findings are consistent with the numerous epidemiology studies that have found no increased risk of MPM in auto mechanics.

  10. Aging mechanisms and service life of lead-acid batteries

    NASA Astrophysics Data System (ADS)

    Ruetschi, Paul

    In lead-acid batteries, major aging processes, leading to gradual loss of performance, and eventually to the end of service life, are: Anodic corrosion (of grids, plate-lugs, straps or posts). Positive active mass degradation and loss of adherence to the grid (shedding, sludging). Irreversible formation of lead sulfate in the active mass (crystallization, sulfation). Short-circuits. Loss of water. Aging mechanisms are often inter-dependent. For example, corrosion of the grids will lead to increased resistance to current flow, which will in turn impede proper charge of certain parts of the active mass, resulting in sulfation. Active mass degradation may lead to short-circuits. Sulfation may be the result of a loss of water, and so forth. The rates of the different aging processes strongly depend on the type of use (or misuse) of the battery. Over-charge will lead to accelerated corrosion and also to accelerated loss of water. With increasing depth-of-discharge during cycling, positive active mass degradation is accelerated. Some aging mechanisms are occurring only upon misuse. Short-circuits across the separators, due to the formation of metallic lead dendrites, for example, are usually formed only after (excessively) deep discharge. Stationary batteries, operated under float-charge conditions, will age typically by corrosion of the positive grids. On the other hand, service life of batteries subject to cycling regimes, will typically age by degradation of the structure of the positive active mass. Starter batteries are usually aging by grid corrosion, for instance in normal passenger car use. However, starter batteries of city buses, making frequent stops, may age (prematurely) by positive active mass degradation, because the batteries are subject to numerous shallow discharge cycles. Valve-regulated batteries often fail as a result of negative active mass sulfation, or water loss. For each battery design, and type of use, there is usually a characteristic

  11. Threshold Levels of Infant and Under-Five Mortality for Crossover between Life Expectancies at Ages Zero, One and Five in India: A Decomposition Analysis

    PubMed Central

    Dubey, Manisha

    2015-01-01

    Objectives Under the prevailing conditions of imbalanced life table and historic gender discrimination in India, our study examines crossover between life expectancies at ages zero, one and five years for India and quantifies the relative share of infant and under-five mortality towards this crossover. Methods We estimate threshold levels of infant and under-five mortality required for crossover using age specific death rates during 1981–2009 for 16 Indian states by sex (comprising of India’s 90% population in 2011). Kitagawa decomposition equations were used to analyse relative share of infant and under-five mortality towards crossover. Findings India experienced crossover between life expectancies at ages zero and five in 2004 for menand in 2009 for women; eleven and nine Indian states have experienced this crossover for men and women, respectively. Men usually experienced crossover four years earlier than the women. Improvements in mortality below ages five have mostly contributed towards this crossover. Life expectancy at age one exceeds that at age zero for both men and women in India except for Kerala (the only state to experience this crossover in 2000 for men and 1999 for women). Conclusions For India, using life expectancy at age zero and under-five mortality rate together may be more meaningful to measure overall health of its people until the crossover. Delayed crossover for women, despite higher life expectancy at birth than for men reiterates that Indian women are still disadvantaged and hence use of life expectancies at ages zero, one and five become important for India. Greater programmatic efforts to control leading causes of death during the first month and 1–59 months in high child mortality areas can help India to attain this crossover early. PMID:26683617

  12. Elements for the expected mechanisms on 'reduced emissions from deforestation and degradation, REDD' under UNFCCC

    NASA Astrophysics Data System (ADS)

    Mollicone, D.; Freibauer, A.; Schulze, E. D.; Braatz, S.; Grassi, G.; Federici, S.

    2007-10-01

    Carbon emissions from deforestation and degradation account for about 20% of global anthropogenic emissions. Strategies and incentives for reduced emissions from deforestation and degradation (REDD) have emerged as one of the most active areas in the international climate change negotiations under the United Nations Framework Convention on Climate Change (UNFCCC). While the current negotiations focus on a REDD mechanism in developing countries, it should be recognized that risks of carbon losses from forests occur in all climate zones and also in industrialized countries. A future climate change agreement would be more effective if it included all carbon losses and gains from land use in all countries and climate zones. The REDD mechanism will be an important step towards reducing emissions from land use change in developing countries, but needs to be followed by steps in other land use systems and regions. A national approach to REDD and significant coverage globally are needed to deal with the risk that deforestation and degradation activities are displaced rather than avoided. Favourable institutional and governance conditions need to be established that guarantee in the long-term a stable incentive and control system for maintaining forest carbon stocks. Ambitious emission reductions from deforestation and forest degradation need sustained financial incentives, which go beyond positive incentives for reduced emissions but also give incentives for sustainable forest management. Current data limitations need—and can be—overcome in the coming years to allow accurate accounting of reduced emissions from deforestation and degradation. A proper application of the conservativeness approach in the REDD context could allow a simplified reporting of emissions from deforestation in a first phase, consistent with the already agreed UNFCCC reporting principles.

  13. Mechanical Regulation of Cardiac Aging in Model Systems.

    PubMed

    Sessions, Ayla O; Engler, Adam J

    2016-05-13

    Unlike diet and exercise, which individuals can modulate according to their lifestyle, aging is unavoidable. With normal or healthy aging, the heart undergoes extensive vascular, cellular, and interstitial molecular changes that result in stiffer less compliant hearts that experience a general decline in organ function. Although these molecular changes deemed cardiac remodeling were once thought to be concomitant with advanced cardiovascular disease, they can be found in patients without manifestation of clinical disease. It is now mostly acknowledged that these age-related mechanical changes confer vulnerability of the heart to cardiovascular stresses associated with disease, such as hypertension and atherosclerosis. However, recent studies have aimed at differentiating the initial compensatory changes that occur within the heart with age to maintain contractile function from the maladaptive responses associated with disease. This work has identified new targets to improve cardiac function during aging. Spanning invertebrate to vertebrate models, we use this review to delineate some hallmarks of physiological versus pathological remodeling that occur in the cardiomyocyte and its microenvironment, focusing especially on the mechanical changes that occur within the sarcomere, intercalated disc, costamere, and extracellular matrix. PMID:27174949

  14. Cost comparison of mechanically ventilated patients across the age span

    PubMed Central

    Hayman, William R.; Leuthner, Steven R.; Laventhal, Naomi T.; Brousseau, David; Lagatta, Joanne M.

    2016-01-01

    Objective to compare use of mechanical ventilation and hospital costs across ventilated patients of all ages, preterm through adults, in a nationally-representative sample. Study Design secondary analysis of the 2009 Agency for Healthcare Research and Quality National Inpatient Sample. Results 1,107,563 (2.8%) patients received mechanical ventilation. For surviving ventilated patients, median costs for infants ≤32 weeks’ gestation were $51,000–$209,000, whereas median costs for older patients were lower, from $17,000–$25,000. For non-surviving ventilated patients, median costs were $27,000–$39,000 except at the extremes of age; the median cost was $10,000 for <24 week newborns, and $14,000 for 91+ year adults. Newborns of all gestational ages had a disproportionate share of hospital costs relative to their total volume. Conclusions Most ICU resources at the extremes of age are not directed toward non-surviving patients. From a perinatal perspective, attention should be directed toward improving outcomes and reducing costs for all infants, not just at the earliest gestational ages. PMID:26468935

  15. Ultimate mechanisms of age-biased flea parasitism.

    PubMed

    Hawlena, Hadas; Abramsky, Zvika; Krasnov, Boris R

    2007-12-01

    Mechanisms that cause nonrandom patterns of parasite distribution among host individuals may influence the population and evolutionary dynamics of both parasites and hosts, but are still poorly understood. We studied whether survival, reproduction, and behavioral responses of fleas (Xenopsylla conformis) changed with the age of their rodent hosts (Meriones crassus), experimentally disentangling two possible mechanisms: (a) differential survival and/or fitness reward of parasites due to host age, and (b) active parasite choice of a host of a particular age. To explore the first mechanism, we raised fleas on rodents of two age groups and assessed flea survival as well as the quantity and quality of their offspring. To explore the second mechanism, three groups of fleas that differed in their previous feeding experience (no experience, experience on juvenile or experience on adult rodents) were given an opportunity to choose between juvenile and adult rodents in a Y-maze. Fleas raised on juvenile rodents had higher survival and had more offspring that emerged earlier than fleas raised on adults. However, fleas did not show any innate preference for juvenile rodents, nor were they able to learn to choose them. In contrast to our predictions, based on a single previous exposure, fleas learned to choose adult rodents. The results suggest that two mechanisms-differential survival and fitness reward of fleas, and associative learning by them-affect patterns of flea distribution between juvenile and adult rodents. The former increases whereas the latter reduces flea densities on juvenile rodents. The ability of fleas to learn to choose adult but not juvenile hosts may be due to: (a) a stronger stimulus from adults, (b) a higher profitability of adults in terms of predictability and abundance, or (c) the evolutionary importance of recognizing adult but not juvenile hosts as representatives of the species.

  16. Skin aging and oxidative stress: Equol's anti-aging effects via biochemical and molecular mechanisms.

    PubMed

    Lephart, Edwin D

    2016-11-01

    Oxygen in biology is essential for life. It comes at a cost during normal cellular function, where reactive oxygen species (ROS) are generated by oxidative metabolism. Human skin exposed to solar ultra-violet radiation (UVR) dramatically increases ROS production/oxidative stress. It is important to understand the characteristics of human skin and how chronological (intrinsic) aging and photo-aging (extrinsic aging) occur via the impact of ROS production by cascade signaling pathways. The goal is to oppose or neutralize ROS insults to maintain good dermal health. Botanicals, as active ingredients, represent one of the largest categories used in dermatology and cosmeceuticals to combat skin aging. An emerging botanical is equol, a polyphenolic/isoflavonoid molecule found in plants and food products and via gastrointestinal metabolism from precursor compounds. Introductory sections cover oxygen, free radicals (ROS), oxidative stress, antioxidants, human skin aging, cellular/molecular ROS events in skin, steroid enzymes/receptors/hormonal actions and genetic factors in aging skin. The main focus of this review covers the characteristics of equol (phytoestrogenic, antioxidant and enhancement of extracellular matrix properties) to reduce skin aging along with its anti-aging skin influences via reducing oxidative stress cascade events by a variety of biochemical/molecular actions and mechanisms to enhance human dermal health. PMID:27521253

  17. Age of sex-determining mechanisms in vertebrates.

    PubMed

    WITSCHI, E

    1959-08-14

    Certain characteristic patterns of physiologic sex determination are not causally linked with types of genic and chromosomal constitution (XX-XY or ZW-ZZ). The observed widespread but not universal parallelism in the distribution of genetic and physiologic patterns among vertebrate groups expresses genealogic relationship. On the basis of this interpretation one may estimate the approximate evolutionary age of the mechanism of genetic sex determination. It is concluded that in all tetrapod vertebrates these mechanisms originated during the Jurassic period. Environmental conditions seem to affect the progress of this evolution. PMID:13675759

  18. Age of sex-determining mechanisms in vertebrates.

    PubMed

    WITSCHI, E

    1959-08-14

    Certain characteristic patterns of physiologic sex determination are not causally linked with types of genic and chromosomal constitution (XX-XY or ZW-ZZ). The observed widespread but not universal parallelism in the distribution of genetic and physiologic patterns among vertebrate groups expresses genealogic relationship. On the basis of this interpretation one may estimate the approximate evolutionary age of the mechanism of genetic sex determination. It is concluded that in all tetrapod vertebrates these mechanisms originated during the Jurassic period. Environmental conditions seem to affect the progress of this evolution.

  19. Age of acquisition: its neural and computational mechanisms.

    PubMed

    Hernandez, Arturo E; Li, Ping

    2007-07-01

    The acquisition of new skills over a life span is a remarkable human ability. This ability, however, is constrained by age of acquisition (AoA); that is, the age at which learning occurs significantly affects the outcome. This is most clearly reflected in domains such as language, music, and athletics. This article provides a perspective on the neural and computational mechanisms underlying AoA in language acquisition. The authors show how AoA modulates both monolingual lexical processing and bilingual language acquisition. They consider the conditions under which syntactic processing and semantic processing may be differentially sensitive to AoA effects in second-language acquisition. The authors conclude that AoA effects are pervasive and that the neural and computational mechanisms underlying learning and sensorimotor integration provide a general account of these effects.

  20. Acculturation or Development? Autonomy Expectations among Ethnic German Immigrant Adolescents and Their Native German Age-Mates

    ERIC Educational Resources Information Center

    Titzmann, Peter F.; Silbereisen, Rainer K.

    2012-01-01

    This longitudinal study compared immigrant and native adolescents' expectations concerning the timing of conventional socially acceptable and oppositional less socially acceptable forms of autonomy. Based on normative development and a collectivist background among immigrants, both developmental and acculturative change was expected. The sample…

  1. Relationship Between the Remaining Years of Healthy Life Expectancy in Older Age and National Income Level, Educational Attainment, and Improved Water Quality.

    PubMed

    Kim, Jong In; Kim, Gukbin

    2016-10-01

    The remaining years of healthy life expectancy (RYH) at age 65 years can be calculated as RYH (65) = healthy life expectancy-aged 65 years. This study confirms the associations between socioeconomic indicators and the RYH (65) in 148 countries. The RYH data were obtained from the World Health Organization. Significant positive correlations between RYH (65) in men and women and the socioeconomic indicators national income, education level, and improved drinking water were found. Finally, the predictors of RYH (65) in men and women were used to build a model of the RYH using higher socioeconomic indicators (R(2 )= 0.744, p < .001). Overall country-level educational attainment, national income level, and improved water quality influenced the RYH at 65 years. Therefore, policymaking to improve these country-level socioeconomic factors is expected to have latent effects on RYH in older age. PMID:27388888

  2. Relationship Between the Remaining Years of Healthy Life Expectancy in Older Age and National Income Level, Educational Attainment, and Improved Water Quality.

    PubMed

    Kim, Jong In; Kim, Gukbin

    2016-10-01

    The remaining years of healthy life expectancy (RYH) at age 65 years can be calculated as RYH (65) = healthy life expectancy-aged 65 years. This study confirms the associations between socioeconomic indicators and the RYH (65) in 148 countries. The RYH data were obtained from the World Health Organization. Significant positive correlations between RYH (65) in men and women and the socioeconomic indicators national income, education level, and improved drinking water were found. Finally, the predictors of RYH (65) in men and women were used to build a model of the RYH using higher socioeconomic indicators (R(2 )= 0.744, p < .001). Overall country-level educational attainment, national income level, and improved water quality influenced the RYH at 65 years. Therefore, policymaking to improve these country-level socioeconomic factors is expected to have latent effects on RYH in older age.

  3. Aging and Immune Function: Molecular Mechanisms to Interventions

    PubMed Central

    Ponnappan, Subramaniam

    2011-01-01

    Abstract The immune system of an organism is an essential component of the defense mechanism aimed at combating pathogenic stress. Age-associated immune dysfunction, also dubbed “immune senescence,” manifests as increased susceptibility to infections, increased onset and progression of autoimmune diseases, and onset of neoplasia. Over the years, extensive research has generated consensus in terms of the phenotypic and functional defects within the immune system in various organisms, including humans. Indeed, age-associated alterations such as thymic involution, T cell repertoire skewing, decreased ability to activate naïve T cells and to generate robust memory responses, have been shown to have a causative role in immune decline. Further, understanding the molecular mechanisms underlying the generation of proteotoxic stress, DNA damage response, modulation of ubiquitin proteasome pathway, and regulation of transcription factor NFκB activation, in immune decline, have paved the way to delineating signaling pathways that cross-talk and impact immune senescence. Given the role of the immune system in combating infections, its effectiveness with age may well be a marker of health and a predictor of longevity. It is therefore believed that a better understanding of the mechanisms underlying immune senescence will lead to an effective interventional strategy aimed at improving the health span of individuals. Antioxid. Redox Signal. 14, 1551–1585. PMID:20812785

  4. Neuroendocrine aging in birds: comparing lifespan differences and conserved mechanisms.

    PubMed

    Ottinger, Mary Ann

    2007-05-01

    As more comparative data become available, it is clear that the process of aging has fundamental similarities across classes of vertebrates. Birds provide a fascinating collection of species because of the considerable range in reproductive lifespan and variation in reproductive strategies that often relate to lifespan. One fascinating aspect of the comparative biology of aging in different avian species is the conserved mechanisms that appear very similar to those observed in mammals. Despite marked differences in sexual differentiation and reproductive function, including a single functional ovary and the internal testes, there appears to be remarkable similarity in elements of neuroendocrine aging and their end results. Furthermore, although beyond the scope of this review, the intense endocrine and energetic demands on many species of temperate zone birds for long migration and the accompanying seasonal alterations in endocrine responses add an additional layer of complexity in understanding aging. It is the purpose of this review to focus on neuroendocrine changes that accompany aging in a short-lived bird, with mention of some of the available data in field birds and long-lived species. Unfortunately, few neuroendocrine data are available for these long-lived avian species. It would be very interesting to determine if these long-lived birds somehow manage to delay the cascade of changes that contribute to the demise of metabolic and reproductive endocrine function. This review will also attempt to integrate the time-related events that occur in the responses of the hypothalamus and the gonads, especially relative to the neuroregulatory systems that have been implicated in the age-related decline in reproductive function. Finally, emerging areas of interest will be considered in the context of future research areas. PMID:17452025

  5. Mortality under age 50 accounts for much of the fact that US life expectancy lags that of other high-income countries.

    PubMed

    Ho, Jessica Y

    2013-03-01

    Life expectancy at birth in the United States is among the lowest of all high-income countries. Most recent studies have concentrated on older ages, finding that Americans have a lower life expectancy at age fifty and experience higher levels of disease and disability than do their counterparts in other industrialized nations. Using cross-national mortality data to identify the key age groups and causes of death responsible for these shortfalls, I found that mortality differences below age fifty account for two-thirds of the gap in life expectancy at birth between American males and their counterparts in sixteen comparison countries. Among females, the figure is two-fifths. The major causes of death responsible for the below-fifty trends are unintentional injuries, including drug overdose--a fact that constitutes the most striking finding from this study; noncommunicable diseases; perinatal conditions, such as pregnancy complications and birth trauma; and homicide. In all, this study highlights the importance of focusing on younger ages and on policies both to prevent the major causes of death below age fifty and to reduce social inequalities.

  6. Mechanism of Inflammation in Age-Related Macular Degeneration

    PubMed Central

    Parmeggiani, Francesco; Romano, Mario R.; Costagliola, Ciro; Semeraro, Francesco; Incorvaia, Carlo; D'Angelo, Sergio; Perri, Paolo; De Palma, Paolo; De Nadai, Katia; Sebastiani, Adolfo

    2012-01-01

    Age-related macular degeneration (AMD) is a multifactorial disease that represents the most common cause of irreversible visual impairment among people over the age of 50 in Europe, the United States, and Australia, accounting for up to 50% of all cases of central blindness. Risk factors of AMD are heterogeneous, mainly including increasing age and different genetic predispositions, together with several environmental/epigenetic factors, that is, cigarette smoking, dietary habits, and phototoxic exposure. In the aging retina, free radicals and oxidized lipoproteins are considered to be major causes of tissue stress resulting in local triggers for parainflammation, a chronic status which contributes to initiation and/or progression of many human neurodegenerative diseases such as AMD. Experimental and clinical evidences strongly indicate the pathogenetic role of immunologic processes in AMD occurrence, consisting of production of inflammatory related molecules, recruitment of macrophages, complement activation, microglial activation and accumulation within those structures that compose an essential area of the retina known as macula lutea. This paper reviews some attractive aspects of the literature about the mechanisms of inflammation in AMD, especially focusing on those findings or arguments more directly translatable to improve the clinical management of patients with AMD and to prevent the severe vision loss caused by this disease. PMID:23209345

  7. Molecular and Mechanical Causes of Microtubule Catastrophe and Aging.

    PubMed

    Zakharov, Pavel; Gudimchuk, Nikita; Voevodin, Vladimir; Tikhonravov, Alexander; Ataullakhanov, Fazoil I; Grishchuk, Ekaterina L

    2015-12-15

    Tubulin polymers, microtubules, can switch abruptly from the assembly to shortening. These infrequent transitions, termed "catastrophes", affect numerous cellular processes but the underlying mechanisms are elusive. We approached this complex stochastic system using advanced coarse-grained molecular dynamics modeling of tubulin-tubulin interactions. Unlike in previous simplified models of dynamic microtubules, the catastrophes in this model arise owing to fluctuations in the composition and conformation of a growing microtubule tip, most notably in the number of protofilament curls. In our model, dynamic evolution of the stochastic microtubule tip configurations over a long timescale, known as the system's "aging", gives rise to the nonexponential distribution of microtubule lifetimes, consistent with experiment. We show that aging takes place in the absence of visible changes in the microtubule wall or tip, as this complex molecular-mechanical system evolves slowly and asymptotically toward the steady-state level of the catastrophe-promoting configurations. This new, to our knowledge, theoretical basis will assist detailed mechanistic investigations of the mechanisms of action of different microtubule-binding proteins and drugs, thereby enabling accurate control over the microtubule dynamics to treat various pathologies. PMID:26682815

  8. Outcome at school-age after neonatal mechanical ventilation.

    PubMed

    Gunn, T R; Lepore, E; Outerbridge, E W

    1983-06-01

    103 school-age children (5 to 12 years) who survived mechanical ventilation for neonatal respiratory failure were evaluated for growth, neurological, intellectual, psychological and school function in order to determine those children most at risk for handicap. A major handicap occurred in seven children, preventing attendance at normal school or normal classes. Neurological sequelae were significantly associated with perinatal asphyxia and with birthweights of 1500g or less, and neurological sequelae and socio-economic factors were the major determinants of ability. The effects of the Neonatal Intensive Care Unit (NICU) experience on parents and subsequent parent-child relationships were also investigated: 67 per cent of the mothers were very upset by the experience and many continue to worry excessively about the health of their child. Parents who visited their child in the NICU frequently were significantly more anxious and overprotective, restricting many activities even when the child was of school age. PMID:6873492

  9. Erythropoietin and mTOR: A “One-Two Punch” for Aging-Related Disorders Accompanied by Enhanced Life Expectancy

    PubMed Central

    Maiese, Kenneth

    2016-01-01

    Life expectancy continues to increase throughout the world, but is accompanied by a rise in the incidence of non-communicable diseases. As a result, the benefits of an increased lifespan can be limited by aging-related disorders that necessitate new directives for the development of effective and safe treatment modalities. With this objective, the mechanistic target of rapamycin (mTOR), a 289-kDa serine/threonine protein, and its related pathways of mTOR Complex 1 (mTORC1), mTOR Complex 2 (mTORC2), proline rich Akt substrate 40 kDa (PRAS40), AMP activated protein kinase (AMPK), Wnt signaling, and silent mating type information regulation 2 homolog 1 (Saccharomyces cerevisiae) (SIRT1), have generated significant excitement for furthering novel therapies applicable to multiple systems of the body. Yet, the biological and clinical outcome of these pathways can be complex especially with oversight of cell death mechanisms that involve apoptosis and autophagy. Growth factors, and in particular erythropoietin (EPO), are one avenue under consideration to implement control over cell death pathways since EPO can offer potential treatment for multiple disease entities and is intimately dependent upon mTOR signaling. In experimental and clinical studies, EPO appears to have significant efficacy in treating several disorders including those involving the developing brain. However, in mature populations that are affected by aging-related disorders, the direction for the use of EPO to treat clinical disease is less clear that may be dependent upon a number of factors including the understanding of mTOR signaling. Continued focus upon the regulatory elements that control EPO and mTOR signaling could generate critical insights for targeting a broad range of clinical maladies. PMID:27488211

  10. Age-dependent ascending aorta mechanics assessed through multiphase CT.

    PubMed

    Martin, Caitlin; Sun, Wei; Primiano, Charles; McKay, Raymond; Elefteriades, John

    2013-12-01

    Quantification of the age- and gender-specific in vivo mechanical characteristics of the ascending aorta (AA) will allow for identification of abnormalities aside from changes brought on by aging alone. Multiphase clinical CT scans of 45 male patients between the ages of 30 and 79 years were analyzed to assess age-dependent in vivo AA characteristics. The three-dimensional AA geometry for each patient was reconstructed from the CT scans for 9-10 phases throughout the cardiac cycle. The AA circumference was measured during each phase and was used to determine the corresponding diameter, circumferential strain, and wall tension at each phase. The pressure-strain modulus was also determined for each patient. The mean diastolic AA diameter was significantly smaller among young (42.6 ± 5.2 years) at 29.9 ± 2.8 mm than old patients (69.0 ± 5.2 years) at 33.2 ± 3.2 mm. The circumferential AA strain from end-diastole to peak-systole decreased from 0.092 ± 0.03 in young to 0.056 ± 0.03 in old patients. The pressure-strain modulus increased two-fold from 68.4 ± 30.5 kPa in young to 162.0 ± 93.5 kPa in old patients, and the systolic AA wall tension increased from 268.5 ± 31.3 kPa in young to 304.9 ± 49.2 kPa in old patients. The AA dilates and stiffens with aging which increases the vessel wall tension, likely predisposing aneurysm and dissection.

  11. Accelerated ageing: from mechanism to therapy through animal models.

    PubMed

    Osorio, Fernando G; Obaya, Alvaro J; López-Otín, Carlos; Freije, José M P

    2009-02-01

    Ageing research benefits from the study of accelerated ageing syndromes such as Hutchinson-Gilford progeria syndrome (HGPS), characterized by the early appearance of symptoms normally associated with advanced age. Most HGPS cases are caused by a mutation in the gene LMNA, which leads to the synthesis of a truncated precursor of lamin A known as progerin that lacks the target sequence for the metallopotease FACE-1/ZMPSTE24 and remains constitutively farnesylated. The use of Face-1/Zmpste24-deficient mice allowed us to demonstrate that accumulation of farnesylated prelamin A causes severe abnormalities of the nuclear envelope, hyper-activation of p53 signalling, cellular senescence, stem cell dysfunction and the development of a progeroid phenotype. The reduction of prenylated prelamin A levels in genetically modified mice leads to a complete reversal of the progeroid phenotype, suggesting that inhibition of protein farnesylation could represent a therapeutic option for the treatment of progeria. However, we found that both prelamin A and its truncated form progerin can undergo either farnesylation or geranylgeranylation, revealing the need of targeting both activities for an efficient treatment of HGPS. Using Face-1/Zmpste24-deficient mice as model, we found that a combination of statins and aminobisphosphonates inhibits both types of modifications of prelamin A and progerin, improves the ageing-like symptoms of these mice and extends substantially their longevity, opening a new therapeutic possibility for human progeroid syndromes associated with nuclear-envelope defects. We discuss here the use of this and other animal models to investigate the molecular mechanisms underlying accelerated ageing and to test strategies for its treatment.

  12. Investigation of Aging Mechanisms in Lean NOx Traps

    SciTech Connect

    Mark Crocker

    2010-03-31

    Lean NO{sub x} traps (LNTs) represent a promising technology for the abatement of NO{sub x} under lean conditions. Although LNTs are starting to find commercial application, the issue of catalyst durability remains problematic. LNT susceptibility to sulfur poisoning is the single most important factor determining effective catalyst lifetime. The NO{sub x} storage element of the catalyst has a greater affinity for SO{sub 3} than it does for NO{sub 2}, and the resulting sulfate is more stable than the stored nitrate. Although this sulfate can be removed from the catalyst by means of high temperature treatment under rich conditions, the required conditions give rise to deactivation mechanisms such as precious metal sintering, total surface area loss, and solid state reactions between the various oxides present. The principle objective of this project was to improve understanding of the mechanisms of lean NO{sub x} trap aging, and to understand the effect of washcoat composition on catalyst aging characteristics. The approach utilized involved detailed characterization of model catalysts prior to and after aging, in tandem with measurement of catalyst performance in NO{sub x} storage and reduction. In this manner, NO{sub x} storage and reduction characteristics were correlated with the evolution of catalyst physico-chemical properties upon aging. Rather than using poorly characterized proprietary catalysts, or simple model catalysts of the Pt/BaO/Al{sub 2}O{sub 3} type (representing the first generation of LNTs), Pt/Rh/BaO/Al{sub 2}O{sub 3} catalysts were employed which also incorporated CeO{sub 2} or CeO{sub 2}-ZrO{sub 2}, representing a model system which more accurately reflects current LNT formulations. Catalysts were prepared in which the concentration of each of the main components was systematically varied: Pt (50, 75 or 100 g/ft{sup 3}), Rh (10 or 20 g/ft{sup 3}), BaO (15, 30 or 45 g/L), and either CeO{sub 2} (0, 50 or 100 g/L) or CeO{sub 2}-ZrO{sub 2} (0, 50

  13. Meeting the expectation of industry: an integrated approach for the teaching of mechanics and electronics to design students

    NASA Astrophysics Data System (ADS)

    Bingham, Guy A.; Southee, Darren J.; Page, Tom

    2015-07-01

    This paper examines the traditional engineering-based provision delivered to Product Design and Technology (B.Sc.) undergraduates at the Loughborough Design School and questions its relevancy against the increasing expectations of industry. The paper reviews final-year design projects to understand the level of transference of engineering-based knowledge into design practice and highlights areas of opportunity for improved teaching and learning. The paper discusses the development and implementation of an integrated approach to the teaching of Mechanics and Electronics to formalise and reinforce the key learning process of transference within the design context. The paper concludes with observations from the delivery of this integrated teaching and offers insights from student and academic perspectives for the further improvement of engineering-based teaching and learning.

  14. Mechanical properties of bulk polydimethylsiloxane for microfluidics over a large range of frequencies and aging times

    NASA Astrophysics Data System (ADS)

    Placet, V.; Delobelle, P.

    2015-03-01

    The dynamic mechanical characterization of polydimethylsiloxane (PDMS) over a large range of frequencies (10-2 < f < 105 Hz) and long aging times at room temperature (4 h < tv < ~60 000 h) has been presented. Three samples with different curing conditions have been studied and three different techniques, dynamic mechanical analysis at different temperatures, nano-indentation and scanning micro-deformation microscopy, have been used. Although the three techniques work at different scales and at different frequencies all the results match the same master curve. As expected, the storage and the loss moduli greatly increase with the frequency. Moreover, these moduli moderately increase with the aging time tv depending on the curing temperature. A simple model which takes the frequency and the aging time into account, and which is based on the Havriliak-Negami model, has been presented and identified. Hence, values of the relaxed and instantaneous moduli at tv = 0 and tv = ∞ are proposed. Only the relaxed moduli depend on the curing conditions and moreover it has been shown that the tangent of the phase lag is independent of the aging time and thus of the curing process.

  15. Bicycle injuries: a matter of mechanism and age.

    PubMed

    Siman-Tov, Maya; Jaffe, Dena H; Peleg, Kobi

    2012-01-01

    Bicycle riding is a popular form of recreation with positive health and environmental effects. These road users are vulnerable to serious injuries, especially when motor vehicles are involved. The goal of this study was to characterize cyclist-related injuries according to motor vehicle involvement for adults versus children. A retrospective study was carried out using data from 11 trauma centers in the Israeli National Trauma Registry (2001-2007). Injuries were classified according to whether a motor vehicle was involved, and differences in injury characteristics were assessed for adults (18+ years) versus children (1-17 years). A total of 5529 patients were hospitalized for bicycle injuries, of whom 1765 were adults and 3764 were children. Thirty percent (n=1662) of all bicycle injuries involved motor vehicles, although the rate of injuries resulting in hospitalization was 37% among adults and 27% among children. Injury characteristics and hospital resource utilization differed substantially by age group. Cyclists struck by a motor vehicle presented with more severe injuries requiring more hospital resources and resulting in poorer outcomes than those not involved with motor vehicles. The interaction effect between motor vehicle involvement and age was significant for torso injuries and need for medical imaging. We found that injury characteristics, hospital resource utilization and health-related outcomes for bicycle injuries are highly dependent on patient's age and mechanism of injury. Effect modification of motor vehicle involvement by age may in part reflect physicians' attitudes toward pediatric imaging. The risks identified in this study should be used for preparedness and management of trauma hospitalizations from bicycle injuries. PMID:22062347

  16. Mechanisms of yogic practices in health, aging, and disease.

    PubMed

    Kuntsevich, Viktoriya; Bushell, William C; Theise, Neil D

    2010-01-01

    Mechanisms underlying the modulating effects of yogic cognitive-behavioral practices (eg, meditation, yoga asanas, pranayama breathing, caloric restriction) on human physiology can be classified into 4 transduction pathways: humoral factors, nervous system activity, cell trafficking, and bioelectromagnetism. Here we give examples of these transduction pathways and how, through them, yogic practices might optimize health, delay aging, and ameliorate chronic illness and stress from disability. We also recognize that most studies of these mechanisms remain embedded in a reductionist paradigm, investigating small numbers of elements of only 1 or 2 pathways. Moreover, often, subjects are not long-term practitioners, but recently trained. The models generated from such data are, in turn, often limited, top-down, without the explanatory power to describe beneficial effects of long-term practice or to provide foundations for comparing one practice to another. More flexible and useful models require a systems-biology approach to gathering and analysis of data. Such a paradigm is needed to fully appreciate the deeper mechanisms underlying the ability of yogic practice to optimize health, delay aging, and speed efficient recovery from injury or disease. In this regard, 3 different, not necessarily competing, hypotheses are presented to guide design of future investigations, namely, that yogic practices may: (1) promote restoration of physiologic setpoints to normal after derangements secondary to disease or injury, (2) promote homeostatic negative feedback loops over nonhomeostatic positive feedback loops in molecular and cellular interactions, and (3) quench abnormal "noise" in cellular and molecular signaling networks arising from environmental or internal stresses.

  17. Mechanisms of renal tubular defects in old age.

    PubMed Central

    Dontas, A. S.; Marketos, S. G.; Papanayiotou, P.

    1972-01-01

    The mechanisms of renal tubular dysfunction in old age have been examined in twenty-eight clinically healthy elderly subjects without infection, and in fourteen subjects of similar age with laboratory evidence of intrarenal infection. The data were compared with those from thirteen clinically healthy young subjects. Studied were: proximal tubular (Tm(PAH)) and distal tubular (CH2O) activity, minimal and maximal osmolal U/P ratios, maximal osmolal excretion in hydropenia, and GFR levels under standard hydration and under water-loading. The reduction of GFR in old age is evident particularly in men under conditions of standard hydration: it is accentuated in the presence of renal infection. Proximal tubular activity is also significantly lower in elderly men, especially if they have chronic bacteriuria. The reduction is closely related to GFR levels, with identical Tm(PAH):C(in) ratios in all groups. This supports the intact nephron hypothesis for this part of the nephron. Distal tubular activity is depressed in old age in both sexes proportionately more than proximal tubular activity or the GFR. The lower CH2O: GFR ratios imply a selective distal tubular damage. Maximal osmolal U/P ratios in hydropenia are significantly higher in the young (mean 367) than in either the elderly non-infected (mean 279) or the elderly infected subjects (mean 212). Conversely, minimal U/P ratios in water-loading are lower in the young (mean 0.247) than in either elderly group (means 0.418 and 0.668). Osmolal excretion in hydropenia is not different between the groups, but urine flows in water-loading clearly separate them. The data indicate that simple functions of the distal-collecting tubule (e.g. the CH2O), are less affected in old age than are functions involving several medullary structures (as is the maximal U(osm) or U/P ratio). They suggest that the main impairment of the distal tubular cell involves the failure to achieve a proper osmotic gradient between tubular fluid and

  18. Latina Mothers' and Daughters' Expectations for Autonomy at Age 15 (La Quinceañera)

    ERIC Educational Resources Information Center

    Romo, Laura F.; Mireles-Rios, Rebeca; Lopez-Tello, Gisselle

    2014-01-01

    American children gain more autonomy as they progress through adolescence, however, autonomy-granting for Latina adolescent girls from immigrant families is a relatively unexplored question. In this study, we identified behaviors that Mexican mothers and their daughters deemed to be appropriate when they reach the age of "La…

  19. Expectations of filial obligation and their impact on preferences for future living arrangements of middle-aged and older Asian Indian immigrants.

    PubMed

    Diwan, Sadhna; Lee, Sang E; Sen, Soma

    2011-03-01

    Filial obligation, described as culturally-defined rights and duties that prescribe how family members are expected to care for and provide support to each other, is an important variable that influences older immigrants' preferences for living and care arrangements. This exploratory study examined variables associated with expectations of filial obligation among middle-aged and older, Asian Indian, first generation immigrants and explored the relationship between variations in expectations of filial obligation and expressed preferences for future living arrangements. Data were collected through telephone surveys of 226 English-speaking immigrants in Atlanta, GA. Although no significant relationships were observed between filial obligation expectations and length of residence in the U.S., respondents indicated a variety of preferred future living arrangements. Contrary to current living arrangement patterns found among older immigrants, very few respondents preferred to move in with their children. The most popular preference was to "move closer to children," followed by "moving to a retirement community" with the majority preferring a retirement community geared to Asian Indians. Other preferences included "not moving" and "returning to India." Variations in expectations of filial obligation, length of residence in the U.S., and self-rated health were significantly associated with these preferences. Implications are discussed for building capacity within ethnic communities to address living arrangement preferences and their repercussions for caregiving in ethnic families and in communities.

  20. Molecular mechanisms involved in muscle wasting in cancer and ageing: cachexia versus sarcopenia.

    PubMed

    Argilés, Josep M; Busquets, Sílvia; Felipe, Antonio; López-Soriano, Francisco J

    2005-05-01

    The aim of the present review is to summarize and evaluate the different mechanisms and catabolic mediators involved in cancer cachexia and ageing sarcopenia since they may represent targets for future promising clinical investigations. Cancer cachexia is a syndrome characterized by a marked weight loss, anorexia, asthenia and anemia. In fact, many patients who die with advanced cancer suffer from cachexia. The degree of cachexia is inversely correlated with the survival time of the patient and it always implies a poor prognosis. Unfortunately, at the clinical level, cachexia is not treated until the patient suffers from a considerable weight loss and wasting. At this point, the cachectic syndrome is almost irreversible. The cachectic state is often associated with the presence and growth of the tumour and leads to a malnutrition status due to the induction of anorexia. In recent years, age-related diseases and disabilities have become of major health interest and importance. This holds particularly for muscle wasting, also known as sarcopenia, that decreases the quality of life of the geriatric population, increasing morbidity and decreasing life expectancy. The cachectic factors (associated with both depletion of fat stores and muscular tissue) can be divided into two categories: of tumour origin and humoural factors. In conclusion, more research should be devoted to the understanding of muscle wasting mediators, both in cancer and ageing, in particular the identification of common mediators may prove as a good therapeutic strategies for both prevention and treatment of wasting both in disease and during healthy ageing.

  1. A synopsis on aging-Theories, mechanisms and future prospects.

    PubMed

    da Costa, João Pinto; Vitorino, Rui; Silva, Gustavo M; Vogel, Christine; Duarte, Armando C; Rocha-Santos, Teresa

    2016-08-01

    Answering the question as to why we age is tantamount to answering the question of what is life itself. There are countless theories as to why and how we age, but, until recently, the very definition of aging - senescence - was still uncertain. Here, we summarize the main views of the different models of senescence, with a special emphasis on the biochemical processes that accompany aging. Though inherently complex, aging is characterized by numerous changes that take place at different levels of the biological hierarchy. We therefore explore some of the most relevant changes that take place during aging and, finally, we overview the current status of emergent aging therapies and what the future holds for this field of research. From this multi-dimensional approach, it becomes clear that an integrative approach that couples aging research with systems biology, capable of providing novel insights into how and why we age, is necessary. PMID:27353257

  2. Radiochemical ageing of EPDM elastomers. 3. Mechanism of radiooxidation

    NASA Astrophysics Data System (ADS)

    Rivaton, A.; Cambon, S.; Gardette, J.-L.

    2005-01-01

    The preceding paper of this series was devoted to the identification and quantification of the main chemical changes resulting from the radiochemical ageing of EPDM (77.9% ethylene, 21.4% propylene, 0.7% diene) and EPR (76.6% ethylene, 23.4% propylene) films irradiated under oxygen atmosphere using 60Co gamma rays. The double bond of the diene was observed to be consumed with a high radiochemical yield. The oxidation and reticulation rates were observed to be higher in the case of EPDM than in EPR. Accumulation of the major oxidation products in both polymers was shown to occur in the order of decreasing concentrations: hydroperoxides, ketones, carboxylic acids and alcohols, peroxides. On the basis of the analysis of the oxidation products formed in EPDM and EPR, and taking into account their relative concentrations, the mechanisms accounting for the EPDM γ-degradation under oxygen atmosphere are proposed in the present paper. Two main processes are involved in the EPDM radiooxidation. The random γ-radiolysis of the polymer provides a constant source of macroalkyl radicals mainly formed on ethylene units. The secondary radicals so formed are likely to initiate a selective oxidation of the polymer through free-radicals reactions involving the abstraction of labile hydrogen atoms. In particular, the hydroperoxides decomposition and the consumption of the ENB moieties, this latter being the most oxidisable site and the source of crosslinking, may result from hydrogen abstraction by radical species.

  3. A comparison of health expectancies over two decades in England: results of the Cognitive Function and Ageing Study I and II

    PubMed Central

    Jagger, Carol; Matthews, Fiona E; Wohland, Pia; Fouweather, Tony; Stephan, Blossom C M; Robinson, Louise; Arthur, Antony; Brayne, Carol

    2016-01-01

    Summary Background Whether rises in life expectancy are increases in good-quality years is of profound importance worldwide, with population ageing. We investigate how various health expectancies have changed in England between 1991 and 2011, with identical study design and methods in each decade. Methods Baseline data from the Cognitive Function and Ageing Studies in populations aged 65 years or older in three geographically defined centres in England (Cambridgeshire, Newcastle, and Nottingham) provided prevalence estimates for three health measures: self-perceived health (defined as excellent–good, fair, or poor); cognitive impairment (defined as moderate–severe, mild, or none, as assessed by Mini-Mental State Examination score); and disability in activities of daily living (defined as none, mild, or moderate–severe). Health expectancies for the three regions combined were calculated by the Sullivan method, which applies the age-specific and sex-specific prevalence of the health measure to a standard life table for the same period. Findings Between 1991 and 2011, gains in life expectancy at age 65 years (4·5 years for men and 3·6 years for women) were accompanied by equivalent gains in years free of any cognitive impairment (4·2 years [95% CI 4·2–4·3] for men and 4·4 years [4·3–4·5] for women) and decreased years with mild or moderate–severe cognitive impairment. Gains were also identified in years in excellent or good self-perceived health (3·8 years [95% CI 3·5–4·1] for men and 3·1 years [2·7–3·4] for women). Gains in disability-free years were much smaller than those in excellent–good self-perceived health or those free from cognitive impairment, especially for women (0·5 years [0·2–0·9] compared with 2·6 years [2·3–2·9] for men), mostly because of increased mild disability. Interpretation During the past two decades in England, we report an absolute compression (ie, reduction) of cognitive impairment, a relative

  4. Terrestrial ages of Antarctic meteorites: Implications for concentration mechanisms

    NASA Technical Reports Server (NTRS)

    Schultz, L.

    1986-01-01

    Antarctic meteorites differ from meteorites fallen in other places in their mean terrestrial ages. Boeckl estimated the terrestrial half-life for the disintegration of stone meteorites by weathering under the climatic conditions of the Western United States to be about 3600 years. Antarctic meteorites, however, have terrestrial ages up to 70000 years, indicating larger weathering half-lives. The terrestrial ages of meteorites are determined by their concentration of cosmic-ray-produced radionuclides with suitable half-lives (C-14, Al-26, and Cl-36). These radionuclides have yielded reliable ages for the Antarctic meteorites. The distribution of terrestrial ages of Allan Hills and Yamato meteorites are examined.

  5. Great Expectations.

    ERIC Educational Resources Information Center

    Sullivan, Patricia

    1999-01-01

    Parents must learn to transmit a sense of high expectations to their children (related to behavior and accomplishments) without crushing them with too much pressure. This means setting realistic expectations based on their children's special abilities, listening to their children's feelings about the expectations, and understanding what…

  6. Aging and Cortical Mechanisms of Speech Perception in Noise

    ERIC Educational Resources Information Center

    Wong, Patrick C. M.; Jin, James Xumin; Gunasekera, Geshri M.; Abel, Rebekah; Lee, Edward R.; Dhar, Sumitrajit

    2009-01-01

    Spoken language processing in noisy environments, a hallmark of the human brain, is subject to age-related decline, even when peripheral hearing might be intact. The present study examines the cortical cerebral hemodynamics (measured by fMRI) associated with such processing in the aging brain. Younger and older subjects identified single words in…

  7. Age of Acquisition: Its Neural and Computational Mechanisms

    ERIC Educational Resources Information Center

    Hernandez, Arturo E.; Li, Ping

    2007-01-01

    The acquisition of new skills over a life span is a remarkable human ability. This ability, however, is constrained by age of acquisition (AoA); that is, the age at which learning occurs significantly affects the outcome. This is most clearly reflected in domains such as language, music, and athletics. This article provides a perspective on the…

  8. On the use of mean groundwater age, life expectancy and capture probability for defining aquifer vulnerability and time-of-travel zones for source water protection.

    PubMed

    Molson, J W; Frind, E O

    2012-01-01

    Protection and sustainability of water supply wells requires the assessment of vulnerability to contamination and the delineation of well capture zones. Capture zones, or more generally, time-of-travel zones corresponding to specific contaminant travel times, are most commonly delineated using advective particle tracking. More recently, the capture probability approach has been used in which a probability of capture of P=1 is assigned to the well and the growth of a probability-of-capture plume is tracked backward in time using an advective-dispersive transport model. This approach accounts for uncertainty due to local-scale heterogeneities through the use of macrodispersion. In this paper, we develop an alternative approach to capture zone delineation by applying the concept of mean life expectancy E (time remaining before being captured by the well), and we show how life expectancy E is related to capture probability P. Either approach can be used to delineate time-of-travel zones corresponding to specific travel times, as well as the ultimate capture zone. The related concept of mean groundwater age A (time since recharge) can also be applied in the context of defining the vulnerability of a pumped aquifer. In the same way as capture probability, mean life expectancy and groundwater age account for local-scale uncertainty or unresolved heterogeneities through macrodispersion, which standard particle tracking neglects. The approach is tested on 2D and 3D idealized systems, as well as on several watershed-scale well fields within the Regional Municipality of Waterloo, Ontario, Canada.

  9. Chelation: A Fundamental Mechanism of Action of AGE Inhibitors, AGE Breakers, and Other Inhibitors of Diabetes Complications

    SciTech Connect

    Nagai, Rhoji; Murray, David B.; Metz, Thomas O.; Baynes, John

    2012-03-01

    Advanced glycation or glycoxidation end-products (AGE) increase in tissue proteins with age, and their rate of accumulation is increased in diabetes, nephropathy and inflammatory diseases. AGE inhibitors include a range of compounds that are proposed to act by trapping carbonyl and dicarbonyl intermediates in AGE formation. However, some among the newer generation of AGE inhibitors lack reactive functional groups that would trap reaction intermediates, indicating an alternative mechanism of action. We propose that AGE inhibitors function primarily as chelators, inhibiting metal-catalyzed oxidation reactions. The AGE-inhibitory activity of angiotensin-converting enzyme inhibitors and angiotensin receptor blockers is also consistent with their chelating activity. Finally, compounds described as AGE breakers, or their hydrolysis products, also have strong chelating activity, suggesting that these compounds also act through their chelating activity. We conclude that chelation is the common, and perhaps the primary, mechanism of action of AGE inhibitors and breakers, and that chronic, mild chelation therapy should prove useful in treatment of diabetes and age-related diseases characterized by oxidative stress, inflammation and increased chemical modification of tissue proteins by advanced glycoxidation and lipoxidation end-products.

  10. Clinicians’ Expectations of Web 2.0 as a Mechanism for Knowledge Transfer of Stroke Best Practices

    PubMed Central

    David, Isabelle; Rochette, Annie

    2012-01-01

    Background Health professionals are increasingly encouraged to adopt an evidence-based practice to ensure greater efficiency of their services. To promote this practice, several strategies exist: distribution of educational materials, local consensus processes, educational outreach visits, local opinion leaders, and reminders. Despite these strategies, gaps continue to be observed between practice and scientific evidence. Therefore, it is important to implement innovative knowledge transfer strategies that will change health professionals’ practices. Through its interactive capacities, Web 2.0 applications are worth exploring. As an example, virtual communities of practice have already begun to influence professional practice. Objective This study was initially developed to help design a Web 2.0 platform for health professionals working with stroke patients. The aim was to gain a better understanding of professionals’ perceptions of Web 2.0 before the development of the platform. Methods A qualitative study following a phenomenological approach was chosen. We conducted individual semi-structured interviews with clinicians and managers. Interview transcripts were subjected to a content analysis. Results Twenty-four female clinicians and managers in Quebec, Canada, aged 28-66 participated. Most participants identified knowledge transfer as the most useful outcome of a Web 2.0 platform. Respondents also expressed their need for a user-friendly platform. Accessibility to a computer and the Internet, features of the Web 2.0 platform, user support, technology skills, and previous technological experience were found to influence perceived ease of use and usefulness. Our results show that the perceived lack of time of health professionals has an influence on perceived behavioral intention to use it despite favorable perception of the usefulness of the Web 2.0 platform. Conclusions In conclusion, female health professionals in Quebec believe that Web 2.0 may be a useful

  11. Human fear extinction and return of fear using reconsolidation update mechanisms: The contribution of on-line expectancy ratings

    PubMed Central

    Warren, Victor Taylor; Anderson, Kemp M.; Kwon, Cliffe; Bosshardt, Lauren; Jovanovic, Tanja; Bradley, Bekh; Norrholm, Seth Davin

    2015-01-01

    Disruption of the reconsolidation of conditioned fear memories has been suggested as a non-pharmacological means of preventing the return of learned fear in human populations. A reconsolidation update paradigm was developed in which a reconsolidation window is opened by a single isolated retrieval trial of a previously reinforced CS+ which is then followed by Extinction Training within that window. However, follow-up studies in humans using multi-methods fear conditioning indices (e.g., fear-potentiated startle, skin conductance, US-expectancy) have failed to replicate the retrieval + extinction effects. In the present study, we further investigated the retrieval + extinction reconsolidation update paradigm by directly comparing the acquisition, extinction, and return of fear-potentiated startle in the absence or presence of US-expectancy measures (using a trial-by-trial response keypad) with and without retrieval of a previously acquired CS-US association. Participants were fear conditioned to two visual cue CS+'s, one of which was presented as a single, isolated retrieval trial before Extinction Training and one that was extinguished as usual. The results show that the inclusion of US-expectancy measures strengthens the CS–US association to provide enhanced fear conditioning and maintenance of fear memories over the experimental sessions. In addition, in the groups that used on-line US-expectancy measures, the retrieval + extinction procedure reduced reinstatement of fear-potentiated startle to both previously reinforced CS+'s, as compared to the extinction as usual group. PMID:24183839

  12. Meeting the Expectation of Industry: An Integrated Approach for the Teaching of Mechanics and Electronics to Design Students

    ERIC Educational Resources Information Center

    Bingham, Guy A.; Southee, Darren J.; Page, Tom

    2015-01-01

    This paper examines the traditional engineering-based provision delivered to Product Design and Technology (B.Sc.) undergraduates at the Loughborough Design School and questions its relevancy against the increasing expectations of industry. The paper reviews final-year design projects to understand the level of transference of engineering-based…

  13. Exceeding Expectations

    ERIC Educational Resources Information Center

    Cannon, John

    2011-01-01

    Awareness of expectations is so important in the facilities business. The author's experiences has taught him that it is essential to understand how expectations impact people's lives as well as those for whom they provide services for every day. This article presents examples and ideas that will provide insight and ideas to help educators…

  14. Obesity and Life Expectancy with and without Diabetes in Adults Aged 55 Years and Older in the Netherlands: A Prospective Cohort Study

    PubMed Central

    Ligthart, Symen; Peeters, Anna; Hofman, Albert; Nusselder, Wilma; Franco, Oscar H.

    2016-01-01

    Background Overweight and obesity are associated with increased risk of type 2 diabetes. Limited evidence exists regarding the effect of excess weight on years lived with and without diabetes. We aimed to determine the association of overweight and obesity with the number of years lived with and without diabetes in a middle-aged and elderly population. Methods and Findings The study included 6,499 individuals (3,656 women) aged 55 y and older from the population-based Rotterdam Study. We developed a multistate life table to calculate life expectancy for individuals who were normal weight, overweight, and obese and the difference in years lived with and without diabetes. For life table calculations, we used prevalence, incidence rate, and hazard ratios (HRs) for three transitions (healthy to diabetes, healthy to death, and diabetes to death), stratifying by body mass index (BMI) at baseline and adjusting for confounders. During a median follow-up of 11.1 y, we observed 697 incident diabetes events and 2,192 overall deaths. Obesity was associated with an increased risk of developing diabetes (HR: 2.13 [p < 0.001] for men and 3.54 [p < 0.001] for women). Overweight and obesity were not associated with mortality in men and women with or without diabetes. Total life expectancy remained unaffected by overweight and obesity. Nevertheless, men with obesity aged 55 y and older lived 2.8 (95% CI −6.1 to −0.1) fewer y without diabetes than normal weight individuals, whereas, for women, the difference between obese and normal weight counterparts was 4.7 (95% CI −9.0 to −0.6) y. Men and women with obesity lived 2.8 (95% CI 0.6 to 6.2) and 5.3 (95% CI 1.6 to 9.3) y longer with diabetes, respectively, compared to their normal weight counterparts. Since the implications of these findings could be limited to middle-aged and older white European populations, our results need confirmation in other populations. Conclusions Obesity in the middle aged and elderly is associated

  15. Discover the network mechanisms underlying the connections between aging and age-related diseases.

    PubMed

    Yang, Jialiang; Huang, Tao; Song, Won-Min; Petralia, Francesca; Mobbs, Charles V; Zhang, Bin; Zhao, Yong; Schadt, Eric E; Zhu, Jun; Tu, Zhidong

    2016-01-01

    Although our knowledge of aging has greatly expanded in the past decades, it remains elusive why and how aging contributes to the development of age-related diseases (ARDs). In particular, a global mechanistic understanding of the connections between aging and ARDs is yet to be established. We rely on a network modelling named "GeroNet" to study the connections between aging and more than a hundred diseases. By evaluating topological connections between aging genes and disease genes in over three thousand subnetworks corresponding to various biological processes, we show that aging has stronger connections with ARD genes compared to non-ARD genes in subnetworks corresponding to "response to decreased oxygen levels", "insulin signalling pathway", "cell cycle", etc. Based on subnetwork connectivity, we can correctly "predict" if a disease is age-related and prioritize the biological processes that are involved in connecting to multiple ARDs. Using Alzheimer's disease (AD) as an example, GeroNet identifies meaningful genes that may play key roles in connecting aging and ARDs. The top modules identified by GeroNet in AD significantly overlap with modules identified from a large scale AD brain gene expression experiment, supporting that GeroNet indeed reveals the underlying biological processes involved in the disease. PMID:27582315

  16. Discover the network mechanisms underlying the connections between aging and age-related diseases

    PubMed Central

    Yang, Jialiang; Huang, Tao; Song, Won-min; Petralia, Francesca; Mobbs, Charles V.; Zhang, Bin; Zhao, Yong; Schadt, Eric E.; Zhu, Jun; Tu, Zhidong

    2016-01-01

    Although our knowledge of aging has greatly expanded in the past decades, it remains elusive why and how aging contributes to the development of age-related diseases (ARDs). In particular, a global mechanistic understanding of the connections between aging and ARDs is yet to be established. We rely on a network modelling named “GeroNet” to study the connections between aging and more than a hundred diseases. By evaluating topological connections between aging genes and disease genes in over three thousand subnetworks corresponding to various biological processes, we show that aging has stronger connections with ARD genes compared to non-ARD genes in subnetworks corresponding to “response to decreased oxygen levels”, “insulin signalling pathway”, “cell cycle”, etc. Based on subnetwork connectivity, we can correctly “predict” if a disease is age-related and prioritize the biological processes that are involved in connecting to multiple ARDs. Using Alzheimer’s disease (AD) as an example, GeroNet identifies meaningful genes that may play key roles in connecting aging and ARDs. The top modules identified by GeroNet in AD significantly overlap with modules identified from a large scale AD brain gene expression experiment, supporting that GeroNet indeed reveals the underlying biological processes involved in the disease. PMID:27582315

  17. Age-related hearing loss: ear and brain mechanisms.

    PubMed

    Frisina, Robert D

    2009-07-01

    Loss of sensory function in the aged has serious consequences for economic productivity, quality of life, and healthcare costs in the billions each year. Understanding the neural and molecular bases will pave the way for biomedical interventions to prevent, slow, or reverse these conditions. This chapter summarizes new information regarding age changes in the auditory system involving both the ear (peripheral) and brain (central). A goal is to provide findings that have implications for understanding some common biological underpinnings that affect sensory systems, providing a basis for eventual interventions to improve overall sensory functioning, including the chemical senses.

  18. Human fear extinction and return of fear using reconsolidation update mechanisms: the contribution of on-line expectancy ratings.

    PubMed

    Warren, Victor Taylor; Anderson, Kemp M; Kwon, Cliffe; Bosshardt, Lauren; Jovanovic, Tanja; Bradley, Bekh; Norrholm, Seth Davin

    2014-09-01

    Disruption of the reconsolidation of conditioned fear memories has been suggested as a non-pharmacological means of preventing the return of learned fear in human populations. A reconsolidation update paradigm was developed in which a reconsolidation window is opened by a single isolated retrieval trial of a previously reinforced CS+ which is then followed by Extinction Training within that window. However, follow-up studies in humans using multi-methods fear conditioning indices (e.g., fear-potentiated startle, skin conductance, US-expectancy) have failed to replicate the retrieval+extinction effects. In the present study, we further investigated the retrieval+extinction reconsolidation update paradigm by directly comparing the acquisition, extinction, and return of fear-potentiated startle in the absence or presence of US-expectancy measures (using a trial-by-trial response keypad) with and without retrieval of a previously acquired CS-US association. Participants were fear conditioned to two visual cue CS+'s, one of which was presented as a single, isolated retrieval trial before Extinction Training and one that was extinguished as usual. The results show that the inclusion of US-expectancy measures strengthens the CS-US association to provide enhanced fear conditioning and maintenance of fear memories over the experimental sessions. In addition, in the groups that used on-line US-expectancy measures, the retrieval+extinction procedure reduced reinstatement of fear-potentiated startle to both previously reinforced CS+'s, as compared to the extinction as usual group.

  19. Cellular senescence in aging and age-related disease: from mechanisms to therapy

    PubMed Central

    Childs, Bennett G; Durik, Matej; Baker, Darren J; van Deursen, Jan M

    2016-01-01

    Cellular senescence, a process that imposes permanent proliferative arrest on cells in response to various stressors, has emerged as a potentially important contributor to aging and age-related disease, and it is an attractive target for therapeutic exploitation. A wealth of information about senescence in cultured cells has been acquired over the past half century; however, senescence in living organisms is poorly understood, largely because of technical limitations relating to the identification and characterization of senescent cells in tissues and organs. Furthermore, newly recognized beneficial signaling functions of senescence suggest that indiscriminately targeting senescent cells or modulating their secretome for anti-aging therapy may have negative consequences. Here we discuss current progress and challenges in understanding the stressors that induce senescence in vivo, the cell types that are prone to senesce, and the autocrine and paracrine properties of senescent cells in the contexts of aging and age-related diseases as well as disease therapy. PMID:26646499

  20. Cellular senescence in aging and age-related disease: from mechanisms to therapy.

    PubMed

    Childs, Bennett G; Durik, Matej; Baker, Darren J; van Deursen, Jan M

    2015-12-01

    Cellular senescence, a process that imposes permanent proliferative arrest on cells in response to various stressors, has emerged as a potentially important contributor to aging and age-related disease, and it is an attractive target for therapeutic exploitation. A wealth of information about senescence in cultured cells has been acquired over the past half century; however, senescence in living organisms is poorly understood, largely because of technical limitations relating to the identification and characterization of senescent cells in tissues and organs. Furthermore, newly recognized beneficial signaling functions of senescence suggest that indiscriminately targeting senescent cells or modulating their secretome for anti-aging therapy may have negative consequences. Here we discuss current progress and challenges in understanding the stressors that induce senescence in vivo, the cell types that are prone to senesce, and the autocrine and paracrine properties of senescent cells in the contexts of aging and age-related diseases as well as disease therapy.

  1. Mechanical characteristics of aged Hinoki wood from Japanese historical buildings

    NASA Astrophysics Data System (ADS)

    Yokoyama, Misao; Gril, Joseph; Matsuo, Miyuki; Yano, Hiroyuki; Sugiyama, Junji; Clair, Bruno; Kubodera, Sigeru; Mistutani, Takumi; Sakamoto, Minoru; Ozaki, Hiromasa; Imamura, Mineo; Kawai, Shuichi

    2009-09-01

    Wood is present in many cultural heritage objects in Japan thanks to its capacity to resist over a long period of time. However, the evolution of its properties in regular use remains insufficiently known. The present study on the effect of wood aging takes advantage of the Japanese context where building traditions have been maintained for centuries. 3-point bending tests were performed in longitudinal (L) and radial (R) directions on small clear wood specimens cut from 8 historical samples and one modern reference considered of high quality by craftsmen. Although aged wood appeared more rigid and stronger than recent wood, after density and humidity corrections were applied no significant variation of L and R rigidity or L strength was observed. The post-linear behaviour, however, was drastically influenced by wood age especially in R direction where the strength and rupture energy decreased markedly with the time elapsed since the wood was processed. Well preserved aged wood considered as safe as long as it is not loaded perpendicular to grain. To cite this article: M. Yokoyama et al., C. R. Physique 10 (2009).

  2. Impact of aging mechanism on model simulated carbonaceous aerosols

    PubMed Central

    Huang, Y.; Wu, S.; Dubey, M.K.; French, N. H. F.

