Science.gov

Sample records for age-related degradation mechanisms

  1. AGE-RELATED DEGRADATION OF NUCLEAR POWER PLANT STRUCTURES AND COMPONENTS.

    SciTech Connect

    BRAVERMAN,J.

    1999-03-29

    This paper summarizes and highlights the results of the initial phase of a research project on the assessment of aged and degraded structures and components important to the safe operation of nuclear power plants (NPPs). A review of age-related degradation of structures and passive components at NPPs was performed. Instances of age-related degradation have been collected and reviewed. Data were collected from plant generated documents such as Licensing Event Reports, NRC generic communications, NUREGs and industry reports. Applicable cases of degradation occurrences were reviewed and then entered into a computerized database. The results obtained from the review of degradation occurrences are summarized and discussed. Various trending analyses were performed to identify which structures and components are most affected, whether degradation occurrences are worsening, and what are the most common aging mechanisms. The paper also discusses potential aging issues and degradation-susceptible structures and passive components which would have the greatest impact on plant risk.

  2. Age-Related Degradation of Nuclear Power Plant Structures and Components

    SciTech Connect

    Braverman, J.; Chang, T.-Y.; Chokshi, N.; Hofmayer, C.; Morante, R.; Shteyngart, S.

    1999-03-29

    This paper summarizes and highlights the results of the initial phase of a research project on the assessment of aged and degraded structures and components important to the safe operation of nuclear power plants (NPPs). A review of age-related degradation of structures and passive components at NPPs was performed. Instances of age-related degradation have been collected and reviewed. Data were collected from plant generated documents such as Licensing Event Reports, NRC generic communications, NUREGs and industry reports. Applicable cases of degradation occurrences were reviewed and then entered into a computerized database. The results obtained from the review of degradation occurrences are summarized and discussed. Various trending analyses were performed to identify which structures and components are most affected, whether degradation occurrences are worsening, and what was the most common aging mechanisms. The paper also discusses potential aging issues and degradation-susceptible structures and passive components which would have the greatest impact on plant risk.

  3. 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…

  4. 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

  5. Early Age-Related Macular Degeneration Impairs Tolerance To Stimulus Degradation

    PubMed Central

    Liu, Lei; White, Janis

    2010-01-01

    Purpose Pathologic changes of retinal photoreceptors associated with early age-related macular degeneration (AMD) have been well established, but the disease is usually asymptomatic at the early stage and traditional suprathreshold clinical tests often fail to reveal functional deficiencies. The aim of this study is to demonstrate subtle changes of one suprathreshold visual function in early AMD eyes. Methods The quality of pre-attentively discriminable texture stimuli was systematically degraded through random deletion of texture checks. The subjects’ task was to make a forced-choice decision on whether two equally degraded patches contained samples of the same or different types of textures. Tolerance to texture stimulus degradation was measured in young and elderly normal controls and in patients with early AMD. Results Subjects were trained to perform the texture discrimination task until they made few errors in discriminating intact textures. Texture discrimination deteriorated with increasing stimulus degradation in all subjects. There was no significant difference between performance of young and elderly normal controls. Early AMD eyes showed significantly less tolerance to stimulus degradation than age-similar normal controls at a range of degradation levels. After controlling for visual acuity, normal subjects still performed significantly better than early AMD eyes around 22% check deletion. There was no significant difference between better eyes of early AMD patients and fellow eyes of late AMD eyes. Performance on the degraded texture task was not correlated with visual acuity. A mild blur of the stimulus had little effect on discrimination of degraded textures. Conclusions Early AMD may not directly affect suprathreshold visual functions when the stimuli are intact and contain redundant information, but may manifest itself as a reduction of tolerance to stimulus degradation in the form of localized information loss. The performance of patients with

  6. Changes in pattern completion – a key mechanism to explain age-related recognition memory deficits?

    PubMed Central

    Vieweg, Paula; Stangl, Matthias; Howard, Lorelei R.; Wolbers, Thomas

    2016-01-01

    Accurate memory retrieval from partial or degraded input requires the reactivation of memory traces, a hippocampal mechanism termed pattern completion. Age-related changes in hippocampal integrity have been hypothesized to shift the balance of memory processes in favor of the retrieval of already stored information (pattern completion), to the detriment of encoding new events (pattern separation). Using a novel behavioral paradigm, we investigated the impact of cognitive aging (1) on recognition performance across different levels of stimulus completeness, and (2) on potential response biases. Participants were required to identify previously learned scenes among new ones. Additionally, all stimuli were presented in gradually masked versions to alter stimulus completeness. Both young and older adults performed increasingly poorly as the scenes became less complete, and this decline in performance was more pronounced in elderly participants indicative of a pattern completion deficit. Intriguingly, when novel scenes were shown, only the older adults showed an increased tendency to identify these as familiar scenes. In line with theoretical models, we argue that this reflects an age-related bias towards pattern completion. PMID:25597525

  7. 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).…

  8. A complementary role of intracortical inhibition in age-related tactile degradation and its remodelling in humans.

    PubMed

    Pleger, Burkhard; Wilimzig, Claudia; Nicolas, Volkmar; Kalisch, Tobias; Ragert, Patrick; Tegenthoff, Martin; Dinse, Hubert R

    2016-01-01

    Many attempts are currently underway to restore age-related degraded perception, however, the link between restored perception and remodeled brain function remains elusive. To understand remodeling of age-related cortical reorganization we combined functional magnetic resonance imaging (fMRI) with assessments of tactile acuity, perceptual learning, and computational modeling. We show that aging leads to tactile degradation parallel to enhanced activity in somatosensory cortex. Using a neural field model we reconciled the empirical age-effects by weakening of cortical lateral inhibition. Using perceptual learning, we were able to partially restore tactile acuity, which however was not accompanied by the expected attenuation of cortical activity, but by a further enhancement. The neural field model reproduced these learning effects solely through a weakening of the amplitude of inhibition. These findings suggest that the restoration of age-related degraded tactile acuity on the cortical level is not achieved by re-strengthening lateral inhibition but by further weakening intracortical inhibition. PMID:27302219

  9. A complementary role of intracortical inhibition in age-related tactile degradation and its remodelling in humans

    PubMed Central

    Pleger, Burkhard; Wilimzig, Claudia; Nicolas, Volkmar; Kalisch, Tobias; Ragert, Patrick; Tegenthoff, Martin; Dinse, Hubert R.

    2016-01-01

    Many attempts are currently underway to restore age-related degraded perception, however, the link between restored perception and remodeled brain function remains elusive. To understand remodeling of age-related cortical reorganization we combined functional magnetic resonance imaging (fMRI) with assessments of tactile acuity, perceptual learning, and computational modeling. We show that aging leads to tactile degradation parallel to enhanced activity in somatosensory cortex. Using a neural field model we reconciled the empirical age-effects by weakening of cortical lateral inhibition. Using perceptual learning, we were able to partially restore tactile acuity, which however was not accompanied by the expected attenuation of cortical activity, but by a further enhancement. The neural field model reproduced these learning effects solely through a weakening of the amplitude of inhibition. These findings suggest that the restoration of age-related degraded tactile acuity on the cortical level is not achieved by re-strengthening lateral inhibition but by further weakening intracortical inhibition. PMID:27302219

  10. 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

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

    PubMed

    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

  12. 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. PMID:27288490

  13. Calcium dysregulation and neuroinflammation: Discrete and integrated mechanisms for age-related synaptic dysfunction

    PubMed Central

    Sama, Diana M.; Norris, Christopher M.

    2013-01-01

    Some of the best biomarkers of age-related cognitive decline are closely linked to synaptic function and plasticity. This review highlights several age-related synaptic alterations as they relate to Ca2+ dyshomeostasis, through elevation of intracellular Ca2+, and neuroinflammation, through production of pro-inflammatory cytokines including interleukin-1 beta (IL-1β) and tumor necrosis factor-alpha (TNF-α). Though distinct in many ways, Ca2+ and neuroinflammatory signaling mechanisms exhibit extensive cross-talk and bidirectional interactions. For instance, cytokine production in glial cells is strongly dependent on the Ca2+ dependent protein phosphatase calcineurin, which shows elevated activity in animal models of aging and disease. In turn, pro-inflammatory cytokines, such as TNF, can augment the expression/activity of L-type voltage sensitive Ca2+ channels in neurons, leading to Ca2+ dysregulation, hyperactive calcineurin activity, and synaptic depression. Thus, in addition to discussing unique contributions of Ca2+ dyshomeostasis and neuroinflammation, this review emphasizes how these processes interact to hasten age-related synaptic changes. PMID:23751484

  14. Identification and Assessment of Material Models for Age-Related Degradation of Structures and Passive Components in Nuclear Power Plants

    SciTech Connect

    Nie,J.; Braverman, J.; Hofmayer, C.; Kim, M. K.; Choi, I-K.

    2009-04-27

    When performing seismic safety assessments of nuclear power plants (NPPs), the potential effects of age-related degradation on structures, systems, and components (SSCs) should be considered. To address the issue of aging degradation, the Korea Atomic Energy Research Institute (KAERI) has embarked on a five-year research project to develop a realistic seismic risk evaluation system which will include the consideration of aging of structures and components in NPPs. Three specific areas that are included in the KAERI research project, related to seismic probabilistic risk assessment (PRA), are probabilistic seismic hazard analysis, seismic fragility analysis including the effects of aging, and a plant seismic risk analysis. To support the development of seismic capability evaluation technology for degraded structures and components, KAERI entered into a collaboration agreement with Brookhaven National Laboratory (BNL) in 2007. The collaborative research effort is intended to continue over a five year period with the goal of developing seismic fragility analysis methods that consider the potential effects of age-related degradation of SSCs, and using these results as input to seismic PRAs. In the Year 1 scope of work BNL collected and reviewed degradation occurrences in US NPPs and identified important aging characteristics needed for the seismic capability evaluations that will be performed in the subsequent evaluations in the years that follow. This information is presented in the Annual Report for the Year 1 Task, identified as BNL Report-81741-2008 and also designated as KAERI/RR-2931/2008. The report presents results of the statistical and trending analysis of this data and compares the results to prior aging studies. In addition, the report provides a description of U.S. current regulatory requirements, regulatory guidance documents, generic communications, industry standards and guidance, and past research related to aging degradation of SSCs. This report

  15. MECHANISMS OF PESTICIDE DEGRADATION

    EPA Science Inventory

    This research project was initiated with the overall objective of determining (1) the chemical structures of toxic components of toxaphene, (2) to study anaerobic metabolism to degrade toxaphene and other pesticides, and (3) to understand toxic action mechanism of chlordimeform. ...

  16. Age-related changes in lung collagen metabolism. A role for degradation in regulating lung collagen production.

    PubMed

    Mays, P K; McAnulty, R J; Laurent, G J

    1989-08-01

    Lung collagen levels are determined by a balance between synthesis and degradation, processes known to have rapid rates in young animals. Here, we report age-related changes in lung collagen synthesis and degradation in rats at five ages from 1 month to 2 yr. Synthesis rates were determined after injection of [14C]proline with a flooding dose of unlabeled proline, and its appearance as hydroxy-[14C]proline in protein. To determine degradation of newly synthesized collagen, the appearance of hydroxy-[14C]proline, either free or in low-molecular-weight peptides, was compared with hydroxy-[14C]proline in protein. Fractional collagen synthesis rates decreased from 13.51 +/- 0.54%/day at 1 month to 0.97 +/- 0.14%/day at 2 yr of age (p less than 0.05). Total lung collagen production also fell, but only after 15 months, when it decreased from 2.01 +/- 0.16 mg/day at 15 months to 0.54 +/- 0.10 mg/day at 2 yr of age (p less than 0.05). Fractional rates of total collagen degradation, calculated from the difference between rates of synthesis and rates of collagen deposition, decreased 20-fold from 1 month to 2 yr of age. The proportion of newly synthesized collagen degraded increased from 27.6 +/- 3.2% at 1 month to a maximum of 82.3 +/- 1.1% at 15 months. These results suggest that lung collagen synthesis and degradation occur throughout life, and that degradative pathways may play important roles in regulating collagen production during growth and ageing. PMID:2788379

  17. Age-related changes of myocardial ATP supply and demand mechanisms

    PubMed Central

    Yaniv, Yael; Juhaszova, Magdalena; Sollott, Steven J.

    2013-01-01

    In advanced age, the resting myocardial oxygen consumption (M V̇O2) and cardiac work (CW) in the rat remain intact. However, M V̇O2, CW and cardiac efficiency achieved at high demand are decreased with age, compared to maximal values in the young. Whether this deterioration is due to decrease in myocardial ATP demand, ATP supply, or the control mechanisms that match them, remains controversial. Here we discuss evolving perspectives of age-related changes of myocardial ATP supply and demand mechanisms, and critique experimental models used to investigate aging. Specifically, we evaluate experimental data collected at the level of isolated mitochondria, tissue, or organism, and discuss how mitochondrial energetic mechanisms change in advanced age, both at basal and high energy demand levels. PMID:23845538

  18. 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

  19. 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

  20. Age-related hair changes in men: mechanisms and management of alopecia and graying.

    PubMed

    Mirmirani, Paradi

    2015-01-01

    The appearance of human scalp hair is often tied to perceptions of youth and virility, especially in men. Hair loss, or alopecia and hair graying are commonly associated with advancing age and are frequently a source for emotional distress and anxiety. Our understanding of the complex molecular signals and mechanisms that regulate and influence the hair follicle has expanded in recent years. By harnessing this understanding we are poised to address the esthetic concerns of aging hair. Additionally, changes in the hair follicle may be a reflection of systemic senescent signals, thus because of its accessibility, the hair follicle may serve as an important research tool in gerontology. In this review, the most current knowledge and research regarding mechanisms of androgenetic alopecia, senescent alopecia, and graying are discussed, as are extrinsic factors that may contribute to hair changes with age. Evidence based management strategies for treatment of age-related hair changes are also reviewed. PMID:25466305

  1. Potential mechanisms underlying the role of chronic inflammation in age-related muscle wasting.

    PubMed

    Jo, Edward; Lee, Sang-Rok; Park, Bong-Sup; Kim, Jeong-Su

    2012-10-01

    Sarcopenia, an age-related condition characterized by progressive skeletal muscle degeneration, might exist as one of the primary clinical conditions underlying severe functional impairment as well as increased risk of co-morbidities in the elderly. Although the etiology of sarcopenia remains multifaceted, age-related chronic inflammation has been strongly implicated in muscle wasting and related sequelae during advanced age. Recent evidence suggests that aberrant, unresolved alterations in regular inflammatory processes during advanced age might ultimately operate as the link that drives skeletal muscle to become more degenerative and dysfunctional in nature. Such negative atrophic muscular outcomes might result from inflammation-induced disruption of central mechanisms regulating skeletal muscle morphology and remodeling. In addition, recent findings demonstrate an adverse confluence between sarcopenia and excessive adiposity (i.e. sarcopenic obesity), as the co-existence of such adverse alterations in body composition may exacerbate systemic inflammation and muscle wasting in the elderly. The following evidence-based review serves to examine sarcopenia from a mechanistic perspective with emphasis on chronic inflammation. PMID:22717404

  2. Age-Related Neurodegeneration Prevention Through mTOR Inhibition: Potential Mechanisms and Remaining Questions

    PubMed Central

    Jahrling, Jordan B.; Laberge, Remi-Martin

    2016-01-01

    With the global aging population, Alzheimer's disease, Parkinson's disease and mild cognition impairment are increasing in prevalence. The success of rapamycin as an agent to extend lifespan in various organisms, including mice, brings hope that chronic mTOR inhibition could also refrain age-related neurodegeneration. Here we review the evidence suggesting that mTOR inhibition - mainly with rapamycin - is a valid intervention to delay age-related neurodegeneration. We discuss the potential mechanisms by which rapamycin may facilitate neurodegeneration prevention or restoration of cognitive function. We also discuss the known side effects of rapamycin and provide evidence to alleviate exaggerated concerns regarding its wider clinical use. We explore the small molecule alternatives to rapamycin and propose future directions for their development, mainly by exploring the possibility of targeting the downstream effectors of mTOR: S6K1 and especially S6K2. Finally, we discuss the strengths and weaknesses of the models used to determine intervention efficacy for neurodegeneration. We address the difficulties of interpreting data using the common way of investigating the efficacy of interventions to delay/prevent neurodegeneration by observing animal behavior while these animals are under treatment. We propose an experimental design that should isolate the variable of aging in the experimental design and resolve the ambiguity present in recent literature. PMID:26059360

  3. 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. PMID:25773985

  4. Age related differences in mechanical demands imposed on the lower back by manual material handling tasks.

    PubMed

    Shojaei, Iman; Vazirian, Milad; Croft, Emily; Nussbaum, Maury A; Bazrgari, Babak

    2016-04-11

    The prevalence of low back pain (LBP) increases with age, yet the underlying mechanism(s) responsible for this remains unclear. To explore the role of biomechanical factors, we investigated age-related differences in lower-back biomechanics during sagittally-symmetric simulated manual material handling tasks. For each task, trunk kinematics and mechanical demand on the lower back were examined, from among 60 participants within five equal-sized and gender-balanced age groups spanning from 20 to 70 years old. The tasks involved lowering a 4.5kg load from an upright standing posture to both knee height and a fixed height and then lifting the load back to the initial upright posture. During these tasks, segmental body kinematics and ground reaction forces were collected using wireless inertial measurement units and a force platform. Overall, older participants completed the tasks with larger pelvic rotation and smaller lumbar flexion. Such adopted trunk kinematics resulted in larger peak shearing demand at the lower back in older vs. younger participants. These results suggest that older individuals may be at a higher risk for developing lower back pain when completing similar manual material handling tasks, consistent with epidemiological evidence for higher risks of occupational low back pain among this cohort. PMID:26556714

  5. Age-related changes in collagen synthesis and degradation in rat tissues. Importance of degradation of newly synthesized collagen in regulating collagen production.

    PubMed

    Mays, P K; McAnulty, R J; Campa, J S; Laurent, G J

    1991-06-01

    During developmental growth, collagens are believed to be continuously deposited into an extracellular matrix which is increasingly stabilized by the formation of covalent cross-links throughout life. However, the age-related changes in rates of synthetic and degradative processes are less well understood. In the present study we measured rates of collagen synthesis in vivo using a flooding dose of unlabelled proline given with [14C]proline and determining production of hydroxy[14C]proline. Degradation of newly synthesized collagen was estimated from the amount of free hydroxy [14C]proline in tissues 30 min after injection. Collagen fractional synthesis rates ranged from about 5%/day in skeletal muscle to 20%/day in hearts of rats aged 1 month. At 15 months of age, collagen fractional synthesis rates had decreased markedly in lung and skin, but in skeletal muscle and heart, rates were unchanged. At 24 months of age, synthesis rates had decreased by at least 10-fold in all tissues, compared with rates at 1 month. The proportion of newly synthesized collagen degraded ranged from 6.4 +/- 0.4% in skin to 61.6 +/- 5.0% in heart at 1 month of age. During aging the proportion degraded increased in all tissues to maximal values at 15 months, ranging from 56 +/- 7% in skin to 96 +/- 1% in heart. These data suggest that there are marked age-related changes in rates of collagen metabolism. They also indicate that synthesis is active even in old animals, where the bulk of collagens produced are destined to be degraded. PMID:2049064

  6. 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

  7. Circadian and age-related modulation of thermoreception and temperature regulation: mechanisms and functional implications.

    PubMed

    Van Someren, Eus J W; Raymann, Roy J E M; Scherder, Erik J A; Daanen, Hein A M; Swaab, Dick F

    2002-09-01

    At older ages, the circadian rhythm of body temperature shows a decreased amplitude, an advanced phase, and decreased stability. The present review evaluates to what extent these changes may result from age-related deficiencies at several levels of the thermoregulatory system, including thermoreception, thermogenesis and conservation, heat loss, and central regulation. Whereas some changes are related to the aging process per se, others appear to be secondary to other factors, for which the risk increases with aging, notably a decreased level of fitness and physical activity. Moreover, functional implications of the body temperature rhythm are discussed. For example, the relation between circadian rhythm and thermoregulation has hardly been investigated, while evidence showed that sleep quality is dependent on both aspects. It is proposed that the circadian rhythm in temperature in homeotherms should not be regarded as a leftover of ectothermy in early evolution, but appears to be of functional significance for physiology from the level of molecules to cognition. A new view on the functional significance of the circadian rhythm in peripheral vasodilation and the consequent out-of-phase rhythms in skin and core temperature is presented. It is unlikely that the strong, daily occurring, peripheral vasodilation primarily represents heat loss in response to a lowering of set point, since behavioral measures are simultaneously taken in order to prevent heat loss. Several indications rather point towards a supportive role in immunological host defense mechanisms. Given the functional significance of the temperature rhythm, research should focus on the feasibility and effectiveness of methods that can in principle be applied in order to enhance the weakened circadian temperature rhythm in the elderly. PMID:12208240

  8. Smoking and age-related macular degeneration: biochemical mechanisms and patient support.

    PubMed

    Willeford, Kevin T; Rapp, Jerry

    2012-11-01

    A small percentage of the population associates smoking with ocular disease. Most optometrists do not stress the importance of smoking cessation to their patients, and the centrality of smoking regarding the risk for ocular disease is not emphasized in optometric education. Age-related macular degeneration has strong epidemiological associations with smoking, and so serves as an appropriate model for the adverse effects of cigarette smoke on the eye. This article aims to provide basic scientific information to optometrists and optometry students so that they can better understand the pathogenesis of age-related macular degeneration and provide education and support to their patients wishing to stop smoking. PMID:23034338

  9. 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

  10. 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

  11. Molecular Mechanism for Age-Related Memory Loss: The Histone-Binding Protein RbAp48

    PubMed Central

    Pavlopoulos, Elias; Jones, Sidonie; Kosmidis, Stylianos; Close, Maggie; Kim, Carla; Kovalerchik, Olga; Small, Scott A.; Kandel, Eric R.

    2016-01-01

    To distinguish age-related memory loss more explicitly from Alzheimer’s disease (AD), we have explored its molecular underpinning in the dentate gyrus (DG), a subregion of the hippocampal formation thought to be targeted by aging. We carried out a gene expression study in human postmortem tissue harvested from both DG and entorhinal cortex (EC), a neighboring subregion unaffected by aging and known to be the site of onset of AD. Using expression in the EC for normalization, we identified 17 genes that manifested reliable age-related changes in the DG. The most significant change was an age-related decline in RbAp48, a histone-binding protein that modifies histone acetylation. To test whether the RbAp48 decline could be responsible for age-related memory loss, we turned to mice and found that, consistent with humans, RbAp48 was less abundant in the DG of old than in young mice. We next generated a transgenic mouse that expressed a dominant-negative inhibitor of RbAp48 in the adult forebrain. Inhibition of RbAp48 in young mice caused hippocampus-dependent memory deficits similar to those associated with aging, as measured by novel object recognition and Morris water maze tests. Functional magnetic resonance imaging studies showed that within the hippocampal formation, dysfunction was selectively observed in the DG, and this corresponded to a regionally selective decrease in histone acetylation. Up-regulation of RbAp48 in the DG of aged wild-type mice ameliorated age-related hippocampus-based memory loss and age-related abnormalities in histone acetylation. Together, these findings show that the DG is a hippocampal subregion targeted by aging, and identify molecular mechanisms of cognitive aging that could serve as valid targets for therapeutic intervention. PMID:23986399

  12. Molecular mechanism for age-related memory loss: the histone-binding protein RbAp48.

    PubMed

    Pavlopoulos, Elias; Jones, Sidonie; Kosmidis, Stylianos; Close, Maggie; Kim, Carla; Kovalerchik, Olga; Small, Scott A; Kandel, Eric R

    2013-08-28

    To distinguish age-related memory loss more explicitly from Alzheimer's disease (AD), we have explored its molecular underpinning in the dentate gyrus (DG), a subregion of the hippocampal formation thought to be targeted by aging. We carried out a gene expression study in human postmortem tissue harvested from both DG and entorhinal cortex (EC), a neighboring subregion unaffected by aging and known to be the site of onset of AD. Using expression in the EC for normalization, we identified 17 genes that manifested reliable age-related changes in the DG. The most significant change was an age-related decline in RbAp48, a histone-binding protein that modifies histone acetylation. To test whether the RbAp48 decline could be responsible for age-related memory loss, we turned to mice and found that, consistent with humans, RbAp48 was less abundant in the DG of old than in young mice. We next generated a transgenic mouse that expressed a dominant-negative inhibitor of RbAp48 in the adult forebrain. Inhibition of RbAp48 in young mice caused hippocampus-dependent memory deficits similar to those associated with aging, as measured by novel object recognition and Morris water maze tests. Functional magnetic resonance imaging studies showed that within the hippocampal formation, dysfunction was selectively observed in the DG, and this corresponded to a regionally selective decrease in histone acetylation. Up-regulation of RbAp48 in the DG of aged wild-type mice ameliorated age-related hippocampus-based memory loss and age-related abnormalities in histone acetylation. Together, these findings show that the DG is a hippocampal subregion targeted by aging, and identify molecular mechanisms of cognitive aging that could serve as valid targets for therapeutic intervention. PMID:23986399

  13. Possible Molecular Mechanisms Underlying Age-Related Cardiomyocyte Apoptosis in the F344XBN Rat Heart

    PubMed Central

    Kakarla, Sunil K.; Rice, Kevin M.; Katta, Anjaiah; Paturi, Satyanarayana; Wu, Miaozong; Kolli, Madhukar; Keshavarzian, Saba; Manzoor, Kamran; Wehner, Paulette S.

    2010-01-01

    Despite advances in treatment, age-related cardiac dysfunction still remains a leading cause of cardiovascular death. Recent data have suggested that increases in cardiomyocyte apoptosis may be involved in the pathological remodeling of heart. Here, we examine the effects of aging on cardiomyocyte apoptosis in 6-, 30-, and 36-month-old Fischer344xBrown Norway F1 hybrid rats (F344XBN). Compared with 6-month hearts, aged hearts exhibited increased TdT-mediated dUTP nick end labeling–positive nuclei, caspase-3 activation, caspase-dependent cleavage of α-fodrin and diminished phosphorylation of protein kinase B/Akt (Thr 308). These age-dependent increases in cardiomyocyte apoptosis were associated with alterations in the composition of the cardiac dystrophin glycoprotein complex and elevated cytoplasmic IgG and albumin immunoreactivity. Immunohistochemical analysis confirmed these data and demonstrated qualitative differences in localization of dystrophin–glycoprotein complex (DGC) molecules with aging. Taken together, these data suggest that aging-related increases in cardiac apoptotic activity model may be due, at least in part, to age-associated changes in DGC structure. PMID:20056683

  14. 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

  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. Cellular and molecular mechanisms of age-related macular degeneration: from impaired autophagy to neovascularization.

    PubMed

    Klettner, Alexa; Kauppinen, Anu; Blasiak, Janusz; Roider, Johan; Salminen, Antero; Kaarniranta, Kai

    2013-07-01

    Age-related macular degeneration (AMD) is a complex, degenerative and progressive disease involving multiple genetic and environmental factors. It can result in severe visual loss e.g. AMD is the leading cause of blindness in the elderly in the western countries. Although age, genetics, diet, smoking, and many cardiovascular factors are known to be linked with this disease there is increasing evidence that long-term oxidative stress, impaired autophagy clearance and inflammasome mediated inflammation are involved in the pathogenesis. Under certain conditions these may trigger detrimental processes e.g. release of vascular endothelial growth factor (VEGF), causing choroidal neovascularization e.g. in wet AMD. This review ties together these crucial pathological threads in AMD. PMID:23603148

  17. 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

  18. Age-related changes in attentional selection: quality of task set or degradation of task set across time?

    PubMed

    Jackson, Jonathan D; Balota, David A

    2013-09-01

    The present study explores the nature of attentional selection in younger and older adults. Following R. De Jong, E. Berendsen, and R. Cools (1999, Acta Psychologica, Vol. 101, pp. 379-394), we manipulated the response to stimulus interval (RSI) in two attentional selection paradigms to examine if there are age-related differences in the quality of task set and/or the maintenance of task set across time. In Experiment 1, we found that the interference effect in a spatial interference task was (a) overall larger in older adults compared with younger adults, and (b) smaller at the short RSI (200 ms) compared with the long RSI (2000 ms), and (c) not associated with an interaction between age and RSI. The second experiment explored the same variables in a Stroop color interference paradigm. Again, older adults produced a disproportionately larger interference effect than younger adults, the interference effect was smaller at the short RSI compared with the long RSI, and there was no evidence of an interaction between age and RSI. In both experiments, the larger interference effect could not be attributed to age-related general slowing and there was evidence from Vincentile analyses of increasing interference and age effects at the slower response latencies. These results indicate that attentional selection deficits in these two experiments were due to a breakdown in the quality of the task set as opposed to age-related differences in the maintenance of the task set across time. PMID:23834491

  19. Review of Recent Aging-Related Degradation Occurrences of Structures and Passive Components in U.S. Nuclear Power Plants

    SciTech Connect

    Nie,J.; Braverman, J.; Hofmayer, C.; Choun, Y.-S.; Kim, M.K.; Choi, I.-K.

    2009-04-02

    The Korea Atomic Energy Research Institute (KAERI) and Brookhaven National Laboratory (BNL) are collaborating to develop seismic capability evaluation technology for degraded structures and passive components (SPCs) under a multi-year research agreement. To better understand the status and characteristics of degradation of SPCs in nuclear power plants (NPPs), the first step in this multi-year research effort was to identify and evaluate degradation occurrences of SPCs in U.S. NPPs. This was performed by reviewing recent publicly available information sources to identify and evaluate the characteristics of degradation occurrences and then comparing the information to the observations in the past. Ten categories of SPCs that are applicable to Korean NPPs were identified, comprising of anchorage, concrete, containment, exchanger, filter, piping system, reactor pressure vessel, structural steel, tank, and vessel. Software tools were developed to expedite the review process. Results from this review effort were compared to previous data in the literature to characterize the overall degradation trends.

  20. 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

  1. Decorin expression is important for age-related changes in tendon structure and mechanical properties.

    PubMed

    Dunkman, Andrew A; Buckley, Mark R; Mienaltowski, Michael J; Adams, Sheila M; Thomas, Stephen J; Satchell, Lauren; Kumar, Akash; Pathmanathan, Lydia; Beason, David P; Iozzo, Renato V; Birk, David E; Soslowsky, Louis J

    2013-01-01

    The aging population is at an increased risk of tendon injury and tendinopathy. Elucidating the molecular basis of tendon aging is crucial to understanding the age-related changes in structure and function in this vulnerable tissue. In this study, the structural and functional features of tendon aging are investigated. In addition, the roles of decorin and biglycan in the aging process were analyzed using transgenic mice at both mature and aged time points. Our hypothesis is that the increase in tendon injuries in the aging population is the result of altered structural properties that reduce the biomechanical function of the tendon and consequently increase susceptibility to injury. Decorin and biglycan are important regulators of tendon structure and therefore, we further hypothesized that decreased function in aged tendons is partly the result of altered decorin and biglycan expression. Biomechanical analyses of mature (day 150) and aged (day 570) patellar tendons revealed deteriorating viscoelastic properties with age. Histology and polarized light microscopy demonstrated decreased cellularity, alterations in tenocyte shape, and reduced collagen fiber alignment in the aged tendons. Ultrastructural analysis of fibril diameter distributions indicated an altered distribution in aged tendons with an increase of large diameter fibrils. Aged wild type tendons maintained expression of decorin which was associated with the structural and functional changes seen in aged tendons. Aged patellar tendons exhibited altered and generally inferior properties across multiple assays. However, decorin-null tendons exhibited significantly decreased effects of aging compared to the other genotypes. The amelioration of the functional deficits seen in the absence of decorin in aged tendons was associated with altered tendon fibril structure. Fibril diameter distributions in the decorin-null aged tendons were comparable to those observed in the mature wild type tendon with the absence

  2. Decorin expression is important for age-related changes in tendon structure and mechanical properties

    PubMed Central

    Dunkman, Andrew A.; Buckley, Mark R.; Mienaltowski, Michael J.; Adams, Sheila M.; Thomas, Stephen J.; Satchell, Lauren; Kumar, Akash; Pathmanathan, Lydia; Beason, David P.; Iozzo, Renato V.; Birk, David E.; Soslowsky, Louis J.

    2013-01-01

    The aging population is at an increased risk of tendon injury and tendinopathy. Elucidating the molecular basis of tendon aging is crucial to understanding the age-related changes in structure and function in this vulnerable tissue. In this study, the structural and functional features of tendon aging are investigated. In addition, the roles of decorin and biglycan in the aging process were analyzed using transgenic mice at both mature and aged time points. Our hypothesis is that the increase in tendon injuries in the aging population is the result of altered structural properties that reduce the biomechanical function of the tendon and consequently increase susceptibility to injury. Decorin and biglycan are important regulators of tendon structure and therefore, we further hypothesized that decreased function in aged tendons is partly the result of altered decorin and biglycan expression. Biomechanical analyses of mature (day 150) and aged (day 570) patellar tendons revealed deteriorating viscoelastic properties with age. Histology and polarized light microscopy demonstrated decreased cellularity, alterations in tenocyte shape, and reduced collagen fiber alignment in the aged tendons. Ultrastructural analysis of fibril diameter distributions indicated an altered distribution in aged tendons with an increase of large diameter fibrils. Aged wild type tendons maintained expression of decorin which was associated with the structural and functional changes seen in aged tendons. Aged patellar tendons exhibited altered and generally inferior properties across multiple assays. However, decorin-null tendons exhibited significantly decreased effects of aging compared to the other genotypes. The amelioration of the functional deficits seen in the absence of decorin in aged tendons was associated with altered tendon fibril structure. Fibril diameter distributions in the decorin-null aged tendons were comparable to those observed in the mature wild type tendon with the absence

  3. 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

  4. An integrated approach towards identifying age-related mechanisms of slip initiated falls

    PubMed Central

    Lockhart, Thurmon E.

    2008-01-01

    The causes of slip and fall accidents, both in terms of extrinsic and intrinsic factors and their associations are not yet fully understood. Successful intervention solutions for reducing slip and fall accidents require a more complete understanding of the mechanisms involved. Before effective fall prevention strategies can be put into practice, it is central to examine the chain of events in an accident, comprising the exposure to hazards, initiation of events and the final outcome leading to injury and disability. These events can be effectively identified and analyzed by applying epidemiological, psychophysical, biomechanical and tribological research principles and methodologies. In this manuscript, various methods available to examine fall accidents and their underlying mechanisms are presented to provide a comprehensive array of information to help pinpoint the needs and requirements of new interventions aimed at reducing the risk of falls among the growing elderly population. PMID:17768070

  5. 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.

  6. 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

  7. 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

  8. Thermal battery degradation mechanisms

    SciTech Connect

    Missert, Nancy A.; Brunke, Lyle Brent

    2015-09-01

    Diffuse reflectance IR spectroscopy (DRIFTS) was used to investigate the effect of accelerated aging on LiSi based anodes in simulated MC3816 batteries. DRIFTS spectra showed that the oxygen, carbonate, hydroxide and sulfur content of the anodes changes with aging times and temperatures, but not in a monotonic fashion that could be correlated to phase evolution. Bands associated with sulfur species were only observed in anodes taken from batteries aged in wet environments, providing further evidence for a reaction pathway facilitated by H2S transport from the cathode, through the separator, to the anode. Loss of battery capacity with accelerated aging in wet environments was correlated to loss of FeS2 in the catholyte pellets, suggesting that the major contribution to battery performance degradation results from loss of active cathode material.

  9. 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...

  10. 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

  11. Lifelong Cyclic Mechanical Strain Promotes Large Elastic Artery Stiffening: Increased Pulse Pressure and Old Age-Related Organ Failure.

    PubMed

    Thorin-Trescases, Nathalie; Thorin, Eric

    2016-05-01

    The arterial wall is under a huge mechanical constraint imposed by the cardiac cycle that is bound to generate damage with time. Each heartbeat indeed imposes a pulsatile pressure that generates a vascular stretch. Lifetime accumulation of pulsatile stretches will eventually induce fatigue of the elastic large arterial walls, such as aortic and carotid artery walls, promoting their stiffening that will gradually perturb the normal blood flow and local pressure within the organs, and lead to organ failure. The augmented pulse pressure induced by arterial stiffening favours left ventricular hypertrophy because of the repeated extra work against stiff high-pressure arteries, and tissue damage as a result of excessive pulsatile pressure transmitted into the microcirculation, especially in low resistance/high-flow organs such as the brain and kidneys. Vascular aging is therefore characterized by the stiffening of large elastic arteries leading to a gradual increase in pulse pressure with age. In this review we focus on the effect of age-related stiffening of large elastic arteries. We report the clinical evidence linking arterial stiffness and organ failure and discuss the molecular pathways that are activated by the increase of mechanical stress in the wall. We also discuss the possible interventions that could limit arterial stiffening with age, such as regular aerobic exercise training, and some pharmacological approaches. PMID:26961664

  12. 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

  13. Unraveling a Multifactorial Late-Onset Disease: From Genetic Susceptibility to Disease Mechanisms for Age-Related Macular Degeneration

    PubMed Central

    Swaroop, Anand; Chew, Emily Y.; Rickman, Catherine Bowes; Abecasis, Gonçalo R.

    2012-01-01

    Aging-associated neurodegenerative diseases significantly influence the quality of life of affected individuals. Genetic approaches, combined with genomic technology, have provided powerful insights into common late-onset diseases, such as age-related macular degeneration (AMD). Here, we discuss current findings on the genetics of AMD to highlight areas of rapid progress and new challenges. We also attempt to integrate available genetic and biochemical data with cellular pathways involved in aging to formulate an integrated model of AMD pathogenesis. PMID:19405847

  14. Ultrastructure of the liver microcirculation influences hepatic and systemic insulin activity and provides a mechanism for age-related insulin resistance.

    PubMed

    Mohamad, Mashani; Mitchell, Sarah Jayne; Wu, Lindsay Edward; White, Melanie Yvonne; Cordwell, Stuart James; Mach, John; Solon-Biet, Samantha Marie; Boyer, Dawn; Nines, Dawn; Das, Abhirup; Catherine Li, Shi-Yun; Warren, Alessandra; Hilmer, Sarah Nicole; Fraser, Robin; Sinclair, David Andrew; Simpson, Stephen James; de Cabo, Rafael; Le Couteur, David George; Cogger, Victoria Carroll

    2016-08-01

    While age-related insulin resistance and hyperinsulinemia are usually considered to be secondary to changes in muscle, the liver also plays a key role in whole-body insulin handling and its role in age-related changes in insulin homeostasis is largely unknown. Here, we show that patent pores called 'fenestrations' are essential for insulin transfer across the liver sinusoidal endothelium and that age-related loss of fenestrations causes an impaired insulin clearance and hyperinsulinemia, induces hepatic insulin resistance, impairs hepatic insulin signaling, and deranges glucose homeostasis. To further define the role of fenestrations in hepatic insulin signaling without any of the long-term adaptive responses that occur with aging, we induced acute defenestration using poloxamer 407 (P407), and this replicated many of the age-related changes in hepatic glucose and insulin handling. Loss of fenestrations in the liver sinusoidal endothelium is a hallmark of aging that has previously been shown to cause deficits in hepatic drug and lipoprotein metabolism and now insulin. Liver defenestration thus provides a new mechanism that potentially contributes to age-related insulin resistance. PMID:27095270

  15. O-atom degradation mechanisms of materials

    NASA Technical Reports Server (NTRS)

    Coulter, Daniel R.; Liang, Ranty H.; Chung, Shirley Y.; Smith, Keri Oda; Gupta, Amitava

    1987-01-01

    The low Earth orbit environment is described and the critical issues relating to oxygen atom degradation are discussed. Some analytic techniques for studying the problem and preliminary results on the underlying degradation mechanisms are presented.