    2013-01-01

    Carbonaceous aerosols including organic carbon and black carbon have significant implications for both climate and air quality. In the current global climate or chemical transport models, a fixed hydrophobic-to-hydrophilic conversion lifetime for carbonaceous aerosol (τ) is generally assumed, which is usually around one day. We have implemented a new detailed aging scheme for carbonaceous aerosols in a chemical transport model (GEOS-Chem) to account for both the chemical oxidation and the physical condensation-coagulation effects, where τ is affected by local atmospheric environment including atmospheric concentrations of water vapor, ozone, hydroxyl radical and sulfuric acid. The updated τ exhibits large spatial and temporal variations with the global average (up to 11 km altitude) calculated to be 2.6 days. The chemical aging effects are found to be strongest over the tropical regions driven by the low ozone concentrations and high humidity there. The τ resulted from chemical aging generally decreases with altitude due to increases in ozone concentration and decreases in humidity. The condensation-coagulation effects are found to be most important for the high-latitude areas, in particular the polar regions, where the τ values are calculated to be up to 15 days. When both the chemical aging and condensation-coagulation effects are considered, the total atmospheric burdens and global average lifetimes of BC, black carbon, (OC, organic carbon) are calculated to increase by 9% (3%) compared to the control simulation, with considerable enhancements of BC and OC concentrations in the Southern Hemisphere. Model evaluations against data from multiple datasets show that the updated aging scheme improves model simulations of carbonaceous aerosols for some regions, especially for the remote areas in the Northern Hemisphere. The improvement helps explain the persistent low model bias for carbonaceous aerosols in the Northern Hemisphere reported in literature. Further

  3. [Oxidative stress and inflammation: hypothesis for the mechanism of aging].

    PubMed

    Tsubota, Kazuo

    2007-03-01

    Oxidative stress due to free radicals is related to the pathogenesis of many chronic disorders including cancer, inflammation, and neurological diseases. Oxidative stress such as aging and light exposure is also considered to be associated with age-related macular degeneration and cataract. The ocular surface is chronically exposed to oxidative stress including ultraviolet light, the oxygen in air, and changes in oxygen pressure due to blinking. We demonstrated that a rat dry eye model with a jogging board showed corneal epithelial disoders and elevated levels of oxidative stress, suggesting that the pathogenesis of epithelial disorders in dry eye with low frequency of blinking is related to oxidative stress. Next, using a model of laser-induced choroidal neovascularization (CNV), we showed that angiotensin receptormediated inflammation is required for the development of CNV. We also demonstrated that mice deficient in superoxide dismutase (SOD) showed typical clinical features of AMD. Finally, we proposed our thoughts about regenerative medicine, that is, to maintain quiescent stem cells, we have to regulate the aging of stem cells. PMID:17402562

  4. Chelation: a fundamental mechanism of action of AGE inhibitors, AGE breakers, and other inhibitors of diabetes complications.

    PubMed

    Nagai, Ryoji; Murray, David B; Metz, Thomas O; Baynes, John W

    2012-03-01

    This article outlines evidence that advanced glycation end product (AGE) inhibitors and breakers act primarily as chelators, inhibiting metal-catalyzed oxidation reactions that catalyze AGE formation. We then present evidence that chelation is the most likely mechanism by which ACE inhibitors, angiotensin receptor blockers, and aldose reductase inhibitors inhibit AGE formation in diabetes. Finally, we note several recent studies demonstrating therapeutic benefits of chelators for diabetic cardiovascular and renal disease. We conclude that chronic, low-dose chelation therapy deserves serious consideration as a clinical tool for prevention and treatment of diabetes complications.

  5. Mesenchymal stem cell aging: Mechanisms and influences on skeletal and non-skeletal tissues

    PubMed Central

    Liu, Huijuan; Xia, Xuechun

    2015-01-01

    The aging population and the incidence of aging-related diseases such as osteoporosis are on the rise. Aging at the tissue and organ levels usually involves tissue stem cells. Human and animal model studies indicate that aging affects two aspects of mesenchymal stem cell (MSC): a decrease in the bone marrow MSC pool and biased differentiation into adipocyte at the cost of osteoblast, which underlie the etiology of osteoporosis. Aging of MSC cells is also detrimental to some non-skeletal tissues, in particular the hematopoietic system, where MSCs serve as a niche component. In addition, aging compromises the therapeutic potentials of MSC cells, including cells isolated from aged individuals or cells cultured for many passages. Here we discuss the recent progress on our understanding of MSC aging, with a focus on the effects of MSC aging on bone remodeling and hematopoiesis and the mechanisms of MSC aging. PMID:26088863

  6. Functional unity of the thymus and pineal gland and study of the mechanisms of aging.

    PubMed

    Polyakova, V O; Linkova, N S; Kvetnoy, I M; Khavinson, V Kh

    2011-09-01

    The data on the morphology and functions of the thymus and pineal gland in individuals of different age are analyzed and common mechanisms of involution of these organs during aging and the consequencies of this process are discussed. Based on the data on the molecular changes in the thymus and pineal gland during aging, the authors hypothesize the functional unity of these organs and their mutual complementarity in the maintenance of normal immune and endocrine status during aging.

  7. Great Expectations.

    ERIC Educational Resources Information Center

    Smith, Jana J.

    2000-01-01

    Discusses how some universities are proactively looking to improve, enhance, and increase student housing on-campus through new and renovated residence halls that meet and exceed the expectations of today's students. Renovation improvements related to maximizing security, enhancing a homelike environment; developing a sense of community, and…

  8. [Mechanisms of the immune system ageing and some age-associated diseases].

    PubMed

    Witkowski, Jacek M

    2014-01-01

    In this paper the concept of homeostenosis (progressive reduction of ability to adapt producing loss of effectiveness) of the immune system is presented as a cause of the system ageing. In particular, the progression of immune system homeostenosis was shown to be associated with previous or ongoing chronic inflammatory diseases, including rheumatoid arthritis, type 2 diabetes, chronic kidney disease and Alzheimer's disease.

  9. Elevated RhoA/Rho-kinase activity in the aged rat penis: mechanism for age-associated erectile dysfunction.

    PubMed

    Jin, Liming; Liu, Tongyun; Lagoda, Gwen A; Champion, Hunter C; Bivalacqua, Trinity J; Burnett, Arthur L

    2006-03-01

    Epidemiologic studies have shown that aging accounts significantly for the prevalence of erectile dysfunction (ED). The pathophysiology of ED during aging and its underlying molecular mechanisms are largely unknown. We hypothesized that increased RhoA/Rho-kinase signaling is a major factor in the pathogenesis of age-associated ED and the mechanism involves increased penile smooth muscle contractility through inhibition of myosin light chain phosphatase. Male Fischer 344 young (4 month old) and aged (20-22 month old) rats underwent erectile function testing in vivo by measuring intracavernosal pressure (ICP) and mean arterial blood pressure (MAP) upon electrical stimulation of the cavernous nerve. The data demonstrated that erectile function was significantly lower in aged rats than that in young rats at all voltages tested (P<0.05). Western blot analysis results showed that there were no significant changes in protein expressions of RhoA, Rho-kinase-alpha and -beta isoforms, and myosin light chain phosphatase target subunit (MYPT1); however, membrane-bound RhoA and phosphorylated MYPT1 were increased in aged rat penes by 95 +/- 15 and 56 +/- 8% (P<0.05), respectively, indicating enhanced RhoA and Rho-kinase activity. Inhibition of Rho-kinase with Y27632 maximally increased ICP/MAP to 0.72 +/- 0.05 in aged rats vs. 0.47 +/- 0.06 in young rats (P<0.05). Gene transfer of adeno-associated virus (AAV) encoding dominant negative RhoA (T19NRhoA) to penes of aged and young rats for 7 days markedly improved erectile function in aged rats when compared with that in young rats (P<0.05). These observations were also supported by Rho-kinase activity assay results showing that basal Rho-kinase activity in aged rat penes receiving AAV vehicle treatment was twofold greater than that in young rat penes receiving AAV vehicle treatment, while it was reduced to a level similar to that in young rat penes after gene therapy of T19NRhoA (P<0.05). Taken together, these data suggest that

  10. Great Expectations for "Great Expectations."

    ERIC Educational Resources Information Center

    Ridley, Cheryl

    Designed to make the study of Dickens'"Great Expectations" an appealing and worthwhile experience, this paper presents a unit of study intended to help students gain (1) an appreciation of Dickens' skill at creating realistic human characters; (2) an insight into the problems of a young man confused by false values and unreal ambitions and ways to…

  11. Degradation of mechanical behavior in UHMWPE after natural and accelerated aging.

    PubMed

    Edidin, A A; Jewett, C W; Kalinowski, A; Kwarteng, K; Kurtz, S M

    2000-07-01

    Ultra-high molecular weight polyethylene (UHMWPE) is known to degrade during natural (shelf) aging following gamma irradiation in air, but the mechanical signature of degradation remains poorly understood. Accelerated aging methods have been developed to reproduce the natural aging process as well as to precondition total joint replacement components prior to joint simulator wear testing. In this study, we compared the mechanical behavior of naturally (shelf) aged and accelerated aged tibial inserts using a previously validated miniature specimen testing technique known as the small punch test. Tibial inserts made-of GUR 1120 and sterilized with 25 to 40 kGy of gamma radiation (in air) in 1988, 1993, and 1997 were obtained; a subset of the 1997 implants were subjected to 4 weeks of accelerated aging in air at 80 degrees C. To determine the spatial variation of mechanical properties within each insert, miniature disk shaped specimens were machined from the surface and subsurface regions of the inserts. Analysis of variance of the test data showed that aging significantly affected the small punch test measures of elastic modulus, initial load, ultimate load, ultimate displacement, and work to failure. The accelerated aging protocol was unable to reproduce the spatial mechanical profile seen in shelf aged components, but it did mechanically degrade the surface of GUR 1120 tibial components to an extent comparable to that seen after 10 years of natural aging. Test specimens showed a fracture morphology consistent with the decreased ductility and toughness which was corroborated by the small punch test metrics of this study. Our data support the hypothesis that UHMWPE undergoes a spatially nonuniform change towards a less ductile (more brittle) mechanical behavior after gamma irradiation in air and shelf aging.

  12. [Single mechanism of remodelling extracellular matrix in thymus and pineal gland at aging].

    PubMed

    Lin'kova, N S; Poliakova, V O; Kvetnoĭ, I M

    2011-01-01

    The expression of matrix metalloproteinase 2 and 9 in thymus and pineal gland has been verified. These data demonstrate single mechanism of remodelling extracellular matrix in thymus and pineal gland at aging.

  13. The Role of Exercise in Cardiac Aging: From Physiology to Molecular Mechanisms.

    PubMed

    Roh, Jason; Rhee, James; Chaudhari, Vinita; Rosenzweig, Anthony

    2016-01-22

    Aging induces structural and functional changes in the heart that are associated with increased risk of cardiovascular disease and impaired functional capacity in the elderly. Exercise is a diagnostic and therapeutic tool, with the potential to provide insights into clinical diagnosis and prognosis, as well as the molecular mechanisms by which aging influences cardiac physiology and function. In this review, we first provide an overview of how aging impacts the cardiac response to exercise, and the implications this has for functional capacity in older adults. We then review the underlying molecular mechanisms by which cardiac aging contributes to exercise intolerance, and conversely how exercise training can potentially modulate aging phenotypes in the heart. Finally, we highlight the potential use of these exercise models to complement models of disease in efforts to uncover new therapeutic targets to prevent or treat heart disease in the aging population.

  14. Aging affects mechanical properties and lubricin/PRG4 gene expression in normal ligaments.

    PubMed

    Thornton, Gail M; Lemmex, Devin B; Ono, Yohei; Beach, Cara J; Reno, Carol R; Hart, David A; Lo, Ian K Y

    2015-09-18

    Age-related changes in ligament properties may have clinical implications for injuries in the mature athlete. Previous preclinical models documented mechanical and biochemical changes in ligaments with aging. The purpose of this study was to investigate the effect of aging on ligament properties (mechanical, molecular, biochemical) by comparing medial collateral ligaments (MCLs) from 1-year-old and 3-year-old rabbits. The MCLs underwent mechanical (n=7, 1-year-old; n=7, 3-year-old), molecular (n=8, 1-year-old; n=6, 3-year-old), collagen and glycosaminoglycan (GAG) content (n=8, 1-year-old; n=6, 3-year-old) and water content (n=8, 1-year-old; n=5, 3-year-old) assessments. Mechanical assessments evaluated total creep strain, failure strain, ultimate tensile strength and modulus. Molecular assessments using RT-qPCR evaluated gene expression for collagens, proteoglycans, hormone receptors, and matrix metalloproteinases and their inhibitors. While total creep strain and ultimate tensile strength were not affected by aging, failure strain was increased and modulus was decreased comparing MCLs from 3-year-old rabbits to those from 1-year-old rabbits. The mRNA expression levels for lubricin/proteoglycan 4 (PRG4) and tissue inhibitor of metalloproteinase-3 increased with aging; whereas, the mRNA expression levels for estrogen receptor and matrix metalloproteinase-1 decreased with aging. Collagen and GAG content assays and water content assessments did not demonstrate any age-related changes. The increased failure strain and decreased modulus with aging may have implications for increased susceptibility to ligament damage/injury with aging. Lubricin/PRG4 gene expression was affected by aging and its speculated role in ligament function may be related to interfascicular lubrication, which in turn may lead to altered mechanical function with aging and increases in potential for injury.

  15. Omega-3 fatty acids and brain resistance to ageing and stress: body of evidence and possible mechanisms.

    PubMed

    Denis, I; Potier, B; Vancassel, S; Heberden, C; Lavialle, M

    2013-03-01

    The increasing life expectancy in the populations of rich countries raises the pressing question of how the elderly can maintain their cognitive function. Cognitive decline is characterised by the loss of short-term memory due to a progressive impairment of the underlying brain cell processes. Age-related brain damage has many causes, some of which may be influenced by diet. An optimal diet may therefore be a practical way of delaying the onset of age-related cognitive decline. Nutritional investigations indicate that the ω-3 poyunsaturated fatty acid (PUFA) content of western diets is too low to provide the brain with an optimal supply of docosahexaenoic acid (DHA), the main ω-3 PUFA in cell membranes. Insufficient brain DHA has been associated with memory impairment, emotional disturbances and altered brain processes in rodents. Human studies suggest that an adequate dietary intake of ω-3 PUFA can slow the age-related cognitive decline and may also protect against the risk of senile dementia. However, despite the many studies in this domain, the beneficial impact of ω-3 PUFA on brain function has only recently been linked to specific mechanisms. This review examines the hypothesis that an optimal brain DHA status, conferred by an adequate ω-3 PUFA intake, limits age-related brain damage by optimizing endogenous brain repair mechanisms. Our analysis of the abundant literature indicates that an adequate amount of DHA in the brain may limit the impact of stress, an important age-aggravating factor, and influences the neuronal and astroglial functions that govern and protect synaptic transmission. This transmission, particularly glutamatergic neurotransmission in the hippocampus, underlies memory formation. The brain DHA status also influences neurogenesis, nested in the hippocampus, which helps maintain cognitive function throughout life. Although there are still gaps in our knowledge of the way ω-3 PUFA act, the mechanistic studies reviewed here indicate that

  16. Simulating expected elevation dependent warming (EDW) mechanisms in a dynamically-downscaled perturbed physics climate model ensemble over the Himalayan region

    NASA Astrophysics Data System (ADS)

    Forsythe, N. D.; Blenkinsop, S.; Fowler, H. J.; Betts, R.; Janes, T.

    2014-12-01

    Current theoretical climatology suggests three key climate processes - snow cover contribution to surface albedo, cloud cover prevalence and near surface water vapour - influencing the surface energy balance are expected to exhibit elevation-gradients in global warming-driven changes. These gradients are in turn expected to act as mechanisms contributing to EDW. This study examines the simulation of these mechanisms and their influence on projections of EDW in a dynamically downscaled transient perturbed physics ensemble (PPE). The downscaling experiment in question is the Hadley Centre Regional Model version 3 PRECIS configuration (HadRM3P) 25km simulation over the South Asian domain driven by the MetOffice 17-member QUMP (Quantifying Uncertainty in Model Projections) ensemble of the Hadley Centre Climate Model version 3 (HadCM3). Use of the multi-member PPE enables quantification of uncertainty in projected changes in climate variables - albedo, cloud cover, water vapour and near surface temperature - while the spatial resolution of a RCM improves insight into the role of elevation in projected rates of change. This work specifically addresses the Regional Climate Model (RCM) representation of expected EDW mechanisms by calculating vertical profiles (relative to modelled surface elevation of downscaled grid cells) for changes in: [1] albedo, i.e. the ratio of future to control period albedo where albedo is calculated as one minus the ratio of absorbed surface solar radiation to incoming surface solar radiation; [2] shortwave cloud radiative effect (CRE), i.e. the ratio of future to present CRE where CRE is calculated as incoming "top of atmosphere" shortwave radiation minus incoming surface shortwave radiation; [3] near surface water vapour -- in terms of specific humidity (Qair) - and related down-welling longwave radiation, but because previous EDW research has shown non-linearity in Qair radiative influence, changes in Qair is evaluated in both delta (additive

  17. 77 FR 41457 - Aging Management Associated With Wall Thinning Due to Erosion Mechanisms

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-07-13

    ... Register on June 22, 2010 (75 FR 35510). The NRC staff has developed draft LR-ISG-2012-01 to: (a) Revise... COMMISSION Aging Management Associated With Wall Thinning Due to Erosion Mechanisms AGENCY: Nuclear... Interim Staff Guidance (LR-ISG), LR-ISG-2012-01, ``Wall Thinning Due to Erosion Mechanisms.'' The draft...

  18. The Essential Mechanisms of Aging: What Have We Learnt in Ten Years?

    PubMed

    Yin, Dazhong

    2016-01-01

    Carbonylation due to oxidation and glycation is an important biochemical cause of degenerative diseases and aging. While the enigma of aging is understood as a result of molecular dysfunction due to the failure of maintenance systems, a brief history of the interpretation of aging mechanisms and the exact biochemistry connecting entropy and biological aging is addressed. Lipofuscin formation mechanisms resulting in irreparable accumulative changes represent the most important aging- related alterations of entropy increase in biological kingdom, which is very different from the damage-based "aging" process of inorganic materials. A fifth level of aging mechanism investigations that highlights the importance of functional groups of biochemistry, the "missing codes" of life science, is put forward in this review. Significance and validities of such 'life codes' in biology beyond genomic and proteomic concepts has also been clarified. An open-minded consideration of functional groups of biomolecules, such as carbonyl groups, may help to explain the mechanisms of fatigue and sleep in terms of neurobiochemistry and biological pharmaco-medicine.

  19. A comparative study of commercial lithium ion battery cycle life in electrical vehicle: Aging mechanism identification

    NASA Astrophysics Data System (ADS)

    Han, Xuebing; Ouyang, Minggao; Lu, Languang; Li, Jianqiu; Zheng, Yuejiu; Li, Zhe

    2014-04-01

    When lithium-ion batteries age with cycling, the battery capacity decreases and the resistance increases. The aging mechanism of different types of lithium-ion batteries differs. The loss of lithium inventory, loss of active material, and the increase in resistance may result in battery aging. Generally, analysis of the battery aging mechanism requires dismantling of batteries and using methods such as X-ray diffraction and scanning electron microscopy. These methods may permanently damage the battery. Therefore, the methods are inappropriate for the battery management system (BMS) in an electric vehicle. The constant current charging curves while charging the battery could be used to get the incremental capacity and differential voltage curves for identifying the aging mechanism; the battery state-of-health can then be estimated. This method can be potentially used in the BMS for online diagnostic and prognostic services. The genetic algorithm could be used to quantitatively analyze the battery aging offline. And the membership function could be used for onboard aging mechanism identification.

  20. Cardiac Aging: From Molecular Mechanisms to Significance in Human Health and Disease

    PubMed Central

    Dai, Dao-Fu; Chen, Tony; Johnson, Simon C.; Szeto, Hazel

    2012-01-01

    Abstract Cardiovascular diseases (CVDs) are the major causes of death in the western world. The incidence of cardiovascular disease as well as the rate of cardiovascular mortality and morbidity increase exponentially in the elderly population, suggesting that age per se is a major risk factor of CVDs. The physiologic changes of human cardiac aging mainly include left ventricular hypertrophy, diastolic dysfunction, valvular degeneration, increased cardiac fibrosis, increased prevalence of atrial fibrillation, and decreased maximal exercise capacity. Many of these changes are closely recapitulated in animal models commonly used in an aging study, including rodents, flies, and monkeys. The application of genetically modified aged mice has provided direct evidence of several critical molecular mechanisms involved in cardiac aging, such as mitochondrial oxidative stress, insulin/insulin-like growth factor/PI3K pathway, adrenergic and renin angiotensin II signaling, and nutrient signaling pathways. This article also reviews the central role of mitochondrial oxidative stress in CVDs and the plausible mechanisms underlying the progression toward heart failure in the susceptible aging hearts. Finally, the understanding of the molecular mechanisms of cardiac aging may support the potential clinical application of several “anti-aging” strategies that treat CVDs and improve healthy cardiac aging. PMID:22229339

  1. Effect of delayed aging on mechanical properties of an Al-Cu-Mg alloy

    SciTech Connect

    Ravindranathan, S.P.; Kashyap, K.T.; Kumar, S.R.; Ramachandra, C.; Chatterji, B.

    2000-02-01

    The effect of delayed aging on mechanical properties is characteristically found in Al-Mg-Si alloys. Delayed aging refers to the time elapsed between solutionizing and artificial aging. Delayed aging leads to inferior properties. This effect was investigated in an Al-Cu-Mg alloy (AU2GN) of nominal composition Al-2Cu-1.5Mg-1Fe-1Ni as a function of delay. This alloy also showed a drop in mechanical properties with delay. The results are explained on the basis of Pashley's kinetic model to qualitatively explain the evolution of a coarse precipitate structure with delay. It is found that all the results of delayed aging in the Al-Cu-Mg alloys are similar to those found in Al-Mg-Si alloys.

  2. Molecular Mechanisms of Age-Related Sleep Loss in the Fruit Fly

    PubMed Central

    Robertson, Meagan; Keene, Alex C.

    2013-01-01

    Across phyla, aging is associated with reduced sleep duration and efficiency. Both aging and sleep involve complex genetic architecture and diverse cell types and are heavily influenced by diet and environment. Therefore, understanding the molecular mechanisms of age-dependent changes in sleep will require integrative approaches that go beyond examining these two processes independently. The fruit fly, Drosophila melanogaster, provides a genetically amenable system for dissecting the molecular basis of these processes. In this review, we examine the role of metabolism and circadian rhythms in age-dependent sleep loss. PMID:23594925

  3. Fission track ages and Exhumation mechanisms of the Tauern Window, Eastern Alps

    NASA Astrophysics Data System (ADS)

    Bertrand, Audrey; Rosenberg, Claudio; Garcia, Sebastian

    2010-05-01

    The Tauern Window (TW) is a thermal and structural dome which exposes Penninic basement, its cover units as well as parts of the overlying Austroalpine basement in the central part of the Eastern Alps. The peak of metamorphism was attained approximately at 30Ma (Selverstone et .al, 1992), followed by cooling and exhumation throughout Miocene time. Most of the tertiary exhumation of the Eastern Alps was localized in the TW, from Early Oligocene to late Miocene time. A current debate centers on the exhumation mechanisms of Penninic rocks in the core of the TW, namely to assess whether orogen-parallel extension (e.g., Selverstone, 1988) or a combination of folding and erosion (eg., Rosenberg et al., 2004) with subordinate extension were the controlling processes. E-W extension is well documented at the western (Brenner Fault) and eastern (Katschberg Fault) margins of the window (e.g., Behrmann, 1988; Selverstone, 1988; Genser and Neubauer, 1989). In contrast, upright folding dominates the internal structure of the dome, and in particular along its western part, where fold amplitudes, mostly eroded during folding, attained up to 10 km. This study attempts to assess the relative importance of folding and erosion and of orogen-parallel extension during exhumation by analyzing the spatial and temporal cooling patterns of apatite and zircon fission track ages. The compilation of published apatite and zircon fission track ages indicates a concentric younging of both the apatite and zircon ages toward the core of the TW. The concentric isochrones follow the map trace of the axial planes of the upright folds of the western and eastern TW. This cooling pattern is in contrast to the one expected by a process of extensional unroofing, which in map view would results in isochrons parallel to the extensional faults and progressively younging towards them (e.g., Foster et al., 2001). We therefore propose that folding and erosion were primarily responsible for exhuming the Penninic

  4. The emerging role of Notch pathway in ageing: Focus on the related mechanisms in age-related diseases.

    PubMed

    Balistreri, Carmela Rita; Madonna, Rosalinda; Melino, Gerry; Caruso, Calogero

    2016-08-01

    Notch signaling is an evolutionarily conserved pathway, which is fundamental for the development of all tissues, organs and systems of human body. Recently, a considerable and still growing number of studies have highlighted the contribution of Notch signaling in various pathological processes of the adult life, such as age-related diseases. In particular, the Notch pathway has emerged as major player in the maintenance of tissue specific homeostasis, through the control of proliferation, migration, phenotypes and functions of tissue cells, as well as in the cross-talk between inflammatory cells and the innate immune system, and in onset of inflammatory age-related diseases. However, until now there is a confounding evidence about the related mechanisms. Here, we discuss mechanisms through which Notch signaling acts in a very complex network of pathways, where it seems to have the crucial role of hub. Thus, we stress the possibility to use Notch pathway, the related molecules and pathways constituting this network, both as innovative (predictive, diagnostic and prognostic) biomarkers and targets for personalised treatments for age-related diseases. PMID:27328278

  5. Impact of temperature on the aging mechanisms of arsenic in soils: fractionation and bioaccessibility.

    PubMed

    Huang, Guanxing; Chen, Zongyu; Wang, Jia; Hou, Qinxuan; Zhang, Ying

    2016-03-01

    The present study focused on the influence of temperature variation on the aging mechanisms of arsenic in soils. The results showed that higher temperature aggravated the decrease of more mobilizable fractions and the increase of less mobilizable or immobilizable fractions in soils over time. During the aging process, the redistribution of both carbonate-bound fraction and specifically sorbed and organic-bound fraction in soils occurred at various temperatures, and the higher temperature accelerated the redistribution of specifically sorbed and organic-bound fraction. The aging processes of arsenic in soils at different temperatures were characterized by several stages, and the aging processes were not complete within 180 days. Arsenic bioaccessibility in soils decreased significantly by the aging, and the decrease was intensified by the higher temperature. In terms of arsenic bioaccessibility, higher temperature accelerated the aging process of arsenic in soils remarkably.

  6. Why AMD is a disease of ageing and not of development: mechanisms and insights

    PubMed Central

    Sharma, Kaushal; Sharma, Neel Kamal; Anand, Akshay

    2014-01-01

    Ageing disorders can be defined as the progressive and cumulative outcome of several defective cellular mechanisms as well as metabolic pathways, consequently resulting in degeneration. Environment plays an important role in its pathogenesis. In contrast, developmental disorders arise from inherited mutations and usually the role of environmental factors in development of disease is minimal. Age related macular degeneration (AMD) is one such retinal degenerative disorder which starts with the progression of age. Metabolism plays an important role in initiation of such diseases of ageing. Cholesterol metabolism and their oxidized products like 7-ketocholesterol have been shown to adversely impact retinal pigment epithelium (RPE) cells. These molecules can initiate mitochondrial apoptotic processes and also influence the complements factors and expression of angiogenic proteins like VEGF etc. In this review we highlight why and how AMD is an ageing disorder and not a developmental disease substantiated by disrupted cholesterol metabolism common to several age related diseases. PMID:25071560

  7. Stem Cell-Specific Mechanisms Ensure Genomic Fidelity within HSCs and upon Aging of HSCs.

    PubMed

    Moehrle, Bettina M; Nattamai, Kalpana; Brown, Andreas; Florian, Maria C; Ryan, Marnie; Vogel, Mona; Bliederhaeuser, Corinna; Soller, Karin; Prows, Daniel R; Abdollahi, Amir; Schleimer, David; Walter, Dagmar; Milsom, Michael D; Stambrook, Peter; Porteus, Matthew; Geiger, Hartmut

    2015-12-22

    Whether aged hematopoietic stem and progenitor cells (HSPCs) have impaired DNA damage repair is controversial. Using a combination of DNA mutation indicator assays, we observe a 2- to 3-fold increase in the number of DNA mutations in the hematopoietic system upon aging. Young and aged hematopoietic stem cells (HSCs) and hematopoietic progenitor cells (HPCs) do not show an increase in mutation upon irradiation-induced DNA damage repair, and young and aged HSPCs respond very similarly to DNA damage with respect to cell-cycle checkpoint activation and apoptosis. Both young and aged HSPCs show impaired activation of the DNA-damage-induced G1-S checkpoint. Induction of chronic DNA double-strand breaks by zinc-finger nucleases suggests that HSPCs undergo apoptosis rather than faulty repair. These data reveal a protective mechanism in both the young and aged hematopoietic system against accumulation of mutations in response to DNA damage. PMID:26686632

  8. Stem cell specific mechanisms ensure genomic fidelity within HSCs and upon aging of HSCs

    PubMed Central

    Moehrle, Bettina M.; Nattamai, Kalpana; Brown, Andreas; Florian, Maria C.; Ryan, Marnie; Vogel, Mona; Bliederhaeuser, Corinna; Soller, Karin; Prows, Daniel R.; Abdollahi, Amir; Schleimer, David; Walter, Dagmar; Milsom, Michael D.; Stambrook, Peter; Porteus, Matthew; Geiger, Hartmut

    2015-01-01

    Whether aged hematopoietic stem and progenitor cells (HSPCs) have impaired DNA damage repair is controversial. Using a combination of DNA mutation indicator assays, we observe a 2-3 fold increase in the number of DNA mutations in the hematopoietic system upon aging. Young and aged HSCs and HPCs do not show an increase in mutation upon irradiation-induced DNA damage repair, and young and aged HSPCs respond very similarly to DNA damage with respect to cell cycle checkpoint activation and apoptosis. Both, young and aged HSPCs show impaired activation of the DNA-damage induced G1-S checkpoint. Induction of chronic DNA double strand breaks by zinc-finger nucleases suggest that HSPCs undergo apoptosis rather than faulty repair. These data reveal a protective mechanism in both the young and aged hematopoietic system against accumulation of mutations in response to DNA damage. PMID:26686632

  9. Age-specific profiles of tissue-level composition and mechanical properties in murine cortical bone.

    PubMed

    Raghavan, Mekhala; Sahar, Nadder D; Kohn, David H; Morris, Michael D

    2012-04-01

    There is growing evidence that bone composition and tissue-level mechanical properties are significant determinants of skeletal integrity. In the current study, Raman spectroscopy and nanoindentation testing were co-localized to analyze tissue-level compositional and mechanical properties in skeletally mature young (4 or 5 months) and old (19 months) murine femora at similar spatial scales. Standard multivariate linear regression analysis revealed age-dependent patterns in the relationships between mechanical and compositional properties at the tissue scale. However, changes in bone material properties with age are often complex and nonlinear, and can be missed with linear regression and correlation-based methods. A retrospective data mining approach was implemented using non-linear multidimensional visualization and classification to identify spectroscopic and nanoindentation metrics that best discriminated bone specimens of different age-classes. The ability to classify the specimens into the correct age group increased by using combinations of Raman and nanoindentation variables (86-96% accuracy) as compared to using individual measures (59-79% accuracy). Metrics that best classified 4 or 5 month and 19 month specimens (2-age classes) were mineral to matrix ratio, crystallinity, modulus and plasticity index. Metrics that best distinguished between 4, 5 and 19 month specimens (3-age classes) were mineral to matrix ratio, crystallinity, modulus, hardness, cross-linking, carbonate to phosphate ratio, creep displacement and creep viscosity. These findings attest to the complexity of mechanisms underlying bone tissue properties and draw attention to the importance of considering non-linear interactions between tissue-level composition and mechanics that may work together to influence material properties with age. The results demonstrate that a few non-linearly combined compositional and mechanical metrics provide better discriminatory information than a single metric

  10. Mechanical properties of cables exposed to simultaneous thermal and radiation aging

    SciTech Connect

    Jacobus, M.J. ); Fuehrer, G.F. )

    1990-01-01

    Sandia National Laboratories is conducting long-term aging research on representative samples of nuclear power plant Class 1E cables. The objectives of this program are to determine the suitability of these cables for extended life (beyond the 40-year design basis) and to assess various cable condition monitoring (CM) techniques for predicting remaining cable life. This paper provides the results of mechanical measurements that were performed on cable specimens cross-linked polyethylene neoprene jackets: chlorinated polyethylene jackets, fiberglass braid jackets, and chlorosulfonated polyethylene jackets aged at relatively mild, simultaneous thermal and radiation exposure conditions for periods of up to nine months. After aging, some of the aged samples, as well as some unaged samples, were exposed to accident gamma radiation at ambient temperature. The mechanical measurements discussed in this paper include tensile strength, ultimate elongation, and compressive modulus. 10 refs., 22 figs., 2 tabs.

  11. Accelerating aging of zirconia femoral head implants: change of surface structure and mechanical properties.

    PubMed

    Chowdhury, S; Vohra, Yogesh K; Lemons, Jack E; Ueno, Masaru; Ikeda, Junji

    2007-05-01

    Recently, alternations of zirconia ceramic femoral heads of total hip prostheses during in vivo conditions have caused concern in the medical disciplines regarding phase transformation of zirconia prosthetic components. In this paper, we have investigated the mechanical and structural properties of different laboratory aged zirconia femoral heads and correlated changes in mechanical properties with the phase compositions of the sample. From laser microscope observation, cross-sectional Scanning electron microscopy imaging, and X-ray diffraction analysis on the surface of the zirconia femoral heads, we found monoclinic to tetragonal phase transformation in zirconia prostheses over time during the aging process in the laboratory. Mechanical properties, mainly hardness (H) and Young's modulus (E) values, were measured by nanoindentation technique on the surface of these implants. The results showed that both H and E values decreased with increased monoclinic phase in zirconia, thus confirming a phase transformation over time during aging.

  12. In Situ Mechanical Analysis of Myofibrillar Perturbation and Aging on Soft, Bilayered Drosophila Myocardium

    PubMed Central

    Kaushik, Gaurav; Fuhrmann, Alexander; Cammarato, Anthony; Engler, Adam J.

    2011-01-01

    Drosophila melanogaster is a genetically malleable organism with a short life span, making it a tractable system in which to study mechanical effects of genetic perturbation and aging on tissues, e.g., impaired heart function. However, Drosophila heart-tube studies can be hampered by its bilayered structure: a ventral muscle layer covers the contractile cardiomyocytes. Here we propose an atomic force microscopy-based analysis that uses a linearized-Hertz method to measure individual mechanical components of soft composite materials. The technique was verified using bilayered polydimethylsiloxane. We further demonstrated its biological utility via its ability to resolve stiffness changes due to RNA interference to reduce myofibrillar content or due to aging in Drosophila myocardial layers. This protocol provides a platform to assess the mechanics of soft biological composite systems and, to our knowledge, for the first time, permits direct measurement of how genetic perturbations, aging, and disease can impact cardiac function in situ. PMID:22261050

  13. A comparative study of expectant parents ' childbirth expectations.

    PubMed

    Kao, Bi-Chin; Gau, Meei-Ling; Wu, Shian-Feng; Kuo, Bih-Jaw; Lee, Tsorng-Yeh

    2004-09-01

    The purpose of this study was to understand childbirth expectations and differences in childbirth expectations among expectant parents. For convenience sampling, 200 couples willing to participate in this study were chosen from two hospitals in central Taiwan. Inclusion criteria were at least 36 weeks of gestation, aged 18 and above, no prenatal complications, and willing to consent to participate in this study. Instruments used to collect data included basic demographic data and the Childbirth Expectations Questionnaire. Findings of the study revealed that (1) five factors were identified by expectant parents regarding childbirth expectations including the caregiving environment, expectation of labor pain, spousal support, control and participation, and medical and nursing support; (2) no general differences were identified in the childbirth expectations between expectant fathers and expectant mothers; and (3) expectant fathers with a higher socioeconomic status and who had received prenatal (childbirth) education had higher childbirth expectations, whereas mothers displayed no differences in demographic characteristics. The study results may help clinical healthcare providers better understand differences in expectations during labor and birth and childbirth expectations by expectant parents in order to improve the medical and nursing system and promote positive childbirth experiences and satisfaction for expectant parents.

  14. Aging Leads to a Dysregulation in Mechanically Driven Bone Formation and Resorption.

    PubMed

    Razi, Hajar; Birkhold, Annette I; Weinkamer, Richard; Duda, Georg N; Willie, Bettina M; Checa, Sara

    2015-10-01

    Physical activity is essential to maintain skeletal mass and structure, but its effect seems to diminish with age. To test the hypothesis that bone becomes less sensitive to mechanical strain with age, we used a combined in vivo/in silico approach. We investigated how maturation and aging influence the mechanical regulation of bone formation and resorption to 2 weeks of noninvasive in vivo controlled loading in mice. Using 3D in vivo morphometrical assessment of longitudinal microcomputed tomography images, we quantified sites in the mouse tibia where bone was deposited or resorbed in response to controlled in vivo loading. We compared the (re)modeling events (formation/resorption/quiescent) to the mechanical strains induced at these sites (predicted using finite element analysis). Mice of all age groups (young, adult, and elderly) responded to loading with increased formation and decreased resorption, preferentially at high strains. Low strains were associated with no anabolic response in adult and elderly mice, whereas young animals showed a strong response. Adult animals showed a clear separation between strain ranges where formation and resorption occurred but without an intermediate quiescent "lazy zone". This strain threshold disappeared in elderly mice, as mechanically induced (re)modeling became dysregulated, apparent in an inability to inhibit resorption or initiate formation. Contrary to what is generally believed until now, aging does not shift the mechanical threshold required to initiate formation or resorption, but rather blurs its specificity. These data suggest that pharmaceutical strategies augmenting physical exercise should consider this dysfunction in the mechanical regulation of bone (re)modeling to more effectively combat age-related bone loss.

  15. Investigation of mechanical properties of modern dental composites after artificial aging for one year.

    PubMed

    Hahnel, Sebastian; Henrich, Anne; Bürgers, Ralf; Handel, Gerhard; Rosentritt, Martin

    2010-01-01

    This in vitro study investigated the aging behavior of dental composites with regard to surface roughness (SR), Vickers hardness (VH) and flexural strength (FS), and the study elucidated the impact of artificial aging parameters. One hundred and sixty-five rectangular specimens were prepared from five composites (Filtek Supreme XT, Filtek Silorane, CeramX, Quixfil, experimental ormocer) and subjected to various artificial aging protocols (storage in distilled water/ethanol/artificial saliva for 7, 90 and 365 days; thermal cycling, 2 x 3000 cycles 5/55 degrees C). SR, VH and FS were determined at baseline and after each aging treatment. Means and standard deviations were calculated; statistical analysis was performed using three-way ANOVA and the Tukey-Kramer multiple comparison test (alpha=.05). The results showed a significant influence in the composite and aging duration on mechanical parameters; the aging medium did not have a significant influence on VH and FS, but there was a significant influence on SR. The highest overall VH was found for theexperimental ormocer; Filtek Silorane yielded the lowest values. For FS, the significantly highest values were found for Filtek Silorane, and the lowest values were found for the experimental ormocer. Prolonged aging periods (90 or 365 days) or thermal cycling led to significant decreases in both VH and FS and significant increases in SR. The findings of the current study indicate that composites differ significantly for SR and its mechanical properties with regard to FS and VH, as well as in aging behavior. Generally, artificial aging leads to a significant decrease in mechanical properties, which underlines the relevance of continuous improvement of dental composites.

  16. DNA methylation, an epigenetic mechanism connecting folate to healthy embryonic development and aging

    PubMed Central

    Kim, Kyong-chol; Friso, Simonetta; Choi, Sang-Woon

    2009-01-01

    Experimental studies demonstrated that maternal exposure to certain environmental and dietary factors during early embryonic development can influence the phenotype of offspring as well as the risk of disease development at the later life. DNA methylation, an epigenetic phenomenon, has been suggested as a mechanism by which maternal nutrients affect the phenotype of their offspring in both honeybee and agouti mouse models. Phenotypic changes through DNA methylation can be linked to folate metabolism by the knowledge that folate, a coenzyme of one-carbon metabolism, is directly involved in methyl group transfer for DNA methylation. During the fetal period, organ-specific DNA methylation patterns are established through epigenetic reprogramming. However, established DNA methylation patterns are not immutable and can be modified during our life time by the environment. Aberrant changes in DNA methylation with diet may lead to the development of age-associated diseases including cancer. It is also known that the aging process by itself is accompanied by alterations in DNA methylation. Diminished activity of DNA methyltransferases (Dnmts) can be a potential mechanism for the decreased genomic DNA methylation during aging, along with reduced folate intake and altered folate metabolism. Progressive hypermethylation in promoter regions of certain genes is observed throughout aging and repression of tumor suppressors induced by this epigenetic mechanism appears to be associated with cancer development. In this review we address the effect of folate on early development and aging through an epigenetic mechanism, DNA methylation. PMID:19733471

  17. Contribution of impaired mitochondrial autophagy to cardiac aging: mechanisms and therapeutic opportunities

    PubMed Central

    Dutta, Debapriya; Calvani, Riccardo; Bernabei, Roberto; Leeuwenburgh, Christiaan; Marzetti, Emanuele

    2012-01-01

    The prevalence of cardiovascular disease (CVD) increases with advancing age. While the long-term exposure to cardiovascular risk factors plays a major role in the etiopathogenesis of CVD, intrinsic cardiac aging enhances the susceptibility to developing heart pathologies in late life. The progressive decline of cardiomyocyte mitochondrial function is considered to be a major mechanism underlying heart senescence. Damaged mitochondria not only produce less ATP, but also generate increased amounts of reactive oxygen species (ROS) and display a greater propensity to trigger apoptosis. Given the post-mitotic nature of cardiomyocytes, the efficient removal of dysfunctional mitochondria is critical for the maintenance of cell homeostasis, as damaged organelles cannot be diluted by cell proliferation. The only known mechanism whereby mitochondria are turned over is through macroautophagy (MA). The efficiency of this process declines with advancing age which may play a critical role in heart senescence as well as in age-related CVD. This review illustrates the putative mechanisms whereby alterations in the autophagic removal of damaged mitochondria intervene in the process of cardiac aging as well as in the pathogenesis of specific heart diseases especially prevalent in late life (e.g., left ventricular hypertrophy, ischemic heart disease, heart failure, and diabetic cardiomyopathy). Interventions proposed to counter cardiac aging through improvements in MA (e.g., calorie restriction and calorie restriction mimetics) are also presented. PMID:22499902

  18. Study on the behavior and mechanism of polycarbonate with hot-water aging

    NASA Astrophysics Data System (ADS)

    Kong, L. P.; Zhao, Y. X.; Zhou, C. H.; Huang, Y. H.; Tang, M.; Gao, J. G.

    2016-07-01

    The present work was concerned with hot-water aging behavior and mechanism of Bisphenol A polycarbonate (PC) used as food and packaging materials. It indicated that with the aging time prolonged, PC sample had internal defects and the mechanical properties of PC materials changed not too much, molecular weight decreased, thermal stability declined. Phenolic hydroxyl absorption intensity enhanced in IR spectra and the maximum absorption wavelength red shift of benzene in UV-Vis spectra, the level of BPA increased. The color change of PC sample was not apparent.

  19. Aging behavior and mechanical properties of maraging steels in the presence of submicrocrystalline Laves phase particles

    SciTech Connect

    Mahmoudi, A.; Ghavidel, M.R. Zamanzad; Nedjad, S. Hossein; Heidarzadeh, A.; Ahmadabadi, M. Nili

    2011-10-15

    Cold rolling and annealing of homogenized Fe-Ni-Mn-Mo-Ti-Cr maraging steels resulted in the formation of submicrocrystalline Fe{sub 2}(Mo,Ti) Laves phase particles. Optical and scanning electron microscopy, X-ray diffraction, tensile and hardness tests were used to study the microstructure, aging behavior and mechanical properties of the annealed steels. The annealed microstructures showed age hardenability during subsequent isothermal aging at 753 K. Ultrahigh fracture stress but poor tensile ductility was obtained after substantial age hardening in the specimens with 2% and 4% chromium. Increasing chromium addition up to 6% toughened the aged microstructure at the expense of the fracture stress by increasing the volume fraction of retained austenite. The Laves phase particles acted as crack nucleation sites during tensile deformation. - Highlights: {yields} Laves phases dispersed in a BCC iron matrix by annealing of cold rolled samples. {yields} The samples showed age hardenability during subsequent isothermal aging at 753 K. {yields} Ultrahigh fracture stress but poor ductility was obtained after age hardening. {yields} Increasing chromium addition toughened the aged microstructure. {yields} Laves phase particles acting as crack nucleation sites during tensile deformation.

  20. Mechanisms of cardioprotective effect of aged garlic extract against Doxorubicin-induced cardiotoxicity.

    PubMed

    Alkreathy, Huda M; Damanhouri, Zoheir A; Ahmed, Nessar; Slevin, Mark; Osman, Abdel-Moneim M

    2012-12-01

    Aged garlic has been extensively studied and has been shown to have a number of medicinal properties, including immunomodulatory, hepatoprotective, antimutagenic, anticarcinogenic, and antioxidant effects. The objective of this study was to investigate the mechanisms of the cardioprotective effect of aged garlic extract (AGE), a widely used herbal medicine with potent antioxidant activity, against doxorubicin-induced cardiotoxicity. Moreover, the study investigated if the cardioprotective effect of AGE might be at the expense of the antitumor effect of the anticancer drug doxorubicin (DOX). Primary cultured neonatal rat cardiac myocytes were treated with DOX, AGE, and their combination for 24 hours. DOX increased p53 and caspase 3 activity-induced apoptotic cell death, whereas AGE pretreatment suppressed the action of DOX. AGE pretreatment did not interfere with the cytotoxic activity of DOX, but it increased the DOX uptake into tumor cells and increased the long term survivors of tumor-bearing mice from 30% to 70%. In conclusion, DOX impairs viability of cardiac myocytes, at least partially by activating the p53-mediated apoptotic signaling. AGE can effectively and extensively counteract this action of DOX and may potentially protect the heart from severe toxicity of DOX. At the same time, AGE did not interfere with antitumor activity of DOX. PMID:22172987

  1. Age-Related Impairment of Pancreatic Beta-Cell Function: Pathophysiological and Cellular Mechanisms

    PubMed Central

    De Tata, Vincenzo

    2014-01-01

    The incidence of type 2 diabetes significantly increases with age. The relevance of this association is dramatically magnified by the concomitant global aging of the population, but the underlying mechanisms remain to be fully elucidated. Here, some recent advances in this field are reviewed at the level of both the pathophysiology of glucose homeostasis and the cellular senescence of pancreatic islets. Overall, recent results highlight the crucial role of beta-cell dysfunction in the age-related impairment of pancreatic endocrine function and delineate the possibility of new original therapeutic interventions. PMID:25232350

  2. Universal Aging Mechanism for Static and Sliding Friction of Metallic Nanoparticles.

    PubMed

    Feldmann, Michael; Dietzel, Dirk; Tekiel, Antoni; Topple, Jessica; Grütter, Peter; Schirmeisen, André

    2016-07-01

    The term "contact aging" refers to the temporal evolution of the interface between a slider and a substrate usually resulting in increasing friction with time. Current phenomenological models for multiasperity contacts anticipate that such aging is not only the driving force behind the transition from static to sliding friction, but at the same time influences the general dynamics of the sliding friction process. To correlate static and sliding friction on the nanoscale, we show experimental evidence of stick-slip friction for nanoparticles sliding on graphite over a wide dynamic range. We can assign defined periods of aging to the stick phases of the particles, which agree with simulations explicitly including contact aging. Additional slide-hold-slide experiments for the same system allow linking the sliding friction results to static friction measurements, where both friction mechanisms can be universally described by a common aging formalism. PMID:27447515

  3. Universal Aging Mechanism for Static and Sliding Friction of Metallic Nanoparticles

    NASA Astrophysics Data System (ADS)

    Feldmann, Michael; Dietzel, Dirk; Tekiel, Antoni; Topple, Jessica; Grütter, Peter; Schirmeisen, André

    2016-07-01

    The term "contact aging" refers to the temporal evolution of the interface between a slider and a substrate usually resulting in increasing friction with time. Current phenomenological models for multiasperity contacts anticipate that such aging is not only the driving force behind the transition from static to sliding friction, but at the same time influences the general dynamics of the sliding friction process. To correlate static and sliding friction on the nanoscale, we show experimental evidence of stick-slip friction for nanoparticles sliding on graphite over a wide dynamic range. We can assign defined periods of aging to the stick phases of the particles, which agree with simulations explicitly including contact aging. Additional slide-hold-slide experiments for the same system allow linking the sliding friction results to static friction measurements, where both friction mechanisms can be universally described by a common aging formalism.

  4. Universal Aging Mechanism for Static and Sliding Friction of Metallic Nanoparticles.

    PubMed

    Feldmann, Michael; Dietzel, Dirk; Tekiel, Antoni; Topple, Jessica; Grütter, Peter; Schirmeisen, André

    2016-07-01

    The term "contact aging" refers to the temporal evolution of the interface between a slider and a substrate usually resulting in increasing friction with time. Current phenomenological models for multiasperity contacts anticipate that such aging is not only the driving force behind the transition from static to sliding friction, but at the same time influences the general dynamics of the sliding friction process. To correlate static and sliding friction on the nanoscale, we show experimental evidence of stick-slip friction for nanoparticles sliding on graphite over a wide dynamic range. We can assign defined periods of aging to the stick phases of the particles, which agree with simulations explicitly including contact aging. Additional slide-hold-slide experiments for the same system allow linking the sliding friction results to static friction measurements, where both friction mechanisms can be universally described by a common aging formalism.

  5. Physical ageing of polyethylene terephthalate under natural sunlight: correlation study between crystallinity and mechanical properties

    NASA Astrophysics Data System (ADS)

    Aljoumaa, Khaled; Abboudi, Maher

    2016-01-01

    Semi-crystalline polyethylene terephthalate (PET) was aged under the effect of natural UV exposure and outdoor temperature during 670 days. The variation in the mechanical and thermal properties beside to the morphology was tracked by applying different analytical techniques, including scanning electron microscopy, infrared spectroscopy, differential scanning calorimetry and wide angle X-ray diffraction, in addition to tensile strength and hardness measurements. It has been confirmed that the ageing process is the results of physical trend only. The aged PET showed a decrease in both tensile strength and strain with an increase in the degree of crystallinity of aged PET samples during the whole period. These changes in crystallinity were examined by various analysis methods: density, calorimetric and infrared spectroscopy. New peaks in FTIR analysis at 1115 and 1090 cm-1 were characterized and proved that this technique is considered to be an easy tool to track the change in the surface crystallinity of aged PET samples directly. The results of this study showed that an augmentation in the degree of crystallinity of outdoor aged PET samples from 18 to 36 %, accompanied with a decrease in tensile strength from 167.9 to 133.7 MPa. Moreover, a good exponential correlation was found between the degree of crystallinity and the mechanical properties of the aged PET.

  6. Oxidative Damage and Cellular Defense Mechanisms in Sea Urchin Models of Aging

    PubMed Central

    Du, Colin; Anderson, Arielle; Lortie, Mae; Parsons, Rachel; Bodnar, Andrea

    2013-01-01

    The free radical or oxidative stress theory of aging proposes that the accumulation of oxidative cellular damage is a major contributor to the aging process and a key determinant of species longevity. This study investigates the oxidative stress theory in a novel model for aging research, the sea urchin. Sea urchins present a unique model for the study of aging due to the existence of species with tremendously different natural life spans including some species with extraordinary longevity and negligible senescence. Cellular oxidative damage, antioxidant capacity and proteasome enzyme activities were measured in the tissues of three sea urchin species: short-lived Lytechinus variegatus, long-lived Strongylocentrotus franciscanus and Strongylocentrotus purpuratus which has an intermediate lifespan. Levels of protein carbonyls and 4-hydroxynonenal (HNE) measured in tissues (muscle, nerve, esophagus, gonad, coelomocytes, ampullae) and 8-hydroxy-2’-deoxyguanosine (8-OHdG) measured in cell-free coelomic fluid showed no general increase with age. The fluorescent age-pigment lipofuscin measured in muscle, nerve and esophagus, increased with age however it appeared to be predominantly extracellular. Antioxidant mechanisms (total antioxidant capacity, superoxide dismutase) and proteasome enzyme activities were maintained with age. In some instances, levels of oxidative damage were lower and antioxidant activity higher in cells or tissues of the long-lived species compared to the short-lived species, however further studies are required to determine the relationship between oxidative damage and longevity in these animals. Consistent with the predictions of the oxidative stress theory of aging, the results suggest that negligible senescence is accompanied by a lack of accumulation of cellular oxidative damage with age and maintenance of antioxidant capacity and proteasome enzyme activities may be important mechanisms to mitigate damage. PMID:23707327

  7. Effects of aging on vasoconstrictor and mechanical properties of rat skeletal muscle arterioles

    NASA Technical Reports Server (NTRS)

    Muller-Delp, Judy; Spier, Scott A.; Ramsey, Michael W.; Lesniewski, Lisa A.; Papadopoulos, Anthony; Humphrey, J. D.; Delp, Michael D.

    2002-01-01

    Exercise capacity and skeletal muscle blood flow during exercise are reduced with advancing age. This reduction in blood flow capacity may be related to increased reactivity of skeletal muscle resistance vessels to vasoconstrictor stimuli. The purpose of this study was to test the hypothesis that aging results in increased vasoconstrictor responses of skeletal muscle resistance arterioles. First-order (1A) arterioles (90-220 microm) from the gastrocnemius and soleus muscles of young (4 mo) and aged (24 mo) Fischer-344 rats were isolated, cannulated, and pressurized via hydrostatic reservoirs. Vasoconstriction in response to increases in norepinephrine (NE; 1 x 10(-9)-1 x 10(-4) M) and KCl (20-100 mM) concentrations and increases in intraluminal pressure (10-130 cmH(2)O) were evaluated in the absence of flow. Responses to NE and KCl were similar in both soleus and gastrocnemius muscle arterioles from young and aged rats. In contrast, active myogenic responses to changes in intraluminal pressure were diminished in soleus and gastrocnemius arterioles from aged rats. To assess whether alterations in the mechanical properties of resistance arterioles underlie altered myogenic responsiveness, passive diameter responses to pressure and mechanical stiffness were evaluated. There was no effect of age on the structural behavior (passive pressure-diameter relationship) or stiffness of arterioles from either the soleus or gastrocnemius muscles. These results suggest that aging does not result in a nonspecific decrease in vasoconstrictor responsiveness of skeletal muscle arterioles. Rather, aging-induced adaptations of vasoreactivity of resistance arterioles appear to be limited to mechanisms that are uniquely involved in the signaling of the myogenic response.

  8. The fragile elderly hip: Mechanisms associated with age-related loss of strength and toughness☆

    PubMed Central

    Reeve, Jonathan; Loveridge, Nigel

    2014-01-01

    Every hip fracture begins with a microscopic crack, which enlarges explosively over microseconds. Most hip fractures in the elderly occur on falling from standing height, usually sideways or backwards. The typically moderate level of trauma very rarely causes fracture in younger people. Here, this paradox is traced to the decline of multiple protective mechanisms at many length scales from nanometres to that of the whole femur. With normal ageing, the femoral neck asymmetrically and progressively loses bone tissue precisely where the cortex is already thinnest and is also compressed in a sideways fall. At the microscopic scale of the basic remodelling unit (BMU) that renews bone tissue, increased numbers of actively remodelling BMUs associated with the reduced mechanical loading in a typically inactive old age augments the numbers of mechanical flaws in the structure potentially capable of initiating cracking. Menopause and over-deep osteoclastic resorption are associated with incomplete BMU refilling leading to excessive porosity, cortical thinning and disconnection of trabeculae. In the femoral cortex, replacement of damaged bone or bone containing dead osteocytes is inefficient, impeding the homeostatic mechanisms that match strength to habitual mechanical usage. In consequence the participation of healthy osteocytes in crack-impeding mechanisms is impaired. Observational studies demonstrate that protective crack deflection in the elderly is reduced. At the most microscopic levels attention now centres on the role of tissue ageing, which may alter the relationship between mineral and matrix that optimises the inhibition of crack progression and on the role of osteocyte ageing and death that impedes tissue maintenance and repair. This review examines recent developments in the understanding of why the elderly hip becomes fragile. This growing understanding is suggesting novel testable approaches for reducing risk of hip fracture that might translate into control

  9. Mechanical properties improvement of silica aerogel through aging: Role of solvent type, time and temperature

    NASA Astrophysics Data System (ADS)

    Omranpour, H.; Dourbash, A.; Motahari, S.

    2014-05-01

    Effective parameters that enhance mechanical properties during aging were investigated in the present study. Silica aerogels were made from tetraethyl orthosilicate (TEOS), water, methanol and NH4F in molar ratio 1:4:8:2×10-3 using a one-step method. Different time, temperature and aging solvents in aging stage were studied. Subsequently, solvent exchange with n-hexane, modification under TMCS solution and ambient pressure drying (APD) were performed for all samples. The aerogels had densities within the range of 0.1 and 0.6 g/cm3. The FTIR, mechanical properties, density and BET results, porosity, pore volume, pore diameter and surface area of the samples, were discussed. The compression properties of the gel increased with the increase in the time and temperature of aging. It was observed that solvents with more polarity improved polymerization, which enhanced the mechanical properties of the related samples. However, the stresses and capillary forces of water during drying were so large that inhibited "spring-back effect" during APD, and consequently a collapsed silica network with higher density was fabricated. In other words, the specific compression strength and modulus declined drastically. For methanol, alcohols inhibit the reactions inconveniently causing more shrinkage. In aging by n-hexane, capillary pressure declined significantly and thereby shrinkage was eliminated and silica aerogels with low bulk densities (0.095 g/cm3), high specific surface areas (600 m2/g), and large pore volumes (2.6 cm3/g) were synthesized.

  10. Mechanisms of Age-Related Decline in Memory Search across the Adult Life Span

    ERIC Educational Resources Information Center

    Hills, Thomas T.; Mata, Rui; Wilke, Andreas; Samanez-Larkin, Gregory R.

    2013-01-01

    Three alternative mechanisms for age-related decline in memory search have been proposed, which result from either reduced processing speed (global slowing hypothesis), overpersistence on categories (cluster-switching hypothesis), or the inability to maintain focus on local cues related to a decline in working memory (cue-maintenance hypothesis).…

  11. Damage Mechanisms of Filled Siloxanes for Predictive Multiscale Modeling of Aging Behavior

    SciTech Connect

    Balazs, B; Maxwell, R; de Teresa, S; Dinh, L; Gee, R

    2002-04-02

    Predictions of component performance versus lifetime are often risky for complex materials in which there may be many underlying aging or degradation mechanisms. In order to develop more accurate predictive models for silica-filled siloxane components, we are studying damage mechanisms over a broad range of size domains, linked together through several modeling efforts. Atomistic and molecular dynamic modeling has elucidated the chemistry of the silica filler to polymer interaction, as this interaction plays a key role in this material's aging behavior. This modeling work has been supported by experimental data on the removal of water from the silica surface, the effect of the surrounding polymer on this desiccation, and on the subsequent change in the mechanical properties of the system. Solid State NMR efforts have characterized the evolution of the polymer and filler dynamics as the material is damaged through irradiation or desiccation. These damage signatures have been confirmed by direct measurements of changes in polymer crosslink density and filler interaction as measured by solvent swelling, and by mechanical property tests. Data from the changes at these molecular levels are simultaneously feeding the development of age-aware constitutive models for polymer behavior. In addition, the microstructure of the foam, including under load, has been determined by Computed Tomography, and this data is being introduced into Finite Element Analysis codes to allow component level models. All of these techniques are directed towards the incorporation of molecular and microstructural aging signatures into predictive models for overall component performance.

  12. Dynamic strain aging of the materials characterized by the Peierls plasticity mechanism

    NASA Astrophysics Data System (ADS)

    Petukhov, B. V.

    2016-09-01

    A synergetic model is proposed to describe the influence of dynamic strain aging on the plasticity of materials that is controlled by the Peierls barriers overcome by dislocations. The immobilization of dislocations by the impurities concentrated in the dislocation cores is taken into account. The behavior of calculated deformation curves is studied as a function of the material parameters and the mechanical test conditions.

  13. Mechanical properties of human enamel as a function of age and location in the tooth.

    PubMed

    Park, Saejin; Wang, Duck H; Zhang, Dongsheng; Romberg, Elaine; Arola, Dwayne

    2008-06-01

    Aging and the related changes in mechanical behavior of hard tissues of the human body are becoming increasingly important. In this study the influence of aging on the mechanical behavior of human enamel was evaluated using 3rd molars from young (18 < or = age < or = 30 years) and old (55 < or = age) patients. The hardness and elastic modulus were quantified using nanoindentation as a function of distance from the Dentin-Enamel Junction (DEJ) and within three different regions of the crown (i.e. cervical, cuspal and inter-cuspal enamel). Results of the evaluation showed that the elastic modulus and hardness increased with distance from the DEJ in all three regions examined, regardless of patient age. The largest increases with distance from the DEJ occurred within the cervical region of the old enamel. Overall, the results showed that there were no age-dependent differences in properties of enamel near the DEJ. However, near the tooth's surface, both the hardness (p < 0.025) and elastic modulus (p < 0.0001) were significantly greater in the old enamel. At the surface of the tooth the average elastic modulus of "old" enamel was nearly 20% greater than that of enamel from the young patients.

  14. Influence of thermal aging on microstructure and mechanical properties of CLAM steel

    NASA Astrophysics Data System (ADS)

    Huang, Lixin; Hu, Xue; Yang, Chunguang; Yan, Wei; Xiao, Furen; Shan, Yiyin; Yang, Ke

    2013-11-01

    In order to investigate the influence of thermal aging on microstructure and mechanical properties of CLAM (China low activation martensitic) steel, a comparison study was made on the as-tempered and the aged steels. The tempered CLAM steels were subjected to aging treatment at 600 °C for 1100 h and 3000 h, and at 650 °C for 1100 h, respectively. The changes of microstructure were characterized by both transmission electron microscope (TEM) and scanning electron microscope (SEM). The mechanical properties were evaluated by Charpy impact, tensile and Vickers hardness tests. The upper shelf energy (USE) of the thermal aged CLAM steel decreased with the extension of aging time, while the yield strength changed slightly. After long-term thermal aging, the MX type precipitates remained stable. The coarsening of M23C6 and the formation of Laves phase were confirmed by scanning/transmission electron microscopes. The Laves phase was the main factor leading to the increase of DBTT.