  16. Inhibition of Age-Related Cytokines Production by ATGL: A Mechanism Linked to the Anti-Inflammatory Effect of Resveratrol

    PubMed Central

    Lettieri Barbato, Daniele; Tatulli, Giuseppe; Aquilano, Katia; Ciriolo, Maria R.

    2014-01-01

    Ageing is characterized by the expansion and the decreased vascularization of visceral adipose tissue (vAT), disruption of metabolic activities, and decline of the function of the immune system, leading to chronic inflammatory states. We previously demonstrated that, in vAT of mice at early state of ageing, adipocytes mount a stress resistance response consisting in the upregulation of ATGL, which is functional in restraining the production of inflammatory cytokines. Here, we found that, in the late phase of ageing, such an adaptive response is impaired. In particular, 24-months-old mice and aged 3T3-L1 adipocytes display affected expression of ATGL and its downstream PPARα-mediated lipid signalling pathway, leading to upregulation of TNFα and IL-6 production. We show that the natural polyphenol compound resveratrol (RSV) efficiently suppresses the expression of TNFα and IL-6 in an ATGL/PPARα dependent manner. Actually, adipocytes downregulating ATGL do not show a restored PPARα expression and display elevated cytokines production. Overall the results obtained highlight a crucial function of ATGL in inhibiting age-related inflammation and reinforce the idea that RSV could represent a valid natural compound to limit the onset and/or the exacerbation of the age-related inflammatory states. PMID:24817795

  17. Inhibition of age-related cytokines production by ATGL: a mechanism linked to the anti-inflammatory effect of resveratrol.

    PubMed

    Lettieri Barbato, Daniele; Tatulli, Giuseppe; Aquilano, Katia; Ciriolo, Maria R

    2014-01-01

    Ageing is characterized by the expansion and the decreased vascularization of visceral adipose tissue (vAT), disruption of metabolic activities, and decline of the function of the immune system, leading to chronic inflammatory states. We previously demonstrated that, in vAT of mice at early state of ageing, adipocytes mount a stress resistance response consisting in the upregulation of ATGL, which is functional in restraining the production of inflammatory cytokines. Here, we found that, in the late phase of ageing, such an adaptive response is impaired. In particular, 24-months-old mice and aged 3T3-L1 adipocytes display affected expression of ATGL and its downstream PPARα-mediated lipid signalling pathway, leading to upregulation of TNFα and IL-6 production. We show that the natural polyphenol compound resveratrol (RSV) efficiently suppresses the expression of TNFα and IL-6 in an ATGL/PPARα dependent manner. Actually, adipocytes downregulating ATGL do not show a restored PPARα expression and display elevated cytokines production. Overall the results obtained highlight a crucial function of ATGL in inhibiting age-related inflammation and reinforce the idea that RSV could represent a valid natural compound to limit the onset and/or the exacerbation of the age-related inflammatory states. PMID:24817795

  18. The implications of age-related neurofunctional compensatory mechanisms in executive function and language processing including the new Temporal Hypothesis for Compensation

    PubMed Central

    Martins, Ruben; Joanette, Yves; Monchi, Oury

    2015-01-01

    As the passage of time structurally alters one’s brain, cognition does not have to suffer the same faith, at least not to the same extent. Indeed, the existence of age-related compensatory mechanisms allow for some cognitive preservation. This paper attempts to coherently review the existing concepts of neurofunctional compensation when applied to two different cognitive domains, namely executive function and language processing. More precisely, we explore the Cognitive reserve (CR) model in healthy aging as well as its two underlying mechanisms: neural reserve and neural compensation. Furthermore, we review the Compensation-Related Utilization of Neural Circuits Hypothesis as well as the Growing Of Life Differences Explains Normal Aging model. Finally, we propose, based on some functional neuroimaging studies, the existence of another compensatory mechanism characterized by age-related delayed cerebral activation allowing for cognitive performance to be preserved at the expense of speed processing: the Temporal Hypothesis for Compensation. PMID:25964754

  19. 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

  20. Durability Improvements Through Degradation Mechanism Studies

    SciTech Connect

    Borup, Rodney L.; Mukundan, Rangachary; Spernjak, Dusan; Baker, Andrew M.; Lujan, Roger W.; Langlois, David Alan; Ahluwalia, Rajesh; Papadia, D. D.; Weber, Adam Z.; Kusoglu, Ahmet; Shi, Shouwnen; More, K. L.; Grot, Steve

    2015-08-03

    The durability of polymer electrolyte membrane (PEM) fuel cells is a major barrier to the commercialization of these systems for stationary and transportation power applications. By investigating cell component degradation modes and defining the fundamental degradation mechanisms of components and component interactions, new materials can be designed to improve durability. To achieve a deeper understanding of PEM fuel cell durability and component degradation mechanisms, we utilize a multi-institutional and multi-disciplinary team with significant experience investigating these phenomena.

  1. Mechanical strain and degradation of laser heterostructures

    NASA Astrophysics Data System (ADS)

    Ptashchenko, Alexander A.; Ptashchenko, Fedor A.; Maslejeva, Natalia V.; Sadova, Galina V.

    2001-02-01

    The effect of mechanical strain on degradation processes in GaAs-AlGaAs laser heterostructures (LHS) with stripe geometry and in light emitting diodes (LED) was experimentally studied. The strain was produced either by axial pressure or by indentation with a Wickers pyramid. We show that degradation affects the degree of polarization and the far-field distribution of laser emission. The effect of strain on the degradation intensity is estimated.

  2. Kinetic study and mechanism of Niclosamide degradation.

    PubMed

    Zaazaa, Hala E; Abdelrahman, Maha M; Ali, Nouruddin W; Magdy, Maimana A; Abdelkawy, M

    2014-11-11

    A spectrophotometric kinetic study of Niclosamide alkaline degradation as a function of drug concentration, alkaline concentration and temperature has been established utilizing double divisor-ratio spectra spectrophotometric method. The developed method allowed determination of Niclosamide in presence of its alkaline degradation products; namely; 2-chloro-4-nitro aniline (DEG I) and 5-chloro salicylic acid (DEG II) with characterization of its degradation mechanism. It was found that degradation kinetic of Niclosamide followed pseudo-first order under the established experimental conditions with a degradation rate constant (k) of 0.0829 mol/h and half life (t1/2) of 8.35 h. The overall degradation rate constant as a function of the temperature under the given conditions obeyed Arrhenius equation where the activation energy was calculated to be 3.41 kcal/mol. PMID:24892546

  3. Kinetic study and mechanism of Niclosamide degradation

    NASA Astrophysics Data System (ADS)

    Zaazaa, Hala E.; Abdelrahman, Maha M.; Ali, Nouruddin W.; Magdy, Maimana A.; Abdelkawy, M.

    2014-11-01

    A spectrophotometric kinetic study of Niclosamide alkaline degradation as a function of drug concentration, alkaline concentration and temperature has been established utilizing double divisor-ratio spectra spectrophotometric method. The developed method allowed determination of Niclosamide in presence of its alkaline degradation products; namely; 2-chloro-4-nitro aniline (DEG I) and 5-chloro salicylic acid (DEG II) with characterization of its degradation mechanism. It was found that degradation kinetic of Niclosamide followed pseudo-first order under the established experimental conditions with a degradation rate constant (k) of 0.0829 mol/h and half life (t1/2) of 8.35 h. The overall degradation rate constant as a function of the temperature under the given conditions obeyed Arrhenius equation where the activation energy was calculated to be 3.41 kcal/mol.

  4. From cell senescence to age-related diseases: differential mechanisms of action of senescence-associated secretory phenotypes

    PubMed Central

    Byun, Hae-Ok; Lee, Young-Kyoung; Kim, Jeong-Min; Yoon, Gyesoon

    2015-01-01

    Cellular senescence is a process by which cells enter a state of permanent cell cycle arrest. It is commonly believed to underlie organismal aging and age-associated diseases. However, the mechanism by which cellular senescence contributes to aging and age-associated pathologies remains unclear. Recent studies showed that senescent cells exert detrimental effects on the tissue microenvironment, generating pathological facilitators or aggravators. The most significant environmental effector resulting from senescent cells is the senescence-associated secretory phenotype (SASP), which is constituted by a strikingly increased expression and secretion of diverse pro-inflammatory cytokines. Careful investigation into the components of SASPs and their mechanism of action, may improve our understanding of the pathological backgrounds of age-associated diseases. In this review, we focus on the differential expression of SASP-related genes, in addition to SASP components, during the progress of senescence. We also provide a perspective on the possible action mechanisms of SASP components, and potential contributions of SASP-expressing senescent cells, to age-associated pathologies. [BMB Reports 2015; 48(10): 549-558] PMID:26129674

  5. Mechanisms of humic substances degradation by fungi

    NASA Astrophysics Data System (ADS)

    Chen, Y.; Hadar, Y.; Grinhut, T.

    2012-04-01

    Humic substances (HS) are formed by secondary synthesis reactions (humification) during the decay process and transformation of biomolecules originating from plants and other dead organisms. In nature, HS are extremely resistant to biological degradation. Thus, these substances are major components in the C cycle and in the biosphere and therefore, the understanding of the process leading to their formation and transformation and degradation is vital. Fungi active in the decomposition process of HS include mainly ascomycetes and basidiomycetes that are common in the upper layer of forest and grassland soils. Many basidiomycetes belong to the white-rot fungi (WRF) and litter-decomposing fungi (LDF). These fungi are considered to be the most efficient lignin degraders due to their nonspecific oxidizing enzymes: manganese peroxidase (MnP), lignin peroxidase (LiP) and laccase. Although bacteria dominate compost and participate in the turnover of HS, their ability to degrade stable macromolecules such as lignin and HS is limited. The overall objectives of this research were to corroborate biodegradation processes of HS by WRF. The specific objectives were: (i) To isolate, identify and characterize HS degrading WRF from biosolids (BS) compost; (ii) To study the biodegradation process of three types of HS, which differ in their structure, by WRF isolated from BS compost; and (iii) To investigate the mechanisms of HA degradation by WRF using two main approaches: (a) Study the physical and chemical analyses of the organic compounds obtained from direct fungal degradation of HA as well as elucidation of the relevant enzymatic reactions; and (b) Study the enzymatic and biochemical mechanisms involved during HA degradation. In order to study the capability of fungi to degrade HS, seventy fungal strains were isolated from biosolids (BS) compost. Two of the most active fungal species were identified based on rDNA sequences and designated Trametes sp. M23 and Phanerochaetesp., Y6

  6. 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.

  7. An age-related shift of resting-state functional connectivity of the subthalamic nucleus: a potential mechanism for compensating motor performance decline in older adults

    PubMed Central

    Mathys, Christian; Hoffstaedter, Felix; Caspers, Julian; Caspers, Svenja; Südmeyer, Martin; Grefkes, Christian; Eickhoff, Simon B.; Langner, Robert

    2014-01-01

    Healthy aging is associated with decline in basic motor functioning and higher motor control. Here, we investigated age-related differences in the brain-wide functional connectivity (FC) pattern of the subthalamic nucleus (STN), which plays an important role in motor response control. As earlier studies revealed functional coupling between STN and basal ganglia, which both are known to influence the conservativeness of motor responses on a superordinate level, we tested the hypothesis that STN FC with the striatum becomes dysbalanced with age. To this end, we performed a seed-based resting-state analysis of fMRI data from 361 healthy adults (mean age: 41.8, age range: 18–85) using bilateral STN as the seed region of interest. Age was included as a covariate to identify regions showing age-related changes of FC with the STN seed. The analysis revealed positive FC of the STN with several previously described subcortical and cortical regions like the anterior cingulate and sensorimotor cortex, as well as not-yet reported regions including central and posterior insula. With increasing age, we observed reduced positive FC with caudate nucleus, thalamus, and insula as well as increased positive FC with sensorimotor cortex and putamen. Furthermore, an age-related reduction of negative FC was found with precuneus and posterior cingulate cortex. We suggest that this reduced de-coupling of brain areas involved in self-relevant but motor-unrelated cognitive processing (i.e. precuneus and posterior cingulate cortex) from the STN motor network may represent a potential mechanism behind the age-dependent decline in motor performance. At the same time, older adults appear to compensate for this decline by releasing superordinate motor control areas, in particular caudate nucleus and insula, from STN interference while increasing STN-mediated response control over lower level motor areas like sensorimotor cortex and putamen. PMID:25100995

  8. Radiation Degradation Mechanisms in Laser Diodes

    NASA Technical Reports Server (NTRS)

    Johston, A. H.; Miyahira, T. F.

    2004-01-01

    Degradation mechanisms are investigated for laser diodes fabricated with different materials and wavelengths between 660 and 1550 nm. A new approach is developed that evaluates degradation below the laser threshold to determine the radiation-induced recombination density. This allows mechanisms at high injection, such as Auger recombination, to be separated from low-injection damage. New results show that AlGaInP lasers in the visible region are nearly an order of magnitude more resistant to radiation than devices fabricated with AlGaAs or AlGaAsP at longer wavelengths.

  9. 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. PMID:25917344

  10. Investigation of degradation mechanisms in composite matrices

    NASA Technical Reports Server (NTRS)

    Giori, C.; Yamauchi, T.

    1982-01-01

    Degradation mechanisms were investigated for graphite/polysulfone and graphite/epoxy laminates exposed to ultraviolet and high-energy electron radiations in vacuum up to 960 equivalent sun hours and 10 to the ninth power rads respectively. Based on GC and combined GC/MS analysis of volatile by-products evolved during irradiation, several free radical mechanisms of composite degradation were identified. The radiation resistance of different matrices was compared in terms of G values and quantum yields for gas formation. All the composite materials evaluated show high electron radiation stability and relatively low ultraviolet stability as indicated by low G values and high quantum for gas formation. Mechanical property measurements of irradiated samples did not reveal significant changes, with the possible exception of UV exposed polysulfone laminates. Hydrogen and methane were identified as the main by-products of irradiation, along with unexpectedly high levels of CO and CO2.

  11. Seepage into drifts with mechanical degradation.

    PubMed

    Li, Guomin; Tsang, Chin-Fu

    2003-01-01

    Seepage into drifts in unsaturated tuff is an important issue for the long-term performance of the proposed nuclear waste repository at Yucca Mountain, Nevada. Drifts in which waste packages will be emplaced are subject to degradation in the form of rockfall from the drift ceiling, induced by stress-relief, seismic, or thermal effects. The objective of this study is to calculate seepage rates, for various drift-degradation scenarios and for different values of percolation flux, in the Topopah Spring middle nonlithophysal (Tptpmn) and the Topopah Spring lower lithophysal (Tptpll) units at Yucca Mountain. Seepage calculations are conducted by (1) defining a heterogeneous drift-scale permeability model with field data, (2) selecting calibrated parameters associated with the Tptpmn and Tptpll units, and (3) simulating seepage, based on detailed degraded-drift profiles obtained from a separate rock mechanics engineering analysis. The simulation results indicate (1) that the seepage threshold (i.e., the percolation flux at which seepage first occurs) is not significantly changed by drift degradation and (2) the degradation-induced increase in seepage above the threshold is influenced probably more by the shape of the cavity created by rockfall than by rockfall volume. PMID:12714289

  12. Common Mechanisms of Alzheimer’s Disease and Ischemic Stroke: The Role of Protein Kinase C in the Progression of Age-Related Neurodegeneration

    PubMed Central

    Lucke-Wold, Brandon P.; Turner, Ryan C.; Logsdon, Aric F.; Simpkins, James W.; Alkon, Daniel L.; Smith, Kelly E.; Chen, Yi-Wen; Tan, Zhenjun; Huber, Jason D.; Rosen, Charles L.

    2015-01-01

    Ischemic stroke and Alzheimer’s disease (AD), despite being distinct disease entities, share numerous pathophysiological mechanisms such as those mediated by inflammation, immune exhaustion, and neurovascular unit compromise. An important shared mechanistic link is acute and chronic changes in protein kinase C (PKC) activity. PKC isoforms have widespread functions important for memory, blood-brain barrier maintenance, and injury repair that change as the body ages. Disease states accelerate PKC functional modifications. Mutated forms of PKC can contribute to neurodegeneration and cognitive decline. In some cases the PKC isoforms are still functional but are not successfully translocated to appropriate locations within the cell. The deficits in proper PKC translocation worsen stroke outcome and amyloid-β toxicity. Cross talk between the innate immune system and PKC pathways contribute to the vascular status within the aging brain. Unfortunately, comorbidities such as diabetes, obesity, and hypertension disrupt normal communication between the two systems. The focus of this review is to highlight what is known about PKC function, how isoforms of PKC change with age, and what additional alterations are consequences of stroke and AD. The goal is to highlight future therapeutic targets that can be applied to both the treatment and prevention of neurologic disease. Although the pathology of ischemic stroke and AD are different, the similarity in PKC responses warrants further investigation, especially as PKC-dependent events may serve as an important connection linking age-related brain injury. PMID:25114088

  13. Depression in Age-Related Macular Degeneration

    ERIC Educational Resources Information Center

    Casten, Robin; Rovner, Barry

    2008-01-01

    Age-related macular degeneration (AMD) is a major cause of disability in the elderly, substantially degrades the quality of their lives, and is a risk factor for depression. Rates of depression in AMD are substantially greater than those found in the general population of older people, and are on par with those of other chronic and disabling…

  14. Age-Related Macular Degeneration

    MedlinePlus

    ... this page please turn Javascript on. Age-related Macular Degeneration What is AMD? Click for more information Age-related macular degeneration, ... the macula allows you to see fine detail. AMD Blurs Central Vision AMD blurs the sharp central ...

  15. Macular degeneration - age-related

    MedlinePlus

    Age-related macular degeneration (ARMD); AMD ... distorted and wavy. There may be a small dark spot in the center of your vision that ... leafy vegetables, may also decrease your risk of age-related macular degeneration. If you have wet AMD, ...

  16. Mechanical degradation temperature of waste storage materials

    SciTech Connect

    Fink, M.C.; Meyer, M.L.

    1993-05-13

    Heat loading analysis of the Solid Waste Disposal Facility (SWDF) waste storage configurations show the containers may exceed 90{degrees}C without any radioactive decay heat contribution. Contamination containment is primarily controlled in TRU waste packaging by using multiple bag layers of polyvinyl chloride and polyethylene. Since literature values indicate that these thermoplastic materials can begin mechanical degradation at 66{degrees}C, there was concern that the containment layers could be breached by heating. To better define the mechanical degradation temperature limits for the materials, a series of heating tests were conducted over a fifteen and thirty minute time interval. Samples of a low-density polyethylene (LDPE) bag, a high-density polyethylene (HDPE) high efficiency particulate air filter (HEPA) container, PVC bag and sealing tape were heated in a convection oven to temperatures ranging from 90 to 185{degrees}C. The following temperature limits are recommended for each of the tested materials: (1) low-density polyethylene -- 110{degrees}C; (2) polyvinyl chloride -- 130{degrees}C; (3) high-density polyethylene -- 140{degrees}C; (4) sealing tape -- 140{degrees}C. Testing with LDPE and PVC at temperatures ranging from 110 to 130{degrees}C for 60 and 120 minutes also showed no observable differences between the samples exposed at 15 and 30 minute intervals. Although these observed temperature limits differ from the literature values, the trend of HDPE having a higher temperature than LDPE is consistent with the reference literature. Experimental observations indicate that the HDPE softens at elevated temperatures, but will retain its shape upon cooling. In SWDF storage practices, this might indicate some distortion of the waste container, but catastrophic failure of the liner due to elevated temperatures (<185{degrees}C) is not anticipated.

  17. Statistical physics of age related macular degeneration

    NASA Astrophysics Data System (ADS)

    Family, Fereydoon; Mazzitello, K. I.; Arizmendi, C. M.; Grossniklaus, H. E.

    Age-related macular degeneration (AMD) is the leading cause of blindness beyond the age of 50 years. The most common pathogenic mechanism that leads to AMD is choroidal neovascularization (CNV). CNV is produced by accumulation of residual material caused by aging of retinal pigment epithelium cells (RPE). The RPE is a phagocytic system that is essential for renewal of photoreceptors (rods and cones). With time, incompletely degraded membrane material builds up in the form of lipofuscin. Lipofuscin is made of free-radical-damaged protein and fat, which forms not only in AMD, but also Alzheimer disease and Parkinson disease. The study of lipofuscin formation and growth is important, because of their association with cellular aging. We introduce a model of non-equilibrium cluster growth and aggregation that we have developed for studying the formation and growth of lipofuscin in the aging RPE. Our results agree with a linear growth of the number of lipofuscin granules with age. We apply the dynamic scaling approach to our model and find excellent data collapse for the cluster size distribution. An unusual feature of our model is that while small particles are removed from the RPE the larger ones become fixed and grow by aggregation.

  18. Physics of Age Related Macular Degeneration

    NASA Astrophysics Data System (ADS)

    Family, Fereydoon

    2009-11-01

    Age-related macular degeneration (AMD) is the leading cause of blindness beyond the age of 50 years. The most common pathogenic mechanism that leads to AMD is choroidal neovascularization (CNV). CNV is produced by accumulation of residual material caused by aging of retinal pigment epithelium cells (RPE). The RPE is a phagocytic system that is essential for renewal of photoreceptors (rods and cones). With time, incompletely degraded membrane material builds up in the form of lipofuscin. Lipofuscin is made of free-radical-damaged protein and fat, which forms not only in AMD, but also Alzheimer's disease, and Parkinson's disease. The study of lipofuscin formation and growth is important, because of their association with cellular aging. In this talk I will discuss a model of non-equilibrium cluster growth that we have developed for studying the formation and growth of lipofuscin in AMD [K.I. Mazzitello, C.M. Arizmendi, Fereydoon Family, H. E. Grossniklaus, Physical Review E (2009)]. I will also present an overview of our theoretical and computational efforts in modeling some other aspects of the physics of AMD, including CNV and the breakdown of Bruch's membrane [Ongoing collaboration with Abbas Shirinifard and James A. Glazier, Biocomplexity Institute and Department of Physics, Indiana University, Y. Jiang, Los Alamos, and Hans E. Grossniklaus, Department of Ophthalmology, Emory University].

  19. Induction of epithelial to mesenchymal transition (EMT) and inhibition on adipogenesis: Two different sides of the same coin? Feasible roles and mechanisms of transforming growth factor β1 (TGF-β1) in age-related thymic involution.

    PubMed

    Tan, Jianxin; Wang, Yajun; Zhang, Nannan; Zhu, Xike

    2016-08-01

    Age-related thymic involution is characterized by a loss of thymic epithelial cells (TECs) and a concomitant increase in adipocytes, but the mechanisms involved in thymic adipogenesis are still not clear. Transforming growth factor β1 (TGF-β1) is a pleiotropic cytokine that has been reported to be up-regulated with age in thymic stromal cells in both human and mouse. However, the exact role of TGF-β1 in age-related thymic involution remains to be further elucidated. On the basis of previous findings, we propose a novel hypothesis that TGF-β1 functions a dual role in age-related thymic involution. On one hand, up-regulation of TGF-β1 promotes epithelial to mesenchymal transition (EMT) process in TECs via activating forkhead box protein C2 (FoxC2). On the other hand, TGF-β1 inhibits the transdifferentiation of EMT-derived mesenchymal cells to adipocytes in the thymus. If confirmed, our hypothesis will not only provide further evidence supporting that the transdifferentiation of TECs into pre-adipocytes represents a source of thymic adiposity during age-related thymic involution, but also uncover a unique role of TGF-β1 in the transdifferentiation of TECs into pre-adipocytes. Collectively, the inhibition of TGF-β1 may serve as a strategy to hinder age-related thymic involution or even to restore thymic function in the elderly. PMID:27189906

  20. [Age-related macular degeneration].

    PubMed

    Budzinskaia, M V

    2014-01-01

    The review provides an update on the pathogenesis and new treatment modalities for neovascular age-related macular degeneration (AMD). The impact of polymorphism in particular genes, including complement factor H (CFH), age-related maculopathy susceptibility 2 (ARMS2/LOC387715), and serine peptidase (HTRA1), on AMD development is discussed. Clinical presentations of different forms of exudative AMD, that is classic, occult, or more often mixed choroidal neovascularization, retinal angiomatous proliferation, and choroidal polypoidal vasculopathy, are described. Particular attention is paid to the results of recent clinical trials and safety issues around the therapy. PMID:25715554

  1. Aging-Related Changes in the Nigrostriatal Dopamine System and the Response to MPTP in Nonhuman Primates: Diminished Compensatory Mechanisms as a Prelude to Parkinsonism

    PubMed Central

    Collier, Timothy J.; Lipton, Jack; Daley, Brian F.; Palfi, Stephane; Chu, Yaping; Sortwell, Caryl; Bakay, Roy A.E.; Sladek, John R.; Kordower, Jeffrey H.

    2007-01-01

    Aging is the most prominent risk factor for Parkinson’s disease. Yet, consensus of how advancing age may predispose the dopamine (DA) system to parkinsonism is lacking. Three age-ranges of female rhesus monkeys, 8–9, 15–17 and 21–31 years, received unilateral DA depletion with intracarotid 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). Morphological and biochemical analyses of DA-depleted and intact hemispheres revealed three primary findings: 1) The intact striatum exhibited age-related declines in dopamine (DA) and homovanillic acid (HVA) that were present by middle-age; 2) In the MPTP-treated striatum, the compensatory increase in DA activity was absent in old monkeys; and, 3) Age-associated morphological changes included declines in the density of tyrosine hydroxylase (TH) positive fibers in striatum, decreased nigral soma size and optical density of TH, but no significant loss of neurons. These findings suggest that aging produces changes in the nigrostriatal DA system that approach the threshold for expression of parkinsonian features, and that progressive impairment of plasticity may be central to the role of aging in development of parkinsonism. PMID:17254792

  2. Age-related hearing loss

    MedlinePlus

    ... is no known single cause of age-related hearing loss. Most commonly, it is caused by changes in the inner ear that occur as you grow older. Your genes and loud noise (from rock concerts or music headphones) may play a large role. The following ...

  3. 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.

  4. Mechanical Properties of Degraded PMR-15 Resin

    NASA Technical Reports Server (NTRS)

    Tsuji, Luis C.; McManus, Hugh L.; Bowles, Kenneth J.

    1998-01-01

    Thermo-oxidative aging produces a non-uniform degradation state in PMR-15 resin. A surface layer, usually attributed to oxidative degradation, forms. This surface layer has different properties from the inner material. A set of material tests was designed to separate the properties of the oxidized surface layer from the properties of interior material. Test specimens were aged at 316 C in either air or nitrogen, for durations of up to 800 hours. The thickness of the oxidized surface layer in air aged specimens, and the shrinkage and Coefficient of Thermal Expansion (CTE) of nitrogen aged specimens were measured directly. Four-point-bend tests were performed to determine modulus of both the oxidized surface layer and the interior material. Bimaterial strip specimens consisting of oxidized surface material and unoxidized interior material were constructed and used to determine surface layer shrinkage and CTE. Results confirm that the surface layer and core materials have substantially different properties.

  5. Stabilization and Degradation Mechanisms of Cytoplasmic Ataxin-1

    PubMed Central

    Kohiyama, Mayumi F.; Lagalwar, Sarita

    2015-01-01

    Aggregation-prone proteins in neurodegenerative disease disrupt cellular protein stabilization and degradation pathways. The neurodegenerative disease spinocerebellar ataxia type 1 (SCA1) is caused by a coding polyglutamine expansion in the Ataxin-1 gene (ATXN1), which gives rise to the aggregation-prone mutant form of ATXN1 protein. Cerebellar Purkinje neurons, preferentially vulnerable in SCA1, produce ATXN1 protein in both cytoplasmic and nuclear compartments. Cytoplasmic stabilization of ATXN1 by phosphorylation and 14-3-3-mediated mechanisms ultimately drive translocation of the protein to the nucleus where aggregation may occur. However, experimental inhibition of phosphorylation and 14-3-3 binding results in rapid degradation of ATXN1, thus preventing nuclear translocation and cellular toxicity. The exact mechanism of cytoplasmic ATXN1 degradation is currently unknown; further investigation of degradation may provide future therapeutic targets. This review examines the present understanding of cytoplasmic ATXN1 stabilization and potential degradation mechanisms during normal and pathogenic states. PMID:27168726

  6. [Presbycusis - Age Related Hearing Loss].

    PubMed

    Fischer, N; Weber, B; Riechelmann, H

    2016-07-01

    Presbycusis or age related hearing loss can be defined as a progressive, bilateral and symmetrical sensorineural hearing loss due to age related degeneration of inner ear structures. It can be considered a multifactorial complex disorder with environmental and genetic factors. The molecular, electrophysiological and histological damage at different levels of the inner ear cause a progressive hearing loss, which usually affects the high frequencies of hearing. The resulting poor speech recognition has a negative impact on cognitive, emotional and social function in older adults. Recent investigations revealed an association between hearing impairment and social isolation, anxiety, depression and cognitive decline in elderly. These findings emphasize the importance of diagnosis and treating hearing loss in the elderly population. Hearing aids are the most commonly used devices for treating presbycusis. The technical progress of implantable hearing devices allows an effective hearing rehabilitation even in elderly with severe hearing loss. However, most people with hearing impairments are not treated adequately. PMID:27392191

  7. Characterization of Thermally Degraded Energetic Materials: Mechanical and Chemical Behavior

    SciTech Connect

    Miller, J.C.; Renlund, A.M.; Schmitt, R.G.; Wellman, G.W.

    1998-12-04

    We report the results of recent experiments on thermally degraded HMX and HMX/binder materials. Small-scale samples were heated confined in either constant-volume or load- controlled configurations. A main emphasis of the work reported here is developing an understanding of the complex coupling of the mechanical and chemical responses during thermal degradation.

  8. Mechanical Properties of Degraded PMR-15 Resin

    NASA Technical Reports Server (NTRS)

    Tsuji, Luis C.

    2000-01-01

    Thermo-oxidative aging produces a nonuniform degradation state in PMR-15 resin. A surface layer, usually attributed to oxidative degradation, forms. This surface layer has different properties from the inner material. A set of material tests was designed to separate the properties of the oxidized surface layer from the properties of interior material. Test specimens were aged at 316 C in either air or nitrogen, for durations of up to 800 hr. The thickness of the oxidized surface layer in air aged specimens, and the shrinkage and coefficient of thermal expansion (CTE) of nitrogen aged specimens were measured directly. The nitrogen-aged specimens were assumed to have the same properties as the interior material in the air-aged specimens. Four-point-bend tests were performed to determine modulus of both the oxidized surface layer and the interior material. Bimaterial strip specimens consisting of oxidized surface material and unoxidized interior material were constructed and used to determine surface layer shrinkage and CTE. Results confirm that the surface layer and core materials have substantially different properties.

  9. Degradation mechanisms of ceramic thermal barrier coatings in corrosive environments

    NASA Technical Reports Server (NTRS)

    Lau, S. K.; Bratton, R. J.

    1984-01-01

    Chemical as well as thermal-mechanical interactions between the ceramics and gas turbine combustion gases/condensates are found to play critical roles in the degradation of porous plasma-sprayed ceramic thermal barrier coatings. The detailed degradation mechanisms of several state-of-the-art ceramic thermal barrier coatings, including several zirconia compositions and a calcium silicate, in corrosive environments are examined in this paper. Approaches to extend coating lifetime are also described.

  10. [Age-related macular degeneration].

    PubMed

    Garcia Layana, A

    1998-01-01

    Age-related macular degeneration (ARMD) is the leading cause of blindness in the occidental world. Patients suffering this process have an important reduction on their quality of life being handicapped to read, to write, to recognise faces of their friends, or even to watch the television. One of the main problems of that disease is the absence of an effective treatment able to revert the process. Laser treatment is only useful in a limited number of patients, and even in these cases recurrent lesions are frequent. These facts and the progressive ageing of our society establish the ARMD as one of the biggest aim of medical investigations for the next century, and currently is focus of attention in the most industrialised countries. One of the most promising pieces of research is focused in the investigation of the risk factors associated with the age-related macular degeneration, in order to achieve a prophylactic treatment avoiding its appearance. Diet elements such as fat ingestion or reduced antioxidant intakes are being investigated as some of these factors, what open a new possibility for a prophylactic treatment. Finally, research is looking for new therapeutic modalities such as selective radiotherapy in order to improve or maintain the vision of these patients. PMID:10420956

  11. Peroxisome degradation in mammals: mechanisms of action, recent advances, and perspectives

    PubMed Central

    Nordgren, Marcus; Wang, Bo; Apanasets, Oksana; Fransen, Marc

    2013-01-01

    Peroxisomes are remarkably dynamic organelles that participate in a diverse array of cellular processes, including the metabolism of lipids and reactive oxygen species. In order to regulate peroxisome function in response to changing nutritional and environmental stimuli, new organelles need to be formed and superfluous and dysfunctional organelles have to be selectively removed. Disturbances in any of these processes have been associated with the etiology and progression of various congenital neurodegenerative and age-related human disorders. The aim of this review is to critically explore our current knowledge of how peroxisomes are degraded in mammalian cells and how defects in this process may contribute to human disease. Some of the key issues highlighted include the current concepts of peroxisome removal, the peroxisome quality control mechanisms, the initial triggers for peroxisome degradation, the factors for dysfunctional peroxisome recognition, and the regulation of peroxisome homeostasis. We also dissect the functional and mechanistic relationship between different forms of selective organelle degradation and consider how lysosomal dysfunction may lead to defects in peroxisome turnover. In addition, we draw lessons from studies on other organisms and extrapolate this knowledge to mammals. Finally, we discuss the potential pathological implications of dysfunctional peroxisome degradation for human health. PMID:23785334

  12. Mechanisms balancing skeletal matrix synthesis and degradation.

    PubMed Central

    Blair, Harry C; Zaidi, Mone; Schlesinger, Paul H

    2002-01-01

    Bone is regulated by evolutionarily conserved signals that balance continuous differentiation of bone matrix-producing cells against apoptosis and matrix removal. This is continued from embryogenesis, where the skeleton differentiates as a solid mass and is shaped into separate bones by cell death and proteolysis. The two major tissues of the skeleton are avascular cartilage, with an extracellular matrix based on type II collagen and hydrophilic proteoglycans, and bone, a stronger and lighter material based on oriented type I collagen and hydroxyapatite. Both differentiate from the same mesenchymal stem cells. This differentiation is regulated by a family of related signals centred on bone morphogenic proteins. Fibroblast growth factors, Indian hedgehog and parathyroid hormone-related protein are important in determining the type of matrix and the relation of skeletal and non-skeletal structures. Removal of mineralized matrix involves apoptosis of matrix cells and differentiation of acid-secreting cells (osteoclasts) from macrophage precursors. Key regulators of matrix removal are signals in the tumour-necrosis-factor family. Osteoclasts dissolve bone by isolating a region of the matrix and secreting HCl and proteinases at that site. Successive cycles of removal and replacement allow growth, repair and remodelling. The signals for bone turnover are predominantly cell-membrane-associated, allowing very specific spatial regulation. In addition to its support function, bone is a reservoir of Ca2+, PO3-(4) and OH-. Secondary modulation of mineral secretion and bone degradation are mediated by humoral signals, including parathyroid hormone and vitamin D, as well as the cytokines that also regulate the underlying cell differentiation. PMID:12023876

  13. Drug Release Kinetics and Transport Mechanisms of Non-degradable and Degradable Polymeric Delivery Systems

    PubMed Central

    Fu, Yao; Kao, Weiyuan John

    2010-01-01

    Importance of the field The advancement in material design and engineering has led to the rapid development of novel materials with increasing complexity and functions. Both non-degradable and degradable polymers have found wide applications in the controlled delivery field. Studies on drug release kinetics provide important information into the function of material systems. To elucidate the detailed transport mechanism and the structure-function relationship of a material system, it is critical to bridge the gap between the macroscopic data and the transport behavior at the molecular level. Areas covered in this review The structure and function information of selected non-degradable and degradable polymers have been collected and summarized from literatures published after 1990s. The release kinetics of selected drug compounds from various material systems will be discussed in case studies. Recent progresses in the mathematical models based on different transport mechanisms will be highlighted. What the reader will gain This article aims to provide an overview of structure-function relationships of selected non-degradable and degradable polymers as drug delivery matrices. Take home message Understanding the structure-function relationship of the material system is key to the successful design of a delivery system for a particular application. Moreover, developing complex polymeric matrices requires more robust mathematical models to elucidate the solute transport mechanisms. PMID:20331353

  14. Medical bioremediation of age-related diseases

    PubMed Central

    Mathieu, Jacques M; Schloendorn, John; Rittmann, Bruce E; Alvarez, Pedro JJ

    2009-01-01

    Catabolic insufficiency in humans leads to the gradual accumulation of a number of pathogenic compounds associated with age-related diseases, including atherosclerosis, Alzheimer's disease, and macular degeneration. Removal of these compounds is a widely researched therapeutic option, but the use of antibodies and endogenous human enzymes has failed to produce effective treatments, and may pose risks to cellular homeostasis. Another alternative is "medical bioremediation," the use of microbial enzymes to augment missing catabolic functions. The microbial genetic diversity in most natural environments provides a resource that can be mined for enzymes capable of degrading just about any energy-rich organic compound. This review discusses targets for biodegradation, the identification of candidate microbial enzymes, and enzyme-delivery methods. PMID:19358742

  15. Preparation and degradation mechanisms of biodegradable polymer: a review

    NASA Astrophysics Data System (ADS)

    Zeng, S. H.; Duan, P. P.; Shen, M. X.; Xue, Y. J.; Wang, Z. Y.

    2016-07-01

    Polymers are difficult to degrade completely in Nature, and their catabolites may pollute the environment. In recent years, biodegradable polymers have become the hot topic in people's daily life with increasing interest, and a controllable polymer biodegradation is one of the most important directions for future polymer science. This article presents the main preparation methods for biodegradable polymers and discusses their degradation mechanisms, the biodegradable factors, recent researches and their applications. The future researches of biodegradable polymers are also put forward.

  16. Formation of free radicals during mechanical degradation of elastomers.

    NASA Technical Reports Server (NTRS)

    Devries, K. L.; Williams, M. L.; Roylance, D. K.

    1971-01-01

    Solithane 113 (an amorphous polyurethane elastomer) was prepared by curing equal proportions of castor oil and trifunctional isocyanate for 6 hr 45 min at 170 F. The sample material was mechanically degraded by grinding below and above its glass transition point at liquid nitrogen and room temperatures. The EPR spectra of ground samples were recorded and the number of free radicals were determined by a computer double-integration of the recorded spectra and by a comparison of the values with those of a standard material. Curves of EPR spectra suggest that different molecular mechanisms may be active in degradation of this material below and above its glass transition temperature.

  17. Mechanisms of Glucagon Degradation at Alkaline pH

    PubMed Central

    Caputo, Nicholas; Castle, Jessica R.; Bergstrom, Colin P.; Carroll, Julie M.; Bakhtiani, Parkash A.; Jackson, Melanie A.; Roberts, Charles T.; David, Larry L.; Ward, W. Kenneth

    2014-01-01

    Glucagon is unstable and undergoes degradation and aggregation in aqueous solution. For this reason, its use in portable pumps for closed loop management of diabetes is limited to very short periods. In this study, we sought to identify the degradation mechanisms and the bioactivity of specific degradation products. We studied degradation in the alkaline range, a range at which aggregation is minimized. Native glucagon and analogs identical to glucagon degradation products were synthesized. To quantify biological activity in glucagon and in the degradation peptides, a protein kinase A-based bioassay was used. Aged, fresh, and modified peptides were analyzed by liquid chromatography with mass spectrometry (LCMS). Oxidation of glucagon at the Met residue was common but did not reduce bioactivity. Deamidation and isomerization were also common and were more prevalent at pH 10 than 9. The biological effects of deamidation and isomerization were unpredictable; deamidation at some sites did not reduce bioactivity. Deamidation of Gln 3, isomerization of Asp 9, and deamidation with isomerization at Asn 28 all caused marked potency loss. Studies with molecular-weight-cutoff membranes and LCMS revealed much greater fibrillation at pH 9 than 10. Further work is necessary to determine formulations of glucagon that minimize degradation and fibrillation. PMID:23651991

  18. Age-Related Tissue Stiffening: Cause and Effect

    PubMed Central

    Sherratt, Michael J.

    2013-01-01

    Significance Tissue elasticity is severely compromised in aging skin, lungs, and blood vessels. In the vascular and pulmonary systems, respectively, loss of mechanical function is linked to hypertension, which in turn is a risk factor for heart and renal failure, stroke, and aortic aneurysms, and to an increased risk of mortality as a result of acute lung infections. Recent Advances Although cellular mechanisms were thought to play an important role in mediating tissue aging, the reason for the apparent sensitivity of elastic fibers to age-related degradation remained unclear. We have recently demonstrated that compared with type I collagen, a key component of the elastic fiber system, the cysteine-rich fibrillin microfibril is highly susceptible to direct UV exposure in a cell-free environment. We hypothesized therefore that, as a consequence of both their remarkable longevity and cysteine-rich composition, many elastic fiber-associated components will be susceptible to the accumulation of damage by both direct UV radiation and reactive oxygen species-mediated oxidation. Critical Issues Although elastic fiber remodeling is a common feature of aging dynamic tissues, the inaccessibility of most human tissues has hampered attempts to define the molecular causes. Clinical Care Relevance Although, currently, the localized repair of damaged elastic fibers may be effected by the topical application of retinoids and some cosmetic products, future studies may extend the application of systemic transforming growth factor β antagonists, which can prevent cardiovascular remodeling in murine Marfan syndrome, to aging humans. Acellular mechanisms may be key mediators of elastic fiber remodeling and hence age-related tissue stiffening. PMID:24527318

  19. Mechanism-based Modeling of Long-term Degradation

    NASA Technical Reports Server (NTRS)

    McManus, H. L.; Foch, B. J.; Cunningham, R. A.

    1998-01-01

    The use of composites in high temperature, long lifetime applications requires a basic understanding of composite degradation mechanisms, advances in analytical capabilities, and accurate accelerated and scaled tests. To advance all of these goals, models are proposed based on a variety of fundamental material mechanisms. Thermal, oxygen, and moisture diffusion, chemical reactions, composite micromechanics; modified laminated plate theory, and future mechanics based damage models are used. All models attempt to stay as simple and fundamental as possible. All are coupled, so that interactions between various effects are modeled implicitly. Ongoing efforts at MIT are reviewed here, with some reference to other work, but no attempt is made to do a comprehensive review. Mechanism based models are yielding understanding of the mechanisms behind observed degradation phenomena, are helping to design accelerated tests, and are the first steps towards a predictive capability.

  20. Physical and mechanical properties of degraded waste surrogate material

    SciTech Connect

    Hansen, F.D.; Mellegard, K.D.

    1998-03-01

    This paper discusses rock mechanics testing of surrogate materials to provide failure criteria for compacted, degraded nuclear waste. This daunting proposition was approached by first assembling all known parameters such as the initial waste inventory and rock mechanics response of the underground setting after the waste is stored. Conservative assumptions allowing for extensive degradation processes helped quantify the lowest possible strength conditions of the future state of the waste. In the larger conceptual setting, computations involve degraded waste behavior in transient pressure gradients as gas exits the waste horizon into a wellbore. Therefore, a defensible evaluation of tensile strength is paramount for successful analyses and intentionally provided maximal failed volumes. The very conservative approach assumes rampant degradation to define waste surrogate composition. Specimens prepared from derivative degradation product were consolidated into simple geometries for rock mechanics testing. Tensile strength thus derived helped convince a skeptical peer review panel that drilling into the Waste Isolation Pilot Plant (WIPP) would not likely expel appreciable solids via the drill string.

  1. Degradation Mechanisms and Accelerated Testing in PEM Fuel Cells

    SciTech Connect

    Borup, Rodney L.

    2011-01-01

    The durability of PEM fuel cells is a major barrier to the commercialization of these systems for stationary and transportation power applications. Although there has been recent progress in improving durability, further improvements are needed to meet the commercialization targets. Past improvements have largely been made possible because of the fundamental understanding of the underlying degradation mechanisms. By investigating component and cell degradation modes; defining the fundamental degradation mechanisms of components and component interactions new materials can be designed to improve durability. Various factors have been shown to affect the useful life of PEM fuel cells. Other issues arise from component optimization. Operational conditions (such as impurities in either the fuel or oxidant stream), cell environment, temperature (including subfreezing exposure), pressure, current, voltage, etc.; or transient versus continuous operation, including start-up and shutdown procedures, represent other factors that can affect cell performance and durability.

  2. The relevance of aging-related changes in brain function to rehabilitation in aging-related disease

    PubMed Central

    Crosson, Bruce; McGregor, Keith M.; Nocera, Joe R.; Drucker, Jonathan H.; Tran, Stella M.; Butler, Andrew J.

    2015-01-01

    The effects of aging on rehabilitation of aging-related diseases are rarely a design consideration in rehabilitation research. In this brief review we present strong coincidental evidence from these two fields suggesting that deficits in aging-related disease or injury are compounded by the interaction between aging-related brain changes and disease-related brain changes. Specifically, we hypothesize that some aphasia, motor, and neglect treatments using repetitive transcranial magnetic stimulation (rTMS) or transcranial direct current stimulation (tDCS) in stroke patients may address the aging side of this interaction. The importance of testing this hypothesis and addressing the larger aging by aging-related disease interaction is discussed. Underlying mechanisms in aging that most likely are relevant to rehabilitation of aging-related diseases also are covered. PMID:26074807

  3. Silk Fibroin Degradation Related to Rheological and Mechanical Properties.

    PubMed

    Partlow, Benjamin P; Tabatabai, A Pasha; Leisk, Gary G; Cebe, Peggy; Blair, Daniel L; Kaplan, David L

    2016-05-01

    Regenerated silk fibroin has been proposed as a material substrate for biomedical, optical, and electronic applications. Preparation of the silk fibroin solution requires extraction (degumming) to remove contaminants, but results in the degradation of the fibroin protein. Here, a mechanism of fibroin degradation is proposed and the molecular weight and polydispersity is characterized as a function of extraction time. Rheological analysis reveals significant changes in the viscosity of samples while mechanical characterization of cast and drawn films shows increased moduli, extensibility, and strength upon drawing. Fifteen minutes extraction time results in degraded fibroin that generates the strongest films. Structural analysis by wide angle X-ray scattering (WAXS) and Fourier transform infrared spectroscopy (FTIR) indicates molecular alignment in the drawn films and shows that the drawing process converts amorphous films into the crystalline, β-sheet, secondary structure. Most interesting, by using selected extraction times, films with near-native crystallinity, alignment, and molecular weight can be achieved; yet maximal mechanical properties for the films from regenerated silk fibroin solutions are found with solutions subjected to some degree of degradation. These results suggest that the regenerated solutions and the film casting and drawing processes introduce more complexity than native spinning processes. PMID:26756449

  4. Age-related hair pigment loss.

    PubMed

    Tobin, Desmond J

    2015-01-01

    Humans are social animals that communicate disproportionately via potent genetic signals imbued in the skin and hair, including racial, ethnic, health, gender, and age status. For the vast majority of us, age-related hair pigment loss becomes the inescapable signal of our disappearing youth. The hair follicle (HF) pigmentary unit is a wonderful tissue for studying mechanisms generally regulating aging, often before this becomes evident elsewhere in the body. Given that follicular melanocytes (unlike those in the epidermis) are regulated by the hair growth cycle, this cycle is likely to impact the process of aging in the HF pigmentary unit. The formal identification of melanocyte stem cells in the mouse skin has spurred a flurry of reports on the potential involvement of melanocyte stem cell depletion in hair graying (i.e., canities). Caution is recommended, however, against simple extrapolation of murine data to humans. Regardless, hair graying in both species is likely to involve an age-related imbalance in the tissue's oxidative stress handling that will impact not only melanogenesis but also melanocyte stem cell and melanocyte homeostasis and survival. There is some emerging evidence that the HF pigmentary unit may have regenerative potential, even after it has begun to produce white hair fibers. It may therefore be feasible to develop strategies to modulate some aging-associated changes to maintain melanin production for longer. PMID:26370651

  5. Mechanical properties and in vitro degradation of bioresorbable knitted stents.

    PubMed

    Nuutinen, Juha-Pekka; Välimaa, Tero; Clerc, Claude; Törmälä, Pertti

    2002-01-01

    The aim of this study was to characterize the mechanical properties and in vitro degradation of bioresorbable knitted stents. Each stent was knitted using a single self-reinforced fibre made out of either PLLA or 96L/4D PLA or 80L/20G PLGA. The mechanical and physical properties of the fibres and stents were measured before and after gamma sterilization, as well as during in vitro degradation. The mechanical properties of the knitted stents made out of bioresorbable fibres were similar to those of commercially available metallic stents. The knitting geometry (loop height) had a marked effect on the mechanical properties of the stents. The rate of in vitro degradation in mechanical and physical properties for the PLLA and 96L/4D PLA stents was similar and significantly lower than that of the 80L/20G PLGA stents. The 80L/20G PLGA stents lost about 35% of their initial weight at 11 weeks. At this time, they had lost all their compression resistance strength. These data can be used as a guideline in planning further studies in vivo. PMID:12555898

  6. Environment assisted degradation mechanisms in aluminum-lithium alloys

    NASA Technical Reports Server (NTRS)

    Gangloff, Richard P.; Stoner, Glenn E.; Swanson, Robert E.

    1988-01-01

    Section 1 of this report records the progress achieved on NASA-LaRC Grant NAG-1-745 (Environment Assisted Degradation Mechanisms in Al-Li Alloys), and is based on research conducted during the period April 1 to November 30, 1987. A discussion of work proposed for the project's second year is included. Section 2 provides an overview of the need for research on the mechanisms of environmental-mechanical degradation of advanced aerospace alloys based on aluminum and lithium. This research is to provide NASA with the basis necessary to permit metallurgical optimization of alloy performance and engineering design with respect to damage tolerance, long term durability and reliability. Section 3 reports on damage localization mechanisms in aqueous chloride corrosion fatigue of aluminum-lithium alloys. Section 4 reports on progress made on measurements and mechanisms of localized aqueous corrosion in aluminum-lithium alloys. Section 5 provides a detailed technical proposal for research on environmental degradation of Al-Li alloys, and the effect of hydrogen in this.

  7. Photooxidation of cellulose nitrate: new insights into degradation mechanisms.

    PubMed

    Berthumeyrie, Sebastien; Collin, Steeve; Bussiere, Pierre-Olivier; Therias, Sandrine

    2014-05-15

    Cellulose nitrate (or nitrocellulose) has received considerable interest due to its uses in various applications, such as paints, photographic films and propellants. However, it is considered as one of the primary pollutants in the energetic material industries because it can be degraded to form polluting chemical species. In this work, the UV light degradation of cellulose nitrate films was studied under conditions of artificially accelerated photooxidation. To eliminate the reactivity of nitro groups, the degradation of ethylcellulose was also investigated. Infrared spectroscopy analyses of the chemical modifications caused by the photooxidation of cellulose nitrate films and the resulting formation of volatile products revealed the occurrence of de-nitration and the formation of oxidation photoproducts exhibiting lactone and anhydride functions. The impact of these chemical modifications on the mechanical and thermal properties of cellulose nitrate films includes embrittlement and lower temperatures of ignition when used as a propellant. PMID:24685530

  8. Mechanisms of polymer degradation using an oxygen plasma generator

    NASA Technical Reports Server (NTRS)

    Colony, Joe A.; Sanford, Edward L.

    1987-01-01

    An RF oxygen plasma generator was used to produce polymer degradation which appears to be similar to that which has been observed in low Earth orbit. Mechanisms of this type of degradation were studied by collecting the reaction products in a cryogenic trap and identifying the molecular species using infrared, mass spectral, and X-ray diffraction techniques. No structurally dependent species were found from Kapton, Teflon, or Saran polymers. However, very reactive free radical entities are produced during the polymer degradation, as well as carbon dioxide and water. Reactions of the free radicals with the glass reaction vessel, with copper metal in the cold trap, and with a triphenyl phosphate scavenger in the cold trap, demonstrated the reactivity of the primary products.

  9. Degradation mechanism of planar perovskite solar cells (Presentation Recording)

    NASA Astrophysics Data System (ADS)

    Qin, Chuanjiang; Matsushima, Toshinori; Adachi, Chihaya

    2015-10-01

    Organic-inorganic hybrid halide perovskites are an interesting class of materials that have excellent semiconductor properties, and demonstrated promising applications on many fields, such as solar cells, water photolysis, light emitting diodes, and amplified spontaneous emission. So far, the device lifetime is still short, and this is an important key issue faced for all researchers in this field.[1] The deep understanding of their durability and degradation mechanism is critical and necessary toward future applications. Towards development of efficient and long-term stable perovskite solar cells (PSCs), we firstly studied the relationship between crystallization, morphology, device architecture, efficiency and durability of encapsulated PSCs. Furthermore, the degradation mechanism of the devices was elucidated by different experimental methods. The well crystallized and fully covered perovskite layer improves not only power conversion efficiency but also long-time durability. Compared to a widely used silver counter electrode, lithium fluoride/aluminum and gold electrode-based PSCs demonstrated better durability owing to less chemical degradation and interface changing. We also confirmed that the amount of accumulated charge carriers induces the degradation of the PSCs, which was proved by a thermally stimulated current technique. Finally, we realized a planar PSC with excellent durability by improving device encapsulation and optimizing device structures. Reference: 1. M. Grätzel, Nature Materials 2014, 13, 838-842.

  10. Inflammation and its role in age-related macular degeneration.

    PubMed

    Kauppinen, Anu; Paterno, Jussi J; Blasiak, Janusz; Salminen, Antero; Kaarniranta, Kai

    2016-05-01

    Inflammation is a cellular response to factors that challenge the homeostasis of cells and tissues. Cell-associated and soluble pattern-recognition receptors, e.g. Toll-like receptors, inflammasome receptors, and complement components initiate complex cellular cascades by recognizing or sensing different pathogen and damage-associated molecular patterns, respectively. Cytokines and chemokines represent alarm messages for leukocytes and once activated, these cells travel long distances to targeted inflamed tissues. Although it is a crucial survival mechanism, prolonged inflammation is detrimental and participates in numerous chronic age-related diseases. This article will review the onset of inflammation and link its functions to the pathogenesis of age-related macular degeneration (AMD), which is the leading cause of severe vision loss in aged individuals in the developed countries. In this progressive disease, degeneration of the retinal pigment epithelium (RPE) results in the death of photoreceptors, leading to a loss of central vision. The RPE is prone to oxidative stress, a factor that together with deteriorating functionality, e.g. decreased intracellular recycling and degradation due to attenuated heterophagy/autophagy, induces inflammation. In the early phases, accumulation of intracellular lipofuscin in the RPE and extracellular drusen between RPE cells and Bruch's membrane can be clinically detected. Subsequently, in dry (atrophic) AMD there is geographic atrophy with discrete areas of RPE loss whereas in the wet (exudative) form there is neovascularization penetrating from the choroid to retinal layers. Elevations in levels of local and systemic biomarkers indicate that chronic inflammation is involved in the pathogenesis of both disease forms. PMID:26852158

  11. High Temperature Degradation Mechanisms in Polymer Matrix Composites

    NASA Technical Reports Server (NTRS)

    Cunningham, Ronan A.

    1996-01-01

    Polymer matrix composites are increasingly used in demanding structural applications in which they may be exposed to harsh environments. The durability of such materials is a major concern, potentially limiting both the integrity of the structures and their useful lifetimes. The goal of the current investigation is to develop a mechanism-based model of the chemical degradation which occurs, such that given the external chemical environment and temperatures throughout the laminate, laminate geometry, and ply and/or constituent material properties, we can calculate the concentration of diffusing substances and extent of chemical degradation as functions of time and position throughout the laminate. This objective is met through the development and use of analytical models, coupled to an analysis-driven experimental program which offers both quantitative and qualitative information on the degradation mechanism. Preliminary analyses using a coupled diffusion/reaction model are used to gain insight into the physics of the degradation mechanisms and to identify crucial material parameters. An experimental program is defined based on the results of the preliminary analysis which allows the determination of the necessary material coefficients. Thermogravimetric analyses are carried out in nitrogen, air, and oxygen to provide quantitative information on thermal and oxidative reactions. Powdered samples are used to eliminate diffusion effects. Tests in both inert and oxidative environments allow the separation of thermal and oxidative contributions to specimen mass loss. The concentration dependency of the oxidative reactions is determined from the tests in pure oxygen. Short term isothermal tests at different temperatures are carried out on neat resin and unidirectional macroscopic specimens to identify diffusion effects. Mass loss, specimen shrinkage, the formation of degraded surface layers and surface cracking are recorded as functions of exposure time. Geometry effects

  12. Degradation mechanisms and accelerated testing in PEM fuel cells

    SciTech Connect

    Borup, Rodney L; Mukundan, Rangachary

    2010-01-01

    The durability of PEM fuel cells is a major barrier to the commercialization of these systems for stationary and transportation power applications. Although there has been recent progress in improving durability, further improvements are needed to meet the commercialization targets. Past improvements have largely been made possible because of the fundamental understanding of the underlying degradation mechanisms. By investigating component and cell degradation modes; defining the fundamental degradation mechanisms of components and component interactions new materials can be designed to improve durability. Various factors have been shown to affect the useful life of PEM fuel cells. Other issues arise from component optimization. Operational conditions (such as impurities in either the fuel and oxidant stream), cell environment, temperature (including subfreezing exposure), pressure, current, voltage, etc.; or transient versus continuous operation, including start-up and shutdown procedures, represent other factors that can affect cell performance and durability. The need for Accelerated Stress Tests (ASTs) can be quickly understood given the target lives for fuel cell systems: 5000 hours ({approx} 7 months) for automotive, and 40,000 hrs ({approx} 4.6 years) for stationary systems. Thus testing methods that enable more rapid screening of individual components to determine their durability characteristics, such as off-line environmental testing, are needed for evaluating new component durability in a reasonable turn-around time. This allows proposed improvements in a component to be evaluated rapidly and independently, subsequently allowing rapid advancement in PEM fuel cell durability. These tests are also crucial to developers in order to make sure that they do not sacrifice durability while making improvements in costs (e.g. lower platinum group metal [PGM] loading) and performance (e.g. thinner membrane or a GDL with better water management properties). To

  13. Mechanisms of Aβ Clearance and Degradation by Glial Cells.

    PubMed

    Ries, Miriam; Sastre, Magdalena

    2016-01-01

    Glial cells have a variety of functions in the brain, ranging from immune defense against external and endogenous hazardous stimuli, regulation of synaptic formation, calcium homeostasis, and metabolic support for neurons. Their dysregulation can contribute to the development of neurodegenerative disorders, including Alzheimer's disease (AD). One of the most important functions of glial cells in AD is the regulation of Amyloid-β (Aβ) levels in the brain. Microglia and astrocytes have been reported to play a central role as moderators of Aβ clearance and degradation. The mechanisms of Aβ degradation by glial cells include the production of proteases, including neprilysin, the insulin degrading enzyme, and the endothelin-converting enzymes, able to hydrolyse Aβ at different cleavage sites. Besides these enzymes, other proteases have been described to have some role in Aβ elimination, such as plasminogen activators, angiotensin-converting enzyme, and matrix metalloproteinases. Other relevant mediators that are released by glial cells are extracellular chaperones, involved in the clearance of Aβ alone or in association with receptors/transporters that facilitate their exit to the blood circulation. These include apolipoproteins, α2macroglobulin, and α1-antichymotrypsin. Finally, astrocytes and microglia have an essential role in phagocytosing Aβ, in many cases via a number of receptors that are expressed on their surface. In this review, we examine all of these mechanisms, providing an update on the latest research in this field. PMID:27458370

  14. Mechanisms of Aβ Clearance and Degradation by Glial Cells

    PubMed Central

    Ries, Miriam; Sastre, Magdalena

    2016-01-01

    Glial cells have a variety of functions in the brain, ranging from immune defense against external and endogenous hazardous stimuli, regulation of synaptic formation, calcium homeostasis, and metabolic support for neurons. Their dysregulation can contribute to the development of neurodegenerative disorders, including Alzheimer’s disease (AD). One of the most important functions of glial cells in AD is the regulation of Amyloid-β (Aβ) levels in the brain. Microglia and astrocytes have been reported to play a central role as moderators of Aβ clearance and degradation. The mechanisms of Aβ degradation by glial cells include the production of proteases, including neprilysin, the insulin degrading enzyme, and the endothelin-converting enzymes, able to hydrolyse Aβ at different cleavage sites. Besides these enzymes, other proteases have been described to have some role in Aβ elimination, such as plasminogen activators, angiotensin-converting enzyme, and matrix metalloproteinases. Other relevant mediators that are released by glial cells are extracellular chaperones, involved in the clearance of Aβ alone or in association with receptors/transporters that facilitate their exit to the blood circulation. These include apolipoproteins, α2macroglobulin, and α1-antichymotrypsin. Finally, astrocytes and microglia have an essential role in phagocytosing Aβ, in many cases via a number of receptors that are expressed on their surface. In this review, we examine all of these mechanisms, providing an update on the latest research in this field. PMID:27458370

  15. Mechanisms of folate losses during processing: diffusion vs. heat degradation.

    PubMed

    Delchier, Nicolas; Ringling, Christiane; Maingonnat, Jean-François; Rychlik, Michael; Renard, Catherine M G C

    2014-08-15

    Though folates are sensitive to heat treatments, leaching appears to be a major mechanism involved in folate losses in vegetables during processing. The aim of our study was to study folate diffusivity and degradation from spinach and green beans, in order to determine the proportion of each mechanism involved in folate losses. Folate diffusivity constant, calculated according to Fick's second law (Crank, 1975), was 7.4×10(-12) m(2)/s for spinach and 5.8×10(-10) m(2)/s for green beans, which is the same order of magnitude as for sugars and acids for each vegetable considered. Folate thermal degradation kinetics was not monotonous in spinach and green beans especially at 45 °C and did not follow a first order reaction. The proportion of vitamers changed markedly after thermal treatment, with a better retention of formyl derivatives. For spinach, folate losses were mainly due to diffusion while for green beans thermal degradation seemed to be preponderant. PMID:24679802

  16. Chemical degradation mechanisms of membranes for alkaline membrane fuel cells

    NASA Astrophysics Data System (ADS)

    Choe, Yoong-Kee; Henson, Neil J.; Kim, Yu Seung

    2015-12-01

    Chemical degradation mechanisms of membranes for alkaline membrane fuel cells have been investigated using density functional theory (DFT). We have elucidated that the aryl-ether moiety of membranes is one of the weakest site against attack of hydroxide ions. The results of DFT calculations for hydroxide initiated aryl-ether cleavage indicated that the aryl-ether cleavage occurred prior to degradation of cationic functional group. Such a weak nature of the aryl-ether group arises from the electron deficiency of the aryl group as well as the low bond dissociation energy. The DFT results suggests that removal of the aryl-ether group in the membrane should enhance the stability of membranes under alkaline conditions. In fact, an ether fee poly(phenylene) membrane exhibits excellent stability against the attack from hydroxide ions.

  17. Chemical degradation mechanisms of membranes for alkaline membrane fuel cells

    SciTech Connect

    Choe, Yoong-Kee; Henson, Neil J.; Kim, Yu Seung

    2015-12-31

    Chemical degradation mechanisms of membranes for alkaline membrane fuel cells have been investigated using density functional theory (DFT). We have elucidated that the aryl-ether moiety of membranes is one of the weakest site against attack of hydroxide ions. The results of DFT calculations for hydroxide initiated aryl-ether cleavage indicated that the aryl-ether cleavage occurred prior to degradation of cationic functional group. Such a weak nature of the aryl-ether group arises from the electron deficiency of the aryl group as well as the low bond dissociation energy. The DFT results suggests that removal of the aryl-ether group in the membrane should enhance the stability of membranes under alkaline conditions. In fact, an ether fee poly(phenylene) membrane exhibits excellent stability against the attack from hydroxide ions.

  18. Nutrition and age-related eye diseases

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Vision loss among the elderly is an important health problem. Approximately one person in three has some form of vision-reducing eye disease by the age of 65 [1]. Age-related cataract, age-related macular degeneration (AMD), diabetic retinopathy and glaucoma are the major diseases resulting in visu...

  19. Age-Related Changes in Creative Thinking

    ERIC Educational Resources Information Center

    Roskos-Ewoldsen, Beverly; Black, Sheila R.; Mccown, Steven M.

    2008-01-01

    Age-related differences in cognitive processes were used to understand age-related declines in creativity. According to the Geneplore model (Finke, Ward, & Smith, 1992), there are two phases of creativity--generating an idea and exploring the implications of the idea--each with different underlying cognitive processes. These two phases are…

  20. Melanization and phagocytosis: implications for age related macular degeneration.

    PubMed

    Sarangarajan, Rangaprasad; Apte, Shireesh P

    2005-01-01

    Signaling pathways that upregulate melanization in the retinal pigment epithelium (RPE) may also be implicated in the downregulation of rod outer segment (ROS) phagocytosis by the RPE. Melanization activating pathways may also modulate oxygen consumption by the photoreceptors, apolipoprotein E4 levels, and the rate of photoisomerization events such that the net effect may be a reduction in drusen and/or lipofuscin accumulation. An increase in melanin at the apical microvilli of the RPE may shield ROS from light thereby contributing in part to the decrease in the rate of ROS phagocytosis. This decrease in ROS phagocytosis by the RPE may serve to maintain a balance between ingestion and degradation/recycling thereby avoiding an increase to its already substantial metabolic load. Several experimental drugs for age related macular degeneration (ARMD) coincidentally are also capable of decreasing the rate of ROS phagocytosis. This review attempts to identify the signaling pathways that may link the upregulation of melanization to the downregulation of ROS phagocytosis. Phagocytic pathways that are modulated by melanization need to be studied in isolation to determine what role, if any, they possess in ameliorating the onset and progression of ARMD. Many more empirical studies are needed to unravel specific pathways and mechanisms that seem to link melanization with ARMD. PMID:16030499

  1. Degradation of Thiamethoxam in aqueous solution by ozonation: Influencing factors, intermediates, degradation mechanism and toxicity assessment.

    PubMed

    Zhao, Qinghua; Ge, Yanan; Zuo, Peng; Shi, Dong; Jia, Shouhua

    2016-03-01

    This paper focuses on the degradation of Thiamethoxam (THIA) in aqueous solution by ozonation. Four influencing factors: pH, THIA initial concentration, ozone concentration and temperature were investigated in order to optimize the conditions, and pH showed the greatest impact; the removal efficiency reached up to 71.19% under the condition of pH 5-11, THIA initial concentration 50-300 mg L(-1), the ozone concentration 10-22.5 mg L(-1) at 293-308 K after 90 min. Four main intermediates were separated and identified and the possible degradation mechanism was proposed. The luminous intensity of photobacteria and the chemical oxygen demand (COD) were measured to assess the changes of toxicity and mineralization in ozonation process, and results showed that the inhibition rate decreased by 60% and 76% of COD was removed after 180 min with the THIA initial concentration was 200 mg L(-1). Our study powerfully demonstrates that the degradation of THIA in aqueous solution by ozonation is a promising technology. PMID:26714292

  2. ArF pellicle degradation mechanism for resolving CD variation

    NASA Astrophysics Data System (ADS)

    Choi, Hyungseok; Ahn, Yohan; Ryu, Jua; Lee, Yangkoo; An, Bumhyun; Lee, Seokryeol

    2007-03-01

    With the introduction of ArF laser, a binary mask is preferred because a PSM mask is still weak to the crystal defect called as photomask haze although extensive studies trying to resolve the haze impact to a photomask have been performed by various researchers in company and school. However, a new problem was happened after a binary mask introduction that CD variation in an exposure shot is appeared and is gradually increased. And finally, CD variation considerably causes defects in wafer level. It was proven that CD variation is closely related to the change of the reticle transmittance by a lot of researches. In this study, the mechanism of ArF pellicle degradation is focused on because the pellicle degradation affects a reticle transmittance in direct. The components outgassed from a pellicle by the high photon energy of ArF laser, for example carbon or fluorine, are absorbed on the surface of the reticle, so that the transmittance of the reticle is decreased. The phenomena of the pellicle degradation have been studied by the various viewpoints, theoretical background, experiment and results tested in mass production line in this study. Therefore, this study has the important meaning by providing the substantial clues to resolve CD variation problem in a near future.

  3. Animal models of age related macular degeneration

    PubMed Central

    Pennesi, Mark E.; Neuringer, Martha; Courtney, Robert J.

    2013-01-01

    Age related macular degeneration (AMD) is the leading cause of vision loss of those over the age of 65 in the industrialized world. The prevalence and need to develop effective treatments for AMD has lead to the development of multiple animal models. AMD is a complex and heterogeneous disease that involves the interaction of both genetic and environmental factors with the unique anatomy of the human macula. Models in mice, rats, rabbits, pigs and non-human primates have recreated many of the histological features of AMD and provided much insight into the underlying pathological mechanisms of this disease. In spite of the large number of models developed, no one model yet recapitulates all of the features of human AMD. However, these models have helped reveal the roles of chronic oxidative damage, inflammation and immune dysregulation, and lipid metabolism in the development of AMD. Models for induced choroidal neovascularization have served as the backbone for testing new therapies. This article will review the diversity of animal models that exist for AMD as well as their strengths and limitations. PMID:22705444

  4. Review: Axon pathology in age-related neurodegenerative disorders.

    PubMed

    Adalbert, R; Coleman, M P

    2013-02-01

    'Dying back' axon degeneration is a prominent feature of many age-related neurodegenerative disorders and is widespread in normal ageing. Although the mechanisms of disease- and age-related losses may differ, both contribute to symptoms. Here, we review recent advances in understanding axon pathology in age-related neurodegenerative disorders such as Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis and glaucoma. In particular, we highlight the importance of axonal transport, autophagy, traumatic brain injury and mitochondrial quality control. We then place these disease mechanisms in the context of changes to axons and dendrites that occur during normal ageing. We discuss what makes ageing such an important risk factor for many neurodegenerative disorders and conclude that the processes of normal ageing and disease combine at the molecular, cellular or systems levels in a range of disorders to produce symptoms. Pathology identical to disease also occurs at the cellular level in most elderly individuals. Thus, normal ageing and age-related disease are inextricably linked and the term 'healthy ageing' downplays the important contributions of cellular pathology. For a full understanding of normal ageing or age-related disease we must study both processes. PMID:23046254

  5. X-82 to Treat Age-related Macular Degeneration

    ClinicalTrials.gov

    2016-08-16

    Age-Related Macular Degeneration (AMD); Macular Degeneration; Exudative Age-related Macular Degeneration; AMD; Macular Degeneration, Age-related, 10; Eye Diseases; Retinal Degeneration; Retinal Diseases

  6. Photolytic and photocatalytic degradation of tetracycline: Effect of humic acid on degradation kinetics and mechanisms.

    PubMed

    Li, Si; Hu, Jiangyong

    2016-11-15

    The widespread occurrence of tetracycline (TC) in the aquatic environment poses a potential risk to aquatic ecosystem and human health. In this study, elimination of TC by photolysis and TiO2 photocatalysis were investigated by using mercury-free UVA-LED as an alternative light source. Particular emphasis was given to the effect of humic acid (HA) on the reaction kinetics and mechanisms of TC removal. Photolytic degradation of TC was slightly enhanced by HA due to its photosensitization effect, as evidenced by the increased steady-state concentrations of OH. The most abundant transformation product of TC, which was formed by the attack of OH radical, was enhanced during photolytic degradation. During photocatalytic experiments, HA dramatically inhibited TC loss due to the surface deactivation of TiO2 and OH quenching. The steady-state concentration of OH was dramatically decreased in the presence of HA. Identification of transformation products showed that HA could inhibit the oxidation pathways initiated by OH during photocatalysis of TC. These findings provide further insights into the assessment of photolysis and photocatalysis for antibiotics elimination in natural waters where HA exists ubiquitously. PMID:27420385

  7. Nutritional influences on epigenetics and age-related disease

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Nutritional epigenetics has emerged as a novel mechanism underlying gene–diet interactions, further elucidating the modulatory role of nutrition in aging and age-related disease development. Epigenetics is defined as a heritable modification to the DNA that regulates chromosome architecture and modu...

  8. Pathophysiology of ageing, longevity and age related diseases

    PubMed Central

    Bürkle, Alexander; Caselli, Graziella; Franceschi, Claudio; Mariani, Erminia; Sansoni, Paolo; Santoni, Angela; Vecchio, Giancarlo; Witkowski, Jacek M; Caruso, Calogero

    2007-01-01

    On April 18, 2007 an international meeting on Pathophysiology of Ageing, Longevity and Age-Related Diseases was held in Palermo, Italy. Several interesting topics on Cancer, Immunosenescence, Age-related inflammatory diseases and longevity were discussed. In this report we summarize the most important issues. However, ageing must be considered an unavoidable end point of the life history of each individual, nevertheless the increasing knowledge on ageing mechanisms, allows envisaging many different strategies to cope with, and delay it. So, a better understanding of pathophysiology of ageing and age-related disease is essential for giving everybody a reasonable chance for living a long and enjoyable final part of the life. PMID:17683521

  9. Brain site-specific proteome changes in aging-related dementia

    PubMed Central

    Manavalan, Arulmani; Mishra, Manisha; Feng, Lin; Sze, Siu Kwan; Akatsu, Hiroyasu; Heese, Klaus

    2013-01-01

    This study is aimed at gaining insights into the brain site-specific proteomic senescence signature while comparing physiologically aged brains with aging-related dementia brains (for example, Alzheimer's disease (AD)). Our study of proteomic differences within the hippocampus (Hp), parietal cortex (pCx) and cerebellum (Cb) could provide conceptual insights into the molecular mechanisms involved in aging-related neurodegeneration. Using an isobaric tag for relative and absolute quantitation (iTRAQ)-based two-dimensional liquid chromatography coupled with tandem mass spectrometry (2D-LC-MS/MS) brain site-specific proteomic strategy, we identified 950 proteins in the Hp, pCx and Cb of AD brains. Of these proteins, 31 were significantly altered. Most of the differentially regulated proteins are involved in molecular transport, nervous system development, synaptic plasticity and apoptosis. Particularly, proteins such as Gelsolin (GSN), Tenascin-R (TNR) and AHNAK could potentially act as novel biomarkers of aging-related neurodegeneration. Importantly, our Ingenuity Pathway Analysis (IPA)-based network analysis further revealed ubiquitin C (UBC) as a pivotal protein to interact with diverse AD-associated pathophysiological molecular factors and suggests the reduced ubiquitin proteasome degradation system (UPS) as one of the causative factors of AD. PMID:24008896

  10. Mechanisms of charcoal degradation during its initial stages of decomposition

    NASA Astrophysics Data System (ADS)

    Singh, Nimisha; Abiven, Samuel; Schmidt, Michael W. I.

    2010-05-01

    Future climatic changes might result in an increased potential for wildfires, whereby incorporation of charred biomass into soil would increase. The incomplete combustion of biomass results in the production of a chemically heterogeneous class of highly condensed compounds known as pyrogenic C (PyC), which is generally considered resistant to microbial degradation. Recently, studies based on short-term laboratory incubations with soil have indicated that PyC can also eventually degrade (Baldock and Smernik, 2002; Hamer et al., 2004) and it is now widely accepted that a significant quantity of these resistant fraction of soil must have undergone degradation in terrestrial environments. Charcoal has been shown to decompose faster in the initial stages (first 2-3 months) and stabilize later (Kuzyakov et al., 2009). However, studies describing charcoal transformation processes remain scarce. The different potential degradation mechanisms have not yet been studied in combination, and therefore the relative importance for PyC degradation has not been evaluated. We are conducting an incubation experiment to study the biological, chemical and physical degradation/stabilization processes of PyC in soil under controlled conditions. We use Pinus ponderosa 13C/15N labeled (13C: 800 per mil, 15N: 4.2 atom %) wood and charcoal (pyrolysed at 450 °C under N2 atmosphere). We incubate soil from Lägeren forest (Wettingen, Switzerland) with three kind of organic inputs, labeled wood, char and no littler control. The decomposition rates would be estimated based on 13C of CO2 entrapped in NaOH. Time course destructive sampling would be done during the study. Lyophilized soil subsamples will be used for analysis of the amount of 13C incorporation in the microbial biomass using fumigation extraction method and phospholipids fatty acid analysis (PLFA). The remaining PyC in the soil would be characterized for the changes in its chemistry at the molecular level using Benzenepolycarboxlic

  11. Dihydrogen catalysis: a degradation mechanism for N2-fixation intermediates.

    PubMed

    Asatryan, Rubik; Bozzelli, Joseph W; Ruckenstein, Eli

    2012-11-29

    Molecular hydrogen plays multiple roles in activation of nitrogen. Among others, it inhibits the overall process of N(2)-reduction catalyzed by nitrogenase enzyme. The H(2)-assisted dehydrogenation and the H-atom transfer reactions (called dihydrogen catalysis, DHC) are suggested as possible mechanisms for the degradation and removal of potential intermediates formed during the reduction of nitrogen. Several iron-organic model reactions associated with the core stereospecific reaction (cis-N(2)H(2) + H(2) → N(2) + H(2) + H(2)) are examined using a comprehensive density functional theory and ab initio analysis of the corresponding potential energy surfaces. A variety of energetically feasible decomposition pathways are identified for the DHC-oxidation of iron-bound [N(x)H(y)]-species. A liberated diazene intermediate (HN═NH) is suggested to interact in situ with two proximal hydridic H-atoms of an activated (hydrided) Fe-catalyst to produce N(2) and H(2) with a low or even no activation barrier. The majority of identified pathways are shown to be highly sensitive to the electronic environment and spin configuration of metallocomplexes. The H(2)-assisted transport of a single H-atom from a bound [N(x)H(y)] moiety to either the proximal or distal (Fe, S or N) active centers of a catalyst provides an alternative degradation (interconversion) mechanism for the relevant intermediates. The two types of molecular hydrogen-assisted reactions highlighted above, namely, the H(2)-assisted dehydrogenation and the transport of H-atoms, suggest theoretical interpretations for the observed H(2)-inhibition of N(2) activation and HD formation (in the presence of D(2)). The DHC reactions of various [N(x)H(y)] moieties are expected to play significant roles in the industrial high-pressure hydrodenitrification and other catalytic processes involving the metabolism of molecular hydrogen. PMID:23095090

  12. Atomic vacancies significantly degrade the mechanical properties of phosphorene

    NASA Astrophysics Data System (ADS)

    Sha, Zhen-Dong; Pei, Qing-Xiang; Zhang, Ying-Yan; Zhang, Yong-Wei

    2016-08-01

    Due to low formation energies, it is very easy to create atomic defects in phosphorene during its fabrication process. How these atomic defects affect its mechanical behavior, however, remain unknown. Here, we report on a systematic study of the effect of atomic vacancies on the mechanical properties and failure behavior of phosphorene using molecular dynamics simulations. It is found that atomic vacancies induce local stress concentration and cause early bond-breaking, leading to a significant degradation of the mechanical properties of the material. More specifically, a 2% concentration of randomly distributed mono-vacancies is able to reduce the fracture strength by ∼40%. An increase in temperature from 10 to 400 K can further deteriorate the fracture strength by ∼60%. The fracture strength of defective phosphorene is also found to be affected by defect distribution. When the defects are patterned in a line, the reduction in fracture strength greatly depends on the tilt angle and the loading direction. Furthermore, we find that di-vacancies cause an even larger reduction in fracture strength than mono-vacancies when the loading is in an armchair direction. These findings provide important guidelines for the structural design of phosphorene in future applications.