  15. The effect of aging, temperature and brine composition on the mechanical strength of chalk

    NASA Astrophysics Data System (ADS)

    Korsnes, Reidar Inge; Nermoen, Anders; Stødle, Trond; Vika Storm, Eirik; Vadla Madland, Merete

    2014-05-01

    Chalk strength has been of great focus for several research communities since the 1980s when the Ekofisk subsidence problem was discovered. Sea water injection was initiated in 1987 to improve the oil production and to re-pressurize the reservoirs to halt the subsidence. The oil production was improved significantly, but the reservoir compaction in the water saturated regions continued, in contrast to the regions with no water breakthrough. This observation indicates a water weakening effect of the chalk. Extensive studies have been performed during the last decades to enlighten how the brine chemistry alters the rock mechanical properties. These studies have shown that the elastic bulk modulus, yield strength, creep and the deformation rate at constant stress conditions depend on the pore fluid composition. In general, the injected brine is in non-equilibrium with the rock surface inducing alteration of the rock mineralogy. In this study we examined two aspects of the mechanical strength, namely the bulk modulus and the onset of yield during hydrostatic stress loading with 0.7 MPa pore pressure. The test program consisted of aged and un-aged cores, ambient and 130°C test temperature, and four brine compositions: MgCl2, NaCl, Na2SO4, and synthetic sea water (SSW) at ion strengths of 0.657 M. The aging was performed by submerging saturated cores in a closed container with the respective test brine for three weeks at 130°C. Un-aged cores were saturated the same day as they were tested. For each brine composition we present four test setups; (a) aged and tested at 130°C, (b) aged and tested at ambient temperature, (c) un-aged and tested at 130°C, and (d) un-aged and tested at ambient conditions. The main results from our study are: 1. By using NaCl and MgCl2 as saturating brines, neither the test temperature nor the aging procedure affected the yield stress and bulk modulus significantly. 2. Using Na2SO4, the yield point and bulk moduli were reduced if the core

  16. Organic chemical aging mechanisms: An annotated bibliography. Waste Tank Safety Program

    SciTech Connect

    Samuels, W.D.; Camaioni, D.M.; Nelson, D.A.

    1993-09-01

    An annotated bibliography has been compiled of the potential chemical and radiological aging mechanisms of the organic constituents (non-ferrocyanide) that would likely be found in the UST at Hanford. The majority of the work that has been conducted on the aging of organic chemicals used for extraction and processing of nuclear materials has been in conjunction with the acid or PUREX type processes. At Hanford the waste being stored in the UST has been stabilized with caustic. The aging factors that were used in this work were radiolysis, hydrolysis and nitrite/nitrate oxidation. The purpose of this work was two-fold: to determine whether or not research had been or is currently being conducted on the species associated with the Hanford UST waste, either as a mixture or as individual chemicals or chemical functionalities, and to determine what areas of chemical aging need to be addressed by further research.

  17. Mechanisms of Muscle Denervation in Aging: Insights from a Mouse Model of Amyotrophic Lateral Sclerosis

    PubMed Central

    Park, Kevin H.J

    2015-01-01

    Muscle denervation at the neuromuscular junction (NMJ) is thought to be a contributing factor in age-related muscle weakness. Therefore, understanding the mechanisms that modulate NMJ innervation is a key to developing therapies to combat age-related muscle weakness affecting the elderly. Two mouse models, one lacking the Cu/Zn superoxide dismutase (SOD1) gene and another harboring the transgenic mutant human SOD1 gene, display progressive changes at the NMJ, including muscle endplate fragmentation, nerve terminal sprouting, and denervation. These changes at the NMJ share many of the common features observed in the NMJs of aged mice. In this review, research findings demonstrating the effects of PGC-1α, IGF-1, GDNF, MyoD, myogenin, and miR-206 on NMJ innervation patterns in the G93A SOD1 mice will be highlighted in the context of age-related muscle denervation. PMID:26425392

  18. Sarcopenia, cachexia and aging: diagnosis, mechanisms and therapeutic options - a mini-review.

    PubMed

    Ali, Sumbul; Garcia, Jose M

    2014-01-01

    By the year 2050, individuals over the age of 65 years will comprise 20% of the US population. Loss of muscle mass and strength is common in this age group and it is associated with increased dependence, frailty and mortality. Sarcopenia, defined as the loss of muscle mass and function associated with aging, and cachexia, defined as weight loss due to an underlying illness, are muscle wasting disorders of particular relevance in the aging population, but they go largely unrecognized. In this review we highlight the common pathophysiological mechanisms underlying muscle loss in sarcopenia and cachexia, the factors unique to each condition and means of diagnosing and differentiating them clinically. Therapeutic options including exercise, nutritional therapy, androgens and growth hormone as well as their practical limitations are discussed. We also shed light on newer agents being developed as potential therapeutic options for wasting diseases. PMID:24731978

  19. Mechanical heterogeneities in the subendothelial matrix develop with age and decrease with exercise.

    PubMed

    Kohn, Julie C; Chen, Adeline; Cheng, Stephanie; Kowal, Daniel R; King, Michael R; Reinhart-King, Cynthia A

    2016-06-14

    Arterial stiffening occurs with age and is associated with lack of exercise. Notably both age and lack of exercise are major cardiovascular risk factors. While it is well established that bulk arterial stiffness increases with age, more recent data suggest that the intima, the innermost arterial layer, also stiffens during aging. Micro-scale mechanical characterization of individual layers is important because cells primarily sense the matrix that they are in contact with and not necessarily the bulk stiffness of the vessel wall. To investigate the relationship between age, exercise, and subendothelial matrix stiffening, atomic force microscopy was utilized here to indent the subendothelial matrix of the thoracic aorta from young, aged-sedentary, and aged-exercised mice, and elastic modulus values were compared to conventional pulse wave velocity measurements. The subendothelial matrix elastic modulus was elevated in aged-sedentary mice compared to young or aged-exercised mice, and the macro-scale stiffness of the artery was found to linearly correlate with the subendothelial matrix elastic modulus. Notably, we also found that with age, there exists an increase in the point-to-point variations in modulus across the subendothelial matrix, indicating non-uniform stiffening. Importantly, this heterogeneity is reversible with exercise. Given that vessel stiffening is known to cause aberrant endothelial cell behavior, and the spatial heterogeneities we find exist on a length scale much smaller than the size of a cell, these data suggest that further investigation in the heterogeneity of the subendothelial matrix elastic modulus is necessary to fully understand the effects of physiological matrix stiffening on cell function.

  20. Effect of Cyclic Aging on Mechanical Properties and Microstructure of Maraging Steel 250

    NASA Astrophysics Data System (ADS)

    Tariq, Fawad; Naz, Nausheen; Baloch, Rasheed Ahmed

    2010-10-01

    The effects of thermal cyclic aging on mechanical properties and microstructure of maraging steel 250 were studied using hardness tester, tensile testing machine, impact tester, optical, scanning electron, and stereo microscopy. Samples were solution annealed at 1093 K for 1 h followed by air cooling to form bcc martensite. Cyclic aging treatments were carried out at 753 and 773 K for varying time periods. Increase in hardness and strength with corresponding decrease in ductility and impact strength was observed with increasing aging cycles. Reverted austenite was detected by x-ray diffraction technique formed as a result of cyclic aging. The presence of reverted γ was also confirmed by EDX-SEM analysis and attributed to the formation of Mo- and Ni-rich regions which transformed to γ on cooling. Heterogeneity in composition and amount of reverted γ was found to increase with increase in aging cycles and aging time. Fractography reveals the change in fracture mode from ductile dimple-like to brittle cleavage with increase in hardness and strength due to cyclic aging.

  1. Transient Fluid Flow Along Basement Faults and Rupture Mechanics: Can We Expect Injection-Induced Earthquake Behavior to Correspond Directly With Injection Operations?

    NASA Astrophysics Data System (ADS)

    Norbeck, J. H.; Horne, R. N.

    2015-12-01

    We explored injection-induced earthquake behavior in geologic settings where basement faults are connected hydraulically to overlying saline aquifers targeted for wastewater disposal. Understanding how the interaction between natural geology and injection well operations affects the behavior of injection-induced earthquake sequences has important implications for characterizing seismic hazard risk. Numerical experiments were performed to investigate the extent to which seismicity is influenced by the migration of pressure perturbations along fault zones. Two distinct behaviors were observed: a) earthquake ruptures that were confined to the pressurized region of the fault and b) sustained earthquake ruptures that propagated far beyond the pressure front. These two faulting mechanisms have important implications for assessing the manner in which seismicity can be expected respond to injection well operations.Based upon observations from the numerical experiments, we developed a criterion that can be used to classify the expected faulting behavior near wastewater disposal sites. The faulting criterion depends on the state of stress, the initial fluid pressure, the orientation of the fault, and the dynamic friction coefficient of the fault. If the initial ratio of shear to effective normal stress resolved on the fault (the prestress ratio) is less than the fault's dynamic friction coefficient, then earthquake ruptures will tend to be limited by the distance of the pressure front. In this case, parameters that affect seismic hazard assessment, like the maximum earthquake magnitude or earthquake recurrence interval, could correlate with injection well operational parameters. For example, the maximum earthquake magnitude might be expected to grow over time in a systematic manner as larger patches of the fault are exposed to significant pressure changes. In contrast, if the prestress ratio is greater than dynamic friction, a stress drop can occur outside of the pressurized

  2. Comparison of biaxial mechanical properties of coronary sinus tissues from porcine, ovine and aged human species.

    PubMed

    Pham, Thuy; Sun, Wei

    2012-02-01

    Due to its proximity to the mitral valve, the coronary sinus (CS) vessel serves as a conduit for the deployment and implantation of the percutaneous transvenous mitral annuloplasty (PTMA) devices that can potentially reduce the mitral regurgitation. Because CS vessel is a venous tissue and seldom diseased, its mechanical properties have not been well studied. In this study, we performed a multi-axial mechanical test and histological analysis to characterize the mechanical and structural properties of the aged human, porcine and ovine CS tissues. The results showed that the aged human CS tissues exhibited much stiffer and highly anisotropic behaviors compared to the porcine and ovine. Both of the porcine and ovine CS vessel walls were thicker and mainly composed of striated muscle fibers (SMF), whereas the thinner aged human CS had higher collagen, less SMF, and more fragmented elastin fibers, which are possibly due to aging effects. We also observed that the anatomical features of porcine CS vessel might be not suitable for PTMA deployment. These differences between animal and human models raise questions for the validity of using animal models to investigate the biomechanics involved in the PTMA intervention. Therefore, caution must be taken in future studies of PTMA stents using animal models.

  3. Aging of running shoes and its effect on mechanical and biomechanical variables: implications for runners.

    PubMed

    Chambon, Nicolas; Sevrez, Violaine; Ly, Quoc Hung; Guéguen, Nils; Berton, Eric; Rao, Guillaume

    2014-01-01

    This study investigates the effect of running shoes' aging on mechanical and biomechanical parameters as a function of midsole materials (viscous, intermediate, elastic) and ground inclination. To this aim, heel area of the shoe (under calcaneal tuberosity) was first mechanically aged at realistic frequency and impact magnitudes based on a 660 km training plan. Stiffness (ST) and viscosity were then measured on both aged and matching new shoes, and repercussions on biomechanical variables (joint kinematics, muscular pre-activation, vertical ground reaction force and tibial acceleration) were assessed during a leg-extended stepping-down task designed to mimic the characteristics of running impacts. Shoes' aging led to increased ST (means: from 127 to 154 N ∙ mm(-1)) and decreased energy dissipation (viscosity) (means: from 2.19 to 1.88 J). The effects induced by mechanical changes on body kinematics were very small. However, they led with the elastic shoe to increased vastus lateralis pre-activation, tibial acceleration peak (means: from 4.5 g to 5.2 g) and rate. Among the three shoes tested, the shoe with intermediate midsole foam provided the best compromise between viscosity and elasticity. The optimum balance remains to be found for the design of shoes regarding at once cushioning, durability and injury prevention.

  4. Aging of running shoes and its effect on mechanical and biomechanical variables: implications for runners.

    PubMed

    Chambon, Nicolas; Sevrez, Violaine; Ly, Quoc Hung; Guéguen, Nils; Berton, Eric; Rao, Guillaume

    2014-01-01

    This study investigates the effect of running shoes' aging on mechanical and biomechanical parameters as a function of midsole materials (viscous, intermediate, elastic) and ground inclination. To this aim, heel area of the shoe (under calcaneal tuberosity) was first mechanically aged at realistic frequency and impact magnitudes based on a 660 km training plan. Stiffness (ST) and viscosity were then measured on both aged and matching new shoes, and repercussions on biomechanical variables (joint kinematics, muscular pre-activation, vertical ground reaction force and tibial acceleration) were assessed during a leg-extended stepping-down task designed to mimic the characteristics of running impacts. Shoes' aging led to increased ST (means: from 127 to 154 N ∙ mm(-1)) and decreased energy dissipation (viscosity) (means: from 2.19 to 1.88 J). The effects induced by mechanical changes on body kinematics were very small. However, they led with the elastic shoe to increased vastus lateralis pre-activation, tibial acceleration peak (means: from 4.5 g to 5.2 g) and rate. Among the three shoes tested, the shoe with intermediate midsole foam provided the best compromise between viscosity and elasticity. The optimum balance remains to be found for the design of shoes regarding at once cushioning, durability and injury prevention. PMID:24576090

  5. Mechanisms of premature vascular aging in children with Hutchinson-Gilford progeria syndrome.

    PubMed

    Gerhard-Herman, Marie; Smoot, Leslie B; Wake, Nicole; Kieran, Mark W; Kleinman, Monica E; Miller, David T; Schwartzman, Armin; Giobbie-Hurder, Anita; Neuberg, Donna; Gordon, Leslie B

    2012-01-01

    Hutchinson-Gilford progeria syndrome is a rare, segmental premature aging syndrome of accelerated atherosclerosis and early death from myocardial infarction or stroke. This study sought to establish comprehensive characterization of the fatal vasculopathy in Hutchinson-Gilford progeria syndrome and its relevance to normal aging. We performed cardiovascular assessments at a single clinical site on the largest prospectively studied cohort to date. Carotid-femoral pulse wave velocity was dramatically elevated (mean: 13.00±3.83 m/s). Carotid duplex ultrasound echobrightness, assessed in predefined tissue sites as a measure of arterial wall density, was significantly greater than age- and sex-matched controls in the intima-media (P<0.02), near adventitia (P<0.003), and deep adventitia (P<0.01), as was internal carotid artery mean flow velocity (P<0.0001). Ankle-brachial indices were abnormal in 78% of patients. Effective disease treatments may be heralded by normalizing trends of these noninvasive cardiovascular measures. The data demonstrate that, along with peripheral vascular occlusive disease, accelerated vascular stiffening is an early and pervasive mechanism of vascular disease in Hutchinson-Gilford progeria syndrome. There is considerable overlap with cardiovascular changes of normal aging, which reinforces the view that defining mechanisms of cardiovascular disease in Hutchinson-Gilford progeria syndrome provides a unique opportunity to isolate a subset of factors influencing cardiovascular disease in the general aging population.

  6. The antioxidant mechanisms underlying the aged garlic extract- and S-allylcysteine-induced protection.

    PubMed

    Colín-González, Ana L; Santana, Ricardo A; Silva-Islas, Carlos A; Chánez-Cárdenas, Maria E; Santamaría, Abel; Maldonado, Perla D

    2012-01-01

    Aged garlic extract (AGE) is an odorless garlic preparation containing S-allylcysteine (SAC) as its most abundant compound. A large number of studies have demonstrated the antioxidant activity of AGE and SAC in both in vivo--in diverse experimental animal models associated to oxidative stress--and in vitro conditions--using several methods to scavenge reactive oxygen species or to induce oxidative damage. Derived from these experiments, the protective effects of AGE and SAC have been associated with the prevention or amelioration of oxidative stress. In this work, we reviewed different antioxidant mechanisms (scavenging of free radicals and prooxidant species, induction of antioxidant enzymes, activation of Nrf2 factor, inhibition of prooxidant enzymes, and chelating effects) involved in the protective actions of AGE and SAC, thereby emphasizing their potential use as therapeutic agents. In addition, we highlight the ability of SAC to activate Nrf2 factor--a master regulator of the cellular redox state. Here, we include original data showing the ability of SAC to activate Nrf2 factor in cerebral cortex. Therefore, we conclude that the therapeutic properties of these molecules comprise cellular and molecular mechanisms at different levels. PMID:22685624

  7. The Antioxidant Mechanisms Underlying the Aged Garlic Extract- and S-Allylcysteine-Induced Protection

    PubMed Central

    Colín-González, Ana L.; Santana, Ricardo A.; Silva-Islas, Carlos A.; Chánez-Cárdenas, Maria E.; Santamaría, Abel; Maldonado, Perla D.

    2012-01-01

    Aged garlic extract (AGE) is an odorless garlic preparation containing S-allylcysteine (SAC) as its most abundant compound. A large number of studies have demonstrated the antioxidant activity of AGE and SAC in both in vivo—in diverse experimental animal models associated to oxidative stress—and in vitro conditions—using several methods to scavenge reactive oxygen species or to induce oxidative damage. Derived from these experiments, the protective effects of AGE and SAC have been associated with the prevention or amelioration of oxidative stress. In this work, we reviewed different antioxidant mechanisms (scavenging of free radicals and prooxidant species, induction of antioxidant enzymes, activation of Nrf2 factor, inhibition of prooxidant enzymes, and chelating effects) involved in the protective actions of AGE and SAC, thereby emphasizing their potential use as therapeutic agents. In addition, we highlight the ability of SAC to activate Nrf2 factor—a master regulator of the cellular redox state. Here, we include original data showing the ability of SAC to activate Nrf2 factor in cerebral cortex. Therefore, we conclude that the therapeutic properties of these molecules comprise cellular and molecular mechanisms at different levels. PMID:22685624

  8. Mechanical properties evaluations of an age hardenable martensitic steel deformed by equal channel angular pressing.

    PubMed

    Nili-Ahmadabadi, M; Shirazi, H; Iranpour Mobarake, M; Poorganji, B; Hossein Nedjad, S; Furuhara, T

    2010-09-01

    Effect of severe plastic deformation by equal channel angular pressing on the mechanical properties of an age hardenable low carbon martensitic steel was investigated. Equal Channel angular pressing was carried out on the solution-annealed steel up to four passes at room temperature through the route Bc. Aging was carried out at 753 K for 2.4 ks. It was found that after four passes deformation, the microstructure is consist of fine grained high angle grain boundaries and lamellar dislocation cell block. The strength of steel is increased considerably while a increasing in elongation is revealed. PMID:21133170

  9. Dynamic mechanical and molecular weight measurements on polymer bonded explosives from thermally accelerated aging tests. I. Fluoropolymer binders

    SciTech Connect

    Hoffman, D.M.; Caley, L.E.

    1981-01-01

    The dynamic mechanical properties and molecular weight distribution of two polymer bonded explosives, LX-10-1 and PBX-9502, maintained at 23, 60, and 74/sup 0/C for 3 years were studied. LX-10-1 is 94.5% 1,3,5,7-tetranitro-1,3,5,7-tetraazacyclooctane explosive bonded together with 5.5% Viton A fluoropolymer. PBX-9502 is 95% triaminotrinitrobenzene explosive bonded with 5% Kel-F-800 fluoropolymer. There are two mechanical relaxations in the LX-10-1 in the military temperature range. The relaxation at -10/sup 0/C is associated with the glass transition temperature of the Viton A binder. A second weak relaxation occurs at about 30/sup 0/C in all LX-10-1 samples tested. This relaxation is probably associated with small amounts of crystallinity in the binder although this has not been demonstrated. There is a slight increase in modulus of the LX-10-1 with accelerated aging temperature. Changes in the dynamic mechanical properties of PBX-9502 are ascribed to crystallization of the chlorotrifluoroethylene component of the Kel-F-800 binder. The molecular weight of the Viton A binder decreased slight with increasing aging temperature. Using the kinetics of random scission the activation energy for polymer degradation in the presence of the explosive was 1.19 kcal/mole. The Arrhenius preexponential term and activation energy predict an expected use-life in excess of 60 years for LX-10-1. The Kel-F-800 in PBX-9502 is also extremely stable.

  10. Barriers to the Preclinical Development of Therapeutics that Target Aging Mechanisms

    PubMed Central

    Burd, Christin E.; Gill, Matthew S.; Niedernhofer, Laura J.; Robbins, Paul D.; Austad, Steven N.; Barzilai, Nir

    2016-01-01

    Through the progress of basic science research, fundamental mechanisms that contribute to age-related decline are being described with increasing depth and detail. Although these efforts have identified new drug targets and compounds that extend life span in model organisms, clinical trials of therapeutics that target aging processes remain scarce. Progress in aging research is hindered by barriers associated with the translation of basic science discoveries into the clinic. This report summarizes discussions held at a 2014 Geroscience Network retreat focused on identifying hurdles that currently impede the preclinical development of drugs targeting fundamental aging processes. From these discussions, it was evident that aging researchers have varied perceptions of the ideal preclinical pipeline. To forge a clear and cohesive path forward, several areas of controversy must first be resolved and new tools developed. Here, we focus on five key issues in preclinical drug development (drug discovery, lead compound development, translational preclinical biomarkers, funding, and integration between researchers and clinicians), expanding upon discussions held at the Geroscience Retreat and suggesting areas for further research. By bringing these findings to the attention of the aging research community, we hope to lay the foundation for a concerted preclinical drug development pipeline. PMID:27535964

  11. Mechanisms of ethanol-induced degeneration in the developing, mature, and aging cerebellum.

    PubMed

    Jaatinen, Pia; Rintala, Jyrki

    2008-01-01

    The adverse effects of acute and chronic ethanol exposure on cerebellar functions have been acknowledged for decades, in terms of impaired control of movement and balance. In addition to the motor impairment, cerebellar degeneration has recently been shown to contribute to distinct neuropsychological deficits in chronic alcoholics, as well as in children with prenatal ethanol exposure. The basic mechanisms underlying these ethanol-induced functional alterations and the related neuropathology in the cerebellum have mostly been clarified only recently. These mechanisms include: (i) excitotoxicity; (ii) dietary factors, especially thiamine depletion; (iii) glial abnormalities; (iv) changes in growth factors; (v) apoptotic mechanisms; (vi) oxidative stress; and (vii) compromised energy production. Although these mechanisms widely apply not only to the mature cerebellum, but also to the developing and the aging cerebella, the developing and the aged cerebellum have some special characteristics, which may make them even more vulnerable to ethanol-induced degeneration. These special instances will be discussed along with the general mechanisms of ethanol-induced cerebellar degeneration. PMID:18418667

  12. Forming patterns and mechanical properties of austenitic chromium-nickel steel due to strain aging

    NASA Astrophysics Data System (ADS)

    Kamyshanchenko, N. V.; Krasilnikov, V. V.; Nikulin, I. S.; Gal'tsev, A. V.; Belenko, V. A.; Gal'tseva, I. N.

    2016-02-01

    The work presents the results of studies of forming patterns and mechanical properties of martensite transformation, found in the chromium-nickel steels of 08X18H10T grade, subjected to pre-heat treatment followed by deformation aging. Internal energy state is determined by using acoustic emission. The observed patterns improve the mechanical parameters of steels quenched and plastically deformed at low temperature and then subjected to temper under load in the optimum temperature being associated with obtaining a more stable condition of the structure through the processes of relaxation of internal stresses, high dispersion and uniform distribution of carbides and intermetallic particles, increasing the density of dislocations as well as through other processes occurring during deformation aging martensite. Start your abstract here...

  13. Quality Saving Mechanisms of Mitochondria during Aging in a Fully Time-Dependent Computational Biophysical Model.

    PubMed

    Mellem, Daniel; Fischer, Frank; Jaspers, Sören; Wenck, Horst; Rübhausen, Michael

    2016-01-01

    Mitochondria are essential for the energy production of eukaryotic cells. During aging mitochondria run through various processes which change their quality in terms of activity, health and metabolic supply. In recent years, many of these processes such as fission and fusion of mitochondria, mitophagy, mitochondrial biogenesis and energy consumption have been subject of research. Based on numerous experimental insights, it was possible to qualify mitochondrial behaviour in computational simulations. Here, we present a new biophysical model based on the approach of Figge et al. in 2012. We introduce exponential decay and growth laws for each mitochondrial process to derive its time-dependent probability during the aging of cells. All mitochondrial processes of the original model are mathematically and biophysically redefined and additional processes are implemented: Mitochondrial fission and fusion is separated into a metabolic outer-membrane part and a protein-related inner-membrane part, a quality-dependent threshold for mitophagy and mitochondrial biogenesis is introduced and processes for activity-dependent internal oxidative stress as well as mitochondrial repair mechanisms are newly included. Our findings reveal a decrease of mitochondrial quality and a fragmentation of the mitochondrial network during aging. Additionally, the model discloses a quality increasing mechanism due to the interplay of the mitophagy and biogenesis cycle and the fission and fusion cycle of mitochondria. It is revealed that decreased mitochondrial repair can be a quality saving process in aged cells. Furthermore, the model finds strategies to sustain the quality of the mitochondrial network in cells with high production rates of reactive oxygen species due to large energy demands. Hence, the model adds new insights to biophysical mechanisms of mitochondrial aging and provides novel understandings of the interdependency of mitochondrial processes. PMID:26771181

  14. Quality Saving Mechanisms of Mitochondria during Aging in a Fully Time-Dependent Computational Biophysical Model

    PubMed Central

    Mellem, Daniel; Fischer, Frank; Jaspers, Sören; Wenck, Horst; Rübhausen, Michael

    2016-01-01

    Mitochondria are essential for the energy production of eukaryotic cells. During aging mitochondria run through various processes which change their quality in terms of activity, health and metabolic supply. In recent years, many of these processes such as fission and fusion of mitochondria, mitophagy, mitochondrial biogenesis and energy consumption have been subject of research. Based on numerous experimental insights, it was possible to qualify mitochondrial behaviour in computational simulations. Here, we present a new biophysical model based on the approach of Figge et al. in 2012. We introduce exponential decay and growth laws for each mitochondrial process to derive its time-dependent probability during the aging of cells. All mitochondrial processes of the original model are mathematically and biophysically redefined and additional processes are implemented: Mitochondrial fission and fusion is separated into a metabolic outer-membrane part and a protein-related inner-membrane part, a quality-dependent threshold for mitophagy and mitochondrial biogenesis is introduced and processes for activity-dependent internal oxidative stress as well as mitochondrial repair mechanisms are newly included. Our findings reveal a decrease of mitochondrial quality and a fragmentation of the mitochondrial network during aging. Additionally, the model discloses a quality increasing mechanism due to the interplay of the mitophagy and biogenesis cycle and the fission and fusion cycle of mitochondria. It is revealed that decreased mitochondrial repair can be a quality saving process in aged cells. Furthermore, the model finds strategies to sustain the quality of the mitochondrial network in cells with high production rates of reactive oxygen species due to large energy demands. Hence, the model adds new insights to biophysical mechanisms of mitochondrial aging and provides novel understandings of the interdependency of mitochondrial processes. PMID:26771181

  15. Quality Saving Mechanisms of Mitochondria during Aging in a Fully Time-Dependent Computational Biophysical Model.

    PubMed

    Mellem, Daniel; Fischer, Frank; Jaspers, Sören; Wenck, Horst; Rübhausen, Michael

    2016-01-01

    Mitochondria are essential for the energy production of eukaryotic cells. During aging mitochondria run through various processes which change their quality in terms of activity, health and metabolic supply. In recent years, many of these processes such as fission and fusion of mitochondria, mitophagy, mitochondrial biogenesis and energy consumption have been subject of research. Based on numerous experimental insights, it was possible to qualify mitochondrial behaviour in computational simulations. Here, we present a new biophysical model based on the approach of Figge et al. in 2012. We introduce exponential decay and growth laws for each mitochondrial process to derive its time-dependent probability during the aging of cells. All mitochondrial processes of the original model are mathematically and biophysically redefined and additional processes are implemented: Mitochondrial fission and fusion is separated into a metabolic outer-membrane part and a protein-related inner-membrane part, a quality-dependent threshold for mitophagy and mitochondrial biogenesis is introduced and processes for activity-dependent internal oxidative stress as well as mitochondrial repair mechanisms are newly included. Our findings reveal a decrease of mitochondrial quality and a fragmentation of the mitochondrial network during aging. Additionally, the model discloses a quality increasing mechanism due to the interplay of the mitophagy and biogenesis cycle and the fission and fusion cycle of mitochondria. It is revealed that decreased mitochondrial repair can be a quality saving process in aged cells. Furthermore, the model finds strategies to sustain the quality of the mitochondrial network in cells with high production rates of reactive oxygen species due to large energy demands. Hence, the model adds new insights to biophysical mechanisms of mitochondrial aging and provides novel understandings of the interdependency of mitochondrial processes.

  16. Aging-related changes in respiratory system mechanics and morphometry in mice.

    PubMed

    Elliott, Jonathan E; Mantilla, Carlos B; Pabelick, Christina M; Roden, Anja C; Sieck, Gary C

    2016-07-01

    Previous work investigating respiratory system mechanics in mice has reported an aging-related increase in compliance and mean linear intercept (Lm). However, these changes were assessed using only a young (2-mo-old) and old (20- and 26-mo-old) group yet were interpreted to reflect a linear evolution across the life span. Therefore, to investigate respiratory system mechanics and lung morphometry across a more complete spectrum of ages, we utilized 2 (100% survival, n = 6)-, 6 (100% survival, n = 12)-, 18 (90% survival, n = 12)-, 24 (75% survival, n = 12)-, and 30 (25% survival, n = 12)-mo-old C57BL/6 mice. We found a nonlinear aging-related decrease in respiratory system resistance and increase in dynamic compliance and hysteresis between 2- and 24-mo-old mice. However, in 30-mo-old mice, respiratory system resistance increased, and dynamic compliance and hysteresis decreased relative to 24-mo-old mice. Respiratory system impedance spectra were measured between 1-20.5 Hz at positive end-expiratory pressures (PEEP) of 1, 3, 5, and 7 cmH2O. Respiratory system resistance and reactance at each level of PEEP were increased and decreased, respectively, only in 2-mo-old animals. No differences in the respiratory system impedance spectra were observed in 6-, 18-, 24-, and 30-mo-old mice. Additionally, lungs were fixed following tracheal instillation of 4% paraformaldehyde at 25 cmH2O and processed for Lm and airway collagen deposition. There was an aging-related increase in Lm consistent with emphysematous-like changes and no evidence of increased airway collagen deposition. Accordingly, we demonstrate nonlinear aging-related changes in lung mechanics and morphometry in C57BL/6 mice.

  17. In situ activity recovery of aging biofilm in biological aerated filter: Surfactants treatment and mechanisms study.

    PubMed

    Yu, Qisheng; Huang, Hui; Ren, Hongqiang; Ding, Lili; Geng, Jinju

    2016-11-01

    In situ activity recovery of aging biofilm in the biological aerated filter (BAF) is an important but underappreciated problem. Lab-scaled BAFs were established in this study and three kinds of surfactants containing sodium dodecyl sulfate (SDS), sodium dodecyl benzene sulfonate (SDBS) and rhamnolipid were employed. Multiple indicators including effluent qualities, dissolved organic matters, biofilm physiology and morphology characteristics were investigated to explore the mechanisms. Results showed that removal rates of effluent COD in test groups significantly recovered to the level before aging. Compared with the control, effluent in SDBS and rhamnolipid-treated groups obtained more protein-like and humic-like substances, respectively. Furthermore, great live cell ratio, smooth surface and low adhesion force of biofilm were observed after rhamnolipid treatment, which was in consistent with good effluent qualities in the same group. This is the first report of applying rhamnolipid for in situ activity recovery of aging biofilm in bioreactors. PMID:27513646

  18. Influence of maturation and aging on mechanical and biochemical properties of connective tissue in rats.

    PubMed

    Vogel, H G

    1980-01-01

    The influence of maturation and age on the physical and chemical properties of various organs of connective tissue has been studied in rats at ages of 4 weeks, 8 weeks, 4 monhs, 1 year and 2 years. The changes between young (4 weeks old) and adult (4 months to 1 year old) animals were considered as the effects of maturation, whereas the changes between adult and senescent (2 years old) rats were regarded as the effects of aging. Ultimate values, such as ultimate load, tensile strength and breaking strength, or ultimate modulus of elasticity, showed a sharp rise during maturation and a smaller but significant decrease during aging in all organs, such as skin strips, tail tendons, shaft bones, epiphyseal cartilage and aorta rings. Ultimate strain showed a similar pattern, but the maximum occurred earlier. These changes were parallel with the content of insoluble collagen. Other chemical parameters such as soluble collagen or glycosaminoglycans, showed a continuous decrease during the life span, whereas elastin rose continuously. More detailed analysis of mechanical properties in rat skin gave insight into the viscoelastic behaviour of skin. In creep experiments time until break under constant load rose continuously during the life span, whereas ultimate extension rate showed a sharp fall during maturation and a slow decrease during senescence. Stress at low extension degree and moduli of elasticity at low extension degree were decreased by maturation and increased by senescence, exactly the opposite of the changes at high extension degrees. The so-called step phenomenon was increased due to maturation and decreased due to aging. Relaxation and mechanical recovery were changed in the same direction by maturation and aging. Relative viscoelastic parameters, such as the hysteresis phenomenon and relative decrease of stress under cyclic strain, were barely influenced by the aging process. Changes of most of the mechanical parameters at high extension degrees during

  19. The effect of aging and surface modification on the mechanical properties of dense aluminum oxide.

    PubMed

    Cook, S D; Weinberg, L A

    1984-01-01

    The effect of in vivo aging and surface texturing on the mechanical properties of dense aluminum oxide were studied. The modulus of rupture and Weibull modulus were determined in air and Ringer's solution using a 3-point bend test. The results showed that the in vivo environment sealed off microcracks either chemically or by tissue ingrowth which strengthened the alumina. The surface modification, however, tended to create more microcracks and stress concentrations at the surface indentations which tended to weaken the alumina.

  20. The effect of aging on crack-growth resistance and toughening mechanisms in human dentin.

    PubMed

    Koester, Kurt J; Ager, Joel W; Ritchie, Robert O

    2008-04-01

    Crack-growth experiments in human dentin have been performed in situ in an environmental scanning electron microscope to measure, for the first time, the crack-growth resistance curve (R-curve) for clinically relevant (<250 microm) crack extensions and to simultaneously identify the salient toughening mechanisms. "Young" dentin from donors 19-30 years in age and "aged" dentin from donors 40-70 years in age were evaluated. The "young" group had 0-4% of its tubules filled with apatite; the "aged" group was subdivided into "opaque" with 12-32% filled tubules and "transparent" with 65-100% filled tubules. Although crack-initiation toughnesses were similar, the crack-growth resistance of "young" dentin was higher by about 40% compared to "aged" dentin. Mechanistically, this behavior is interpreted in terms of three phenomena: (i) gross crack deflection of the growing crack, (ii) microcracks which initiated at unfilled tubules in the high stress region in the vicinity of a propagating crack (no microcracks formed at filled tubules), and (iii) crack propagation which followed a local trajectory through unfilled tubules and deflected around filled tubules. The higher toughness of the "young" dentin was related to enhanced microcracking (at unfilled tubules) ahead of the growing crack, which (i) shields the crack by activating multiple crack tips and by reducing the local stress intensity through crack deflection and (ii) leads to the formation of crack bridges from "uncracked ligaments" due to the incomplete coalescence of these microcracks with the main crack tip. With age, the role of these toughening mechanisms was diminished primarily to the lower fraction of unfilled, and hence microcracked, tubules.

  1. Temperature dependent ageing mechanisms in Lithium-ion batteries - A Post-Mortem study

    NASA Astrophysics Data System (ADS)

    Waldmann, Thomas; Wilka, Marcel; Kasper, Michael; Fleischhammer, Meike; Wohlfahrt-Mehrens, Margret

    2014-09-01

    The effects of temperatures in the range of -20 °C to 70 °C on the ageing behaviour of cycled Lithium-ion batteries are investigated quantitatively by electrochemical methods and Post-Mortem analysis. Commercial 18650-type high-power cells with a LixNi1/3Mn1/3Co1/3O2/LiyMn2O4 blend cathode and graphite/carbon anode were used as test system. The cells were cycled at a rate of 1 C until the discharge capacity falls below 80% of the initial capacity. Interestingly, an Arrhenius plot indicates two different ageing mechanisms for the ranges of -20 °C to 25 °C and 25 °C to 70 °C. Below 25 °C, the ageing rates increase with decreasing temperature, while above 25 °C ageing is accelerated with increasing temperature. The aged 18650 cells are inspected via scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), inductively coupled plasma (ICP), measurements of electrode thickness and X-ray diffraction (XRD) after disassembly to learn more about the chemical reasons of the degradation. The effect of different temperatures on the electrode polarizations are evaluated by assembling electrodes in pouch cells with reference electrode as a model system. We find that the dominating ageing mechanism for T < 25 °C is Lithium plating, while for T > 25 °C the cathodes show degeneration and the anodes will be increasingly covered by SEI layers.

  2. Directional variations of mechanical parameters in rat skin depending on maturation and age.

    PubMed

    Vogel, H G

    1981-06-01

    Mechanical properties of rat back skin at low loads and at failure were studied in 2 directions, e.g., perpendicular and longitudinal to body axis beginning with early maturation (from 1 week onwards) until senescence (at 24 mo). Anisotropic behavior, known for human skin, has also been found in rats. Surprisingly, the changes due to maturation and aging were not the same for one area of skin regardless of the direction. Ultimate extension was more influenced by the aging process in samples perpendicular to the body axis than in those parallel to body axis. Elongation at zero load, that means load not measurable under the described conditions, was higher in the longitudinal samples than in the perpendicular ones in young and very old animals, whereas this difference was absent in mature animals. In contrast, ultimate load, tensile strength and modulus of elasticity were higher in perpendicular samples than in samples longitudinal to the body axis for young and very old, but not for mature animals. Elongation at low loads or low stresses shows a different pattern than at medium loads or medium stresses when both directions are compared. Apparently, elements contributing to the mechanical properties in the various directions are differently influenced by the maturation and aging processes. Moreover, the elements contributing to the changes at low loads react differently to the aging process from those responsible for the effects at medium and high loads.

  3. Mechanical Properties of Anisotropic Conductive Adhesive Film Under Hygrothermal Aging and Thermal Cycling

    NASA Astrophysics Data System (ADS)

    Gao, Li-Lan; Chen, Xu; Gao, Hong

    2012-07-01

    Mechanical properties of anisotropic conductive adhesive film (ACF) were investigated experimentally under various environmental conditions. The temperature sweep test was conducted to investigate the effects of temperature on dynamical mechanical properties of the ACF. The ACF exhibited transitions to the glass state, viscoelastic state, and rubber state with increasing temperature, and its glass-transition temperature ( T g) was determined to be 149°C. The creep-recovery behaviors of the ACF were investigated, and it was found that the initial strains, instantaneous strains, and creep or recovery rates increased with increasing temperature. No obvious creep phenomenon was observed at low temperatures (≤0°C). The creep strain and creep rates at any time decreased with increasing hygrothermal aging time. The uniaxial tensile behaviors of the ACF were also investigated under hygrothermal aging and thermal cycling. The results show that the Young's modulus and tensile strength of the ACF decrease with increasing hygrothermal aging time; however, they increase at first and then decrease with increasing thermal cycling time. T g decreases slightly for the ACF after hygrothermal aging; however, it increases after thermal cycling.

  4. Molecular and Cellular Mechanisms of Muscle Aging and Sarcopenia and Effects of Electrical Stimulation in Seniors

    PubMed Central

    Barberi, Laura; Scicchitano, Bianca Maria

    2015-01-01

    The prolongation of skeletal muscle strength in aging and neuromuscular disease has been the objective of numerous studies employing a variety of approaches. It is generally accepted that cumulative failure to repair damage related to an overall decrease in anabolic processes is a primary cause of functional impairment in muscle. The functional performance of skeletal muscle tissues declines during post- natal life and it is compromised in different diseases, due to an alteration in muscle fiber composition and an overall decrease in muscle integrity as fibrotic invasions replace functional contractile tissue. Characteristics of skeletal muscle aging and diseases include a conspicuous reduction in myofiber plasticity (due to the progressive loss of muscle mass and in particular of the most powerful fast fibers), alteration in muscle-specific transcriptional mechanisms, and muscle atrophy. An early decrease in protein synthetic rates is followed by a later increase in protein degradation, to affect biochemical, physiological, and morphological parameters of muscle fibers during the aging process. Alterations in regenerative pathways also compromise the functionality of muscle tissues. In this review we will give an overview of the work on molecular and cellular mechanisms of aging and sarcopenia and the effects of electrical stimulation in seniors.. PMID:26913161

  5. Aging and loading rate effects on the mechanical behavior of equine bone

    NASA Astrophysics Data System (ADS)

    Kulin, Robb M.; Jiang, Fengchun; Vecchio, Kenneth S.

    2008-06-01

    Whether due to a sporting accident, high-speed impact, fall, or other catastrophic event, the majority of clinical bone fractures occur under dynamic loading conditions. However, although extensive research has been performed on the quasi-static fracture and mechanical behavior of bone to date, few high-quality studies on the fracture behavior of bone at high strain rates have been performed. Therefore, many questions remain regarding the material behavior, including not only the loading-rate-dependent response of bone, but also how this response varies with age. In this study, tests were performed on equine femoral bone taken post-mortem from donors 6 months to 28 years of age. Quasi-static and dynamic tests were performed to determine the fracture toughness and compressive mechanical behavior as a function of age at varying loading rates. Fracture paths were then analyzed using scanning confocal and scanning-electron microscopy techniques to assess the role of various microstructural features on toughening mechanisms.

  6. Mechanism of Silicon Electrode Aging upon Cycling in Full Lithium-Ion Batteries.

    PubMed

    Delpuech, Nathalie; Dupre, Nicolas; Moreau, Philippe; Bridel, Jean-Sebastian; Gaubicher, Joel; Lestriez, Bernard; Guyomard, Dominique

    2016-04-21

    Understanding the aging mechanism of silicon-based negative electrodes for lithium-ion batteries upon cycling is essential to solve the problem of low coulombic efficiency and capacity fading and further to implement this new high-capacity material in commercial cells. Nevertheless, such studies have so far focused on half cells in which silicon is cycled versus an infinite reservoir of lithium. In the present work, the aging mechanism of silicon-based electrodes is studied upon cycling in a full Li-ion cell configuration with LiCoO2 as the positive electrode. Postmortem analyses of both electrodes clearly indicate that neither one of them contains lithium and that no discernible degradation results from the cycling. The aging mechanism can be explained by the reduction of solvent molecules. Electrons extracted from the positive electrode are responsible for an internal imbalance in the cell, which results in progressive slippage of the electrodes and reduces the compositional range of cyclable lithium ions for both electrodes. PMID:26915951

  7. Lamb Wave Stiffness Characterization of Composites Undergoing Thermal-Mechanical Aging

    NASA Technical Reports Server (NTRS)

    Seale, Michael D.; Madaras, Eric I.

    2004-01-01

    The introduction of new, advanced composite materials into aviation systems requires a thorough understanding of the long term effects of combined thermal and mechanical loading upon those materials. Analytical methods investigating the effects of intense thermal heating combined with mechanical loading have been investigated. The damage mechanisms and fatigue lives were dependent on test parameters as well as stress levels. Castelli, et al. identified matrix dominated failure modes for out-of-phase cycling and fiber dominated damage modes for in-phase cycling. In recent years, ultrasonic methods have been developed that can measure the mechanical stiffness of composites. To help evaluate the effect of aging, a suitably designed Lamb wave measurement system is being used to obtain bending and out-of-plane stiffness coefficients of composite laminates undergoing thermal-mechanical loading. The system works by exciting an antisymmetric Lamb wave and calculating the velocity at each frequency from the known transducer separation and the measured time-of-flight. The same peak in the waveforms received at various distances is used to measure the time difference between the signals. The velocity measurements are accurate and repeatable to within 1% resulting in reconstructed stiffness values repeatable to within 4%. Given the material density and plate thickness, the bending and out-of-plane shear stiffnesses are calculated from a reconstruction of the dispersion curve. A mechanical scanner is used to move the sensors over the surface to map the time-of-flight, velocity, or stiffnesses of the entire specimen. Access to only one side of the material is required and no immersion or couplants are required because the sensors are dry coupled to the surface of the plate. In this study, the elastic stiffnesses D(sub 11), D(sub 22), A(sub 44), and A(sub 55) as well as time-of-flight measurements for composite samples that have undergone combined thermal and mechanical aging for

  8. Glycation-altered proteolysis as a pathobiologic mechanism that links dietary glycemic index, aging, and age-related disease in non diabetics

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Epidemiologic studies indicate that the risks for major age-related debilities including coronary heart disease, diabetes, and age-related macular degeneration (AMD) are diminished in people who consume lower glycemic index (GI) diets, but lack of a unifying physiobiochemical mechanism that explains...

  9. Patient (customer) expectations in hospitals.

    PubMed

    Bostan, Sedat; Acuner, Taner; Yilmaz, Gökhan

    2007-06-01

    The expectations of patient are one of the determining factors of healthcare service. The purpose of this study is to measure the Patients' Expectations, based on Patient's Rights. This study was done with Likert-Survey in Trabzon population. The analyses showed that the level of the expectations of the patient was high on the factor of receiving information and at an acceptable level on the other factors. Statistical meaningfulness was determined between age, sex, education, health insurance, and the income of the family and the expectations of the patients (p<0.05). According to this study, the current legal regulations have higher standards than the expectations of the patients. The reason that the satisfaction of the patients high level is interpreted due to the fact that the level of the expectation is low. It is suggested that the educational and public awareness studies on the patients' rights must be done in order to increase the expectations of the patients. PMID:17028043

  10. Role of mitochondrial dysfunction and altered autophagy in cardiovascular aging and disease: from mechanisms to therapeutics

    PubMed Central

    Marzetti, Emanuele; Csiszar, Anna; Dutta, Debapriya; Balagopal, Gauthami; Calvani, Riccardo

    2013-01-01

    Advanced age is associated with a disproportionate prevalence of cardiovascular disease (CVD). Intrinsic alterations in the heart and the vasculature occurring over the life course render the cardiovascular system more vulnerable to various stressors in late life, ultimately favoring the development of CVD. Several lines of evidence indicate mitochondrial dysfunction as a major contributor to cardiovascular senescence. Besides being less bioenergetically efficient, damaged mitochondria also produce increased amounts of reactive oxygen species, with detrimental structural and functional consequences for the cardiovascular system. The age-related accumulation of dysfunctional mitochondrial likely results from the combination of impaired clearance of damaged organelles by autophagy and inadequate replenishment of the cellular mitochondrial pool by mitochondriogenesis. In this review, we summarize the current knowledge about relevant mechanisms and consequences of age-related mitochondrial decay and alterations in mitochondrial quality control in the cardiovascular system. The involvement of mitochondrial dysfunction in the pathogenesis of cardiovascular conditions especially prevalent in late life and the emerging connections with neurodegeneration are also illustrated. Special emphasis is placed on recent discoveries on the role played by alterations in mitochondrial dynamics (fusion and fission), mitophagy, and their interconnections in the context of age-related CVD and endothelial dysfunction. Finally, we discuss pharmacological interventions targeting mitochondrial dysfunction to delay cardiovascular aging and manage CVD. PMID:23748424

  11. Role of mitochondrial dysfunction and altered autophagy in cardiovascular aging and disease: from mechanisms to therapeutics.

    PubMed

    Marzetti, Emanuele; Csiszar, Anna; Dutta, Debapriya; Balagopal, Gauthami; Calvani, Riccardo; Leeuwenburgh, Christiaan

    2013-08-15

    Advanced age is associated with a disproportionate prevalence of cardiovascular disease (CVD). Intrinsic alterations in the heart and the vasculature occurring over the life course render the cardiovascular system more vulnerable to various stressors in late life, ultimately favoring the development of CVD. Several lines of evidence indicate mitochondrial dysfunction as a major contributor to cardiovascular senescence. Besides being less bioenergetically efficient, damaged mitochondria also produce increased amounts of reactive oxygen species, with detrimental structural and functional consequences for the cardiovascular system. The age-related accumulation of dysfunctional mitochondrial likely results from the combination of impaired clearance of damaged organelles by autophagy and inadequate replenishment of the cellular mitochondrial pool by mitochondriogenesis. In this review, we summarize the current knowledge about relevant mechanisms and consequences of age-related mitochondrial decay and alterations in mitochondrial quality control in the cardiovascular system. The involvement of mitochondrial dysfunction in the pathogenesis of cardiovascular conditions especially prevalent in late life and the emerging connections with neurodegeneration are also illustrated. Special emphasis is placed on recent discoveries on the role played by alterations in mitochondrial dynamics (fusion and fission), mitophagy, and their interconnections in the context of age-related CVD and endothelial dysfunction. Finally, we discuss pharmacological interventions targeting mitochondrial dysfunction to delay cardiovascular aging and manage CVD.

  12. Precipitation and mechanical properties of Nb-modified ferritic stainless steel during isothermal aging

    SciTech Connect

    Yan Haitao Bi Hongyun; Li Xin; Xu Zhou

    2009-03-15

    The influence of isothermal aging on precipitation behavior and mechanical properties of Nb-modified ferritic stainless steel was investigated using Thermo-calc software, scanning electron microscopy and transmission electron microscopy. It was observed that TiN, NbC and Fe{sub 2}Nb formed in the investigated steel and the experimental results agreed well with the results calculated by Thermo-calc software. During isothermal aging at 800 deg. C, the coarsening rate of Fe{sub 2}Nb is greater than that of NbC, and the calculated average sizes of NbC and Fe{sub 2}Nb of the aged specimen agreed with the experimental results. In addition, the tensile strength and micro-hardness of the ferritic stainless steel increased with increased aging time from 24 h to 48 h. But aging at 800 deg. C for 96 h caused the coarsening of the precipitation, which led to a decrease of tensile strength and micro-hardness.

  13. Polyphenol Stilbenes: Molecular Mechanisms of Defence against Oxidative Stress and Aging-Related Diseases

    PubMed Central

    Reinisalo, Mika; Kårlund, Anna; Koskela, Ali; Kaarniranta, Kai; Karjalainen, Reijo O.

    2015-01-01

    Numerous studies have highlighted the key roles of oxidative stress and inflammation in aging-related diseases such as obesity, type 2 diabetes, age-related macular degeneration (AMD), and Alzheimer's disease (AD). In aging cells, the natural antioxidant capacity decreases and the overall efficiency of reparative systems against cell damage becomes impaired. There is convincing data that stilbene compounds, a diverse group of natural defence phenolics, abundant in grapes, berries, and conifer bark waste, may confer a protective effect against aging-related diseases. This review highlights recent data helping to clarify the molecular mechanisms involved in the stilbene-mediated protection against oxidative stress. The impact of stilbenes on the nuclear factor-erythroid-2-related factor-2 (Nrf2) mediated cellular defence against oxidative stress as well as the potential roles of SQSTM1/p62 protein in Nrf2/Keap1 signaling and autophagy will be summarized. The therapeutic potential of stilbene compounds against the most common aging-related diseases is discussed. PMID:26180583

  14. Age-related changes in the cellular, mechanical, and contractile properties of rat tail tendons.

    PubMed

    Lavagnino, Michael; Gardner, Keri; Arnoczky, Steven P

    2013-01-01

    Tendon laxity following injury, cyclic creep, or repair has been shown to alter the normal homeostasis of tendon cells, which can lead to degenerative changes in the extracellular matrix. While tendon cells have been shown to have an inherent contractile mechanism that gives them some ability to retighten lax tendons and reestablish a homeostatic cellular environment, the effect of age on this process is unknown. To determine the effect of aging on cell number, cell shape, and tensile modulus on tendons as well as the rate of cell-mediated contraction of lax tendons, tail tendon fascicles from 1-, 3-, and 12-month-old rats were analyzed. Aging results in a decrease (p < 0.001) in cell number per mm(2): 1 m (981 ± 119), 3 m (570 ± 108), and 12 m (453 ± 23), a more flattened (p < 0.001) cell nuclei shape and a higher (p < 0.001) tensile modulus (MPa) of the tendons: 1 m (291 ± 2), 3 m (527 ± 38), and 12 m (640 ± 102). Both the extent and rate of contraction over 7 days decreased with age (p = 0.007). This decrease in contraction rate with age correlates to the observed changes seen in aging tendons [increased modulus (r(2) = 0.95), decreased cell number (r(2) = 0.89)]. The ability of tendons to regain normal tension following injury or exercise-induced laxity is a key factor in the recovery of tendon function. The decreased contraction rate as a function of age observed in the current study may limit the ability of tendon cells to retighten lax tendons in older individuals. This, in turn, may place these structures at further risk for injury or altered function.

  15. Aging mechanisms for steel components of high-level waste storage tanks

    SciTech Connect

    Weeks, J.; Bandyopadhyay, K.; Bush, S.; Kassir, M.; Mather, B.; Shewmon, P.; Streicher, M.; Thompson, B.; van Rooyen, D.

    1995-05-01

    High level storage tanks in service at the present time were fabricated from either carbon steel or low-carbon stainless steel, in each case surrounded by a concrete vault. A variety of potential degradation mechanisms may affect these steel tanks, including corrosion, stress-corrosion cracking, fatigue, radiation, erosion, and hydrogen embrittlement. Historically, some of the non-stress-relieved carbon steel tanks have leaked; in the only failure analysis performed to date, stress corrosion cracking in the heat-affected zone (HAZ) of the weld was identified as the cause. Potentially significant aging mechanisms include general corrosion, pitting and/or crevice corrosion stress-corrosion cracking, microbiologically-induced corrosion, concentration cell attack, and corrosion of external tank surfaces by in-leakage of ground water. Aging mechanisms which are deemed non-significant include thermal and radiation embrittlement, creep and stress relaxation, fatigue, erosion and erosion/corrosion wear, and hydrogen embrittlement. Justification for the potential significance or non-significance for each mechanism is provided, based on the current understanding of these processes and the environments to which the tanks are exposed.

  16. Restricting the ageing degradation of the mechanical properties of gamma irradiated UHMWPE using MWCNTs.

    PubMed

    Rama Sreekanth, P S; Kanagaraj, S

    2013-05-01

    Property degradation of the medical grade polymers after gamma irradiation is the primary concern that limits longevity of them. Though the conventional antioxidant material helps to reduce the degradation but it limits the degree of crosslinking of the polymer. The objective of the present work is to study the influence of multi walled carbon nanotubes (MWCNTs) on restricting the degradation of mechanical properties of medical grade ultra high molecular weight polyethylene (UHMWPE) after its irradiation. UHMWPE was reinforced by chemically treated MWCNTs at different concentrations such as 0.5, 1.0, 1.5, and 2.0 wt%. The test samples were then subjected to Co⁶⁰ gamma irradiation with an integral dose of 25, 50, 75 and 100 kGy in air. The mechanical properties of irradiated samples were evaluated within 10 days, 60 and 120 days after irradiation. It was observed that the mechanical properties of virgin UHMWPE and nanocomposites were enhanced immediately after irradiation but they were found to be reduced at later stages. It was also observed that the presence of MWCNTs limited the ageing degradation of the mechanical properties of UHMWPE. Raman spectroscopic and TEM studies confirmed the formation of irradiation induced defects on the MWCNTs. Electron spin resonance studies showed that the relative radical intensity of virgin UHWMPE was reduced significantly with an increase of MWCNTs concentration confirming the radical scavenging ability of them. It is concluded that MWCNTs restricted the ageing degradation of irradiated UHMWPE.

  17. Neural mechanisms mediating positive and negative treatment expectations in visceral pain: a functional magnetic resonance imaging study on placebo and nocebo effects in healthy volunteers.

    PubMed

    Schmid, Julia; Theysohn, Nina; Gaß, Florian; Benson, Sven; Gramsch, Carolin; Forsting, Michael; Gizewski, Elke R; Elsenbruch, Sigrid

    2013-11-01

    To elucidate placebo and nocebo effects in visceral pain, we conducted a functional magnetic resonance imaging (fMRI) study to analyze effects of positive and negative treatment expectations in a rectal pain model. In 36 healthy volunteers, painful rectal distensions were delivered after intravenous application of an inert substance combined with either positive instructions of pain relief (placebo group) or negative instructions of pain increase (nocebo group), each compared to neutral instructions. Neural activation during cued-pain anticipation and pain was analyzed along with expected and perceived pain intensity. Expected and perceived pain intensity were significantly increased in the nocebo group and significantly decreased in the placebo group. In the placebo group, positive expectations significantly reduced activation of the somatosensory cortex during anticipation and of the insula, somatosensory cortex, and amygdala during pain delivery when compared to neutral expectations. Within the nocebo group, negative expectations led to significantly increased insula activation during painful stimulation. Direct group contrasts during expectation modulation revealed significantly increased distension-induced activation within the somatosensory cortex in the nocebo group. In conclusion, the experience and neural processing of visceral pain can be increased or decreased by drug-specific expectations. This first brain imaging study on nocebo effects in visceral pain has implications for the pathophysiology and treatment of patients with chronic abdominal complaints such as irritable bowel syndrome.

  18. Age-related changes in mechanical properties of the Achilles tendon.

    PubMed

    Waugh, C M; Blazevich, A J; Fath, F; Korff, T

    2012-02-01

    The stiffness of a tendon, which influences muscular force transfer to the skeleton and increases during childhood, is dependent on its material properties and dimensions, both of which are influenced by chronic loading. The aims of this study were to: (i) determine the independent contributions of body mass, force production capabilities and tendon dimensions to tendon stiffness during childhood; and (ii) descriptively document age-related changes in tendon mechanical properties and dimensions. Achilles tendon mechanical and material properties were determined in 52 children (5-12 years) and 19 adults. Tendon stiffness and Young's modulus (YM) were calculated as the slopes of the force-elongation and stress-strain curves, respectively. Relationships between stiffness vs. age, mass and force, and between YM vs. age, mass and stress were determined by means of polynomial fits and multiple regression analyses. Mass was found to be the best predictor of stiffness, whilst stress was best related to YM (< 75 and 51% explained variance, respectively). Combined, mass and force accounted for up to 78% of stiffness variation. Up to 61% of YM variability could be explained using a combination of mass, stress and age. These results demonstrate that age-related increases in tendon stiffness are largely attributable to increased tendon loading from weight-bearing tasks and increased plantarflexor force production, as well as tendon growth. Moreover, our results suggest that chronic increases in tendon loading during childhood result in microstructural changes which increase the tendon's YM. Regarding the second aim, peak stress increased from childhood to adulthood due to greater increases in strength than tendon cross-sectional area. Peak strain remained constant as a result of parallel increases in tendon length and peak elongation. The differences in Achilles tendon properties found between adults and children are likely to influence force production, and ultimately movement

  19. Genetic Architecture of Context Processing in Late Middle Age: More Than One Underlying Mechanism

    PubMed Central

    Kremen, William S.; Panizzon, Matthew S.; Xian, Hong; Barch, Deanna M.; Franz, Carol E.; Grant, Michael D.; Toomey, Rosemary; Lyons, Michael J.

    2011-01-01

    Studies comparing young and older adults suggest a deficit in processing context information as a key mechanism underlying cognitive aging. However, the genetic architecture of context processing has not been examined. Consistent with previous results, we found evidence of functionally dissociable components of context processing accuracy in 1127 late middle-aged twins ages 51–60. One component emphasizes use of context cues to prepare responses (proactive cognitive control); the other emphasizes adjustment of responses after probes are presented (reactive control). Approximately one-quarter of the variance in each component was accounted for by genes. Multivariate twin analysis indicated that genetic factors underlying two important components of context processing were independent of one another, thus implicating more than one underlying mechanism. Slower reaction time (RT) on non-context processing trials was positively correlated with errors on the strongly proactive control component on which young adults outperform older adults, but RT was negatively correlated with errors on the strongly reactive control component on which older adults perform better. Although this RT measure was uncorrelated with chronological age in our age-homogeneous sample, slower RT was associated with performance patterns that were more like older adults. However, this did not generalize to other processing speed measures. Genetic correlations, which reflect shared genetic variance, paralleled the phenotypic correlations. There was also a positive genetic correlation between general cognitive ability and accuracy on the proactive control component, but there were still mostly distinct genetic influences underlying these measures. In contrast, the reactive control component was unrelated to general cognitive ability. PMID:21875218

  20. Quantitative Analysis of Mechanisms That Govern Red Blood Cell Age Structure and Dynamics during Anaemia

    PubMed Central

    Savill, Nicholas J.; Chadwick, William; Reece, Sarah E.

    2009-01-01

    Mathematical modelling has proven an important tool in elucidating and quantifying mechanisms that govern the age structure and population dynamics of red blood cells (RBCs). Here we synthesise ideas from previous experimental data and the mathematical modelling literature with new data in order to test hypotheses and generate new predictions about these mechanisms. The result is a set of competing hypotheses about three intrinsic mechanisms: the feedback from circulating RBC concentration to production rate of immature RBCs (reticulocytes) in bone marrow, the release of reticulocytes from bone marrow into the circulation, and their subsequent ageing and clearance. In addition we examine two mechanisms specific to our experimental system: the effect of phenylhydrazine (PHZ) and blood sampling on RBC dynamics. We performed a set of experiments to quantify the dynamics of reticulocyte proportion, RBC concentration, and erythropoietin concentration in PHZ-induced anaemic mice. By quantifying experimental error we are able to fit and assess each hypothesis against our data and recover parameter estimates using Markov chain Monte Carlo based Bayesian inference. We find that, under normal conditions, about 3% of reticulocytes are released early from bone marrow and upon maturation all cells are released immediately. In the circulation, RBCs undergo random clearance but have a maximum lifespan of about 50 days. Under anaemic conditions reticulocyte production rate is linearly correlated with the difference between normal and anaemic RBC concentrations, and their release rate is exponentially correlated with the same. PHZ appears to age rather than kill RBCs, and younger RBCs are affected more than older RBCs. Blood sampling caused short aperiodic spikes in the proportion of reticulocytes which appear to have a different developmental pathway than normal reticulocytes. We also provide evidence of large diurnal oscillations in serum erythropoietin levels during anaemia

  1. FastStats: Life Expectancy

    MedlinePlus

    ... years of age by sex, race and Hispanic origin Health, United States 2015, table 15 [PDF - 9.8 MB] Life expectancy at birth and at 65 years of age, by sex: Organisation for Economic Co-operation and Development (OECD) countries Health, United States 2015, table 14 [PDF - 9. ...

  2. Modeling the Mechanical Consequences of Age-Related Trabecular Bone Loss by XFEM Simulation.

    PubMed

    Fan, Ruoxun; Gong, He; Zhang, Xianbin; Liu, Jun; Jia, Zhengbin; Zhu, Dong

    2016-01-01

    The elderly are more likely to suffer from fracture because of age-related trabecular bone loss. Different bone loss locations and patterns have different effects on bone mechanical properties. Extended finite element method (XFEM) can simulate fracture process and was suited to investigate the effects of bone loss on trabecular bone. Age-related bone loss is indicated by trabecular thinning and loss and may occur at low-strain locations or other random sites. Accordingly, several ideal normal and aged trabecular bone models were created based on different bone loss locations and patterns; then, fracture processes from crack initiation to complete failure of these models were observed by XFEM; finally, the effects of different locations and patterns on trabecular bone were compared. Results indicated that bone loss occurring at low-strain locations was more detrimental to trabecular bone than that occurring at other random sites; meanwhile, the decrease in bone strength caused by trabecular loss was higher than that caused by trabecular thinning, and the effects of vertical trabecular loss on mechanical properties were more severe than horizontal trabecular loss. This study provided a numerical method to simulate trabecular bone fracture and distinguished different effects of the possible occurrence of bone loss locations and patterns on trabecular bone. PMID:27403206

  3. Modeling the Mechanical Consequences of Age-Related Trabecular Bone Loss by XFEM Simulation

    PubMed Central

    Fan, Ruoxun; Zhang, Xianbin; Liu, Jun; Jia, Zhengbin; Zhu, Dong

    2016-01-01

    The elderly are more likely to suffer from fracture because of age-related trabecular bone loss. Different bone loss locations and patterns have different effects on bone mechanical properties. Extended finite element method (XFEM) can simulate fracture process and was suited to investigate the effects of bone loss on trabecular bone. Age-related bone loss is indicated by trabecular thinning and loss and may occur at low-strain locations or other random sites. Accordingly, several ideal normal and aged trabecular bone models were created based on different bone loss locations and patterns; then, fracture processes from crack initiation to complete failure of these models were observed by XFEM; finally, the effects of different locations and patterns on trabecular bone were compared. Results indicated that bone loss occurring at low-strain locations was more detrimental to trabecular bone than that occurring at other random sites; meanwhile, the decrease in bone strength caused by trabecular loss was higher than that caused by trabecular thinning, and the effects of vertical trabecular loss on mechanical properties were more severe than horizontal trabecular loss. This study provided a numerical method to simulate trabecular bone fracture and distinguished different effects of the possible occurrence of bone loss locations and patterns on trabecular bone. PMID:27403206

  4. Effects of age and sex on neuromuscular-mechanical determinants of muscle strength.

    PubMed

    Wu, Rui; Delahunt, Eamonn; Ditroilo, Massimiliano; Lowery, Madeleine; De Vito, Giuseppe

    2016-06-01

    The aim of this study was to concurrently assess the effect of age on neuromuscular and mechanical properties in 24 young (23.6 ± 3.7 years) and 20 older (66.5 ± 3.8 years) healthy males and females. Maximal strength of knee extensors (KE) and flexors (KF), contractile rate of torque development (RTD) and neural activation of agonist-antagonist muscles (surface EMG) were examined during maximal voluntary isometric contraction (MVIC). Tissue stiffness (i.e. musculo-articular stiffness (MAS) and muscle stiffness (MS)) was examined via the free-oscillation technique, whereas muscle architecture (MA) of the vastus lateralis and subcutaneous fat were measured by ultrasonography. Males exhibited a greater age-related decline for KE (47.4 %) and KF (53.1 %) MVIC, and RTD (60.4 %) when compared to females (32.9, 42.6 and 34.0 %, respectively). Neural activation of agonist muscles during KE MVIC falls markedly with ageing; however, no age and sex effects were observed in the antagonist co-activation. MAS and MS were lower in elderly compared with young participants and in females compared with males. Regarding MA, main effects for age (young 23.0 ± 3.3 vs older 19.5 ± 2.0 mm) and sex (males 22.4 ± 3.5 vs females 20.4 ± 2.7 mm) were detected in muscle thickness. For fascicle length, there was an effect of age (young 104.6 ± 8.8 vs older 89.8 ± 10.5 mm), while for pennation angle, there was an effect of sex (males 13.3 ± 2.4 vs females 11.5 ± 1.7°). These findings suggest that both neuromuscular and mechanical declines are important contributors to the age-related loss of muscle strength/function but with some peculiar sex-related differences. PMID:27189591

  5. Aging of Non-Visual Spectral Sensitivity to Light in Humans: Compensatory Mechanisms?

    PubMed Central

    Najjar, Raymond P.; Chiquet, Christophe; Teikari, Petteri; Cornut, Pierre-Loïc; Claustrat, Bruno; Denis, Philippe; Gronfier, Claude

    2014-01-01

    The deterioration of sleep in the older population is a prevalent feature that contributes to a decrease in quality of life. Inappropriate entrainment of the circadian clock by light is considered to contribute to the alteration of sleep structure and circadian rhythms in the elderly. The present study investigates the effects of aging on non-visual spectral sensitivity to light and tests the hypothesis that circadian disturbances are related to a decreased light transmittance. In a within-subject design, eight aged and five young subjects were exposed at night to 60 minute monochromatic light stimulations at 9 different wavelengths (420–620 nm). Individual sensitivity spectra were derived from measures of melatonin suppression. Lens density was assessed using a validated psychophysical technique. Although lens transmittance was decreased for short wavelength light in the older participants, melatonin suppression was not reduced. Peak of non-visual sensitivity was, however, shifted to longer wavelengths in the aged participants (494 nm) compared to young (484 nm). Our results indicate that increased lens filtering does not necessarily lead to a decreased non-visual sensitivity to light. The lack of age-related decrease in non-visual sensitivity to light may involve as yet undefined adaptive mechanisms. PMID:24465738

  6. Mechanisms of age-related decline in memory search across the adult life span.

    PubMed

    Hills, Thomas T; Mata, Rui; Wilke, Andreas; Samanez-Larkin, Gregory R

    2013-12-01

    Three alternative mechanisms for age-related decline in memory search have been proposed, which result from either reduced processing speed (global slowing hypothesis), overpersistence on categories (cluster-switching hypothesis), or the inability to maintain focus on local cues related to a decline in working memory (cue-maintenance hypothesis). We investigated these 3 hypotheses by formally modeling the semantic recall patterns of 185 adults between 27 to 99 years of age in the animal fluency task (Thurstone, 1938). The results indicate that people switch between global frequency-based retrieval cues and local item-based retrieval cues to navigate their semantic memory. Contrary to the global slowing hypothesis that predicts no qualitative differences in dynamic search processes and the cluster-switching hypothesis that predicts reduced switching between retrieval cues, the results indicate that as people age, they tend to switch more often between local and global cues per item recalled, supporting the cue-maintenance hypothesis. Additional support for the cue-maintenance hypothesis is provided by a negative correlation between switching and digit span scores and between switching and total items recalled, which suggests that cognitive control may be involved in cue maintenance and the effective search of memory. Overall, the results are consistent with age-related decline in memory search being a consequence of reduced cognitive control, consistent with models suggesting that working memory is related to goal perseveration and the ability to inhibit distracting information.

  7. Mechanisms of chemotherapy-induced human ovarian aging: double strand DNA breaks and microvascular compromise.

    PubMed

    Soleimani, Reza; Heytens, Elke; Darzynkiewicz, Zbigniew; Oktay, Kutluk

    2011-08-01

    The mechanism of chemotherapy-induced acceleration of ovarian aging is not fully understood. We used doxorubicin, a widely used cancer chemotherapeutic, in a variety of in vivo xenograft, and in vitro models to investigate the impact of chemotherapy-induced aging on the human ovary. Doxorubicin caused massive double-strand-DNA-breaks in primordial follicles, oocytes, and granulosa cells in a dose dependent fashion as revealed by accumulating γH2AX foci. This damage was associated with apoptotic oocyte death and resulted in the activation of ATM. It appeared that the repair response enabled a minor proportion of oocytes (34.7%) and granulosa cells (12.1%) to survive while the majority succumbed to apoptotic death. Paradoxically, inhibition of ATM by KU-55933 resulted in improved survival, probably via prevention of downstream activation of TAp63α. Furthermore, doxorubicin caused vascular and stromal damage in the human ovary, which might impair ovarian function both pre- and post-menopausally. Chemotherapy-induced premature ovarian aging appears to result from a complex process involving both the germ- and non-germ cell components of the ovary. These effects may have clinical implications in aging both for premenopausal and postmenopausal cancer survivors. PMID:21869459

  8. Changes in Structural-Mechanical Properties and Degradability of Collagen during Aging-associated Modifications.

    PubMed

    Panwar, Preety; Lamour, Guillaume; Mackenzie, Neil C W; Yang, Heejae; Ko, Frank; Li, Hongbin; Brömme, Dieter

    2015-09-18

    During aging, changes occur in the collagen network that contribute to various pathological phenotypes in the skeletal, vascular, and pulmonary systems. The aim of this study was to investigate the consequences of age-related modifications on the mechanical stability and in vitro proteolytic degradation of type I collagen. Analyzing mouse tail and bovine bone collagen, we found that collagen at both fibril and fiber levels varies in rigidity and Young's modulus due to different physiological changes, which correlate with changes in cathepsin K (CatK)-mediated degradation. A decreased susceptibility to CatK-mediated hydrolysis of fibrillar collagen was observed following mineralization and advanced glycation end product-associated modification. However, aging of bone increased CatK-mediated osteoclastic resorption by ∼27%, and negligible resorption was observed when osteoclasts were cultured on mineral-deficient bone. We observed significant differences in the excavations generated by osteoclasts and C-terminal telopeptide release during bone resorption under distinct conditions. Our data indicate that modification of collagen compromises its biomechanical integrity and affects CatK-mediated degradation both in bone and tissue, thus contributing to our understanding of extracellular matrix aging.

  9. Effects of age on the synergistic interactions between lipopolysaccharide and mechanical ventilation in mice.

    PubMed

    Smith, Lincoln S; Gharib, Sina A; Frevert, Charles W; Martin, Thomas R

    2010-10-01

    Children have a lower incidence and mortality from acute lung injury (ALI) than adults, and infections are the most common event associated with ALI. To study the effects of age on susceptibility to ALI, we investigated the responses to microbial products combined with mechanical ventilation (MV) in juvenile (21-d-old) and adult (16-wk-old) mice. Juvenile and adult C57BL/6 mice were treated with inhaled Escherichia coli 0111:B4 lipopolysaccharide (LPS) and MV using tidal volume = 15 ml/kg. Comparison groups included mice treated with LPS or MV alone and untreated age-matched control mice. In adult animals treated for 3 hours, LPS plus MV caused synergistic increases in neutrophils (P < 0.01) and IgM in bronchoalveolar lavage fluid (P = 0.03) and IL-1β in whole lung homogenates (P < 0.01) as compared with either modality alone. Although juvenile and adult mice had similar responses to LPS or MV alone, the synergistic interactions between LPS and MV did not occur in juvenile mice. Computational analysis of gene expression array data suggest that the acquisition of synergy with increasing age results, in part, from the loss of antiapoptotic responses and the acquisition of proinflammatory responses to the combination of LPS and MV. These data suggest that the synergistic inflammatory and injury responses to inhaled LPS combined with MV are acquired with age as a result of coordinated changes in gene expression of inflammatory, apoptotic, and TGF-β pathways.

  10. Changes in Structural-Mechanical Properties and Degradability of Collagen during Aging-associated Modifications*

    PubMed Central

    Panwar, Preety; Lamour, Guillaume; Mackenzie, Neil C. W.; Yang, Heejae; Ko, Frank; Li, Hongbin; Brömme, Dieter

    2015-01-01

    During aging, changes occur in the collagen network that contribute to various pathological phenotypes in the skeletal, vascular, and pulmonary systems. The aim of this study was to investigate the consequences of age-related modifications on the mechanical stability and in vitro proteolytic degradation of type I collagen. Analyzing mouse tail and bovine bone collagen, we found that collagen at both fibril and fiber levels varies in rigidity and Young's modulus due to different physiological changes, which correlate with changes in cathepsin K (CatK)-mediated degradation. A decreased susceptibility to CatK-mediated hydrolysis of fibrillar collagen was observed following mineralization and advanced glycation end product-associated modification. However, aging of bone increased CatK-mediated osteoclastic resorption by ∼27%, and negligible resorption was observed when osteoclasts were cultured on mineral-deficient bone. We observed significant differences in the excavations generated by osteoclasts and C-terminal telopeptide release during bone resorption under distinct conditions. Our data indicate that modification of collagen compromises its biomechanical integrity and affects CatK-mediated degradation both in bone and tissue, thus contributing to our understanding of extracellular matrix aging. PMID:26224630

  11. Effect of aging on islet beta-cell function and its mechanisms in Wistar rats.

    PubMed

    Gu, Zhaoyan; Du, Yingzhen; Liu, Yu; Ma, Lichao; Li, Lin; Gong, Yanping; Tian, Hui; Li, Chunlin

    2012-12-01

    Type 2 diabetes mellitus is characterized by islet β-cell dysfunction and its incidence increases with age. However, the mechanisms underlying the effect of aging on islet β-cell function are not fully understood. We characterized β-cell function in 4-month-old (young), 14-month-old (adult), and 24-month-old (old) male Wistar rats, and found that islet β-cell function decreased gradually with age. Old rats displayed oral glucose intolerance and exhibited a decrease in glucose-stimulated insulin release (GSIR) and palmitic acid-stimulated insulin release (PSIR). Furthermore, total superoxide dismutase (T-SOD), CuZn superoxide dismutase (CuZn-SOD), and glutathione peroxidase (GSH-Px) activity decreased, whereas serum malondialdehyde (MDA) levels increased in the older rats. Moreover, we detected a significant reduction in β-cell proliferation and an increase in the frequency of apoptotic β-cells in the islets of rats in the old group. Finally, Anxa1 expression in the islets of old rats was significantly upregulated. These data provide new insights into the development of age-related β-cell dysfunction in rats.

  12. Importance of age on the dynamic mechanical behavior of intertubular and peritubular dentin.

    PubMed

    Ryou, Heonjune; Romberg, Elaine; Pashley, David H; Tay, Franklin R; Arola, Dwayne

    2015-02-01

    An experimental evaluation of human coronal dentin was performed using nanoscopic dynamic mechanical analysis (nanoDMA). The primary objectives were to quantify any unique changes in mechanical behavior of intertubular and peritubular dentin with age, and to evaluate the microstructure and mechanical behavior of the mineral deposited within the lumens. Specimens of coronal dentin were evaluated by nanoDMA using single indents and in scanning mode via scanning probe microscopy. Results showed that there were no significant differences in the storage modulus or complex modulus between the two age groups (18-25 versus 54-83 yrs) for either the intertubular or peritubular tissue. However, there were significant differences in the dampening behavior between the young and old dentin, as represented in the loss modulus and tanδ responses. For both the intertubular and peritubular components, the capacity for dampening was significantly lower in the old group. Scanning based nanoDMA showed that the tubules of old dentin exhibit a gradient in elastic behavior, with decrease in elastic modulus from the cuff to the center of tubules filled with newly deposited mineral.

  13. Extreme lifespan of the human fish (Proteus anguinus): a challenge for ageing mechanisms

    PubMed Central

    Voituron, Yann; de Fraipont, Michelle; Issartel, Julien; Guillaume, Olivier; Clobert, Jean

    2011-01-01

    Theories of extreme lifespan evolution in vertebrates commonly implicate large size and predator-free environments together with physiological characteristics like low metabolism and high protection against oxidative damages. Here, we show that the ‘human fish’ (olm, Proteus anguinus), a small cave salamander (weighing 15–20 g), has evolved an extreme life-history strategy with a predicted maximum lifespan of over 100 years, an adult average lifespan of 68.5 years, an age at sexual maturity of 15.6 years and lays, on average, 35 eggs every 12.5 years. Surprisingly, neither its basal metabolism nor antioxidant activities explain why this animal sits as an outlier in the amphibian size/longevity relationship. This species thus raises questions regarding ageing processes and constitutes a promising model for discovering mechanisms preventing senescence in vertebrates. PMID:20659920

  14. Bone Aging by Advanced Glycation End Products: A Multiscale Mechanical Analysis.

    PubMed

    Ganeko, K; Masaki, C; Shibata, Y; Mukaibo, T; Kondo, Y; Nakamoto, T; Miyazaki, T; Hosokawa, R

    2015-12-01

    The quality and quantity of mandibular bone are essential prerequisites for osseointegrated implants. Only the Hounsfield unit on preoperative computed tomography is currently used as a clinical index. Nevertheless, a considerable mismatch occurs between bone quality and the Hounsfield unit. Loss of bone toughness during aging has been accepted based on empirical evidence, but this concept is unlikely evidence based at the level of mechanical properties. Nonenzymatic bone matrix cross-links associated with advanced glycation end products predominate as a consequence of aging. Thus, loss of tissue integrity could diminish the bone toughening mechanism. Here, we demonstrate an impaired bone toughening mechanism caused by mimicking aging in rabbits on a methionine-rich diet, which enabled an enhanced nonenzymatically cross-linked bone matrix. A 3-point bending test revealed a greater reduction in femoral fracture resistance in rabbits on a methionine-rich diet, despite higher maximum and normalized breaking forces (287.3 N and 88.1%, respectively), than in rabbits on a normal diet (262.2 N and 79.7%, respectively). In situ nanoindentation on mandibular cortical bone obtained from rabbits on a methionine-rich diet did not enable strain rate-dependent stiffening and consequent large-dimensional recovery during rapid loading following constant displacement after a rapid-load indentation test as compared with those in rabbits on a normal diet. Such nanoscale structure-function relationships dictate resistance to cracking propagation at the material level and allow for the overall bone toughening mechanism to operate under large external stressors. The strain-dependent stiffening was likely associated with strain-energy transfer to the superior cross-linked bone matrix network of the normal diet, while the reduction in the enzymatically cross-linked matrix in bone samples from rabbits on a methionine-rich diet likely diminished the intrinsic bone toughening mechanism. The

  15. Effects of age on the physiological and mechanical characteristics of human femoropopliteal arteries.

    PubMed

    Kamenskiy, Alexey V; Pipinos, Iraklis I; Dzenis, Yuris A; Phillips, Nicholas Y; Desyatova, Anastasia S; Kitson, Justin; Bowen, Robert; MacTaggart, Jason N

    2015-01-01

    Surgical and interventional therapies for peripheral artery disease (PAD) are notorious for high rates of failure. Interactions between the artery and repair materials play an important role, but comprehensive data describing the physiological and mechanical characteristics of human femoropopliteal arteries are not available. Fresh femoropopliteal arteries were obtained from 70 human subjects (13-79 years old), and in situ vs. excised arterial lengths were measured. Circumferential and longitudinal opening angles were determined for proximal superficial femoral, proximal popliteal and distal popliteal arteries. Mechanical properties were assessed by multi-ratio planar biaxial extension, and experimental data were used to calculate physiological stresses and stretches, in situ axial force and anisotropy. Verhoeff-Van Gieson-stained axial and transverse arterial sections were used for histological analysis. Most specimens demonstrated nonlinear deformations and were more compliant longitudinally than circumferentially. In situ axial pre-stretch decreased 0.088 per decade of life. In situ axial force and axial stress also decreased with age, but circumferential physiological stress remained constant. Physiological circumferential stretch decreased 55-75% after 45 years of age. Histology demonstrated a thickened external elastic lamina with longitudinally oriented elastin that was denser in smaller, younger arteries. Axial elastin likely regulates axial pre-stretch to help accommodate the complex deformations required of the artery wall during locomotion. Degradation and fragmentation of elastin as a consequence of age, cyclic mechanical stress and atherosclerotic arterial disease may contribute to decreased in situ axial pre-stretch, predisposing to more severe kinking of the artery during limb flexion and loss of energy-efficient arterial function.

  16. Microstructure and Mechanical Instability of Water-Quenched U-6wt% Nb Alloy Affected by Long-Term Aging

    SciTech Connect

    Hsiung, L; Zhou, J

    2005-12-06

    A combinative approach of microhardness testing, tensile testing, and TEM microstructural analysis was employed to study the microstructure and mechanical instability of a water-quenched U-6wt.% Nb (WQ-U6Nb) alloy subjected to different aging schedules including artificial aging at 200 C, 15-year natural aging at ambient temperatures, and 15-year natural aging followed by accelerative aging at 200 C. The changes in mechanical property during and after the aging processes were examined using microhardness and tensile-testing methods. During the early stages of artificial aging at 200 C, the microhardness of WQ-U6Nb alloy increased, i.e., age hardening, as a result of the development of nanoscale modulation caused by spinodal decomposition. Coarsening of the modulated structure occurred after a prolonged aging at 200 C for 16 hours, and it led to a decrease of microhardness, i.e., age softening. Phase instability was also found to occur in WQ-U6Nb alloy that was subjected to a 15-year natural aging at ambient temperatures. The formation of partially ordered domains resulting from a spinodal modulation with an atomic-scale wavelength rendered the appearance of swirl-shape antiphase domain boundaries (APBs) observed in TEM images. Although it did not cause a significant change in microhardness, 15-year natural aging has dramatically affected the aging mechanisms of the alloy isothermally aged at 200 C. Microhardness values of the NA alloy continuously increased and no age softening was found after isothermal aging at 200 C for 96 hours as a result of the phase decomposition of partially ordered domains into Nb-depleted {alpha} phase and Nb-enriched U{sub 3}Nb ordered phase in the alloy. It is concluded that the long-term natural aging changes the transformation pathway of WQ-U6Nb, and it leads to order-disorder transformation, precipitation hardening, and ductility embrittlement of WQ-U6Nb alloy.

  17. Recent fracture mechanics results from NASA research related to the aging commercial transport fleet

    NASA Technical Reports Server (NTRS)

    Harris, Charles E.

    1991-01-01

    NASA is conducting the Airframe Structural Integrity Program in support of the aging commercial transport fleet. This interdisciplinary program is being worked in cooperation with the U.S. airframe manufacturers, airline operators, and the FAA. Advanced analysis methods are under development to predict the fatigue crack growth in complex built-up shell structures. Innovative nondestructive examination technologies are also under development to provide large area inspection capability to detect corrosion, disbonds, and fatigue cracks. Recent fracture mechanics results applicable to predicting the growth of cracks initiating at the rivets of fuselage splice joints are reviewed.

  18. Fracture mechanics research at NASA related to the aging commercial transport fleet

    NASA Technical Reports Server (NTRS)

    Newman, James C., Jr.; Harris, Charles E.

    1992-01-01

    NASA is conducting the Airframe Structural Integrity Program in support of the aging commercial transport fleet. This interdisciplinary program is being worked in cooperation with the U.S. airframe manufacturers, airline operators, and the FAA. Advanced analysis methods are under development and an extensive testing program is under way to study fatigue crack growth and fracture in complex built-up shell structures. Innovative nondestructive examination technologies are also being developed to provide large area inspection capability to detect corrosion, disbonds, and cracks. Recent fracture mechanics results applicable to predicting the growth of cracks under monotonic and cyclic loading at rivets in fuselage lap-splice joints are reviewed.

  19. Oral sapropterin augments reflex vasoconstriction in aged human skin through noradrenergic mechanisms.

    PubMed

    Stanhewicz, Anna E; Alexander, Lacy M; Kenney, W Larry

    2013-10-01

    Reflex vasoconstriction is attenuated in aged skin due to a functional loss of adrenergic vasoconstriction. Bioavailability of tetrahydrobiopterin (BH4), an essential cofactor for catecholamine synthesis, is reduced with aging. Locally administered BH4 increases vasoconstriction through adrenergic mechanisms in aged human skin. We hypothesized that oral sapropterin (Kuvan, a pharmaceutical BH4) would augment vasoconstriction elicited by whole-body cooling and tyramine perfusion in aged skin. Ten healthy subjects (age 75 ± 2 yr) ingested sapropterin (10 mg/kg) or placebo in a randomized, double-blind crossover design. Venous blood samples were collected prior to, and 3 h following ingestion. Three intradermal microdialysis fibers were placed in the forearm skin for local delivery of 1) lactated Ringer, 2) 5 mM BH4, and 3) 5 mM yohimbine + 1 mM propranolol (Y+P; to inhibit adrenergic vasoconstriction). Red cell flux was measured at each site by laser-Doppler flowmetry (LDF) as reflex vasoconstriction was induced by lowering and then clamping whole-body skin temperature (Tsk) using a water-perfused suit. Following whole-body cooling, subjects were rewarmed and 1 mM tyramine was perfused at each site to elicit endogenous norepinephrine release from the perivascular nerve terminal. Cutaneous vascular conductance was calculated as CVC = LDF/mean arterial pressure and expressed as change from baseline (ΔCVC). Plasma BH4 was elevated 3 h after ingestion of sapropterin (43.8 ± 3 vs. 19.1 ± 2 pmol/ml; P < 0.001). Sapropterin increased reflex vasoconstriction at the Ringer site at Tsk ≤ 32.5°C (P < 0.05). Local BH4 perfusion augmented reflex vasoconstriction at Tsk ≤ 31.5°C with placebo treatment only (P < 0.05). There was no treatment effect on reflex vasoconstriction at the BH4-perfused or Y+P-perfused sites. Sapropterin increased pharmacologically induced vasoconstriction at the Ringer site (-0.19 ± 0.03 vs. -0.08 ± 0.02 ΔCVC; P = 0.01). There was no

  20. [The study of the effectiveness of drug prevention mechanisms of cardiovascular aging by cytoflavin].

    PubMed

    Kartashova, E A; Romantsov, M G; Sarvilina, I V

    2014-01-01

    The aim of the research was the search of the mechanism of Cytoflavin action in patients with isolated systolic arterial hypertension (ISAH) as the aging model. The following research methods were applied: the assessment of complaints, 24-hour arterial pressure monitoring, ultrasound diagnostic, volume sphygmography, lipid profiles and coagulogram, molecular phenotyping by MALDI-TOF-TOF-MS. The combination of Cytoflavin with standard therapy of ISAH led to the most expressed return development of clinical symptoms, the restoration of the haemodynamics, structural and geometrical parameters of cardiovascular system, indicators lipid profiles and coagulogram in the comparison with patients with ISAH, who accepted standard therapy and those of the control groups. Molecular mechanisms of Cytoflavin action, including regulation of the activity of cell signaling pathways through intermolecular interactions were found. We recommend using Cytoflavin together with the standard therapy in treatment of ISAH, which provides the action of geroprotectors for cardiovascular system.

  1. Age-related ransparent root dentin: mineral concentration,crystallite size and mechanical properties

    SciTech Connect

    Kinney, John H.; Nalla, Ravi K.; Pople, John A.; Breunig, Tom M.; Ritchie, Robert O.

    2004-12-29

    Many fractures occur in teeth that have been altered, forexample restored or endodontically repaired. It is therefore essential toevaluate the structure and mechanical properties of these altereddentins. One such altered form of dentin is transparent (sometimes calledsclerotic) dentin, which forms gradually with aging. The present studyfocuses on differences in the structure and mechanical properties ofnormal versus transparent dentin. The mineral concentration, as measuredby X-ray computed microtomography, was signifcantly higher in transparentdentin, the elevated concentration being consistent with the closure ofthe tubule lumens. Crystallite size, as measured by small angle X-rayscattering, was slightly smaller in transparent dentin, although theimportance of this ending requires further study. The elastic propertieswere unchanged by transparency; however, transparent dentin, unlikenormal dentin, exhibited almost no yielding before failure. In addition,the fracture toughness was lowered by roughly 20 percent while thefatigue lifetime was deleteriously affected at high stress levels. Theseresults are discussed in terms of the altered microstructure oftransparent dentin.

  2. On the age and formation mechanism of the core of the Quadrantid meteoroid stream

    NASA Astrophysics Data System (ADS)

    Abedin, Abedin; Spurný, Pavel; Wiegert, Paul; Pokorný, Petr; Borovička, Jiří; Brown, Peter

    2015-11-01

    The Quadrantid meteor shower is among the strongest annual meteor showers, and has drawn the attention of scientists for several decades. The stream is unusual, among others, for several reasons: its very short duration around maximum activity (≈12-14 h) as detected by visual, photographic and radar observations, its recent onset (around 1835 AD Quetelet, L.A.J. [1839]. Catalogue des principles apparitions d'etoiles filantes) and because it had been the only major stream without an obvious parent body until 2003. Ever since, there have been debates as to the age of the stream and the nature of its proposed parent body, asteroid 2003 EH1. In this work, we present results on the most probable age and formation mechanism of the narrow portion of the Quadrantid meteoroid stream. For the first time we use data on eight high precision photographic Quadrantids, equivalent to gram-kilogram size, to constrain the most likely age of the core of the stream. Out of eight high-precision photographic Quadrantids, five pertain directly to the narrow portion of the stream. In addition, we also use data on five high-precision radar Quadrantids, observed within the peak of the shower. We performed backwards numerical integrations of the equations of motion of a large number of 'clones' of both, the eight high-precision photographic and five radar Quadrantid meteors, along with the proposed parent body, 2003 EH1. According to our results, from the backward integrations, the most likely age of the narrow structure of the Quadrantids is between 200 and 300 years. These presumed ejection epochs, corresponding to 1700-1800 AD, are then used for forward integrations of large numbers of hypothetical meteoroids, ejected from the parent 2003 EH1, until the present epoch. The aim is to constrain whether the core of the Quadrantid meteoroid stream is consistent with a previously proposed relatively young age (≈200 years).

  3. Optical characters and texture maps of skin and the aging mechanism by use of multiphoton microscopy and optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Wu, Shulian; Li, Hui; Zhang, Xiaoman; Huang, Yudian; Xu, Xiaohui

    2012-03-01

    Cutaneous aging is a complicated biological process affecting different constituents of skin, which can be divided into two types: the chronological aging and the photo-aging. The two cutaneous aging processes often co-exist accompanying with each other. The effects are often overlapped including changes in epithelium and dermis. The degeneration of collagen is a major factor in dermal alteration with aging. In this study, multiphoton microscopy (MPM) with its high resolution imaging and optical coherence tomography (OCT) with its depth resolved imaging were used to study the anti-aging dermatology in vivo. It was attempted to make the optical parameter and texture feature to evaluate the process of aging skin using mathematical image processing. The links among optical parameter, spectrum and texture feature in collagen with aging process were established to uncover mechanism of aging skin.

  4. Increased endoplasmic reticulum stress in mouse osteocytes with aging alters Cox-2 response to mechanical stimuli.

    PubMed

    Chalil, Sreeda; Jaspers, Richard T; Manders, Ralph J; Klein-Nulend, Jenneke; Bakker, Astrid D; Deldicque, Louise

    2015-02-01

    Aging reduces bone mass as well as the anabolic response of bone to mechanical stimuli, resulting in osteopenia. Endoplasmic reticulum (ER) stress impairs the response of myogenic cells to anabolic stimuli, and is involved in sarcopenia, but whether ER stress also contributes to osteopenia is unknown. Therefore, we tested whether ER stress exists in bones of aged mice, and whether this impairs the osteocyte response to mechanical stimulation. Primary osteocytes were obtained from long bones of adult (8 months) and old (24-26 months) mice, treated with or without the pharmacological ER stress inducer tunicamycin, and either or not subjected to mechanical loading by pulsating fluid flow (PFF). The osteocyte response to PFF was assessed by measuring cyclooxygenase-2 (Cox-2) mRNA levels and nitric oxide (NO) production. mRNA levels of ER stress markers were higher in old versus adult osteocytes (+40% for activating transcription factor-4, +120% for C/EBP homologous protein, and +120% for spliced X-box binding protein-1, p < 0.05). The Cox-2 response to PFF was fourfold decreased in cells from old bones (p < 0.001), while tunicamycin decreased PFF-induced Cox-2 expression by threefold in cells from adult bones (p < 0.01). PFF increased NO production by 50% at 60 min in osteocytes from old versus adult bones (p < 0.01). In conclusion, our data indicate that the expression of several ER stress markers was higher in osteocytes from bones of old compared to adult mice. Since ER stress altered the response of osteocytes to mechanical loading, it could be a novel factor contributing to osteopenia. PMID:25539857

  5. Reactive molecule species and antioxidative mechanisms in normal skin and skin aging.

    PubMed

    Wölfle, Ute; Seelinger, Günter; Bauer, Georg; Meinke, Martina C; Lademann, Jürgen; Schempp, Christoph M

    2014-01-01

    Reactive oxygen and nitrogen species (ROS/RNS) which may exist as radicals or nonradicals, as well as reactive sulfur species and reactive carbon species, play a major role in aging processes and in carcinogenesis. These reactive molecule species (RMS), often referred to as 'free radicals' or oxidants, are partly by-products of the physiological metabolism. When RMS concentrations exceed a certain threshold, cell compartments and cells are injured and destroyed. Endogenous physiological mechanisms are able to neutralize RMS to some extent, thereby limiting damage. In the skin, however, pollutants and particularly UV irradiation are able to produce additional oxidants which overload the endogenous protection system and cause early aging, debilitation of immune functions, and skin cancer. The application of antioxidants from various sources in skin care products and food supplements is therefore widespread, with increasingly effective formulations being introduced. The harmful effects of RMS (aside from impaired structure and function of DNA, proteins, and lipids) are: interference with specific regulatory mechanisms and signaling pathways in cell metabolism, resulting in chronic inflammation, weakening of immune functions, and degradation of tissue. Important control mechanisms are: MAP-kinases, the aryl-hydrocarbon receptor (AhR), the antagonistic transcription factors nuclear factor-κB and Nrf2 (nuclear factor erythroid 2-related factor 2), and, especially important, the induction of matrix metalloproteinases which degrade dermal connective tissue. Recent research, however, has revealed that RMS and in particular ROS/RNS are apparently also produced by specific enzyme reactions in an evolutionarily adapted manner. They may fulfill important physiologic functions such as the activation of specific signaling chains in the cell metabolism, defense against infectious pathogens, and regulation of the immune system. Normal physiological conditions are characterized by

  6. Non contact method for in vivo assessment of skin mechanical properties for assessing effect of ageing.

    PubMed

    Boyer, G; Pailler Mattei, C; Molimard, J; Pericoi, M; Laquieze, S; Zahouani, H

    2012-03-01

    The assessment of human tissue properties by objective and quantitative devices is very important to improve the understanding of its mechanical behaviour. The aim of this paper is to present a non contact method to measure the mechanical properties of human skin in vivo. A complete non contact device using an air flow system has been developed. Validation and assessment of the method have been performed on inert visco-elastic material. An in vivo study on the forearm of two groups of healthy women aged of 23.2±1.6 and 60.4±2.4 has been performed. Main parameters assessed are presented and a first interpretation to evaluate the reduced Young's modulus is proposed. Significant differences between the main parameters of the curve are shown with ageing. As tests were performed with different loads, the influence of the stress is also observed. We found a reduced Young's modulus with an air flow force of 10 mN of 14.38±3.61 kPa for the youngest group and 6.20±1.45 kPa for the oldest group. These values agree with other studies using classical or dynamic indentation. Non contact test using the developed device gives convincing results.

  7. Ageing under mechanical stress: first experiments for a silver based multilayer mirror

    NASA Astrophysics Data System (ADS)

    Lalo, Arnaud; Ravel, Guillaume; Ignat, Michel; Cousin, Bernard; Swain, Michael V.

    2004-06-01

    Improving materials and devices reliability is a major concern to the spatial industry. Results are reported for satellite mirrors-like specimens consisting in oxide-protected metal systems. Optical coatings were deposited by electron beam evaporation. Mechanical stress fields in multi-layered materials play an important role. The stress state can have far-reaching implications both in kinetics and thermodynamics. Therefore an integrated apparatus with four-point bending equipment was designed. The technique allowed us to exert stress into a film or a system of films on a substrate concurrently with thermal treatment. In order to achieve the first tests performed with the help of the apparatus, various preliminary characterizations were required. The article reports the preliminary micro-mechanical testing of the materials (ultra micro-indentation to evaluate the elastic modulus of the samples materials and wafer curvature technique to determine the specimen residual stress) and the first ageing experiment. Experimental evidence of accelerated ageing under stress is successfully reported.

  8. Influence of age on mechanical properties of healing fractures and intact bones in rats.

    PubMed

    Ekeland, A; Engesoeter, L B; Langeland, N

    1982-08-01

    Mechanical properties of fractured and intact femora have been studied in young and adult, male rats. A standardized, closed, mid-diaphyseal fracture was produced in the left femur, the right femur serving as control. The fracture was left to heal without immobilization. At various intervals, both fractured and intact femora were loaded in torsion until failure. The fractured femora regained the mechanical properties of the contralateral, intact bones after about 4 weeks in young and after about 12 weeks in adult rats. For intact bones, both the ultimate torsional moment (strength) and the torsional stiffness increased with age of the animals, whereas the ultimate torsional angle remained unchanged. For bone as a material, however, the ultimate torsional stress (strength) and the modulus of rigidity (stiffness) increased with age only in young rats, being almost constant in the adult animals. The various biomechanical parameters of the healing fractures did not reach those of the contralateral, intact bones simultaneously. The torsional moment required to twist a healing femoral fracture 20 degrees (0.35 radians), a deformation close to what an intact femur can resist, proved to be a functional and simple measure of the degree of fracture repair in rats.

  9. Distinct mechanisms for the impact of distraction and interruption on working memory in aging

    PubMed Central

    Clapp, Wesley C; Gazzaley, Adam

    2010-01-01

    Interference is known to negatively impact the ability to maintain information in working memory (WM), an effect that is exacerbated with aging. Here, we explore how distinct sources of interference, i.e., distraction (stimuli to-be-ignored) and interruption (stimuli requiring attention), differentially influence WM in younger and older adults. EEG was recorded while participants engaged in three versions of a delayed-recognition task: no interference, a distracting stimulus, and an interrupting stimulus presented during WM maintenance. Behaviorally, both types of interference negatively impacted WM accuracy in older adults significantly more than younger adults (with a larger deficit for interruptions). N170 latency measures revealed that the degree of processing both distractors and interruptors predicted WM accuracy in both populations. However, while WM impairments could be explained by excessive attention to distractors by older adults (a suppression deficit), impairment induced by interruption were not clearly mediated by age-related increases in attention to interruptors. These results suggest that distinct underlying mechanisms mediate the impact of different types of external interference on WM in normal aging. PMID:20144492

  10. Age hardening characteristics and mechanical behavior of Al-Cu-Li-Zr-In alloys

    NASA Technical Reports Server (NTRS)

    Wagner, John A.

    1989-01-01

    An investigation was conducted to determine the age-hardening response and cryogenic mechanical properties of superplastic Al-Cu-Li-Zr-In alloys. Two alloys with compositions Al-2.65Cu-2.17Li-O.13Zr (baseline) and Al-2.60Cu-2.34Li-0.16Zr-0.17In were scaled-up from 30 lb permanent mold ingots to 350 lb DC (direct chill) ingots and thermomechanically processed to 3.2 mm thick sheet. The microstructure of material which contained the indium addition was partially recrystallized compared to the baseline suggesting that indium may influence recrystallization behavior. The indium-modified alloy exhibited superior hardness and strength compared to the baseline alloy when solution-heat-treated at 555 C and aged at 160 C or 190 C. For each alloy, strength increased and toughness was unchanged or decreased when tested at - 185 C compared to ambient temperature. By using optimized heat treatments, the indium-modified alloy exhibited strength levels approaching those of the baseline alloy without deformation prior to aging. The increase in strength of these alloys in the T6 condition make them particularly attractive for superplastic forming applications where post-SPF parts cannot be cold deformed to increase strength.

  11. Modeling the mechanical behavior of vertebral trabecular bone: effects of age-related changes in microstructure.

    PubMed

    Silva, M J; Gibson, L J

    1997-08-01

    Age-related reductions in the thickness and number of trabeculae in vertebral trabecular bone have been documented by several workers, yet the relative effects of these changes on mechanical properties are not known. We developed a two-dimensional model of human vertebral trabecular bone and investigated its mechanical behavior using finite element analysis. The stress-strain behavior, failure mode, and strain distributions predicted using the model were consistent with those observed for vertebral trabecular bone under compressive loading. Random reductions in the number of trabeculae reduced the modulus and strength of the models two to five times more than uniform reductions in the thickness of trabeculae that caused the same loss of bone volume. For example, randomly removing longitudinal trabeculae to achieve a reduction in density of 10% reduced the strength by approximately 70%, whereas removing the same amount of bone by uniformly reducing the thickness of the longitudinal trabeculae only reduced the strength by approximately 20%. For a simulation of aged bone, in which the thickness and number of trabeculae were reduced concurrently, the strength was 23% of its intact ("young") value. When the bone mass of the aged model was restored to its intact level by increasing the thickness but not the number of trabeculae, the strength increased by 60%, but was still only 37% of its intact value. These combined findings, based on a two-dimensional, idealized model of vertebral trabecular bone, illustrate the importance of maintaining trabecular number and suggest that it may not be possible to restore bone strength following a period of advanced bone loss if a substantial number of trabeculae have been resorbed. Thus, until treatments exist that can increase trabecular number, the most effective treatment strategy is to prevent the degradation of bone strength by maintaining the number of trabeculae at a healthy level.

  12. Mechanical and Physical Properties of Both Unaged and Aged Coflon and Tefzel. Revised 18 Mar. 1997

    NASA Technical Reports Server (NTRS)

    Samulak, M.; Campion, R. P.

    1996-01-01

    This report deals with all recent mechanical testing performed on variously aged samples of Coflon and TefzeL to complete the work for Phase 1. Earlier results were reported in CAPP/M.7. Fluids A, F, G, and I have all been used for ageing in the last 12 month period, with particular attention concentrated on the effects of Fluid F as a result of discussions at the December 1995 steering committee meeting in Austin. Dramatic mechanical and physical changes occurred to Coflon in our initial studies after 4 weeks at 120 C in this sour gas mixture and so a detailed matrix was drawn up to investigate the effects of time and temperature of exposure. Subsequent tensile tests and compact tension (CT) fatigue tests were performed. Fatigue testing has been limited during this period to Coflon only; however, Tefzel CT samples have been exposed to the same conditions as the Coflon allowing the possibility for fatigue tests to be performed at a later date. Fluid A exposures during the last 6 months have been long-term at 65 C, 100 C and 120 C only. These exposures have been a continuation of earlier work and will complete the investigation of this fluid. Other chemical ageings have involved Fluid G at 120 C to confirm and investigate the hostile nature of this fluid on Coflon. Again, this fluid will not be used in Phase 2. Finally, long-term exposures in Fluid 1, a high aromatic oil mixture, were carried out to investigate the effects on the polymers of aromaticity in a simulated service fluid.

  13. Mechanisms underlying the production of false memories for famous people's names in aging and Alzheimer's disease.

    PubMed

    Plancher, Gaën; Guyard, Anne; Nicolas, Serge; Piolino, Pascale

    2009-10-01

    It is well known that the occurrence of false memories increases with aging, but the results remain inconsistent concerning Alzheimer's disease (AD). Moreover, the mechanisms underlying the production of false memories are still unclear. Using an experimental episodic memory test with material based on the names of famous people in a procedure derived from the DRM paradigm [Roediger, H. L., III, & McDermott, K. B. (1995). Creating false memories: Remembering words not presented in lists. Journal of Experimental Psychology: Learning, Memory & Cognition, 21, 803-814], we examined correct and false recall and recognition in 30 young adults, 40 healthy older adults, and 30 patients with AD. Moreover, we evaluated the relationships between false memory performance, correct episodic memory performance, and a set of neuropsychological assessments evaluating the semantic memory and executive functions. The results clearly indicated that correct recall and recognition performance decreased with the subjects' age, but it decreased even more with AD. In addition, semantically related false recalls and false recognitions increased with age but not with dementia. On the contrary, non-semantically related false recalls and false recognitions increased with AD. Finally, the regression analyses showed that executive functions mediated related false memories and episodic memory mediated related and unrelated false memories in aging. Moreover, executive functions predicted related and unrelated false memories in AD, and episodic and semantic memory predicted semantically related and unrelated false memories in AD. In conclusion, the results obtained are consistent with the current constructive models of memory suggesting that false memory creation depends on different cognitive functions and, consequently, that the impairments of these functions influence the production of false memories.

  14. Mechanical properties of thermally aged cast stainless steels from shippingport reactor components.

    SciTech Connect

    Chopra, O. K.; Shack, W. J.; Energy Technology

    1995-06-07

    Thermal embrittlement of static-cast CF-8 stainless steel components from the decommissioned Shippingport reactor has been characterized. Cast stainless steel materials were obtained from four cold-leg check valves, three hot-leg main shutoff valves, and two pump volutes. The actual time-at-temperature for the materials was {approx}13 y at {approx}281 C (538 F) for the hot-leg components and {approx}264 C (507 F) for the cold-leg components. Baseline mechanical properties for as-cast material were determined from tests on either recovery-annealed material, i.e., annealed for 1 h at 550 C and then water quenched, or material from the cooler region of the component. The Shippingport materials show modest decreases in fracture toughness and Charpy-impact properties and a small increase in tensile strength because of relatively low service temperatures and ferrite content of the steel. The procedure and correlations developed at Argonne National Laboratory for estimating mechanical properties of cast stainless steels predict accurate or slightly lower values for Charpy-impact energy, tensile flow stress, fracture toughness J-R curve, and JIC of the materials. The kinetics of thermal embrittlement and degree of embrittlement at saturation, i.e., the minimum impact energy achieved after long-term aging, were established from materials that were aged further in the laboratory. The results were consistent with the estimates. The correlations successfully predicted the mechanical properties of the Ringhals 2 reactor hot- and crossover-leg elbows (CF-8M steel) after service of {approx}15 y and the KRB reactor pump cover plate (CF-8) after {approx}8 y of service.

  15. Mechanical properties of thermally aged cast stainless steels from Shippingport reactor components

    SciTech Connect

    Chopra, O.K.; Shack, W.J.

    1995-04-01

    Thermal embrittlement of static-cast CF-8 stainless steel components from the decommissioned Shippingport reactor has been characterized. Cast stainless steel materials were obtained from four cold-leg check valves, three hot-leg main shutoff valves, and two pump volutes. The actual time-at-temperature for the materials was {approximately}13 y at {approximately}281 C (538 F) for the hot-leg components and {approximately}264 C (507 F) for the cold-leg components. Baseline mechanical properties for as-cast material were determined from tests on either recovery-annealed material, i.e., annealed for 1 h at 550 C and then water quenched, or material from the cooler region of the component. The Shippingport materials show modest decreases in fracture toughness and Charpy-impact properties and a small increase in tensile strength because of relatively low service temperatures and ferrite content of the steel. The procedure and correlations developed at Argonne National Laboratory for estimating mechanical properties of cast stainless steels predict accurate or slightly lower values for Charpy-impact energy, tensile flow stress, fracture toughness J-R curve, and J{sub IC} of the materials. The kinetics of thermal embrittlement and degree of embrittlement at saturation, i.e., the minimum impact energy achieved after long-term aging, were established from materials that were aged further in the laboratory. The results were consistent with the estimates. The correlations successfully predicted the mechanical properties of the Ringhals 2 reactor hot and crossover-leg elbows (CF-8M steel) after service of {approximately} 15 y and the KRB reactor pump cover plate (CF-8) after {approximately} 8 y of service.

  16. The ethics of life expectancy.

    PubMed

    Small, Robin

    2002-08-01

    Some ethical dilemmas in health care, such as over the use of age as a criterion of patient selection, appeal to the notion of life expectancy. However, some features of this concept have not been discussed. Here I look in turn at two aspects: one positive--our expectation of further life--and the other negative--the loss of potential life brought about by death. The most common method of determining this loss, by counting only the period of time between death and some particular age, implies that those who die at ages not far from that one are regarded as losing very little potential life, while those who die at greater ages are regarded as losing none at all. This approach has methodological advantages but ethical disadvantages, in that it fails to correspond to our strong belief that anyone who dies is losing some period of life that he or she would otherwise have had. The normative role of life expectancy expressed in the 'fair innings' attitude arises from a particular historical situation: not the increase of life expectancy in modern societies, but a related narrowing in the distribution of projected life spans. Since life expectancy is really a representation of existing patterns of mortality, which in turn are determined by many influences, including the present allocation of health resources, it should not be taken as a prediction, and still less as a statement of entitlement. PMID:12956176

  17. Investigation of the Dynamic Strain Aging and Mechanical Properties in Alloy-625 with Different Microstructures

    NASA Astrophysics Data System (ADS)

    Chatterjee, Arnomitra; Sharma, Garima; Tewari, R.; Chakravartty, J. K.

    2015-03-01

    Tensile tests were carried out on service exposed Alloy 625 ammonia cracker tube used at heavy water production plant to study the effect of microstructure on the serrated yielding and mechanical properties of the material. Owing to temperature gradient during service exposure, the microstructure was different in top, middle, and bottom sections of the tube. Variation of flow stress, ductility, and average work hardening were monitored with temperature. In the present work, emphasis was given on the study of serrated yielding in the service exposed Alloy 625. Detail investigations were made to study the effect of microstructure on the underlying mechanism of dynamic strain aging of the material. The study revealed that both the normal and the inverse Portevin-Le Chatelier effect (PLC) occured in the material at lower and higher temperature regime, respectively. While the normal PLC dynamics was associated with locking of dislocations by interstitial carbon atoms, the inverse one was accomplished by the dislocation pinning by substitutional Mo atoms. Further analyses identified that the basic deformation mechanism was different in middle and bottom samples as that in the top samples which was reflected in the difference in their respective activation energy and stress drop magnitude.

  18. Influence of aging temperature on the structure and mechanical properties of titanium alloy VT22 subjected to helical rolling

    NASA Astrophysics Data System (ADS)

    Mishin, I. P.; Naydenkin, E. V.; Ratochka, I. V.; Lykova, O. N.; Balushkina, M. A.

    2015-10-01

    The structure and mechanical properties of titanium alloy VT22 after helical rolling and subsequent aging was investigated. It is shown that the treatment leads to the formation of ultra-fine grain/subgrain structure in the alloy. The subsequent aging increases the ultimate strength and yield strength to 1640 and 1590 MPa respectively, while saving satisfactory plasticity (δ > 5%).

  19. Oral sapropterin acutely augments reflex vasodilation in aged human skin through nitric oxide-dependent mechanisms.

    PubMed

    Stanhewicz, Anna E; Alexander, Lacy M; Kenney, W Larry

    2013-10-01

    Functional constitutive nitric oxide synthase (NOS) and its cofactor tetrahydrobiopterin (BH4) are required for full reflex cutaneous vasodilation and are attenuated in primary aging. Acute, locally administered BH4 increases reflex vasodilation through NO-dependent mechanisms in aged skin. We hypothesized that oral sapropterin (Kuvan, shelf-stable pharmaceutical formulation of BH4) would augment reflex vasodilation in aged human skin during hyperthermia. Nine healthy human subjects (76 ± 1 yr) ingested sapropterin (10 mg/kg) or placebo in a randomized double-blind crossover design. Venous blood samples were collected prior to, and 3 h following, ingestion of sapropterin for measurement of plasma BH4. Three intradermal microdialysis fibers were placed in the forearm skin for local delivery of 1) lactated Ringer's solution, 2) 10 mM BH4, and 3) 20 mM N(G)-nitro-l-arginine methyl ester (l-NAME) to inhibit NOS. Red cell flux was measured at each site by laser-Doppler flowmetry (LDF) as reflex vasodilation was induced using a water-perfused suit. At 1°C rise in oral temperature, mean body temperature was clamped and 20 mM l-NAME was perfused at each site. Cutaneous vascular conductance was calculated (CVC = LDF/MAP) and expressed as a percentage of maximum (%CVCmax 28 mM sodium nitroprusside and local heat 43°C). Plasma concentrations of BH4 were significantly elevated 3 h after ingestion of sapropterin (0 h: 19.1 ± 2 pmol/ml vs. 3 h: 43.8 ± 3 pmol/ml; P < 0.001). Sapropterin increased NO-dependent vasodilation at control site (placebo: 14 ± 1 %CVCmax vs. sapropterin: 25 ± 4 %CVCmax; P = 0.004). Local BH4 administration increased NO-dependent vasodilation compared with control in placebo trials only (control: 14 ± 1 %CVCmax vs. BH4-treated: 24 ± 3 %CVCmax; P = 0.02). These data suggest oral sapropterin increases bioavailable BH4 in aged skin microvasculature sufficiently to increase NO synthesis through NOS and that sapropterin may be a viable intervention to

  20. Glycation-altered proteolysis as a pathobiologic mechanism that links dietary glycemic index, aging, and age-related disease (in nondiabetics).

    PubMed

    Uchiki, Tomoaki; Weikel, Karen A; Jiao, Wangwang; Shang, Fu; Caceres, Andrea; Pawlak, Dorota; Handa, James T; Brownlee, Michael; Nagaraj, Ram; Taylor, Allen

    2012-02-01

    Epidemiologic studies indicate that the risks for major age-related debilities including coronary heart disease, diabetes, and age-related macular degeneration (AMD) are diminished in people who consume lower glycemic index (GI) diets, but lack of a unifying physiobiochemical mechanism that explains the salutary effect is a barrier to implementing dietary practices that capture the benefits of consuming lower GI diets. We established a simple murine model of age-related retinal lesions that precede AMD (hereafter called AMD-like lesions). We found that consuming a higher GI diet promotes these AMD-like lesions. However, mice that consumed the lower vs. higher GI diet had significantly reduced frequency (P < 0.02) and severity (P < 0.05) of hallmark age-related retinal lesions such as basal deposits. Consuming higher GI diets was associated with > 3 fold higher accumulation of advanced glycation end products (AGEs) in retina, lens, liver, and brain in the age-matched mice, suggesting that higher GI diets induce systemic glycative stress that is etiologic for lesions. Data from live cell and cell-free systems show that the ubiquitin-proteasome system (UPS) and lysosome/autophagy pathway [lysosomal proteolytic system (LPS)] are involved in the degradation of AGEs. Glycatively modified substrates were degraded significantly slower than unmodified substrates by the UPS. Compounding the detriments of glycative stress, AGE modification of ubiquitin and ubiquitin-conjugating enzymes impaired UPS activities. Furthermore, ubiquitin conjugates and AGEs accumulate and are found in lysosomes when cells are glycatively stressed or the UPS or LPS/autophagy are inhibited, indicating that the UPS and LPS interact with one another to degrade AGEs. Together, these data explain why AGEs accumulate as glycative stress increases. PMID:21967227

  1. Molecular mechanisms of subretinal fibrosis in age-related macular degeneration.

    PubMed

    Ishikawa, Keijiro; Kannan, Ram; Hinton, David R

    2016-01-01

    Subretinal fibrosis is a result of a wound healing response that follows choroidal neovascularization in neovascular age-related macular degeneration (nAMD). Although anti-vascular endothelial growth factor therapy has become a standard treatment that improves visual acuity in many nAMD patients, unsuccessful treatment outcomes have often been attributed to the progression of subretinal fibrosis. In this review, we summarize the cellular and extracellular components of subretinal fibrous membranes and also discuss the possible molecular mechanisms including the functional involvement of growth factors and the inflammatory response in the process. Moreover, we present an murine animal model of subretinal fibrosis that might facilitate greater understanding of the pathophysiology and the development of novel therapeutic strategies for the inhibition of subretinal fibrosis in nAMD.

  2. Walter Benjamin in the Age of Digital Reproduction: Aura in Education--A Rereading of "The Work of Art in the Age of Mechanical Reproduction"

    ERIC Educational Resources Information Center

    Peim, Nick

    2007-01-01

    This paper considers a key text in the field of Cultural Studies for its relevance to questions about the identity of knowledge in education. The concept of "aura" arises as being of special significance in "The Work of Art in the Age of Mechanical Reproduction" as a way of understanding the change that occurs to art when mass reproduction becomes…

  3. Terrestrial ages, pairing, and concentration mechanism of Antarctic chondrites from Frontier Mountain, Northern Victoria Land

    NASA Astrophysics Data System (ADS)

    Welten, K. C.; Nishiizumi, K.; Caffee, M. W.; Hillegonds, D. J.; Johnson, J. A.; Jull, A. J. T.; Wieler, R.; Folco, L.

    We report concentrations of cosmogenic 10Be, 26Al, 36Cl, and 41Ca in the metal phase of 26 ordinary chondrites from Frontier Mountain (FRO), Antarctica, as well as cosmogenic 14C in eight and noble gases in four bulk samples. Thirteen out of 14 selected H chondrites belong to two previously identified pairing groups, FRO 90001 and FRO 90174, with terrestrial ages of ˜40 and ˜100 kyr, respectively. The FRO 90174 shower is a heterogeneous H3-6 chondrite breccia that probably includes more than 300 individual fragments, explaining the high H/L chondrite ratio (3.8) at Frontier Mountain. The geographic distribution of 19 fragments of this shower constrains ice fluctuations over the past 50-100 kyr to less than ˜40 m, supporting the stability of the meteorite trap over the last glacial cycle. The second H-chondrite pairing group, FRO 90001, is much smaller and its geographic distribution is mainly controlled by wind-transport. Most L-chondrites are younger than 50 kyr, except for the FRO 93009/01172 pair, which has a terrestrial age of ˜500 kyr. These two old L chondrites represent the only surviving members of a large shower with a similar preatmospheric radius (˜80 cm) as the FRO 90174 shower. The find locations of these two paired L-chondrite fragments on opposite sides of Frontier Mountain confirm the general glaciological model in which the two ice flows passing both ends of the mountain are derived from the same source area on the plateau. The 50 FRO meteorites analyzed so far represent 21 different falls. The terrestrial ages range from 6 kyr to 500 kyr, supporting the earlier proposed concentration mechanism.

  4. Long-term aging of cast stainless steels: Mechanisms and resulting properties

    SciTech Connect

    Chopra, O.K.; Chung, H.M.

    1987-09-01

    Mechanical property data are presented from Charpy-impact, tensile, and J-R curve tests for several heats of cast stainless steel aged up to 10,000 h at 450, 400, 350, 320, and 290/sup 0/C. The results indicate that thermal aging increases the tensile strength and decreases the impactenergy, J/sub IC/ and tearing modulus of the steels. Also, the ductile-to-brittle transition curve shifts to higher temperatures. The low-carbon CF-3 steels were the most resistant and the molybdenum-containing high-carbon CF-8M steels were the most susceptible to low-temperature embrittlement. The influence of nitrogen content and distribution of ferrite on loss of toughness are discussed. Data also indicate that existing correlations do not accurately represent the embrittlement behavior over the temperature range 280 to 450/sup 0/C, i.e., extrapolation of high-temperature data to reactor temperatures may not be valid for some compositions of cast stainless steels. 13 refs., 13 figs., 2 tabs.

  5. Influence of Thrombus Age on the Mechanical Thrombectomy Efficacy of the Amplatz Thrombectomy Device In Vitro

    SciTech Connect

    Grimm, Jan Jahnke, Thomas; Muhle, Claus; Heller, Martin; Mueller-Huelsbeck, Stefan

    2003-06-15

    Purpose: To determine the efficacy of thrombectomy for the Amplatz Thrombectomy Device (ATD) according to the age of the thrombus. Methods: Thrombectomy was performed with the 7 Fr or 8 Fr ATD. Five-day-old or 8-day-old thrombi were made from porcine blood by clotting within silicone tubes to be used in a flow model. Emboli sizes, weight, remaining thrombus and activation time were evaluated. Results: The age of the thrombus had no influence on the activation time necessary for complete thrombolysis. A significant difference was found in the overall amount of embolization only with the 7 Fr device although a similar trend was shown with the 8 Fr device. The amount of embolized thrombotic material was higher for both devices if older thrombi (i.e., 8 days old) we reprocessed. The overall impression was that the 8 Fr device showed slightly better results (less remaining thrombus and embolization). Conclusion: A tendency toward higher amounts of embolization was observed if older thrombi were used in the model. Therefore the interventional radiologist should be aware of the potentially higher risk of peripheral embolization when performing mechanical thrombectomy(with the ATD) in older thrombotic occlusions, especially since the higher rate of embolization was mainly due to an increased proportion of larger embolic particles (1 mm), which are clinically more significant.

  6. The impact of executive capacity and age on mechanisms underlying multidimensional feature selection

    PubMed Central

    Mott, Katherine K.; Alperin, Brittany R.; Fox, Anne M.; Holcomb, Phillip J.; Daffner, Kirk R.

    2015-01-01

    This study examined the role of executive capacity (EC) and aging in multidimensional feature selection. ERPs were recorded from healthy young and old adults of either high or average EC based on neuropsychological testing. Participants completed a color selective attention task in which they responded to target letter-forms in a specified color (attend condition) while ignoring letter-forms in a different color (ignore condition). Two selection negativity (SN) components were computed: the SNColor (attend – ignore), indexing early color selection, and the SNLetter (targets – standards), indexing early letter-form selection. High EC subjects exhibited self-terminating feature selection; the processing of one feature type was reduced if information from the other feature type suggested the stimulus did not contain the task-relevant feature. In contrast, average EC subjects exhaustively selected all features of a stimulus. The self-terminating approach was associated with better task accuracy. Higher EC was also linked to stronger early selection of target letter-forms, but did not modulate the seemingly less demanding task of color selection. Mechanisms utilized for multidimensional feature selection appear to be consistent across the lifespan, although there was age-related slowing of processing speed for early selection of letter features. We conclude that EC is a critical determinant of how multidimensional feature processing is carried out. PMID:25660207

  7. Mechanical properties of the rat colon: the effect of age, sex and different conditions of storage.

    PubMed

    Watters, D A; Smith, A N; Eastwood, M A; Anderson, K C; Elton, R A

    1985-01-01

    The mechanical properties of the rat colon were studied in old and young Sprague-Dawley rats which were also grouped by sex. Different storage media were used. Rings of colonic tissue were submitted to pulls on an Instron 1026 tensiometer. Gender did not affect the properties of the young rat colon. The rat colon has a tensile strength of around 50 g/mm2 (which places it between the dog and the cat). It increased in strength from proximal to distal, though the rectum was weaker than the colon. The pre-strain of the rat colon was 10% and it was capable of stretching to 200% of its original dimensions. The strength and ability to stretch fell with age, although it initially increased, in the first year of life. Physiological saline at 4 degrees C preserved the burst strength, percentage elongation, hysteresis and Young's modulus between 25 and 100 g stress for up to 1 week. Young's modulus between 125 and 200 g fell progressively with each day of storage. Stress relaxation rose in the first 24 h and thereafter remained constant. Salt appeared to be a good long-term storage medium. Irradiation of the colons before storage did not affect the mechanical properties.

  8. Degradation mechanisms of cable insulation materials during radiation-thermal ageing in radiation environment

    NASA Astrophysics Data System (ADS)

    Seguchi, Tadao; Tamura, Kiyotoshi; Ohshima, Takeshi; Shimada, Akihiko; Kudoh, Hisaaki

    2011-02-01

    Radiation and thermal degradation of ethylene-propylene rubber (EPR) and crosslinked polyethylene (XLPE) as cable insulation materials were investigated by evaluating tensile properties, gel-fraction, and swelling ratio, as well as by the infrared (FTIR) analysis. The activation energy of thermal oxidative degradation changed over the range 100-120 °C for both EPR and XLPE. This may be attributed to the fact that the content of an antioxidant used as the stabilizer for polymers decreases by evaporation during thermal ageing at high temperatures. The analysis of antioxidant content and oxidative products in XLPE as a model sample showed that a small amount of antioxidant significantly reduced the extent of thermal oxidation, but was not effective for radiation induced oxidation. The changes in mechanical properties were well reflected by the degree of oxidation. A new model of polymer degradation mechanisms was proposed where the degradation does not take place by chain reaction via peroxy radical and hydro-peroxide. The role of the antioxidant in the polymer is the reduction of free radical formation in the initiation step in thermal oxidation, and it could not stop radical reactions for either radiation or thermal oxidation.