  13. Atomic vacancies significantly degrade the mechanical properties of phosphorene.

    PubMed

    Sha, Zhen-Dong; Pei, Qing-Xiang; Zhang, Ying-Yan; Zhang, Yong-Wei

    2016-08-01

    Due to low formation energies, it is very easy to create atomic defects in phosphorene during its fabrication process. How these atomic defects affect its mechanical behavior, however, remain unknown. Here, we report on a systematic study of the effect of atomic vacancies on the mechanical properties and failure behavior of phosphorene using molecular dynamics simulations. It is found that atomic vacancies induce local stress concentration and cause early bond-breaking, leading to a significant degradation of the mechanical properties of the material. More specifically, a 2% concentration of randomly distributed mono-vacancies is able to reduce the fracture strength by ∼40%. An increase in temperature from 10 to 400 K can further deteriorate the fracture strength by ∼60%. The fracture strength of defective phosphorene is also found to be affected by defect distribution. When the defects are patterned in a line, the reduction in fracture strength greatly depends on the tilt angle and the loading direction. Furthermore, we find that di-vacancies cause an even larger reduction in fracture strength than mono-vacancies when the loading is in an armchair direction. These findings provide important guidelines for the structural design of phosphorene in future applications. PMID:27345189

  14. Nut consumption and age-related disease.

    PubMed

    Grosso, G; Estruch, R

    2016-02-01

    Current knowledge on the effects of nut consumption on human health has rapidly increased in recent years and it now appears that nuts may play a role in the prevention of chronic age-related diseases. Frequent nut consumption has been associated with better metabolic status, decreased body weight as well as lower body weight gain over time and thus reduce the risk of obesity. The effect of nuts on glucose metabolism, blood lipids, and blood pressure is still controversial. However, significant decreased cardiovascular risk has been reported in a number of observational and clinical intervention studies. Thus, findings from cohort studies show that increased nut consumption is associated with a reduced risk of cardiovascular disease and mortality (especially that due to cardiovascular-related causes). Similarly, nut consumption has been also associated with reduced risk of certain cancers, such as colorectal, endometrial, and pancreatic neoplasms. Evidence regarding nut consumption and neurological or psychiatric disorders is scarce, but a number of studies suggest significant protective effects against depression, mild cognitive disorders and Alzheimer's disease. The underlying mechanisms appear to include antioxidant and anti-inflammatory actions, particularly related to their mono- and polyunsaturated fatty acids (MUFA and PUFA, as well as vitamin and polyphenol content). MUFA have been demonstrated to improve pancreatic beta-cell function and regulation of postprandial glycemia and insulin sensitivity. PUFA may act on the central nervous system protecting neuronal and cell-signaling function and maintenance. The fiber and mineral content of nuts may also confer health benefits. Nuts therefore show promise as useful adjuvants to prevent, delay or ameliorate a number of chronic conditions in older people. Their association with decreased mortality suggests a potential in reducing disease burden, including cardiovascular disease, cancer, and cognitive impairments

  15. Age-Related White Matter Changes

    PubMed Central

    Xiong, Yun Yun; Mok, Vincent

    2011-01-01

    Age-related white matter changes (WMC) are considered manifestation of arteriolosclerotic small vessel disease and are related to age and vascular risk factors. Most recent studies have shown that WMC are associated with a host of poor outcomes, including cognitive impairment, dementia, urinary incontinence, gait disturbances, depression, and increased risk of stroke and death. Although the clinical relevance of WMC has been extensively studied, to date, only very few clinical trials have evaluated potential symptomatic or preventive treatments for WMC. In this paper, we reviewed the current understanding in the pathophysiology, epidemiology, clinical importance, chemical biomarkers, and treatments of age-related WMC. PMID:21876810

  16. Pharmacogenetics and age-related macular degeneration.

    PubMed

    Schwartz, Stephen G; Brantley, Milam A

    2011-01-01

    Pharmacogenetics seeks to explain interpatient variability in response to medications by investigating genotype-phenotype correlations. There is a small but growing body of data regarding the pharmacogenetics of both nonexudative and exudative age-related macular degeneration. Most reported data concern polymorphisms in the complement factor H and age-related maculopathy susceptibility 2 genes. At this time, the data are not consistent and no definite conclusions may be drawn. As clinical trials data continue to accumulate, these relationships may become more apparent. PMID:22046503

  17. Benzoxazinone-Mediated Triazine Degradation: A Proposed Reaction Mechanism.

    PubMed

    Willett, C D; Lerch, R N; Lin, C-H; Goyne, K W; Leigh, N D; Roberts, C A

    2016-06-22

    The role of benzoxazinones (Bx, 2-hydroxy-2H-1,4-benzoxazin-3(4H)-one) in triazine resistance in plants has been studied for over half a century. In this research, fundamental parameters of the reaction between DIBOA-Glc (2-β-d-glucopyranosyloxy-4-hydroxy-1,4-benzoxazin-3-one) and atrazine (ATR, 6-chloro-N-ethyl-N'-(1-methylethyl)-1,3,5-triazine-2,4-diamine) were examined. Through a series of experiments employing a variety of chromatographic and spectroscopic techniques, the DIBOA-Glc/ATR reaction was characterized in terms of reactant and product kinetics, stoichiometry, identification of a reaction intermediate, and reaction products formed. Results of these experiments demonstrated that the reaction mechanism proceeds via nucleophilic attack of the hydroxamic acid moiety of DIBOA-Glc at the C-2 position of the triazine ring to form hydroxyatrazine (HA, 2-hydroxy-4-ethylamino-6-isopropylamino-s-triazine), with associated degradation of DIBOA-Glc. Degradation of reactants followed first-order kinetics with a noncatalytic role of DIBOA-Glc. A reaction intermediate was identified as a DIBOA-Glc-HA conjugate, indicating a 1:1 DIBOA-Glc:ATR stoichiometry. Reaction products included HA and Cl(-), but definitive identification of DIBOA-Glc reaction product(s) was not attained. With these reaction parameters elucidated, DIBOA-Glc can be evaluated in terms of its potential for a myriad of applications, including its use to address the problem of widespread ATR contamination of soil and water resources. PMID:27215133

  18. Resorbable composites with bioresorbable glass fibers for load-bearing applications. In vitro degradation and degradation mechanism.

    PubMed

    Lehtonen, Timo J; Tuominen, Jukka U; Hiekkanen, Elina

    2013-01-01

    An in vitro degradation study of three bioresorbable glass fiber-reinforced poly(l-lactide-co-dl-lactide) (PLDLA) composites was carried out in simulated body fluid (SBF), to simulate body conditions, and deionized water, to evaluate the nature of the degradation products. The changes in mechanical and chemical properties were systematically characterized over 52 weeks dissolution time to determine the degradation mechanism and investigate strength retention by the bioresorbable glass fiber-reinforced PLDLA composite. The degradation mechanism was found to be a combination of surface and bulk erosion and does not follow the typical core-accelerated degradation mechanism of poly(α-hydroxyacids). Strength retention by bioresorbable glass fiber-reinforced PLDLA composites can be tailored by changing the oxide composition of the glass fibers, but the structure-property relationship of the glass fibers has to be understood and controlled so that the phenomenon of ion leaching can be utilized to control the degradation rate. Therefore, these high performance composites are likely to open up several new possibilities for utilizing resorbable materials in clinical applications which could not be realized in the past. PMID:22963847

  19. Driving and Age-Related Macular Degeneration

    ERIC Educational Resources Information Center

    Owsley, Cynthia; McGwin, Gerald, Jr.

    2008-01-01

    This article reviews the research literature on driving and age-related macular degeneration, which is motivated by the link between driving and the quality of life of older adults and their increased collision rate. It addresses the risk of crashes, driving performance, driving difficulty, self-regulation, and interventions to enhance, safety,…

  20. Age Related Changes in Preventive Health Behavior.

    ERIC Educational Resources Information Center

    Leventhal, Elaine A.; And Others

    Health behavior may be influenced by age, beliefs, and symptomatology. To examine age-related health beliefs and behaviors with respect to six diseases (the common cold, colon-rectal cancer, lung cancer, heart attack, high blood pressure, and senility), 396 adults (196 males, 200 females) divided into three age groups completed a questionnaire…

  1. Driving and Age-Related Macular Degeneration

    PubMed Central

    Owsley, Cynthia; McGwin, Gerald

    2009-01-01

    This article reviews the research literature on driving and age-related macular degeneration, which is motivated by the link between driving and the quality of life of older adults and their increased collision rate. It addresses the risk of crashes, driving performance, driving difficulty, self-regulation, and interventions to enhance, safety, and considers directions for future research. PMID:20046818

  2. Neuromuscular contributions to age-related weakness

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Age-related physiological change of neuromuscular function is not a linear process and is likely influenced by various biological and behavioral factors (e.g., genetics, nutrition, physical activity level, comorbidities, etc.). These factors contribute to heterogeneity among older adults, which chal...

  3. Semiempirical Predictions of Chemical Degradation Reaction Mechanisms of CL-20 as Related to Molecular Structure

    SciTech Connect

    Qasim, Mohammad M.; Furey, John; Fredrickson, Herbert L.; Szecsody, Jim E.; Mcgrath, Chris J.; Bajpai, Rakesh

    2004-10-01

    Quantum mechanical methods and force field molecular mechanics were used to characterize cage cyclic nitramines and to predict environmental degradation mechanisms. Due to structural similarities it is predicted that, under homologous circumstances, the major environmental RDX degradation pathways should also be effective for CL-20 and similar cyclic nitramines.

  4. INTERIM REPORT ON CONCRETE DEGRADATION MECHANISMS AND ONLINE MONITORING TECHNIQUES

    SciTech Connect

    Mahadevan, Sankaran; Agarwal, Vivek; Neal, Kyle; Kosson, David; Adams, Douglas

    2014-09-01

    The existing fleets of nuclear power plants in the United States have initial operating licenses of 40 years, though most these plants have applied for and received license extensions. As plant structures, systems, and components age, their useful life—considering both structural integrity and performance—is reduced as a result of deterioration of the materials. The online monitoring of concrete structure conducted under the Advanced Instrumentation, Information, and Control Technologies Pathway of the Light Water Reactor Sustainability program at Idaho National Laboratory will develop and demonstrate concrete structures health monitoring capabilities. Assessment and management of aging concrete structures in nuclear plants require a more systematic approach than simple reliance on existing code margins of safety. Therefore, the structural health monitoring is required to produce actionable information regarding structural integrity that supports operational and maintenance decisions. Through this research project, several national laboratories and Vanderbilt University proposes to develop a framework of research activities for the health monitoring of nuclear power plant concrete structures that includes integration of four elements—damage modeling, monitoring, data analytics, and uncertainty quantification. This report briefly discusses available techniques and ongoing challenges in each of the four elements of the proposed framework with emphasis on degradation mechanisms and online monitoring techniques.

  5. Thermal degradation reaction mechanism of xylose: A DFT study

    NASA Astrophysics Data System (ADS)

    Huang, Jinbao; He, Chao; Wu, Longqin; Tong, Hong

    2016-08-01

    The thermal degradation reaction mechanism of xylose as hemicellulose model compound was investigated by using density functional theory methods M062X with the 6-31++G(d,p) basis set. Eight possible pyrolytic reaction pathways were proposed and the standard kinetic and thermodynamic parameters in all reaction pathways were calculated at different temperatures. In reaction pathway (1), xylose is first transformed into acyclic containing-carbonyl isomer, and then the isomer further decomposes through four possible pyrolysis pathways (1-1)-(1-4). Pathways (2) and (3) depict an immediate ring-opening process through the simultaneous breaking of C-O and C-C bonds. Pathways (4)-(7) describe the pyrolysis processes of various anhydro-xyloses through a direct ring-opening process. Pathway (8) gives the evolutionary process of pyranones. The calculation results show that reaction pathways (1), (2) and (5) are the major reaction channels and reaction pathways (3), (4), and (6)-(8) are the competitive reaction channels in pyrolysis of xylose. The major products of xylose pyrolysis are low molecular products such as 2-furaldehyde, glycolaldehyde, acetaldehyde, methylglyoxal and acetone, and the main competitive products are formaldehyde, formic acid, acetic acid, CO2, CH4, acetol, pyranone, and so on.

  6. Lignocellulose degradation mechanisms across the Tree of Life.

    PubMed

    Cragg, Simon M; Beckham, Gregg T; Bruce, Neil C; Bugg, Timothy D H; Distel, Daniel L; Dupree, Paul; Etxabe, Amaia Green; Goodell, Barry S; Jellison, Jody; McGeehan, John E; McQueen-Mason, Simon J; Schnorr, Kirk; Walton, Paul H; Watts, Joy E M; Zimmer, Martin

    2015-12-01

    Organisms use diverse mechanisms involving multiple complementary enzymes, particularly glycoside hydrolases (GHs), to deconstruct lignocellulose. Lytic polysaccharide monooxygenases (LPMOs) produced by bacteria and fungi facilitate deconstruction as does the Fenton chemistry of brown-rot fungi. Lignin depolymerisation is achieved by white-rot fungi and certain bacteria, using peroxidases and laccases. Meta-omics is now revealing the complexity of prokaryotic degradative activity in lignocellulose-rich environments. Protists from termite guts and some oomycetes produce multiple lignocellulolytic enzymes. Lignocellulose-consuming animals secrete some GHs, but most harbour a diverse enzyme-secreting gut microflora in a mutualism that is particularly complex in termites. Shipworms however, house GH-secreting and LPMO-secreting bacteria separate from the site of digestion and the isopod Limnoria relies on endogenous enzymes alone. The omics revolution is identifying many novel enzymes and paradigms for biomass deconstruction, but more emphasis on function is required, particularly for enzyme cocktails, in which LPMOs may play an important role. PMID:26583519

  7. Relative humidity and temperature dependence of mechanical degradation of natural fiber composites

    NASA Astrophysics Data System (ADS)

    Pan, YiHui; Zhong, Zheng

    2016-06-01

    In this paper, the mechanical degradation of natural fiber composites is studied with the consideration of the relative humidity and the temperature. A nonlinear constitutive model is established, which employs an internal variable to describe the mechanical degradation related to the energy dissipation during moisture absorption. The existing experimental researches demonstrated that the mechanical degradation is an irreversible thermodynamic process induced by the degradation of fibers and the damages of interfaces between fiber and matrix, both of which depend on the variation of the relative humidity or the temperature. The evolution of the mechanical degradation is obtained through the determination of dissipation rates as a function of the relative humidity and the temperature. The theoretically predicted mechanical degradations are compared with experimental results of sisal fiber reinforced composites subject to different relative humidity and temperatures, and a good agreement is found.

  8. The mechanism of sulforaphene degradation to different water contents.

    PubMed

    Tian, Guifang; Li, Yuan; Cheng, Li; Yuan, Qipeng; Tang, Pingwah; Kuang, Pengqun; Hu, Jing

    2016-03-01

    Sulforaphene extracted from radish seeds was strongly associated with cancer prevention. However, sulforaphene was unstable in aqueous medium and at high temperature. This instability impairs many useful applications of sulforaphene. In this paper, the stability of sulforaphene (purity above 95%) during storage at -20°C, 4°C and 26°C was studied. The degradation product was purified by preparative HPLC and identified by ESI/MS, NMR ((1)H and (13)C NMR) and FTIR spectroscopy. The degradation pathway of sulforaphene was presented. Furthermore, we found that the degradation rate of sulforaphene was closely related to the water content of sulforaphene sample. The higher the water content was, the faster the sulforaphene sample degraded. A mathematical model was developed to predict the degradation constant at various water contents. It provided a guideline for industry to improve the stability of sulforaphene during preparation, application and storage. PMID:26471648

  9. Smoking and Age-Related Macular Degeneration: Review and Update

    PubMed Central

    Velilla, Sara; García-Medina, José Javier; García-Layana, Alfredo; Pons-Vázquez, Sheila; Pinazo-Durán, M. Dolores; Gómez-Ulla, Francisco; Arévalo, J. Fernando; Díaz-Llopis, Manuel; Gallego-Pinazo, Roberto

    2013-01-01

    Age-related macular degeneration (AMD) is one of the main socioeconomical health issues worldwide. AMD has a multifactorial etiology with a variety of risk factors. Smoking is the most important modifiable risk factor for AMD development and progression. The present review summarizes the epidemiological studies evaluating the association between smoking and AMD, the mechanisms through which smoking induces damage to the chorioretinal tissues, and the relevance of advising patients to quit smoking for their visual health. PMID:24368940

  10. Mechanism and kinetics of parathion degradation under ultrasonic irradiation.

    PubMed

    Yao, Juan-Juan; Gao, Nai-Yun; Li, Cong; Li, Lei; Xu, Bin

    2010-03-15

    The parathion degradation under ultrasonic irradiation in aqueous solution was investigated. The results indicate that at the conditions in question, degradation rate of parathion decreased with increasing initial concentration and decreasing power. The optimal frequency for parathion degradation was 600 kHz. The free radical reactions predominate in the sonochemical degradation of parathion and the reaction zones are predominately at the bubble interface and, to a much lesser extent, in bulk solution. The gas/liquid interfacial regions are the real effective reaction sites for sonochemical degradation of parathion. The reaction can be well described as a gas/liquid heterogeneous reaction which obeys a kinetic model based on Langmuir-Hinshelwood model. The main pathways of parathion degradation by ultrasonic irradiation were also proposed by qualitative and quantitative analysis of organic and inorganic byproducts. It is indicated that the N(2) in air takes part in the parathion degradation through the formation of NO(2) under ultrasonic irradiation. Parathion is decomposed into paraoxon and 4-nitrophenol in the first step via two different pathways, respectively, which is in agreement with the theoretical molecular orbital (MO) calculations. PMID:19854573

  11. Molecular mechanisms associated with xylan degradation by Xanthomonas plant pathogens.

    PubMed

    Santos, Camila Ramos; Hoffmam, Zaira Bruna; de Matos Martins, Vanesa Peixoto; Zanphorlin, Leticia Maria; de Paula Assis, Leandro Henrique; Honorato, Rodrigo Vargas; Lopes de Oliveira, Paulo Sérgio; Ruller, Roberto; Murakami, Mario Tyago

    2014-11-14

    Xanthomonas pathogens attack a variety of economically relevant plants, and their xylan CUT system (carbohydrate utilization with TonB-dependent outer membrane transporter system) contains two major xylanase-related genes, xynA and xynB, which influence biofilm formation and virulence by molecular mechanisms that are still elusive. Herein, we demonstrated that XynA is a rare reducing end xylose-releasing exo-oligoxylanase and not an endo-β-1,4-xylanase as predicted. Structural analysis revealed that an insertion in the β7-α7 loop induces dimerization and promotes a physical barrier at the +2 subsite conferring this unique mode of action within the GH10 family. A single mutation that impaired dimerization became XynA active against xylan, and high endolytic activity was achieved when this loop was tailored to match a canonical sequence of endo-β-1,4-xylanases, supporting our mechanistic model. On the other hand, the divergent XynB proved to be a classical endo-β-1,4-xylanase, despite the low sequence similarity to characterized GH10 xylanases. Interestingly, this enzyme contains a calcium ion bound nearby to the glycone-binding region, which is required for catalytic activity and structural stability. These results shed light on the molecular basis for xylan degradation by Xanthomonas and suggest how these enzymes synergistically assist infection and pathogenesis. Our findings indicate that XynB contributes to breach the plant cell wall barrier, providing nutrients and facilitating the translocation of effector molecules, whereas the exo-oligoxylanase XynA possibly participates in the suppression of oligosaccharide-induced immune responses. PMID:25266726

  12. Investigation of accelerated stress factors and failure/degradation mechanisms

    NASA Astrophysics Data System (ADS)

    Lathrop, J. W.

    1984-03-01

    Results of the performance tests on unencapsulated cells are described. Equivalent circuit parameters; characteristics of a degraded solar cell; and atomic and molecular species at the cell surface are detailed.

  13. The stability and degradation mechanism of sulforaphene in solvents.

    PubMed

    Tian, Guifang; Tang, Pingwah; Xie, Rui; Cheng, Li; Yuan, Qipeng; Hu, Jing

    2016-05-15

    Sulforaphene, a natural compound, has been investigated as a potential anticancer agent. However, the stability of sulforaphene, in various solvents, and its degradation pathway have not been appropriately reported. This instability impairs the preparation process, the biological evaluation experiments, and the applications of sulforaphene. In this study, the stability of sulforaphene stored at 26°C was investigated in each of the following six solvents: two kinds of protic solvents (methanol and ethanol) and four kinds of aprotic solvents (acetonitrile, dichloromethane, ethyl acetate and acetone). Sulforaphene was found to be stable in aprotic solvents and unstable in the protic solvents. The degradation products of sulforaphene in protic solvents (methanol and ethanol) were purified by the preparative HPLC and identified by ESI/MS and NMR ((1)H NMR). The degradation pathways of sulforaphene in methanol and ethanol were proposed. It was found that sulforaphene was degraded into two kinds of structural isomer in alcohols. PMID:26775975

  14. Effects of fatigue on the chemical and mechanical degradation of model stent sub-units.

    PubMed

    Dreher, Maureen L; Nagaraja, Srinidhi; Batchelor, Benjamin

    2016-06-01

    Understanding the fatigue and durability performance of implantable cardiovascular stents is critical for assessing their performance. When the stent is manufactured from an absorbable material, however, this durability assessment is complicated by the transient nature of the device. Methodologies for evaluating the fatigue performance of absorbable stents while accurately simulating the degradation are limited and little is known about the interaction between fatigue and degradation. In this study, we investigated the fatigue behavior and effect of fatigue on the degradation rate for a model absorbable cardiovascular stent. Custom v-shaped stent sub-units manufactured from poly(L-lactide), i.e., PLLA, were subjected to a simultaneous fatigue and degradation study with cycle counts representative of one year of expected in vivo use. Fatigue loading was carried out such that the polymer degraded at a rate that was aligned with a modest degree of fatigue acceleration. Control, un-loaded specimens were also degraded under static immersion conditions representative of simulated degradation without fatigue. The study identified that fatigue loading during degradation significantly increased specimen stiffness and lowered the force at break. Fatigue loading also significantly increased the degree of molecular weight decline highlighting an interaction between mechanical loading and chemical degradation. This study demonstrates that fatigue loading during degradation can affect both the mechanical properties and the chemical degradation rate. The results are important for defining appropriate in vitro degradation conditions for absorbable stent preclinical evaluation. PMID:26759973

  15. Micromechanical Modeling Study of Mechanical Inhibition of Enzymatic Degradation of Collagen Tissues.

    PubMed

    Tonge, Theresa K; Ruberti, Jeffrey W; Nguyen, Thao D

    2015-12-15

    This study investigates how the collagen fiber structure influences the enzymatic degradation of collagen tissues. We developed a micromechanical model of a fibrous collagen tissue undergoing enzymatic degradation based on two central hypotheses. The collagen fibers are crimped in the undeformed configuration. Enzymatic degradation is an energy activated process and the activation energy is increased by the axial strain energy density of the fiber. We determined the intrinsic degradation rate and characteristic energy for mechanical inhibition from fibril-level degradation experiments and applied the parameters to predict the effect of the crimped fiber structure and fiber properties on the degradation of bovine cornea and pericardium tissues under controlled tension. We then applied the model to examine the effect of the tissue stress state on the rate of tissue degradation and the anisotropic fiber structures that developed from enzymatic degradation. PMID:26682825

  16. Age-related regulation of genes: slow homeostatic changes and age-dimension technology

    NASA Astrophysics Data System (ADS)

    Kurachi, Kotoku; Zhang, Kezhong; Huo, Jeffrey; Ameri, Afshin; Kuwahara, Mitsuhiro; Fontaine, Jean-Marc; Yamamoto, Kei; Kurachi, Sumiko

    2002-11-01

    Through systematic studies of pro- and anti-blood coagulation factors, we have determined molecular mechanisms involving two genetic elements, age-related stability element (ASE), GAGGAAG and age-related increase element (AIE), a unique stretch of dinucleotide repeats (AIE). ASE and AIE are essential for age-related patterns of stable and increased gene expression patterns, respectively. Such age-related gene regulatory mechanisms are also critical for explaining homeostasis in various physiological reactions as well as slow homeostatic changes in them. The age-related increase expression of the human factor IX (hFIX) gene requires the presence of both ASE and AIE, which apparently function additively. The anti-coagulant factor protein C (hPC) gene uses an ASE (CAGGAG) to produce age-related stable expression. Both ASE sequences (G/CAGAAG) share consensus sequence of the transcriptional factor PEA-3 element. No other similar sequences, including another PEA-3 consensus sequence, GAGGATG, function in conferring age-related gene regulation. The age-regulatory mechanisms involving ASE and AIE apparently function universally with different genes and across different animal species. These findings have led us to develop a new field of research and applications, which we named “age-dimension technology (ADT)”. ADT has exciting potential for modifying age-related expression of genes as well as associated physiological processes, and developing novel, more effective prophylaxis or treatments for age-related diseases.

  17. Age-related eye disease and gender.

    PubMed

    Zetterberg, Madeleine

    2016-01-01

    Worldwide, the prevalence of moderate to severe visual impairment and blindness is 285 millions, with 65% of visually impaired and 82% of all blind people being 50 years and older. Meta-analyses have shown that two out of three blind people are women, a gender discrepancy that holds true for both developed and developing countries. Cataract accounts for more than half of all blindness globally and gender inequity in access to cataract surgery is the major cause of the higher prevalence of blindness in women. In addition to gender differences in cataract surgical coverage, population-based studies on the prevalence of lens opacities indicate that women have a higher risk of developing cataract. Laboratory as well as epidemiologic studies suggest that estrogen may confer antioxidative protection against cataractogenesis, but the withdrawal effect of estrogen in menopause leads to increased risk of cataract in women. For the other major age-related eye diseases; glaucoma, age-related macular degeneration (AMD) and diabetic retinopathy, data are inconclusive. Due to anatomic factors, angle closure glaucoma is more common in women, whereas the dominating glaucoma type; primary open-angle glaucoma (POAG), is more prevalent in men. Diabetic retinopathy also has a male predominance and vascular/circulatory factors have been implied both in diabetic retinopathy and in POAG. For AMD, data on gender differences are conflicting although some studies indicate increased prevalence of drusen and neovascular AMD in women. To conclude, both biologic and socioeconomic factors must be considered when investigating causes of gender differences in the prevalence of age-related eye disease. PMID:26508081

  18. The suprachiasmatic nucleus: age-related decline in biological rhythms.

    PubMed

    Nakamura, Takahiro J; Takasu, Nana N; Nakamura, Wataru

    2016-09-01

    Aging is associated with changes in sleep duration and quality, as well as increased rates of pathologic/disordered sleep. While several factors contribute to these changes, emerging research suggests that age-related changes in the mammalian central circadian clock within the suprachiasmatic nucleus (SCN) may be a key factor. Prior work from our group suggests that circadian output from the SCN declines because of aging. Furthermore, we have previously observed age-related infertility in female mice, caused by a mismatch between environmental light-dark cycles and the intrinsic, internal biological clocks. In this review, we address regulatory mechanisms underlying circadian rhythms in mammals and summarize recent literature describing the effects of aging on the circadian system. PMID:26915078

  19. A Review of Molecular-Level Mechanism of Membrane Degradation in the Polymer Electrolyte Fuel Cell

    PubMed Central

    Ishimoto, Takayoshi; Koyama, Michihisa

    2012-01-01

    Chemical degradation of perfluorosulfonic acid (PFSA) membrane is one of the most serious problems for stable and long-term operations of the polymer electrolyte fuel cell (PEFC). The chemical degradation is caused by the chemical reaction between the PFSA membrane and chemical species such as free radicals. Although chemical degradation of the PFSA membrane has been studied by various experimental techniques, the mechanism of chemical degradation relies much on speculations from ex-situ observations. Recent activities applying theoretical methods such as density functional theory, in situ experimental observation, and mechanistic study by using simplified model compound systems have led to gradual clarification of the atomistic details of the chemical degradation mechanism. In this review paper, we summarize recent reports on the chemical degradation mechanism of the PFSA membrane from an atomistic point of view. PMID:24958288

  20. Mechanisms and regulation of the degradation of cyclin B.

    PubMed Central

    Hershko, A

    1999-01-01

    The degradation of the cyclin B subunit of protein kinase Cdk1/cyclin B is required for inactivation of the kinase and exit from mitosis. Cyclin B is degraded by the ubiquitin pathway, a system involved in most selective protein degradation in eukaryotic cells. In this pathway, proteins are targeted for degradation by ligation to ubiquitin, a process carried out by the sequential action of three enzymes: the ubiquitin-activating enzyme E1, a ubiquitin-carrier protein E2 and a ubiquitin-protein ligase E3. In the system responsible for cyclin B degradation, the E3-like function is carried out by a large complex called cyclosome or anaphase-promoting complex (APC). In the early embryonic cell cycles, the cyclosome is inactive in the interphase, but becomes active at the end of mitosis. Activation requires phosphorylation of the cyclosome/APC by protein kinase Cdk1/cyclin B. The lag kinetics of cyclosome activation may be explained by Suc1-assisted multiple phosphorylations of partly phosphorylated complex. The presence of a Fizzy/Cdc20-like protein is necessary for maximal activity of the mitotic form of cyclosome/APC in cyclin-ubiquitin ligation. PMID:10582242

  1. Sonolytic and sonophotolytic degradation of Carbamazepine: Kinetic and mechanisms.

    PubMed

    Rao, Yongfang; Yang, Haisong; Xue, Dan; Guo, Yang; Qi, Fei; Ma, Jun

    2016-09-01

    An in-depth investigation on the ultrasonic decomposition of Carbamazepine (CBZ), one of the most regularly identified drugs in the environment, was conducted. The effects of diverse variables were evaluated, such as frequency, power, solution pH, initial CBZ concentration and varied inorganic anions. Reaction order was determined on the basis of analyzing reaction kinetics of CBZ degradation. The sonophotolysis and photolysis of CBZ was also examined in this contribution. The influence of water composition on the sonolytic and sonophotolytic elimination of CBZ was analyzed. Additionally, 21 intermediates were identified during sonolytic degradation of CBZ based on LC/ESI-MS/MS analysis, among which two escaped from the detection in previous studies. Possible decay pathways were proposed accordingly. The epoxidation, cleavage of double bond, hydration, hydroxylation, ring contraction and intramolecular cyclization were believed to be involved in sonochemical degradation of CBZ. PMID:27150783

  2. Risk Factors for Age-Related Maculopathy

    PubMed Central

    Connell, Paul P.; Keane, Pearse A.; O'Neill, Evelyn C.; Altaie, Rasha W.; Loane, Edward; Neelam, Kumari; Nolan, John M.; Beatty, Stephen

    2009-01-01

    Age-related maculopathy (ARM) is the leading cause of blindness in the elderly. Although beneficial therapeutic strategies have recently begun to emerge, much remains unclear regarding the etiopathogenesis of this disorder. Epidemiologic studies have enhanced our understanding of ARM, but the data, often conflicting, has led to difficulties with drawing firm conclusions with respect to risk for this condition. As a consequence, we saw a need to assimilate the published findings with respect to risk factors for ARM, through a review of the literature appraising results from published cross-sectional studies, prospective cohort studies, case series, and case control studies investigating risk for this condition. Our review shows that, to date, and across a spectrum of epidemiologic study designs, only age, cigarette smoking, and family history of ARM have been consistently demonstrated to represent risk for this condition. In addition, genetic studies have recently implicated many genes in the pathogenesis of age-related maculopathy, including Complement Factor H, PLEKHA 1, and LOC387715/HTRA1, demonstrating that environmental and genetic factors are important for the development of ARM suggesting that gene-environment interaction plays an important role in the pathogenesis of this condition. PMID:20339564

  3. Benzoxazinone-mediated triazine degradation: A proposed reaction mechanism

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The role of benzoxazinones (Bx, 2-hydroxy-2H-1,4-benzoxazin-3(4H)-one)) in triazine degradation and resistance has been studied for over half a century. In this research, the fundamental parameters of the reaction between DIBOA-Glc (2-ß-D-glucopyranosyloxy-4-hydroxy-1,4-benzoxazin-3-one) and atrazin...

  4. Physics of Lipofuscin Formation and Growth in Age Related Macular Degeneration

    NASA Astrophysics Data System (ADS)

    Family, Fereydoon; Mazzitello, K. I.; Arizmendi, C. M.; Grossniklaus, Hans E.

    2010-02-01

    Age-related macular degeneration (AMD) is the leading cause of blindness beyond the age of 50 years. The most common pathogenic mechanism that leads to AMD is choroidal neovascularization (CNV). CNV is produced by accumulation of residual material caused by aging of retinal pigment epithelium cells (RPE). With time, incompletely degraded membrane material builds up in the RPE in the form of lipofuscin. Lipofuscin is made of free-radical-damaged protein and fat, which forms not only in AMD, but also Alzheimer disease, and Parkinson disease. We will present the results of a study of the kinetics of lipofuscin growth in RPE cells using Kinetic Monte Carlo simulations and scaling theory on a cluster aggregation model. The model captures the essential physics of lipofuscin growth in the cells. A remarkable feature is that small particles may be removed from the cells while the larger ones become fixed and grow by aggregation. We compare our results to the number of lipofuscin granules in eyes with early age-related degeneration. )

  5. Age-related decline in bottom-up processing and selective attention in the very old

    PubMed Central

    Zhuravleva, T. Y.; Alperin, B. R.; Haring, A. E.; Rentz, D. M.; Holcomb, P. J.; Daffner, K. R.

    2014-01-01

    Previous research demonstrating age-related deficits in selective attention have not included old-old adults, an increasingly important group to study. The current investigation compared event-related potentials (ERPs) in 15 young-old (65–79) and 23 old-old (80–99) subjects during a color-selective attention task. Subjects responded to target letters in a specified color (Attend) while ignoring letters in a different color (Ignore) under both low and high load. There were no group differences in visual acuity, accuracy, reaction time, or latency of early ERP components. The old-old group showed a disruption in bottom-up processing, indexed by a substantially diminished posterior N1 (smaller amplitude). They also demonstrated markedly decreased modulation of bottom-up processing based on selected visual features, indexed by the posterior selection negativity (SN), with similar attenuation under both loads. In contrast, there were no group differences in frontally-mediated attentional selection, measured by the anterior selection positivity (SP). There was a robust inverse relationship between the size of the SN and SP (the smaller the SN, the larger the SP), which may represent an anteriorly-supported compensatory mechanism. In the absence of a decline in top-down modulation indexed by the SP, the diminished SN may reflect age-related degradation of early bottom-up visual processing in old-old adults. PMID:24887611

  6. MRZ-99030 - A novel modulator of Aβ aggregation: I - Mechanism of action (MoA) underlying the potential neuroprotective treatment of Alzheimer's disease, glaucoma and age-related macular degeneration (AMD).

    PubMed

    Parsons, Christopher G; Ruitenberg, Maarten; Freitag, Christine E; Sroka-Saidi, Kamila; Russ, Hermann; Rammes, Gerhard

    2015-05-01

    Therapeutic approaches addressing β-amyloid1-42 (Aβ1-42) aggregation represent a promising neuroprotective strategy for the treatment of Alzheimer's disease, dry age-related macular degeneration (AMD) and glaucoma. MRZ-99030 is a dipeptide containing d-tryptophan and 2-amino-2-methylpropionic acid in clinical development for the topical treatment of glaucoma and AMD. MRZ-99030 is an Aβ aggregation modulator, previously reported to prevent the formation of soluble toxic oligomeric Aβ species. The present study confirmed that MRZ-99030 prevents the formation of oligomeric Aβ species using similar SDS-PAGE experiments. However, additional data from TR-FRET, DLS and AFM experiments revealed that MRZ-99030 does not directly prevent early protein/protein interactions between monomeric Aβ, but rather promotes the formation of large, non-amyloidogenic, amorphous Aβ aggregates and thereby reduces the amount of intermediate toxic soluble oligomeric Aβ species. The affinity of MRZ-99030 to Aβ1-42 determined by SPR was 28.4 nM but the ratio of compound to Aβ is also important: a 10-20 fold excess of MRZ-99030 over Aβ is probably required for effective modulation of protein/protein interactions. For example, in glaucoma, assuming a maximal Aβ concentration of 1-15 nM in the retina, up to 150 nM MRZ-99030 could be required at the protein target. In line with this consideration, MRZ-99030 was able to prevent Aβ-induced toxicity on PC12 cells, retinal ganglion cells and retinal pigment epithelium cells when present at a 10-20 fold stoichiometric excess over Aβ. Moreover, in vivo studies demonstrate the neuroprotective potential of MRZ-99030 after systemic and topical administration in animal models of Alzheimer's disease and glaucoma/AMD respectively. PMID:25634238

  7. Age-related shifts in distortion product otoacoustic emissions peak-ratios and amplitude modulation spectra.

    PubMed

    Lai, Jesyin; Bartlett, Edward L

    2015-09-01

    Amplitude modulation (AM) is an important temporal cue for precise speech and complex sound recognition. However, functional decline of the auditory periphery as well as degradation of central auditory processing due to aging can reduce the salience and resolution of temporal cues. Age-related deficits in central temporal processing have previously been observed at more rapid AM frequencies and various AM depths. These centrally observed changes result from cochlear changes compounded with changes along the ascending auditory pathway. In fact, a decrease in ability to detect temporally modulated sounds accurately could originate from changes in cochlear filtering properties and in cochlear mechanics due to aging. Nonetheless, few studies have examined cochlear mechanisms in AM detection. To assess integrity of the mechanical properties of the auditory periphery, distortion product otoacoustic emissions (DPOAEs) are a tool commonly used in clinics and in research. In this study, we measured DPOAEs to reveal age-related changes in peak f2/f1 ratio and degradation in AM detection by basilar membrane vibration. Two tones (f1 and f2, f2 > f1) at various f2/f1 ratios and simultaneous presentation of one AM and one pure tone were used as stimuli to evoke DPOAEs. In addition of observing reduced DPOAE amplitudes and steeper slopes in the input-output DPOAE functions, higher peak f2/f1 ratios and broader f2/f1 tuning were also observed in aged animals. Aged animals generally had lower distortion product (DP) and first sideband (SB 1) responses evoked by an f1 pure tone and an f2 AM tone, regardless of whether the AM frequency was 45 Hz or 128 Hz. SB 1 thresholds, which corresponds to the smallest stimulus AM depth that can induce cochlear vibrations at the DP generator locus, were higher in aged animals as well. The results suggest that age-related changes in peak f2/f1 ratio and AM detection by basilar membrane vibration are consistent with a reduction in endocochlear

  8. Age-related Shifts in Distortion Product Otoacoustic Emissions Peak-ratios and Amplitude Modulation Spectra

    PubMed Central

    Lai, Jesyin; Bartlett, Edward L.