  9. Age-related transparent root dentin: mineral concentration, crystallite size, and mechanical properties.

    PubMed

    Kinney, J H; Nalla, R K; Pople, J A; Breunig, T M; Ritchie, R O

    2005-06-01

    Many fractures occur in teeth that have been altered, for example restored or endodontically repaired. It is therefore essential to evaluate the structure and mechanical properties of these altered dentins. One such altered form of dentin is transparent (sometimes called sclerotic) dentin, which forms gradually with aging. The present study focuses on differences in the structure and mechanical properties of normal versus transparent dentin. The mineral concentration, as measured by X-ray computed microtomography, was significantly higher in transparent dentin, the elevated concentration being consistent with the closure of the tubule lumens. Crystallite size, as measured by small angle X-ray scattering, was slightly smaller in transparent dentin, although the importance of this finding requires further study. The elastic properties were unchanged by transparency; however, transparent dentin, unlike normal dentin, exhibited almost no yielding before failure. In addition, the fracture toughness was lowered by roughly 20% while the fatigue lifetime was deleteriously affected at high stress levels. These results are discussed in terms of the altered microstructure of transparent dentin.

  10. Microstructure and mechanical properties of composite resins subjected to accelerated artificial aging.

    PubMed

    dos Reis, Andréa Cândido; de Castro, Denise Tornavoi; Schiavon, Marco Antônio; da Silva, Leandro Jardel; Agnelli, José Augusto Marcondes

    2013-01-01

    The aim of this study was to investigate the influence of accelerated artificial aging (AAA) on the microstructure and mechanical properties of the Filtek Z250, Filtek Supreme, 4 Seasons, Herculite, P60, Tetric Ceram, Charisma and Filtek Z100. composite resins. The composites were characterized by Fourier-transform Infrared spectroscopy (FTIR) and thermal analyses (Differential Scanning Calorimetry - DSC and Thermogravimetry - TG). The microstructure of the materials was examined by scanning electron microscopy. Surface hardness and compressive strength data of the resins were recorded and the mean values were analyzed statistically by ANOVA and Tukey's test (α=0.05). The results showed significant differences among the commercial brands for surface hardness (F=86.74, p<0.0001) and compressive strength (F=40.31, p<0.0001), but AAA did not affect the properties (surface hardness: F=0.39, p=0.53; compressive strength: F=2.82, p=0.09) of any of the composite resins. FTIR, DSC and TG analyses showed that resin polymerization was complete, and there were no differences between the spectra and thermal curve profiles of the materials obtained before and after AAA. TG confirmed the absence of volatile compounds and evidenced good thermal stability up to 200 °C, and similar amounts of residues were found in all resins evaluated before and after AAA. The AAA treatment did not significantly affect resin surface. Therefore, regardless of the resin brand, AAA did not influence the microstructure or the mechanical properties.

  11. Mechanism of antioxidant interaction on polymer oxidation by thermal and radiation ageing

    NASA Astrophysics Data System (ADS)

    Seguchi, Tadao; Tamura, Kiyotoshi; Shimada, Akihiko; Sugimoto, Masaki; Kudoh, Hisaaki

    2012-11-01

    The mechanism of polymer oxidation by radiation and thermal ageing was investigated for the life evaluation of cables installed in radiation environments. The antioxidant as a stabilizer was very effective for thermal oxidation with a small content in polymers, but was not effective for radiation oxidation. The ionizing radiation induced the oxidation to result in chain scission even at low temperature, because the free radicals were produced and the antioxidant could not stop the oxidation of radicals with the chain scission. A new mechanism of antioxidant effect for polymer oxidation was proposed. The effect of antioxidant was not the termination of free radicals in polymer chains such as peroxy radicals, but was the depression of initial radical formation in polymer chains by thermal activation. The antioxidant molecule was assumed to delocalize the activated energy in polymer chains by the Boltzmann statics (distribution) to result in decrease in the probability of radical formation at a given temperature. The interaction distance (delocalization volume) by one antioxidant molecule was estimated to be 5-10 nm by the radius of sphere in polymer matrix, though the value would depend on the chemical structure of antioxidant.

  12. Estimation of mechanical properties of cast stainless steels during thermal aging in LWR systems

    SciTech Connect

    Chopra, O.K.

    1991-10-01

    A procedure and correlations are presented for predicting Charpy- impact energy, tensile flow stress, fracture toughness J-R curve, and J{sub IC} of aged cast stainless steels from known material information. The ``saturation`` impact strength and fracture toughness of a specific cast stainless steel, i.e., the minimum value that would be achieved for the material after long-term service, is estimated from the chemical composition of the steel. Mechanical properties as a function of time and temperature of reactor service are estimated from impact energy and flow stress of the unaged material and the kinetics of embrittlement, which are also determined from chemical composition. The J{sub IC} values are determined from the estimated J-R curve and flow stress. Examples of estimating mechanical properties of cast stainless steel components during reactor service are presented. A common ``lower-bound`` J-R curve for cast stainless steels of unknown chemical composition is also defined for a given grade of steel, ferrite content, and temperature.

  13. A Mechanism For Solar Forcing of Climate: Did the Maunder Minimum Cause the Little Ice Age?

    NASA Technical Reports Server (NTRS)

    Yung, Yuk L.

    2004-01-01

    The mechanism we wish to demonstrate exploits chemical, radiative, and dynamical sensitivities in the stratosphere to affect the climate of the troposphere. The sun, while its variability in total radiative output over the course of the solar cycle is on the order of 0.1%, exhibits variability in the UV output on the order of 5%. We expect to show that a substantially decreased solar UV output lessened the heating of the Earth's stratosphere during the Maunder Minimum, through decreased radiative absorption by ozone and oxygen. These changes in stratospheric heating would lead to major changes in the stratospheric zonal wind pattern which would in turn affect the propagation characteristics of planetary-scale waves launched in the winter hemisphere. Until recently, there was no quantitative data to relate the changes in the stratosphere to those at the surface. There is now empirical evidence from the NCEP Reanalysis data that a definitive effect of the solar cycle on climate in the troposphere exists. Our recent work is summarized as follows (see complete list of publications in later part of this report).

  14. Expectation and conditioning

    NASA Astrophysics Data System (ADS)

    Coster, Adelle C. F.; Alstrøm, Preben

    2001-02-01

    We present a dynamical model that embodies both classical and instrumental conditioning paradigms in the same framework. The model is based on the formation of expectations of stimuli and of rewards. The expectations of stimuli are formed in a recurrent process called expectation learning in which one activity pattern evokes another. The expectation of rewards or punishments (motivation) is modelled using reinforcement learning.

  15. Effect of age on mechanical properties of the collagen phase in different orientations of human cortical bone.

    PubMed

    Leng, Huijie; Reyes, Michael J; Dong, Xuanliang N; Wang, Xiaodu

    2013-08-01

    The collagen phase plays an important role in mechanical behaviors of cortical bone. However, aging effects on the mechanical behavior of the collagen phase is still poorly understood. In this study, micro-tensile tests were performed on demineralized human cortical bone samples from young, middle-aged, and elderly donors and aging effects on the mechanical properties of the collagen phase in different orientations (i.e. longitudinal and transverse directions of bone) were examined. The results of this study indicated that the elastic modulus and ultimate strength of the demineralized bone specimens decreased with aging in both the longitudinal and transverse orientations. However, the failure strain exhibited no significant changes in both orientations regardless of aging. These results suggest that the stiffness and strength of the collagen phase in bone are deteriorated with aging in both longitudinal and transverse directions. However, the aging effect is not reflected in the failure strain of the collagen phase in both longitudinal and transverse orientations, implying that the maximum sustainable deformation of the collagen phase is independent of aging and orientation.

  16. Education: Expectation and the Unexpected

    ERIC Educational Resources Information Center

    Fulford, Amanda

    2016-01-01

    This paper considers concepts of expectation and responsibility, and how these drive dialogic interactions between tutor and student in an age of marketised Higher Education. In thinking about such interactions in terms of different forms of exchange, the paper considers the philosophy of Martin Buber and Emmanuel Levinas on dialogic…

  17. Microstructures, aging behaviour and mechanical properties in hydrogen and chloride media of backward extruded Mg-Y based biomaterials.

    PubMed

    Peng, Qiuming; Ma, Ning; Fang, Daqing; Li, Hui; Liu, Riping; Tian, Yongjun

    2013-01-01

    Microstructures, aging behaviour from room temperature to 300 °C and mechanical properties in different media of backward extruded (BE) Mg-Y based biomaterial have been investigated. The results reveal that BE-Mg-Y based alloy is mainly composed of polygon-shaped grains and fine precipitates. The results of aging response show that BE-Mg-Y based alloy exhibits remarkable age hardening behaviour when the aging temperature is 200 °C and higher. The high mechanical properties of aged BE-Mg-Y based alloy are mostly associated with fine microstructure, solid solution strengthening and the existence of homogeneous precipitates. The hydrogen embrittlement dependence on the aging time is confirmed in BE-Mg-Y based alloy. Additionally, the strength and elongation of BE-Mg-Y based alloy are significantly influenced by the ion concentration in media. These results offer some implications for understanding the reduced strength of Mg based implants in body environment. It is demonstrated that the temporary high mechanical strength in air of BE-Mg-Y based biomaterials is insufficient to evaluate the in vivo mechanical integrity.

  18. Neural mechanisms of verb argument structure processing in agrammatic aphasic and healthy age-matched listeners

    PubMed Central

    Thompson, C.K.; Bonakdarpour, B.; Fix, S.F.

    2010-01-01

    Processing of lexical verbs involves automatic access to argument structure entries entailed within the verb's representation. Recent neuroimaging studies with young normal listeners suggest that this involves bilateral posterior perisylvian tissue, with graded activation in these regions based on argument structure complexity. The aim of the present study was to examine the neural mechanisms of verb processing using functional magnetic resonance imaging (fMRI) in older normal volunteers and patients with stroke-induced agrammatic aphasia, a syndrome in which verb, as compared to noun, production often is selectively impaired, but verb comprehension in both on-line and off-line tasks is spared. Fourteen healthy listeners and five age-matched aphasic patients performed a lexical decision task, which examined verb processing by argument structure complexity, i.e., one-argument (i.e., intransitive (v1)); two-argument (i.e., transitive (v2)), and three-argument (v3) verbs. Results for the age-matched listeners largely replicated those for younger participants studied by Thompson et al. (2007): v3-v1 comparisons showed activation of the angular gyrus in both hemispheres and this same heteromodal region was activated in the left hemisphere in the (v2+v3)-v1 contrast. Similar results were derived for the agrammatic aphasic patients, however, activation was unilateral (in the right hemisphere for 3 participants) rather than bilateral likely because these patients' lesions extended to the left temporoparietal region. All performed the task with high accuracy and, despite differences in lesion site and extent, they recruited spared tissue in the same regions as healthy normals. Consistent with psycholinguistic models of sentence processing, these findings indicate that the posterior language network is engaged for processing verb argument structure and is crucial for semantic integration of argument structure information. PMID:19702460

  19. Mechanisms Underlying Age- and Performance-related Differences in Working Memory

    PubMed Central

    Daffner, Kirk R.; Chong, Hyemi; Sun, Xue; Tarbi, Elise C.; Riis, Jenna L.; McGinnis, Scott M.; Holcomb, Phillip J.

    2011-01-01

    This study took advantage of the subsecond temporal resolution of ERPs to investigate mechanisms underlying age- and performance-related differences in working memory. Young and old subjects participated in a verbal n-back task with three levels of difficulty. Each group was divided into high and low performers based on accuracy under the 2-back condition. Both old subjects and low-performing young subjects exhibited impairments in preliminary mismatch/match detection operations (indexed by the anterior N2 component). This may have undermined the quality of information available for the subsequent decision-making process (indexed by the P3 component), necessitating the appropriation of more resources. Additional anterior and right hemisphere activity was recruited by old subjects. Neural efficiency and the capacity to allocate more resources to decision-making differed between high and low performers in both age groups. Under low demand conditions, high performers executed the task utilizing fewer resources than low performers (indexed by the P3 amplitude). As task requirements increased, high-performing young and old subjects were able to appropriate additional resources to decision-making, whereas their low-performing counterparts allocated fewer resources. Higher task demands increased utilization of processing capacity for operations other than decision-making (e.g., sustained attention) that depend upon a shared pool of limited resources. As demands increased, all groups allocated additional resources to the process of sustaining attention (indexed by the posterior slow wave). Demands appeared to have exceeded capacity in low performers, leading to a reduction of resources available to the decision-making process, which likely contributed to a decline in performance. PMID:20617886

  20. Mitochondrial protection and anti-aging activity of Astragalus polysaccharides and their potential mechanism.

    PubMed

    Li, Xing-Tai; Zhang, Ya-Kui; Kuang, Hai-Xue; Jin, Feng-Xin; Liu, De-Wen; Gao, Ming-Bo; Liu, Ze; Xin, Xiao-Juan

    2012-01-01

    The current study was performed to investigate mitochondrial protection and anti-aging activity of Astragalus polysaccharides (APS) and the potential underlying mechanism. Lipid peroxidation of liver and brain mitochondria was induced by Fe(2+)-Vit C in vitro. Thiobarbituric acid (TBA) colorimetry was used to measure the content of thiobarbituric acid reactive substances (TBARS). Mouse liver mitochondrial permeability transition (PT) was induced by calcium overload in vitro and spectrophotometry was used to measure it. The scavenging activities of APS on superoxide anion (O(2) (•-)) and hydroxyl radical (•OH), which were produced by reduced nicotinamide adenine dinucleotide (NADH)-N-Methylphenazonium methyl sulfate (PMS) and hydrogen peroxide (H(2)O(2))-Fe(2+) system respectively, were measured by 4-nitrobluetetrazolium chloride (NBT) reduction and Fenton reaction colorimetry respectively. The Na(2)S(2)O(3) titration method was used to measure the scavenging activities of APS on H(2)O(2). APS could inhibit TBARS production, protect mitochondria from PT, and scavenge O(2) (•-), •OH and H(2)O(2) significantly in a concentration-dependent manner respectively. The back of the neck of mice was injected subcutaneously with D-galactose to induce aging at a dose of 100 mg/kg/d for seven weeks. Moreover, the activities of catalase (CAT), surperoxide dismutase (SOD) and glutathione peroxidase (GPx) and anti-hydroxyl radical which were assayed by using commercial monitoring kits were increased significantly in vivo by APS. According to this research, APS protects mitochondria by scavenging reactive oxygen species (ROS), inhibiting mitochondrial PT and increasing the activities of antioxidases. Therefore, APS has the effect of promoting health. PMID:22408421

  1. El Dorado and the fountain of aging: what mechanisms matter how much?

    NASA Astrophysics Data System (ADS)

    Donahue, N. M.

    2011-12-01

    Organics get old because they have to; the atmosphere is not a very friendly place if you are reduced. So they increase. Not long ago, models thought organic aerosol was too reduced: they did not make enough aerosol, and they did not oxidize it enough. Model aerosol was, quiet literally, too young. Consequently, the community has busily sought to make it grow up and even die. Many, many aging mechanisms have been pursued, some of which make more aerosol, some of which make older (more oxidized) aerosol, and some of which do both. We and others have focused on aging by gas-phase hydroxyl radical (OH) reacting both homogeneously with gas-phase organics and heterogeneously with condensed-phase organics. Aqueous-phase chemistry convincingly oxidizes organics and can both increase and decrease OA levels. Condensed-phase photolysis may play a role. The prediction here is that the search for new OA sources will soon transform into a search for new OA sinks (as originally proposed for heterogeneous surface oxidation of self-assembled organic monolayers), and that this is entirely sensible. OA should be viewed as a meta-stable chemical intermediate form of some ambient organics, kept stable in large part by a longer lifetime due to diffusion limitations for heterogeneous OH uptake compared to homogeneous OH oxidation of similar organics in the gas phase. Viewed against the timescale of aerosol deposition (roughly 1 week), many of these processes certainly do have time to play an important role in the atmosphere. Sorting out just what role is played by each is a long task, but the community has made great progress in recent years. Here we shall frame that progress and look forward to consider the next steps.

  2. Mitochondrial Protection and Anti-aging Activity of Astragalus Polysaccharides and Their Potential Mechanism

    PubMed Central

    Li, Xing-Tai; Zhang, Ya-Kui; Kuang, Hai-Xue; Jin, Feng-Xin; Liu, De-Wen; Gao, Ming-Bo; Liu, Ze; Xin, Xiao-Juan

    2012-01-01

    The current study was performed to investigate mitochondrial protection and anti-aging activity of Astragalus polysaccharides (APS) and the potential underlying mechanism. Lipid peroxidation of liver and brain mitochondria was induced by Fe2+–Vit C in vitro. Thiobarbituric acid (TBA) colorimetry was used to measure the content of thiobarbituric acid reactive substances (TBARS). Mouse liver mitochondrial permeability transition (PT) was induced by calcium overload in vitro and spectrophotometry was used to measure it. The scavenging activities of APS on superoxide anion (O2•−) and hydroxyl radical (•OH), which were produced by reduced nicotinamide adenine dinucleotide (NADH)—N-Methylphenazonium methyl sulfate (PMS) and hydrogen peroxide (H2O2)–Fe2+ system respectively, were measured by 4-nitrobluetetrazolium chloride (NBT) reduction and Fenton reaction colorimetry respectively. The Na2S2O3 titration method was used to measure the scavenging activities of APS on H2O2. APS could inhibit TBARS production, protect mitochondria from PT, and scavenge O2•−, •OH and H2O2 significantly in a concentration-dependent manner respectively. The back of the neck of mice was injected subcutaneously with D-galactose to induce aging at a dose of 100 mg/kg/d for seven weeks. Moreover, the activities of catalase (CAT), surperoxide dismutase (SOD) and glutathione peroxidase (GPx) and anti-hydroxyl radical which were assayed by using commercial monitoring kits were increased significantly in vivo by APS. According to this research, APS protects mitochondria by scavenging reactive oxygen species (ROS), inhibiting mitochondrial PT and increasing the activities of antioxidases. Therefore, APS has the effect of promoting health. PMID:22408421

  3. Temporal expectancy modulates phasic alerting in both detection and discrimination tasks.

    PubMed

    Lu, Shena; Wang, Wei; Cai, Yongchun

    2015-02-01

    The aim of the present study was to investigate whether phasic alerting might be modulated by temporal expectancy and to determine the processing stages at which this modulation might occur. We manipulated participants' expectancy for the target appearance by systematically varying the cue-target stimulus onset asynchrony (SOA) distribution in both detection and discrimination tasks. There were three temporal expectancy conditions: the non-aging condition in which temporal expectancy was eliminated, the aging condition in which temporal expectancy increased as SOA increased, and the accelerated-aging condition in which temporal expectancy increased more dramatically as SOA increased than in the aging condition. We obtained the same pattern of results in both detection and discrimination tasks: the onset time of the alerting effect was postponed successively across the three temporal expectancy conditions. The present findings suggest that the time course of the alerting effect may be modulated by temporal expectancy, highlighting the importance of taking account into the influence of temporal expectancy in studies involving the time course of cognitive processes. Furthermore, since mechanisms underlying the detection and discrimination tasks may differ in early processing stages involving perceptual analysis and response selection, the same result pattern observed in both tasks is consistent with the hypothesis that the modulation of temporal expectancy on phasic alerting occurs at late processing stages involving motor preparation.

  4. Changes in mechanical properties of bone within the mandibular condyle with age.

    PubMed

    Huja, Sarandeep S; Rummel, Andrew M; Beck, Frank M

    2008-02-01

    The purpose of the study was to compare indentation modulus (IM) and hardness of condylar bone in young and adult dogs. In addition we desired to examine histologic sections for bone formation activity in the two groups. Mandibular condyles were obtained from adult (1- to 2-year-old) and young (approximately 5-m old) dogs. Two sections/condyle were obtained and one was processed for histomorphometry and the other for mechanical analyses. Indents were made on moist condylar trabecular bone to a depth of 500 nm at a loading rate of 10 nm/s using a custom-made hydration system to obtain IM and hardness. Histomorphometric analyses measured the bone volume/total volume (BV/TV%) and ratio of labeled to unlabeled bone within the condyle. Data were analyzed using a repeated-measures factorial analysis of variance and Tukey-Kramer method. Overall, the IM of the adult condyles (10.0+/-3.4 GPa, Mean+/-SD) were significantly (P<0.0001) higher than in young dogs (5.6+/-2.6 GPa). There was a greater bone mass in the young (60.2%) versus the adult condyles (42%). Also, significantly more labeled bone in the young (66.1%) condylar bone suggested higher bone forming activity than in adult condyles (27.5%). With age there is a change in mass and material properties in the trabecular bone of the mandibular condyle in dogs.

  5. Microscale Mechanism of Age Dependent Wetting Properties of Prickly Pear Cacti (Opuntia).

    PubMed

    Rykaczewski, Konrad; Jordan, Jacob S; Linder, Rubin; Woods, Erik T; Sun, Xiaoda; Kemme, Nicholas; Manning, Kenneth C; Cherry, Brian R; Yarger, Jeffery L; Majure, Lucas C

    2016-09-13

    Cacti thrive in xeric environments through specialized water storage and collection tactics such as a shallow, widespread root system that maximizes rainwater absorption and spines adapted for fog droplet collection. However, in many cacti, the epidermis, not the spines, dominates the exterior surface area. Yet, little attention has been dedicated to studying interactions of the cactus epidermis with water drops. Surprisingly, the epidermis of plants in the genus Opuntia, also known as prickly pear cacti, has water-repelling characteristics. In this work, we report that surface properties of cladodes of 25 taxa of Opuntia grown in an arid Sonoran climate switch from water-repelling to superwetting under water impact over the span of a single season. We show that the old cladode surfaces are not superhydrophilic, but have nearly vanishing receding contact angle. We study water drop interactions with, as well as nano/microscale topology and chemistry of, the new and old cladodes of two Opuntia species and use this information to uncover the microscopic mechanism underlying this phenomenon. We demonstrate that composition of extracted wax and its contact angle do not change significantly with time. Instead, we show that the reported age dependent wetting behavior primarily stems from pinning of the receding contact line along multilayer surface microcracks in the epicuticular wax that expose the underlying highly hydrophilic layers.

  6. Microscale Mechanism of Age Dependent Wetting Properties of Prickly Pear Cacti (Opuntia).

    PubMed

    Rykaczewski, Konrad; Jordan, Jacob S; Linder, Rubin; Woods, Erik T; Sun, Xiaoda; Kemme, Nicholas; Manning, Kenneth C; Cherry, Brian R; Yarger, Jeffery L; Majure, Lucas C

    2016-09-13

    Cacti thrive in xeric environments through specialized water storage and collection tactics such as a shallow, widespread root system that maximizes rainwater absorption and spines adapted for fog droplet collection. However, in many cacti, the epidermis, not the spines, dominates the exterior surface area. Yet, little attention has been dedicated to studying interactions of the cactus epidermis with water drops. Surprisingly, the epidermis of plants in the genus Opuntia, also known as prickly pear cacti, has water-repelling characteristics. In this work, we report that surface properties of cladodes of 25 taxa of Opuntia grown in an arid Sonoran climate switch from water-repelling to superwetting under water impact over the span of a single season. We show that the old cladode surfaces are not superhydrophilic, but have nearly vanishing receding contact angle. We study water drop interactions with, as well as nano/microscale topology and chemistry of, the new and old cladodes of two Opuntia species and use this information to uncover the microscopic mechanism underlying this phenomenon. We demonstrate that composition of extracted wax and its contact angle do not change significantly with time. Instead, we show that the reported age dependent wetting behavior primarily stems from pinning of the receding contact line along multilayer surface microcracks in the epicuticular wax that expose the underlying highly hydrophilic layers. PMID:27537082

  7. Degradation mechanism of LiCoO2/mesocarbon microbeads battery based on accelerated aging tests

    NASA Astrophysics Data System (ADS)

    Guan, Ting; Zuo, Pengjian; Sun, Shun; Du, Chunyu; Zhang, Lingling; Cui, Yingzhi; Yang, Lijie; Gao, Yunzhi; Yin, Geping; Wang, Fuping

    2014-12-01

    A series of LiCoO2/mesocarbon microbeads (MCMB) commercial cells cycled at different rates (0.6C, 1.2C, 1.5C, 1.8C, 2.4C and 3.0C) are disassembled and the capacity fade mechanism is proposed by analyzing the structure, morphology and electrochemical performance evolution at the capacity retention of 95%, 90%, 85%, 80%. The capacity deterioration of the commercial cell is mainly caused by the decay of the reversible capacity of LiCoO2 cathode, the irreversible loss of active lithium and the lithium remaining in anode. The proportions of effects by the above three factors are calculated accurately. The consumption of the active lithium leads to a cell imbalance between the anode and the cathode. The electrochemical test results indicate that the capacity fade of the active materials at the low rate is more obvious than that at the high rate. The influence of the active lithium is gradually increscent with the increasing rate. The rate of 1.5C is the optimal value to accelerate the aging of the full cell by comparing the testing results at different capacity retentions in the specific condition of low charge/discharge rate and shallow depth of discharge.

  8. Aging of whey protein films and the effect on mechanical and barrier properties.

    PubMed

    Anker, M; Stading, M; Hermansson, A M

    2001-02-01

    This work focuses on the aging of whey protein isolate (WPI) films plasticized with glycerol (G) and sorbitol (S). The films were cast from heated aqueous solutions at pH 7 and dried at 23 degrees C and 50% relative humidity (RH) for 16 h. They were stored in a climate room (23 degrees C, 50% RH) for 120 days, and the film properties were measured at regular intervals. The moisture content (MC) of the WPI/G films decreased from 22% (2 days) to 15% (45 days) and was thereafter constant at 15% (up to 120 days). This affected the mechanical properties and caused an increased stress at break (from 2.7 to 8.3 MPa), a decreased strain at break (from 33 to 4%), and an increased glass transition temperature (T(g)) (from -56 to -45 degrees C). The barrier properties were, however, unaffected, with constant water vapor permeability and a uniform film thickness. The MC of the WPI/S films was constant at approximately 9%, which gave no change in film properties.

  9. Mechanisms of Superoxide Signaling in Epigenetic Processes: Relation to Aging and Cancer

    PubMed Central

    Afanas’ev, Igor

    2015-01-01

    Superoxide is a precursor of many free radicals and reactive oxygen species (ROS) in biological systems. It has been shown that superoxide regulates major epigenetic processes of DNA methylation, histone methylation, and histone acetylation. We suggested that superoxide, being a radical anion and a strong nucleophile, could participate in DNA methylation and histone methylation and acetylation through mechanism of nucleophilic substitution and free radical abstraction. In nucleophilic reactions superoxide is able to neutralize positive charges of methyl donors S-adenosyl-L-methionine (SAM) and acetyl-coenzyme A (AcCoA) enhancing their nucleophilic capacity or to deprotonate cytosine. In the reversed free radical reactions of demethylation and deacetylation superoxide is formed catalytically by the (Tet) family of dioxygenates and converted into the iron form of hydroxyl radical with subsequent oxidation and final eradication of methyl substituents. Double role of superoxide in these epigenetic processes might be of importance for understanding of ROS effects under physiological and pathological conditions including cancer and aging. PMID:26029480

  10. Effect of Hygrothermal Aging on the Mechanical Properties of Fluorinated and Nonfluorinated Clay-Epoxy Nanocomposites

    PubMed Central

    Hamim, Salah U.; Singh, Raman P.

    2014-01-01

    Hydrophilic nature of epoxy polymers can lead to both reversible and irreversible/permanent changes in epoxy upon moisture absorption. The permanent changes leading to the degradation of mechanical properties due to combined effect of moisture and elevated temperature on EPON 862, Nanomer I.28E, and Somasif MAE clay-epoxy nanocomposites are investigated in this study. The extent of permanent degradation on fracture and flexural properties due to the hygrothermal aging is determined by drying the epoxy and their clay-epoxy nanocomposites after moisture absorption. Significant permanent damage is observed for fracture toughness and flexural modulus, while the extent of permanent damage is less significant for flexural strength. It is also observed that permanent degradation in Somasif MAE clay-epoxy nanocomposites is higher compared to Nanomer I.28E clay-epoxy nanocomposites. Fourier transform infrared (FTIR) spectroscopy revealed that both clays retained their original chemical structure after the absorption-desorption cycle without undergoing significant changes. Scanning electron microscopy (SEM) images of the fracture surfaces provide evidence that Somasif MAE clay particles offered very little resistance to crack propagation in case of redried specimens when compared to Nanomer I.28E counterpart. The reason for the observed higher extent of permanent degradation in Somasif MAE clay-epoxy system has been attributed to the weakening of the filler-matrix interface. PMID:27379285

  11. Brain mechanisms underlying the effects of aging on different aspects of selective attention.

    PubMed

    Geerligs, Linda; Saliasi, Emi; Maurits, Natasha M; Renken, Remco J; Lorist, Monicque M

    2014-05-01

    The ability to suppress irrelevant information declines with age, while the ability to enhance relevant information remains largely intact. We examined mechanisms behind this dissociation in an fMRI study, using a selective attention task in which relevant and irrelevant information appeared simultaneously. Slowing of response times due to distraction by irrelevant targets was larger in older than younger participants. Increased distraction was related to larger increases in activity and connectivity in areas of the dorsal attention network, indicating a more pronounced (re-)orientation of attention. The decreases in accuracy in target compared to nontarget trials were smaller in older compared to younger participants. In older adults we found increased recruitment of areas in the fronto-parietal control network (FPCN) during target detection. Moreover, older adults showed increased connectivity between the FPCN, supporting cognitive control, and somatomotor areas implicated in response selection and execution. This connectivity increase was related to improved target detection, suggesting that older adults engage additional cognitive control, which might enable the observed intact performance in detecting and responding to target stimuli.

  12. Accelerated aging studies of UHMWPE. I. Effect of resin, processing, and radiation environment on resistance to mechanical degradation.

    PubMed

    Edidin, A A; Herr, M P; Villarraga, M L; Muth, J; Yau, S S; Kurtz, S M

    2002-08-01

    The resin and processing route have been identified as potential variables influencing the mechanical behavior, and hence the clinical performance, of ultra-high molecular weight polyethylene (UHMWPE) orthopedic components. Researchers have reported that components fabricated from 1900 resin may oxidize to a lesser extent than components fabricated from GUR resin during shelf aging after gamma sterilization in air. Conflicting reports on the oxidation resistance for 1900 raise the question of whether resin or manufacturing method, or an interaction between resin and manufacturing method, influences the mechanical behavior of UHMWPE. We conducted a series of accelerated aging studies (no aging, aging in oxygen or in nitrogen) to systematically examine the influence of resin (GUR or 1900), manufacturing method (bulk compression molding or extrusion), and sterilization method (none, in air, or in nitrogen) on the mechanical behavior of UHMWPE. The small punch testing technique was used to evaluate the mechanical behavior of the materials, and Fourier transform infrared spectroscopy was used to characterize the oxidation in selected samples. Our study showed that the sterilization environment, aging condition, and specimen location (surface or subsurface) significantly affected the mechanical behavior of UHMWPE. Each of the three polyethylenes evaluated seem to degrade according to a similar pathway after artificial aging in oxygen and gamma irradiation in air. The initial ability of the materials to exhibit post-yield strain hardening was significantly compromised by degradation. In general, there were only minor differences in the aging behavior of molded and extruded GUR 1050, whereas the molded 1900 material seemed to degrade slightly faster than either of the 1050 materials.

  13. Client Expectations for Counseling

    ERIC Educational Resources Information Center

    Tinsley, Howard E. A.; Harris, Donna J.

    1976-01-01

    Undergraduate students (N=287) completed an 82-item questionnaire about their expectations of counseling. The respondents' strongest expectations were of seeing an experienced, genuine, expert, and accepting counselor they could trust. Expectancies that the counselor would be understanding and directive were lower. Significant sex differences were…

  14. Marijuana: College Students' Expectations.

    ERIC Educational Resources Information Center

    Rumstein, Regina

    College students' expectations regarding the physiological, psychological, and social effects of marijuana were investigated. A sample of 210 undergraduates stated their expectations about the effect of the drug by answering a series of structured-response type questions. Also, Ss provided background information related to their expectations about…

  15. The Power of Expectations

    ERIC Educational Resources Information Center

    Cross, Neal

    2008-01-01

    Principals want teachers to do more than profess high expectations for their students. Principals want teachers to have the knowledge and skills to realize their expectations for students by using strategies that increase students' attention to their achievement and responsibilities for learning. Current expectancy literature states that teachers…

  16. Expecting the Best

    ERIC Educational Resources Information Center

    DiPaula, John

    2010-01-01

    Educational expectations are psychological constructs that change over time and can be altered or influenced by various factors. The concept of educational expectations refers to how much schooling students realistically believe that they will complete. These expectations are eventually raised or lowered as students see others like themselves…

  17. Alzheimer's Disease as Subcellular `Cancer' --- The Scale-Invariant Principles Underlying the Mechanisms of Aging ---

    NASA Astrophysics Data System (ADS)

    Murase, M.

    1996-01-01

    with self-organization, has been thought to underlie `creative' aspects of biological phenomena such as the origin of life, adaptive evolution of viruses, immune recognition and brain function. It therefore must be surprising to find that the same principles will also underlie `non-creative' aspects, for example, the development of cancer and the aging of complex organisms. Although self-organization has extensively been studied in nonliving things such as chemical reactions and laser physics, it is undoubtedly true that the similar sources of the order are available to living things at different levels and scales. Several paradigm shifts are, however, required to realize how the general principles of natural selection can be extensible to non-DNA molecules which do not possess the intrinsic nature of self-reproduction. One of them is, from the traditional, genetic inheritance view that DNA (or RNA) molecules are the ultimate unit of heritable variations and natural selection at any organization level, to the epigenetic (nongenetic) inheritance view that any non-DNA molecule can be the target of heritable variations and molecular selection to accumulate in certain biochemical environment. Because they are all enriched with a β-sheet content, ready to mostly interact with one another, different denatured proteins like β-amyloid, PHF and prions can individually undergo self-templating or self-aggregating processes out of gene control. Other paradigm shifts requisite for a break-through in the etiology of neurodegenerative disorders will be discussed. As it is based on the scale-invariant principles, the present theory also predicts plausible mechanisms underlying quite different classes of disorders such as amyotrophic lateral sclerosis (ALS), atherosclerosis, senile cataract and many other symptoms of aging. The present theory, thus, provides the consistent and comprehensive account to the origin of aging by means of natural selection and self-organization.

  18. When stem cells grow old: phenotypes and mechanisms of stem cell aging.

    PubMed

    Schultz, Michael B; Sinclair, David A

    2016-01-01

    All multicellular organisms undergo a decline in tissue and organ function as they age. An attractive theory is that a loss in stem cell number and/or activity over time causes this decline. In accordance with this theory, aging phenotypes have been described for stem cells of multiple tissues, including those of the hematopoietic system, intestine, muscle, brain, skin and germline. Here, we discuss recent advances in our understanding of why adult stem cells age and how this aging impacts diseases and lifespan. With this increased understanding, it is feasible to design and test interventions that delay stem cell aging and improve both health and lifespan.

  19. Aged Male Rats Regenerate Cortical Bone with Reduced Osteocyte Density and Reduced Secretion of Nitric Oxide After Mechanical Stimulation

    PubMed Central

    Tayim, Riyad J.; McElderry, John-David; Morris, Michael D.; Goldstein, Steven A.

    2016-01-01

    Mechanical loading is integral to the repair of bone damage. Osteocytes are mechanosensors in bone and participate in signaling through gap junction channels, which are primarily comprised of connexin 43 (Cx43). Nitric oxide (NO) and prostaglandin E2 (PGE2) have anabolic and catabolic effects on bone, and the secretion of these molecules occurs after mechanical stimulation. The effect of age on the repair of bone tissue after damage and on the ability of regenerated bone to transduce mechanical stimulation into a cellular response is unexplored. The goal of this study was to examine (1) osteocytes and their mineralized matrix within regenerated bone from aged and mature animals and (2) the ability of regenerated bone explants from aged and mature animals to transduce cyclic mechanical loading into a cellular response through NO and PGE2 secretion. Bilateral cortical defects were created in the diaphysis of aged (21-month-old) or mature (6-month-old) male rats, and new bone tissue was allowed to grow into a custom implant of controlled geometry. Mineralization and mineral-to-matrix ratio were significantly higher in regenerated bone from aged animals, while lacunar and osteocyte density and phosphorylated (pCx43) and total Cx43 protein were significantly lower, relative to mature animals. Regenerated bone from mature rats had increased pCx43 protein and PGE2 secretion with loading and greater NO secretion relative to aged animals. Reduced osteocyte density and Cx43 in regenerated bone in aged animals could limit the establishment of gap junctions as well as NO and PGE2 secretion after loading, thereby altering bone formation and resorption in vivo. PMID:24370615

  20. The Possible Mechanism of Advanced Glycation End Products (AGEs) for Alzheimer’s Disease

    PubMed Central

    Ko, Shun-Yao; Ko, Hshin-An; Chu, Kuo-Hsiung; Shieh, Tzong-Ming; Chi, Tzong-Cherng; Chen, Hong-I; Chang, Weng-Cheng; Chang, Shu-Shing

    2015-01-01

    Amyloid precursor protein (APP) has been modified by β and γ-secretase that cause amyloid deposits (plaques) in neuronal cells. Glyceraldhyde-derived AGEs has been identified as a major source of neurotoxicity in Alzheimer’s disease (AD). In a previous study, we demonstrated that glyceraldehyde-derived AGEs increase APP and Aβ via ROS. Furthermore, the combination of AGEs and Aβ has been shown to enhance neurotoxicity. In mice, APP expression is increased by tail vein injection of AGEs. This evidence suggests a correlation between AGEs and the development of AD. However, the role played by AGEs in the pathogenesis of AD remains unclear. In this report, we demonstrate that AGEs up-regulate APP processing protein (BACE and PS1) and Sirt1 expression via ROS, but do not affect the expression of downstream antioxidant genes HO-1 and NQO-1. Moreover, we found that AGEs increase GRP78 expression and enhance the cell death-related pathway p53, bcl-2/bax ratio, caspase 3. These results indicate that AGEs impair the neuroprotective effects of Sirt1 and lead to neuronal cell death via ER stress. Our findings suggest that AGEs increase ROS production, which stimulates downstream pathways related to APP processing, Aβ production, Sirt1, and GRP78, resulting in the up-regulation of cell death related pathway. This in-turn enhances neuronal cell death, which leads to the development of AD. PMID:26587989

  1. Effects of aging on mechanical properties of composite restoratives: a depth-sensing microindentation approach.

    PubMed

    Yap, Adrian U J; Chung, S M; Rong, Y; Tsai, K T

    2004-01-01

    This study investigated the effects of aging on the hardness and modulus of two composites (Tetric Ceram [TC], Vivadent; Esthet X [EX], Dentsply), a conventional (Compoglass [CG], Vivadent) and a posterior compomer (Dyract Posterior [DP], Dentsply) using a depth-sensing microindentation approach. Seven specimens (3-mm wide x 3-mm long x 2-mm deep) of each material were made and conditioned in distilled water at 37 degrees C. Hardness and modulus of the materials were determined at seven and 30 days using depth-sensing microindentation testing with the Instron MicroTester. Hardness was determined by dividing the peak load over the maximum projected contact area while effective modulus was calculated by analysis of the loading/unloading P-h curves and the analytical model according to Oliver and Pharr (1992). Results were analyzed using one-way ANOVA/Scheffe's post-hoc test and Independent Samples t-test at significance level 0.05. Mean Vickers Hardness (HV) ranged from 46.60 to 58.67 and 44.44 to 59.41 at seven and 30 days, respectively. Mean indentation modulus ranged from 9.57 to 9.95 and 9.19 to 10.03 for the same time periods. At both time periods, EX was significantly harder than all the other materials and HV values for TC were significantly greater than CG. No significant difference in hardness and modulus was observed between seven and 30 days for all materials with the exception of CG. For the latter, a significant decrease in mechanical properties was detected over time.

  2. The Effect of Aging on the Accuracy of New Friction-Style Mechanical Torque Limiting Devices for Dental Implants

    PubMed Central

    Saboury, Aboulfazl; Sadr, Seyed Jalil; Fayaz, Ali; Mahshid, Minoo

    2013-01-01

    Objective: High variability in delivering the target torque is reported for friction-style mechanical torque limiting devices (F-S MTLDs). The effect of aging (number of use) on the accuracy of these devices is not clear. The purpose of this study was to assess the effect of aging on the accuracy (±10% of the target torque) of F-S MTLDs. Materials and Methods: Fifteen new F-S MTLDs and their appropriate drivers from three different implant manufacturers (Astra Tech, Biohorizon and Dr Idhe), five for each type, were selected. The procedure of peak torque measurement was performed in ten sequences before and after aging. In each sequence, ten repetitions of peak torque values were registered for the aging procedure. To measure the output of each device, a Tohnichi torque gauge was used. Results: Before aging, peak torque measurements of all the devices tested in this study falled within 10% of their preset target values. After aging, a significant difference was seen between raw error values of three groups of MTLDs (P<0.05). More than 50% of all peak torque measurements demonstrated more than 10% difference from their torque values after aging. Conclusion: Within the limitation of this study, aging as an independent factor affects the accuracy of F-S MTLDs. Astra Tech MTLDs presented the most consistent torque output for 25 Ncm target torque. PMID:23724202

  3. Dissecting mechanisms of brain aging by studying the intrinsic excitability of neurons

    PubMed Central

    Rizzo, Valerio; Richman, Jeffrey; Puthanveettil, Sathyanarayanan V.

    2015-01-01

    Several studies using vertebrate and invertebrate animal models have shown aging associated changes in brain function. Importantly, changes in soma size, loss or regression of dendrites and dendritic spines and alterations in the expression of neurotransmitter receptors in specific neurons were described. Despite this understanding, how aging impacts intrinsic properties of individual neurons or circuits that govern a defined behavior is yet to be determined. Here we discuss current understanding of specific electrophysiological changes in individual neurons and circuits during aging. PMID:25610394

  4. Effect of major lifestyle risk factors, independent and jointly, on life expectancy with and without cardiovascular disease: results from the Consortium on Health and Ageing Network of Cohorts in Europe and the United States (CHANCES).

    PubMed

    O'Doherty, Mark G; Cairns, Karen; O'Neill, Vikki; Lamrock, Felicity; Jørgensen, Torben; Brenner, Hermann; Schöttker, Ben; Wilsgaard, Tom; Siganos, Galatios; Kuulasmaa, Kari; Boffetta, Paolo; Trichopoulou, Antonia; Kee, Frank

    2016-05-01

    Seldom have studies taken account of changes in lifestyle habits in the elderly, or investigated their impact on disease-free life expectancy (LE) and LE with cardiovascular disease (CVD). Using data on subjects aged 50+ years from three European cohorts (RCPH, ESTHER and Tromsø), we used multi-state Markov models to calculate the independent and joint effects of smoking, physical activity, obesity and alcohol consumption on LE with and without CVD. Men and women aged 50 years who have a favourable lifestyle (overweight but not obese, light/moderate drinker, non-smoker and participates in vigorous physical activity) lived between 7.4 (in Tromsø men) and 15.7 (in ESTHER women) years longer than those with an unfavourable lifestyle (overweight but not obese, light/moderate drinker, smoker and does not participate in physical activity). The greater part of the extra life years was in terms of "disease-free" years, though a healthy lifestyle was also associated with extra years lived after a CVD event. There are sizeable benefits to LE without CVD and also for survival after CVD onset when people favour a lifestyle characterized by salutary behaviours. Remaining a non-smoker yielded the greatest extra years in overall LE, when compared to the effects of routinely taking physical activity, being overweight but not obese, and drinking in moderation. The majority of the overall LE benefit is in disease free years. Therefore, it is important for policy makers and the public to know that prevention through maintaining a favourable lifestyle is "never too late".

  5. Effects of Aging Treatment on Mechanical Properties of Sn-58Bi Epoxy Solder on ENEPIG-Surface-Finished PCB

    NASA Astrophysics Data System (ADS)

    Kim, Jungsoo; Myung, Woo-Ram; Jung, Seung-Boo

    2016-07-01

    The mechanical properties of Sn-58Bi epoxy solder were evaluated by low-speed shear testing as functions of aging time and temperature. To determine the effects of epoxy, the interfacial reaction and mechanical properties of both Sn-58Bi and Sn-58Bi epoxy solder were investigated after aging treatment. The chemical composition and growth kinetics of the intermetallic compound (IMC) formed at the interface between Sn-58Bi solder and electroless nickel electroless palladium immersion gold (ENEPIG) surface finish were analyzed. Sn-58Bi solder paste was applied by stencil-printing on flame retardant-4 substrate, then reflowed. Reflowed samples were aged at 85°C, 95°C, 105°C, and 115°C for up to 1000 h. (Ni,Pd)3Sn4 IMC formed between Sn-58Bi solder and ENEPIG surface finish after reflow. Ni3Sn4 and Ni3P IMCs formed at the interface between (Ni,Pd)3Sn4 IMC and ENEPIG surface finish after aging at 115°C for 300 h. The overall IMC growth rate of Sn-58Bi solder joint was higher than that of Sn-58Bi epoxy solder joint during aging. The shear strength of Sn-58Bi epoxy solder was about 2.4 times higher than that of Sn-58Bi solder due to the blocking effect of epoxy, and the shear strength decreased with increasing aging time.

  6. Effects of Aging Treatment on Mechanical Properties of Sn-58Bi Epoxy Solder on ENEPIG-Surface-Finished PCB

    NASA Astrophysics Data System (ADS)

    Kim, Jungsoo; Myung, Woo-Ram; Jung, Seung-Boo

    2016-11-01

    The mechanical properties of Sn-58Bi epoxy solder were evaluated by low-speed shear testing as functions of aging time and temperature. To determine the effects of epoxy, the interfacial reaction and mechanical properties of both Sn-58Bi and Sn-58Bi epoxy solder were investigated after aging treatment. The chemical composition and growth kinetics of the intermetallic compound (IMC) formed at the interface between Sn-58Bi solder and electroless nickel electroless palladium immersion gold (ENEPIG) surface finish were analyzed. Sn-58Bi solder paste was applied by stencil-printing on flame retardant-4 substrate, then reflowed. Reflowed samples were aged at 85°C, 95°C, 105°C, and 115°C for up to 1000 h. (Ni,Pd)3Sn4 IMC formed between Sn-58Bi solder and ENEPIG surface finish after reflow. Ni3Sn4 and Ni3P IMCs formed at the interface between (Ni,Pd)3Sn4 IMC and ENEPIG surface finish after aging at 115°C for 300 h. The overall IMC growth rate of Sn-58Bi solder joint was higher than that of Sn-58Bi epoxy solder joint during aging. The shear strength of Sn-58Bi epoxy solder was about 2.4 times higher than that of Sn-58Bi solder due to the blocking effect of epoxy, and the shear strength decreased with increasing aging time.

  7. User Expectations: Nurses' Perspective.

    PubMed

    Gürsel, Güney

    2016-01-01

    Healthcare is a technology-intensive industry. Although all healthcare staff needs qualified computer support, physicians and nurses need more. As nursing practice is an information intensive issue, understanding nurses' expectations from healthcare information systems (HCIS) is a must issue to meet their needs and help them in a better way. In this study perceived importance of nurses' expectations from HCIS is investigated, and two HCIS is evaluated for meeting the expectations of nurses by using fuzzy logic methodologies. PMID:27332398

  8. Influence of delay step conditions between quenching and aging on the precipitation mechanisms in the alloy AlZnMg AA7028 aging process

    SciTech Connect

    Calatayud, A.; Ferrer, C.; Amigo, V.; Salvador, M.D.

    1997-03-15

    Among precipitation-hardened alloys, the Al-Zn-Mg system includes the aluminium alloys with higher-strength. The relatively high solubility of Zn and Mg in aluminium makes it possible to produce a high density of precipitates, which results in a higher strength increase. AlZnMg low copper or copper free alloys have the advantage of being easily weldable and, moreover, they harden significantly at room temperature with respect to other weldable aluminium alloys. Due to the remarkable degree of natural aging achieved by AA7000 alloys, the time interval at room temperature between quenching and the beginning of the artificial aging treatment is a variable that must be taken into account. This work was undertaken to evaluate the influence of cooling kinetics at quenching on alloy mechanical characteristics in artificial aging at several temperatures T{sub 2}. The effect of variables that define delays after quenching, basically time t{sub 1} and temperature T{sub 1} was also analyzed. Likewise, this work studies microstructural evolution of material exposed to aging treatments, resulting from the combination of the above mentioned variables.

  9. NPY/neuropeptide Y enhances autophagy in the hypothalamus: a mechanism to delay aging?

    PubMed

    Aveleira, Célia A; Botelho, Mariana; Cavadas, Cláudia

    2015-01-01

    Aging was recently described as a life event programmed by the hypothalamus, a key brain region that is crucial for the neuroendocrine interaction between the central nervous system and the periphery. Autophagy impairment is a hallmark of aging, contributing to the aging phenotype and to the aggravation of age-related diseases. Since hypothalamic autophagy decreases with age, strategies to promote autophagy in the hypothalamus may be relevant for control of the aging process. NPY (neuropeptide Y) is an endogenous neuropeptide mainly produced by the hypothalamus. We recently reported, for the first time, that NPY stimulates autophagy in rodent hypothalamus and mediates caloric restriction-induced autophagy in hypothalamic neurons. Moreover, we observed that NPY acts through NPY1R (neuropeptide Y receptor Y1) or NPY5R activation involving a concerted action of different signaling pathways. Since both hypothalamic autophagy and NPY levels decrease with age, modulation of NPY levels could provide new putative therapeutic tools to ameliorate age-related deteriorations and extend longevity.

  10. NPY/neuropeptide Y enhances autophagy in the hypothalamus: a mechanism to delay aging?

    PubMed

    Aveleira, Célia A; Botelho, Mariana; Cavadas, Cláudia

    2015-01-01

    Aging was recently described as a life event programmed by the hypothalamus, a key brain region that is crucial for the neuroendocrine interaction between the central nervous system and the periphery. Autophagy impairment is a hallmark of aging, contributing to the aging phenotype and to the aggravation of age-related diseases. Since hypothalamic autophagy decreases with age, strategies to promote autophagy in the hypothalamus may be relevant for control of the aging process. NPY (neuropeptide Y) is an endogenous neuropeptide mainly produced by the hypothalamus. We recently reported, for the first time, that NPY stimulates autophagy in rodent hypothalamus and mediates caloric restriction-induced autophagy in hypothalamic neurons. Moreover, we observed that NPY acts through NPY1R (neuropeptide Y receptor Y1) or NPY5R activation involving a concerted action of different signaling pathways. Since both hypothalamic autophagy and NPY levels decrease with age, modulation of NPY levels could provide new putative therapeutic tools to ameliorate age-related deteriorations and extend longevity. PMID:26086271

  11. Comparison of different low-temperature aging protocols: its effects on the mechanical behavior of Y-TZP ceramics.

    PubMed

    Pereira, G K R; Muller, C; Wandscher, V F; Rippe, M P; Kleverlaan, C J; Valandro, L F

    2016-07-01

    This study evaluated the effect of different protocols of low-temperature degradation simulation on the mechanical behavior (structural reliability and flexural strength), the surface topography (roughness), and phase transformation of a Y-TZP ceramic. Disc-shaped specimens (1.2mm×12mm, Lava Frame, 3M ESPE, Seefeld, Germany) were manufactured according to ISO:6872-2008 and divided (n=30) according to the aging protocol executed: "Ctrl" - as-sintered - without any treatment; "Dist Water" - stored at distilled water at 37°C for 365 days; "MC" mechanical cycling into two steps: First - 200N, 2.2Hz for 2.000.000 cycles, Second - 450N, 10Hz for 1.000.000 cycles; "Aut" - steam autoclave at 134°C, 2bar (200kPa) for 20h; "Aut+MC"- Aut and MC methods. Roughness analysis (μm) showed, for Ra parameter, higher statistically significant values for Ctrl 0.68 (0.27), while for Rz parameter, the highest values were observed for Ctrl 4.43(1.53) and Aut 2.24 (0.62). Surface topography analysis showed that none aging method promoted surface alterations when compared to control group. Phase transformation analysis showed that all aging methods promoted an increase in m-phase content (Ctrl: 0.94%, Dist Water: 20.73%, MC: 9.47%, Aut: 53.33% and Aut+MC: 61.91%). Weibull Analysis showed higher statistical characteristic strength values for Aut (1033.36MPa) and Dist Water (1053.76MPa). No aging method promoted deleterious impact either on the biaxial flexural strengths or on the structural reliabilities (Weibull moduli). Also, none of the aging methods promoted reduction of Y-TZP mechanical properties; thus the development of new methodologies and the association between mechanical stimuli and hydrothermal degradation should be considered to better understand the mechanism of low-temperature degradation. PMID:26921592

  12. Structures and mechanical properties of ECAP processed 7075 AI alloy upon natural aging and T651 treatment.

    SciTech Connect

    Zhao, Y.; Liao, Xiaozhou; Valiev, R. Z.; Zhu, Y. T.

    2004-01-01

    Equal-channel angular pressing (ECAP) processed ultrafine grained (UFG) and coarse grained (CG) 7075 Al alloys were treated by natural aging and T651 temper (annealed at 120 C for 48 h in Ar atmosphere), respectively. Mechanical tests showed that for the UFG sample, the natural aging resulted in the highest strength (the ultimate tensile strength is 720 MPa). In contrast, for the CG sample, the T651 treatment resulted in the higher strength (the ultimate strength is 590 MPa) than the natural aging (530 MPa). Microstructural analyses indicated that the enhanced strength of the T651 treated CG sample was mainly caused by high densities of G-P zones and metastable {eta}{prime} precipitate. The enhanced strength of the naturally aged UFG sample was mainly caused by the high densities of G-P zones and dislocations. Upon T65 1 treatment, the dislocation density of the UFG sample deceased significantly, overcompensating the precipitation strengthening.

  13. A microscopic and macroscopic study of aging collagen on its molecular structure, mechanical properties, and cellular response.

    PubMed

    Wilson, Samantha L; Guilbert, Marie; Sulé-Suso, Josep; Torbet, Jim; Jeannesson, Pierre; Sockalingum, Ganesh D; Yang, Ying

    2014-01-01

    During aging, collagen structure changes, detrimentally affecting tissues' biophysical and biomechanical properties due to an accumulation of advanced glycation end-products (AGEs). In this investigation, we conducted a parallel study of microscopic and macroscopic properties of different-aged collagens from newborn to 2-yr-old rats, to examine the effect of aging on fibrillogenesis, mechanical and contractile properties of reconstituted hydrogels from these collagens seeded with or without fibroblasts. In addition to fibrillogenesis of collagen under the conventional conditions, some fibrillogenesis was conducted alongside a 12-T magnetic field, and gelation rate and AGE content were measured. A nondestructive indentation technique and optical coherence tomography were used to determine the elastic modulus and dimensional changes, respectively. It was revealed that in comparison to younger specimens, older collagens exhibited higher viscosity, faster gelation rates, and a higher AGE-specific fluorescence. Exceptionally, only young collagens formed highly aligned fibrils under magnetic fields. The youngest collagen demonstrated a higher elastic modulus and contraction in comparison to the older collagen. We conclude that aging changes collagen monomer structure, which considerably affects the fibrillogenesis process, the architecture of the resulting collagen fibers and the global network, and the macroscopic properties of the formed constructs.

  14. An Unexpected Expected Value.

    ERIC Educational Resources Information Center

    Schwartzman, Steven

    1993-01-01

    Discusses the surprising result that the expected number of marbles of one color drawn from a set of marbles of two colors after two draws without replacement is the same as the expected number of that color marble after two draws with replacement. Presents mathematical models to help explain this phenomenon. (MDH)

  15. Recurrent Sleep Fragmentation Induces Insulin and Neuroprotective Mechanisms in Middle-Aged Flies

    PubMed Central

    Williams, Michael J.; Perland, Emelie; Eriksson, Mikaela M.; Carlsson, Josef; Erlandsson, Daniel; Laan, Loora; Mahebali, Tabusi; Potter, Ella; Frediksson, Robert; Benedict, Christian; Schiöth, Helgi B.

    2016-01-01

    Lack of quality sleep increases central nervous system oxidative stress and impairs removal of neurotoxic soluble metabolites from brain parenchyma. During aging poor sleep quality, caused by sleep fragmentation, increases central nervous system cellular stress. Currently, it is not known how organisms offset age-related cytotoxic metabolite increases in order to safeguard neuronal survival. Furthermore, it is not understood how age and sleep fragmentation interact to affect oxidative stress protection pathways. We demonstrate sleep fragmentation increases systems that protect against oxidative damage and neuroprotective endoplasmic reticulum molecular chaperones, as well as neuronal insulin and dopaminergic expression in middle-aged Drosophila males. Interestingly, even after sleep recovery the expression of these genes was still upregulated in middle-aged flies. Finally, sleep fragmentation generates higher levels of reactive oxygen species (ROS) in middle-aged flies and after sleep recovery these levels remain significantly higher than in young flies. The fact that neuroprotective pathways remain upregulated in middle-aged flies beyond sleep fragmentation suggests it might represent a strong stressor for the brain during later life. PMID:27531979

  16. Effect of low-temperature aging on the mechanical behavior of ground Y-TZP.

    PubMed

    Pereira, Gkr; Amaral, M; Cesar, P F; Bottino, M C; Kleverlaan, C J; Valandro, L F

    2015-05-01

    This study evaluated the effects of low-temperature aging on the surface topography, phase transformation, biaxial flexural strength, and structural reliability of a ground Y-TZP ceramic. Disc-shaped specimens were manufactured and divided according to two factors: "grinding" - without grinding (as-sintered, Ctrl), grinding with an extra-fine diamond bur (25 µm Xfine) and coarse diamond bur (181 µm Coarse); and "low-temperature-aging" (absence or presence). Grinding was performed using a contra-angle handpiece under water-cooling. Aging was performed in an autoclave at 134 °C, under 2 bar, over a period of 20 h. Surface topography analysis showed an increase in roughness based on grit-size (Coarse>Xfine>Ctrl), and aging promoted different effects on roughness (Ctrl AgCoarse). Grinding and aging promoted an increase in the amount of m-phase, although different susceptibilities to degradation were observed. Weibull analysis showed an increase in characteristic strength after grinding (Coarse=Xfine>Ctrl); however, distinct effects were observed for aging (CtrlCoarse Ag). Weibull moduli were statistically similar. Grinding promoted an increase in characteristic strength as a result of an increase in m-phase content; when the Y-TZP surface was ground by coarse diamond burs followed by aging, characteristic strength was reduced, meaning the low-temperature degradation appeared to intensify for rougher Y-TZP surfaces. PMID:25746851

  17. Recurrent Sleep Fragmentation Induces Insulin and Neuroprotective Mechanisms in Middle-Aged Flies.

    PubMed

    Williams, Michael J; Perland, Emelie; Eriksson, Mikaela M; Carlsson, Josef; Erlandsson, Daniel; Laan, Loora; Mahebali, Tabusi; Potter, Ella; Frediksson, Robert; Benedict, Christian; Schiöth, Helgi B

    2016-01-01

    Lack of quality sleep increases central nervous system oxidative stress and impairs removal of neurotoxic soluble metabolites from brain parenchyma. During aging poor sleep quality, caused by sleep fragmentation, increases central nervous system cellular stress. Currently, it is not known how organisms offset age-related cytotoxic metabolite increases in order to safeguard neuronal survival. Furthermore, it is not understood how age and sleep fragmentation interact to affect oxidative stress protection pathways. We demonstrate sleep fragmentation increases systems that protect against oxidative damage and neuroprotective endoplasmic reticulum molecular chaperones, as well as neuronal insulin and dopaminergic expression in middle-aged Drosophila males. Interestingly, even after sleep recovery the expression of these genes was still upregulated in middle-aged flies. Finally, sleep fragmentation generates higher levels of reactive oxygen species (ROS) in middle-aged flies and after sleep recovery these levels remain significantly higher than in young flies. The fact that neuroprotective pathways remain upregulated in middle-aged flies beyond sleep fragmentation suggests it might represent a strong stressor for the brain during later life. PMID:27531979

  18. Effect of low-temperature aging on the mechanical behavior of ground Y-TZP.

    PubMed

    Pereira, Gkr; Amaral, M; Cesar, P F; Bottino, M C; Kleverlaan, C J; Valandro, L F

    2015-05-01

    This study evaluated the effects of low-temperature aging on the surface topography, phase transformation, biaxial flexural strength, and structural reliability of a ground Y-TZP ceramic. Disc-shaped specimens were manufactured and divided according to two factors: "grinding" - without grinding (as-sintered, Ctrl), grinding with an extra-fine diamond bur (25 µm Xfine) and coarse diamond bur (181 µm Coarse); and "low-temperature-aging" (absence or presence). Grinding was performed using a contra-angle handpiece under water-cooling. Aging was performed in an autoclave at 134 °C, under 2 bar, over a period of 20 h. Surface topography analysis showed an increase in roughness based on grit-size (Coarse>Xfine>Ctrl), and aging promoted different effects on roughness (Ctrl AgCoarse). Grinding and aging promoted an increase in the amount of m-phase, although different susceptibilities to degradation were observed. Weibull analysis showed an increase in characteristic strength after grinding (Coarse=Xfine>Ctrl); however, distinct effects were observed for aging (CtrlCoarse Ag). Weibull moduli were statistically similar. Grinding promoted an increase in characteristic strength as a result of an increase in m-phase content; when the Y-TZP surface was ground by coarse diamond burs followed by aging, characteristic strength was reduced, meaning the low-temperature degradation appeared to intensify for rougher Y-TZP surfaces.