    2015-01-01

    Amplitude modulation (AM) is an important temporal cue for precise speech and complex sound recognition. However, functional decline of the auditory periphery as well as degradation of central auditory processing due to aging can reduce the salience and resolution of temporal cues. Age-related deficits in central temporal processing have previously been observed at more rapid AM frequencies and various AM depths. These centrally observed changes result from cochlear changes compounded with changes along the ascending auditory pathway. In fact, a decrease in ability to detect temporally modulated sounds accurately could originate from changes in cochlear filtering properties and in cochlear mechanics due to aging. Nonetheless, few studies have examined cochlear mechanisms in AM detection. To assess integrity of the mechanical properties of the auditory periphery, distortion product otoacoustic emissions (DPOAEs) are a tool commonly used in clinics and in research. In this study, we measured DPOAEs to reveal age-related changes in peak f2/f1 ratio and degradation in AM detection by basilar membrane vibration. Two tones (f1 and f2, f2>f1) at various f2/f1 ratios and simultaneous presentation of one AM and one pure tone were used as stimuli to evoke DPOAEs. In addition of observing reduced DPOAE amplitudes and steeper slopes in the input-output DPOAE functions, higher peak f2/f1 ratios and broader f2/f1 tuning were also observed in aged animals. Aged animals generally had lower distortion product (DP) and first sideband (SB 1) responses evoked by an f1 pure tone and an f2 AM tone, regardless of whether the AM frequency was 45 Hz or 128 Hz. SB 1 thresholds, which corresponds to the smallest stimulus AM depth that can induce cochlear vibrations at the DP generator locus, were higher in aged animals as well. The results suggest that age-related changes in peak f2/f1 ratio and AM detection by basilar membrane vibration are consistent with a reduction in endocochlear

  9. Topography of age-related changes in sleep spindles.

    PubMed

    Martin, Nicolas; Lafortune, Marjolaine; Godbout, Jonathan; Barakat, Marc; Robillard, Rebecca; Poirier, Gaétan; Bastien, Célyne; Carrier, Julie

    2013-02-01

    Aging induces multiple changes to sleep spindles, which may hinder their alleged functional role in memory and sleep protection mechanisms. Brain aging in specific cortical regions could affect the neural networks underlying spindle generation, yet the topography of these age-related changes is currently unknown. In the present study, we analyzed spindle characteristics in 114 healthy volunteers aged between 20 and 73 years over 5 anteroposterior electroencephalography scalp derivations. Spindle density, amplitude, and duration were higher in young subjects than in middle-aged and elderly subjects in all derivations, but the topography of age effects differed drastically. Age-related decline in density and amplitude was more prominent in anterior derivations, whereas duration showed a posterior prominence. Age groups did not differ in all-night spindle frequency for any derivation. These results show that age-related changes in sleep spindles follow distinct topographical patterns that are specific to each spindle characteristic. This topographical specificity may provide a useful biomarker to localize age-sensitive changes in underlying neural systems during normal and pathological aging. PMID:22809452

  10. Senescent cells: SASPected drivers of age-related pathologies.

    PubMed

    Ovadya, Yossi; Krizhanovsky, Valery

    2014-12-01

    The progression of physiological ageing is driven by intracellular aberrations including telomere attrition, genomic instability, epigenetic alterations and loss of proteostasis. These in turn damage cells and compromise their functionality. Cellular senescence, a stable irreversible cell-cycle arrest, is elicited in damaged cells and prevents their propagation in the organism. Under normal conditions, senescent cells recruit the immune system which facilitates their removal from tissues. Nevertheless, during ageing, tissue-residing senescent cells tend to accumulate, and might negatively impact their microenvironment via profound secretory phenotype with pro-inflammatory characteristics, termed senescence-associated secretory phenotype (SASP). Indeed, senescent cells are mostly abundant at sites of age-related pathologies, including degenerative disorders and malignancies. Interestingly, studies on progeroid mice indicate that selective elimination of senescent cells can delay age-related deterioration. This suggests that chronic inflammation induced by senescent cells might be a main driver of these pathologies. Importantly, senescent cells accumulate as a result of deficient immune surveillance, and their removal is increased upon the use of immune stimulatory agents. Insights into mechanisms of senescence surveillance could be combined with current approaches for cancer immunotherapy to propose new preventive and therapeutic strategies for age-related diseases. PMID:25217383

  11. Mechanical property degradation of graphite/polyimide composites after exposure to moisture or shuttle orbiter fluids

    NASA Technical Reports Server (NTRS)

    Lisagor, W. B.

    1979-01-01

    The effects of moisture exposure on the mechanical properties of graphite polyimide systems are presented. The mechanism of the degradation and the magnitude of the affect associated with specific mechanical properties is investigated. An experimental effort involving exposure to selected environmental variables and subsequent mechanical property testing and analysis is included.

  12. Pathogenesis of Age-Related Bone Loss in Humans

    PubMed Central

    2013-01-01

    Background. Although data from rodent systems are extremely useful in providing insights into possible mechanisms of age-related bone loss, concepts evolving from animal models need to ultimately be tested in humans. Methods. This review provides an update on mechanisms of age-related bone loss in humans based on the author’s knowledge of the field and focused literature reviews. Results. Novel imaging, experimental models, biomarkers, and analytic techniques applied directly to human studies are providing new insights into the patterns of bone mass acquisition and loss as well as the role of sex steroids, in particular estrogen, on bone metabolism and bone loss with aging in women and men. These studies have identified the onset of trabecular bone loss at multiple sites that begins in young adulthood and remains unexplained, at least based on current paradigms of the mechanisms of bone loss. In addition, estrogen appears to be a major regulator of bone metabolism not only in women but also in men. Studies assessing mechanisms of estrogen action on bone in humans have identified effects of estrogen on RANKL expression by several different cell types in the bone microenvironment, a role for TNF-α and IL-1β in mediating effects of estrogen deficiency on bone, and possible regulation of the Wnt inhibitor, sclerostin, by estrogen. Conclusions. There have been considerable advances in our understanding of age-related bone loss in humans. However, there are also significant gaps in knowledge, particularly in defining cell autonomous changes in bone in human studies to test or validate concepts emerging from studies in rodents. Decision Editor: Luigi Ferrucci, MD, PhD PMID:22923429

  13. Distraction can reduce age-related forgetting.

    PubMed

    Biss, Renée K; Ngo, K W Joan; Hasher, Lynn; Campbell, Karen L; Rowe, Gillian

    2013-04-01

    In three experiments, we assessed whether older adults' generally greater tendency to process distracting information can be used to minimize widely reported age-related differences in forgetting. Younger and older adults studied and recalled a list of words on an initial test and again on a surprise test after a 15-min delay. In the middle (Experiments 1a and 2) or at the end (Experiment 3) of the delay, participants completed a 1-back task in which half of the studied words appeared as distractors. Across all experiments, older adults reliably forgot unrepeated words; however, older adults rarely or never forgot the words that had appeared as distractors, whereas younger adults forgot words in both categories. Exposure to distraction may serve as a rehearsal episode for older adults, and thus as a method by which general distractibility may be co-opted to boost memory. PMID:23426890

  14. Consequences of Age-Related Cognitive Declines

    PubMed Central

    Salthouse, Timothy

    2013-01-01

    Adult age differences in a variety of cognitive abilities are well documented, and many of those abilities have been found to be related to success in the workplace and in everyday life. However, increased age is seldom associated with lower levels of real-world functioning, and the reasons for this lab-life discrepancy are not well understood. This article briefly reviews research concerned with relations of age to cognition, relations of cognition to successful functioning outside the laboratory, and relations of age to measures of work performance and achievement. The final section discusses several possible explanations for why there are often little or no consequences of age-related cognitive declines in everyday functioning. PMID:21740223

  15. [Age-related changes of sensory system].

    PubMed

    Iwamoto, Toshihiko; Hanyu, Haruo; Umahara, Takahiko

    2013-10-01

    Pathological processes usually superimpose on physiological aging even in the sensory system including visual, hearing, olfactory, taste and somatosensory functions. Representative changes of age-related changes are presbyopia, cataracts, and presbyacusis. Reduced sense of smell is seen in normal aging, but the prominent reduction detected by the odor stick identification test is noticed especially in early stage of Alzheimer or Parkinson disease. Reduced sense of taste is well-known especially in salty sense, while the changes of sweet, bitter, and sour tastes are different among individuals. Finally, deep sensation of vibration and proprioception is decreased with age as well as superficial sensation (touch, temperature, pain). As a result, impaired sensory system could induce deterioration of the activities of daily living and quality of life in the elderly. PMID:24261198

  16. Macular carotenoids and age-related maculopathy.

    PubMed

    O'Connell, Eamonn; Neelam, Kumari; Nolan, John; Au Eong, Kah-Guan; Beatty, Stephan

    2006-11-01

    Lutein (L) and zeaxanthin (Z) are concentrated at the macula, where they are collectively known as macular pigment (MP), and where they are believed to play a major role in protecting retinal tissues against oxidative stress. Whilst the exact pathogenesis of age-related maculopathy (ARM) remains unknown, the disruption of cellular processes by oxidative stress may play an important role. Manipulation of dietary intake of L and Z has been shown to augment MP, thereby raising hopes that dietary supplementation with these carotenoids might prevent, delay, or modify the course of ARM. This article discusses the scientific rationale supporting the hypothesis that L and Z are protective against ARM, and presents the recent evidence germane to this theory. PMID:17160199

  17. [Epidemiology of age-related macular degeneration].

    PubMed

    Brandl, C; Stark, K J; Wintergerst, M; Heinemann, M; Heid, I M; Finger, R P

    2016-09-01

    Age-related macular degeneration (AMD) is the main cause of blindness in industrialized societies. Population-based epidemiological investigations generate important data on prevalence, incidence, risk factors, and future trends. This review summarizes the most important epidemiological studies on AMD with a focus on their transferability to Germany including existing evidence for the main risk factors for AMD development and progression. Future tasks, such as the standardization of grading systems and the use of recent retinal imaging technology in epidemiological studies are discussed. In Germany, epidemiological data on AMD are scarce. However, the need for epidemiological research in ophthalmology is currently being addressed by several recently started population-based studies. PMID:27541733

  18. Age-related macular degeneration: current treatments

    PubMed Central

    Hubschman, Jean Pierre; Reddy, Shantan; Schwartz, Steven D

    2009-01-01

    Purpose: Although important progress has been made in understanding age-related macular degeneration (AMD), management of the disease continues to be a challenge. AMD research has led to a widening of available treatment options and improved prognostic perspectives. This essay reviews these treatment options. Design: Interpretative essay. Methods: Literature review and interpretation. Results: Current treatments to preserve vision in patients with non-exudative AMD include antioxidant vitamins and mineral supplementations. Exudative AMD is currently most often treated monthly with anti-VEGF intravitreal injections. However, investigators are beginning to experiment with combination therapy and surgical approaches in an attempt to limit the number of treatment and reduce the financial burden on the health care system. Conclusion: By better understanding the basis and pathogenesis of AMD, newer therapies will continue to be developed that target specific pathways in patients with AMD, with the hoped for outcome of better management of the disease and improved visual acuity. PMID:19668560

  19. The Neural Consequences of Age-Related Hearing Loss.

    PubMed

    Peelle, Jonathan E; Wingfield, Arthur

    2016-07-01

    During hearing, acoustic signals travel up the ascending auditory pathway from the cochlea to auditory cortex; efferent connections provide descending feedback. In human listeners, although auditory and cognitive processing have sometimes been viewed as separate domains, a growing body of work suggests they are intimately coupled. Here, we review the effects of hearing loss on neural systems supporting spoken language comprehension, beginning with age-related physiological decline. We suggest that listeners recruit domain general executive systems to maintain successful communication when the auditory signal is degraded, but that this compensatory processing has behavioral consequences: even relatively mild levels of hearing loss can lead to cascading cognitive effects that impact perception, comprehension, and memory, leading to increased listening effort during speech comprehension. PMID:27262177

  20. Methods And Systms For Analyzing The Degradation And Failure Of Mechanical Systems

    DOEpatents

    Jarrell, Donald B.; Sisk, Daniel R.; Hatley, Darrel D.; Kirihara, Leslie J.; Peters, Timothy J.

    2005-02-08

    Methods and systems for identifying, understanding, and predicting the degradation and failure of mechanical systems are disclosed. The methods include measuring and quantifying stressors that are responsible for the activation of degradation mechanisms in the machine component of interest. The intensity of the stressor may be correlated with the rate of physical degradation according to some determinable function such that a derivative relationship exists between the machine performance, degradation, and the underlying stressor. The derivative relationship may be used to make diagnostic and prognostic calculations concerning the performance and projected life of the machine. These calculations may be performed in real time to allow the machine operator to quickly adjust the operational parameters of the machinery in order to help minimize or eliminate the effects of the degradation mechanism, thereby prolonging the life of the machine. Various systems implementing the methods are also disclosed.

  1. Plumbrook Hypersonic Tunnel Facility Graphite Furnace Degradation Mechanisms

    NASA Technical Reports Server (NTRS)

    Jacobson, Nathan S.

    1999-01-01

    A recent rebuild revealed extensive degradation to the large graphite induction furnace in the Hypersonic Tunnel Facility (HTF). This damage to the graphite blocks and insulating felt is examined and modeled with thermochemical equilibrium codes. The primary reactions appear to be with water vapor and the nitrogen purge gas. Based on these conclusions, several changes are recommended. An inert purge gas (e.g. argon or helium) and controlling and monitoring water vapor to about 10 ppm should decrease the damage substantially.

  2. Degradation of TATP, TNT, and RDX using mechanically alloyed metals

    NASA Technical Reports Server (NTRS)

    Clausen, Christian (Inventor); Geiger, Cherie (Inventor); Sigman, Michael (Inventor); Fidler, Rebecca (Inventor)

    2012-01-01

    Bimetallic alloys prepared in a ball milling process, such as iron nickel (FeNi), iron palladium (FePd), and magnesium palladium (MgPd) provide in situ catalyst system for remediating and degrading nitro explosive compounds. Specifically, munitions, such as, 2,4,6-trinitrotoluene (TNT), cyclo-1,3,5-trimethylene-2,4,6-trinitramine (RDX), nitrocellulose and nitroglycerine that have become contaminants in groundwater, soil, and other structures are treated on site to remediate explosive contamination.

  3. Degradation mechanism for planar heterojunction perovskite solar cells

    NASA Astrophysics Data System (ADS)

    Yamamoto, Kouhei; Furumoto, Yoshikazu; Shahiduzzaman, M.; Kuwabara, Takayuki; Takahashi, Kohshin; Taima, Tetsuya

    2016-04-01

    Organic-inorganic hybrid perovskite materials have recently emerged as a promising cost- and energy-efficient light absorber material for photovoltaic applications. Unfortunately, perovskite solar cells have a problem with decreasing power conversion efficiency owing to their degradation in air. To clarify the cause of the degradation of perovskite solar cells, we exposed deposited CH3NH3PbI3 and HC(NH2)2PbI3 films to an O2 or (H2O+N2) atmosphere condition. Analysis of these films revealed that a large energy band gap was observed as a result of the influence of the H2O molecule in CH3NH3PbI3 and HC(NH2)2PbI3. Under the (H2O+N2) atmosphere condition, the existence of CH3NH3I and HC(NH2)2I molecules was found to affect the morphology and as well as the crystalline diffraction peak. The resultant perovskite crystalline structure was degraded by H2O molecules under the air exposure condition.

  4. Characterization of the Degradation Mechanisms of Lysine-derived Aliphatic Poly(ester urethane) Scaffolds

    PubMed Central

    Hafeman, Andrea E.; Zienkiewicz, Katarzyna J.; Zachman, Angela L.; Sung, Hak-Joon; Nanney, Lillian B.; Davidson, Jeffrey M.; Guelcher, Scott A.

    2010-01-01

    Characterization of the degradation mechanism of polymeric scaffolds and delivery systems for regenerative medicine is essential to assess their clinical applicability. Key performance criteria include induction of a minimal, transient inflammatory response and controlled degradation to soluble non-cytotoxic breakdown products that are cleared from the body by physiological processes. Scaffolds fabricated from biodegradable poly(ester urethane)s (PEURs) undergo controlled degradation to non-cytotoxic breakdown products and support the ingrowth of new tissue in preclinical models of tissue regeneration. While previous studies have shown that PEUR scaffolds prepared from lysine-derived polyisocyanates degrade faster under in vivo compared to in vitro conditions, the degradation mechanism is not well understood. In this study, we have shown that PEUR scaffolds prepared from lysine triisocyanate (LTI) or a trimer of hexamethylene diisocyanate (HDIt) undergo hydrolytic, esterolytic, and oxidative degradation. Hydrolysis of ester bonds to yield α-hydroxy acids is the dominant mechanism in buffer, and esterolytic media modestly increase the degradation rate. While HDIt scaffolds show a modest (<20%) increase in degradation rate in oxidative medium, LTI scaffolds degrade six times faster in oxidative medium. Furthermore, the in vitro rate of degradation of LTI scaffolds in oxidative medium approximates the in vivo rate in rat excisional wounds, and histological sections show macrophages expressing myeloperoxidase at the material surface. While recent preclinical studies have underscored the potential of injectable PEUR scaffolds and delivery systems for tissue regeneration, this promising class of biomaterials has a limited regulatory history. Elucidation of the macrophage-mediated oxidative mechanism by which LTI scaffolds degrade in vivo provides key insights into the ultimate fate of these materials when injected into the body. PMID:20864156

  5. Characterization of the degradation mechanisms of lysine-derived aliphatic poly(ester urethane) scaffolds.

    PubMed

    Hafeman, Andrea E; Zienkiewicz, Katarzyna J; Zachman, Angela L; Sung, Hak-Joon; Nanney, Lillian B; Davidson, Jeffrey M; Guelcher, Scott A

    2011-01-01

    Characterization of the degradation mechanism of polymeric scaffolds and delivery systems for regenerative medicine is essential to assess their clinical applicability. Key performance criteria include induction of a minimal, transient inflammatory response and controlled degradation to soluble non-cytotoxic breakdown products that are cleared from the body by physiological processes. Scaffolds fabricated from biodegradable poly(ester urethane)s (PEURs) undergo controlled degradation to non-cytotoxic breakdown products and support the ingrowth of new tissue in preclinical models of tissue regeneration. While previous studies have shown that PEUR scaffolds prepared from lysine-derived polyisocyanates degrade faster under in vivo compared to in vitro conditions, the degradation mechanism is not well understood. In this study, we have shown that PEUR scaffolds prepared from lysine triisocyanate (LTI) or a trimer of hexamethylene diisocyanate (HDIt) undergo hydrolytic, esterolytic, and oxidative degradation. Hydrolysis of ester bonds to yield α-hydroxy acids is the dominant mechanism in buffer, and esterolytic media modestly increase the degradation rate. While HDIt scaffolds show a modest (<20%) increase in degradation rate in oxidative medium, LTI scaffolds degrade six times faster in oxidative medium. Furthermore, the in vitro rate of degradation of LTI scaffolds in oxidative medium approximates the in vivo rate in rat excisional wounds, and histological sections show macrophages expressing myeloperoxidase at the material surface. While recent preclinical studies have underscored the potential of injectable PEUR scaffolds and delivery systems for tissue regeneration, this promising class of biomaterials has a limited regulatory history. Elucidation of the macrophage-mediated oxidative mechanism by which LTI scaffolds degrade in vivo provides key insights into the ultimate fate of these materials when injected into the body. PMID:20864156

  6. Squalamine lactate for exudative age-related macular degeneration.

    PubMed

    Connolly, Brian; Desai, Avinash; Garcia, Charles A; Thomas, Edgar; Gast, Michael J

    2006-09-01

    Squalamine lactate inhibits angiogenesis by a long-lived, intracellular mechanism of action. The drug is taken up into activated endothelial cells through caveolae, small invaginations in the cellular membrane. Subsequently, the drug binds to and "chaperones" calmodulin to an intracellular membrane compartment and blocks angiogenesis at several levels. A series of basic investigations, preclinical studies, and human clinical trials have begun to establish the proof of concept, efficacy, and safety parameters for use of squalamine lactate as a therapeutic agent for exudative age-related macular degeneration and several types of malignancies. PMID:16935213

  7. Degradation of enoxacin antibiotic by the electro-Fenton process: Optimization, biodegradability improvement and degradation mechanism.

    PubMed

    Annabi, Cyrine; Fourcade, Florence; Soutrel, Isabelle; Geneste, Florence; Floner, Didier; Bellakhal, Nizar; Amrane, Abdeltif

    2016-01-01

    This study aims to investigate the effectiveness of the electro-Fenton process on the removal of a second generation of fluoroquinolone, enoxacin. The electrochemical reactor involved a carbon-felt cathode and a platinum anode. The influence of some experimental parameters, namely the initial enoxacin concentration, the applied current intensity and the Fe(II) amount, was examined. The degradation of the target molecule was accompanied by an increase of the biodegradability, assessed from the BOD5 on COD ratio, which increased from 0 before treatment until 0.5 after 180 min of electrolysis at 50 mg L(-1) initial enoxacin concentration, 0.2 mmol L(-1) Fe(II) concentration and 300 mA applied current intensity. TOC and COD time-courses were also evaluated during electrolysis and reached maximum residual yields of 54% and 43% after 120 min of treatment, respectively. Moreover, a simultaneous generation of inorganic ions (fluorides, ammonium and nitrates) were observed and 3 short chain carboxylic acids (formic, acetic and oxalic acids) were identified and monitored during 180 min of electrolysis. By-products were identified according to UPLC-MS/MS results and a degradation pathway was proposed. PMID:26413803

  8. Age-related changes in the plasticity and toughness of human cortical bone at multiple length-scales

    SciTech Connect

    Zimmermann, Elizabeth A.; Schaible, Eric; Bale, Hrishikesh; Barth, Holly D.; Tang, Simon Y.; Reichert, Peter; Busse, Bjoern; Alliston, Tamara; Ager III, Joel W.; Ritchie, Robert O.

    2011-08-10

    The structure of human cortical bone evolves over multiple length-scales from its basic constituents of collagen and hydroxyapatite at the nanoscale to osteonal structures at nearmillimeter dimensions, which all provide the basis for its mechanical properties. To resist fracture, bone’s toughness is derived intrinsically through plasticity (e.g., fibrillar sliding) at structural-scales typically below a micron and extrinsically (i.e., during crack growth) through mechanisms (e.g., crack deflection/bridging) generated at larger structural-scales. Biological factors such as aging lead to a markedly increased fracture risk, which is often associated with an age-related loss in bone mass (bone quantity). However, we find that age-related structural changes can significantly degrade the fracture resistance (bone quality) over multiple lengthscales. Using in situ small-/wide-angle x-ray scattering/diffraction to characterize sub-micron structural changes and synchrotron x-ray computed tomography and in situ fracture-toughness measurements in the scanning electron microscope to characterize effects at micron-scales, we show how these age-related structural changes at differing size-scales degrade both the intrinsic and extrinsic toughness of bone. Specifically, we attribute the loss in toughness to increased non-enzymatic collagen cross-linking which suppresses plasticity at nanoscale dimensions and to an increased osteonal density which limits the potency of crack-bridging mechanisms at micron-scales. The link between these processes is that the increased stiffness of the cross-linked collagen requires energy to be absorbed by “plastic” deformation at higher structural levels, which occurs by the process of microcracking.

  9. Age-related changes in the plasticity and toughness of human cortical bone at multiple length scales.

    PubMed

    Zimmermann, Elizabeth A; Schaible, Eric; Bale, Hrishikesh; Barth, Holly D; Tang, Simon Y; Reichert, Peter; Busse, Bjoern; Alliston, Tamara; Ager, Joel W; Ritchie, Robert O

    2011-08-30

    The structure of human cortical bone evolves over multiple length scales from its basic constituents of collagen and hydroxyapatite at the nanoscale to osteonal structures at near-millimeter dimensions, which all provide the basis for its mechanical properties. To resist fracture, bone's toughness is derived intrinsically through plasticity (e.g., fibrillar sliding) at structural scales typically below a micrometer and extrinsically (i.e., during crack growth) through mechanisms (e.g., crack deflection/bridging) generated at larger structural scales. Biological factors such as aging lead to a markedly increased fracture risk, which is often associated with an age-related loss in bone mass (bone quantity). However, we find that age-related structural changes can significantly degrade the fracture resistance (bone quality) over multiple length scales. Using in situ small-angle X-ray scattering and wide-angle X-ray diffraction to characterize submicrometer structural changes and synchrotron X-ray computed tomography and in situ fracture-toughness measurements in the scanning electron microscope to characterize effects at micrometer scales, we show how these age-related structural changes at differing size scales degrade both the intrinsic and extrinsic toughness of bone. Specifically, we attribute the loss in toughness to increased nonenzymatic collagen cross-linking, which suppresses plasticity at nanoscale dimensions, and to an increased osteonal density, which limits the potency of crack-bridging mechanisms at micrometer scales. The link between these processes is that the increased stiffness of the cross-linked collagen requires energy to be absorbed by "plastic" deformation at higher structural levels, which occurs by the process of microcracking. PMID:21873221

  10. Ultrasound as a Complementary Tool to Internal Mixers for Investigation of Thermal Mechanical Degradation of PET

    NASA Astrophysics Data System (ADS)

    Sun, Zhigang; Zhao, Lijuan; Tatibouët, Jacques; Jen, Cheng-kuei

    2008-07-01

    An ultrasonically instrumented internal mixer was used to study thermal mechanical degradation of PET samples with different levels of water content and under different processing temperatures and blade speeds. The strength of ultrasound signals reflected from a roller blade of an internal mixer appeared to be more sensitive to PET degradation than the torque measurement means available on the internal mixer, suggesting that ultrasound could provide additional information on material property changes. A main advantage of ultrasonic degradation monitoring over torque measurement is that it could be implemented at various locations of an extruder to obtain localized melt degradation information.

  11. Cathode diffusion and degradation mechanism of polymeric light emitting devices

    NASA Astrophysics Data System (ADS)

    Suh, Min Chul; Chung, Ho Kyoon; Kim, Sang-Yeol; Kwon, Jang Hyuk; Chin, Byung Doo

    2005-09-01

    Rutherford backscattering spectroscopy was applied to investigate the diffusion of metals into polymeric light emitting layer by a continuous device operation. The change of substrate (indium/tin) signal as well as calcium penetration after device operation was conspicuous using pristine light emitting polymer, whereas annealed device above polymer's glass transition temperature indicated almost no migration of calcium. This can be a direct evidence of the molecular conformation and rigidity change of light emitting polymer, which affects the degradation behavior by the metal diffusion into organic thin film.

  12. Long noncoding RNAs in aging and age-related diseases.

    PubMed

    Kour, Sukhleen; Rath, Pramod C

    2016-03-01

    Aging is the universal, intrinsic, genetically-controlled, evolutionarily-conserved and time-dependent intricate biological process characterised by the cumulative decline in the physiological functions and their coordination in an organism after the attainment of adulthood resulting in the imbalance of neurological, immunological and metabolic functions of the body. Various biological processes and mechanisms along with altered levels of mRNAs and proteins have been reported to be involved in the progression of aging. It is one of the major risk factors in the patho-physiology of various diseases and disorders. Recently, the discovery of pervasive transcription of a vast pool of heterogeneous regulatory noncoding RNAs (ncRNAs), including small ncRNAs (sncRNAs) and long ncRNAs (lncRNAs), in the mammalian genome have provided an alternative way to study and explore the missing links in the aging process, its mechanism(s) and related diseases in a whole new dimension. The involvement of small noncoding RNAs in aging and age-related diseases have been extensively studied and recently reviewed. However, lncRNAs, whose function is far less explored in relation to aging, have emerged as a class of major regulators of genomic functions. Here, we have described some examples of known as well as novel lncRNAs that have been implicated in the progression of the aging process and age-related diseases. This may further stimulate research on noncoding RNAs and the aging process. PMID:26655093

  13. Mechanism-based Representative Volume Elements (RVEs) for Predicting Property Degradations in Multiphase Materials

    SciTech Connect

    Xu, Wei; Sun, Xin; Li, Dongsheng; Ryu, Seun; Khaleel, Mohammad A.

    2013-02-01

    Quantitative understanding of the evolving thermal-mechanical properties of a multi-phase material hinges upon the availability of quantitative statistically representative microstructure descriptions. Questions then arise as to whether a two-dimensional (2D) or a three-dimensional (3D) representative volume element (RVE) should be considered as the statistically representative microstructure. Although 3D models are more representative than 2D models in general, they are usually computationally expensive and difficult to be reconstructed. In this paper, we evaluate the accuracy of a 2D RVE in predicting the property degradations induced by different degradation mechanisms with the multiphase solid oxide fuel cell (SOFC) anode material as an example. Both 2D and 3D microstructure RVEs of the anodes are adopted to quantify the effects of two different degradation mechanisms: humidity-induced electrochemical degradation and phosphorus poisoning induced structural degradation. The predictions of the 2D model are then compared with the available experimental measurements and the results from the 3D model. It is found that the 2D model, limited by its inability of reproducing the realistic electrical percolation, is unable to accurately predict the degradation of thermo-electrical properties. On the other hand, for the phosphorus poisoning induced structural degradation, both 2D and 3D microstructures yield similar results, indicating that the 2D model is capable of providing computationally efficient yet accurate results for studying the structural degradation within the anodes.

  14. Mechanisms of Enzymatic Degradation of Amyloid Beta Microfibrils Generating Nanofilaments and Nanospheres Related to Cytotoxicity†

    PubMed Central

    Numata, Keiji; Kaplan, David L.

    2010-01-01

    Amyloid beta (Aβ) fibrils are found in brain tissue of persons with Alzheimer’s disease (AD), where they accumulate as plaques. One way to reduce Aβ accumulation in the brain and potentially treat AD is with Aβ-degrading enzymes such as Neprilysin (NEP) and Insulin-Degrading Enzyme (IDE). However, enzymatic responses and degradation mechanisms of Aβ fibrils (crystalline-state Aβ) have not been investigated, particularly with respect to how to avoid cytotoxicity of the degradation products to neuronal cells. Thus, insight into mechanisms of enzymatic degradation of Aβ fibrils would be instructive as a route to elucidating different structural features related to degradation and to cytotoxicity. We report mechanisms of enzymatic degradation of Aβ with cross-beta structures and show the series of steps involved in the digestion Aβ microfibrils to nanospheres or nanofilaments by protease XIV or alpha-chymotrypsin, respectively. These degradation products, which contained almost the same secondary structures, showed different cytotoxicities, indicating that relationships between nano-assembled structures and cytotoxicity of Aβ peptides are more significant rather than the beta-sheet content. In addition, the enzymatic digestion at the Lys28 loop region linking the two beta sheets in Aβ fibrils is suggested as a key target related to cytotoxicity, a feature that can be selectively targeted based on the choice of protease. PMID:20196618

  15. Age-related macular degeneration: choroidal ischaemia?

    PubMed Central

    Coleman, D Jackson; Silverman, Ronald H; Rondeau, Mark J; Lloyd, Harriet O; Khanifar, Aziz A; Chan, R V Paul

    2013-01-01

    Aim Our aim is to use ultrasound to non-invasively detect differences in choroidal microarchitecture possibly related to ischaemia among normal eyes and those with wet and dry age-related macular degeneration (AMD). Design Prospective case series of subjects with dry AMD, wet AMD and age-matched controls. Methods Digitised 20 MHz B-scan radiofrequency ultrasound data of the region of the macula were segmented to extract the signal from the retina and choroid. This signal was processed by a wavelet transform, and statistical modelling was applied to the wavelet coefficients to examine differences among dry, wet and non-AMD eyes. Receiver operating characteristic (ROC) analysis was used to evaluate a multivariate classifier. Results In the 69 eyes of 52 patients, 18 did not have AMD, 23 had dry AMD and 28 had wet AMD. Multivariate models showed statistically significant differences between groups. Multiclass ROC analysis of the best model showed an excellent volume-under-curve of 0.892±0.17. The classifier is consistent with ischaemia in dry AMD. Conclusions Wavelet augmented ultrasound is sensitive to the organisational elements of choroidal microarchitecture relating to scatter and fluid tissue boundaries such as seen in ischaemia and inflammation, allowing statistically significant differentiation of dry, wet and non-AMD eyes. This study further supports the association of ischaemia with dry AMD and provides a rationale for treating dry AMD with pharmacological agents to increase choroidal perfusion. ClinicalTrials.gov registration NCT00277784. PMID:23740965

  16. Age-related crosslink in skin collagen

    SciTech Connect

    Yamauchi, M.; Mechanic, G.

    1986-05-01

    A stable crosslinking amino acid was isolated from mature bovine skin collagen and its structure was identified as histidinohydroxylysinonorleucine (HHL) using fast atom bombardment mass spectrometry and /sup 1/H, /sup 13/C-NMR. This newly identified crosslink has a linkage between C-2 histidine and C-6 of lysine in the latter's portion of hydroxylysinonorleucine. Quantitative studies using various aged samples of cow and human skin collagen indicated that this acid-heat stable nonreducible compound was the major age-related crosslink. In case of cow skin collagen, for example, during early embryonic development (3 and 5 month old embryos) the content of HHL stayed less than 0.01 residue/mole of collagen, however from the middle of gestation period (7 month old embryo) through the maturation stage it showed rapid increase with age and reached approximately 0.5 residues/mole of collagen in the 3 year old animal. Small increments (up to 0.65 res/mole of collagen) were observed in the 9 year old cow. The amounts of the crosslink unlike pyridinoline do not decrease with aging. Similar patterns were observed in human skin collagen.

  17. A molecular simulation study of chemical degradation and mechanical deformation of hydrated Nafion membranes

    NASA Astrophysics Data System (ADS)

    Xie, Jing; Ban, Shuai; Liu, Bei; Zhou, Hongjun

    2016-01-01

    A combined modeling approach using kinetic Monte Carlo and molecular dynamics simulations is applied to investigate both chemical and mechanical degradation of Nafion membranes on the molecular level. In different hydration conditions, two major degradation reactions are identified to be the main chain unzipping and the side chain scission. The dissolution process of Nafion is evaluated in terms of weight loss, production emission rate and evolution of functional groups. Further, the complicated structural deformation is preliminarily investigated by imposing linear strain on degraded Nafion membrane. Different craze patterns are compared before and after chemical degradation, and the mechanism of crack propagation is proposed. Finally, prospective applications of our modeling approach are addressed for future studies of membrane degradation phenomena under fuel cell operation conditions.

  18. Identification of degradation mechanisms of blue InGaN/GaN laser diodes

    NASA Astrophysics Data System (ADS)

    Wen, P. Y.; Zhang, S. M.; Li, D. Y.; Liu, J. P.; Zhang, L. Q.; Zhou, K.; Feng, M. X.; Tian, A. Q.; Zhang, F.; Gao, X. D.; Zeng, C.; Yang, H.

    2015-10-01

    A comprehensive analysis of the degradation mechanism of blue InGaN/GaN laser diodes (LDs) is carried out by investigating the electrical and optical characteristics. The increase in the leakage current as well as decrease in the slope efficiency is observed. The luminescence properties of the active region at different aging stages are studied by means of cathodoluminescence. Significant degradation of the active region is observed on the room temperature cathodoluminescence while the low temperature cathodoluminescence shows almost no degradation, indicating that the degradation of the LDs is due to generation of low temperature frozen point defects. Furthermore, the generation of the defects follows a kinetic mechanism enhanced by electron-hole non-radiative recombination which explains the acceleration of time degradation in our LDs.

  19. Oxidative degradation of triclosan by potassium permanganate: Kinetics, degradation products, reaction mechanism, and toxicity evaluation.

    PubMed

    Chen, Jing; Qu, Ruijuan; Pan, Xiaoxue; Wang, Zunyao

    2016-10-15

    In this study, we systematically investigated the potential applicability of potassium permanganate for removal of triclosan (TCS) in water treatment. A series of kinetic experiments were carried out to study the influence of various factors, including the pH, oxidant doses, temperature, and presence of typical anions (Cl(-), SO4(2-), NO3(-)), humic acid (HA), and fulvic acid (FA) on triclosan removal. The optimal reaction conditions were: pH = 8.0, [TCS]0:[KMnO4]0 = 1:2.5, and T = 25 °C, where 20 mg/L of TCS could be completely degraded in 120 s. However, the rate of TCS (20 μg/L) oxidation by KMnO4 ([TCS]0:[KMnO4]0 = 1:2.5) was 1.64 × 10(-3) mg L(-1)·h(-1), lower than that at an initial concentration of 20 mg/L (2.24 × 10(3) mg L(-1)·h(-1)). A total of eleven products were detected by liquid chromatography-quadrupole-time-of-flight-mass spectrometry (LC-Q-TOF-MS) analysis, including phenol and its derivatives, benzoquinone, an organic acid, and aldehyde. Two main reaction pathways involving CO bond cleavage (-C(8)O(7)-) and benzene ring opening (in the less chlorinated benzene ring) were proposed, and were further confirmed based on frontier electron density calculations and point charges. Furthermore, the changes in the toxicity of the reaction solution during TCS oxidation by KMnO4 were evaluated by using both the luminescent bacteria Photobacterium phosphoreum and the water flea Daphnia magna. The toxicity of 20 mg/L triclosan to D. magna and P. phosphoreum after 60 min was reduced by 95.2% and 43.0%, respectively. Phenol and 1,4-benzoquinone, the two representative degradation products formed during permanganate oxidation, would yield low concentrations of DBPs (STHMFP, 20.99-278.97 μg/mg; SHAAFP, 7.86 × 10(-4)-45.77 μg/mg) after chlorination and chloramination. Overall, KMnO4 can be used as an effective oxidizing agent for TCS removal in water and wastewater treatment. PMID:27459151

  20. GENETICS OF HUMAN AGE RELATED DISORDERS.

    PubMed

    Srivastava, I; Thukral, N; Hasija, Y

    2015-01-01

    Aging is an inevitable biological phenomenon. The incidence of age related disorders (ARDs) such as cardiovascular diseases, cancer, arthritis, dementia, osteoporosis, diabetes, neurodegenerative diseases increase rapidly with aging. ARDs are becoming a key social and economic trouble for the world's elderly population (above 60 years), which is expected to reach 2 billion by 2050. Advancement in understanding of genetic associations, particularly through genome wide association studies (GWAS), has revealed a substantial contribution of genes to human aging and ARDs. In this review, we have focused on the recent understanding of the extent to which genetic predisposition may influence the aging process. Further analysis of the genetic association studies through pathway analysis several genes associated with multiple ARDs have been highlighted such as apolipoprotein E (APOE), brain-derived neurotrophic factor (BDNF), cadherin 13 (CDH13), CDK5 regulatory subunit associated protein 1 (CDKAL-1), methylenetetrahydrofolate reductase (MTHFR), disrupted in schizophrenia 1 (DISC1), nitric oxide synthase 3 (NOS3), paraoxonase 1 (PON1), indicating that these genes could play a pivotal role in ARD causation. These genes were found to be significantly enriched in Jak-STAT signalling pathway, asthma and allograft rejection. Further, interleukin-6 (IL-6), insulin (INS), vascular endothelial growth factor A (VEGFA), estrogen receptor1 (ESR1), transforming growth factor, beta 1(TGFB1) and calmodulin 1 (CALM1) were found to be highly interconnected in network analysis. We believe that extensive research on the presence of common genetic variants among various ARDs may facilitate scientists to understand the biology behind ARDs causation. PMID:26856084

  1. Degradation and mechanism of the mechanics and durability of reinforced concrete slab in a marine environment

    NASA Astrophysics Data System (ADS)

    Wu, Sheng-xing; Liu, Guan-guo; Bian, Han-bing; Lv, Wei-bo; Jiang, Jian-hua

    2016-04-01

    An experimental research was conducted to determine the corrosion and bearing capacity of a reinforced concrete (RC) slab at different ages in a marine environment. Results show that the development of corrosion-induced cracks on a slab in a marine environment can be divided into three stages according to crack morphology at the bottom of the slab. In the first stage, cracks appear. In the second stage, cracks develop from the edges to the middle of the slab. In the third stage, longitudinal and transverse corrosion-induced cracks coexist. The corrosion ratio of reinforcements nonlinearly increases with the age, and the relationship between the corrosion ratio of the reinforcements and the corrosion-induced crack width of the concrete is established. The flexural capacity of the corroded RC slab nonlinearly decreases with the age, and the model for the bearing capacity factor of the corroded RC slab is established. The mid-span deflection of the corroded RC slab that corresponds to the yield of the reinforcements linearly increases with the increase in corrosion ratio. Finally, the mechanisms of corrosion morphology and the degradation of the mechanical properties of an RC slab in a marine environment are discussed on the basis of the basic theories of steel corrosion in concrete and concrete structure design.