  19. Recurrent Sleep Fragmentation Induces Insulin and Neuroprotective Mechanisms in Middle-Aged Flies.

    PubMed

    Williams, Michael J; Perland, Emelie; Eriksson, Mikaela M; Carlsson, Josef; Erlandsson, Daniel; Laan, Loora; Mahebali, Tabusi; Potter, Ella; Frediksson, Robert; Benedict, Christian; Schiöth, Helgi B

    2016-01-01

    Lack of quality sleep increases central nervous system oxidative stress and impairs removal of neurotoxic soluble metabolites from brain parenchyma. During aging poor sleep quality, caused by sleep fragmentation, increases central nervous system cellular stress. Currently, it is not known how organisms offset age-related cytotoxic metabolite increases in order to safeguard neuronal survival. Furthermore, it is not understood how age and sleep fragmentation interact to affect oxidative stress protection pathways. We demonstrate sleep fragmentation increases systems that protect against oxidative damage and neuroprotective endoplasmic reticulum molecular chaperones, as well as neuronal insulin and dopaminergic expression in middle-aged Drosophila males. Interestingly, even after sleep recovery the expression of these genes was still upregulated in middle-aged flies. Finally, sleep fragmentation generates higher levels of reactive oxygen species (ROS) in middle-aged flies and after sleep recovery these levels remain significantly higher than in young flies. The fact that neuroprotective pathways remain upregulated in middle-aged flies beyond sleep fragmentation suggests it might represent a strong stressor for the brain during later life.

  20. Dynamic mechanical properties of a maxillofacial silicone elastomer incorporating a ZnO additive: the effect of artificial aging.

    PubMed

    Mouzakis, Dionysios E; Papadopoulos, Triantafillos D; Polyzois, Gregory L; Griniari, Panagiota G

    2010-11-01

    The main objective of the current study was to investigate the dynamic mechanical properties of a room-temperature vulcanizing silicone incorporating different fractions of zinc oxide (ZnO) after indoor and outdoor photoaging. Forty-eight samples were produced by adding different amounts of ZnO into a commercial maxillofacial silicone (EPISIL-E). The samples were divided into 4 groups containing 0.0, 0.2, 0.5, and 1 wt% ZnO additive, respectively. Samples were exposed to sunlight (subgroup 2), ultraviolet (subgroup 3), and fluorescence (subgroup 4) aging, whereas nonaged samples comprised the control subgroup (subgroup 1). Dynamic mechanical analysis was used to determine the storage modulus (E'), loss modulus (E″), and damping capacity (tanδ). General linear statistic model was conducted to evaluate the effects of aging, testing frequency, and composition on the dynamic mechanical properties of the silicone with the ZnO additive. Post hoc analysis was performed using Tukey test. Statistical analysis revealed a significant impact of composition on tanδ (P < 0.05). Aging influenced E' and E″ (P < 0.01). The combination of aging and composition had a significant effect on all dynamic properties (P < 0.01).

  1. Dynamic mechanical properties of a maxillofacial silicone elastomer incorporating a ZnO additive: the effect of artificial aging.

    PubMed

    Mouzakis, Dionysios E; Papadopoulos, Triantafillos D; Polyzois, Gregory L; Griniari, Panagiota G

    2010-11-01

    The main objective of the current study was to investigate the dynamic mechanical properties of a room-temperature vulcanizing silicone incorporating different fractions of zinc oxide (ZnO) after indoor and outdoor photoaging. Forty-eight samples were produced by adding different amounts of ZnO into a commercial maxillofacial silicone (EPISIL-E). The samples were divided into 4 groups containing 0.0, 0.2, 0.5, and 1 wt% ZnO additive, respectively. Samples were exposed to sunlight (subgroup 2), ultraviolet (subgroup 3), and fluorescence (subgroup 4) aging, whereas nonaged samples comprised the control subgroup (subgroup 1). Dynamic mechanical analysis was used to determine the storage modulus (E'), loss modulus (E″), and damping capacity (tanδ). General linear statistic model was conducted to evaluate the effects of aging, testing frequency, and composition on the dynamic mechanical properties of the silicone with the ZnO additive. Post hoc analysis was performed using Tukey test. Statistical analysis revealed a significant impact of composition on tanδ (P < 0.05). Aging influenced E' and E″ (P < 0.01). The combination of aging and composition had a significant effect on all dynamic properties (P < 0.01). PMID:21119441

  2. Mechanical properties of calcia stabilized zirconia following in vivo and in vitro aging.

    PubMed

    Kenner, G H; Pasco, W D; Frakes, J T; Brown, S D

    1975-07-01

    Aging studies were done on calcia stabilized zirconia rods of 72% theoretical density to determine the effect of actual and simulated biological environments on their strength. They were aged without stress in vitro in Ringer's solution for 1, 2 and 4weeks or in vivo in rabbits for 12 weeks. Rods aged in vitro showed mean losses in bending strength of 16, 17 and 19% respectively after 1, 2 and 4 weeks of immersion, while those aged in vivo showed a mean loss of 25%. It was concluded that the material tested would be unsatisfactory as an orthopedic replacement because of the rapid decrease in strength which occurred when exposed to actual or simulated biological media.

  3. Peripheral mechanisms of thermoregulatory control of skin blood flow in aged humans

    PubMed Central

    Kenney, W. Larry

    2010-01-01

    Human skin blood flow is controlled via dual innervation from the sympathetic nervous system. Reflex cutaneous vasoconstriction and vasodilation are both impaired with primary aging, rendering the aged more vulnerable to hypothermia and cardiovascular complications from heat-related illness. Age-related alterations in the thermoregulatory control of skin blood flow occur at multiple points along the efferent arm of the reflex, including 1) diminished sympathetic outflow, 2) altered presynaptic neurotransmitter synthesis, 3) reduced vascular responsiveness, and 4) impairments in downstream (endothelial and vascular smooth muscle) second-messenger signaling. This mechanistic review highlights some of the recent findings in the area of aging and the thermoregulatory control of skin blood flow. PMID:20413421

  4. Investigation of aging mechanisms of high power Li-ion cells used for hybrid electric vehicles

    NASA Astrophysics Data System (ADS)

    Bourlot, Sandrine; Blanchard, Philippe; Robert, Stéphanie

    High power lithium-ion batteries need to exhibit long service life to meet targets of automotive applications. This article describes the deep investigation of the so-called VL6P cells, high power lithium-ion cells mass produced by Johnson Controls - Saft (JC-S), in order to understand the root causes of their aging. Cells aged by calendar and cycle life are investigated here compared to fresh cells. Among the results of the different analyses, the most significant is that more active lithium is detected in negative electrode after aging. This tends to indicate that effect of aging is due to increase of positive electrode limitation. Results of this investigation will allow JC-S to continue to improve life of the lithium-ion cells.

  5. Influence of Thermal Aging on the Microstructure and Mechanical Behavior of Dual Phase Precipitation Hardened Powder Metallurgy Stainless Steels

    NASA Astrophysics Data System (ADS)

    Stewart, Jennifer

    2011-12-01

    Increasing demand for high strength powder metallurgy (PM) steels has resulted in the development of dual phase PM steels. In this work, the effects of thermal aging on the microstructure and mechanical behavior of dual phase precipitation hardened powder metallurgy (PM) stainless steels of varying ferrite-martensite content were examined. Quantitative analyses of the inherent porosity and phase fractions were conducted on the steels and no significant differences were noted with respect to aging temperature. Tensile strength, yield strength, and elongation to fracture all increased with increasing aging temperature reaching maxima at 538°C in most cases. Increased strength and decreased ductility were observed in steels of higher martensite content. Nanoindentation of the individual microconstituents was employed to obtain a fundamental understanding of the strengthening contributions. Both the ferrite and martensite hardness values increased with aging temperature and exhibited similar maxima to the bulk tensile properties. Due to the complex non-uniform stresses and strains associated with conventional nanoindentation, micropillar compression has become an attractive method to probe local mechanical behavior while limiting strain gradients and contributions from surrounding features. In this study, micropillars of ferrite and martensite were fabricated by focused ion beam (FIB) milling of dual phase precipitation hardened powder metallurgy (PM) stainless steels. Compression testing was conducted using a nanoindenter equipped with a flat punch indenter. The stress-strain curves of the individual microconstituents were calculated from the load-displacement curves less the extraneous displacements of the system. Using a rule of mixtures approach in conjunction with porosity corrections, the mechanical properties of ferrite and martensite were combined for comparison to tensile tests of the bulk material, and reasonable agreement was found for the ultimate tensile

  6. HSP27 Alleviates Cardiac Aging in Mice via a Mechanism Involving Antioxidation and Mitophagy Activation

    PubMed Central

    Lin, Shenglan; Wang, Yana; Zhang, Xiaojin; Kong, Qiuyue; Li, Chuanfu; Li, Yuehua; Ding, Zhengnian

    2016-01-01

    Aging-induced cardiac dysfunction is a prominent feature of cardiac aging. Heat shock protein 27 (HSP27) protects cardiac function against ischemia or chemical challenge. We hypothesized that HSP27 attenuates cardiac aging. Transgenic (Tg) mice with cardiac-specific expression of the HSP27 gene and wild-type (WT) littermates were employed in the experiments. Echocardiography revealed a significant decline in the cardiac function of old WT mice compared with young WT mice. In striking contrast, the aging-induced impairment of cardiac function was attenuated in old Tg mice compared with old WT mice. Levels of cardiac aging markers were lower in old Tg mouse hearts than in old WT mouse hearts. Less interstitial fibrosis and lower contents of reactive oxygen species and ubiquitin-conjugated proteins were detected in old Tg hearts than in old WT hearts. Furthermore, old Tg hearts demonstrated lower accumulation of LC3-II and p62 than old WT hearts. Levels of Atg13, Vps34, and Rab7 were also higher in old Tg hearts than in old WT hearts. Additionally, old Tg hearts had higher levels of PINK1 and Parkin than old WT hearts, suggesting that mitophagy was activated in old Tg hearts. Taken together, HSP27 alleviated cardiac aging and this action involved antioxidation and mitophagy activation. PMID:27110324

  7. Aging mechanisms in the Westinghouse PWR (Pressurized Water Reactor) Control Rod Drive system

    SciTech Connect

    Gunther, W.; Sullivan, K.

    1991-01-01

    An aging assessment of the Westinghouse Pressurized Water Reactor (PWR) Control Rod System (CRD) has been completed as part of the US NRC's Nuclear Plant Aging Research, (NPAR) Program. This study examined the design, construction, maintenance, and operation of the system to determine its potential for degradation as the plant ages. Selected results from this study are presented in this paper. The operating experience data were evaluated to identify the predominant failure modes, causes, and effects. From our evaluation of the data, coupled with an assessment of the materials of construction and the operating environment, we conclude that the Westinghouse CRD system is subject to degradation which, if unchecked, could affect its safety function as a plant ages. Ways to detect and mitigate the effects of aging are included in this paper. The current maintenance for the control rod drive system at fifteen Westinghouse PWRs was obtained through a survey conducted in cooperation with EPRI and NUMARC. The results of the survey indicate that some plants have modified the system, replaced components, or expanded preventive maintenance. Several of these activities have effectively addressed the aging issue. 2 refs., 2 figs., 2 tabs.

  8. What can long-lived mutants tell us about mechanisms causing aging and lifespan variation in natural environments?

    PubMed

    Briga, Michael; Verhulst, Simon

    2015-11-01

    Long-lived mutants of model organisms have brought remarkable progress in our understanding of aging mechanisms. However, long-lived mutants are usually maintained in optimal standardized laboratory environments (SLEs), and it is not obvious to what extent insights from long-lived mutants in SLEs can be generalized to more natural environments. To address this question, we reviewed experiments that compared the fitness and lifespan advantage of long-lived mutants relative to wild type controls in SLEs and more challenging environments in various model organisms such as yeast Saccharomyces cerevisiae, the nematode worm Caenorhabditis elegans, the fruitfly Drosophila melanogaster and the mouse Mus musculus. In competition experiments over multiple generations, the long-lived mutants had a lower fitness relative to wild type controls, and this disadvantage was the clearest when the environment included natural challenges such as limited food (N=6 studies). It is well known that most long-lived mutants have impaired reproduction, which provides one reason for the fitness disadvantage. However, based on 12 experiments, we found that the lifespan advantage of long-lived mutants is diminished in more challenging environments, often to the extent that the wild type controls outlive the long-lived mutants. Thus, it appears that information on aging mechanisms obtained from long-lived mutants in SLEs may be specific to such environments, because those same mechanisms do not extend lifespan in more natural environments. This suggests that different mechanisms cause variation in aging and lifespan in SLEs compared to natural populations.

  9. A Nanoindentation Study on Grain-Boundary Contributions to Strengthening and Aging Degradation Mechanisms in Advanced 12Cr Ferritic Steel

    SciTech Connect

    Jang, Jae-il; Shim, Sang Hoon; Komazaki, Shin-ichi; Honda, Tetsuya

    2007-01-01

    Nanoindentation experiments and microstructural analysis were performed on advanced 12% Cr ferritic steel having extremely fine and complex martensitic microstructures, to answer unsolved questions on the contributions of grain boundaries to strengthening and aging degradation mechanisms in both as-tempered and thermally aged steels. Interesting features of the experimental results led us to suggest that among several high angle boundaries, block boundary is most effective in enhancing the macroscopic strength in as-tempered virgin sample, and that a decrease in matrix strength rather than reduction in grain-boundary strengthening effect is primarily responsible for the macroscopic softening behavior observed during thermal exposure.

  10. Age-Dependent Changes in Geometry, Tissue Composition and Mechanical Properties of Fetal to Adult Cryopreserved Human Heart Valves.

    PubMed

    van Geemen, Daphne; Soares, Ana L F; Oomen, Pim J A; Driessen-Mol, Anita; Janssen-van den Broek, Marloes W J T; van den Bogaerdt, Antoon J; Bogers, Ad J J C; Goumans, Marie-José T H; Baaijens, Frank P T; Bouten, Carlijn V C

    2016-01-01

    There is limited information about age-specific structural and functional properties of human heart valves, while this information is key to the development and evaluation of living valve replacements for pediatric and adolescent patients. Here, we present an extended data set of structure-function properties of cryopreserved human pulmonary and aortic heart valves, providing age-specific information for living valve replacements. Tissue composition, morphology, mechanical properties, and maturation of leaflets from 16 pairs of structurally unaffected aortic and pulmonary valves of human donors (fetal-53 years) were analyzed. Interestingly, no major differences were observed between the aortic and pulmonary valves. Valve annulus and leaflet dimensions increase throughout life. The typical three-layered leaflet structure is present before birth, but becomes more distinct with age. After birth, cell numbers decrease rapidly, while remaining cells obtain a quiescent phenotype and reside in the ventricularis and spongiosa. With age and maturation-but more pronounced in aortic valves-the matrix shows an increasing amount of collagen and collagen cross-links and a reduction in glycosaminoglycans. These matrix changes correlate with increasing leaflet stiffness with age. Our data provide a new and comprehensive overview of the changes of structure-function properties of fetal to adult human semilunar heart valves that can be used to evaluate and optimize future therapies, such as tissue engineering of heart valves. Changing hemodynamic conditions with age can explain initial changes in matrix composition and consequent mechanical properties, but cannot explain the ongoing changes in valve dimensions and matrix composition at older age.

  11. Weaning from mechanical ventilation: a cross-sectional study of reference values and the discriminative validity of aging

    PubMed Central

    Corbellini, Camilo; Trevisan, Cristiane Brenner Eilert; Villafañe, Jorge Hugo; Doval da Costa, Alexandre; Vieira, Silvia Regina Rios

    2015-01-01

    [Purpose] To evaluate pre-extubation variables and check the discriminative validity of age as well as its correlation with weaning failure in elderly patients. [Subjects and Methods] Two hundred thirty-nine consecutive patients (48% female) who were on mechanical ventilation and had undergone orotracheal intubation were divided into four subgroups according to their age: <59 years, 60–69 years, 70–79 years, and >80 years old. The expiratory volume (VE), respiratory frequency (f), tidal volume (VT), and respiratory frequency/tidal volume ratio (f/VT) were used to examine differences in weaning parameters between the four subgroups, and age was correlated with weaning failure. [Results] The rate of weaning failure was 27.8% in patients aged >80 years and 22.1% in patients aged <60 years old. Elderly patients presented higher f/VT and f values and lower VT values. The areas under the receiver operating characteristic curves for f/VT ratio were smaller than those published previously. [Conclusion] Our results indicate that aging influences weaning criteria without causing an increase in weaning failure. PMID:26180354

  12. The aging behavior of types 308 and 308CRE stainless steels and its effect on mechanical properties

    SciTech Connect

    Vitek, J.M.; David, S.A.

    1987-01-01

    Aging of 308 and 308CRE SS was studied at 475 to 850/sup 0/C for aging times up to 10,000 hours. Above 550/sup 0/C, aging of 308 steel resulted in precipitation of carbides and the transformation of ferrite to sigma phase or the formation of sigma phase in initially ferrite-free material. The elevated-temperature aging of 308CRE steel resulted in the precipitation of titanium-rich carbides, nitrides, and sulfides, and the transformation of ferrite to sigma phase. The distribution of precipitates was affected by the initial condition of the materials. The elevated-temperature creep properties, and in particular the improved properties of 308CRE, were related to the precipitate distribution. Below 550/sup 0/C, aging of welded type 308 steel, precipitation of G-phase within the ferrite was observed, as well as the decomposition of ferrite into alpha and alpha prime. With the help of a novel mechanical properties microprobe, which was capable of determining the hardness of the minor constituent ferrite phase, the hardness behavior as a function of aging could be related to the microstructures. These results are interpreted in terms of the potential susceptibility of these alloys to 475/sup 0/C embrittlement.

  13. Sarcopenia, obesity, and natural killer cell immune senescence in aging: altered cytokine levels as a common mechanism.

    PubMed

    Lutz, Charles T; Quinn, LeBris S

    2012-08-01

    Human aging is characterized by both physical and physiological frailty. A key feature of frailty, sarcopenia is the age-associated decline in skeletal muscle mass, strength, and endurance that characterize even the healthy elderly. Increases in adiposity, particularly in visceral adipose tissue, are almost universal in aging individuals and can contribute to sarcopenia and insulin resistance by increasing levels of inflammatory cytokines known collectively as adipokines. Aging also is associated with declines in adaptive and innate immunity, known as immune senescence, which are risk factors for cancer and all-cause mortality. The cytokine interleukin-15 (IL-15) is highly expressed in skeletal muscle tissue and declines in aging rodent models. IL-15 inhibits fat deposition and insulin resistance, is anabolic for skeletal muscle in certain situations, and is required for the development and survival of natural killer (NK) lymphocytes. We review the effect that adipokines and myokines have on NK cells, with special emphasis on IL-15. We posit that increased adipokine and decreased IL-15 levels during aging constitute a common mechanism for sarcopenia, obesity, and immune senescence.

  14. Hormetic mechanisms of anti-aging and rejuvenating effects of repeated mild heat stress on human fibroblasts in vitro.

    PubMed

    Rattan, Suresh I S

    2004-01-01

    The phenomenon of hormesis is represented by mild stress-induced stimulation of maintenance and repair pathways, resulting in beneficial effects for cells and organisms. We have reported that repeated mild heat stress (RMHS) has anti-aging hormetic effects on growth and various cellular and biochemical characteristics of human skin fibroblasts undergoing aging in vitro. These effects of RMHS include the maintenance of the stress protein profile, reduction in the accumulation of oxidatively and glycoxidatively damaged proteins, stimulation of the activities of the proteasome and its 11S activator, improvement in cellular resistance to ethanol, hydrogen peroxide, and ultraviolet rays, and increased antioxidative activity of the cells. We have also reported that RMHS prolongs the lifespan of Drosophila. Others have reported anti-aging and life prolonging effects of a wide variety of so-called stressors, such as pro-oxidants, aldehydes, calorie restriction, irradiation, heat shock, and hypergravity. Although molecular mechanisms of hormesis are yet to be elucidated, there are indications that relatively small hormetic effects become biologically amplified, resulting in significant improvement of cellular and organic functions and survival. Hormesis, therefore, can be an effective approach for modulating aging, for preventing or delaying the onset of age-related diseases, and for improving the quality of life in old age.

  15. Molecular mechanism of extrinsic factors affecting anti-aging of stem cells

    PubMed Central

    Wong, Tzyy Yue; Solis, Mairim Alexandra; Chen, Ying-Hui; Huang, Lynn Ling-Huei

    2015-01-01

    Scientific evidence suggests that stem cells possess the anti-aging ability to self-renew and maintain differentiation potentials, and quiescent state. The objective of this review is to discuss the micro-environment where stem cells reside in vivo, the secreted factors to which stem cells are exposed, the hypoxic environment, and intracellular factors including genome stability, mitochondria integrity, epigenetic regulators, calorie restrictions, nutrients, and vitamin D. Secreted tumor growth factor-β and fibroblast growth factor-2 are reported to play a role in stem cell quiescence. Extracellular matrices may interact with caveolin-1, the lipid raft on cell membrane to regulate quiescence. N-cadherin, the adhesive protein on niche cells provides support for stem cells. The hypoxic micro-environment turns on hypoxia-inducible factor-1 to prevent mesenchymal stem cells aging through p16 and p21 down-regulation. Mitochondria express glucosephosphate isomerase to undergo glycolysis and prevent cellular aging. Epigenetic regulators such as p300, protein inhibitors of activated Stats and H19 help maintain stem cell quiescence. In addition, calorie restriction may lead to secretion of paracrines cyclic ADP-ribose by intestinal niche cells, which help maintain intestinal stem cells. In conclusion, it is crucial to understand the anti-aging phenomena of stem cells at the molecular level so that the key to solving the aging mystery may be unlocked. PMID:25815136

  16. Molecular mechanism of extrinsic factors affecting anti-aging of stem cells.

    PubMed

    Wong, Tzyy Yue; Solis, Mairim Alexandra; Chen, Ying-Hui; Huang, Lynn Ling-Huei

    2015-03-26

    Scientific evidence suggests that stem cells possess the anti-aging ability to self-renew and maintain differentiation potentials, and quiescent state. The objective of this review is to discuss the micro-environment where stem cells reside in vivo, the secreted factors to which stem cells are exposed, the hypoxic environment, and intracellular factors including genome stability, mitochondria integrity, epigenetic regulators, calorie restrictions, nutrients, and vitamin D. Secreted tumor growth factor-β and fibroblast growth factor-2 are reported to play a role in stem cell quiescence. Extracellular matrices may interact with caveolin-1, the lipid raft on cell membrane to regulate quiescence. N-cadherin, the adhesive protein on niche cells provides support for stem cells. The hypoxic micro-environment turns on hypoxia-inducible factor-1 to prevent mesenchymal stem cells aging through p16 and p21 down-regulation. Mitochondria express glucosephosphate isomerase to undergo glycolysis and prevent cellular aging. Epigenetic regulators such as p300, protein inhibitors of activated Stats and H19 help maintain stem cell quiescence. In addition, calorie restriction may lead to secretion of paracrines cyclic ADP-ribose by intestinal niche cells, which help maintain intestinal stem cells. In conclusion, it is crucial to understand the anti-aging phenomena of stem cells at the molecular level so that the key to solving the aging mystery may be unlocked.

  17. Mechanical Testing of TR-55 Rubber Thermally Aged Under Tensile Strain

    SciTech Connect

    Small IV, W; Alviso, C T; Wilson, T S; Chinn, S C; Maxwell, R S

    2009-03-10

    TR-55 rubber specimens were previously subjected to an aging process consisting of the application of a tensile strain of approximately 67%, 100%, 133%, or 167% elongation for 4, 8, 12, or 16 h at either 250 C or room temperature. Control specimens at the same temperatures/durations were not subjected to tensile strain. The specimens were allowed to recover at room temperature without external stimuli for over 100 days before tensile testing. A single dog bone was cut from each specimen and a stress-strain curve was obtained. The elastic modulus of each specimen was calculated. Specimens aged under tensile strain exhibited rubber-like behavior dependent on the aging elongation and duration. This behavior was not evident in the unstrained controls. For the unstrained controls, exposure to 250 C resulted in an increase in modulus relative to the unheated material independent of the heating duration. The tensile strain applied during the aging process caused a reduction in modulus relative to the controls; lower moduli were observed for the shorter aging durations. Slippage of the specimens in the grips prevented determination of ultimate strength, as all specimens either slipped completely out of the grip before failure or failed at the original grip edge after slipping.

  18. Degradation of mechanical properties of stainless steel cladding due to neutron irradiation and thermal aging

    SciTech Connect

    Haggag, F.M.

    1994-09-01

    Thermal aging of three-wire series-arc stainless steel weld overlay cladding at 288{degrees}C for 1605 h resulted in an appreciable decrease (16%) in the Charpy V-notch (CVN) upper-shelf energy (USE), but the effect on the 41-J transition temperature shift was very small (3{degrees}C). The combined effect following neutron irradiation at 288{degrees}C to a fluence of 5 X 10{sup 19} neutrons/cm{sup 2} (>1 MeV) was a 22% reduction in the USE and a 29{degrees}C shift in the 41-J transition temperature. The effect of thermal aging on tensile properties was very small. However, the combined effect of irradiation and aging was an increase in the yield strength (6 to 34% at test temperatures from 288 to -125{degrees}C) and no apparent change in ultimate tensile strength or total elongation. Neutron irradiation reduced the initiation fracture toughness (J{sub {kappa}}) much more than did thermal aging alone. However, irradiation slightly decreased the tearing modulus but no reduction was caused by thermal aging alone. The effects of long-term thermal exposure times (20,000 and 50,000 h) will be investigated when the specimens become available. Also, long-term thermal exposure of the three-wire cladding as well as type 308 stainless steel weld materials at 343{degrees}C is in progress.

  19. Health expectancy indicators.

    PubMed Central

    Robine, J. M.; Romieu, I.; Cambois, E.

    1999-01-01

    An outline is presented of progress in the development of health expectancy indicators, which are growing in importance as a means of assessing the health status of populations and determining public health priorities. PMID:10083720

  20. [Molecular mechanisms of combined extremely radiofrequency and infrared therapy in various age patients with chronic parodontitis].

    PubMed

    Ianova, O A; Medvedev, D S; Lin'kova, N S; Trifonov, N I; D'iakonov, M M

    2014-01-01

    The influence of extreme radiofrequency millimeter microwave (EHF) and infrared (IR) electromagnetic emanation on the molecular markers of cell renovation (Ki67, p53) and proinflammatory cytokine TNF-α expression in the buccal cells of various age patients with chronic parodontitis was investigated. The results show that EHF- and IR-electromagnetic emanation increased Ki67 proliferative marker expression and decreased expression of proapoptosis protein p53 and proinflammatory cytokine TNF-α in the buccal epithelium of young, middle-aged and elderly people with chronic parodontitis. The data obtained open the new ability for patogenetic treatment of various age patients with chronic parodontitis using the EHF- and IR-electromagnetic emanation method.

  1. Influence of Sea Water Aging on the Mechanical Behaviour of Acrylic Matrix Composites

    NASA Astrophysics Data System (ADS)

    Davies, P.; Le Gac, P.-Y.; Le Gall, M.

    2016-07-01

    A new matrix resin was recently introduced for composite materials, based on acrylic resin chemistry allowing standard room temperature infusion techniques to be used to produce recyclable thermoplastic composites. This is a significant advance, particularly for more environmentally-friendly production of large marine structures such as boats. However, for such applications it is essential to demonstrate that composites produced with these resins resist sea water exposure in service. This paper presents results from a wet aging study of unreinforced acrylic and glass and carbon fibre reinforced acrylic composites. It is shown that the acrylic matrix resin is very stable in seawater, showing lower property losses after seawater aging than those of a commonly-used epoxy matrix resin. Carbon fibre reinforced acrylic also shows good property retention after aging, while reductions in glass fibre reinforced composite strengths suggest that specific glass fibre sizing may be required for optimum durability.

  2. Kinetics and mechanism of thermal aging embrittlement of duplex stainless steels

    SciTech Connect

    Chung, H.M.; Chopra, O.K.

    1987-06-01

    Microstructural characteristics of long-term-aged cast duplex stainless steel specimens from eight laboratory heats and an actual component from a commercial boiling water reactor have been investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), small angle neutron scattering (SANS), and atom probe field ion microscopy (APFIM) techniques. Three precipitate phases, i.e., Cr-rich ..cap alpha..' and the Ni- and Si-rich G phase, and ..gamma../sub 2/ austenite, have been identified in the ferrite matrix of the aged specimens. For CF-8 grade materials, M/sub 23/C/sub 6/ carbides were identified on the austenite-ferrite boundaries as well as in the ferrite matrix for aging at greater than or equal to 450/sup 0/C. It has been shown that Si, C, and Mo contents are important factors that influence the kinetics of the G-phase precipitation. However, TEM and APFIM analyses indicate that the embrittlement for less than or equal to400/sup 0/C aging is primarily associated with Fe and Cr segregation in ferrite by spinodal decomposition. For extended aging, e.g., 6 to 8 years at 350 to 400/sup 0/C, large platelike ..cap alpha..' formed by nucleation and growth from the structure produced by the spinodal decomposition. The Cr content appears to play an important role either to promote the platelike ..cap alpha..' (high Cr content) or to suppress the ..cap alpha..' in favor of ..gamma../sub 2/ precipitation (low Cr). Approximate TTT diagrams for the spinodal, ..cap alpha..', G, ..gamma../sub 2/, and the in-ferrite M/sub 23/C/sub 6/ have been constructed for 250 to 450/sup 0/C aging. Microstructural modifications associated with a 550/sup 0/C reannealing and a subsequent toughness restoration are also discussed. It is shown that the toughness restoration is associated primarily with the dissolution of the Cr-rich region in ferrite.

  3. Adaptive and regulatory mechanisms in aged rats with postoperative cognitive dysfunction

    PubMed Central

    Bi, Yanlin; Liu, Shuyun; Yu, Xinjuan; Wang, Mingshan; Wang, Yuelan

    2014-01-01

    Inflammation may play a role in postoperative cognitive dysfunction. 5′ Adenosine monophosphate-activated protein kinase, nuclear factor-kappa B, interleukin-1β, and tumor necrosis factor-α are involved in inflammation. Therefore, these inflammatory mediators may be involved in postoperative cognitive dysfunction. Western immunoblot analysis revealed 5′ adenosine monophosphate-activated protein kinase and nuclear factor-kappa B in the hippocampus of aged rats were increased 1–7 days after splenectomy. Moreover, interleukin-1β and tumor necrosis factor-α were upregulated and gradually decreased. Therefore, these inflammatory mediators may participate in the splenectomy model of postoperative cognitive dysfunction in aged rats. PMID:25206851

  4. Lamb wave characterization of the effects of long-term thermal-mechanical aging on composite stiffness

    NASA Technical Reports Server (NTRS)

    Seale, M. D.; Madaras, E. I.

    1999-01-01

    Lamb waves offer a promising method of evaluating damage in composite materials. The Lamb wave velocity is directly related to the material parameters, so an effective tool exists to monitor damage in composites by measuring the velocity of these waves. The Lamb Wave Imager (LWI) uses a pulse/receive technique that excites an antisymmetric Lamb mode and measures the time-of-flight over a wide frequency range. Given the material density and plate thickness, the bending and out-of-plane shear stiffnesses are calculated from a reconstruction of the dispersion curve. In this study, the time-of-flight as well as the elastic stiffnesses D11, D22, A44, and A55 for composite samples which have undergone combined thermal and mechanical aging are obtained. The samples examined include a baseline specimen with 0 cycles, specimens which have been aged 2350 and 3530 cycles at high strain levels, and one specimen aged 3530 cycles at low strain levels.

  5. Lamb wave characterization of the effects of long-term thermal-mechanical aging on composite stiffness.

    PubMed

    Seale, M D; Madaras, E I

    1999-09-01

    Lamb waves offer a promising method of evaluating damage in composite materials. The Lamb wave velocity is directly related to the material parameters, so an effective tool exists to monitor damage in composites by measuring the velocity of these waves. The Lamb Wave Imager (LWI) uses a pulse/receive technique that excites an antisymmetric Lamb mode and measures the time-of-flight over a wide frequency range. Given the material density and plate thickness, the bending and out-of-plane shear stiffnesses are calculated from a reconstruction of the dispersion curve. In this study, the time-of-flight as well as the elastic stiffnesses D11, D22, A44, and A55 for composite samples which have undergone combined thermal and mechanical aging are obtained. The samples examined include a baseline specimen with 0 cycles, specimens which have been aged 2350 and 3530 cycles at high strain levels, and one specimen aged 3530 cycles at low strain levels.

  6. Mechanisms and implications of age-associated impaired innate interferon secretion by dendritic cells: a mini-review.

    PubMed

    Agrawal, Anshu

    2013-01-01

    Initial secretion of interferons by innate immune cells such as dendritic cells is crucial for protection against infections as well as for alerting and activating the downstream immune responses. The secretion of innate interferons, both type I and type III, by dendritic cells is severely impaired in aged subjects. This review focuses on the mechanisms responsible for the reduced interferon secretion by dendritic cells and the role this plays in the increased susceptibility of the elderly to infections, particularly of the respiratory mucosa.

  7. Exaggerated neurobiological sensitivity to threat as a mechanism linking anxiety with increased risk for diseases of aging

    PubMed Central

    O’Donovan, Aoife; Slavich, George M; Epel, Elissa S.; Neylan, Thomas C

    2015-01-01

    Anxiety disorders increase risk for the early development of several diseases of aging. Elevated inflammation, a common risk factor across diseases of aging, may play a key role in the relationship between anxiety and physical disease. However, the neurobiological mechanisms linking anxiety with elevated inflammation remain unclear. In this review, we present a neurobiological model of the mechanisms by which anxiety promotes inflammation. Specifically we propose that exaggerated neurobiological sensitivity to threat in anxious individuals may lead to sustained threat perception, which is accompanied by prolonged activation of threat-related neural circuitry and threat-responsive biological systems including the hypothalamic-pituitary-adrenal (HPA) axis, autonomic nervous system (ANS), and inflammatory response. Over time, this pattern of responding can promote chronic inflammation through structural and functional brain changes, altered sensitivity of immune cell receptors, dysregulation of the HPA axis and ANS, and accelerated cellular aging. Chronic inflammation, in turn, increases risk for diseases of aging. Exaggerated neurobiological sensitivity to threat may thus be a treatment target for reducing disease risk in anxious individuals. PMID:23127296

  8. Dysregulation of SIRT-1 in aging mice increases skeletal muscle fatigue by a PARP-1-dependent mechanism

    PubMed Central

    Mohamed, Junaith S.; Wilson, Joseph C.; Myers, Matthew J.; Sisson, Kayla J.; Alway, Stephen E.

    2014-01-01

    Accumulation of reactive oxygen species (ROS) in skeletal muscles and the resulting decline in muscle performance are hallmarks of sarcopenia. However, the precise mechanism by which ROS results in a decline in muscle performance is unclear. We demonstrate that isometric-exercise concomitantly increases the activities of Silent information regulator 1 (SIRT-1) and Poly [ADP-ribose] polymerase (PARP-1), and that activated SIRT-1 physically binds with and inhibits PARP-1 activity by a deacetylation dependent mechanism in skeletal muscle from young mice. In contrast, skeletal muscle from aged mice displays higher PARP-1 activity and lower SIRT-1 activity due to decreased intracellular NAD+ content, and as a result reduced muscle performance in response to exercise. Interestingly, injection of PJ34, a PARP-1 inhibitor, in aged mice increased SIRT-1 activity by preserving intracellular NAD+ content, which resulted in higher skeletal muscle mitochondrial biogenesis and performance. We found that the higher activity of PARP-1 in H2O2-treated myotubes or in exercised-skeletal muscles from aged mice is due to an elevated level of PARP-1 acetylation by the histone acetyltransferase General control of amino acid synthesis protein 5-like 2 (GCN-5). These results suggest that activation of SIRT-1 and/or inhibition of PARP-1 may ameliorate skeletal muscle performance in pathophysiological conditions such as sarcopenia and disuse-induced atrophy in aging. PMID:25361036

  9. The effects of mechanical transparency on adjustment to a complex visuomotor transformation at early and late working age.

    PubMed

    Heuer, Herbert; Hegele, Mathias

    2010-12-01

    Mechanical tools are transparent in the sense that their input-output relations can be derived from their perceptible characteristics. Modern technology creates more and more tools that lack mechanical transparency, such as in the control of the position of a cursor by means of a computer mouse or some other input device. We inquired whether an enhancement of transparency by means of presenting the shaft of a virtual sliding lever, which governed the transformation of hand position into cursor position, supports performance of aimed cursor movement and the acquisition of an internal model of the transformation in both younger and older adults. Enhanced transparency resulted in an improvement of visual closed-loop control in terms of movement time and curvature of cursor paths. The movement-time improvement was more pronounced at older working age than at younger working age, so that the enhancement of transparency can serve as a means to mitigate age-related declines in performance. Benefits for the acquisition of an internal model of the transformation and of explicit knowledge were absent. Thus, open-loop control in this task did not profit from enhanced mechanical transparency. These findings strongly suggest that environmental support of transparency of the effects of input devices on controlled systems might be a powerful tool to support older users. Enhanced transparency may also improve simulator-based training by increasing motivation, even if training benefits do not transfer to situations without enhanced transparency.

  10. [Molecular Mechanisms of Functional Activity Decreasing of the Skin Cells With Its Aging].

    PubMed

    Khavinson, V Kh; Linkova, N S; Kukanova, E O; Orlova, O A

    2016-01-01

    The article discusses the pool of signaling molecules that regulate the functional activity of the skin cells. Molecules of apoptosis and cells skin aging are p53, p21, p15, Cdk 4/6 and Bcl-2. Inflammation in skin fibroblasts are realized through the cytokines TNF-α, TGF-β, IL-1, ICAM-1, matrix metalloproteinase MMP-1,2,3,9, transcription factor NF-κB and activator protein AP-1. An important role in the aging of skin cells play neuroimmunoendocrine signaling molecules--melatonin, serotonin, skin fibroblast proliferation marker chromogranin A and CD98hc. Age-related changes in the activity of immune cells of the skin is associated with impaired expression of cluster of differentiation of T-lymphocytes (CD3, CD4, CD5, CD8, CD11) and dendritic cells (CD83⁺). These signaling molecules produced by the fibroblasts of the skin, regulate the activity of immune cells involved in the cascade of reactions associated with inflammatory responses, proliferation, apoptosis and cell regeneration. Based on these data nowadays new highly selective approaches to the diagnosis of the skin and the creation of cosmetic agents for the prevention of aging are developed. PMID:27530044

  11. [Molecular Mechanisms of Functional Activity Decreasing of the Skin Cells With Its Aging].

    PubMed

    Khavinson, V Kh; Linkova, N S; Kukanova, E O; Orlova, O A

    2016-01-01

    The article discusses the pool of signaling molecules that regulate the functional activity of the skin cells. Molecules of apoptosis and cells skin aging are p53, p21, p15, Cdk 4/6 and Bcl-2. Inflammation in skin fibroblasts are realized through the cytokines TNF-α, TGF-β, IL-1, ICAM-1, matrix metalloproteinase MMP-1,2,3,9, transcription factor NF-κB and activator protein AP-1. An important role in the aging of skin cells play neuroimmunoendocrine signaling molecules--melatonin, serotonin, skin fibroblast proliferation marker chromogranin A and CD98hc. Age-related changes in the activity of immune cells of the skin is associated with impaired expression of cluster of differentiation of T-lymphocytes (CD3, CD4, CD5, CD8, CD11) and dendritic cells (CD83⁺). These signaling molecules produced by the fibroblasts of the skin, regulate the activity of immune cells involved in the cascade of reactions associated with inflammatory responses, proliferation, apoptosis and cell regeneration. Based on these data nowadays new highly selective approaches to the diagnosis of the skin and the creation of cosmetic agents for the prevention of aging are developed.

  12. Differences in Binding and Monitoring Mechanisms Contribute to Lifespan Age Differences in False Memory

    ERIC Educational Resources Information Center

    Fandakova, Yana; Shing, Yee Lee; Lindenberger, Ulman

    2013-01-01

    Based on a 2-component framework of episodic memory development across the lifespan (Shing & Lindenberger, 2011), we examined the contribution of memory-related binding and monitoring processes to false memory susceptibility in childhood and old age. We administered a repeated continuous recognition task to children (N = 20, 10-12 years),…

  13. The short-wavelength mechanisms of Stiles in age-related macular degeneration.

    PubMed

    Hubschman, J P; Vola, J L; Conrath, J; Berros, P; Hougrand, F

    1998-11-01

    Clinical measurements by the increment-threshold technique of W.S. Stiles are reported in five cases of age-related macular degeneration. Measurements were made on a modified Tübingen perimeter using 1 degree, short-wavelength targets presented on a red field.

  14. Effect of aging on mechanical properties of aluminum-alloy rivets

    NASA Technical Reports Server (NTRS)

    Roop, Frederick C

    1941-01-01

    Curves and tabular data present the results of strength tests made during and after 2 1/2 years of aging on rivets and rivet wire of 3/16-inch nominal diameter. The specimens were of aluminum alloy: 24S, 17S, and A17S of the duralumin type and 53S of the magnesium-silicide type.

  15. Pedagogy for Knowledge Recognition and Acquisition: Knowing and Being at the Close of the Mechanical Age

    ERIC Educational Resources Information Center

    Jaros, Milan

    2009-01-01

    It is the outstanding intellectual challenge of our age to find ways of providing citizens with access to and competent acquisition of the new applications and systems of knowledge. The purpose of this article is twofold. First, it is to justify at the conceptual level that we are facing an unprecedented shift in the way knowledge is generated and…

  16. Environmental pollutants and aging: Investigating and modeling mechanisms of susceptibility in later life.

    EPA Science Inventory

    The rapidly expanding population of older adults raises new concerns over their potential vulnerability to environmental pollutants. Decreases in organ-system function and defenses, coupled with reduced metabolic capacity and clearance, are likely mechanisms for enhanced vulnerab...

  17. Ti-Mo alloys employed as biomaterials: effects of composition and aging heat treatment on microstructure and mechanical behavior.

    PubMed

    Cardoso, Flavia F; Ferrandini, Peterson L; Lopes, Eder S N; Cremasco, Alessandra; Caram, Rubens

    2014-04-01

    The correlation between the composition, aging heat treatments, microstructural features and mechanical properties of β Ti alloys is of primary significance because it is the foundation for developing and improving new Ti alloys for orthopedic biomaterials. However, in the case of Ti-Mo alloys, this correlation is not fully described in the literature. Therefore, the purpose of this study was to experimentally investigate the effect of composition and aging heat treatments on the microstructure, Vickers hardness and elastic modulus of Ti-Mo alloys. These alloys were solution heat-treated and water-quenched, after which their response to aging heat treatments was investigated. Their microstructure, Vickers hardness and elastic modulus were evaluated, and the results allow us to conclude that stabilization of the β phase is achieved with nearly 10% Mo when a very high cooling rate is applied. Young's modulus was found to be more sensitive to phase variations than hardness. In all of the compositions, the highest hardness values were achieved by aging at 723K, which was attributed to the precipitation of α and ω phases. All of the compositions aged at 573K, 623K and 723K showed overaging within 80h.

  18. Adaptation of Diaphyseal Structure with Aging and Increased Mechanical Usage in the Adult Rat: A Histomorphometrical and Biomechanical Study

    NASA Technical Reports Server (NTRS)

    Jee, Webster S. S.; Li, Xiao Jian; Schaffler, Mitchell B.

    1991-01-01

    The experimental increase in mechanical usage or overloading of the left hindlimb was produced by immobilization of the contralateral hindlimb. The right hindlimb was placed in a flexed position against the body and was immobilized using an elastic bandage. Some control animals were sacrificed initially at time zero and increased mechanical usage and age-matched control animals were sacrificed after 2, 10, 18, and 26 weeks of treatment. All animals received double bone fluorochrome labeling prior to sacrifice. Cortical bone histomorphometry and cross-sectional moments of inertia were determined. Marrow cavity enlargement and total cross-sectional area expansion represented the age-related cortical bone changes. Increased mechanical usage enhanced periosteal bone modeling in the formation mode and dampened endocortical bone remodeling and bone modeling in the resorption mode (resorption drift) to create a slight positive bone balance. These observations are in general agreement with Frost's postulate for mechanical effects on bone modeling and remodeling. The maximum moment of inertia did not change significantly in either control or overloaded tibial shafts. The minimum and polar moment of inertias in overloaded bones increases over those of controls at 18 and 26 weeks of the experiment.

  19. Adaptation of Diaphyseal Structure With Aging and Increased Mechanical Usage in the Adult Rat: A Histomorphometrical and Biomechanical Study

    NASA Technical Reports Server (NTRS)

    Jee, Webster S. S.; Li, Xiao Jian; Schaffler, Mitchell B.

    1991-01-01

    The experimental increase in mechanical usage or overloading of the left hindlimb was produced by immobilization of the contralateral hindlimb. The right hindlimb was placed in a flexed position against the body and was immobilized using an elastic bandage. Some control animals were sacrificed initially at time zero and increased mechanical usage and age-matched control animals were sacrificed after 2, 10, 18, and 26 weeks of treatment. All animals received double bone fluorochrome labeling prior to sacrifice. Cortical bone histomorphometry and cross-sectional moments of inertia were determined. Marrow cavity enlargement and total cross-sectional area expansion represented the age-related cortical bone changes. Increased mechanical usage enhanced periosteal bone modeling in the formation mode and dampened endocortical bone remodeling and bone modeling in the resorption mode (resorption drift) to create a slight positive bone balance. These observations are in general agreement with Frost's postulate for mechanical effects on bone modeling and remodeling. The maximum moment of inertia did not change significantly in either control or overloaded tibial shafts. The minimum and polar moment of inertias in overloaded bones increases over those of controls at 18 and 26 weeks of the experiment.

  20. Mechanical property changes of barium titanate (ceramic) after in vivo and in vitro aging.

    PubMed

    Park, J B; Kenner, G H; Brown, S D; Scott, J K

    1977-01-01

    Since barium titanate (BaTi03) can be made piezoelectric, it may be used to substitute hard tissues directly. As a first step in testing this concept, a series of in vivo and in vitro aging and biocompatibility studies were performed. The mean compressive strength of samples implanted subcutaneously in the backs of rabbits decreased to 138 MPa after 20 weeks from a control value of 281 MPa. Similar, though less drastic losses of strength were seen when specimens were aged in distilled water (182 MPa at 28 weeks) and Ringer's solution (159 MPa at 28 weeks). The most rapid decrease of strength in all cases was seen prior to 4 weeks. Thereafter, the decrease was much slower. Histological evaluation of the tissue surrounding the implant revealed a thin fibrous capsule and no evidence of tissue inflammation.

  1. Mechanism of age-related changes of bone marrow mesenchymal stem cells in senile osteoporosis.

    PubMed

    Huang, C; Zhang, G F; Han, J; Liao, G J; Zou, B G

    2016-01-01

    This study was carried out to explore the age-related changes of bone marrow mesenchymal stem cells (BMMSCs) in mice as well as the influence of autophagy on the age-related changes of BMMSCs. BMMSCs aging-associated protein acetylation P53, P21 and P16 expressions in young and senile mice, protein expression of telomerase reverse transcriptase (TERT) as well as reactive oxygen species (ROS) level were detected and compared; the expression of BMMSCs autophagy associated gene, autophagy related protein molecule and LC3 molecule were detected; the influence of differently concentrated rapamycin and 3-MA on BMMSCs autophagy level was observed to select effective concentrations; the influence of rapamycin and 3-MA on BMMSCs cell cycle-related gene expression, apoptosis related gene expression and ROS level were discussed. Results revealed that the senile BMMSCs group had higher acetylation P53, P21 and P16 expression and fluorescence intensity than the young group, but its TERT expression, Beclin1 and LC3 gene expression and fluorescence intensity were lower than the young group. Both rapamycin and 3-MA inhibited CyclinD1 (CCND1) and CyclinD2 (CCND2) expression. Rapamycin promoted the expression of apoptosis-related genes Caspase3 and Caspase8 in the senile group, while 3-MA inhibited them in both the young and senile groups. It can therefore be concluded that senile BMMSCs have multiple age-related changes, performing as decrease of osteogenic capability and multiplication capacity, increase of acetylation P53, P21 and P16 protein expression, apoptosis and ROS level as well as decrease of telomerase activity. Furthermore, the autophagy level in senile BMMSCs reduced compared with young cells; autophagy activation can decrease ROS level and autophagy suppression improves ROS level; and autophagy regulation affects cell cycle and apoptosis. PMID:27358149

  2. Mechanisms of Heavy Metal Sequestration in Soils: Plant-Microbe Interactions and Organic Matter Aging

    SciTech Connect

    Teresa W.-M. Fan; Richard M. Higashi; David Crowley; Andrew N. Lane: Teresa A. Cassel; Peter G. Green

    2004-12-31

    For stabilization of heavy metals at contaminated sites, the three way interaction among soil organic matter (OM)-microbes-plants, and their effect on heavy metal binding is critically important for long-term sustainability, a factor that is poorly understood at the molecular level. Using a soil aging system, the humification of plant matter such as wheat straw was probed along with the effect on microbial community on soil from the former McClellan Air Force Base.

  3. Future Expectations of Brasilian Street Youth

    ERIC Educational Resources Information Center

    Raffaelli, M.; Koller, S.H.

    2005-01-01

    Future expectations of youth surviving on the streets of Porto Alegre, Brasil, were examined. The sample consisted of 35 boys and 34 girls aged 10-18 (M age 14.4) who participated in a sentence completion task and semi-structured interviews. Responses to two incomplete sentences regarding the future revealed a mismatch between hoped-for and…

  4. Performance expectation plan

    SciTech Connect

    Ray, P.E.

    1998-09-04

    This document outlines the significant accomplishments of fiscal year 1998 for the Tank Waste Remediation System (TWRS) Project Hanford Management Contract (PHMC) team. Opportunities for improvement to better meet some performance expectations have been identified. The PHMC has performed at an excellent level in administration of leadership, planning, and technical direction. The contractor has met and made notable improvement of attaining customer satisfaction in mission execution. This document includes the team`s recommendation that the PHMC TWRS Performance Expectation Plan evaluation rating for fiscal year 1998 be an Excellent.

  5. Modification of DNA by reducing sugars: a possible mechanism for nucleic acid aging and age-related dysfunction in gene expression.

    PubMed

    Bucala, R; Model, P; Cerami, A

    1984-01-01

    Reducing sugars react nonenzymatically with protein amino groups to initiate a process called nonenzymatic browning. Long-lived proteins, such as collagen and the lens crystallins, accumulate sufficient modification in vivo that they acquire many of the chemical properties characteristic of aged proteins. We have obtained evidence that nucleic acids also can undergo nonenzymatic modification by sugars. Incubation of DNA or nucleotides with glucose 6-phosphate (Glc-6-P) produces spectral changes similar to those described for nonenzymatic browning proteins. The occurrence of chemical modification was verified by measuring the transfection efficiency of viral DNA after incubation with glucose and Glc-6-P. A loss of transfection potential occurred that was first order with respect to time and sugar concentration. The rate of inactivation by Glc-6-P was 25 times that of glucose; 8 days of incubation with 150 mM Glc-6-P decreased transfection by 4 orders of magnitude. Glc-6-P also produced strand scission in a time- and concentration-dependent manner. We conclude that glucose, Glc-6-P, and possibly other sugars can react with DNA to produce significant structural and biological alterations. Since nucleic acids are long-lived molecules in the resting cell, the accumulation of these addition products might be a mechanism for the decreased genetic viability characteristic of the aged organism. PMID:6582469

  6. Fracture and mechanical stratigraphy for Mississippian-Pennsylvanian age carbonates, Ozark Dome, NW Arkansas

    NASA Astrophysics Data System (ADS)

    Peppers, M.; Burberry, C. M.

    2014-12-01

    Identifying natural fracture patterns in an area gives a detailed look into the local tectonic history. Comparing those fractures to the mechanical properties of the rocks provides key insights into predicting fractures in the subsurface. The Ozark Dome is an ideal study area for fracture research due to multiple fracturing events resulting from the multi-stage deformation Ouachita Orogeny during the late Paleozoic. This study used field observations of lithology and fracture attributes over ~10 outcrops in the Mississppian-Pennsylvanian (360-298 ma) carbonate sequence of the Ozark Plateau. Outcrops were chosen having excellent lithological exposure up the sequence from the Boone to Atoka formations and with 3D representations of the fracture patterns. In all, the area investigated covered nearly 60 square miles. Fracture attributes collected included fracture intensity, length, and abutting relationships; and rock hardness data collected from a Schmidt Hammer. Data was analyzed using programs such as Stereonet and MOVE structural software that generated rose diagrams, structural cross sections, and products. Initial results indicate 4 main fracture orientations that resulted from at least 3 discrete phases of deformation during the Miss-Penn. Initial results also indicate that the present-day mechanical stratigraphy is not the same one that existed during the deformation phases. Work done at the Tiger Blvd. outcrops showed at least 2 distinct mechanical units. Fractures observed at the outcrop did not respect mechanical bed boundaries, and showed no relationship to the differences in mechanical properties observed. This study will aid in the interpretation of fractures in regards to mechanical stratigraphy, which allows for a better understanding of subsurface fracture prediction in carbonate sequences worldwide. Finally, the fracture work here will also help in elucidating the tectonic history of the field area during the Mississippian and Pennsylvanian.

  7. Contribution of Quantitative Methods of Estimating Mortality Dynamics to Explaining Mechanisms of Aging.

    PubMed

    Shilovsky, G A; Putyatina, T S; Markov, A V; Skulachev, V P

    2015-12-01

    Accumulation of various types of unrepaired damage of the genome because of increasing production of reactive oxygen species and decreasing efficiency of the antioxidant defense system and repair systems can cause age-related diseases and emergence of phenotypic signs of senescence. This should lead to increasing vulnerability and to mortality monotonously increasing with age independently of the position of the species on the evolutionary tree. In this light, the survival, mortality, and fertility curves for 45 animal and plant species and one alga published by the Max Planck Institute for Demographic Research (Germany/Denmark) are of special interest (Jones, O. R., et al. (2014) Nature, 505, 169-173). We divided all species treated in that study into four groups according to the ratio of mortality at the terminal age (which corresponds to 5% survival) and average mortality during the entire studied period. For animals of group IV (long-lived and senescent), including humans, the Jones method makes it possible to trace mortality during the entire life cycle. The same applies to short-lived animals (e.g. nematodes or the tundra vole), whether they display the Gompertz type of senescence or not. However, in long-lived species with a less pronounced increase in mortality with age (e.g. the freshwater crocodile, hermit crab, or Scots pine), as well as in animals of average lifespan that reach the terminal age earlier than they could have enough time to become senescent, the Jones method is capable of characterizing only a small part of the life cycle and does not allow judging how senescence manifests itself at late stages of the life cycle. Thus, it is known that old trees display signs of biological senescence rather clearly; although Jones et al. consider them non-senescent organisms because less than 5% of sexually mature individuals survive to display the first manifestations of these characters. We have concluded that the classification proposed by Jones et al

  8. Biomimetic remineralization as a progressive dehydration mechanism of collagen matrices – implications in the aging of resin-dentin bonds

    PubMed Central

    Kim, Young Kyung; Mai, Sui; Mazzoni, Annalisa; Liu, Yan; Tezvergil-Mutluay, Arzu; Takahashi, Kei; Zhang, Kai; Pashley, David H.; Tay, Franklin R.

    2010-01-01

    Biomineralization is a dehydration process in which water from the intrafibrillar compartments of collagen fibrils are progressively replaced by apatites. As water is an important element that precipitates the lack of durability of resin-dentin bonds, this study examined the use of a biomimetic remineralization strategy as a progressive dehydration mechanism for preserving joint integrity and maintaining adhesive strength after aging. Human dentin surfaces were bonded with dentin adhesives, restored with resin composites and sectioned into sticks containing the adhesive joint. Experimental specimens were aged in a biomimetic analog-containing remineralizing medium and control specimens in simulated body fluid for up to 12 months. Specimens retrieved from the designated periods were examined by transmission electron microscopy for manifestation of water-rich regions using a silver tracer and for collagen degradation within the adhesive joints. Tensile testing was performed to determine the potential loss of bond integrity after aging. Control specimens exhibited severe collagen degradation within the adhesive joint after aging. Remineralized specimens exhibited progressive dehydration as manifested by silver tracer reduction and partial remineralization of water-filled micro-channels within the adhesive joint, as well as intrafibrillar remineralization of collagen fibrils that were demineralized initially as part of the bonding procedure. Biomimetic remineralization as a progressive dehydration mechanism of water-rich, resin-sparse collagen matrices enables those adhesive joints to resist degradation over the 12-month aging period, as verified by the conservation of their tensile bond strengths. The ability of the proof-of-concept biomimetic remineralization strategy to prevent bond degradation warrants further development of clinically-relevant delivery systems. PMID:20304110

  9. Aging enhances a mechanically-induced reduction in tendon strength by an active process involving matrix metalloproteinase activity.

    PubMed

    Dudhia, Jayesh; Scott, Charlotte M; Draper, Edward R C; Heinegård, Dick; Pitsillides, Andrew A; Smith, Roger K

    2007-08-01

    Age-associated and degenerative loss of functional integrity in soft tissues develops from effects of cumulative and subtle changes in their extracellular matrix (ECM). The highly ordered tendon ECM provides the tissue with its tensile strength during loading. As age and exercise collide in the high incidence of tendinopathies, we hypothesized that aged tendons fail due to cumulative damage resulting from a combination of diminished matrix repair and fragmentation of ECM proteins induced by prolonged cyclical loading, and that this is an active cell-mediated process. We developed an equine tendon explant model to examine the effect of age on the influence of prolonged cyclical loading at physiologically relevant strain rates (5% strain, 1 Hz for 24 h) on tissue mechanical properties, loss of ECM protein and matrix metalloproteinase (MMP) expression. We show significantly diminished mechanical strength of cyclically loaded tissue compared to controls (39.7 +/- 12%, P age, via load-induced proteolytic disruption of the ECM.

  10. Great Expectations. [Lesson Plan].

    ERIC Educational Resources Information Center

    Devine, Kelley

    Based on Charles Dickens' novel "Great Expectations," this lesson plan presents activities designed to help students understand the differences between totalitarianism and democracy; and a that a writer of a story considers theme, plot, characters, setting, and point of view. The main activity of the lesson involves students working in groups to…

  11. Behavior, Expectations and Status

    ERIC Educational Resources Information Center

    Webster, Jr, Murray; Rashotte, Lisa Slattery

    2010-01-01

    We predict effects of behavior patterns and status on performance expectations and group inequality using an integrated theory developed by Fisek, Berger and Norman (1991). We next test those predictions using new experimental techniques we developed to control behavior patterns as independent variables. In a 10-condition experiment, predictions…

  12. Maintaining High Expectations

    ERIC Educational Resources Information Center

    Williams, Roger; Williams, Sherry

    2014-01-01

    Author and husband, Roger Williams, is hearing and signs fluently, and author and wife, Sherry Williams, is deaf and uses both speech and signs, although she is most comfortable signing. As parents of six children--deaf and hearing--they are determined to encourage their children to do their best, and they always set their expectations high. They…

  13. Parenting with High Expectations

    ERIC Educational Resources Information Center

    Timperlake, Benna Hull; Sanders, Genelle Timperlake

    2014-01-01

    In some ways raising deaf or hard of hearing children is no different than raising hearing children; expectations must be established and periodically tweaked. Benna Hull Timperlake, who with husband Roger, raised two hearing children in addition to their deaf daughter, Genelle Timperlake Sanders, and Genelle, now a deaf professional, share their…

  14. Prior expectations facilitate metacognition for perceptual decision.

    PubMed

    Sherman, M T; Seth, A K; Barrett, A B; Kanai, R

    2015-09-01

    The influential framework of 'predictive processing' suggests that prior probabilistic expectations influence, or even constitute, perceptual contents. This notion is evidenced by the facilitation of low-level perceptual processing by expectations. However, whether expectations can facilitate high-level components of perception remains unclear. We addressed this question by considering the influence of expectations on perceptual metacognition. To isolate the effects of expectation from those of attention we used a novel factorial design: expectation was manipulated by changing the probability that a Gabor target would be presented; attention was manipulated by instructing participants to perform or ignore a concurrent visual search task. We found that, independently of attention, metacognition improved when yes/no responses were congruent with expectations of target presence/absence. Results were modeled under a novel Bayesian signal detection theoretic framework which integrates bottom-up signal propagation with top-down influences, to provide a unified description of the mechanisms underlying perceptual decision and metacognition.

  15. The neural mechanisms underlying the aging-related enhancement of positive affects: electrophysiological evidences

    PubMed Central

    Meng, Xianxin; Yang, Jiemin; Cai, AYan; Ding, XinSheng; Liu, Wenwen; Li, Hong; Yuan, JiaJin

    2015-01-01

    Background: Previous studies reported that old adults, relative to young adults, showed improvement of emotional stability and increased experiences of positive affects. Methods: In order to better understand the neural underpinnings behind the aging-related enhancement of positive affects, it is necessary to investigate whether old and young adults differ in the threshold of eliciting positive or negative emotional reactions. However, no studies have examined emotional reaction differences between old and young adults by manipulating the intensity of emotional stimuli to date. To clarify this issue, the present study examined the impact of aging on the brain’s susceptibility to affective pictures of varying emotional intensities. We recorded event-related potentials (ERP) for highly negative (HN), mildly negative (MN) and neutral pictures in the negative experimental block; and for highly positive (HP), mildly positive (MP) and neutral pictures in the positive experimental block, when young and old adults were required to count the number of pictures, irrespective of the emotionality of the pictures. Results: Event-related potentials results showed that LPP (late positive potentials) amplitudes were larger for HN and MN stimuli compared to neutral stimuli in young adults, but not in old adults. By contrast, old adults displayed larger LPP amplitudes for HP and MP relative to neutral stimuli, while these effects were absent for young adults. In addition, old adults reported more frequent perception of positive stimuli and less frequent perception of negative stimuli than young adults. The post-experiment stimulus assessment showed more positive ratings of Neutral and MP stimuli, and reduced arousal ratings of HN stimuli in old compared to young adults. Conclusion: These results suggest that old adults are more resistant to the impact of negative stimuli, while they are equipped with enhanced attentional bias for positive stimuli. The implications of these results

  16. Eight Common Genetic Variants Associated with Serum DHEAS Levels Suggest a Key Role in Ageing Mechanisms

    PubMed Central

    Bell, Jordana T.; Bhasin, Shalender; Eriksson, Joel; Eriksson, Anna; Ernst, Florian; Ferrucci, Luigi; Frayling, Timothy M.; Glass, Daniel; Grundberg, Elin; Haring, Robin; Hedman, Åsa K.; Hofman, Albert; Kiel, Douglas P.; Kroemer, Heyo K.; Liu, Yongmei; Lunetta, Kathryn L.; Maggio, Marcello; Lorentzon, Mattias; Mangino, Massimo; Melzer, David; Miljkovic, Iva; Nica, Alexandra; Penninx, Brenda W. J. H.; Vasan, Ramachandran S.; Rivadeneira, Fernando; Small, Kerrin S.; Soranzo, Nicole; Uitterlinden, André G.; Völzke, Henry; Wilson, Scott G.; Xi, Li; Zhuang, Wei Vivian; Harris, Tamara B.; Murabito, Joanne M.; Ohlsson, Claes; Murray, Anna; de Jong, Frank H.; Spector, Tim D.; Wallaschofski, Henri

    2011-01-01

    Dehydroepiandrosterone sulphate (DHEAS) is the most abundant circulating steroid secreted by adrenal glands—yet its function is unknown. Its serum concentration declines significantly with increasing age, which has led to speculation that a relative DHEAS deficiency may contribute to the development of common age-related diseases or diminished longevity. We conducted a meta-analysis of genome-wide association data with 14,846 individuals and identified eight independent common SNPs associated with serum DHEAS concentrations. Genes at or near the identified loci include ZKSCAN5 (rs11761528; p = 3.15×10−36), SULT2A1 (rs2637125; p = 2.61×10−19), ARPC1A (rs740160; p = 1.56×10−16), TRIM4 (rs17277546; p = 4.50×10−11), BMF (rs7181230; p = 5.44×10−11), HHEX (rs2497306; p = 4.64×10−9), BCL2L11 (rs6738028; p = 1.72×10−8), and CYP2C9 (rs2185570; p = 2.29×10−8). These genes are associated with type 2 diabetes, lymphoma, actin filament assembly, drug and xenobiotic metabolism, and zinc finger proteins. Several SNPs were associated with changes in gene expression levels, and the related genes are connected to biological pathways linking DHEAS with ageing. This study provides much needed insight into the function of DHEAS. PMID:21533175

  17. Human aneuploidy: mechanisms and new insights into an age-old problem

    PubMed Central

    Nagaoka, So I.; Hassold, Terry J.; Hunt, Patricia A.