  2. Environment assisted degradation mechanisms in advanced light metals

    NASA Technical Reports Server (NTRS)

    Gangloff, R. P.; Stoner, G. E.; Swanson, R. E.

    1989-01-01

    A multifaceted research program on the performance of advanced light metallic alloys in aggressive aerospace environments, and associated environmental failure mechanisms was initiated. The general goal is to characterize alloy behavior quantitatively and to develop predictive mechanisms for environmental failure modes. Successes in this regard will provide the basis for metallurgical optimization of alloy performance, for chemical control of aggressive environments, and for engineering life prediction with damage tolerance and long term reliability.

  3. Electro-peroxone degradation of diethyl phthalate: Cathode selection, operational parameters, and degradation mechanisms.

    PubMed

    Hou, Meifang; Chu, Yaofei; Li, Xiang; Wang, Huijiao; Yao, Weikun; Yu, Gang; Murayama, Seiichi; Wang, Yujue

    2016-12-01

    This study compares the degradation of diethyl phthalate (DEP) by the electro-peroxone (E-peroxone) process with three different carbon-based cathodes, namely, carbon-polytetrafluorethylene (carbon-PTFE), carbon felt, and reticulated vitreous carbon (RVC). Results show that the three cathodes had different electrocatalytic activity for converting sparged O2 to H2O2, which increased in order of carbon felt, RVC, and carbon-PTFE. The in-situ generated H2O2 then reacts with sparged O3 to yield OH, which can in turn oxidize ozone-refractory DEP toward complete mineralization. In general, satisfactory total organic carbon removal yields (76.4-91.8%) could be obtained after 60min of the E-peroxone treatment with the three carbon-based cathodes, and the highest yield was obtained with the carbon-PTFE cathode due to its highest activity for H2O2 generation. In addition, the carbon-PTFE and carbon felt cathodes exhibited excellent stability over six cycles of the E-peroxone treatment of DEP solutions. Based on the intermediates (e.g., monoethyl phthalate, phthalic acid, phenolics, and carboxylic acids) identified by HPLC-UV, plausible reaction pathways were proposed for DEP mineralization by the E-peroxone process. The results of this study indicate that carbon-based cathodes generally have good electrocatalytic activity and stability for application in extended E-peroxone operations to effectively remove phthalates from water. PMID:26777107

  4. Micro-mechanical model for the tension-stabilized enzymatic degradation of collagen tissues

    NASA Astrophysics Data System (ADS)

    Nguyen, Thao; Ruberti, Jeffery

    We present a study of how the collagen fiber structure influences the enzymatic degradation of collagen tissues. Experiments of collagen fibrils and tissues show that mechanical tension can slow and halt enzymatic degradation. Tissue-level experiments also show that degradation rate is minimum at a stretch level coincident with the onset of strain-stiffening in the stress response. To understand these phenomena, we developed a micro-mechanical model of a fibrous collagen tissue undergoing enzymatic degradation. Collagen fibers are described as sinusoidal elastica beams, and the tissue is described as a distribution of fibers. We assumed that the degradation reaction is inhibited by the axial strain energy of the crimped collagen fibers. The degradation rate law was calibrated to experiments on isolated single fibrils from bovine sclera. The fiber crimp and properties were fit to uniaxial tension tests of tissue strips. The fibril-level kinetic and tissue-level structural parameters were used to predict tissue-level degradation-induced creep rate under a constant applied force. We showed that we could accurately predict the degradation-induce creep rate of the pericardium and cornea once we accounted for differences in the fiber crimp structure and properties.

  5. Enantioselective Degradation Mechanism of Beta-Cypermethrin in Soil From the Perspective of Functional Genes.

    PubMed

    Yang, Zhong-Hua; Ji, Guo-Dong

    2015-12-01

    The behavior and mechanisms of the enantioselective degradation of beta-cypermethrin were studied in soil. The four isomers were degraded at different rates, and the enantiomer fractions of alpha-cypermethrin and theta-cypermethrin exceeded 0.5. Moreover, 3-phenoxybenzoic acid, phenol, and protocatechuic acid were detected; based on the presence of these metabolites, we predicted the degradation pathway and identified the functional genes that are related to this degradation process. We established quantitative relationships between the data on degradation kinetics and functional genes; we found that the quantitative relationships between different enantiomers differed even under the same conditions, and the genes pobA and pytH played key roles in limiting the degradation rate. Data obtained using path analysis revealed that the same gene had different direct and indirect effects on the degradation of different isomers. A mechanism was successfully proposed to explain the selective degradation of chiral compounds based on the perspective of functional genes. PMID:26403376

  6. Biodegradable Poly(Ethylene Glycol) Hydrogels Based on a Self-Elimination Degradation Mechanism

    PubMed Central

    Deshmukh, Manjeet; Singh, Yashveer; Gunaseelan, Simi; Gao, Dayuan; Stein, Stanley; Sinko, Patrick J.

    2010-01-01

    Two vinyl sulfone functionalized crosslinkers were developed for the purpose of preparing degradable poly(ethylene glycol) (PEG) hydrogels (EMXL and GABA-EMXL hydrogels). A self-elimination degradation mechanism in which an N-terminal residue of a glutamine is converted to pyroglutamic acid with subsequent release of diamino PEG (DAP) is proposed. The hydrogels were formed via Michael addition by mixing degradable or nondegradable crosslinkers and copolymer {4% w/v; poly[PEG-alt-poly(mercapto-succinic acid)]} at room temperature in phosphate buffer (PB, pH=7.4). Hydrogel degradation was characterized by assessing diamino PEG release and examining morphological changes as well as the swelling and weight loss ratio under physiological conditions (37 °C). Degradation of EMXL and GABA-EMXL hydrogels occurred by surface erosion (confirmed by SEM). GABA-EMXL degradation was significantly faster (~3-fold) than EMXL; however, the degradation of both hydrogels in mouse plasma was 12-times slower than in PBS. The slower degradation rate in plasma as compared to buffer is consistent with the presence of γ-glutamyltransferase, γ-glutamylcyclotransferase and/or glutaminyl cyclase (QC), which have been shown to suppress pyroglutamic acid formation. The current studies suggest that EMXL and GABA-EMXL hydrogels may have biomedical applications where 1 to 2 week degradation timeframes are optimal. PMID:20561680

  7. Association of Age Related Macular Degeneration and Age Related Hearing Impairment

    PubMed Central

    Ghasemi, Hassan; Pourakbari, Malihe Shahidi; Entezari, Morteza; Yarmohammadi, Mohammad Ebrahim

    2016-01-01

    Purpose: To evaluate the association between age-related macular degeneration (ARMD) and sensory neural hearing impairment (SHI). Methods: In this case-control study, hearing status of 46 consecutive patients with ARMD were compared with 46 age-matched cases without clinical ARMD as a control group. In all patients, retinal involvements were confirmed by clinical examination, fluorescein angiography (FA) and optical coherence tomography (OCT). All participants were examined with an otoscope and underwent audiological tests including pure tone audiometry (PTA), speech reception threshold (SRT), speech discrimination score (SDS), tympanometry, reflex tests and auditory brainstem response (ABR). Results: A significant (P = 0.009) association was present between ARMD, especially with exudative and choroidal neovascularization (CNV) components, and age-related hearing impairment primarily involving high frequencies. Patients had higher SRT and lower SDS against anticipated presbycusis than control subjects. Similar results were detected in exudative, CNV and scar patterns supporting an association between late ARMD with SRT and SDS abnormalities. ABR showed significantly prolonged wave I and IV latency times in ARMD (P = 0.034 and 0.022, respectively). Average latency periods for wave I in geographic atrophy (GA) and CNV, and that for wave IV in drusen patterns of ARMD were significantly higher than controls (P = 0.030, 0.007 and 0.050, respectively). Conclusion: The association between ARMD and age-related SHI may be attributed to common anatomical components such as melanin in these two sensory organs. PMID:27195086

  8. Theoretical analysis of degradation mechanisms in the formation of morphogen gradients

    NASA Astrophysics Data System (ADS)

    Bozorgui, Behnaz; Teimouri, Hamid; Kolomeisky, Anatoly B.

    2015-07-01

    Fundamental biological processes of development of tissues and organs in multicellular organisms are governed by various signaling molecules, which are called morphogens. It is known that spatial and temporal variations in the concentration profiles of signaling molecules, which are frequently referred as morphogen gradients, lead to a cell differentiation via activating specific genes in a concentration-dependent manner. It is widely accepted that the establishment of the morphogen gradients involves multiple biochemical reactions and diffusion processes. One of the critical elements in the formation of morphogen gradients is a degradation of signaling molecules. We develop a new theoretical approach that provides a comprehensive description of the degradation mechanisms. It is based on the idea that the degradation works as an effective potential that drives the signaling molecules away from the source region. Utilizing the method of first-passage processes, the dynamics of the formation of morphogen gradients for various degradation mechanisms is explicitly evaluated. It is found that linear degradation processes lead to a dynamic behavior specified by times to form the morphogen gradients that depend linearly on the distance from the source. This is because the effective potential due to the degradation is quite strong. At the same time, nonlinear degradation mechanisms yield a quadratic scaling in the morphogen gradients formation times since the effective potentials are much weaker. Physical-chemical explanations of these phenomena are presented.

  9. Age-related changes in mouse bone permeability.

    PubMed

    Rodriguez-Florez, Naiara; Oyen, Michelle L; Shefelbine, Sandra J

    2014-03-21

    The determination of lacunar-canalicular permeability is essential for understanding local fluid flow in bone, which may indicate how bone senses changes in the mechanical environment to regulate mechano-adaptation. The estimates of lacunar-canalicular permeability found in the literature vary by up to eight orders of magnitude, and age-related permeability changes have not been measured in non-osteonal mouse bone. The objective of this study is to use a poroelastic approach based on nanoindentation data to characterize lacunar-canalicular permeability in murine bone as a function of age. Nine wild type C57BL/6 mice of different ages (2, 7 and 12 months) were used. Three tibiae from each age group were embedded in epoxy resin, cut in half and indented in the longitudinal direction in the mid-cortex using two spherical fluid indenter tips (R=238 μm and 500 μm). Results suggest that the lacunar-canalicular intrinsic permeability of mouse bone decreases from 2 to 7 months, with no significant changes from 7 to 12 months. The large indenter tip imposed larger contact sizes and sampled larger ranges of permeabilities, particularly for the old bone. This age-related difference in the distribution was not seen for indents with the smaller radius tip. We conclude that the small tip effectively measured lacunar-canalicular permeability, while larger tip indents were influenced by vascular permeability. Exploring the age-related changes in permeability of bone measured by nanoindentation will lead to a better understanding of the role of fluid flow in mechano-transduction. This understanding may help indicate alterations in bone adaptation and remodeling. PMID:24433671

  10. Age-Related Changes in the Misinformation Effect.

    ERIC Educational Resources Information Center

    Sutherland, Rachel; Hayne, Harlene

    2001-01-01

    Two experiments examined relation between age-related changes in retention and age-related changes in the misinformation effect. Found large age-related retention differences when participants were interviewed immediately and after 1 day, but after 6 weeks, differences were minimal. Exposure to misleading information increased commission errors.…

  11. Environment assisted degradation mechanisms in advanced light metals

    NASA Technical Reports Server (NTRS)

    Gangloff, Richard P.; Stoner, Glenn E.; Swanson, Robert E.

    1988-01-01

    The general goals of the research program are to characterize alloy behavior quantitatively and to develop predictive mechanisms for environmental failure modes. Successes in this regard will provide the basis for metallurgical optimization of alloy performance, for chemical control of aggressive environments, and for engineering life prediction with damage tolerance and long term reliability.

  12. Chemical and Mechanical Degradation of Sulfonated Poly(sulfone) Membranes in Vanadium Redox Flow Batteries

    SciTech Connect

    Kim, Soowhan; Tighe, Timothy B.; Schwenzer, Birgit; Yan, Jingling; Zhang, Jianlu; Liu, Jun; Yang, Zhenguo; Hickner, Michael A.

    2011-10-01

    A sulfonated poly(sulfone) (S-Radel{reg_sign}) membrane with high proton conductivity and low vanadium ion diffusion showed high initial performance in a vanadium redox flow battery (VRFB) but suffered damage during charge/discharge cycling. The S-Radel membrane had different degradation behaviors in flow cell cycling and ex-situ vanadium ion immersion tests. The S-Radel membrane immersed in V5+ solution cracked into small pieces, but in the VRFB cell, the membrane underwent internal delamination preferentially on the side of the membrane that faced the positive electrode. A vanadium-rich interface was observed near the membrane surface that experienced delamination and Raman spectroscopic analysis of the surfaces of the membrane indicated a slightly depressed 1026 cm-1 band corresponding to the sulfonate SO2 stretch for the degraded surface. Even though the S-Radel membrane underwent severe mechanical damage during the flow cell cycling, significant chemical degradation was not obvious from the spectroscopic analyses. For the VRFB containing an S-Radel membrane, an increase in membrane resistance caused an abnormal voltage depression during the discharge cycle. The reversible increase in membrane resistance and severe mechanical degradation of the membrane during cycling may be attributed repeated formation and dissolution of particles inside the membrane. The mechanical stresses imposed by the particles coupled with a small amount of chemical degradation of the polymer by V5+, are likely degradation mechanisms of the S-Radel membrane in VRFBs under high state-of-charge conditions.

  13. New amines for CO{sub 2} capture. II. oxidative degradation mechanisms

    SciTech Connect

    Lepaumier, H.; Picq, D.; Carrette, P.L.

    2009-10-15

    This study examines oxidative degradation of 12 ethanolamines and ethylenediamines. They were chosen to establish structure-property relationships: the role of replacement of the alcohol function by one second amine function, amine nature, steric hindrance, and cyclic structure were studied. Degradation of aqueous amine solutions was evaluated at 140{sup o}C under air pressure (2 MPa) in stainless steel reactors for 15 days. At the end of the run, most degradation products were identified by gas chromatography (GC)/mass spectrometry (MS); amounts of remaining amine and its degradation products were determined with the quantitative GC method. Main degradation mechanisms are proposed, and some relationships between structure and chemical stability are given.

  14. Statins for age-related macular degeneration

    PubMed Central

    Gehlbach, Peter; Li, Tianjing; Hatef, Elham

    2016-01-01

    Background Age-related macular degeneration (AMD) is a progressive late onset disorder of the macula affecting central vision. Age-related macular degeneration is the leading cause of blindness in people over 65 years in industrialized countries. Recent epidemiologic, genetic, and pathological evidence has shown AMD shares a number of risk factors with atherosclerosis, leading to the hypothesis that statins may exert protective effects in AMD. Objectives The objective of this review was to examine the effectiveness of statins compared with other treatments, no treatment, or placebo in delaying the onset and progression of AMD. Search methods We searched CENTRAL (which contains the Cochrane Eyes and Vision Group Trials Register) (2014, Issue 6), Ovid MEDLINE, Ovid MEDLINE In-Process and Other Non-Indexed Citations, Ovid MEDLINE Daily, Ovid OLDMEDLINE (January 1946 to June 2014), EMBASE (January 1980 to June 2014), Latin American and Caribbean Health Sciences Literature Database (LILACS) (January 1982 to June 2014), PubMed (January 1946 to June 2014), the metaRegister of Controlled Trials (mRCT) (www.controlled-trials.com), ClinicalTrials.gov (www.clinicaltrials.gov), and the WHO International Clinical Trials Registry Platform (ICTRP) (www.who.int/ictrp/search/en). We did not use any date or language restrictions in the electronic searches for trials. We last searched the electronic databases on 5 June 2014. Selection criteria We included randomized controlled trials (RCTs) that compared statins with other treatments, no treatment, or placebo in participants who were either susceptible to or diagnosed as having early stages of AMD. Data collection and analysis We used standard methodological procedures expected by The Cochrane Collaboration. Two authors independently evaluated the search results against the selection criteria, abstracted data, and assessed risk of bias. We did not perform meta-analysis due to heterogeneity in the interventions and outcomes among the

  15. Current therapeutic developments in atrophic age-related macular degeneration.

    PubMed

    Hanus, Jakub; Zhao, Fangkun; Wang, Shusheng

    2016-01-01

    Age-related macular degeneration (AMD), a degenerative disorder of the central retina, is the leading cause of irreversible blindness in the elderly. The underlying mechanism of the advanced form of dry AMD, also named geographic atrophy (GA) or atrophic AMD, remains unclear. Consequently, no cure is available for dry AMD or GA. The only prevention option currently available is the Age-Related Eye Disease Study (AREDS) formulation, which has been demonstrated to slow down the progression of dry AMD. This review summarises recent advances in therapy for dry AMD and GA. Building on the new understanding of the disease and recent technological breakthroughs, numerous ongoing clinical trials have the goal of meeting the need to cure AMD. Therapeutic agents are being developed to target the key features of the disease, including inhibiting the complement pathway and other inflammatory pathways, reducing oxidative stress and protecting retinal pigment epithelial (RPE) cells, inhibiting lipofuscin and visual cycle, regenerating RPE cells from stem cells and restoring choroidal blood flow. Some of these therapeutic options, especially the stem cell-based therapy, hold great promise, which brings great hope for this devastating blinding disease. PMID:26553922

  16. Age-related Cardiac Disease Model of Drosophila

    PubMed Central

    Ocorr, Karen; Akasaka, Takeshi; Bodmer, Rolf

    2007-01-01

    We have begun to study the genetic basis of deterioration of cardiac function in the fruit fly Drosophila melanogaster as an age-related cardiac disease model. For this purpose we have developed heart function assays in Drosophila and found that the fly's cardiac performance, as that of the human heart, deteriorates with age: aging fruit flies exhibit a progressive increase in electrical pacing-induced heart failure as well as in arrhythmias. The insulin receptor and associated pathways have a dramatic and heart-autonomous influence on age-related cardiac performance in flies, suggestive of potentially similar mechanisms in regulating cardiac aging in vertebrates. Compromised KCNQ and KATP ion channel functions also seem to contribute to the decline in heart performance in aging flies, suggesting that the corresponding vertebrate gene functions may similarly decline with age, in addition to their conserved role in protecting against arrhythmias and hypoxia/ischemia, respectively. The fly heart is thus emerging as a promising genetic model for studying the age-dependent decline in organ function. PMID:17125816

  17. Current Therapeutic Development for Atrophic Age-related Macular Degeneration

    PubMed Central

    Hanus, Jakub; Zhao, Fangkun; Wang, Shusheng

    2016-01-01

    Age-related macular degeneration (AMD), a degenerative disorder of the central retina, is the leading cause of irreversible blindness in the elderly. The underlying mechanism of the advanced form of dry AMD, also named geographic atrophy (GA) or atrophic AMD, remains unclear. Consequently, no cure is available for dry AMD or GA. The only prevention option currently available is the Age Related Eye Disease Study (AREDS) formulation which has been demonstrated to slow down the progression of dry AMD. This review summarizes recent advances in therapy for dry AMD and GA. Building on the new understanding of the disease and recent technological breakthroughs, numerous ongoing clinical trials have the goal of meeting the need to cure AMD. Therapeutic agents are being developed to target the key features of the disease, including inhibiting the complement pathway and other inflammatory pathways, reducing oxidative stress and protecting retinal pigment epithelial (RPE) cells, inhibiting lipofuscin and visual cycle, regenerating RPE cells from stem cells and restoring choroidal blood flow. Some of these therapeutic options, especially the stem-cell based therapy, hold great promise, which brings great hope for this devastating blinding disease. PMID:26553922

  18. Correlation of Chemical and Mechanical Property Changes During Oxidative Degradation of Neoprene

    SciTech Connect

    Celina, M.; Wise, J.; Ottesen, D.K.; Gillen, K.T.; Clough, R.L.

    1999-07-01

    The thermal degradation of a commercial, stabilized, unfilled neoprene (chloroprene) rubber was investigated at temperatures up to 140 C. The degradation of this material is dominated by oxidation rather than dehydrochlorination. Important heterogeneous oxidation effects were observed at the various temperatures investigated using infrared micro-spectroscopy and modulus profiling. Intensive degradation-related spectral changes in the IR occurred in the conjugated carbonyl and hydroxyl regions. Quantitative analysis revealed some differences in the development of the IR oxidation profiles, particularly towards the sample surface. These chemical degradation profiles were compared with modulus profiles (mechanical properties). It is concluded that the profile development is fundamentally described by a diffusion-limited autoxidation mechanism. Oxygen consumption measurements showed that the oxidation rates display non-Arrhenius behavior (curvature) at low temperatures. The current results, when compared to those of a previously studied, clay-filled commercial neoprene formulation, indicate that the clay filler acts as an antioxidant, but only at low temperatures.

  19. Critical analysis on degradation mechanism of dye-sensitized solar cells

    NASA Astrophysics Data System (ADS)

    Mohamad Shahimin, Mukhzeer; Suhaimi, Suriati; Abd Wahid, Mohd Halim; Retnasamy, Vithyacharan; Ahmad Hambali, Nor Azura Malini; Reshak, Ali Hussain

    2015-09-01

    This paper reports on a précis of degradation mechanism for dye-sensitized solar cell (DSSCs). The review indicates progress in the understanding of degradation mechanism, in particular, the large improvement in the analysis of the materials used in DSSCs. The paper discussed on the stability issues of the dye, advancement of the photoelectrode film lifetime, changes in the electrolyte components and degradation analysis of the counter electrode. The photoelectrochemical parameters were evaluated in view of the possible degradation routes via open circuit voltage (Voc), short circuit current (Isc), fill factor (FF) and overall conversion efficiency (η) from the current-voltage curve. This analysis covers several types of materials that have paved the way for better-performing solar cells and directly influenced the stability and reliability of DSSCs. The new research trend together with the previous research has been highlighted to examine the key challenges faced in developing the ultimate DSSCs.

  20. On the Degradation Mechanism of Low-Voltage Underground Cable with Poly(Vinyl Chloride) Insulation

    NASA Astrophysics Data System (ADS)

    Tawancy, H. M.; Hassan, M.

    2016-06-01

    A study has been undertaken to determine the degradation mechanism leading to localized short-circuit failures of an underground low-voltage cable with PVC insulation. It is shown that that the insulation of outer sheath and conductor cores has been cracked by thermal degradation involving dehydrochlorination, oxidation, and loss of plasticizers leading to current leakage between the cores. Most evidence points out that overheating due to poor connection of copper wires as well as a chemically active soil has caused the observed degradation.

  1. Microscopic Degradation Mechanisms in Silicon Photovoltaic Module under Long-Term Environmental Exposure

    NASA Astrophysics Data System (ADS)

    Matsuda, Keiko; Watanabe, Takeshi; Sakaguchi, Koichi; Yoshikawa, Masanobu; Doi, Takuya; Masuda, Atsushi

    2012-10-01

    We used several analytical methods to identify the mechanism underlying the performance degradation in a photovoltaic (PV) module subjected to long-term (10 years) field exposure. Cloudy visual defects in this module were caused by delamination between the poly(ethylene vinyl acetate) (EVA) and antireflection coating films on the Si substrate. The delamination was considered to be caused by the formation of a segregation layer and oxidative degradation of EVA. Furthermore, it was found that sodium ions diffused from the superstrate glass into the EVA film and Si cell. We confirm that diffusion of sodium ions caused the degradation of Si cells and the superstrate glass of this module.

  2. Degradation of oxcarbazepine by UV-activated persulfate oxidation: kinetics, mechanisms, and pathways.

    PubMed

    Bu, Lingjun; Zhou, Shiqing; Shi, Zhou; Deng, Lin; Li, Guangchao; Yi, Qihang; Gao, Naiyun

    2016-02-01

    The degradation kinetics and mechanism of the antiepileptic drug oxcarbazepine (OXC) by UV-activated persulfate oxidation were investigated in this study. Results showed that UV/persulfate (UV/PS) process appeared to be more effective in degrading OXC than UV or PS alone. The OXC degradation exhibited a pseudo-first order kinetics pattern and the degradation rate constants (k obs) were affected by initial OXC concentration, PS dosage, initial pH, and humic acid concentration to different degrees. It was found that low initial OXC concentration, high persulfate dosage, and initial pH enhanced the OXC degradation. Additionally, the presence of humic acid in the solution could greatly inhibit the degradation of OXC. Moreover, hydroxyl radical (OH•) and sulfate radical (SO4 (-)••) were identified to be responsible for OXC degradation and SO4 (-)• made the predominant contribution in this study. Finally, major intermediate products were identified and a preliminary degradation pathway was proposed. Results demonstrated that UV/PS system is a potential technology to control the water pollution caused by emerging contaminants such as OXC. PMID:26452660

  3. Reaction and degradation mechanism in all-solid-state lithium-air batteries.

    PubMed

    Kitaura, Hirokazu; Zhou, Haoshen

    2015-12-25

    The reaction and degradation mechanism in all-solid-state Li-air batteries was investigated to improve the cycling performance. It is suggested that Li2O2 is first produced by the H2O-mediated electrochemical reactions during discharging and Li2CO3 is produced by the following chemical reactions. Disruption of the CNTs and residual discharge products, which cause the capacity degradation during cycling, were observed. PMID:26478218

  4. Understanding Irreversible Degradation of Nb3Sn Wires with Fundamental Fracture Mechanics

    SciTech Connect

    Zhai, Yuhu; Calzolaio, Ciro; Senatore, Carmine

    2014-08-01

    Irreversible performance degradation of advanced Nb3Sn superconducting wires subjected to transverse or axial mechanical loading is a critical issue for the design of large-scale fusion and accelerator magnets such as ITER and LHC. Recent SULTAN tests indicate that most cable-in-conduit conductors for ITER coils made of Nb3Sn wires processed by various fabrication techniques show similar performance degradation under cyclic loading. The irreversible degradation due to filament fracture and local strain accumulation in Nb3Sn wires cannot be described by the existing strand scaling law. Fracture mechanic modeling combined with X-ray diffraction imaging of filament micro-crack formation inside the wires under mechanical loading may reveal exciting insights to the wire degradation mechanisms. We apply fundamental fracture mechanics with a singularity approach to study influence of wire filament microstructure of initial void size and distribution to local stress concentration and potential crack propagation. We report impact of the scale and density of the void structure on stress concentration in the composite wire materials for crack initiation. These initial defects result in an irreversible degradation of the critical current beyond certain applied stress. We also discuss options to minimize stress concentration in the design of the material microstructure for enhanced wire performance for future applications.

  5. Kinetics and mechanism of thermal degradation of pentose- and hexose-based carbohydrate polymers.

    PubMed

    Akbar, Jamshed; Iqbal, Mohammad S; Massey, Shazma; Masih, Rashid

    2012-10-15

    This work aims at study of thermal degradation kinetics and mechanism of pentose- and hexose-based carbohydrate polymers isolated from Plantago ovata (PO), Salvia aegyptiaca (SA) and Ocimum basilicum (OB). The analysis was performed by isoconversional method. The materials exhibited mainly two-stage degradation. The weight loss at ambient-115°C characterized by low activation energy corresponds to loss of moisture. The kinetic triplets consisting of E, A and g(α) model of the materials were determined. The major degradation stage represents a loss of high boiling volatile components. This stage is exothermic in nature. Above 340°C complete degradation takes place leaving a residue of 10-15%. The master plots of g(α) function clearly differentiated the degradation mechanism of hexose-based OB and SA polymers and pentose-based PO polymer. The pentose-based carbohydrate polymer showed D(4) type and the hexose-based polymers showed A(4) type degradation mechanism. PMID:22939355

  6. Mechanism of anaerobic degradation of triethanolamine by a homoacetogenic bacterium

    SciTech Connect

    Speranza, Giovanna . E-mail: giovanna.speranza@unimi.it; Morelli, Carlo F.; Cairoli, Paola; Mueller, Britta; Schink, Bernhard

    2006-10-20

    Triethanolamine (TEA) is converted into acetate and ammonia by a strictly anaerobic, gram-positive Acetobacterium strain LuTria3. Fermentation experiments with resting cell suspensions and specifically deuterated substrates indicate that in the acetate molecule the carboxylate and the methyl groups correspond to the alcoholic function and to its adjacent methylene group, respectively, of the 2-hydroxyethyl unit of TEA. A 1,2 shift of a hydrogen (deuterium) atom from -CH{sub 2} -O- to =N-CH{sub 2} - without exchange with the medium was observed. This fact gives evidence that a radical mechanism occurs involving the enzyme and/or coenzyme molecule as a hydrogen carrier. Such a biodegradation appears analogous to the conversion of 2-phenoxyethanol into acetate mediated by another strain of the anaerobic homoacetogenic bacterium Acetobacterium.

  7. Mechanical degradation of fuel cell membranes under fatigue fracture tests

    NASA Astrophysics Data System (ADS)

    Khorasany, Ramin M. H.; Sadeghi Alavijeh, Alireza; Kjeang, Erik; Wang, G. G.; Rajapakse, R. K. N. D.

    2015-01-01

    The effects of cyclic stresses on the fatigue and mechanical stability of perfluorosulfonic acid (PFSA) membranes are experimentally investigated under standard fuel cell conditions. The experiments are conducted ex-situ by subjecting membrane specimens to cyclic uniaxial tension at controlled temperature and relative humidity. The fatigue lifetime is measured in terms of the number of cycles until ultimate fracture. The results indicate that the membrane fatigue lifetime is a strong function of the applied stress, temperature, and relative humidity. The fatigue life increases exponentially with reduced stresses in all cases. The effect of temperature is found to be more significant than that of humidity, with reduced fatigue life at high temperatures. The maximum membrane strain at fracture is determined to decrease exponentially with increasing membrane lifetime. At a given fatigue life, a membrane exposed to fuel cell conditions is shown to accommodate more plastic strain before fracture than one exposed to room conditions. Overall, the proposed ex-situ membrane fatigue experiment can be utilized to benchmark the fatigue lifetime of new materials in a fraction of the time and cost associated with conventional in-situ accelerated stress testing methods.

  8. Age-related priming effects in social judgments.

    PubMed

    Hess, T M; McGee, K A; Woodburn, S M; Bolstad, C A

    1998-03-01

    Two experiments investigated adult age differences in the impact of previously activated (and thus easily accessible) trait-related information on judgments about people. The authors hypothesized that age-related declines in the efficiency of controlled processing mechanisms during adulthood would be associated with increased susceptibility to judgment biases associated with such information. In each study, different-aged adults made impression judgments about a target, and assimilation of these judgments to trait constructs activated in a previous, unrelated task were examined. Consistent with the authors' hypotheses, older adults were likely to form impressions that were biased toward the primed trait constructs. In contrast, younger adults exhibited greater awareness of the primed information and were more likely to correct for its perceived influence, especially when distinctive contextual cues regarding the source of the primes were available. PMID:9533195

  9. Modulation of cell death in age-related diseases.

    PubMed

    Tezil, Tugsan; Basaga, Huveyda

    2014-01-01

    Aging is a stage of life of all living organisms. According to the free-radical theory, aging cells gradually become unable to maintain cellular homeostasis due to the adverse effects of reactive oxygen species (ROS). ROS can cause irreversible DNA mutations, protein and lipid damage which are increasingly accumulated in the course of time if cells could not overcome these effects by the antioxidant defence system. Accrued damaged molecules in cells may either induce cellular death or contribute to develop various pathologies. Hence, programmed cell death mechanisms, apoptosis and autophagy, play a vital role in the aging process. Although they are strictly controlled by various interconnected signalling pathways, alterations in their regulations may contribute to severe pathologies including cancer, Alzheimer's and Parkinson's diseases. In this review, we summarized our current understanding and hypotheses regarding oxidative stress and age-related dysregulation of cell death signalling pathways. PMID:24079770

  10. A Revised Hemodynamic Theory of Age-Related Macular Degeneration.

    PubMed

    Gelfand, Bradley D; Ambati, Jayakrishna

    2016-08-01

    Age-related macular degeneration (AMD) afflicts one out of every 40 individuals worldwide, causing irreversible central blindness in millions. The transformation of various tissue layers within the macula in the retina has led to competing conceptual models of the molecular pathways, cell types, and tissues responsible for the onset and progression of AMD. A model that has persisted for over 6 decades is the hemodynamic, or vascular theory of AMD progression, which states that vascular dysfunction of the choroid underlies AMD pathogenesis. Here, we re-evaluate this hypothesis in light of recent advances on molecular, anatomic, and hemodynamic changes underlying choroidal dysfunction in AMD. We propose an updated, detailed model of hemodynamic dysfunction as a mechanism of AMD development and progression. PMID:27423265

  11. Mechanical Impact Induces Cartilage Degradation via Mitogen Activated Protein Kinases

    PubMed Central

    Ding, Lei; Heying, Emily; Nicholson, Nathan; Stroud, Nicolas J.; Homandberg, Gene A.; Guo, Danping; Buckwalter, Joseph A.; Martin, James A.

    2010-01-01

    Objective To determine the activation of MAP kinases in and around cartilage subjected to mechanical damage and to determine the effects of their inhibitors on impaction induced chondrocyte death and cartilage degeneration. Design The phosphorylation of MAP kinases was examined with confocal microscopy and immunoblotting. The effects of MAP kinase inhibitors on impaction-induced chondrocyte death and proteoglycan loss were determined with fluorescent microscopy and DMMB assay. The expression of catabolic genes at mRNA levels was examined with quantitative real time PCR. Results Early p38 activation was detected at 20 min and 1 hr post-impaction. At 24 hr, enhanced phosphorylation of p38 and ERK1/2 was visualized in chondrocytes from in and around impact sites. The phosphorylation of p38 was increased by 3.0-fold in impact sites and 3.3-fold in adjacent cartilage. The phosphorylation of ERK-1 was increased by 5.8-fold in impact zone and 5.4-fold in adjacent cartilage; the phosphorylation of ERK-2 increased by 4.0-fold in impacted zone and 3.6-fold in adjacent cartilage. Furthermore, the blocking of p38 pathway did not inhibit impaction-induced ERK activation. The inhibition of p38 or ERK pathway significantly reduced injury-related chondrocyte death and proteoglycan losses. Quantative Real-time PCR analysis revealed that blunt impaction significantly up-regulated MMP-13, TNF-α, and ADAMTS-5 expression. Conclusion These findings implicate p38 and ERK MAPKs in the post injury spread of cartilage degeneration and suggest that the risk of PTOA following joint trauma could be decreased by blocking their activities, which might be involved in up-regulating expressions of MMP-13, ADAMTS-5, and TNF-α. PMID:20813194

  12. Performance degradation mechanisms and modes in terrestrial photovoltaic arrays and technology for their diagnosis

    NASA Technical Reports Server (NTRS)

    Noel, G. T.; Sliemers, F. A.; Derringer, G. C.; Wood, V. E.; Wilkes, K. E.; Gaines, G. B.; Carmichael, D. C.

    1978-01-01

    Accelerated life-prediction test methodologies have been developed for the validation of a 20-year service life for low-cost photovoltaic arrays. Array failure modes, relevant materials property changes, and primary degradation mechanisms are discussed as a prerequisite to identifying suitable measurement techniques and instruments. Measurements must provide sufficient confidence to permit selection among alternative designs and materials and to stimulate widespread deployment of such arrays. Furthermore, the diversity of candidate materials and designs, and the variety of potential environmental stress combinations, degradation mechanisms and failure modes require that combinations of measurement techniques be identified which are suitable for the characterization of various encapsulation system-cell structure-environment combinations.

  13. Aging Effects and Estimating Degradation Mechanisms of Thermally Upgraded Paper in Mineral Oil

    NASA Astrophysics Data System (ADS)

    Miyagi, Katsunori; Oe, Etsuo; Yamagata, Naoki

    The life of a transformer is limited to the deterioration of its solid insulation. Winding conductors and other solid insulation materials in oil-immersed transformers have been insulated using cellulose products. For many years, manufacturers have met the needs of special applications by designing transformers using thermally upgraded materials to achieve lighter weight, higher power density and increased life. Recently, the effect of thermally upgraded insulation on diagnostic techniques such as gas-in oil analysis, and their indication of insulation degradation have been reviewed. This paper describes evaluations of the thermal degradation characteristics and decomposition reactions in mineral transformer oil of amine-impregnated thermally upgraded paper insulation. The thermal resistance of the thermally upgraded paper is evaluated by comparison with Kraft paper insulation. Further, aging degradation mechanisms of decompositional degradation of the thermally upgraded paper due to aging in mineral transformer oil are proposed.

  14. Light-Induced Ambient Degradation of Few-Layer Black Phosphorus: Mechanism and Protection.

    PubMed

    Zhou, Qionghua; Chen, Qian; Tong, Yilong; Wang, Jinlan

    2016-09-12

    The environmental instability of single- or few-layer black phosphorus (BP) has become a major hurdle for BP-based devices. The degradation mechanism remains unclear and finding ways to protect BP from degradation is still highly challenging. Based on ab initio electronic structure calculations and molecular dynamics simulations, a three-step picture on the ambient degradation of BP is provided: generation of superoxide under light, dissociation of the superoxide, and eventual breakdown under the action of water. The well-matched band gap and band-edge positions for the redox potential accelerates the degradation of thinner BP. Furthermore, it was found that the formation of P-O-P bonds can greatly stabilize the BP framework. A possible protection strategy using a fully oxidized BP layer as the native capping is thus proposed. Such a fully oxidization layer can resist corrosion from water and leave the BP underneath intact with simultaneous high hole mobility. PMID:27529543

  15. Age-related hypoxia in CNS pathology.

    PubMed

    Bădescu, George Mihai; Fîlfan, Mădălina; Ciobanu, Ovidiu; Dumbravă, DănuŢ Adrian; Popa-Wagner, Aurel

    2016-01-01

    Although neuropathological conditions differ in the etiology of the inflammatory response, cellular and molecular mechanisms of neuroinflammation are probably similar in aging, hypertension, depression and cognitive impairment. Moreover, a number of common risk factors such as obesity, hypertension, diabetes and atherosclerosis are increasingly understood to act as "silent contributors" to neuroinflammation and can underlie the development of disorders such as cerebral small vessel disease (cSVD) and subsequent dementia. On the other hand, acute neuroinflammation, such as in response to traumatic or cerebral ischemia, aggravates the acute damage and can lead to a number of pathological such as depression, post-stroke dementia and potentially neurodegeneration. All of those sequelae impair recovery and most of them provide the ground for further cerebrovascular events and a vicious cycle develops. Therefore, understanding the mechanisms associated with vascular dementia, stroke and related complications is of paramount importance in improving current preventive and therapeutic interventions. Likewise, understanding of molecular factors and pathways associated with neuroinflammation will eventually enable the discovery and implementation of new diagnostic and therapeutic strategies indicated in a wide range of neurological conditions. PMID:27151686

  16. Age-Related Degeneration of the Egg-Laying System Promotes Matricidal Hatching in Caenorhabditis elegans

    PubMed Central

    Pickett, Christopher L.; Kornfeld, Kerry

    2014-01-01

    Summary The identification and characterization of age-related degenerative changes is a critical goal because it can elucidate mechanisms of aging biology and contribute to understanding interventions that promote longevity. Here we document a novel, age-related degenerative change in C. elegans hermaphrodites, an important model system for the genetic analysis of longevity. Matricidal hatching—intra-uterine hatching of progeny that causes maternal death—displayed an age-related increase in frequency and affected ∼70% of mated, wild-type hermaphrodites. The timing and incidence of matricidal hatching were largely independent of the levels of early and total progeny production and the duration of male exposure. Thus, matricidal hatching appears to reflect intrinsic age-related degeneration of the egg-laying system rather than use-dependent damage accumulation. Consistent with this model, mutations that extend longevity by causing dietary restriction significantly delayed matricidal hatching, indicating age-related degeneration of the egg-laying system is controlled by nutrient availability. To identify the underlying tissue defect, we analyzed serotonin signaling that triggers vulval muscle contractions. Mated hermaphrodites displayed an age-related decline in the ability to lay eggs in response to exogenous serotonin, indicating that vulval muscles and/or a further downstream function that is necessary for egg-laying degenerate in an age-related manner. By characterizing a new, age-related degenerative event displayed by C. elegans hermaphrodites, these studies contribute to understanding a frequent cause of death in mated hermaphrodites and establish a model of age-related reproductive complications that may be relevant to the birthing process in other animals such as humans. PMID:23551912

  17. Mechanism of Polysulfone-Based Anion Exchange Membranes Degradation in Vanadium Flow Battery.

    PubMed

    Yuan, Zhizhang; Li, Xianfeng; Zhao, Yuyue; Zhang, Huamin

    2015-09-01

    The stability of hydrocarbon ion exchange membranes is one of the critical issues for a flow battery. However, the degradation mechanism of ion exchange membranes has been rarely investigated especially for anion exchange membranes. Here, the degradation mechanism of polysulfone based anion exchange membranes, carrying pyridine ion exchange groups, under vanadium flow battery (VFB) medium was investigated in detail. We find that sp(2) hybrid orbital interactions between pyridinic-nitrogen in 4,4'-bipyridine and benzylic carbon disrupt the charge state balance of pristine chloromethylated polysulfone. This difference in electronegativity inversely induces an electrophilic carbon center in the benzene ring, which can be attacked by the lone pair electron on the vanadium(V) oxygen species, further leading to the degradation of polymer backbone, while leaving the 4,4'-bipyridine ion exchange groups stable. This work represents a step toward design and construction of alternative type of chemically stable hydrocarbon ion exchange membranes for VFB. PMID:26284752

  18. Diversity, Structures, and Collagen-Degrading Mechanisms of Bacterial Collagenolytic Proteases

    PubMed Central

    Zhang, Yu-Zhong; Ran, Li-Yuan; Li, Chun-Yang

    2015-01-01

    Bacterial collagenolytic proteases are important because of their essential role in global collagen degradation and because of their virulence in some human bacterial infections. Bacterial collagenolytic proteases include some metalloproteases of the M9 family from Clostridium or Vibrio strains, some serine proteases distributed in the S1, S8, and S53 families, and members of the U32 family. In recent years, there has been remarkable progress in discovering new bacterial collagenolytic proteases and in investigating the collagen-degrading mechanisms of bacterial collagenolytic proteases. This review provides comprehensive insight into bacterial collagenolytic proteases, especially focusing on the structures and collagen-degrading mechanisms of representative bacterial collagenolytic proteases in each family. The roles of bacterial collagenolytic proteases in human diseases and global nitrogen cycling, together with the biotechnological and medical applications for these proteases, are also briefly discussed. PMID:26150451

  19. A method to define degradation mechanisms and failure rates for piping

    SciTech Connect

    Gamble, R.M.; Gosselin, S.R.