    2012-01-01

    Trisomic and monosomic (aneuploid) embryos account for at least 10% of human pregnancies and, for women nearing the end of their reproductive lifespan, the incidence may exceed 50%. The errors that lead to aneuploidy almost always occur in the oocyte but, despite intensive investigation, the underlying molecular basis has remained elusive. Recent studies of humans and model organisms have shed new light on the complexity of meiotic defects, providing evidence that the age-related increase in errors in the human female is not attributable to a single factor but to an interplay between unique features of oogenesis and a host of endogenous and exogenous factors. PMID:22705668

  18. PSYCHIATRIC DISORDERS AND LEUKOCYTE TELOMERE LENGTH: UNDERLYING MECHANISMS LINKING MENTAL ILLNESS WITH CELLULAR AGING

    PubMed Central

    Lindqvist, Daniel; Epel, Elissa S.; Mellon, Synthia H.; Penninx, Brenda W.; Révész, Dóra; Verhoeven, Josine E.; Reus, Victor I.; Lin, Jue; Mahan, Laura; Hough, Christina M.; Rosser, Rebecca; Bersani, F. Saverio; Blackburn, Elizabeth H.; Wolkowitz, Owen M.

    2015-01-01

    Many psychiatric illnesses are associated with early mortality and with an increased risk of developing physical diseases that are more typically seen in the elderly. Moreover, certain psychiatric illnesses may be associated with accelerated cellular aging, evidenced by shortened leukocyte telomere length (LTL), which could underlie this association. Shortened LTL reflects a cell’s mitotic history and cumulative exposure to inflammation and oxidation as well as the availability of telomerase, a telomere-lengthening enzyme. Critically short telomeres can cause cells to undergo senescence, apoptosis or genomic instability, and shorter LTL correlates with poorer health and predicts mortality. Emerging data suggest that LTL may be reduced in certain psychiatric illnesses, perhaps in proportion to exposure to the psychiatric illnesses, although conflicting data exist. Telomerase has been less well characterized in psychiatric illnesses, but a role in depression and in antidepressant and neurotrophic effects has been suggested by preclinical and clinical studies. In this article, studies on LTL and telomerase activity in psychiatric illnesses are critically reviewed, potential mediators are discussed, and future directions are suggested. A deeper understanding of cellular aging in psychiatric illnesses could lead to re-conceptualizing them as systemic illnesses with manifestations inside and outside the brain and could identify new treatment targets. PMID:25999120

  19. Mechanisms and biological functions of autophagy in diseased and ageing kidneys.

    PubMed

    Fougeray, Sophie; Pallet, Nicolas

    2015-01-01

    Autophagy degrades pathogens, altered organelles and protein aggregates, and is characterized by the sequestration of cytoplasmic cargos within double-membrane-limited vesicles called autophagosomes. The process is regulated by inputs from the cellular microenvironment, and is activated in response to nutrient scarcity and immune triggers, which signal through a complex molecular network. Activation of autophagy leads to the formation of an isolation membrane, recognition of cytoplasmic cargos, expansion of the autophagosomal membrane, fusion with lysosomes and degradation of the autophagosome and its contents. Autophagy maintains cellular homeostasis during stressful conditions, dampens inflammation and shapes adaptive immunity. A growing body of evidence has implicated autophagy in kidney health, ageing and disease; it modulates tissue responses during acute kidney injuries, regulates podocyte homeostasis and protects against age-related renal disorders. The renoprotective functions of autophagy in epithelial renal cells and podocytes are mostly mediated by the clearance of altered mitochondria, which can activate inflammasomes and apoptosis, and the removal of protein aggregates, which might trigger inflammation and cell death. In translational terms, autophagy is undoubtedly an attractive target for developing new renoprotective treatments and identifying markers of kidney injury. PMID:25385287

  20. The Circadian Timing System: A Recent Addition in the Physiological Mechanisms Underlying Pathological and Aging Processes

    PubMed Central

    Arellanes-Licea, Elvira; Caldelas, Ivette; De Ita-Pérez, Dalia; Díaz-Muñoz, Mauricio

    2014-01-01

    Experimental findings and clinical observations have strengthened the association between physio-pathologic aspects of several diseases, as well as aging process, with the occurrence and control of circadian rhythms. The circadian system is composed by a principal pacemaker in the suprachiasmatic nucleus (SNC) which is in coordination with a number of peripheral circadian oscillators. Many pathological entities such as metabolic syndrome, cancer and cardiovascular events are strongly connected with a disruptive condition of the circadian cycle. Inadequate circadian physiology can be elicited by genetic defects (mutations in clock genes or circadian control genes) or physiological deficiencies (desynchronization between SCN and peripheral oscillators). In this review, we focus on the most recent experimental findings regarding molecular defects in the molecular circadian clock and the altered coordination in the circadian system that are related with clinical conditions such as metabolic diseases, cancer predisposition and physiological deficiencies associated to jet-lag and shiftwork schedules. Implications in the aging process will be also reviewed. PMID:25489492

  1. Temperature, age and crust thickness distributions of Loki Patera on Io: implications for resurfacing mechanism

    NASA Technical Reports Server (NTRS)

    Davies, A. G.

    2003-01-01

    A high-spatial-resolution, multi-wavelength observation by the Galileo NIMS instrument has been analysed to determine the temperature and area distribution of a large portion of the ionian volcano Loki Patera. The temperatures of the cooler components from a two-temperature fit to the data can be used to determine ages of the surface. The age of the floor along a profile across the floor of the caldera ranges from 10 to 80 days. This puts the start of the resurfacing in July/early August 2001, yielding a resurfacing rate of approximately 1 km/day, with the new lava spreading from the SW corner of the caldera in a NE direction. This rate is consistent with resurfacing by foundering of the crust on a lava lake. However,the temperature distribution may also result from the emplacement of flows. Implied crust thicknesses (derived using a lava cooling model) range from 2.6 to 0.9 m.

  2. AMPA receptor trafficking and the mechanisms underlying synaptic plasticity and cognitive aging.

    PubMed

    Henley, Jeremy M; Wilkinson, Kevin A

    2013-03-01

    Even in healthy individuals there is an inexorable agerelated decline in cognitive function. This is due, in large part, to reduced synaptic plasticity caused by changes in the molecular composition of the postsynaptic membrane. AMPA receptors (AMPARs) are glutamate-gated cation channels that mediate the overwhelming majority of fast excitatory transmission in the brain. Changes in AMPAR number and/or function are a core feature of synaptic plasticity and age-related cognitive decline, AMPARs are highly dynamic proteins that are subject to highly controlled trafficking, recycling, and/or degradation and replacement. This active regulation of AMPAR synthesis, targeting, synaptic dwell time, and degradation is fundamentally important for memory formation and storage. Further, aberrant AMPAR trafficking and consequent detrimental changes in synapses are strongly implicated in many brain diseases, which represent a vast social and economic burden. The purpose of this article is to provide an overview of the molecular and cellular AMPA receptor trafficking events that control synaptic responsiveness and plasticity, and highlight what is known currently known about how these processes change with age and disease.

  3. AMPA receptor trafficking and the mechanisms underlying synaptic plasticity and cognitive aging

    PubMed Central

    Henley, Jeremy M.; Wilkinson, Kevin A.

    2013-01-01

    Even in healthy individuals there is an inexorable agerelated decline in cognitive function. This is due, in large part, to reduced synaptic plasticity caused by changes in the molecular composition of the postsynaptic membrane. AMPA receptors (AMPARs) are glutamate-gated cation channels that mediate the overwhelming majority of fast excitatory transmission in the brain. Changes in AMPAR number and/or function are a core feature of synaptic plasticity and age-related cognitive decline, AMPARs are highly dynamic proteins that are subject to highly controlled trafficking, recycling, and/or degradation and replacement. This active regulation of AMPAR synthesis, targeting, synaptic dwell time, and degradation is fundamentally important for memory formation and storage. Further, aberrant AMPAR trafficking and consequent detrimental changes in synapses are strongly implicated in many brain diseases, which represent a vast social and economic burden. The purpose of this article is to provide an overview of the molecular and cellular AMPA receptor trafficking events that control synaptic responsiveness and plasticity, and highlight what is known currently known about how these processes change with age and disease. PMID:23576886

  4. Self-oscillating Vocal Fold Model Mechanics: Healthy, Diseased, and Aging

    NASA Astrophysics Data System (ADS)

    Hiubler, Elizabeth P.; Pollok, Lucas F. E.; Apostoli, Adam G.; Hancock, Adrienne B.; Plesniak, Michael W.

    2014-11-01

    Voice disorders have been estimated to have a substantial economic impact of 2.5 billion annually. Approximately 30% of people will suffer from a voice disorder at some point in their lives. Life-sized, self-oscillating, synthetic vocal fold (VF) models are fabricated to exhibit material properties representative of human VFs. These models are created both with and without a polyp-like structure, a pathology that has been shown to produce rich viscous flow structures not normally observed for healthy VFs during normal phonation. Pressure measurements are acquired upstream of the VFs and high-speed images are captured at varying flow rates during VF oscillation to facilitate an understanding of the characteristics of healthy and diseased VFs. The images are analyzed using a videokymography line-scan technique. Clinically-relevant parameters calculated from the volume-velocity output of a circumferentially-vented mask (Rothenberg mask) are compared to human data collected from two groups of males aged 18-30 and 60-80. This study extends the use of synthetic VF models by assessing their ability to replicate behaviors observed in human subject data to advance a means of investigating changes associated with normal, pathological, and the aging voice. Supported by the GWU Institute for Biomedical Engineering (GWIBE) and GWU Center for Biomimetics and Bioinspired Engineering (COBRE).

  5. In vitro mechanical properties of the accessory ligament of the deep digital flexor tendon in horses in relation to age.

    PubMed

    Becker, C K; Savelberg, H H; Barneveld, A

    1994-11-01

    The material properties of the accessory ligament of the deep digital flexor tendon (AL) of 21 forelimbs from horses between ages one day and 15 years were determined. The force (634-11416 N), failure stress (45-138 N/mm2), failure strain (7-24%) and tangent modulus (33-1639 MPa) are presented in relation to age. Tangent modulus did not indicate changes in elasticity due to age. The results demonstrate that complete ligament failures (CLF) of ALs of older horses (mean 7835 N) occur at lower forces than ALs of young adult horses (mean 8894 N). Sudden decreases, 'dips', in the force-time curves were noticed in ligaments from foals and yearlings and in ligaments from horses > 10 years. They were interpreted as the failure of a number of fibres which either fail at lower forces or are subject to higher forces than the rest. These differences in mechanical properties could be the result of age related differences in the material properties of ALs of older horses similar to alterations in collagenous tissue in other species. When analysing the data of the proximal, middle and distal regions of the ligaments separately, higher strain and elasticity were found in the distal compared to the proximal parts. It is suggested that the clinical occurrence of desmitis of the AL of older horses could be due to fibrillar failure caused by differences in the material properties of the ligaments.

  6. Investigation of path dependence in commercial lithium-ion cells for pure electric bus applications: Aging mechanism identification

    NASA Astrophysics Data System (ADS)

    Ma, Zeyu; Jiang, Jiuchun; Shi, Wei; Zhang, Weige; Mi, Chunting Chris

    2015-01-01

    There is a growing need to provide more realistic and accurate State of Health estimations for batteries in electric vehicles. Thus, it is necessary to research various lithium-ion cell aging processes, including cell degradation and related path dependence. This paper focuses on quantitative analyses of cell aging path dependence in a repeatable laboratory setting, considering the influence of duty cycles, depth of discharge (DOD), and the frequency and severity of the thermal cycle, as reflected in pure electric buses operated in Beijing. Incremental capacity analysis (ICA) and differential voltage analysis (DVA) are applied to infer cell degradation mechanisms and quantify the attributions to capacity fade. It was observed that the cells experienced a higher rate of aging at 80% DOD and an accelerated aging at 40 °C in the thermal cycling, as a result of possible loss of active material (LAM) in both electrodes, in addition to the loss of lithium inventory (LLI) and inhibited kinetics. The slight capacity fade from low-temperature extremes likely caused by LLI due to lithium plating, whereas the noticeable fade after the high-temperature excursion was likely caused by LAM and hindrance to kinetics. These results may lead to improved battery management in EV applications.

  7. Mechanical properties of the human hand digits: Age-related differences

    PubMed Central

    Park, Jaebum; Pazin, Nemanja; Friedman, Jason; Zatsiorsky, Vladimir M.; Latash, Mark L.

    2014-01-01

    Background Mechanical properties of human digits may have significant implications for the hand function. We quantified several mechanical characteristics of individual digits in young and older adults. Methods Digit tip friction was measured at several normal force values using a method of induced relative motion between the digit tip and the object surface. A modified quick-release paradigm was used to estimate digit apparent stiffness, damping, and inertial parameters. The subjects grasped a vertical handle instrumented with force/moment sensors using a prismatic grasp with four digits; the handle was fixed to the table. Unexpectedly, one of the sensors yielded leading to a quick displacement of the corresponding digit. A second-order, linear model was used to fit the force/displacement data. Findings Friction of the digit pads was significantly lower in older adults. The apparent stiffness coefficient values were higher while the damping coefficients were lower in older adults leading to lower damping ratio. The damping ratio was above unity for most data in young adults and below unity for older adults. Quick release of a digit led to force changes in other digits of the hand, likely due to inertial hand properties. These phenomena of “mechanical enslaving” were smaller in older adults although no significant difference was found in the inertial parameter in the two groups. Interpretations The decreased friction and damping ratio present challenges for the control of everyday prehensile tasks. They may lead to excessive digit forces and low stability of the grasped object. PMID:24355703

  8. Attenuation of rat ischemic brain damage by aged garlic extracts: a possible protecting mechanism as antioxidants.

    PubMed

    Numagami, Y; Sato, S; Ohnishi, S T

    1996-08-01

    Effects of an aged garlic extract and its thioallyl components on rat brain ischemia were examined using a middle cerebral artery occlusion model and a transient global ischemia model. In focal ischemia, an aged garlic extract, S-allyl cysteine (SAC), Allyl sulfide (AS) or Allyl disulfide (ADS) was administered 30 min prior to ischemic insult. Three days after ischemic insult, water contents of both ischemic and contralateral hemispheres were measured to assess the degree of ischemic damage. The water content of the ischemic control (no drug treatment) group was 81.50 +/- 0.07% (mean +/- SEM). It was significantly reduced with the administration of 300 mg/kg of SAC; the water content was 80.66 +/- 0.11% (P < 0.001). The histological observation using 2,3,5-triphenyltetrazolium chloride staining demonstrated that the administration of SAC reduced infarct volume. Neither AS nor ADS was effective. In global ischemia, the production of reactive oxygen species (ROS) was measured ex vivo using a spin-trapping agent, alpha-phenyl-N-tert-butylnitrone, and electron paramagnetic resonance spectroscopy. The production of ROS had two peaks; first at 5 min and second at 20 min after reperfusion. Both SAC and 7-nitro indazole, a nitric oxide synthase inhibitor, did not attenuate the amount of ROS produced at the first peak, but did the amount of the second peak. A possible involvement of peroxinitrite, which may be formed from superoxide and nitric oxide and is known to be highly toxic in ischemia/reperfusion injury of the brain, was suggested.

  9. Dermal Aged and Fetal Fibroblasts Realign in Response to Mechanical Strain

    NASA Technical Reports Server (NTRS)

    Sawyer, Christine; Grymes, Rose; Alvarez, Teresa (Technical Monitor)

    1994-01-01

    Integrins specifically recognize and bind extracellular matrix components, providing physical anchor points and functional setpoints. Focal adhesion complexes, containing integrin and cytoskeletal proteins, are potential mechanoreceptors, poised to distribute applied forces through the cytoskeleton. Pursuing the hypothesis that cells both perceive and respond to external force, we applied a stretch/relaxation regimen to normal human fetal and aged dermal fibroblast monolayers cultured on flexible membranes. The frequency and magnitude of the applied force is precisely controlled by the Flexercell Unit(Trademark). A protocol of stretch (20% elongation of the monolayer) at a frequency of 6 cycles/min caused a progressive change from a randomly distributed pattern of cells to a symmetric, radial distribution with cells aligned parallel to the applied force. We have coined the term 'orienteering' as the process of active alignment of cells in response to applied force. Cytochalasin D was added in graded doses to investigate the role of the actin cytoskeleton in force perception and transmission. A clear dose response was found; at high concentrations orienteering was abolished; and the drug's impact was reversible. The two cell strains used were similar in their alignment behavior and in their responses to cytochalasin D. Orienteering was influenced by cell density, and the cell strains studied differed in this respect. Fetal cells, unlike their aged counterparts, failed to orient at high cell density. In both cell strains, mid-density cultures aligned rapidly and sparse cultures lagged. These results indicate that both cell-cell adhesion and cytoskeleton integrity are critical in mediating the orienteering response. Differences between these two cell strains may relate to their expression of extracellular matrix molecules (fibronectin, collagen type 1) integrins and their relative binding affinities.

  10. Dynamic mechanical thermal analysis of maxillofacial prosthetic elastomers: the effect of different disinfecting aging procedures.

    PubMed

    Eleni, Panagiota N; Krokida, Magdalini K; Polyzois, Gregory L; Gettleman, Lawrence

    2014-05-01

    In this study, dynamic mechanical thermal analysis was used to evaluate the changes that occurred in maxillofacial elastomers subjected to different disinfecting regimens. A commercial polydimethyl siloxane (PDMS) and an experimental chlorinated polyethylene (CPE) were treated with different disinfection procedures for a period that simulates 1 year of clinical service: microwave exposure (D1), hypochlorite solution (D2), neutral soap (D3), and a commercial disinfecting solution (D4). A fifth group was kept in dark storage as control. Dynamic mechanical thermal analysis tests operated in a fixed frequency (1 Hz) over a range of temperatures (-130°C to 20°C for PDMS, -60°C to 120°C for CPE). Loss modulus (G″), storage modulus (G'), and loss factor (tanδ) were recorded as a function of temperature. The obtained glass transition temperature (Tg) values were subjected to statistical analysis. Dynamic mechanical thermal analysis revealed changes in Tg values for both materials, which reflect the possible changes in their chemical and physical structure, after different disinfection procedures. The PDMS and CPE samples seem to have less dense structure maybe because of chain scission reaction that probably occurred during the disinfection procedures. According to statistical analysis, Tg values presented significant changes from the control samples among the different materials and disinfecting procedures. Microwave exposure and hypochlorite solution affect CPE significantly, whereas PDMS exhibited significant changes after being treated with a commercial antimicrobial agent, concerning changes that occurred in Tg. In all cases, Tg values were decreased compared with the untreated samples, which were stiffer, presenting higher Tg and G' values. PMID:24799103

  11. Hardening mechanisms in a dynamic strain aging alloy, Hastelloy X, during isothermal and thermomechanical cyclic deformation

    NASA Technical Reports Server (NTRS)

    Miner, R. V.; Castelli, M. G.

    1992-01-01

    The relative contributions of the hardening mechanisms in Hastelloy X during cyclic deformation were investigated by conducting isothermal cyclic deformation tests within a total strain range of +/-0.3 pct and at several temperatures and strain rates, and thermomechanical tests within several different temperature limits. The results of the TEM examinations and special constant structure tests showed that the precipitation on dislocations of Cr23C6 contributed to hardening, but only after sufficient time above 500 C. Solute drag alone produced very considerable cyclic hardening. Heat dislocation densities, peaking around 10 exp 11 per sq cm, were found to develop at temperatures producing the greatest cyclic hardening.

  12. Society's expectations of health

    PubMed Central

    Leach, Edmund

    1975-01-01

    Sir Edmund Leach argues that doctors in the modern world, fortified by the traditional concept that the life of the sick person must at all costs be preserved, are to some extent guilty of the false antitheses current today between youth and age. Moreover youth means health, age illness and senility. Until this imbalance is corrected society will be in danger of `a kind of civil war between the generations'. Society must be taught again that mortality cannot be avoided or conquered by medical science, and at the same time that `health' is not enshrined in the young alone. PMID:1177271

  13. Evaluation of stone durability using a combination of ultrasound, mechanical and accelerated aging tests

    NASA Astrophysics Data System (ADS)

    Molina, E.; Cultrone, G.; Sebastián, E.; Alonso, F. J.

    2013-06-01

    The durability of a rock when exposed to decay agents is an important criterion when assessing its quality as a building material. Our study focuses on six varieties of natural stone (two limestones, one dolostone, one travertine and two sandstones) that are widely used in both new and historical buildings. In order to assess their quality, we measured and characterized their dynamic elastic properties using ultrasounds, we measured their compressive strength using the uniaxial compression test and we evaluated their durability by means of accelerated aging tests (freeze-thaw and salt crystallization). In order to get a full picture of the decay suffered by the different stones, we determined the composition and amount of the clay fraction of the six stones. We also observed small fragments subjected to the salt crystallization test under an environmental scanning electron microscope to study any textural change and measured the changes of colour on the surface with a spectrophotometer. Finally, we analysed the pore system of the stones before and after their deterioration using mercury injection porosimetry. We then compared the results for the different stones and found that dolostone obtained the best results, while the two limestones proved to be the least durable and had the lowest compressive strength.

  14. Autonomous anorthosites of the Anabar Shield: Age, geochemistry, and formation mechanism

    NASA Astrophysics Data System (ADS)

    Glukhovskii, M. Z.; Kuz'min, M. I.; Bayanova, T. B.; Bazhenova, G. N.; Lyalina, L. M.; Serov, P. A.

    2015-10-01

    The new high-accuracy data on U-Pb zircon geochronology, Sm-Nd systematics, and geochemistry of anorthosites of the Anabar Shield are discussed. It is established that anorthosite massifs are composed of gabbro-anorthosites (1.96 Ga old) and oligoclasites (1.93 Ga old) in association with monzodiorites (1.84-1.90 Ga old) and porphyroblastic granites. These rocks were generated in the Archean (3.2-2.7 Ga ago) in the lower crust from quartz-diorite melts under the plume tectonics regime in line with the filterpressing mechanism. The rocks were successively exhumed to upper levels of the crust owing to the Paleoproterozoic impact-triggered process to form a tectonically juxtaposed complementary magmatic complex.

  15. Effects of alcohol intake on time-based event expectations.

    PubMed

    Kunchulia, Marina; Thomaschke, Roland

    2016-04-01

    Previous evidence suggests that alcohol affects various forms of temporal cognition. However, there are presently no studies investigating whether and how alcohol affects on time-based event expectations. Here, we investigated the effects of alcohol on time-based event expectations. Seventeen healthy volunteers, aged between 19 and 36 years, participated. We employed a variable foreperiod paradigm with temporally predictable events, mimicking a computer game. Error rate and reaction time were analyzed in placebo (0 g/kg), low dose (0.2 g/kg) and high dose (0.6 g/kg) conditions. We found that alcohol intake did not eliminate, but substantially reduced, the formation of time-based expectancy. This effect was stronger for high doses, than for low doses, of alcohol. As a result of our studies, we have evidence that alcohol intake impairs time-based event expectations. The mechanism by which the level of alcohol impairs time-based event expectations needs to be clarified by future research. PMID:26680768

  16. Classical subjective expected utility.

    PubMed

    Cerreia-Vioglio, Simone; Maccheroni, Fabio; Marinacci, Massimo; Montrucchio, Luigi

    2013-04-23

    We consider decision makers who know that payoff-relevant observations are generated by a process that belongs to a given class M, as postulated in Wald [Wald A (1950) Statistical Decision Functions (Wiley, New York)]. We incorporate this Waldean piece of objective information within an otherwise subjective setting à la Savage [Savage LJ (1954) The Foundations of Statistics (Wiley, New York)] and show that this leads to a two-stage subjective expected utility model that accounts for both state and model uncertainty. PMID:23559375

  17. Shallow groundwater recharge mechanism and apparent age in the Ndop plain, northwest Cameroon

    NASA Astrophysics Data System (ADS)

    Wirmvem, Mengnjo Jude; Mimba, Mumbfu Ernestine; Kamtchueng, Brice Tchakam; Wotany, Engome Regina; Bafon, Tasin Godlove; Asaah, Asobo Nkengmatia Elvis; Fantong, Wilson Yetoh; Ayonghe, Samuel Ndonwi; Ohba, Takeshi

    2015-02-01

    Knowledge of groundwater recharge and apparent age constitutes a valuable tool for its sustainable management. Accordingly, shallow groundwater (n = 72) in the Ndop plain has been investigated using the stable isotopes of oxygen (18O) and hydrogen (2H or D) and tritium (3H) to determine the recharge process, timing and rate of recharge, and residence time. The shallow groundwater showed low variability in δ18O values (-2.7 to -4.1 ‰) and 3H content (2.4-3.1 TU). The low variability suggests a similar origin, homogenous aquifer, good water mixing and storage capacity of the groundwater reservoir. Like surface water, a cluster of groundwater along the Ndop Meteoric Water Line (NMWL) and Global Meteoric Water Line indicates meteoric origin/recharge. The rainfall recharge occurs under low relative humidity conditions and negligible evaporation effect. About 80 % of the recharge is from direct heterogeneous/diffuse local precipitation at low altitude (<1,260 m) within the Ndop plain. Approximately 20 % is from high altitude precipitation (localised recharge) or is recharged by the numerous inflowing streams and rivers from high elevations. A homogenous cluster of δ-values in groundwater (and surface water) between May and June monsoon rains on the NMWL suggests dominant recharge during these months. The recharge represents at least 16 % (>251 mm) of the annual rainfall (1,540 mm) indicating high annual recharge; high enough for development of the groundwater resource for agriculture. The 3H content (>2.4 TU) in groundwater indicates post-1952 recharged water with an estimated residence time <30 years, suggesting short subsurface circulation, and subsequently a renewable aquifer.

  18. Yifuning postpones ovarian aging through antioxidant mechanisms and suppression of the Rb/p53 signal transduction pathway.

    PubMed

    Liang, Lei; Zhang, Xu-Hui; Ji, Bo; Yao, Hui; Ling, Xiao-Mei; Guo, Zhi-Jian; Deng, Hong-Zhu; Wu, Xin-Rong

    2016-07-01

    Yifuning is a traditional Chinese medicine recipe that has been used for many years in China for its effects on treating climacteric syndrome in women. The present study aimed to demonstrate the effects and underlying molecular mechanism of Yifuning on the ovaries of aging rats. Selected aging rats were administered different doses of Yifuning (1.0 or 2.0 g/kg by lavage), and after 6 weeks the rats were sacrificed. The activit of indicators of oxidative stress in the serum were measured. The expression levels of 8-oxo-2'-deoxyguanosine (8-OHDG) and p53 in the ovaries were examined using immunohistochemistry. The expression levels of the corresponding genes and proteins were detected by reverse transcription‑quantitative polymerase chain reaction and western blotting analyses, respectively. The results indicated that Yifuning significantly prevented ovarian failure, as indicated by improvements in estrous cycling, reproductive organ weights and sex hormone serum levels. Yifuning significantly increased the levels of superoxide dismutase, glutathione peroxidase, catalase and reduced malondialdehyde and hydrogen peroxide levels. Yifuning reduced DNA damage in the ovaries by reducing the expression of 8‑OHDG and p53. Treatment with Yifuning significantly reduced the age‑induced p19, p53, p21 and Rb activity in the ovaries. The present study demonstrates that Yifuning prevents ovarian failure and the mechanism involved is partly associated with antioxidants and suppression of the Rb/p53 signal transduction pathway. PMID:27222316

  19. Yifuning postpones ovarian aging through antioxidant mechanisms and suppression of the Rb/p53 signal transduction pathway.

    PubMed

    Liang, Lei; Zhang, Xu-Hui; Ji, Bo; Yao, Hui; Ling, Xiao-Mei; Guo, Zhi-Jian; Deng, Hong-Zhu; Wu, Xin-Rong

    2016-07-01

    Yifuning is a traditional Chinese medicine recipe that has been used for many years in China for its effects on treating climacteric syndrome in women. The present study aimed to demonstrate the effects and underlying molecular mechanism of Yifuning on the ovaries of aging rats. Selected aging rats were administered different doses of Yifuning (1.0 or 2.0 g/kg by lavage), and after 6 weeks the rats were sacrificed. The activit of indicators of oxidative stress in the serum were measured. The expression levels of 8-oxo-2'-deoxyguanosine (8-OHDG) and p53 in the ovaries were examined using immunohistochemistry. The expression levels of the corresponding genes and proteins were detected by reverse transcription‑quantitative polymerase chain reaction and western blotting analyses, respectively. The results indicated that Yifuning significantly prevented ovarian failure, as indicated by improvements in estrous cycling, reproductive organ weights and sex hormone serum levels. Yifuning significantly increased the levels of superoxide dismutase, glutathione peroxidase, catalase and reduced malondialdehyde and hydrogen peroxide levels. Yifuning reduced DNA damage in the ovaries by reducing the expression of 8‑OHDG and p53. Treatment with Yifuning significantly reduced the age‑induced p19, p53, p21 and Rb activity in the ovaries. The present study demonstrates that Yifuning prevents ovarian failure and the mechanism involved is partly associated with antioxidants and suppression of the Rb/p53 signal transduction pathway.

  20. The combined effect of dismantling for steam sterilization and aging on the accuracy of spring-style mechanical torque devices

    PubMed Central

    Mahshid, Minoo; Sadr, Seyed Jalil; Fayyaz, Ali; Kadkhodazadeh, Mahdi

    2013-01-01

    Purpose This study aimed to assess the combined effect of dismantling before sterilization and aging on the accuracy (±10% of the target torque) of spring-style mechanical torque devices (S-S MTDs). Methods Twenty new S-SMTDs from two different manufacturers (Nobel Biocare and Straumann: 10 of each type) were selected and divided into two groups, namely, case (group A) and control (group B). For sterilization, 100 cycles of autoclaving were performed in 100 sequences. In each sequence, 10 repetitions of peak torque values were registered for aging. To measure and assess the output of each device, a Tohnichi torque gauge was used (P<0.05). Results Before steam sterilization, all of the tested devices stayed within 10% of their target values. After 100 cycles of steam sterilization and aging with or without dismantling of the devices, the Nobel Biocare devices stayed within 10% of their target torque. In the Straumann devices, despite the significant difference between the peak torque and target torque values, the absolute error values stayed within 10% of their target torque. Conclusion Within the limitations of this study, there was no significant difference between the mean and absolute value of error between Nobel Biocare and Straumann S-S MTDs. PMID:24236244

  1. The effect of ageing on the mechanical properties of the silk of the bridge spider Larinioides cornutus (Clerck, 1757)

    PubMed Central

    Lepore, Emiliano; Isaia, Marco; Mammola, Stefano; Pugno, Nicola

    2016-01-01

    Spider silk is regarded as one of the best natural polymer fibers especially in terms of low density, high tensile strength and high elongation until breaking. Since only a few bio-engineering studies have been focused on spider silk ageing, we conducted nano-tensile tests on the vertical naturally spun silk fibers of the bridge spider Larinioides cornutus (Clerck, 1757) (Arachnida, Araneae) to evaluate changes in the mechanical properties of the silk (ultimate stress and strain, Young’s modulus, toughness) over time. We studied the natural process of silk ageing at different time intervals from spinning (20 seconds up to one month), comparing silk fibers spun from adult spiders collected in the field. Data were analyzed using Linear Mixed Models. We detected a positive trend versus time for the Young’s modulus, indicating that aged silks are stiffer and possibly less effective in catching prey. Moreover, we observed a negative trend for the ultimate strain versus time, attesting a general decrement of the resistance force. These trends are interpreted as being due to the drying of the silk protein chains and the reorientation among the fibers. PMID:27156712

  2. The effect of ageing on the mechanical properties of the silk of the bridge spider Larinioides cornutus (Clerck, 1757).

    PubMed

    Lepore, Emiliano; Isaia, Marco; Mammola, Stefano; Pugno, Nicola

    2016-05-09

    Spider silk is regarded as one of the best natural polymer fibers especially in terms of low density, high tensile strength and high elongation until breaking. Since only a few bio-engineering studies have been focused on spider silk ageing, we conducted nano-tensile tests on the vertical naturally spun silk fibers of the bridge spider Larinioides cornutus (Clerck, 1757) (Arachnida, Araneae) to evaluate changes in the mechanical properties of the silk (ultimate stress and strain, Young's modulus, toughness) over time. We studied the natural process of silk ageing at different time intervals from spinning (20 seconds up to one month), comparing silk fibers spun from adult spiders collected in the field. Data were analyzed using Linear Mixed Models. We detected a positive trend versus time for the Young's modulus, indicating that aged silks are stiffer and possibly less effective in catching prey. Moreover, we observed a negative trend for the ultimate strain versus time, attesting a general decrement of the resistance force. These trends are interpreted as being due to the drying of the silk protein chains and the reorientation among the fibers.

  3. The effect of ageing on the mechanical properties of the silk of the bridge spider Larinioides cornutus (Clerck, 1757)

    NASA Astrophysics Data System (ADS)

    Lepore, Emiliano; Isaia, Marco; Mammola, Stefano; Pugno, Nicola

    2016-05-01

    Spider silk is regarded as one of the best natural polymer fibers especially in terms of low density, high tensile strength and high elongation until breaking. Since only a few bio-engineering studies have been focused on spider silk ageing, we conducted nano-tensile tests on the vertical naturally spun silk fibers of the bridge spider Larinioides cornutus (Clerck, 1757) (Arachnida, Araneae) to evaluate changes in the mechanical properties of the silk (ultimate stress and strain, Young’s modulus, toughness) over time. We studied the natural process of silk ageing at different time intervals from spinning (20 seconds up to one month), comparing silk fibers spun from adult spiders collected in the field. Data were analyzed using Linear Mixed Models. We detected a positive trend versus time for the Young’s modulus, indicating that aged silks are stiffer and possibly less effective in catching prey. Moreover, we observed a negative trend for the ultimate strain versus time, attesting a general decrement of the resistance force. These trends are interpreted as being due to the drying of the silk protein chains and the reorientation among the fibers.

  4. Lamb wave characterization of the effects of long-term thermal-mechanical aging on composite stiffness.

    PubMed

    Seale, M D; Madaras, E I

    1999-09-01

    Lamb waves offer a promising method of evaluating damage in composite materials. The Lamb wave velocity is directly related to the material parameters, so an effective tool exists to monitor damage in composites by measuring the velocity of these waves. The Lamb Wave Imager (LWI) uses a pulse/receive technique that excites an antisymmetric Lamb mode and measures the time-of-flight over a wide frequency range. Given the material density and plate thickness, the bending and out-of-plane shear stiffnesses are calculated from a reconstruction of the dispersion curve. In this study, the time-of-flight as well as the elastic stiffnesses D11, D22, A44, and A55 for composite samples which have undergone combined thermal and mechanical aging are obtained. The samples examined include a baseline specimen with 0 cycles, specimens which have been aged 2350 and 3530 cycles at high strain levels, and one specimen aged 3530 cycles at low strain levels. PMID:10489699

  5. Mechanism of Inflammation in Age-Related Macular Degeneration: An Up-to-Date on Genetic Landmarks

    PubMed Central

    Parmeggiani, Francesco; Sorrentino, Francesco S.; Romano, Mario R.; Incorvaia, Carlo; D'Angelo, Sergio; Perri, Paolo; De Nadai, Katia; Bonomo Roversi, Elia; Franceschelli, Paola; Sebastiani, Adolfo

    2013-01-01

    Age-related macular degeneration (AMD) is the most common cause of irreversible visual impairment among people over 50 years of age, accounting for up to 50% of all cases of legal blindness in Western countries. Although the aging represents the main determinant of AMD, it must be considered a multifaceted disease caused by interactions among environmental risk factors and genetic backgrounds. Mounting evidence and/or arguments document the crucial role of inflammation and immune-mediated processes in the pathogenesis of AMD. Proinflammatory effects secondary to chronic inflammation (e.g., alternative complement activation) and heterogeneous types of oxidative stress (e.g., impaired cholesterol homeostasis) can result in degenerative damages at the level of crucial macular structures, that is photoreceptors, retinal pigment epithelium, and Bruch's membrane. In the most recent years, the association of AMD with genes, directly or indirectly, involved in immunoinflammatory pathways is increasingly becoming an essential core for AMD knowledge. Starting from the key basic-research notions detectable at the root of AMD pathogenesis, the present up-to-date paper reviews the best-known and/or the most attractive genetic findings linked to the mechanisms of inflammation of this complex disease. PMID:24369445

  6. Exploring canopy structure and function as a potential mechanism of sustain carbon sequestration in aging forests

    NASA Astrophysics Data System (ADS)

    Fotis, A. T.; Curtis, P.; Ricart, R.

    2013-12-01

    The notion that old-growth forests reach carbon neutrality has recently been challenged, but the mechanisms responsible for continued productivity have remained elusive. Increases in canopy structural complexity, defined by high horizontal and vertical variability in leaf distribution (rugosity), has been proposed as a mechanism for sustained high rates of above ground net primary production (ANPPw) in forests up to ~170 years by enhancing light use efficiency (LUE) and nitrogen use efficiency (NUE). However, a detailed understanding of how rugosity affects resource distribution within and among trees leading to greater LUE and NUE is not known. We propose that leaves in high rugosity plots receive greater photosynthetic photon flux density (PPFD) than leaves in low rugosity plots, causing shifts from shade- to sun- adapted leaves into deeper portions of the canopy, which is thought to increase the photosynthetic capacity of individuals and lead to higher carbon assimilation in forests. The goal of this research was to: 1) quantify different canopy structural characteristics using a portable canopy LiDAR (PCL) and; 2) assess how these structural characteristics affect resource distribution and subsequent changes in leaf morphological, physiological and biochemical traits in three broadleaf species (e.g., Acer rubrum, Quercus rubra and Fagus grandifolia) and one conifer species (e.g., Pinus strobus) at different levels in the canopy in plots with similar leaf are index (LAI) but highly contrasting rugosity levels. We found that gap fraction had a strong positive correlation with rugosity. High rugosity plots had a bimodal distribution of LAI that was concentrated at the top and bottom of the canopy with an open midstory (between 10-50% of total canopy height) whereas low rugosity plots had a more even distribution of leaves. Leaf mass per area (LMA) of all broadleaved species had a strong positive correlation with cumulative gap fraction (P. strobus had a relatively

  7. Mechanical changes in rat tail tendons induced by dibasic amino acids as a function of age.

    PubMed

    Reihsner, R; Menzel, E J

    1994-01-01

    Rat tail tendons from 54-day-old and 900-day-old animals were incubated with different concentrations of the dibasic amino acids, lysine and arginine. We observed a significant incorporation of these amino acids into the tendons. Uniaxial tension tests and relaxation experiments were performed at strain levels within the linear portion of the stress-strain relationship. The incorporation of the amino acids resulted in a decrease of ultimate stress and maximum Young's modulus and, after separation of the elastic and viscous stress components, in a decrease of the elastic fraction. The incorporation of amino acids and the resulting mechanical alterations were more pronounced in the young animals. The reversibility of the effects induced by the amino acids was tested. After the glycosaminoglycan chains were digested with chondroitinase ABC, we showed that the dibasic amino acids bind predominantly to the proteoglycan matrix. A possible analogy to the effects of amino acid incorporation on biomechanics and swelling with a monovalent cation such as Na+ is discussed.

  8. Effects of aging procedures on the molecular, biochemical, morphological, and mechanical properties of vacuum-formed retainers.

    PubMed

    Ahn, Hyo-Won; Ha, Hye-Ryun; Lim, Ho-Nam; Choi, Samjin

    2015-11-01

    The influence of intraoral exposure procedures on the physical characteristics of thermoplastic vacuum-formed retainers (VFRs) is still unclear. The effects of thermoforming and intraoral use on the molecular, chemical, morphological, and mechanical properties of thermoplastic VFRs were investigated. VFRs with a 0.8-mm-thick thermoplastic PETG sheet acquired from 48 patients were investigated with two aging procedures, including vacuum forming and intraoral exposure, for 2-week and 6-month. Eight evaluating sites for thermoplastic VFRs were assessed with seven analytical techniques. LM, SEM, and AFM microscopic findings showed that the surface characteristics increased with increasing in vivo exposure time (a four-fold increase) and varied depending on the sites evaluated (an occlusal surface). Raman and EDX spectroscopic findings showed that aging procedures led to a significant change in the molecular composition of VFRs, leading to a decrease in the composition rate of carbon (C) and the presence of silicon (Si), phosphorus (P), and calcium (Ca). Compressive strength and tensile tests showed that aging procedures led to a significant increase (P<0.01) in ultimate tensile strength, elastic modulus, the stored energy at a 6-mm deflection (u6 mm), and the compressed load at a 3-mm deflection (σ3 mm). Thermoforming led to a smoother surface and no crystallization of PETG sheets. Intraoral exposure accelerated changes in surface morphology, tensile strength, and elastic modulus of VFRs. This change was site-specific and enhanced with an increase in intraoral exposure time. Therefore, thermoforming and in vivo oral exposure procedures led to the molecular, morphological, and mechanical properties of thermoplastic VFRs.

  9. Beyond my wildest expectations.

    PubMed

    Nester, Eugene

    2014-01-01

    With support from my parents, I fulfilled their and my expectations of graduating from college and becoming a scientist. My scientific career has focused on two organisms, Bacillus subtilis and Agrobacterium tumefaciens, and two experimental systems, aromatic amino acid synthesis and DNA transfer in bacteria and plants. Studies on B. subtilis emphasized the genetics and biochemistry of aromatic amino acid synthesis and the characterization of competence in DNA transformation. I carried out both as a postdoc at Stanford with Josh Lederberg. At the University of Washington, I continued these studies and then investigated how Agrobacterium transforms plant cells. In collaboration, Milt Gordon, Mary-Dell Chilton, and I found that this bacterium could transfer a piece of its plasmid into plant cells and thereby modify their properties. This discovery opened up a host of intriguing questions that we have tried to answer over the last 35 years. PMID:25208299

  10. Understanding the relationship between religiousness, spirituality, and underage drinking: the role of positive alcohol expectancies.

    PubMed

    Sauer-Zavala, Shannon; Burris, Jessica L; Carlson, Charles R

    2014-02-01

    Research has consistently found that religiousness and spirituality are negatively associated with underage drinking. However, there is a paucity of research exploring the mechanisms by which these variables influence this important outcome. With 344 underage young adults (ages 18-20; 61 % women), we investigated positive alcohol expectancies as a mediator between religiousness and spirituality (measured separately) and underage alcohol use. Participants completed the Religious Commitment Inventory-10, Daily Spiritual Experiences Scale, Alcohol Expectancies Questionnaire, and Drinking Styles Questionnaire. Results indicate less positive alcohol expectancies partially mediate the relationship between both religiousness and spirituality and underage alcohol use. This suggests religiousness and spirituality's protective influence on underage drinking is partly due to their influence on expectations about alcohol's positive effects. Since underage drinking predicts problem drinking later in life and places one at risk for serious physical and mental health problems, it is important to identify specific points of intervention, including expectations about alcohol that rise from religious and spiritual factors.

  11. Great expectations: what do patients expect and how can expectations be managed?

    PubMed

    Newton, J T; Cunningham, S J

    2013-06-01

    Patients' expectations of their treatment are a key determinant in their satisfaction with treatment. Expectations may encompass not only notions of the outcome of treatment, but also the process of treatment. This article explores the processes by which expectations are formed, differences in expectations across patient groups, and the psychopathology of individuals with unrealistic expectations of treatment manifest in body dysmorphic disorder.

  12. Mechanical behavior of a Y-TZP ceramic for monolithic restorations: effect of grinding and low-temperature aging.

    PubMed

    Pereira, G K R; Silvestri, T; Camargo, R; Rippe, M P; Amaral, M; Kleverlaan, C J; Valandro, L F

    2016-06-01

    This study aimed to investigate the effects of grinding with diamond burs and low-temperature aging on the mechanical behavior (biaxial flexural strength and structural reliability), surface topography, and phase transformation of a Y-TZP ceramic for monolithic dental restorations. Disc-shaped specimens (Zirlux FC, Ivoclar Vivadent) were manufactured according to ISO 6872 (2008) and divided in accordance with two factors: "grinding - 3 levels" and "LTD - 2 levels". Grinding was performed using a contra-angle handpiece under constant water-cooling with different grit-sizes (extra-fine and coarse diamond burs). LTD was simulated in an autoclave at 134°C, under a pressure of 2 bar, over a period of 20h. Surface topography analysis showed an increase in roughness based on surface treatment grit-size (Coarse>Xfine>Ctrl), LTD did not influence roughness values. Both grinding and LTD promoted an increase in the amount of m-phase, although different susceptibilities to degradation were observed. According to existing literature the increase of m-phase content is a direct indicative of Y-TZP degradation. Weibull analysis showed an increase in characteristic strength after grinding (Coarse=Xfine>Ctrl), while for LTD, distinct effects were observed (Ctrlaging in autoclave for 20h (LTD) and grinding showed not to be detrimental to the mechanical properties of Zirlux FC Y-TZP ceramic. PMID:27040197

  13. Does benign paroxysmal positional vertigo explain age and gender variation in patients with vertigo by mechanical assistance maneuvers?

    PubMed

    Wang, Jing; Chi, Fang-Lu; Jia, Xian-Hao; Tian, Liang; Richard-Vitton, Th

    2014-11-01

    Benign paroxysmal positional vertigo (BPPV) is one of the most common peripheral vestibular diseases. The aim of this study was to explore the prevalence of BPPV in vertigo patients and the characteristics of BPPV in diagnosis and repositioning using mechanical assistance maneuvers and to analyze and summarize the reasons showing these characteristics. Seven hundred and twenty-six patients with vertigo were enrolled in this study. All patients were inspected by TRV armchair (SYNAPSYS, model TRV, France). BPPV patients were identified by the examination results. The characteristics and results using TRV armchair in diagnosis and treatment of BPPV were compared and analyzed. Of 726 vertigo patients, 209 BPPV patients were diagnosed, including 58 men and 151 women, aged from 16 to 87 (mean 52.90 ± 11.93) years. There were significant differences in the proportion of BPPV in male and female vertigo patients (P = 0.0233), but no differences among all age groups (P = 0.3201). Of 209 BPPV patients, 208 cases were repositioned by TRV armchair and no one appeared to have otolithic debris relocated into another canal in the repositioning procedures. 202 cases (97.12 %) were successful and six cases (2.87 %) were effective. None of them failed. This study suggests that BPPV is one of the most common diseases in the young vertigo patients, just like that in the old ones. Female of the species has predilection for BPPV and the site of predilection is the right posterior semicircular canals (PC-BPPV). The results of repositioning are perfect using mechanical assistance maneuvers.

  14. Sociology of Low Expectations

    PubMed Central

    Samuel, Gabrielle; Williams, Clare

    2015-01-01

    Social scientists have drawn attention to the role of hype and optimistic visions of the future in providing momentum to biomedical innovation projects by encouraging innovation alliances. In this article, we show how less optimistic, uncertain, and modest visions of the future can also provide innovation projects with momentum. Scholars have highlighted the need for clinicians to carefully manage the expectations of their prospective patients. Using the example of a pioneering clinical team providing deep brain stimulation to children and young people with movement disorders, we show how clinicians confront this requirement by drawing on their professional knowledge and clinical expertise to construct visions of the future with their prospective patients; visions which are personalized, modest, and tainted with uncertainty. We refer to this vision-constructing work as recalibration, and we argue that recalibration enables clinicians to manage the tension between the highly optimistic and hyped visions of the future that surround novel biomedical interventions, and the exigencies of delivering those interventions in a clinical setting. Drawing on work from science and technology studies, we suggest that recalibration enrolls patients in an innovation alliance by creating a shared understanding of how the “effectiveness” of an innovation shall be judged. PMID:26527846

  15. Expectations and speech intelligibility.

    PubMed

    Babel, Molly; Russell, Jamie

    2015-05-01

    Socio-indexical cues and paralinguistic information are often beneficial to speech processing as this information assists listeners in parsing the speech stream. Associations that particular populations speak in a certain speech style can, however, make it such that socio-indexical cues have a cost. In this study, native speakers of Canadian English who identify as Chinese Canadian and White Canadian read sentences that were presented to listeners in noise. Half of the sentences were presented with a visual-prime in the form of a photo of the speaker and half were presented in control trials with fixation crosses. Sentences produced by Chinese Canadians showed an intelligibility cost in the face-prime condition, whereas sentences produced by White Canadians did not. In an accentedness rating task, listeners rated White Canadians as less accented in the face-prime trials, but Chinese Canadians showed no such change in perceived accentedness. These results suggest a misalignment between an expected and an observed speech signal for the face-prime trials, which indicates that social information about a speaker can trigger linguistic associations that come with processing benefits and costs.

  16. Expectations and speech intelligibility.

    PubMed

    Babel, Molly; Russell, Jamie

    2015-05-01

    Socio-indexical cues and paralinguistic information are often beneficial to speech processing as this information assists listeners in parsing the speech stream. Associations that particular populations speak in a certain speech style can, however, make it such that socio-indexical cues have a cost. In this study, native speakers of Canadian English who identify as Chinese Canadian and White Canadian read sentences that were presented to listeners in noise. Half of the sentences were presented with a visual-prime in the form of a photo of the speaker and half were presented in control trials with fixation crosses. Sentences produced by Chinese Canadians showed an intelligibility cost in the face-prime condition, whereas sentences produced by White Canadians did not. In an accentedness rating task, listeners rated White Canadians as less accented in the face-prime trials, but Chinese Canadians showed no such change in perceived accentedness. These results suggest a misalignment between an expected and an observed speech signal for the face-prime trials, which indicates that social information about a speaker can trigger linguistic associations that come with processing benefits and costs. PMID:25994710

  17. Molecular biosensing mechanisms in the spleen for the removal of aged and damaged red cells from the blood circulation.

    PubMed

    Sugawara, Yoshiaki; Hayashi, Yuko; Shigemasa, Yuki; Abe, Yoko; Ohgushi, Ikumi; Ueno, Eriko; Shimamoto, Fumio

    2010-01-01

    Heinz bodies are intraerythrocytic inclusions of hemichrome formed as a result of hemoglobin (Hb) oxidation. They typically develop in aged red cells. Based on the hypothesis that hemichrome formation is an innate characteristic of physiologically normal Hb molecules, we present an overview of our previous findings regarding the molecular instability of Hb and the formation of hemichrome, as well as recent findings on Heinz body formation within normal human erythrocytes. Human adult Hb (HbO(2) A) prepared from healthy donors showed a tendency to produce hemichrome, even at close to physiological temperature and pH. Recent studies found that the number of Heinz bodies formed in red cells increased with increasing temperature when freshly drawn venous blood from healthy donors was subjected to mild heating above 37 °C. These findings suggest that Hb molecules control the removal of non-functional erythrocytes from the circulation via hemichrome formation and subsequent Heinz body clustering. In this review, we discuss the molecular biosensing mechanisms in the spleen, where hemichrome formation and subsequent Heinz body clustering within erythrocytes play a key role in the removal of aged and damaged red cells from the blood circulation.

  18. Neuro-oscillatory mechanisms of intersensory selective attention and task switching in school-aged children, adolescents and young adults.

    PubMed

    Murphy, Jeremy W; Foxe, John J; Molholm, Sophie

    2016-05-01

    The ability to attend to one among multiple sources of information is central to everyday functioning. Just as central is the ability to switch attention among competing inputs as the task at hand changes. Such processes develop surprisingly slowly, such that even into adolescence, we remain slower and more error prone at switching among tasks compared to young adults. The amplitude of oscillations in the alpha band (~8-14 Hz) tracks the top-down deployment of attention, and there is growing evidence that alpha can act as a suppressive mechanism to bias attention away from distracting sensory input. Moreover, the amplitude of alpha has also been shown to be sensitive to the demands of switching tasks. To understand the neural basis of protracted development of these executive functions, we recorded high-density electrophysiology from school-aged children (8-12 years), adolescents (13-17), and young adults (18-34) as they performed a cued inter-sensory selective attention task. The youngest participants showed increased susceptibility to distracting inputs that was especially evident when switching tasks. Concordantly, they showed weaker and delayed onset of alpha modulation compared to the older groups. Thus the flexible and efficient deployment of alpha to bias competition among attentional sets remains underdeveloped in school-aged children. PMID:26190204

  19. Children and Computers: Greek Parents' Expectations.

    ERIC Educational Resources Information Center

    Vryzas, Konstantinos; Tsitouridou, Melpomene

    2002-01-01

    This survey investigated the expectations of Greek parents with regard to the potential impact of children's computer use on the fields of education, interpersonal relationships, and professional and social life. Considers socio-cultural environment; sex and age; and whether the parents had knowledge of computers, used computers at work, or had a…

  20. Major League Baseball Players' Life Expectancies.

    PubMed

    Saint Onge, Jarron M; Rogers, Richard G; Krueger, Patrick M

    2008-07-17

    OBJECTIVE: We examine the importance of anthropometric and performance measures, and age, period, and cohort effects in explaining life expectancies among major league baseball (MLB) players over the past century. METHODS: We use discrete time hazard models to calculate life tables with covariates with data from Total Baseball, a rich source of information on all players who played in the major league. RESULTS: Compared to 20-year-old U.S. males, MLB players can expect almost five additional years of life. Height, weight, handedness, and player ratings are unassociated with the risk of death in this population of highly active and successful adults. Career length is inversely associated with the risk of death, likely because those who play longer gain additional incomes, physical fitness, and training. CONCLUSIONS: Our results indicate improvements in life expectancies with time for all age groups and indicate possible improvements in longevity in the general U.S. population.

  1. Mechanism of All-trans-retinal Toxicity with Implications for Stargardt Disease and Age-related Macular Degeneration*

    PubMed Central

    Chen, Yu; Okano, Kiichiro; Maeda, Tadao; Chauhan, Vishal; Golczak, Marcin; Maeda, Akiko; Palczewski, Krzysztof

    2012-01-01

    Compromised clearance of all-trans-retinal (atRAL), a component of the retinoid cycle, increases the susceptibility of mouse retina to acute light-induced photoreceptor degeneration. Abca4−/−Rdh8−/− mice featuring defective atRAL clearance were used to examine the one or more underlying molecular mechanisms, because exposure to intense light causes severe photoreceptor degeneration in these animals. Here we report that bright light exposure of Abca4−/−Rdh8−/− mice increased atRAL levels in the retina that induced rapid NADPH oxidase-mediated overproduction of intracellular reactive oxygen species (ROS). Moreover, such ROS generation was inhibited by blocking phospholipase C and inositol 1,4,5-trisphosphate-induced Ca2+ release, indicating that activation occurs upstream of NADPH oxidase-mediated ROS generation. Because multiple upstream G protein-coupled receptors can activate phospholipase C, we then tested the effects of antagonists of serotonin 2A (5-HT2AR) and M3-muscarinic (M3R) receptors and found they both protected Abca4−/−Rdh8−/− mouse retinas from light-induced degeneration. Thus, a cascade of signaling events appears to mediate the toxicity of atRAL in light-induced photoreceptor degeneration of Abca4−/−Rdh8−/− mice. A similar mechanism may be operative in human Stargardt disease and age-related macular degeneration. PMID:22184108

  2. Mechanical properties and the structure of chromium-zirconium bronze after dynamic channel-angular pressing and subsequent aging

    NASA Astrophysics Data System (ADS)

    Zel'dovich, V. I.; Dobatkin, S. V.; Frolova, N. Yu.; Khomskaya, I. V.; Kheifets, A. E.; Shorokhov, E. V.; Nasonov, P. A.

    2016-01-01

    Changes in the structure and mechanical properties of the low-alloy chromium-zirconium bronze Cu-0.14% Cr-0.04% Zr have been investigated after a high-strain-rate (104-105 s-1) deformation by the method of dynamic channel-angular pressing (DCAP) and following annealings at 300-700°C. A significant increase in the mechanical properties of the investigated bronze after DCAP and after DCAP and subsequent aging at temperatures of 400-450°C has been established. Thus, compared to the initial quenched state the ultimate tensile strength increases by a factor of 2.6 and 2.8 and the yield stress, by a factor of 3.3 and 5.1, respectively, with the retention of satisfactory plasticity. It has been shown that, upon DCAP and subsequent annealings, in the low-alloyed bronze under investigation there occurs a decomposition of the α solid solution with the precipitation of nanosized particles. This leads to a significant strengthening of the bronze and to an increase in its thermal stability compared with the pure copper subjected to DCAP.

  3. Effects of aging on the structural, mechanical, and thermal properties of the silicone rubber current transformer insulation bushing for a 500 kV substation.

    PubMed

    Wang, Zhigao; Zhang, Xinghai; Wang, Fangqiang; Lan, Xinsheng; Zhou, Yiqian

    2016-01-01

    In order to analyze the cracking and aging reason of the silicone rubber current transformer (CT) insulation bushing used for 8 years from a 500 kV alternating current substation, characteristics including Fourier transform infrared (FTIR) spectroscopy, mechanical properties analysis, hardness, and thermo gravimetric analysis have been carried out. The FTIR results indicated that the external surface of the silicone rubber CT insulation bushing suffered from more serious aging than the internal part, fracture of side chain Si-C bond was much more than the backbone. Mechanical properties and thermal stability results illustrated that the main aging reasons were the breakage of side chain Si-C bond and the excessive cross-linking reaction of the backbone. This study can provide valuable basis for evaluating degradation mechanism and aging state of the silicone rubber insulation bushing in electric power field.

  4. Effects of aging on the structural, mechanical, and thermal properties of the silicone rubber current transformer insulation bushing for a 500 kV substation.

    PubMed

    Wang, Zhigao; Zhang, Xinghai; Wang, Fangqiang; Lan, Xinsheng; Zhou, Yiqian

    2016-01-01

    In order to analyze the cracking and aging reason of the silicone rubber current transformer (CT) insulation bushing used for 8 years from a 500 kV alternating current substation, characteristics including Fourier transform infrared (FTIR) spectroscopy, mechanical properties analysis, hardness, and thermo gravimetric analysis have been carried out. The FTIR results indicated that the external surface of the silicone rubber CT insulation bushing suffered from more serious aging than the internal part, fracture of side chain Si-C bond was much more than the backbone. Mechanical properties and thermal stability results illustrated that the main aging reasons were the breakage of side chain Si-C bond and the excessive cross-linking reaction of the backbone. This study can provide valuable basis for evaluating degradation mechanism and aging state of the silicone rubber insulation bushing in electric power field. PMID:27390631

  5. The effects of solution treatment on the mechanical properties of age-hardened A-286 bar stock at elevated and cryogenic temperature

    NASA Technical Reports Server (NTRS)

    Montano, J. W.

    1972-01-01

    The mechanical properties are presented of solution treated and age hardened A-286 corrosion resistant steel bar stock. Material solution treated at 899 C or 982 C, each followed by an age hardening treatment of 718 C, was evaluated. Test specimens manufactured from 1.50 inch (3.81 cm) diameter bar stock were tested at temperatures from +649 C to -253 C. The test data indicated excellent tensile, yield, elongation and reduction-in-area properties at all testing temperatures for both solution treated and aged materials. Cryogenic temperature notched tensile, impact, and shear tests indicated excellent notch strength, ductility, and shear values. There was very little difference in the mechanical properties of the two solution treated and aged materials. The only exception was that the 962 C solution treated and aged material had superior stress rupture properties at 649 C.

  6. Grade Expectations: How Marks and Education Policies Shape Students' Ambitions

    ERIC Educational Resources Information Center

    OECD Publishing (NJ3), 2012

    2012-01-01

    While enrolment in tertiary education has increased dramatically over the past decades, many university-aged students do not enrol, nor do they expect to earn a university degree. While it is important to promote high expectations for further education, it is equally important to ensure that students' expectations are well-aligned with their…

  7. Cannabis expectancies in substance misusers: French validation of the Marijuana Effect Expectancy Questionnaire.

    PubMed

    Guillem, Eric; Notides, Christine; Vorspan, Florence; Debray, Marcel; Nieto, Isabel; Leroux, Mayliss; Lépine, Jean-Pierre

    2011-01-01

    The aim of this study was to evaluate the psychometric properties of the French version of the Marijuana Effect Expectancy Questionnaire (48 items) and study the cannabis expectancies according to the patterns of substance use and psychiatric disorders (DSM-IV). A sample of 263 subjects (average age 33.1 years [SD = 8.7], 56% men) consisting of cannabis users (n = 64), psychiatric inpatients (n = 175, most of whom were hospitalized for withdrawal), and a control group (n = 24) completed the questionnaire. Internal reliability was good (α= .87) and temporal reliability was satisfactory, with 24 of 48 items having a significant κ ≥ .41. Factor analysis showed four main factors that explained 42.1% of the total variance. The women feared Cognitive Impairment and Negative Effects, and Negative Behavioral Effects more than the men. The onset age of cannabis use, onset age of abuse, abuse and dependence were associated with fewer negative expectancies. Cannabis dependents differed from abusers by more Relaxation and Social Facilitation expectancies. Patients with major depressive episodes, panic disorder, social anxiety disorder, or posttraumatic stress disorder feared negative effects the most. Schizophrenic patients expected more Perceptual Enhancement and Craving. The French version of the Marijuana Effect Expectancy Questionnaire has good psychometric properties and is valid to assess cannabis expectancies in adolescents and adults with substance use disorders.