    1996-12-01

    This paper describes a process currently being employed to develop an easy to use procedure for identifying degradation mechanisms and computing failure rates for piping. The procedure includes guidelines to identify degradation mechanisms that may be present in piping systems. The identified mechanisms along with other system or segment specific features of the piping determine the piping failure rate. Implementation of this procedure requires a data or knowledge base that reflects the service and operational conditions that affect piping reliability and availability. This procedure is being developed for use by plant engineers, and will not require expertise in probability, stress, or fracture mechanics analyses. The method can be used to provide input for performing plant safety assessments and defining risk based inspection programs.

  20. MECHANISMS OF THERMOPHILIC SURVIVAL, DEGRADATION BY THERMOPHILICS AND OPTIMIZATION OF THERMOPHILIC BACTERIA FOR BIODEGRADATION

    EPA Science Inventory

    We have developed a consortium of thermophilic methanotrophic bacteria from Yellowstone National Park that degrades TCE by the use of methyl monooxygenase. We are going to isolate the thermophiles in patent 5,858,763,determine their mechanisms of surviving extreme temperatures, d...

  1. ADIPIC ACID DEGRADATION MECHANISM IN AQUEOUS FGD (FLUE GAS DESULFURIZATION) SYSTEMS

    EPA Science Inventory

    The report gives results of a field and laboratory study of the adipic acid degradation mechanism in aqueous flue gas desulfurization (FGD) systems. (Adding adipic acid to limestone-based, SO2 wet scrubbers increases SO2 removal and limestone utilization. However, as much as 80% ...

  2. Proinflammatory cytokines, aging, and age-related diseases.

    PubMed

    Michaud, Martin; Balardy, Laurent; Moulis, Guillaume; Gaudin, Clement; Peyrot, Caroline; Vellas, Bruno; Cesari, Matteo; Nourhashemi, Fati

    2013-12-01

    Inflammation is a physiological process that repairs tissues in response to endogenous or exogenous aggressions. Nevertheless, a chronic state of inflammation may have detrimental consequences. Aging is associated with increased levels of circulating cytokines and proinflammatory markers. Aged-related changes in the immune system, known as immunosenescence, and increased secretion of cytokines by adipose tissue, represent the major causes of chronic inflammation. This phenomenon is known as "inflamm-aging." High levels of interleukin (IL)-6, IL-1, tumor necrosis factor-α, and C-reactive protein are associated in the older subject with increased risk of morbidity and mortality. In particular, cohort studies have indicated TNF-α and IL-6 levels as markers of frailty. The low-grade inflammation characterizing the aging process notably concurs at the pathophysiological mechanisms underlying sarcopenia. In addition, proinflammatory cytokines (through a variety of mechanisms, such as platelet activation and endothelial activation) may play a major role in the risk of cardiovascular events. Dysregulation of the inflammatory pathway may also affect the central nervous system and be involved in the pathophysiological mechanisms of neurodegenerative disorders (eg, Alzheimer disease).The aim of the present review was to summarize different targets of the activity of proinflammatory cytokines implicated in the risk of pathological aging. PMID:23792036

  3. Mechanisms of Methylene Blue Degradation in Three-dimensionally Integrated Micro-solution Plasma

    NASA Astrophysics Data System (ADS)

    Nomura, Ayano; Hayashi, Yui; Tanaka, Kenji; Shirafuji, Tatsuru; Goto, Motonobu

    2015-09-01

    Plasma in aqueous solution has attracted much attention because they are expected to have possibilities to solve water-related environmental issues. In such application-oriented researches, degradation of methylene blue (MB) or other organic dyes has been widely used for investigating the effects of the plasma treatment on the water with organic contaminants. However, there are few reports on the detailed analysis of the products after the plasma treatment of MB aqueous solution for understanding mechanisms of the degradation processes. We have hence analyzed our degradation products using matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectrometry. We have performed the MB degradation in three-dimensionally integrated micro-solution plasma, which has shown 16-fold higher performance in MB degradation than conventional solution plasma. The results of MALDI-TOF mass spectrometry have indicated the formation of sulfoxides in the first stage of the degradation. Then, the methyl groups on the sulfoxides are partially oxidized. The sulfoxides are separated to form two benzene derivatives after that. Finally, weak functional groups are removed from the benzene derivatives.

  4. Ubiquitin-proteasome-mediated degradation of keratin intermediate filaments in mechanically stimulated A549 cells.

    PubMed

    Jaitovich, Ariel; Mehta, Semil; Na, Ni; Ciechanover, Aaron; Goldman, Robert D; Ridge, Karen M

    2008-09-12

    We previously reported that shear stress induces phosphorylation and disassembly of keratin intermediate filaments (IFs). Shear stress also induces a time- and strain-dependent degradation of keratin IFs, and the current study examines the mechanisms involved in degradation of keratin proteins in human A549 cells exposed to 0-24 h of shear stress (7.5-30 dynes/cm(2)). Ubiquitin was found to be covalently associated with keratin proteins immunoprecipitated from shear-stressed cells, and pretreatment with the proteasomal inhibitor MG132 prevented the degradation of the keratin IF network. Importantly, phosphorylation of K8 Ser-73 is required for the shear stress-mediated ubiquitination, disassembly, and degradation of the keratin IF network. Immunofluorescence microscopy revealed that shear stress caused the thin array of keratin fibrils observed in control cells to be reorganized into a perinuclear aggregate, known as an aggresome, and that ubiquitin was also associated with this structure. Finally, the E2 enzymes, UbcH5b, -c, and Ubc3, but not E2-25K are required for the shear stress-mediated ubiquitin-proteasomal degradation of keratin proteins. These data suggest that shear stress promotes the disassembly and degradation of the keratin IF network via phosphorylation and the ubiquitin-proteasome pathway. PMID:18617517

  5. Insights into the Mechanism and Kinetics of Thermo-Oxidative Degradation of HFPE High Performance Polymer.

    PubMed

    Kunnikuruvan, Sooraj; Parandekar, Priya V; Prakash, Om; Tsotsis, Thomas K; Nair, Nisanth N

    2016-06-01

    The growing requisite for materials having high thermo-oxidative stability makes the design and development of high performance materials an active area of research. Fluorination of the polymer backbone is a widely applied strategy to improve various properties of the polymer, most importantly the thermo-oxidative stability. Many of these fluorinated polymers are known to have thermo-oxidative stability up to 700 K. However, for space and aerospace applications, it is important to improve its thermo-oxidative stability beyond 700 K. Molecular-level details of the thermo-oxidative degradation of such polymers can provide vital information to improve the polymer. In this spirit, we have applied quantum mechanical and microkinetic analysis to scrutinize the mechanism and kinetics of the thermo-oxidative degradation of a fluorinated polymer with phenylethenyl end-cap, HFPE. This study gives an insight into the thermo-oxidative degradation of HFPE and explains most of the experimental observations on the thermo-oxidative degradation of this polymer. Thermolysis of C-CF3 bond in the dianhydride component (6FDA) of HFPE is found to be the rate-determining step of the degradation. Reaction pathways that are responsible for the experimentally observed weight loss of the polymer is also scrutinized. On the basis of these results, we propose a modification of HFPE polymer to improve its thermo-oxidative stability. PMID:27187246

  6. The effect of nucleus pulposus crosslinking and glycosaminoglycan degradation on disc mechanical function.

    PubMed

    Yerramalli, C S; Chou, A I; Miller, G J; Nicoll, S B; Chin, K R; Elliott, D M

    2007-01-01

    Altered mechanical loading, secondary to biochemical changes in the nucleus pulposus, is a potential mechanism in disc degeneration. An understanding of the role of this altered mechanical loading is only possible by separating the mechanical and biological effects of early nucleus pulposus changes. The objective of this study was to quantify the mechanical effect of decreased glycosaminoglycans (GAG) and increased crosslinking in the nucleus pulposus using in vitro rat lumbar discs. Following initial mechanical testing the discs were injected according to the four treatment groups: PBS control, chondroitinase-ABC (ChABC) for GAG degradation, genipin (Gen) for crosslinking, or a combination of chondroitinase and genipin (ChABC+Gen). After treatment the discs were again mechanically tested, followed by histology or biochemistry. Neutral zone mechanical properties were changed by approximately 20% for PBS, ChABC, and ChABC+Gen treatments (significant only for PBS in a paired comparison). These trends were reversed with genipin crosslinking alone. With ChABC treatment the effective compressive modulus increased and the GAG content decreased; with the combination of ChABC+Gen the mechanics and GAG content were unchanged. Degradation of nucleus pulposus GAG alters disc axial mechanics, potentially contributing to the degenerative cascade. Crosslinking is unlikely to contribute to degeneration, but may be a potential avenue of treatment. PMID:16715318

  7. [Depression in Patients with Age-Related Macular Degeneration].

    PubMed

    Narváez, Yamile Reveiz; Gómez-Restrepo, Carlos

    2012-09-01

    Age-related macular degeneration is a cause for disability in the elderly since it greatly affects their quality of life and increases depression likelihood. This article discusses the negative effect depression has on patients with age-related macular degeneration and summarizes the interventions available for decreasing their depression index. PMID:26572116

  8. Effects of Material Degradation on the Structural Integrity of Composite Materials: Experimental Investigation and Modeling of High Temperature Degradation Mechanisms

    NASA Technical Reports Server (NTRS)

    Cunningham, Ronan A.; McManus, Hugh L.

    1996-01-01

    It has previously been demonstrated that simple coupled reaction-diffusion models can approximate the aging behavior of PMR-15 resin subjected to different oxidative environments. Based on empirically observed phenomena, a model coupling chemical reactions, both thermal and oxidative, with diffusion of oxygen into the material bulk should allow simulation of the aging process. Through preliminary modeling techniques such as this it has become apparent that accurate analytical models cannot be created until the phenomena which cause the aging of these materials are quantified. An experimental program is currently underway to quantify all of the reaction/diffusion related mechanisms involved. The following contains a summary of the experimental data which has been collected through thermogravimetric analyses of neat PMR-15 resin, along with analytical predictions from models based on the empirical data. Thermogravimetric analyses were carried out in a number of different environments - nitrogen, air and oxygen. The nitrogen provides data for the purely thermal degradation mechanisms while those in air provide data for the coupled oxidative-thermal process. The intent here is to effectively subtract the nitrogen atmosphere data (assumed to represent only thermal reactions) from the air and oxygen atmosphere data to back-figure the purely oxidative reactions. Once purely oxidative (concentration dependent) reactions have been quantified it should then be possible to quantify the diffusion of oxygen into the material bulk.

  9. Flavonoids and Age Related Disease: Risk, benefits and critical windows

    PubMed Central

    Prasain, JK; Carlson, SH; Wyss, JM

    2010-01-01

    Plant derived products are consumed by a large percentage of the population to prevent, delay and ameliorate disease burden; however, relatively little is known about the efficacy, safety and underlying mechanisms of these traditional health products, especially when taken in concert with pharmaceutical agents. The flavonoids are a group of plant metabolites that are common in the diet and appear to provide some health benefits. While flavonoids are primarily derived from soy, many are found in fruits, nuts and more exotic sources, e.g., kudzu. Perhaps the strongest evidence for the benefits of flavonoids in diseases of aging relates to their effect on components of the metabolic syndrome. Flavonoids from soy, grape seed, kudzu and other sources all lower arterial pressure in hypertensive animal models and in a limited number of tests in humans. They also decrease the plasma concentration of lipids and buffer plasma glucose. The underlying mechanisms appear to include antioxidant actions, central nervous system effects, gut transport alterations, fatty acid sequestration and processing, PPAR activation and increases in insulin sensitivity. In animal models of disease, dietary flavonoids also demonstrate a protective effect against cognitive decline, cancer and metabolic disease. However, research also indicates that the flavonoids can be detrimental in some settings and, therefore, are not universally safe. Thus, as the population ages, it is important to determine the impact of these agents on prevention/attenuation of disease, including optimal exposure (intake, timing/duration) and potential contraindications. PMID:20181448

  10. eNOS-uncoupling in age-related erectile dysfunction

    PubMed Central

    Johnson, JM; Bivalacqua, TJ; Lagoda, GA; Burnett, AL; Musicki, B

    2011-01-01

    Aging is associated with ED. Although age-related ED is attributed largely to increased oxidative stress and endothelial dysfunction in the penis, the molecular mechanisms underlying this effect are not fully defined. We evaluated whether endothelial nitric oxide synthase (eNOS) uncoupling in the aged rat penis is a contributing mechanism. Correlatively, we evaluated the effect of replacement with eNOS cofactor tetrahydrobiopterin (BH4) on erectile function in the aged rats. Male Fischer 344 ‘young’ (4-month-old) and ‘aged’ (19-month-old) rats were treated with a BH4 precursor sepiapterin (10 mg/kg intraperitoneally) or vehicle for 4 days. After 1-day washout, erectile function was assessed in response to electrical stimulation of the cavernous nerve. Endothelial dysfunction (eNOS uncoupling) and oxidative stress (thiobarbituric acid reactive substances, TBARS) were measured by conducting western blot in penes samples. Erectile response was significantly reduced in aged rats, whereas eNOS uncoupling and TBARS production were significantly increased in the aged rat penis compared with young rats. Sepiapterin significantly improved erectile response in aged rats and prevented increase in TBARS production, but did not affect eNOS uncoupling in the penis of aged rats. These findings suggest that aging induces eNOS uncoupling in the penis, resulting in increased oxidative stress and ED. PMID:21289638

  11. Reduced order modeling of mechanical degradation induced performance decay in lithium-ion battery porous electrodes

    DOE PAGESBeta

    Barai, Pallab; Smith, Kandler; Chen, Chien -Fan; Kim, Gi -Heon; Mukherjee, Partha P.

    2015-06-17

    In this paper, a one-dimensional computational framework is developed that can solve for the evolution of voltage and current in a lithium-ion battery electrode under different operating conditions. A reduced order model is specifically constructed to predict the growth of mechanical degradation within the active particles of the carbon anode as a function of particle size and C-rate. Using an effective diffusivity relation, the impact of microcracks on the diffusivity of the active particles has been captured. Reduction in capacity due to formation of microcracks within the negative electrode under different operating conditions (constant current discharge and constant current constantmore » voltage charge) has been investigated. At the beginning of constant current discharge, mechanical damage to electrode particles predominantly occurs near the separator. As the reaction front shifts, mechanical damage spreads across the thickness of the negative electrode and becomes relatively uniform under multiple discharge/charge cycles. Mechanical degradation under different drive cycle conditions has been explored. It is observed that electrodes with larger particle sizes are prone to capacity fade due to microcrack formation. Finally, under drive cycle conditions, small particles close to the separator and large particles close to the current collector can help in reducing the capacity fade due to mechanical degradation.« less

  12. Reduced order modeling of mechanical degradation induced performance decay in lithium-ion battery porous electrodes

    SciTech Connect

    Barai, Pallab; Smith, Kandler; Chen, Chien -Fan; Kim, Gi -Heon; Mukherjee, Partha P.

    2015-06-17

    In this paper, a one-dimensional computational framework is developed that can solve for the evolution of voltage and current in a lithium-ion battery electrode under different operating conditions. A reduced order model is specifically constructed to predict the growth of mechanical degradation within the active particles of the carbon anode as a function of particle size and C-rate. Using an effective diffusivity relation, the impact of microcracks on the diffusivity of the active particles has been captured. Reduction in capacity due to formation of microcracks within the negative electrode under different operating conditions (constant current discharge and constant current constant voltage charge) has been investigated. At the beginning of constant current discharge, mechanical damage to electrode particles predominantly occurs near the separator. As the reaction front shifts, mechanical damage spreads across the thickness of the negative electrode and becomes relatively uniform under multiple discharge/charge cycles. Mechanical degradation under different drive cycle conditions has been explored. It is observed that electrodes with larger particle sizes are prone to capacity fade due to microcrack formation. Finally, under drive cycle conditions, small particles close to the separator and large particles close to the current collector can help in reducing the capacity fade due to mechanical degradation.

  13. Semi-Degradable Poly(β-amino ester) Networks with Temporally-Controlled Enhancement of Mechanical Properties

    PubMed Central

    Safranski, David L.; Weiss, Daiana; Clark, J. Brian; Taylor, W.R.; Gall, Ken

    2014-01-01

    Biodegradable polymers are clinically used in numerous biomedical applications, and classically show a loss in mechanical properties within weeks of implantation. This work demonstrates a new class of semi-degradable polymers that show an increase in mechanical properties through degradation via a controlled shift in a thermal transition. Semi-degradable polymer networks, poly(β-amino ester)-co-methyl methacrylate, were formed from a low glass transition temperature crosslinker, poly(β-amino ester), and high glass transition temperature monomer, methyl methacrylate, which degraded in a manner dependent upon the crosslinker chemical structure. In vitro and in vivo degradation revealed changes in mechanical behavior due to the degradation of the crosslinker from the polymer network. This novel polymer system demonstrates a strategy to temporally control the mechanical behavior of polymers and to enhance the initial performance of smart biomedical devices. PMID:24769113

  14. Acid-catalyzed hydrolysis of BMS-582664: degradation product identification and mechanism elucidation.

    PubMed

    Zhao, Fang; Derbin, George; Miller, Scott; Badawy, Sherif; Hussain, Munir

    2012-09-01

    BMS-582664 is an investigational drug intended for cancer treatment through oral administration. The preformulation studies revealed two unexpected degradation products under acidic conditions by reversed-phase high-performance liquid chromatography with ultraviolet detection. Additional liquid chromatography-mass spectrometry results suggested that these were cleavage (hydrolysis) products of a diaryl ether. To further understand the degradation mechanism, the reaction was carried out in (18) O-labeled water. The (18) O was found to be incorporated in only one of the two hydrolysis products. The results suggest that the corresponding α carbon in the heterocycle was unusually eletrophilic in acidic conditions probably because of the protonation of the neighboring nitrogen. This led to the selective attack by water and the consequent hydrolysis products. The study provides a new example of hydrolytic degradation of pharmaceutical compounds, and the reaction center is an aromatic heterocyclic carbon with an aryloxy substitution. PMID:22189636

  15. Detection and location of mechanical system degradation by using detector signal noise data

    SciTech Connect

    Damiano, B.; Blakeman, E.D.; Phillips, L.D.

    1994-06-01

    This report describes the investigation of a diagnostic method for detecting and locating the source of structural degradation in mechanical systems. The goal of this investigation was to determine whether the diagnostic method would be practically and successfully applied to detect and locate structural changes in a mechanical system. The diagnostic method uses a mathematical model of the mechanical system to define relationships between system parameters, such as spring rates and damping rates, and measurable spectral features, such as natural frequencies and mode shapes. These model-defined relationships are incorporated into a neural network, which is used to relate measured spectral features to system parameters. The diagnosis of the system`s condition is performed by presenting the neural network with measured spectral features and comparing the system parameters estimated by the neural network to previously estimated values. Changes in the estimated system parameters indicate the location and severity of degradation in the mechanical system. The investigation involved applying the method by using computer-simulated data and data collected from a bench-top mechanical system. The effects of neural network training set size and composition on the accuracy of the model parameter estimates were investigated by using computer-simulated data. The measured data were used to demonstrate that the method can be applied to estimate the parameters of a {open_quotes}real{close_quotes} mechanical system. The results show that this diagnostic method can be applied to successfully locate and estimate the magnitude of structural changes in a mechanical system. The average error in the estimated spring rate values of the bench-top mechanical system was approximately 5 to 10%. This degree of accuracy is sufficient to permit the use of this method for detecting and locating structural degradation in mechanical systems.

  16. Deciphering Transcriptional Regulatory Mechanisms Associated with Hemicellulose Degradation in Neurospora crassa

    PubMed Central

    Sun, Jianping; Tian, Chaoguang; Diamond, Spencer

    2012-01-01

    Hemicellulose, the second most abundant plant biomass fraction after cellulose, is widely viewed as a potential substrate for the production of liquid fuels and other value-added materials. Degradation of hemicellulose by filamentous fungi requires production of many different enzymes, which are induced by biopolymers or its derivatives and regulated mainly at the transcriptional level through transcription factors (TFs). Neurospora crassa, a model filamentous fungus, expresses and secretes enzymes required for plant cell wall deconstruction. To better understand genes specifically associated with degradation of hemicellulose, we applied secretome and transcriptome analysis to N. crassa grown on beechwood xylan. We identified 34 secreted proteins and 353 genes with elevated transcription on xylan. The xylanolytic phenotype of strains with deletions in genes identified from the secretome and transcriptome analysis of the wild type was assessed, revealing functions for known and unknown proteins associated with hemicellulose degradation. By evaluating phenotypes of strains containing deletions of predicted TF genes in N. crassa, we identified a TF (XLR-1; xylan degradation regulator 1) essential for hemicellulose degradation that is an ortholog to XlnR/XYR1 in Aspergillus and Trichoderma species, respectively, a major transcriptional regulator of genes encoding both cellulases and hemicellulases. Deletion of xlr-1 in N. crassa abolished growth on xylan and xylose, but growth on cellulose and cellulolytic activity were only slightly affected. To determine the regulatory mechanisms for hemicellulose degradation, we explored the transcriptional regulon of XLR-1 under xylose, xylanolytic, and cellulolytic conditions. XLR-1 regulated only some predicted hemicellulase genes in N. crassa and was required for a full induction of several cellulase genes. Hemicellulase gene expression was induced by a combination of release from carbon catabolite repression (CCR) and induction

  17. A highly efficient degradation mechanism of methyl orange using Fe-based metallic glass powders.

    PubMed

    Xie, Shenghui; Huang, Ping; Kruzic, Jamie J; Zeng, Xierong; Qian, Haixia

    2016-01-01

    A new Fe-based metallic glass with composition Fe76B12Si9Y3 (at. %) is found to have extraordinary degradation efficiency towards methyl orange (MO, C14H14N3SO3) in strong acidic and near neutral environments compared to crystalline zero-valent iron (ZVI) powders and other Fe-based metallic glasses. The influence of temperature (294-328 K) on the degradation reaction rate was measured using ball-milled metallic glass powders revealing a low thermal activation energy barrier of 22.6 kJ/mol. The excellent properties are mainly attributed to the heterogeneous structure consisting of local Fe-rich and Fe-poor atomic clusters, rather than the large specific surface and strong residual stress in the powders. The metallic glass powders can sustain almost unchanged degradation efficiency after 13 cycles at room temperature, while a drop in degradation efficiency with further cycles is attributed to visible surface oxidation. Triple quadrupole mass spectrometry analysis conducted during the reaction was used to elucidate the underlying degradation mechanism. The present findings may provide a new, highly efficient and low cost commercial method for azo dye wastewater treatment. PMID:26902824

  18. Chemical stability and degradation mechanisms of triangular Ag, Ag@Au, and Au nanoprisms.

    PubMed

    Lee, Kee Eun; Hesketh, Amelia V; Kelly, Timothy L

    2014-06-28

    Anisotropic metal nanoparticles have found use in a variety of plasmonic applications because of the large near-field enhancements associated with them; however, the very features that give rise to these enhancements (e.g., sharply curved edges and tips) often have high surface energies and are easily degraded. This paper describes the stability and degradation mechanisms of triangular silver, gold-coated silver, and gold nanoprisms upon exposure to a wide variety of adverse conditions, including halide ions, thiols, amines and elevated temperatures. The silver nanoprisms were immediately and irreversibly degraded under all of the conditions studied. In contrast, the core-shell Ag@Au nanoprisms were less susceptible to etching by chlorides and bromides, but were rapidly degraded by iodides, amines and thiols by a different degradation pathway. Only the pure gold nanoprisms were stable to all of the conditions tested. These results have important implications for the suitability of triangular nanoprisms in many applications; this is particularly true in biological or environmental fields, where the nanoparticles would inevitably be exposed to a wide variety of chemical stimuli. PMID:24827005

  19. A highly efficient degradation mechanism of methyl orange using Fe-based metallic glass powders

    NASA Astrophysics Data System (ADS)

    Xie, Shenghui; Huang, Ping; Kruzic, Jamie J.; Zeng, Xierong; Qian, Haixia

    2016-02-01

    A new Fe-based metallic glass with composition Fe76B12Si9Y3 (at. %) is found to have extraordinary degradation efficiency towards methyl orange (MO, C14H14N3SO3) in strong acidic and near neutral environments compared to crystalline zero-valent iron (ZVI) powders and other Fe-based metallic glasses. The influence of temperature (294-328 K) on the degradation reaction rate was measured using ball-milled metallic glass powders revealing a low thermal activation energy barrier of 22.6 kJ/mol. The excellent properties are mainly attributed to the heterogeneous structure consisting of local Fe-rich and Fe-poor atomic clusters, rather than the large specific surface and strong residual stress in the powders. The metallic glass powders can sustain almost unchanged degradation efficiency after 13 cycles at room temperature, while a drop in degradation efficiency with further cycles is attributed to visible surface oxidation. Triple quadrupole mass spectrometry analysis conducted during the reaction was used to elucidate the underlying degradation mechanism. The present findings may provide a new, highly efficient and low cost commercial method for azo dye wastewater treatment.

  20. A highly efficient degradation mechanism of methyl orange using Fe-based metallic glass powders

    PubMed Central

    Xie, Shenghui; Huang, Ping; Kruzic, Jamie J.; Zeng, Xierong; Qian, Haixia

    2016-01-01

    A new Fe-based metallic glass with composition Fe76B12Si9Y3 (at. %) is found to have extraordinary degradation efficiency towards methyl orange (MO, C14H14N3SO3) in strong acidic and near neutral environments compared to crystalline zero-valent iron (ZVI) powders and other Fe-based metallic glasses. The influence of temperature (294–328 K) on the degradation reaction rate was measured using ball-milled metallic glass powders revealing a low thermal activation energy barrier of 22.6 kJ/mol. The excellent properties are mainly attributed to the heterogeneous structure consisting of local Fe-rich and Fe-poor atomic clusters, rather than the large specific surface and strong residual stress in the powders. The metallic glass powders can sustain almost unchanged degradation efficiency after 13 cycles at room temperature, while a drop in degradation efficiency with further cycles is attributed to visible surface oxidation. Triple quadrupole mass spectrometry analysis conducted during the reaction was used to elucidate the underlying degradation mechanism. The present findings may provide a new, highly efficient and low cost commercial method for azo dye wastewater treatment. PMID:26902824

  1. The contribution of mediated oxidation mechanisms in the electrolytic degradation of cyanuric acid using diamond anodes.

    PubMed

    Bensalah, Nasr; Dbira, Sondos; Bedoui, Ahmed

    2016-07-01

    In this work, the contribution of mediated oxidation mechanisms in the electrolytic degradation of cyanuric acid using boron-doped diamond (BDD) anodes was investigated in different electrolytes. A complete mineralization of cyanuric acid was obtained in NaCl; however lower degrees of mineralization of 70% and 40% were obtained in Na2SO4 and NaClO4, respectively. This can be explained by the nature of the oxidants electrogenerated in each electrolyte. It is clear that the contribution of active chlorine (Cl2, HClO, ClO(-)) electrogenerated from oxidation of chlorides on BDD is much more important in the electrolytic degradation of cyanuric acid than the persulfate and hydroxyl radicals produced by electro-oxidation of sulfate and water on BDD anodes. This could be explained by the high affinity of active chlorine towards nitrogen compounds. No organic intermediates were detected during the electrolytic degradation of cyanuric acid in any the electrolytes, which can be explained by their immediate depletion by hydroxyl radicals produced on the BDD surface. Nitrates and ammonium were the final products of electrolytic degradation of cyanuric acid on BDD anodes in all electrolytes. In addition, small amounts of chloramines were formed in the chloride medium. Low current density (≤10mA/cm(2)) and neutral medium (pH in the range 6-9) should be used for high efficiency electrolytic degradation and negligible formation of hazardous chlorate and perchlorate. PMID:27372125

  2. The influence of silanisation on the mechanical and degradation behaviour of PLGA/HA composites.

    PubMed

    Naik, Ashutosh; Best, Serena M; Cameron, Ruth E

    2015-03-01

    This study investigates the influence of silanisation on the mechanical and degradation behaviour of PLGA/HA composites. Three different silanes (mercaptopropyl trimethoxy silane (MPTMS), aminopropyl trimethoxy silane (APTMS) and aminopropyltriethoxy silane (APTES)) were applied to HA substrates in order to study the effect of head group (which binds to the polymer) and tail group (which binds to the surface hydroxyl groups in HA). A composite of hydroxyapatite (HA) and poly(d,l lactide-co-glycolide (50:50)) (PLGA) was investigated. The influence of concentration, the reaction time, drying temperature and substrate surface on silanisation was examined. TGA was used to detect the degree of silanisation. HA with MPTMS (1wt.% MPTMS with reaction time of 1h) was used as filler in PLGA-30wt.% HA composites for an in-vitro degradation study carried out in PBS. In addition, the mechanical properties of the composites were studied. Silanisation affects the properties of the composite by improving the bonding at the interface and hence it was found to influence the plastic mechanical properties rather than the elastic mechanical properties or the degradation profile of the composite. PMID:25579967

  3. Mechanical behaviour of degradable phosphate glass fibres and composites-a review.

    PubMed

    Colquhoun, R; Tanner, K E

    2016-02-01

    Biodegradable materials are potentially an advantageous alternative to the traditional metallic fracture fixation devices used in the reconstruction of bone tissue defects. This is due to the occurrence of stress shielding in the surrounding bone tissue that arises from the absence of mechanical stimulus to the regenerating bone due to the mismatch between the elastic modulus of bone and the metal implant. However although degradable polymers may alleviate such issues, these inert materials possess insufficient mechanical properties to be considered as a suitable alternative to current metallic devices at sites of sufficient mechanical loading. Phosphate based glasses are an advantageous group of materials for tissue regenerative applications due to their ability to completely degrade in vivo at highly controllable rates based on the specific glass composition. Furthermore the release of the glass's constituent ions can evoke a therapeutic stimulus in vivo (i.e. osteoinduction) whilst also generating a bioactive response. The processing of these materials into fibres subsequently allows them to act as reinforcing agents in degradable polymers to simultaneously increase its mechanical properties and enhance its in vivo response. However despite the various review articles relating to the compositional influences of different phosphate glass systems, there has been limited work summarising the mechanical properties of different phosphate based glass fibres and their subsequent incorporation as a reinforcing agent in degradable composite materials. As a result, this review article examines the compositional influences behind the development of different phosphate based glass fibre compositions intended as composite reinforcing agents along with an analysis of different potential composite configurations. This includes variations in the fibre content, matrix material and fibre architecture as well as other novel composites designs. PMID:26694533

  4. Degradation Mechanisms and Lifetime Prediction for Lithium-Ion Batteries -- A Control Perspective: Preprint

    SciTech Connect

    Smith, Kandler; Shi, Ying; Santhanagopalan, Shriram

    2015-07-29

    Predictive models of Li-ion battery lifetime must consider a multiplicity of electrochemical, thermal, and mechanical degradation modes experienced by batteries in application environments. To complicate matters, Li-ion batteries can experience different degradation trajectories that depend on storage and cycling history of the application environment. Rates of degradation are controlled by factors such as temperature history, electrochemical operating window, and charge/discharge rate. We present a generalized battery life prognostic model framework for battery systems design and control. The model framework consists of trial functions that are statistically regressed to Li-ion cell life datasets wherein the cells have been aged under different levels of stress. Degradation mechanisms and rate laws dependent on temperature, storage, and cycling condition are regressed to the data, with multiple model hypotheses evaluated and the best model down-selected based on statistics. The resulting life prognostic model, implemented in state variable form, is extensible to arbitrary real-world scenarios. The model is applicable in real-time control algorithms to maximize battery life and performance. We discuss efforts to reduce lifetime prediction error and accommodate its inevitable impact in controller design.

  5. System Voltage Potential-Induced Degradation Mechanisms in PV Modules and Methods for Test: Preprint

    SciTech Connect

    Hacke, P.; Terwilliger, K.; Smith, R.; Glick, S.; Pankow, J.; Kempe, M.; Kurtz, S.; Bennett, I.; Kloos, M.

    2011-07-01

    Over the past decade, degradation and power loss have been observed in PV modules resulting from the stress exerted by system voltage bias. This is due in part to qualification tests and standards that do not adequately evaluate for the durability of modules to the long-term effects of high voltage bias experienced in fielded arrays. High voltage can lead to module degradation by multiple mechanisms. The extent of the voltage bias degradation is linked to the leakage current or coulombs passed from the silicon active layer through the encapsulant and glass to the grounded module frame, which can be experimentally determined; however, competing processes make the effect non-linear and history-dependent. Appropriate testing methods and stress levels are described that demonstrate module durability to system voltage potential-induced degradation (PID) mechanisms. This information, along with outdoor testing that is in progress, is used to estimate the acceleration factors needed to evaluate the durability of modules to system voltage stress. Na-rich precipitates are observed on the cell surface after stressing the module to induce PID in damp heat with negative bias applied to the active layer.

  6. System Voltage Potential-Induced Degradation Mechanisms in PV Modules and Methods for Test

    SciTech Connect

    Hacke, P.; Terwilliger, K.; Smith, R.; Glick, S.; Pankow, J.; Kempe, M.; Kurtz, S.; Bennett, I.; Kloos, M.

    2011-01-01

    Over the past decade, degradation and power loss have been observed in PV modules resulting from the stress exerted by system voltage bias. This is due in part to qualification tests and standards that do not adequately evaluate for the durability of modules to the long-term effects of high voltage bias experienced in fielded arrays. High voltage can lead to module degradation by multiple mechanisms. The extent of the voltage bias degradation is linked to the leakage current or culombs passed from the silicon active layer through the encapsulant and glass to the grounded module frame, which can be experimentally determined; however, competing processes make the effect non-linear and history-dependent. Appropriate testing methods and stress levels are described that demonstrate module durability to system voltage potential-induced degradation (PID) mechanisms. This information, along with outdoor testing that is in progress, is used to estimate the acceleration factors needed to evaluate the durability of modules to system voltage stress. Na-rich precipitates are observed on the cell surface after stressing the module to induce PID in damp heat with negative bias applied to the active layer.

  7. An efficient and environment-friendly method of removing graphene oxide in wastewater and its degradation mechanisms.

    PubMed

    Zhang, Chao-Zhi; Li, Ting; Yuan, Yang; Xu, Jianqiang

    2016-06-01

    Graphene and graphene oxide (GO) have already existed in air, water and soil due to their popular application in functional materials. However, degradation of graphene and GO in wastewater has not been reported. Degradation of GO plays a key role in the elimination of graphene and GO in wastewater due to graphene being easily oxidized to GO. In this paper, GO was completely degraded to give CO2 by Photo-Fenton. The degradation intermediates were determined by UV-vis absorption spectra, elemental analysis (EA), fourier transform infrared (FT-IR) and liquid chromatography-mass spectrometry (LC-MS). Experimental results showed that graphene oxide was completely degraded to give CO2 after 28 days. Based on UV, FT-IR, LC-MS spectra and EA data of these degradation intermediates, the degradation mechanisms of GO were supposed. This paper suggests an efficient and environment-friendly method to degrade GO and graphene. PMID:27042978

  8. Theoretical predictions of chemical degradation reaction mechanisms of RDX and other cyclic nitramines derived from their molecular structures.