  8. Great expectations: temporal expectation modulates perceptual processing speed.

    PubMed

    Vangkilde, Signe; Coull, Jennifer T; Bundesen, Claus

    2012-10-01

    In a crowded dynamic world, temporal expectations guide our attention in time. Prior investigations have consistently demonstrated that temporal expectations speed motor behavior. We explore effects of temporal expectation on perceptual speed in three nonspeeded, cued recognition paradigms. Different hazard rate functions for the cue-stimulus foreperiod were used to manipulate temporal expectations. By computational modeling we estimated two distinct components of visual attention: the temporal threshold of conscious perception (t₀ ms) and the speed of subsequent encoding into visual short-term memory (v items/s). Notably, these components were measured independently of any motor involvement. The threshold t₀ was unaffected by temporal expectation, but perceptual processing speed v increased with increasing expectation. By employing constant hazard rates to keep expectation constant over time, we further confirmed that the increase in perceptual speed was independent of the cue-stimulus duration. Thus, our results strongly suggest temporal expectations optimize perceptual performance by speeding information processing.

  9. Expectations predict chronic pain treatment outcomes.

    PubMed

    Cormier, Stéphanie; Lavigne, Geneviève L; Choinière, Manon; Rainville, Pierre

    2016-02-01

    Accumulating evidence suggests an association between patient pretreatment expectations and numerous health outcomes. However, it remains unclear if and how expectations relate to outcomes after treatments in multidisciplinary pain programs. The present study aims at investigating the predictive association between expectations and clinical outcomes in a large database of chronic pain patients. In this observational cohort study, participants were 2272 patients treated in one of 3 university-affiliated multidisciplinary pain treatment centers. All patients received personalized care, including medical, psychological, and/or physical interventions. Patient expectations regarding pain relief and improvements in quality of life and functioning were measured before the first visit to the pain centers and served as predictor variables. Changes in pain intensity, depressive symptoms, pain interference, and tendency to catastrophize, as well as satisfaction with pain treatment and global impressions of change at 6-month follow-up, were considered as treatment outcomes. Structural equation modeling analyses showed significant positive relationships between expectations and most clinical outcomes, and this association was largely mediated by patients' global impressions of change. Similar patterns of relationships between variables were also observed in various subgroups of patients based on sex, age, pain duration, and pain classification. Such results emphasize the relevance of patient expectations as a determinant of outcomes in multimodal pain treatment programs. Furthermore, the results suggest that superior clinical outcomes are observed in individuals who expect high positive outcomes as a result of treatment.

  10. Great Expectations: Temporal Expectation Modulates Perceptual Processing Speed

    ERIC Educational Resources Information Center

    Vangkilde, Signe; Coull, Jennifer T.; Bundesen, Claus

    2012-01-01

    In a crowded dynamic world, temporal expectations guide our attention in time. Prior investigations have consistently demonstrated that temporal expectations speed motor behavior. We explore effects of temporal expectation on "perceptual" speed in three nonspeeded, cued recognition paradigms. Different hazard rate functions for the cue-stimulus…

  11. Initial precipitation and hardening mechanism during non-isothermal aging in an Al–Mg–Si–Cu 6005A alloy

    SciTech Connect

    Yang, Wenchao; Ji, Shouxun; Huang, Lanping; Sheng, Xiaofei; Li, Zhou; Wang, Mingpu

    2014-08-15

    The characterization of precipitation and hardening mechanism during non-isothermal aging had been investigated using high resolution transmission electron microscopy for an Al–Mg–Si–Cu 6005A alloy. It was proposed that the needle-shaped β″ precipitates with a three-dimension coherency strain-field and an increased number density in the Al matrix provided the maximum strengthening effect for the Al–Mg–Si–Cu 6005A alloy. Simultaneously, it was also found that the formation and evolution of clusters in the early precipitation were associated with the vacancy binding energy, during which Si atoms played an important role in controlling the numbers density of Mg/Si co-clusters, and the excess Si atoms provided the increased number of nucleation sites for the subsequent precipitates to strengthen and improve the precipitation rate. Finally, based on the experimental observation and theoretical analysis, the precipitation sequence during the early precipitation in the Al–Mg–Si–Cu 6005A alloy was proposed as: supersaturated solid solution → Si-vacancy pairs, Mg-vacancy pairs and Mg clusters → Si clusters, and dissolution of Mg clusters → Mg atoms diffusion into the existing Si clusters → Mg/Si co-clusters → GP zone. - Highlights: • β″ precipitates provide the maximum strengthening effect for the 6005A alloy. • Si atoms play an important role in controlling the numbers of Mg/Si co-clusters. • The early aging sequence is deduced based on the solute-vacancy binding energy.

  12. Assessing outcome expectations in older adults: the multidimensional outcome expectations for exercise scale.

    PubMed

    Wójcicki, Thomas R; White, Siobhan M; McAuley, Edward

    2009-01-01

    Outcome expectations, an important element of social cognitive theory, have been associated with physical activity in older adults. Yet, the measurement of this construct has often adopted a unidimensional approach. We examined the validity of a theoretically consistent three-factor (physical, social, and self-evaluative) outcome expectations exercise scale in middle-aged and older adults (N = 320; M age = 63.8). Participants completed questionnaires assessing outcome expectations, physical activity, self-efficacy, and health status. Comparisons of the hypothesized factor structure with competing models indicated that a three-factor model provided the best fit for the data. Construct validity was further demonstrated by significant association with physical activity and self-efficacy and differential associations with age and health status. Further evidence of validity and application to social cognitive models of physical activity is warranted.

  13. Measuring Alcohol Expectancies in Youth

    ERIC Educational Resources Information Center

    Randolph, Karen A.; Gerend, Mary A.; Miller, Brenda A.

    2006-01-01

    Beliefs about the consequences of using alcohol, alcohol expectancies, are powerful predictors of underage drinking. The Alcohol Expectancies Questionnaire-Adolescent form (AEQ-A) has been widely used to measure expectancies in youth. Despite its broad use, the factor structure of the AEQ-A has not been firmly established. It is also not known…

  14. A preliminary mechanical property and stress corrosion evaluation of VIM-VAR work strengthened and direct aged Inconel 718 bar material

    NASA Technical Reports Server (NTRS)

    Montano, J. W.

    1987-01-01

    This report presents a preliminary mechanical property and stress corrosion evaluation of double melted (vacuum induction melted (VIM), and vacuum arc remelted (VAR)), solution treated, work strengthened and direct aged Inconel 718 alloy bar (5.50 in. (13.97 cm) diameter). Two sets of tensile specimens, one direct single aged and the other direct double aged, were tested at ambient temperature in both the longitudinal and transverse directions. Longitudinal tensile and yield strengths in excess of 200 ksi (1378.96 MPa) and 168 ksi (1158.33 MPa), respectively, were realized at ambient temperature, for the direct double aged specimen. No failures occurred in the single or double edged longitudinal and transverse tensile specimens stressed to 75 and 100 percent of their respective yield strengths and exposed to a salt fog environment for 180 days. Tensile tests performed after the stress corrosion test showed no mechanical property degradation.

  15. The mechanical properties of ex vivo bovine and porcine crystalline lenses: age-related changes and location-dependent variations.

    PubMed

    Yoon, Sangpil; Aglyamov, Salavat; Karpiouk, Andrei; Emelianov, Stanislav

    2013-06-01

    The mechanical properties of ex vivo animal lenses from three groups were evaluated: old bovine (25-30 mo old, n = 4), young bovine (6 mo old, n = 4) and young porcine (6 mo old, n = 4) eye globes. We measured the dynamics of laser-induced microbubbles created at different locations within the crystalline lenses. An impulsive acoustic radiation force was applied to the microbubble, and the microbubble displacements were measured using a custom-built high pulse repetition frequency ultrasound system. Based on the measured dynamics of the microbubbles, Young's moduli of bovine and porcine lens tissue in the vicinity of the microbubbles were reconstructed. Age-related changes and location-dependent variations in the Young's modulus of the lenses were observed. Near the center, the old bovine lenses had a Young's modulus approximately fivefold higher than that of young bovine and porcine lenses. The gradient of Young's modulus with respect to radial distance was observed in the lenses from three groups.

  16. THE ULTRA COOL BROWN DWARF COMPANION OF WD 0806-661B: AGE, MASS, AND FORMATION MECHANISM

    SciTech Connect

    Rodriguez, David R.; Zuckerman, B.; Melis, Carl; Song, Inseok

    2011-05-10

    We have combined multi-epoch images from the Infrared Side Port Imager on the CTIO 4 m telescope to derive a 3{sigma} limit of J = 21.7 for the ultra cool brown dwarf companion to WD 0806-661 (GJ 3483). We find that J - [4.5] > 4.95, redder than any other brown dwarf known to date. With theoretical evolutionary models and ages 1.5-2.7 Gyr, we estimate the brown dwarf companion to have mass <10-13 M{sub Jup} and temperature {approx}< 400 K, providing evidence that this is among the coolest brown dwarfs currently known. The range of masses for this object is consistent with that anticipated from Jeans-mass fragmentation and we present this as the likely formation mechanism. However, we find that substellar companions of similar mass ({approx}7-17 M{sub Jup}) are distributed over a wide range of semimajor axes, which suggests that giant planet and low-mass brown dwarf formation overlap in this mass range.

  17. Evaluating mechanisms of nutrient depletion and 13C enrichment in the intermediate-depth Atlantic during the last ice age

    NASA Astrophysics Data System (ADS)

    Sigman, Daniel M.; Lehman, Scott J.; Oppo, Delia W.

    2003-09-01

    Using an ocean box model, we have studied the effect of altered circulation on the oceanic distributions of phosphate (PO4-3) and the 13C/12C and 14C/12C of dissolved inorganic carbon to evaluate competing hypotheses for the cause of observed nutrient depletion and 13C enrichment at intermediate depths of the Atlantic during the last ice age. Because of "nutrient trapping" and limited air-sea carbon isotopic equilibration, the simple imposition of an intense meridional overturning cell in the Atlantic fails to simultaneously lower nutrient concentrations and raise 13C/12C to observed glacial levels. Export of intermediate water out of the Atlantic causes a basin-to-basin nutrient transfer, thus providing a more efficient mechanism of intermediate-depth Atlantic nutrient depletion and improved carbon isotopic equilibration at low temperatures (i.e., 13C enrichment). Although this export adds nutrients to the intermediate depths of the Pacific and Indian Oceans, the simulated glacial intermediate-depth Indo-Pacific is nevertheless moderately depleted in PO4-3 relative to the model's interglacial control, in agreement with consensus paleoceanographic evidence. This Indo-Pacific PO4-3 depletion results from our use of a "glacial base case" in which nutrient-rich Antarctic Intermediate Water formation is absent as part of the elimination of the modern North-Atlantic-Deep-Water-based "conveyor" circulation.

  18. The effects of aging for 50,000 hours at 343{degree}C on the mechanical properties of Type 308 stainless steel weldments

    SciTech Connect

    Alexander, D.J.; Nanstad, R.K.

    1995-12-01

    The effects of long-term aging at intermediate temperature on the mechanical properties of type 308 stainless steel weld metals have been studied. Three multipass shielded metal-arc welds with ferrite levels of 4, 8, or 12% were aged up to 50,000 h at 343{degrees}C. Tensile and Charpy V-notch specimens were used to determine the effects of aging on the mechanical properties of the weld metal. Aging had little effect on the yield strength of the weld metal, but did result in a slight increase (approximately 5%) in the ultimate tensile strength. The ferrite content had little effect on the yield strength of the materials, but the ultimate tensile strength increased slightly with higher ferrite content. In contrast to the small effect on the tensile properties, the impact properties were significantly degraded by aging. The extent of the degradation increased with increasing ferrite content and continued to increase with increasing aging time, Spinodal decomposition and the precipitation of G-phase particles in the ferrite phase are believed to be responsible for the degradation of the mechanical properties.

  19. Investigating the specific core genetic-and-epigenetic networks of cellular mechanisms involved in human aging in peripheral blood mononuclear cells

    PubMed Central

    Li, Cheng-Wei; Wang, Wen-Hsin; Chen, Bor-Sen

    2016-01-01

    Aging is an inevitable part of life for humans, and slowing down the aging process has become a main focus of human endeavor. Here, we applied a systems biology approach to construct protein-protein interaction networks, gene regulatory networks, and epigenetic networks, i.e. genetic and epigenetic networks (GENs), of elderly individuals and young controls. We then compared these GENs to extract aging mechanisms using microarray data in peripheral blood mononuclear cells, microRNA (miRNA) data, and database mining. The core GENs of elderly individuals and young controls were obtained by applying principal network projection to GENs based on Principal Component Analysis. By comparing the core networks, we identified that to overcome the accumulated mutation of genes in the aging process the transcription factor JUN can be activated by stress signals, including the MAPK signaling, T-cell receptor signaling, and neurotrophin signaling pathways through DNA methylation of BTG3, G0S2, and AP2B1 and the regulations of mir-223 let-7d, and mir-130a. We also address the aging mechanisms in old men and women. Furthermore, we proposed that drugs designed to target these DNA methylated genes or miRNAs may delay aging. A multiple drug combination comprising phenylalanine, cholesterol, and palbociclib was finally designed for delaying the aging process. PMID:26895224

  20. Possible Mechanisms Underlying Aging-Related Changes in Early Diastolic Filling and Long Axis Motion—Left Ventricular Length and Blood Pressure

    PubMed Central

    Peverill, Roger E.; Chou, Bon; Donelan, Lesley; Mottram, Philip M.; Gelman, John S.

    2016-01-01

    Background The transmitral E wave and the peak velocity of early diastolic mitral annular motion (e`) both decrease with age, but the mechanisms underlying these age-related changes are incompletely understood. This study investigated the possible contributions of blood pressure (BP) and left ventricular end-diastolic length (LVEDL) to age-related reductions in E and e`. Methods The study group were 82 healthy adult subjects <55 years of age who were not obese or hypertensive. Transmitral flow and mitral annular motion were recorded using pulsed-wave Doppler. LVEDL was measured from the mitral annular plane to the apical endocardium. Results Age was positively correlated with diastolic BP and septal wall thickness (SWT), inversely correlated with LVEDL (β = -0.25) after adjustment for sex and body surface area, but was not related to left ventricular end-diastolic diameter (LVEDD). Age was also inversely correlated with E (r = -0.36), septal e`(r = -0.53) and lateral e`(r = -0.53). On multivariable analysis, E was inversely correlated with diastolic BP and LVEDD, septal e`was inversely correlated with diastolic BP and positively correlated with SWT and LVEDL, after adjusting for body mass index, whilst lateral e`was inversely correlated with diastolic BP and positively correlated with LVEDL. Conclusion The above findings are consistent with higher BP being a contributor to age-related reductions in both E and e`and shortening of LVEDL with age being a contributor to the age-related reduction in e`. An implication of these findings is that slowing of myocyte relaxation is unlikely to be the sole, and may not be the main, mechanism underlying age-related decreases in E and e`. PMID:27351745

  1. Age-related failure of endocytosis may be the pathogenetic mechanism responsible for cold follicle formation in the aging mouse thyroid

    SciTech Connect

    Gerber, H.; Peter, H.J.; Studer, H.

    1987-05-01

    With advancing age, 60-80% of the follicles of the mouse thyroid gland turn cold, i.e. they lose their normal capacity to iodinate thyroglobulin (Tgb). Cold follicles are morphologically characterized by their large size, by deeply periodic acid-Schiff-stained colloid and by flat epithelial cells. We investigated the hypothesis that a progressive, age-related failure of endocytosis, leading to a gradually increasing mismatch between production of new Tgb and resorption of stored Tgb, could lead to overfilling of colloid stores with consecutive impediment of diffusion. To this purpose, labeling of the thyroids was started when mice were 3 months old, and 125I was continuously administered thereafter for 2-6 months. After this time, all follicles were homogeneously labeled in autoradiographs. Tracer application was then discontinued. Autoradiographs obtained at intervals during the washout of the tracer yielded a mirror image of that observed after acute labeling. The large follicles which were cold after acute labeling in old animals now still retained labeled iodoproteins even after 7 weeks of washout, i.e. at a time when morphologically normal follicles had long lost their labeled Tgb stores. Thus, the cold follicles of the old thyroid must have been functioning normally during equilibration of young thyroids, but have then gradually lost their capacity to iodinate and to remove stored Tgb from the colloid. The observation supports the thesis that aging primarily affects the cytoskeleton and, thus, the cell's endocytotic machinery. This effect of aging on the thyroid can be prevented by life-long stimulation of the gland by TSH.

  2. Comparative study of structure formation and mechanical behavior of age-hardened Ti–Nb–Zr and Ti–Nb–Ta shape memory alloys

    SciTech Connect

    Inaekyan, K.; Brailovski, V.; Prokoshkin, S.; Pushin, V.; Dubinskiy, S.; Sheremetyev, V.

    2015-05-15

    This work sets out to study the peculiar effects of aging treatment on the structure and mechanical behavior of cold-rolled and annealed biomedical Ti–21.8Nb–6.0Zr (TNZ) and Ti–19.7Nb–5.8Ta (TNT) (at.%) shape memory alloys by means of transmission electron microscopy, X-ray diffractometry, functional fatigue and thermomechanical testing techniques. Dissimilar effects of aging treatment on the mechanical behavior of Zr- and Ta-doped alloys are explained by the differences in the ω-phase formation rate, precipitate size, fraction and distribution, and by their effect on the alloys' critical stresses and transformation temperatures. Even short-time aging of the TNZ alloy leads to its drastic embrittlement caused by “overaging”. On the contrary, during aging of the TNT alloy, formation of finely dispersed ω-phase precipitates is gradual and controllable, which makes it possible to finely adjust the TNT alloy functional properties using precipitation hardening mechanisms. To create in this alloy nanosubgrained dislocation substructure containing highly-dispersed coherent nanosized ω-phase precipitates, the following optimum thermomechanical treatment is recommended: cold rolling (true strain 0.37), followed by post-deformation annealing (600 °C, 15–30 min) and age-hardening (300 °C, 30 min) thermal treatments. It is shown that in TNT alloy, pre-transition diffraction effects (diffuse reflections) can “mask” the β-phase substructure and morphology of secondary phases. - Highlights: • TNZ alloy is characterized by much higher ω-phase precipitation rate than TNT alloy. • Difference in precipitation rates is linked to the difference in Zr and Ta diffusion mobility. • Aging of nanosubgrained TNZ alloy worsens its properties irrespective of the aging time. • Aging time of nanosubgrained TNT alloy can be optimized to improve its properties.

  3. Aging management guideline for commercial nuclear power plants - heat exchangers

    SciTech Connect

    Booker, S.; Lehnert, D.; Daavettila, N.; Palop, E.

    1994-06-01

    This Aging Management Guideline (AMG) describes recommended methods for effective detection and mitigation of age-related degradation mechanisms in commercial nuclear power plant heat exchangers important to license renewal. The intent of this AMG is to assist plant maintenance and operations personnel in maximizing the safe, useful life of these components. It also supports the documentation of effective aging management programs required under the License Renewal Rule 10 CFR 54. This AMG is presented in a manner that allows personnel responsible for performance analysis and maintenance to compare their plant-specific aging mechanisms (expected or already experienced) and aging management program activities to the more generic results and recommendations presented herein.

  4. Preventive effect of Vaccinium uliginosum L. extract and its fractions on age-related macular degeneration and its action mechanisms.

    PubMed

    Yoon, Sun-Myung; Lee, Bom-Lee; Guo, Yuan-Ri; Choung, Se-Young

    2016-01-01

    Age-related macular degeneration (AMD) is the leading cause of vision loss and blindness among the elderly. Although the pathogenesis of this disease remains still obscure, several researchers have report that death of retinal pigmented epithelium (RPE) caused by excessive accumulation of A2E is crucial determinants of AMD. In this study, the preventive effect of Vaccinium uliginosum L. (V.U) extract and its fractions on AMD was investigated in blue light-irradiated human RPE cell (ARPE-19 cells). Blue light-induced RPE cell death was significantly inhibited by the treatment of V.U extract or its fraction. To identify the mechanism, FAB-MS analysis revealed that V.U inhibits the photooxidation of N-retinyl-N-retinylidene ethanolamine (A2E) induced by blue light in cell free system. Moreover, monitoring by quantitative HPLC also revealed that V.U extract and its fractions reduced intracellular accumulation of A2E, suggesting that V.U extract and its fractions inhibit not only blue light-induced photooxidation, but also intracellular accumulation of A2E, resulting in RPE cell survival after blue light exposure. A2E-laden cell exposed to blue light induced apoptosis by increasing the cleaved form of caspase-3, Bax/Bcl-2. Additionally, V.U inhibited by the treatment of V.U extract or quercetin-3-O-arabinofuranoside. These results suggest that V.U extract and its fractions have preventive effect on blue light-induced damage in RPE cells and AMD.

  5. Low hydrogen peroxide production in mitochondria of the long-lived Arctica islandica: underlying mechanisms for slow aging.

    PubMed

    Munro, Daniel; Pichaud, Nicolas; Paquin, Frédérique; Kemeid, Vincent; Blier, Pierre U

    2013-08-01

    The observation of an inverse relationship between lifespan and mitochondrial H₂O₂ production rate would represent strong evidence for the disputed oxidative stress theory of aging. Studies on this subject using invertebrates are surprisingly lacking, despite their significance in both taxonomic richness and biomass. Bivalve mollusks represent an interesting taxonomic group to challenge this relationship. They are exposed to environmental constraints such as microbial H₂S, anoxia/reoxygenation, and temperature variations known to elicit oxidative stress. Their mitochondrial electron transport system is also connected to an alternative oxidase that might improve their ability to modulate reactive oxygen species (ROS) yield. Here, we compared H₂O₂ production rates in isolated mantle mitochondria between the longest-living metazoan--the bivalve Arctica islandica--and two taxonomically related species of comparable size. In an attempt to test mechanisms previously proposed to account for a reduction of ROS production in long-lived species, we compared oxygen consumption of isolated mitochondria and enzymatic activity of different complexes of the electron transport system in the two species with the greatest difference in longevity. We found that A. islandica mitochondria produced significantly less H₂O₂ than those of the two short-lived species in nearly all conditions of mitochondrial respiration tested, including forward, reverse, and convergent electron flow. Alternative oxidase activity does not seem to explain these differences. However, our data suggest that reduced complex I and III activity can contribute to the lower ROS production of A. islandica mitochondria, in accordance with previous studies. We further propose that a lower complex II activity could also be involved. PMID:23566066

  6. Student Disengagement in Relation to Expected and Unexpected Educational Pathways

    ERIC Educational Resources Information Center

    Blondal, Kristjana S.; Adalbjarnardottir, Sigrun

    2012-01-01

    Students' different educational pathways were examined in relation to their disengagement during adolescence. The participants were Icelandic youth (N = 832) who were followed from age 14 to 22. Based on their academic achievement at age 15 and educational attainment at age 22 they were classified into groups that took expected versus unexpected…

  7. Developing expectations regarding the boundaries of expertise.

    PubMed

    Landrum, Asheley R; Mills, Candice M

    2015-01-01

    Three experiments examined elementary school-aged children's and adults' expectations regarding what specialists (i.e., those with narrow domains of expertise) and generalists (i.e., those with broad domains of expertise) are likely to know. Experiment 1 demonstrated developmental differences in the ability to differentiate between generalists and specialists, with younger children believing generalists have more specific trivia knowledge than older children and adults believed. Experiment 2 demonstrated that children and adults expected generalists to have more underlying principles knowledge than specific trivia knowledge about unfamiliar animals. However, they believed that generalists would have more of both types of knowledge than themselves. Finally, Experiment 3 demonstrated that children and adults recognized that underlying principles knowledge can be generalized between topics closely related to the specialists' domains of expertise. However, they did not recognize when this knowledge was generalizable to topics slightly less related, expecting generalists to know only as much as they would. Importantly, this work contributes to the literature by showing how much of and what kinds of knowledge different types of experts are expected to have. In sum, this work provides insight into some of the ways children's notions of expertise change over development. The current research demonstrates that between the ages of 5 and 10, children are developing the ability to recognize how experts' knowledge is likely to be limited. That said, even older children at times struggle to determine the breadth of an experts' knowledge. PMID:25460394

  8. Developing expectations regarding the boundaries of expertise.

    PubMed

    Landrum, Asheley R; Mills, Candice M

    2015-01-01

    Three experiments examined elementary school-aged children's and adults' expectations regarding what specialists (i.e., those with narrow domains of expertise) and generalists (i.e., those with broad domains of expertise) are likely to know. Experiment 1 demonstrated developmental differences in the ability to differentiate between generalists and specialists, with younger children believing generalists have more specific trivia knowledge than older children and adults believed. Experiment 2 demonstrated that children and adults expected generalists to have more underlying principles knowledge than specific trivia knowledge about unfamiliar animals. However, they believed that generalists would have more of both types of knowledge than themselves. Finally, Experiment 3 demonstrated that children and adults recognized that underlying principles knowledge can be generalized between topics closely related to the specialists' domains of expertise. However, they did not recognize when this knowledge was generalizable to topics slightly less related, expecting generalists to know only as much as they would. Importantly, this work contributes to the literature by showing how much of and what kinds of knowledge different types of experts are expected to have. In sum, this work provides insight into some of the ways children's notions of expertise change over development. The current research demonstrates that between the ages of 5 and 10, children are developing the ability to recognize how experts' knowledge is likely to be limited. That said, even older children at times struggle to determine the breadth of an experts' knowledge.

  9. Marital and birth expectations of urban adolescents.

    PubMed

    Smith, E A; Zabin, L S

    1993-09-01

    The formation of attitudes conducive to pregnancy prevention is usually included in the development of adolescent pregnancy prevention programs. This research examines the marital and birth expectations among 3646 adolescents enrolled in grades 7-12 in four inner city schools in 1981-82 in the US. The aim is to assess adolescents' perceptions of life experiences in their social environment, which reveal their beliefs about the social acceptability of birth after marriage. Two of the schools had entirely Black student populations, and two for comparison purposes had a mixed student population comprised of 33% Black students. Results reveal that Blacks reported a higher age for marriage and a lower age of first birth than Whites. Blacks had a lower mean ideal age of first birth than for marriage, while White had a lower mean age of marriage than for first birth. 59.1% of Black teenage females and 55% of Black teenage males reported a first birth ideal less than the marriage age, while 20.4% of White teenage females and 21.1% of White teenage males did so. A comparative graph shows Whites having in-wedlock births around 21 years of age and Blacks having in-wedlock births at 26 years of age. The analysis of the best age of marriage regressed on the best age at first birth indicates that the slopes are parallel, and there is no significant difference between Black and White attitudes. Blacks had an ideal marriage age of about two years later than Whites. In the comparison of survey responses to vital statistics data on legitimacy of first births in Baltimore in 1980, it appears that there is a close correspondence between actual out-of-wedlock status of first births and female adolescent attitudes. This study's findings suggest that both Blacks and Whites expect early births to be premarital and later births to be postmarital. Adolescent experiences affect their perceptions, and teenagers' perceptions are fairly realistic. The interpretation of findings is that Black

  10. Age-related deterioration in trabecular bone mechanical properties at material level: nanoindentation study of the femoral neck in women by using AFM.

    PubMed

    Milovanovic, Petar; Potocnik, Jelena; Djonic, Danijela; Nikolic, Slobodan; Zivkovic, Vladimir; Djuric, Marija; Rakocevic, Zlatko

    2012-02-01

    Despite general belief that the mechanical properties of bone material contribute to whole bone strength, it is still obscure what the age effects are on mechanical behavior of the bone material, particularly in the case of the femoral neck trabeculae. In this study, atomic force microscopy was used for imaging and measuring the size of mineral grains, as well as nano-scale mechanical characterization (nanoindentation) of the bone mineralized matrix of trabeculae, with the aim to explore the age effects on bone elasticity and give new insight into age-related bone fragility. The bone samples in this study comprised trabecular bone specimens of the femoral neck region, collected from eight skeletal healthy women (five young adults: 27-38yrs., three elderly: 83-94yrs.) at autopsy. Bone trabeculae in the elderly displayed a higher modulus and nanohardness, signifying a decreased amount of energy that can be accommodated by the bone tissue during loading. Regression analysis revealed that nearly 65% of variability in the bone matrix elastic modulus can be statistically explained by the changes in size of the matrix mineral grains. This study revealed that the bone trabeculae of elderly women express less elastic behavior at the material level, which makes them more vulnerable to unusual impact loads originating from a fall. The observed age-related structural and mechanical alteration at the bone material level adds new evidence for understanding why hip fractures are more frequent in elderly women.

  11. School Achievements, Behavioural Adjustments and Health at Nine Years of Age in a Population of Infants Who Were Born Preterm or Required Prolonged Mechanical Ventilation.

    ERIC Educational Resources Information Center

    Mohay, Heather; And Others

    The prevalence of subtle handicapping conditions, such as learning disabilities, behavior problems, and recurrent illness, in a population of 88 high-risk infants was investigated when the children reached 9 years of age. Infants had had birthweights of less than 1500 grams or had required prolonged mechanical ventilation in the neonatal period.…

  12. Mechanisms of formation of hardening precipitates and hardening in aging of Al-Li-Cu-Mg model alloys with silver additions

    NASA Astrophysics Data System (ADS)

    Alekseev, A. A.; Zhuravleva, P. L.; Onuchina, M. R.; Klochkova, Yu. Yu.

    2015-11-01

    The mechanisms of the influence of silver additions on the phase transformations that occur in aging are revealed. The contribution of Ω'-phase particles to the deformation stress in Al alloys is estimated. The mechanisms of the effect of low (up to 0.5 wt %) silver additions and the copper content on the structure of the Ω'-phase precipitates in Al alloys are found. According to the proposed model, silver atoms remain immobile during the decomposition of a solid solution and nucleation centers of the Ω' phase form near them in low-temperature aging. Upon hardening aging, fragmented Ω'-phase particles intersect with each other, and the contribution of the intersection regions to the hardening of alloys by Ω'-phase particles is principal.

  13. Effects of aging treatment and heat input on the microstructures and mechanical properties of TIG-welded 6061-T6 alloy joints

    NASA Astrophysics Data System (ADS)

    Peng, Dong; Shen, Jun; Tang, Qin; Wu, Cui-ping; Zhou, Yan-bing

    2013-03-01

    Aging treatment and various heat input conditions were adopted to investigate the microstructural evolution and mechanical properties of TIG welded 6061-T6 alloy joints by microstructural observations, microhardness tests, and tensile tests. With an increase in heat input, the width of the heat-affected zone (HAZ) increases and grains in the fusion zone (FZ) coarsen. Moreover, the hardness of the HAZ decreases, whereas that of the FZ decreases initially and then increases with an increase in heat input. Low heat input results in the low ultimate tensile strength of the welded joints due to the presence of partial penetrations and pores in the welded joints. After a simple artificial aging treatment at 175°C for 8 h, the microstructure of the welded joints changes slightly. The mechanical properties of the welded joints enhance significantly after the aging process as few precipitates distribute in the welded seam.

  14. High Hopes and High Expectations!

    ERIC Educational Resources Information Center

    Wilford, Sara

    2006-01-01

    The start of each new school year is an especially hopeful time, and this author has found that clearly communicating expectations for teachers and families can set the stage for a wonderful new school year. This article discusses the expectations of teachers, directors, and families as a new school year begins.

  15. Sibling Status Effects: Adult Expectations.

    ERIC Educational Resources Information Center

    Baskett, Linda Musun

    1985-01-01

    This study attempted to determine what expectations or beliefs adults might hold about a child based on his or her sibling status alone. Ratings on 50 adjective pairs for each of three sibling status types, only, oldest, and youngest child, were assessed in relation to adult expectations, birth order, and parental status of rater. (Author/DST)

  16. Institutional Differences: Expectations and Perceptions.

    ERIC Educational Resources Information Center

    Silver, Harold

    1982-01-01

    The history of higher education has paid scant attention to the attitudes and expectations of its customers, students, and employers of graduates. Recent research on student and employer attitudes toward higher education sectors has not taken into account these expectations in the context of recent higher education history. (Author/MSE)

  17. Genomic medicine: too great expectations?

    PubMed

    O'Rourke, P P

    2013-08-01

    As advances in genomic medicine have captured the interest and enthusiasm of the public, an unintended consequence has been the creation of unrealistic expectations. Because these expectations may have a negative impact on individuals as well as genomics in general, it is important that they be understood and confronted.

  18. Making Your High Expectations Stick

    ERIC Educational Resources Information Center

    Education Digest: Essential Readings Condensed for Quick Review, 2007

    2007-01-01

    Every teacher starts the school year with great expectations for an orderly classroom. An experienced educator has probably tried various approaches to maintain order and create a classroom environment where every student feels comfortable contributing. To let the students know how much is really expected of them, teachers should not simply state…

  19. Expectations of Garland [Junior College].

    ERIC Educational Resources Information Center

    Garland Junior Coll., Boston, MA.

    A survey was conducted at Garland Junior College to determine the educational expectations of 69 new students, 122 parents, and 22 college faculty and administrators. Each group in this private women's college was asked to rank, in terms of expectations they held, the following items: learn job skills, mature in relations with others, become more…

  20. Microstructural evolution and mechanical properties of an Fe-18Ni-16Cr-4Al base alloy during aging at 950°C

    NASA Astrophysics Data System (ADS)

    Wang, Man; Sun, Yong-duo; Feng, Jing-kai; Zhang, Rui-qian; Tang, Rui; Zhou, Zhang-jian

    2016-03-01

    The development of Gen-IV nuclear systems and ultra-supercritical power plants proposes greater demands on structural materials used for key components. An Fe-18Ni-16Cr-4Al (316-base) alumina-forming austenitic steel was developed in our laboratory. Its microstructural evolution and mechanical properties during aging at 950°C were investigated subsequently. Micro-structural changes were characterized by scanning electron microscopy, electron backscatter diffraction, and transmission electron microscopy. Needle-shaped NiAl particles begin to precipitate in austenite after ageing for 10 h, whereas round NiAl particles in ferrite are coarsened during aging. Precipitates of NiAl with different shapes in different matrices result from differences in lattice misfits. The tensile plasticity increases by 32.4% after aging because of the improvement in the percentage of coincidence site lattice grain boundaries, whereas the tensile strength remains relatively high at approximately 790 MPa.

  1. Life expectancy in Canada--an overview.

    PubMed

    Adams, O

    1990-01-01

    At 73 years for men and more than 80 years for women, Canada's life expectancy at birth compares favourably with other developed countries; Japan currently leads the world with 75.6 years for men and 81.4 years for women. In 1920-1922, fewer than six out of ten Canadians could expect to survive to their 65th birthday; by 1985-1987, this had risen to eight out of ten. At the oldest ages, the increases in survival are even more striking. In 1920-1922, just over one in ten Canadians could expect to reach their 85th birthday; by 1985-1987, this had increased to more than three out of ten. Since the 1920s, life expectancy has been higher in the Western provinces and lower in Atlantic Canada and Quebec. In 1950-1952, for example, a person born in Saskatchewan could expect to live four years longer than a person born in Quebec. By 1985-1987, this difference had been reduced to just over one year. Women have made much greater gains in life expectancy than men. In 1920-1922, women had an advantage in life expectancy over men of less than two years; by 1970-1972, this had more than tripled to seven years. Married men and women have a distinct advantage in longevity over other marital status categories. Married men may expect to live over eight years longer than never-married men, and more than ten years longer than widowed men. Married women can expect to live three years longer than never-married women, and four years longer than women who are either divorced or widowed. As of 1986, a boy born in highest-income quintile area in urban Canada can expect to live almost six years longer than a boy born in a lowest-income quintile area. For girls, the difference is almost two years. However, this socio-economic differential narrowed from 1971 to 1986.

  2. Aging of hair.

    PubMed

    Trüeb, Ralph M

    2005-06-01

    The appearance of hair plays an important role in people's overall physical appearance and self-perception. With today's increasing life expectation, the desire to look youthful plays a bigger role than ever. The hair care industry has become aware of this and also more capable to deliver active products that are directed toward meeting this consumer demand. The discovery of pharmacological targets and the development of safe and effective drugs also indicate strategies of the drug industry for maintenance of healthy and beautiful hair. Hair aging comprises weathering of the hair shaft and aging of the hair follicle. The latter manifests as decrease of melanocyte function or graying, and decrease in hair production in androgenetic and senescent alopecia. The scalp is also subject to intrinsic or physiologic aging and extrinsic aging caused by external factors. Intrinsic factors are related to individual genetic and epigenetic mechanisms with interindividual variation. Prototypes are familial premature graying and androgenetic alopecia. Extrinsic factors include ultraviolet radiation and smoking. Experimental evidence supports the hypothesis that oxidative stress plays a role in skin and hair aging. Topical anti-aging compounds for hair include humefactants, hair conditioners, photoprotectors, and antioxidants. Current available treatment modalities with proven efficacy for treatment of androgenetic alopecia are topical minoxidil, oral finasteride, and autologous hair transplantation. In the absence of another way to reverse hair graying, hair colorants are the mainstays of recovering lost hair color. Topical liposome targeting for melanins, genes, and proteins selectively to hair follicles are under current investigation.

  3. Genes of aging.

    PubMed

    Hamet, Pavel; Tremblay, Johanne

    2003-10-01

    According to developmental genetics theories, aging is a genetically programmed and controlled continuum of development and maturation. Being dynamic and malleable processes, development and aging are controlled not only by genes but also by environmental and epigenetic influences that predominate in the second half of life. Genetic mutations affect many phenotypes in flies, worms, rodents, and humans which share several diseases or their equivalents, including cancer, neurodegeneration, and infectious disorders as well as their susceptibility to them. Life span and stress resistance are closely linked. Oxidative stress actually constitutes a defined hypothesis of aging in that macromolecule oxidative damage accumulates with age and tends to be associated with life expectancy. DNA methylation, a force in the regulation of gene expression, is also one of the biomarkers of genetic damage. The mitotic clock of aging is marked, if not guided, by telomeres, essential genetic elements stabilizing natural chromosomic ends. The dream of humans to live longer, healthy lives is being tested by attempts to modify longevity in animal models, frequently by dietary manipulation. The quest continues to understand the mechanisms of healthy aging, one of the most compelling areas of research in the 21st century. PMID:14577056

  4. Effect of membrane stiffness and cytoskeletal element density on mechanical stimuli within cells: an analysis of the consequences of ageing in cells.

    PubMed

    Xue, Feng; Lennon, Alex B; McKayed, Katey K; Campbell, Veronica A; Prendergast, Patrick J

    2015-01-01

    A finite element model of a single cell was created and used to compute the biophysical stimuli generated within a cell under mechanical loading. Major cellular components were incorporated in the model: the membrane, cytoplasm, nucleus, microtubules, actin filaments, intermediate filaments, nuclear lamina and chromatin. The model used multiple sets of tensegrity structures. Viscoelastic properties were assigned to the continuum components. To corroborate the model, a simulation of atomic force microscopy indentation was performed and results showed a force/indentation simulation with the range of experimental results. A parametric analysis of both increasing membrane stiffness (thereby modelling membrane peroxidation with age) and decreasing density of cytoskeletal elements (thereby modelling reduced actin density with age) was performed. Comparing normal and aged cells under indentation predicts that aged cells have a lower membrane area subjected to high strain as compared with young cells, but the difference, surprisingly, is very small and may not be measurable experimentally. Ageing is predicted to have a more significant effect on strain deep in the nucleus. These results show that computation of biophysical stimuli within cells are achievable with single-cell computational models; correspondence between computed and measured force/displacement behaviours provides a high-level validation of the model. Regarding the effect of ageing, the models suggest only small, although possibly physiologically significant, differences in internal biophysical stimuli between normal and aged cells. PMID:23947334

  5. Differential mechanisms of ang (1-7)-mediated vasodepressor effect in adult and aged candesartan-treated rats.

    PubMed

    Bosnyak, S; Widdop, R E; Denton, K M; Jones, E S

    2012-01-01

    Angiotensin (1-7) (Ang (1-7)) causes vasodilator effects in Wistar-Kyoto (WKY) rats and spontaneously hypertensive rats (SHRs) via angiotensin type 2 receptors (AT(2)R). However, the role of vascular AT(2)R in aging is not known. Therefore, we examined the effect of aging on Ang (1-7)-mediated vasodepressor effects and vascular angiotensin receptor localization in aging. Blood pressure was measured in conscious adult (~17 weeks) and aged (~19 months) normotensive rats that received drug combinations in a randomised fashion over a 4-day protocol: (i) Ang (1-7) alone, (ii) AT(1)R antagonist, candesartan, alone, (iii) Ang (1-7) and candesartan, or (iv) Ang-(1-7), candesartan, and the AT(2)R antagonist, PD123319. In a separate group of animals, the specific MasR antagonist, A779, was administered in place of PD123319. Receptor localisation was also assessed in aortic sections from adult and aged WKY rats by immunofluorescence. Ang (1-7) reduced blood pressure (~15 mmHg) in adult normotensive rats although this effect was dependant on the background dose of candesartan. This depressor effect was reversed by AT(2)R blockade. In aged rats, the depressor effect of Ang (1-7) was evident but was now inhibited by either AT(2)R blockade or MasR blockade. At the same time, AT(2)R, MasR, and ACE2 immunoreactivity was markedly elevated in aortic sections from aged animals. These results indicate that the Ang (1-7)-mediated depressor effect was preserved in aged animals. Whereas Ang (1-7) effects were mediated exclusively via stimulation of AT(2)R in adult WKY, with aging the vasodepressor effect of Ang (1-7) involved both AT(2)R and MasR.

  6. Premises and physical mechanisms to explain plateau boundaries in marine planktic 14C records as absolute age markers

    NASA Astrophysics Data System (ADS)

    Sarnthein, Michael; Grootes, Pieter M.

    2010-05-01

    Changes in marine planktic reservoir age variations hamper severely our ability to age calibrate and use marine records as atmospheric 14C records. Genuine atmospheric 14C changes may overlap with changes induced by massive changes in surface ocean hydrography. However, the deglacial Cariaco Basin record (tuned to U/Th ages of the Hulu record) forms a rare case, where the near-surface ocean and its planktic foraminifera may be in reasonably good exchange with the atmosphere, undisturbed by upwelled old deepwater masses. Accordingly, this core was used to connect IntCal09 with the marine record. High-density dating of this core resolved a suite of ~8 sediment sections over glacial-to-interglacial intervals of 400-1500 yr, where planktic 14C ages stay largely constant ("plateaus"), interspersed with sections, where 14C ages rapidly increase with depth ("jumps"). In harmony with IntCal09 we don't discard this pattern and its potentially important information as mere noise but accept it as real, per analogy to 14C plateaus and jumps established for the tree ring calibrated Holocene. This plateau suite was used for plateau tuning in 8 other high-sedimentation rate and high sampling rate (75-200 yr) deep-sea cores. Here, the plateaus with their characteristic internal structure can hardly be ascribed to irregular pulses of extremely high hemipelagic sedimentation rates leading to 5-50 cm long but otherwise undisturbed sediment sections with constant 14C age. The favored explanation is varying atmospheric 14C concentrations reflected in the near-surface ocean. The age difference between locally measured and atmospheric plateau ages in the reference record serves for deducing local planktic reservoir ages. However, occasional but rare millennial-scale events of changing admixture of old deep-ocean waters may disrupt the atmospheric plateaus in deep-sea cores. The latter influence is distinguished by evaluating the complete deglacial plateau suite in each core, keeping

  7. In vivo estimation of the contribution of elastin and collagen to the mechanical properties in the human abdominal aorta: effect of age and sex.

    PubMed

    Astrand, H; Stalhand, J; Karlsson, J; Karlsson, M; Sonesson, B; Länne, T

    2011-01-01

    The mechanical properties of the aorta affect cardiac function and are related to cardiovascular morbidity/mortality. This study was designed to evaluate the isotropic (mainly elastin, elastin(iso)) and anisotropic (mainly collagen, collagen(ani)) material parameters within the human aorta in vivo. Thirty healthy men and women in three different age categories (23-30, 41-54, and 67-72 yr) were included. A novel mechanical model was used to identify the mechanical properties and the strain field with aid of simultaneously recorded pressure and radius in the abdominal aorta. The magnitudes of the material parameters relating to both the stiffness of elastin(iso) and collagen(ani) were in agreement with earlier in vitro studies. The load-bearing fraction attributed to collagen(ani) oscillated from 10 to 30% between diastolic and systolic pressures during the cardiac cycle. With age, stiffness of elastin(iso) increased in men, despite the decrease in elastin content that has been found due to elastolysis. Furthermore, an increase in stiffness of collagen(ani) at high physiological pressure was found. This might be due to increased glycation, as well as changed isoforms of collagen in the aortic wall with age. A marked sex difference was observed, with a much less age-related effect, both on elastin(iso) and collagen(ani) stiffness in women. Possible factors of importance could be the effect of sex hormones, as well as differing collagen isoforms, between the sexes.

  8. Impact of Thermal Aging on the Microstructure Evolution and Mechanical Properties of Lanthanum-Doped Tin-Silver-Copper Lead-Free Solders

    NASA Astrophysics Data System (ADS)

    Sadiq, Muhammad; Pesci, Raphaël; Cherkaoui, Mohammed

    2013-03-01

    An extensive study is made to analyze the impact of pure lanthanum on the microstructure and mechanical properties of Sn-Ag-Cu (SAC) alloys at high temperatures. Different compositions are tested; the temperature applied for the isothermal aging is 150°C, and aging times of 10 h, 25 h, 50 h, 100 h, and 200 h are studied. Optical microscopy with cross-polarized light is used to follow the grain size, which is refined from 8 mm to 1 mm for as-cast samples and is maintained during thermal aging. Intermetallic compounds (IMCs) present inside the bulk Sn matrix affect the mechanical properties of the SAC alloys. Due to high-temperature exposure, these IMCs grow and hence their impact on mechanical properties becomes more significant. This growth is followed by scanning electron microscopy, and energy-dispersive spectroscopy is used for elemental mapping of each phase. A significant refinement in the average size of IMCs of up to 40% is identified for the as-cast samples, and the coarsening rate of these IMCs is slowed by up to 70% with no change in the interparticle spacing. Yield stress and tensile strength are determined through tensile testing at 20°C for as-cast samples and after thermal aging at 150°C for 100 h and 200 h. Both yield stress and tensile strength are increased by up to 20% by minute lanthanum doping.

  9. In vivo confocal Raman microspectroscopy of the human skin: highlighting of spectral markers associated to aging via a research of correlation between Raman and biometric mechanical measurements.

    PubMed

    Eklouh-Molinier, Christophe; Gaydou, Vincent; Froigneux, Emmanuel; Barlier, Pascale; Couturaud, Virginie; Manfait, Michel; Piot, Olivier

    2015-11-01

    Skin plays a protective role against the loss of water and external aggression, including mechanical stresses. These crucial functions are ensured by different cutaneous layers, particularly the stratum corneum (SC). During aging, the human skin reveals some apparent modifications of functionalities such as a loss of elasticity. Our investigations aimed at demonstrating that Raman microspectroscopy, as a label-free technique with a high molecular specificity, is efficient to assess in vivo the molecular composition of the skin and the alterations underwent during aging. Our approach was based on a search for correlation between Raman data collected on healthy female volunteers of different ages (from 21 to 70 years old) by means of a remote confocal Raman and skin firmness measurements used as a reference method. Raman and biometric data were then submitted to a partial least square (PLS)-based data processing. Our experiments demonstrated the potential of Raman microspectroscopy to provide an objective in vivo assessment of the skin "biological age" that can be very different from the "chronological age" of the person. In addition, Raman features sensitive to the elasticity and the fatigability of the SC were highlighted. Thereafter, calibration transfer functions were constructed to show the possibility to compare the results obtained during two distinct measurement campaigns conducted with two Raman probes of the same conception. This approach could lead to several interesting prospects, in particular by objectifying the effects of dermocosmetic products on the superficial layers of the skin and by accessing some underlying molecular mechanisms.

  10. In vivo confocal Raman microspectroscopy of the human skin: highlighting of spectral markers associated to aging via a research of correlation between Raman and biometric mechanical measurements.

    PubMed

    Eklouh-Molinier, Christophe; Gaydou, Vincent; Froigneux, Emmanuel; Barlier, Pascale; Couturaud, Virginie; Manfait, Michel; Piot, Olivier

    2015-11-01

    Skin plays a protective role against the loss of water and external aggression, including mechanical stresses. These crucial functions are ensured by different cutaneous layers, particularly the stratum corneum (SC). During aging, the human skin reveals some apparent modifications of functionalities such as a loss of elasticity. Our investigations aimed at demonstrating that Raman microspectroscopy, as a label-free technique with a high molecular specificity, is efficient to assess in vivo the molecular composition of the skin and the alterations underwent during aging. Our approach was based on a search for correlation between Raman data collected on healthy female volunteers of different ages (from 21 to 70 years old) by means of a remote confocal Raman and skin firmness measurements used as a reference method. Raman and biometric data were then submitted to a partial least square (PLS)-based data processing. Our experiments demonstrated the potential of Raman microspectroscopy to provide an objective in vivo assessment of the skin "biological age" that can be very different from the "chronological age" of the person. In addition, Raman features sensitive to the elasticity and the fatigability of the SC were highlighted. Thereafter, calibration transfer functions were constructed to show the possibility to compare the results obtained during two distinct measurement campaigns conducted with two Raman probes of the same conception. This approach could lead to several interesting prospects, in particular by objectifying the effects of dermocosmetic products on the superficial layers of the skin and by accessing some underlying molecular mechanisms. PMID:26297464

  11. Retinal pigment epithelial cell multinucleation in the aging eye - a mechanism to repair damage and maintain homoeostasis.

    PubMed

    Chen, Mei; Rajapakse, Dinusha; Fraczek, Monika; Luo, Chang; Forrester, John V; Xu, Heping

    2016-06-01

    Retinal pigment epithelial (RPE) cells are central to retinal health and homoeostasis. Dysfunction or death of RPE cells underlies many age-related retinal degenerative disorders particularly age-related macular degeneration. During aging RPE cells decline in number, suggesting an age-dependent cell loss. RPE cells are considered to be postmitotic, and how they repair damage during aging remains poorly defined. We show that RPE cells increase in size and become multinucleate during aging in C57BL/6J mice. Multinucleation appeared not to be due to cell fusion, but to incomplete cell division, that is failure of cytokinesis. Interestingly, the phagocytic activity of multinucleate RPE cells was not different from that of mononuclear RPE cells. Furthermore, exposure of RPE cells in vitro to photoreceptor outer segment (POS), particularly oxidized POS, dose-dependently promoted multinucleation and suppressed cell proliferation. Both failure of cytokinesis and suppression of proliferation required contact with POS. Exposure to POS also induced reactive oxygen species and DNA oxidation in RPE cells. We propose that RPE cells have the potential to proliferate in vivo and to repair defects in the monolayer. We further propose that the conventionally accepted 'postmitotic' status of RPE cells is due to a modified form of contact inhibition mediated by POS and that RPE cells are released from this state when contact with POS is lost. This is seen in long-standing rhegmatogenous retinal detachment as overtly proliferating RPE cells (proliferative vitreoretinopathy) and more subtly as multinucleation during normal aging. Age-related oxidative stress may promote failure of cytokinesis and multinucleation in RPE cells.

  12. Disengagement versus engagement - a need for greater expectations.

    PubMed

    Bell, J Z

    1978-02-01

    An attempt is made to clarify some existing perspectives of successful aging. The environmental milieu of the aged is laden with potent and pervasive implications about successful adaptation. Considerable exploration is required to facilitate a realistic focus upon various theoretical contributions already presented. The influence of stresses and adaptive energy depletions preceding the senescent state is discussed in an effort to facilitate knowledgeable assimilation of the potential impact of the socioeconomic milieu upon the aged. It is the author's contention that the elderly person, upon retirement, presents an adaptive energy reserve highly personalized in its ability to accommodate to change, and especially dependent upon the nature, number and intensity of environmental stressors to adapt, successfully or unsuccessfully, to senescence. Various environmental stressors are identified (e.g., changes in social opportunities and expectations which create new needs and constrict the realm of emotional and vocational influence, thus reducing opportunities and diminishing self-esteem). Heavy emphasis is placed upon role theory, interaction ritual, and transactional analysis. These concepts are extended to the institutional setting - an environment which serves only to magnify mechanisms occurring throghout the social system while adding its own unique dimension to the stressors confronting the elderly.

  13. Head injury in very young children: mechanisms, injury types, and ophthalmologic findings in 100 hospitalized patients younger than 2 years of age.

    PubMed

    Duhaime, A C; Alario, A J; Lewander, W J; Schut, L; Sutton, L N; Seidl, T S; Nudelman, S; Budenz, D; Hertle, R; Tsiaras, W

    1992-08-01

    Head injury in the youngest age group is distinct from that occurring in older children or adults because of differences in mechanisms, injury thresholds, and the frequency with which the question of child abuse is encountered. To analyze some of these characteristics in very young children, the authors prospectively studied 100 consecutively admitted head-injured patients 24 months of age or younger who were drawn from three institutions. Mechanism of injury, injury type, and associated injuries were recorded. All patients underwent ophthalmologic examination to document the presence of retinal hemorrhages. An algorithm incorporating injury type, best history, and associated findings was used to classify each injury as inflicted or accidental. The results confirmed that most head injuries in children younger than 2 years of age occurred from falls, and while different fall heights were associated with different injury types, most household falls were neurologically benign. Using strict criteria, 24% of injuries were presumed inflicted, and an additional 32% were suspicious for abuse, neglect, or social or family problems. Intradural hemorrhage was much more likely to occur from motor vehicle accidents and inflicted injury than from any other mechanism, with the latter being the most common cause of mortality. Retinal hemorrhages were seen in serious accidental head injury but were most commonly encountered in inflicted injury. The presence of more serious injuries associated with particular mechanisms may be related to a predominance of rotational rather than translational forces acting on the head. PMID:1641278

  14. Diets Based on Virgin Olive Oil or Fish Oil but Not on Sunflower Oil Prevent Age-Related Alveolar Bone Resorption by Mitochondrial-Related Mechanisms

    PubMed Central

    Bullon, Pedro; Battino, Maurizio; Varela-Lopez, Alfonso; Perez-Lopez, Patricia; Granados-Principal, Sergio; Ramirez-Tortosa, Maria C.; Ochoa, Julio J.; Cordero, Mario D.; Gonzalez-Alonso, Adrian; Ramirez-Tortosa, César L.; Rubini, Corrado; Zizzi, Antonio; Quiles, José L.

    2013-01-01

    Background/Objectives Aging enhances frequency of chronic diseases like cardiovascular diseases or periodontitis. Here we reproduced an age-dependent model of the periodontium, a fully physiological approach to periodontal conditions, to evaluate the impact of dietary fat type on gingival tissue of young (6 months old) and old (24 months old) rats. Methods/Findings Animals were fed life-long on diets based on monounsaturated fatty acids (MUFA) as virgin olive oil, n-6 polyunsaturated fatty acids (n-6PUFA), as sunflower oil, or n-3PUFA, as fish oil. Age-related alveolar bone loss was higher in n-6PUFA fed rats, probably as a consequence of the ablation of the cell capacity to adapt to aging. Gene expression analysis suggests that MUFA or n-3PUFA allowed mitochondria to maintain an adequate turnover through induction of biogenesis, autophagy and the antioxidant systems, and avoiding mitochondrial electron transport system alterations. Conclusions The main finding is that the enhanced alveolar bone loss associated to age may be targeted by an appropriate dietary treatment. The mechanisms involved in this phenomenon are related with an ablation of the cell capacity to adapt to aging. Thus, MUFA or n-3PUFA might allow mitochondrial maintaining turnover through biogenesis or autophagy. They might also be able to induce the corresponding antioxidant systems to counteract age-related oxidative stress, and do not inhibit mitochondrial electron transport chain. From the nutritional and clinical point of view, it is noteworthy that the potential treatments to attenuate alveolar bone loss (a feature of periodontal disease) associated to age could be similar to some of the proposed for the prevention and treatment of cardiovascular diseases, a group of pathologies recently associated with age-related periodontitis. PMID:24066124

  15. Pro-Insulin-Like Growth Factor-II Ameliorates Age-Related Inefficient Regenerative Response by Orchestrating Self-Reinforcement Mechanism of Muscle Regeneration.

    PubMed

    Ikemoto-Uezumi, Madoka; Uezumi, Akiyoshi; Tsuchida, Kunihiro; Fukada, So-ichiro; Yamamoto, Hiroshi; Yamamoto, Naoki; Shiomi, Kosuke; Hashimoto, Naohiro

    2015-08-01

    Sarcopenia, age-related muscle weakness, increases the frequency of falls and fractures in elderly people, which can trigger severe muscle injury. Rapid and successful recovery from muscle injury is essential not to cause further frailty and loss of independence. In fact, we showed insufficient muscle regeneration in aged mice. Although the number of satellite cells, muscle stem cells, decreases with age, the remaining satellite cells maintain the myogenic capacity equivalent to young mice. Transplantation of young green fluorescent protein (GFP)-Tg mice-derived satellite cells into young and aged mice revealed that age-related deterioration of the muscle environment contributes to the decline in regenerative capacity of satellite cells. Thus, extrinsic changes rather than intrinsic changes in satellite cells appear to be a major determinant of inefficient muscle regeneration with age. Comprehensive protein expression analysis identified a decrease in insulin-like growth factor-II (IGF-II) level in regenerating muscle of aged mice. We found that pro- and big-IGF-II but not mature IGF-II specifically express during muscle regeneration and the expressions are not only delayed but also decreased in absolute quantity with age. Supplementation of pro-IGF-II in aged mice ameliorated the inefficient regenerative response by promoting proliferation of satellite cells, angiogenesis, and suppressing adipogenic differentiation of platelet derived growth factor receptor (PDGFR)α(+) mesenchymal progenitors. We further revealed that pro-IGF-II but not mature IGF-II specifically inhibits the pathological adipogenesis of PDGFRα(+) cells. Together, these results uncovered a distinctive pro-IGF-II-mediated self-reinforcement mechanism of muscle regeneration and suggest that supplementation of pro-IGF-II could be one of the most effective therapeutic approaches for muscle injury in elderly people.

  16. Influence of physical aging on mechanical properties of polymer free films: the prediction of long-term aging effects on the water permeability and dissolution rate of polymer film-coated tablets.

    PubMed

    Guo, J H; Robertson, R E; Amidon, G L

    1991-12-01

    The effects of physical aging on the water permeation of cellulose acetate and ethylcellulose, the mechanical properties of ethylcellulose, and the dissolution property of hydroxypropyl methylcellulose phthalate were investigated. The water permeabilities of cellulose acetate and ethylcellulose and the dissolution rate of hydroxypropyl methylcellulose phthalate were found to decrease with physical aging time after being quenched from above the glass transition temperatures to sub-Tg temperatures. The gradual approach toward thermodynamic equilibrium during physical aging decreases the free volume of the polymers. This decrease in free volume is accompanied by a decrease in the transport mobility, with concomitant changes in those properties of the polymer that depend on it. The effects of long-term aging on the dissolution rate and water permeabilities of these polymers can be estimated from a linear double-logarithmic relationship between the mobility properties and physical aging time. The existence of the linear double-logarithmic relationship can be derived from the Williams-Landel-Ferry equation, the Doolittle equation, Struik's model, and Fujita's relationship between diffusion and free volume.

  17. Alcohol Outcome Expectancies as Socially Shared and Socialized Beliefs

    PubMed Central

    Donovan, John E.; Molina, Brooke S. G.; Kelly, Thomas M.

    2008-01-01

    Alcohol expectancies are important predictors of alcohol involvement in both adolescents and adults, yet little research has examined the social origins and transmission of these beliefs. This paper examined alcohol outcome expectancies collected in a cohort-sequential longitudinal study of 452 families with children followed over seven waves. Children completed interviews every six months, and parents completed interviews annually. Eighteen of 27 alcohol expectancies were highly consensual, being endorsed by significantly more than 67% of the mothers and fathers. These consensual expectancies were also highly stable over a 3-year period. Over the same period, children increased their adoption of both the positive and negative consensual alcohol expectancies. Unconditional latent growth modeling showed that piece-wise growth models with a transition at age 12 fit the data best. Both the positive and negative consensual expectancies were adopted at a faster rate between ages 8.5 and 11.5 than between ages 12 and 13.5. For negative expectancies, there was no further growth between ages 12 and 13.5. Taken together, these findings support the conceptualization of alcohol outcome expectancies as socially-shared and transmitted beliefs. PMID:19586141

  18. Students' Aspirations, Expectations and School Achievement: What Really Matters?

    ERIC Educational Resources Information Center

    Khattab, Nabil

    2015-01-01

    Using the Longitudinal Study of Young People in England (LSYPE), this study examines how different combinations of aspirations, expectations and school achievement can influence students' future educational behaviour (applying to university at the age of 17-18). The study shows that students with either high aspirations or high expectations have…

  19. Physical activity extends life expectancy

    Cancer.gov

    Leisure-time physical activity is associated with longer life expectancy, even at relatively low levels of activity and regardless of body weight, according to a study by a team of researchers led by the NCI.

  20. Effects of thermal aging and neutron irradiation on the mechanical properties of three-wire stainless steel weld overlay cladding

    SciTech Connect

    Haggag, F.M.; Nanstad, R.K.

    1997-05-01

    Thermal aging of three-wire series-arc stainless steel weld overlay cladding at 288{degrees}C for 1605 h resulted in an appreciable decrease (16%) in the Charpy V-notch (CVN) upper-shelf energy (USE), but the effect on the 41-J transition temperature shift was very small (3{degrees}C). The combined effect of aging and neutron irradiation at 288{degrees}C to a fluence of 5 x 10{sup 19} neutrons/cm{sup 2} (> 1 MeV) was a 22% reduction in the USE and a 29{degrees}C shift in the 41-J transition temperature. The effect of thermal aging on tensile properties was very small. However, the combined effect of irradiation and aging was an increase in the yield strength (6 to 34% at test temperatures from 288 to {minus}125{degrees}C) but no apparent change in ultimate tensile strength or total elongation. Neutron irradiation reduced the initiation fracture toughness (J{sub Ic}) much more than did thermal aging alone. Irradiation slightly decreased the tearing modulus, but no reduction was caused by thermal aging alone. Other results from tensile, CVN, and fracture toughness specimens showed that the effects of thermal aging at 288 or 343{degrees}C for 20,000 h each were very small and similar to those at 288{degrees}C for 1605 h. The effects of long-term thermal exposure time (50,000 h and greater) at 288{degrees}C will be investigated as the specimens become available in 1996 and beyond.