    PubMed

    Qasim, M; Fredrickson, H; McGrath, C; Furey, J; Bajpai, R

    2005-06-01

    Analysis of environmental degradation pathways of contaminants is aided by predictions of likely reaction mechanisms and intermediate products derived from computational models of molecular structure. Quantum mechanical methods and force-field molecular mechanics were used to characterize cyclic nitramines. Likely degradation mechanisms for hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) include hydroxylation utilizing addition of hydroxide ions to initiate proton abstraction via 2nd order rate elimination (E2) or via nucleophilic substitution of nitro groups, reductive chemical and biochemical degradation, and free radical oxidation. Due to structural similarities, it is predicted that, under homologous circumstances, certain RDX environmental degradation pathways should also be effective for octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) and similar cyclic nitramines. Computational models provided a theoretical framework whereby likely transformation mechanisms and transformation products of cyclic nitramines were predicted and used to elucidate in situ degradation pathways. PMID:15804809

  9. Mechanisms of soil degradation and consequences for carbon stocks on Tibetan grasslands

    NASA Astrophysics Data System (ADS)

    Kuzyakov, Yakov; Schleuss, Per-Marten; Miehe, Georg; Heitkamp, Felix; Sebeer, Elke; Spielvogel, Sandra; Xu, Xingliang; Guggenberger, Georg

    2016-04-01

    Tibetan grasslands provide tremendous sinks for carbon (C) and represent important grazing ground. Strong degradation - the destroying the upper root-mat/soil horizon of Kobresia pastures, has dramatic consequences for soil organic carbon (SOC) and nutrient storage. To demonstrate specific degradation patterns and elucidate mechanisms, as well as to assess consequences for SOC storage, we investigated a sequence of six degradation stages common over the whole Kobresia ecosystem. The soil degradation sequence consists of following mechanisms: Overgrazing and trampling by livestock provide the prerequisite for grassland degradation as both (a) cause plant dying, (b) reduce grassland recovery and (c) destroy protective Kobresia root-mats. These anthropogenic induced processes are amplified by naturally occurring degradation in harsh climate. The frequently repeated soil moisture and temperature fluctuations induce volume changes and tensions leading to polygonal cracking of the root mats. Then the plants die and erosion gradually extend the surface cracks. Soil erosion cause a high SOC loss from the upper horizons (0-10 cm: ~5.1 kg C m-2), whereas SOC loss beneath the surface cracks is caused by both, decreasing root C-input and SOC mineralization (SOC losses by mineralization: ~2.5 kg C m-2). Root biomass decreases with degradation and indicated lower C input. The negative δ13C shift of SOC reflects intensive decomposition and corresponds to a relative enrichment of 13C depleted lignin components. We conclude that the combined effects of overgrazing and harsh climate reduce root C input, increase SOC decomposition and initiate erosion leading to SOC loss up to 70% of intact soil (0-30 cm: ~7.6 kg C m-2). Consequently, a high amount of C is released back to the atmosphere as CO2, or is deposited in depressions and river beds creating a potential source of N2O and CH4. Concluding, anthropogenically induced overgrazing makes the Kobresia root-mat sensitive to natural

  10. Degradation of trichloroethene by siderite-catalyzed hydrogen peroxide and persulfate: Investigation of reaction mechanisms and degradation products

    PubMed Central

    Yan, Ni; Liu, Fei; Xue, Qiang; Brusseau, Mark L.; Liu, Yali; Wang, Junjie

    2015-01-01

    A binary catalytic system, siderite-catalyzed hydrogen peroxide (H2O2) coupled with persulfate (S2O82−), was investigated for the remediation of trichloroethene (TCE) contamination. Batch experiments were conducted to investigate reaction mechanisms, oxidant decomposition rates, and degradation products. By using high performance liquid chromatography (HPLC) coupled with electron paramagnetic resonance (EPR), we identified four radicals (hydroxyl (HO·), sulfate (SO4−·), hydroperoxyl (HO2·), and superoxide (O2−·)) in the siderite-catalyzed H2O2-S2O82− system. In the absence of S2O82− (i.e., siderite-catalyzed H2O2), a majority of H2O2 was decomposed in the first hour of the experiment, resulting in the waste of HO·. The addition of S2O82− moderated the H2O2 decomposition rate, producing a more sustainable release of hydroxyl radicals that improved the treatment efficiency. Furthermore, the heat released by H2O2 decomposition accelerated the activation of S2O82−, and the resultant SO4−· was the primary oxidative agent during the first two hours of the reaction. Dichloroacetic acid was firstly detected by ion chromatography (IC). The results of this study indicate a new insight to the reaction mechanism for the catalytic binary H2O2-S2O82− oxidant system, and the delineation of radicals and the discovery of the chlorinated byproduct provide useful information for efficient treatment of chlorinated-solvent contamination in groundwater. PMID:26236152

  11. Degradation Kinetics and Mechanism of a β-Lactam Antibiotic Intermediate, 6-Aminopenicillanic Acid, in a New Integrated Production Process.

    PubMed

    Su, Min; Sun, Hua; Zhao, Yingying; Lu, Aidang; Cao, Xiaohui; Wang, Jingkang

    2016-01-01

    In an effort to promote sustainability and to reduce manufacturing costs, the traditional production process for 6-aminopenicillanic acid (6-APA) has been modified to include less processing units. The objectives of this study are to investigate the degradation kinetics of 6-APA, to propose a reasonable degradation mechanism, and to optimize the manufacturing conditions within this new process. A series of degradation kinetic studies were conducted in the presence of impurities, as well as at various chemical and physical conditions. The concentrations of 6-APA were determined by high-performance liquid chromatography. An Arrhenius-type kinetic model was established to give a more accurate prediction on the degradation rates of 6-APA. A hydrolysis degradation mechanism is shown to be the major pathway for 6-APA. The degradation mechanisms and the kinetic models for 6-APA in the new system enable the design of a good manufacturing process with optimized parameters. PMID:26852849

  12. Poly(ethylene glycol) Hydrogels with Adaptable Mechanical and Degradation Properties for Use in Biomedical Applicationsa

    PubMed Central

    Parlato, Matthew; Reichert, Sarah; Barney, Neal

    2014-01-01

    Requirements of hydrogels for drug delivery, wound dressings, and surgical implantation can be extensive, including suitable mechanical properties and tailorable degradation time frames. Herein, an adaptable PEG-based hydrogel, whose mechanical properties and degradation rate can be systematically adjusted to meet these criteria by altering simple variables such as the PEG molecular weight, is described. The performance of these hydrogels in three physical manipulations (pushing, pulling, and folding), representative of manipulations that they may undergo during typical biomedical use, is also assessed. While not all of these formulations can withstand these manipulations, a subset did, and it is intended to further optimize these formulations for specific clinical applications. Additionally, the outcomes of the physical manipulation tests indicate that simply having a high modulus does not correlate with biomedical applicability. PMID:24949497

  13. Mechanical and microstructural/chemical degradation of coating and substrate in gas turbine blade

    SciTech Connect

    Sugita, Y.; Ito, M.; Sakurai, S.; Gold, C.R.; Bloomer, T.E.; Kameda, J.

    1995-12-31

    The mechanical property degradation (295--1223 K) and microstructural/chemical evolution of CoNiCrAlY coatings and superalloy (Rene 80) substrates in gas turbine blades operated in- service have been studied using a small punch (SP) testing technique and scanning Auger microprobe. In SP tests, coating cracks continuously and discretely propagated at 295 K and higher temperatures, respectively. The ductile-brittle transition temperature of the coatings was increased during long time exposure of gas turbine blades to oxidizing environments while that of the substrate did not change. The low cycle fatigue life of the coatings at 295 K was also reduced in-service. Oxidation and sulfur segregation near the coating surface were found to be major causes of the mechanical degradation of the coatings.

  14. Mechanism of hydroxyl radical generation from biochar suspensions: Implications to diethyl phthalate degradation.

    PubMed

    Fang, Guodong; Zhu, Changyin; Dionysiou, Dionysios D; Gao, Juan; Zhou, Dongmei

    2015-01-01

    This paper investigated hydroxyl radical (OH) generation from biochar suspensions for diethyl phthalate (DEP) degradation in the presence of oxygen. Electron paramagnetic resonance (EPR) coupled with a salicylic acid trapping method were used to detect free radicals in biochar and verify OH generation from biochar suspensions. Free radicals (FRs) in biochar could induce OH generation, and ≈12 spins of FRs were consumed to produce one trapped [OH] molecule. The proposed mechanism of OH generation was that FRs in biochar transferred electrons to O2 to produce the superoxide radical anion and hydrogen peroxide, which reacted further with FRs to produce OH. Free radical-quenching studies utilizing superoxide dismutase, catalase, and deferoxamine as scavengers were used to testify this mechanism. Furthermore, OH generated from biochar suspensions could degrade DEP efficiently. These findings of this study provide new insights into the physicochemical properties and environmental implications of biochar. PMID:25461005

  15. Kinetics and mechanisms of degradation of chloroacetonitriles by the UV/H2O2 process.

    PubMed

    Ling, Li; Sun, Jianliang; Fang, Jingyun; Shang, Chii

    2016-08-01

    Haloacetonitriles (HANs) are emerging disinfection by-products (DBPs) that are more toxic than the regulated DBPs and widely found in the chlorinated/chloraminated water. This paper studied kinetics and mechanisms of the degradation of chloroacetonitriles (CANs) by the UV/H2O2 process at pH 6 and 7.5 and H2O2 concentrations of 1 × 10(-3) M, 5 × 10(-3) M and 1 × 10(-2) M. The degradation followed pseudo first-order degradation kinetics. The degradation rate of monochloroacetonitrile (MCAN) remained similar, while those of dichloroacetonitrile (DCAN) and trichloroacetonitrile (TCAN) increased with increasing pH and H2O2 concentrations. The different trends were attributed to the changing contributions of the two major mechanisms: the nucleophilic attack by hydroperoxide ions ( [Formula: see text] ) and the hydroxyl radical (•OH) oxidation. The second-order rate constants of [Formula: see text] towards MCAN, DCAN and TCAN were determined to be 11.8 (±0.62), 4.83 (±0.01) × 10(3), and 2.54 (±0.23) × 10(5) M(-1) s(-1), respectively, while that of •OH were 8.7 × 10(6), 4.4 × 10(6), and < 10(6) M(-1) s(-1), respectively. The degradation of TCAN was mainly attributed to the [Formula: see text] nucleophilic attack, while that of MCAN was dominated by the •OH oxidation. DCAN was degraded by both mechanisms. The nucleophilic attack increased linearly with increasing [Formula: see text] concentration as a result of increasing H2O2 concentration and/or pH, while the •OH oxidation was less dependent on H2O2 concentrations and/or pH. The nucleophilic attack mainly transformed HANs to haloacetamides, while the •OH oxidation dechlorinated HANs. This paper firstly illustrated the importance of the [Formula: see text] nucleophilic attack, in addition to the •OH oxidation, on the CAN degradation in the UV/H2O2 process. PMID:27161887

  16. Cellular models and therapies for age-related macular degeneration

    PubMed Central

    Forest, David L.; Johnson, Lincoln V.; Clegg, Dennis O.

    2015-01-01

    ABSTRACT Age-related macular degeneration (AMD) is a complex neurodegenerative visual disorder that causes profound physical and psychosocial effects. Visual impairment in AMD is caused by the loss of retinal pigmented epithelium (RPE) cells and the light-sensitive photoreceptor cells that they support. There is currently no effective treatment for the most common form of this disease (dry AMD). A new approach to treating AMD involves the transplantation of RPE cells derived from either human embryonic or induced pluripotent stem cells. Multiple clinical trials are being initiated using a variety of cell therapies. Although many animal models are available for AMD research, most do not recapitulate all aspects of the disease, hampering progress. However, the use of cultured RPE cells in AMD research is well established and, indeed, some of the more recently described RPE-based models show promise for investigating the molecular mechanisms of AMD and for screening drug candidates. Here, we discuss innovative cell-culture models of AMD and emerging stem-cell-based therapies for the treatment of this vision-robbing disease. PMID:26035859

  17. Age related susceptibility of pigs to Cryptosporidium scrofarum infection.

    PubMed

    Kváč, Martin; Němejc, Karel; Kestřánová, Michaela; Květoňová, Dana; Wagnerová, Pavla; Kotková, Michaela; Rost, Michael; Samková, Eva; McEvoy, John; Sak, Bohumil

    2014-05-28

    Piglets from 4 to 8 weeks of age originated from a Cryptosporidium-free research breed were orally inoculated with 1 × 10(6) infectious oocysts of Cryptosporidium scrofarum. The number of shed oocysts per gram of faeces served to describe the infection intensity and prepatent period. In addition, faecal samples collected daily and tissue samples of the small and large intestine collected at 30 days post-inoculation were examined for the C. scrofarum small subunit ribosomal RNA gene using PCR. The piglets inoculated at 4-weeks of age remained uninfected, whereas 5-week-old and older animals were fully susceptible with a prepatent period ranging from 4 to 8 days. Susceptible pigs shed oocysts intermittently, and shedding intensity, reaching a mean maximum of 6000 oocysts per gram, did not differ significantly among infected animals. This study demonstrates that pigs become susceptible to C. scrofarum infection as late as 5-weeks of age. The mechanisms of age related susceptibility remain unknown. PMID:24630710

  18. Epigenetic modification of PKMζ rescues aging-related cognitive impairment

    PubMed Central

    Chen, Chen; Meng, Shi-Qiu; Xue, Yan-Xue; Han, Ying; Sun, Cheng-Yu; Deng, Jia-Hui; Chen, Na; Bao, Yan-Ping; Zhang, Fei-Long; Cao, Lin-Lin; Zhu, Wei-Guo; Shi, Jie; Song, Wei-Hong; Lu, Lin

    2016-01-01

    Cognition is impacted by aging. However, the mechanisms that underlie aging-associated cognitive impairment are unclear. Here we showed that cognitive decline in aged rats was associated with changes in DNA methylation of protein kinase Mζ (PKMζ) in the prelimbic cortex (PrL). PKMζ is a crucial molecule involved in the maintenance of long-term memory. Using different behavioral models, we confirmed that aged rats exhibited cognitive impairment in memory retention test 24 h after training, and overexpression of PKMζ in the PrL rescued cognitive impairment in aged rats. After fear conditioning, the protein levels of PKMζ and the membrane expression of GluR2 increased in the PrL in young and adult rats but not in aged rats, and the levels of methylated PKMζ DNA in the PrL decreased in all age groups, whereas the levels of unmethylated PKMζ DNA increased only in young and adult rats. We also found that environmentally enriched housing reversed the hypermethylation of PKMζ and restored cognitive performance in aged rats. Inactivation of PKMζ prevented the potentiating effects of environmental enrichment on memory retention in aged rats. These results indicated that PKMζ might be a potential target for the treatment of aging-related cognitive impairment, suggesting a potential therapeutic avenue. PMID:26926225

  19. Promising new treatments for neovascular age-related macular degeneration.

    PubMed

    Michels, Stephan; Schmidt-Erfurth, Ursula; Rosenfeld, Philip J

    2006-07-01

    Angiogenesis, the growth of new blood vessels from existing blood vessels, is responsible for vision loss in a variety of ophthalmic diseases. In neovascular age-related macular degeneration (AMD), the leading cause for legal blindness in many industrialised countries, abnormal blood vessels grow in the macula and cause blindness. There are a number of factors important in the angiogenic cascade but VEGF-A has been implicated in recent years as the major factor responsible for neovascular and exudative diseases of the eye. Numerous antiangiogenic drugs are in development but anti-VEGF drugs have shown great promise in treating neovascular AMD and other ocular diseases, and many of these drugs have been adopted from oncology where antiangiogenic therapy is gaining wide acceptance. For the first time in neovascular AMD, anti-VEGF drugs have brought the hope of vision improvement to a significant proportion of patients. This review provides an overview on angiogenic mechanisms, potential antiangiogenic treatment strategies and different antiangiogenic drugs with special focus on neovascular AMD. PMID:16787141

  20. Low Calorie Diet Affects Aging-Related Factors

    MedlinePlus

    ... Research News From NIH Low Calorie Diet Affects Aging-Related Factors Past Issues / Summer 2006 Table of ... project sponsored by the NIH's National Institute on Aging (NIA) to learn more about the effects of ...

  1. Low Calorie Diet Affects Aging-Related Factors

    MedlinePlus

    ... Issue Past Issues Research News From NIH Low Calorie Diet Affects Aging-Related Factors Past Issues / Summer ... learn more about the effects of sustained low-calorie diets in humans on factors affecting aging. This ...

  2. Debris generation from Mechanical degradation of MLI and thermo-control coating

    NASA Astrophysics Data System (ADS)

    Duzellier, Sophie; Drolshagen, Gerhard; Pons, Claude; Rey, Romain; Gordo, Paulo; Horstmann, Andre

    2016-07-01

    Space environment is a harsh environment for exposed materials. Amongst all environmental constraints, ionizing radiation in GEO (particles, UV), atomic oxygen in LEO and temperature variation through synergy mechanisms may lead to serious damage and loss of performance of surface materials (thermo-optical or mechanical properties). Optical and radar observations from the ground as well as analysis of retrieved hardware have shown an abundance of space debris objects that seem to result from the degradation of outer spacecraft surfaces. Recent surveys of the GEO and GTO region have found many objects with high area-to-mass ratio (HAMR debris, see T. Childknecht et al. 2003, 2004, 2005) indicating that they must consist of relatively thin material, like foils. This paper explores the cause, amount and characteristics of space debris objects resulting from spacecraft surface degradation in order to improve space debris population models and support the selection of materials in the context of debris mitigation measures. 20-year GEO dose profile along with thermal cycling has been applied to a set of MLI assemblies and painting samples. The material degradation was monitored through in and ex situ characterizations (visual observation, mechanical and thermo-optical). No self-flaking was observed for paintings nor for MLIs. However, paint surfaces became very brittle, whereas reclosable fasteners of MLIs and Mylar inner foils were strongly damaged as well. Potential scenarios for delamination of MLI foils could be defined.

  3. Stochastic mechanical degradation of multi-cracked fiber bundles with elastic and viscous interactions.

    PubMed

    Manca, Fabio; Giordano, Stefano; Palla, Pier Luca; Cleri, Fabrizio

    2015-05-01

    The mechanics of fiber bundles has been largely investigated in order to understand their complex failure modes. Under a mechanical load, the fibers fail progressively while the load is redistributed among the unbroken fibers. The classical fiber bundle model captures the most important features of this rupture process. On the other hand, the homogenization techniques are able to evaluate the stiffness degradation of bulk solids with a given population of cracks. However, these approaches are inadequate to determine the effective response of a degraded bundle where breaks are induced by non-mechanical actions. Here, we propose a method to analyze the behavior of a fiber bundle, undergoing a random distribution of breaks, by considering the intrinsic response of the fibers and the visco-elastic interactions among them. We obtain analytical solutions for simple configurations, while the most general cases are studied by Monte Carlo simulations. We find that the degradation of the effective bundle stiffness can be described by two scaling regimes: a first exponential regime for a low density of breaks, followed by a power-law regime at increasingly higher break density. For both regimes, we find analytical effective expressions described by specific scaling exponents. PMID:25998172

  4. 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.

  5. Age-related changes in the misinformation effect.

    PubMed

    Sutherland, R; Hayne, H

    2001-08-01

    In these experiments, we examined the relation between age-related changes in retention and age-related changes in the misinformation effect. Children (5- and 6- and 11- and 12-year-olds) and adults viewed a video, and their memory was assessed immediately, 1 day, or 6 weeks later (Experiment 1). There were large age-related differences in retention when participants were interviewed immediately and after 1 day, but after the 6-week delay, age-related differences in retention were minimal. In Experiment 2, 11- and 12-year-olds and adults were exposed to neutral, leading, and misleading postevent information 1 day or 6 weeks after they viewed the video. Exposure to misleading information increased the number of commission errors, particularly when participants were asked about peripheral aspects of the video. At both retention intervals, children were more likely than adults to incorporate the misleading postevent information into their subsequent verbal accounts. These findings indicate that age-related changes in the misinformation effect are not predicted by age-related changes in retention. PMID:11511130

  6. Mechanical behaviour׳s evolution of a PLA-b-PEG-b-PLA triblock copolymer during hydrolytic degradation.

    PubMed

    Breche, Q; Chagnon, G; Machado, G; Girard, E; Nottelet, B; Garric, X; Favier, D

    2016-07-01

    PLA-b-PEG-b-PLA is a biodegradable triblock copolymer that presents both the mechanical properties of PLA and the hydrophilicity of PEG. In this paper, physical and mechanical properties of PLA-b-PEG-b-PLA are studied during in vitro degradation. The degradation process leads to a mass loss, a decrease of number average molecular weight and an increase of dispersity index. Mechanical experiments are made in a specific experimental set-up designed to create an environment close to in vivo conditions. The viscoelastic behaviour of the material is studied during the degradation. Finally, the mechanical behaviour is modelled with a linear viscoelastic model. A degradation variable is defined and included in the model to describe the hydrolytic degradation. This variable is linked to physical parameters of the macromolecular polymer network. The model allows us to describe weak deformations but become less accurate for larger deformations. The abilities and limits of the model are discussed. PMID:26919565

  7. Mass spectrometric analysis for high molecular weight synthetic polymers using ultrasonic degradation and the mechanism of degradation.

    PubMed

    Kawasaki, Hideya; Takeda, Yoshiki; Arakawa, Ryuichi

    2007-06-01

    We have investigated ultrasonic degradations of poly(ethylene oxide) (PEG) and poly(methyl methacrylate) (PMMA) in aqueous media by means of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS). The ultrasonic degradation of polymers was monitored as a function of ultrasonication duration to examine the structural details of ultrasonic degradation polymers. PEG solution ultrasonication produced five types of oligomers (M approximately 1000 Da) with different end groups, irrespective of the initial average molecular masses (M=2, 6, 20, and 2000 kDa). Several degradation pathways with free radical reactions have been suggested to explain these degradation products: the ultrasonic degradation of PEG is initiated by breaking of the C-O bond in the PEG chain, generating polymeric radicals with two terminal groups, i.e., X*( approximately CH2CH2*) and Y*( approximately CH2CH2O*), followed by termination with extraction or release of a hydrogen atom. However, PMMA (M=1630 Da) ultrasonication generated only one type of degradation oligomer, which has a hydrogen group at both ends, the same as that of the original oligomer. It has been suggested that the presence of the radical terminal groups X*( approximately CH2*) and Y*( approximately (CH3)CCOO(CH3)C*) is due to selective C-C bond breaking in the chain during the ultrasonic degradation of PMMA. The MALDI-TOFMS combined with the ultrasonic degradation technique (UD/MALDI-TOFMS) developed in this study could be extended to the analysis of synthetic polymer structures with high molecular weights. PMID:17461552

  8. Laccase-catalyzed decolorization of malachite green: performance optimization and degradation mechanism.

    PubMed

    Yang, Jie; Yang, Xiaodan; Lin, Yonghui; Ng, Tzi Bun; Lin, Juan; Ye, Xiuyun

    2015-01-01

    Malachite green (MG) was decolorized by laccase (LacA) of white-rot fungus Cerrena sp. with strong decolorizing ability. Decolorization conditions were optimized with response surface methodology. A highly significant quadratic model was developed to investigate MG decolorization with LacA, and the maximum MG decolorization ratio of 91.6% was predicted under the conditions of 2.8 U mL(-1) LacA, 109.9 mg L(-1) MG and decolorization for 172.4 min. Kinetic studies revealed the Km and kcat values of LacA toward MG were 781.9 mM and 9.5 s(-1), respectively. UV-visible spectra confirmed degradation of MG, and the degradation mechanism was explored with liquid chromatography-mass spectrometry (LC-MS) analysis. Based on the LC-MS spectra of degradation products, LacA catalyzed MG degradation via two simultaneous pathways. In addition, the phytotoxicity of MG, in terms of inhibition on seed germination and seedling root elongation of Nicotiana tabacum and Lactuca sativa, was reduced after laccase treatment. These results suggest that laccase of Cerrena was effective in decolorizing MG and promising in bioremediation of wastewater in food and aquaculture industries. PMID:26020270

  9. Mechanisms of degradation in adhesive joint strength: Glassy polymer thermoset bond in a humid environment

    SciTech Connect

    Kropka, Jamie Michael; Adolf, Douglas Brian; Spangler, Scott Wilmer; Austin, Kevin N.; Chambers, Robert S.

    2015-08-06

    The degradation in the strength of napkin-ring (NR) joints bonded with an epoxy thermoset is evaluated in a humid environment. While adherend composition (stainless steel and aluminum) and surface preparation (polished, grit blasted, primed, coupling agent coated) do not affect virgin (time=0) joint strength, they can significantly affect the role of moisture on the strength of the joint. Adherend surface abrasion and corrosion processes are found to be key factors in determining the reliability of joint strength in humid environments. In cases where surface specific joint strength degradation processes are not active, decreases in joint strength can be accounted for by the glass transition temperature, Tg, depression of the adhesive associated with water sorption. Under these conditions, joint strength can be rejuvenated to virgin strength by drying. In addition, the decrease in joint strength associated with water sorption can be predicted by the Simplified Potential Energy Clock (SPEC) model by shifting the adhesive reference temperature, Tref, by the same amount as the Tg depression. When surface specific degradation mechanisms are active, they can reduce joint strength below that associated with adhesive Tg depression, and joint strength is not recoverable by drying. Furthermore, a critical relative humidity (or, potentially, critical water sorption concentration), below which the surface specific degradation does not occur, appears to exist for the polished stainless steel joints.

  10. Mechanisms of degradation in adhesive joint strength: Glassy polymer thermoset bond in a humid environment

    DOE PAGESBeta

    Kropka, Jamie Michael; Adolf, Douglas Brian; Spangler, Scott Wilmer; Austin, Kevin N.; Chambers, Robert S.

    2015-08-06

    The degradation in the strength of napkin-ring (NR) joints bonded with an epoxy thermoset is evaluated in a humid environment. While adherend composition (stainless steel and aluminum) and surface preparation (polished, grit blasted, primed, coupling agent coated) do not affect virgin (time=0) joint strength, they can significantly affect the role of moisture on the strength of the joint. Adherend surface abrasion and corrosion processes are found to be key factors in determining the reliability of joint strength in humid environments. In cases where surface specific joint strength degradation processes are not active, decreases in joint strength can be accounted formore » by the glass transition temperature, Tg, depression of the adhesive associated with water sorption. Under these conditions, joint strength can be rejuvenated to virgin strength by drying. In addition, the decrease in joint strength associated with water sorption can be predicted by the Simplified Potential Energy Clock (SPEC) model by shifting the adhesive reference temperature, Tref, by the same amount as the Tg depression. When surface specific degradation mechanisms are active, they can reduce joint strength below that associated with adhesive Tg depression, and joint strength is not recoverable by drying. Furthermore, a critical relative humidity (or, potentially, critical water sorption concentration), below which the surface specific degradation does not occur, appears to exist for the polished stainless steel joints.« less

  11. Laccase-Catalyzed Decolorization of Malachite Green: Performance Optimization and Degradation Mechanism

    PubMed Central

    Yang, Jie; Yang, Xiaodan; Lin, Yonghui; Ng, Tzi Bun; Lin, Juan; Ye, Xiuyun

    2015-01-01

    Malachite green (MG) was decolorized by laccase (LacA) of white-rot fungus Cerrena sp. with strong decolorizing ability. Decolorization conditions were optimized with response surface methodology. A highly significant quadratic model was developed to investigate MG decolorization with LacA, and the maximum MG decolorization ratio of 91.6% was predicted under the conditions of 2.8 U mL-1 LacA, 109.9 mg L-1 MG and decolorization for 172.4 min. Kinetic studies revealed the Km and kcat values of LacA toward MG were 781.9 mM and 9.5 s-1, respectively. UV–visible spectra confirmed degradation of MG, and the degradation mechanism was explored with liquid chromatography–mass spectrometry (LC-MS) analysis. Based on the LC-MS spectra of degradation products, LacA catalyzed MG degradation via two simultaneous pathways. In addition, the phytotoxicity of MG, in terms of inhibition on seed germination and seedling root elongation of Nicotiana tabacum and Lactuca sativa, was reduced after laccase treatment. These results suggest that laccase of Cerrena was effective in decolorizing MG and promising in bioremediation of wastewater in food and aquaculture industries. PMID:26020270

  12. Degradation mechanisms of geosmin and 2-MIB during UV photolysis and UV/chlorine reactions.

    PubMed

    Kim, Tae-Kyoung; Moon, Bo-Ram; Kim, Taeyeon; Kim, Moon-Kyung; Zoh, Kyung-Duk

    2016-11-01

    We conducted chlorination, UV photolysis, and UV/chlorin reactions to investigate the intermediate formation and degradation mechanisms of geosmin and 2-methylisoborneol (2-MIB) in water. Chlorination hardly removed geosmin and 2-MIB, while the UV/chlorine reaction at 254 nm completely removed geosmin and 2-MIB within 40 min and 1 h, respectively, with lesser removals of both compounds during UV photolysis. The kinetics during both UV photolysis and UV/chlorine reactions followed a pseudo first-order reaction. Chloroform was found as a chlorinated intermediate during the UV/chlorine reaction of both geosmin and 2-MIB. The pH affected both the degradation and chloroform production during the UV/chlorine reaction. The open ring and dehydration intermediates identified during UV/chlorine reactions were 1,4-dimethyl-adamantane, and 1,3-dimethyl-adamantane from geosmin, 2-methylenebornane, and 2-methyl-2-bornene from 2-MIB, respectively. Additionally, 2-methyl-3-pentanol, 2,4-dimethyl-1-heptene, 4-methyl-2-heptanone, and 1,1-dichloro-2,4-dimethyl-1-heptane were newly identified intermediates from UV/chlorine reactions of both geosmin and 2-MIB. These intermediates were degraded as the reaction progressed. We proposed possible degradation pathways during the UV photolysis and UV/chlorine reactions of both compounds using the identified intermediates. PMID:27494316

  13. Age-related macular degeneration and changes in the extracellular matrix

    PubMed Central

    Nita, Małgorzata; Strzałka-Mrozik, Barbara; Grzybowski, Andrzej; Mazurek, Urszula; Romaniuk, Wanda

    2014-01-01

    Age-related macular degeneration (AMD) is the leading cause of permanent, irreversible, central blindness (scotoma in the central visual field that makes reading and writing impossible, stereoscopic vision, recognition of colors and details) in patients over the age of 50 years in European and North America countries, and an important role is attributed to disorders in the regulation of the extracellular matrix (ECM). The main aim of this article is to present the crucial processes that occur on the level of Bruch’s membrane, with special consideration of the metalloproteinase substrates, metalloproteinase, and tissue inhibitor of metalloproteinase (TIMP). A comprehensive review of the literature was performed through MEDLINE and PubMed searches, covering the years 2005–2012, using the following keywords: AMD, extracellular matrix, metalloproteinases, tissue inhibitors of metalloproteinases, Bruch’s membrane, collagen, elastin. In the pathogenesis of AMD, a significant role is played by collagen type I and type IV; elastin; fibulin-3, -5, and -6; matrix metalloproteinase (MMP)-2, MMP-9, MMP-14, and MMP-1; and TIMP-3. Other important mechanisms include: ARMS2 and HTR1 proteins, the complement system, the urokinase plasminogen activator system, and pro-renin receptor activation. Continuous rebuilding of the extracellular matrix occurs in both early and advanced AMD, simultaneously with the dysfunction of retinal pigment epithelium (RPE) cells and endothelial cells. The pathological degradation or accumulation of ECM structural components are caused by impairment or hyperactivity of specific MMPs/TIMPs complexes, and is also endangered by the influence of other mechanisms connected with both genetic and environmental factors. PMID:24938626

  14. Age-Related Differences in Reaction Time Task Performance in Young Children

    ERIC Educational Resources Information Center

    Kiselev, Sergey; Espy, Kimberlay Andrews; Sheffield, Tiffany

    2009-01-01

    Performance of reaction time (RT) tasks was investigated in young children and adults to test the hypothesis that age-related differences in processing speed supersede a "global" mechanism and are a function of specific differences in task demands and processing requirements. The sample consisted of 54 4-year-olds, 53 5-year-olds, 59 6-year-olds,…

  15. Recent Advances in Berry Supplementation and Age-Related Cognitive Decline

    Technology Transfer Automated Retrieval System (TEKTRAN)

    To summarize recent findings and current concepts in the beneficial effects of berry consumption on brain function during aging. Berryfruit supplementation has continued to demonstrate efficacy in reversing age-related cognitive decline in animal studies. In terms of the mechanisms behind the effe...

  16. Fatty old hearts: role of cardiac lipotoxicity in age-related cardiomyopathy

    PubMed Central

    Drosatos, Konstantinos

    2016-01-01

    Age-related cardiomyopathy accounts for a significant part of heart failure cases. Imbalance of the energetic equilibrium of the heart along with mitochondrial dysfunction and impaired β-adrenergic receptor signaling contributes in the aggravation of cardiac function in the elderly. In this review article, studies that correlate cardiac aging with lipotoxicity are summarized. The involvement of inhibition of peroxisome proliferator-activated receptor-α, β-adrenergic receptor desensitization, and mitochondrial dysfunction as underlying mechanisms for the lipid-driven age-related cardiomyopathy are presented with the aim to indicate potential therapeutic targets for cardiac aging. PMID:27558317

  17. Fatty old hearts: role of cardiac lipotoxicity in age-related cardiomyopathy.

    PubMed

    Drosatos, Konstantinos

    2016-01-01

    Age-related cardiomyopathy accounts for a significant part of heart failure cases. Imbalance of the energetic equilibrium of the heart along with mitochondrial dysfunction and impaired β-adrenergic receptor signaling contributes in the aggravation of cardiac function in the elderly. In this review article, studies that correlate cardiac aging with lipotoxicity are summarized. The involvement of inhibition of peroxisome proliferator-activated receptor-α, β-adrenergic receptor desensitization, and mitochondrial dysfunction as underlying mechanisms for the lipid-driven age-related cardiomyopathy are presented with the aim to indicate potential therapeutic targets for cardiac aging. PMID:27558317

  18. Insight into the Mechanism of Graphene Oxide Degradation via the Photo-Fenton Reaction.

    PubMed

    Bai, Hao; Jiang, Wentao; Kotchey, Gregg P; Saidi, Wissam A; Bythell, Benjamin J; Jarvis, Jacqueline M; Marshall, Alan G; Robinson, Renã A S; Star, Alexander

    2014-05-15

    Graphene represents an attractive two-dimensional carbon-based nanomaterial that holds great promise for applications such as electronics, batteries, sensors, and composite materials. Recent work has demonstrated that carbon-based nanomaterials are degradable/biodegradable, but little work has been expended to identify products formed during the degradation process. As these products may have toxicological implications that could leach into the environment or the human body, insight into the mechanism and structural elucidation remain important as carbon-based nanomaterials become commercialized. We provide insight into a potential mechanism of graphene oxide degradation via the photo-Fenton reaction. We have determined that after 1 day of treatment intermediate oxidation products (with MW 150-1000 Da) were generated. Upon longer reaction times (i.e., days 2 and 3), these products were no longer present in high abundance, and the system was dominated by graphene quantum dots (GQDs). On the basis of FTIR, MS, and NMR data, potential structures for these oxidation products, which consist of oxidized polycyclic aromatic hydrocarbons, are proposed. PMID:24860637

  19. Insight into the Mechanism of Graphene Oxide Degradation via the Photo-Fenton Reaction

    PubMed Central

    2015-01-01

    Graphene represents an attractive two-dimensional carbon-based nanomaterial that holds great promise for applications such as electronics, batteries, sensors, and composite materials. Recent work has demonstrated that carbon-based nanomaterials are degradable/biodegradable, but little work has been expended to identify products formed during the degradation process. As these products may have toxicological implications that could leach into the environment or the human body, insight into the mechanism and structural elucidation remain important as carbon-based nanomaterials become commercialized. We provide insight into a potential mechanism of graphene oxide degradation via the photo-Fenton reaction. We have determined that after 1 day of treatment intermediate oxidation products (with MW 150–1000 Da) were generated. Upon longer reaction times (i.e., days 2 and 3), these products were no longer present in high abundance, and the system was dominated by graphene quantum dots (GQDs). On the basis of FTIR, MS, and NMR data, potential structures for these oxidation products, which consist of oxidized polycyclic aromatic hydrocarbons, are proposed. PMID:24860637

  20. Degradation mechanism of a low band gap polymer PTB7 by oxidation

    NASA Astrophysics Data System (ADS)

    Park, Soohyung; Jeong, Junkyeong; Lee, Hyunbok; Yi, Yeonjin

    Recently, the PCE of OPVs is at the 10% mark by using donor materials having a low band gap, such as poly(4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b']dithiophene-2,6-diyl-alt-3-fluoro-2-[(2-ethylhexyl)carbonyl]thieno[3,4-b]thiophene-4,6-diyl) (PTB7) and its analogues. In spite of the significant PCE improvement, the lifetime issue still remains open problem. To solve these technical limitations fundamentally, the degradation mechanism should be understood. It can be revealed by investigating the electronic structures of polymers with controlled exposure of oxygen, moisture and light. In this study, ultraviolet, X-ray and inverse photoelectron spectroscopy measurements were performed with step-by-step exposure of controlled oxygen, moisture and light to investigate the degradation mechanism of each polymer film. Theoretical calculations using density functional theory (DFT) were also performed to understand detailed degradation process. From the experimental results, we demonstrate that push-pull polymers are more sensitive to environmental conditions, compared with non-push-pull (conventional) polymers such as poly (3-hexylthiophene-2,5-diyl) (P3HT). In addition, we show high photo-oxidation of PTB7 is originated from the structural reason.

  1. [Research progress on the degradation mechanisms and restoration of riparian ecosystem].

    PubMed

    Huang, Kai; Guo, Huai-cheng; Liu, Yong; Yu, Ya-juan; Zhou, Feng

    2007-06-01

    Restoration and reconstruction of degraded riparian ecosystem caused by natural and anthropogenic disturbances is one of the important issues in restoration ecology and watershed ecology. The disturbances on riparian ecosystem include flow regime alteration, direct modification and watershed disturbance, which have different affecting mechanisms. Flow regime alteration affects riparian ecosystem by changing riparian soil humidity, oxidation-reduction potential, biotaliving environment, and sediment transfer; direct modification affects riparian vegetation diversity through human activities and exotic plants invasion; and watershed disturbance mainly manifests in the channel degradation, aggradation or widening, the lowering of groundwater table, and the modification in fluvial process. The assessment objects of riparian restoration are riparian ecosystem components, and the assessment indicators are shifted from ecological to synthetic indices. Riparian restoration should be based on the detailed understanding of the biological and physical processes which affect riparian ecosystem, and implemented by vegetation restoration and hydrological adjustment at watershed or landscape scale. To extend the research scales and objects and to apply interdisciplinary approaches should be the key points in the further studies on the degradation mechanisms and restoration of riparian ecosystem. PMID:17763745

  2. Towards understanding intrinsic degradation and breakdown mechanisms in SiOCH low-k dielectrics

    SciTech Connect

    Wu, C. De Wolf, I.; Li, Y.; Ciofi, I.; Kauerauf, Th.; Bömmels, J.; Tőkei, Zs.; Croes, K.

    2015-02-14

    The degradation and breakdown mechanisms of a SiOCH low-k material with k = 2.3 (25% porosity) and thicknesses ranging from 90 nm to 20 nm were investigated. By combining the time dependent dielectric breakdown data at positive/negative bias stress with the thickness scaling results, dielectric failure is proven to be intrinsic and not influenced by copper drift or metal barrier deposition induced dielectric damage. It is shown that stress induced leakage current (SILC) can be used as a measure of dielectric degradation. Therefore, low field lifetimes can be safely estimated using SILC extrapolation. Based on our results, both the impact damage model and the power law model have a good accuracy for low field lifetime prediction. Recovery and anneal experiments are used to study the physical nature causing the observed negative flatband voltage shifts in our metal-insulator-semiconductor planar capacitor structures, where hydrogen induced unstable fast and slow donor type interface states are hypothesized to be the root cause of the observed shifts. We suggest that atomic hydrogen is released from the dielectric during electron injection and migrates to the interfacial region. Our model is further supported by an observed irreversible SILC change during the recovery and anneal studies. The degradation mechanism proposed in this work, supported by the low field lifetime data, provides a feasible explanation for intrinsic low-k dielectric failure.

  3. Towards understanding intrinsic degradation and breakdown mechanisms in SiOCH low-k dielectrics

    NASA Astrophysics Data System (ADS)

    Wu, C.; Li, Y.; Ciofi, I.; Kauerauf, Th.; Bömmels, J.; De Wolf, I.; Tőkei, Zs.; Croes, K.

    2015-02-01

    The degradation and breakdown mechanisms of a SiOCH low-k material with k = 2.3 (25% porosity) and thicknesses ranging from 90 nm to 20 nm were investigated. By combining the time dependent dielectric breakdown data at positive/negative bias stress with the thickness scaling results, dielectric failure is proven to be intrinsic and not influenced by copper drift or metal barrier deposition induced dielectric damage. It is shown that stress induced leakage current (SILC) can be used as a measure of dielectric degradation. Therefore, low field lifetimes can be safely estimated using SILC extrapolation. Based on our results, both the impact damage model and the power law model have a good accuracy for low field lifetime prediction. Recovery and anneal experiments are used to study the physical nature causing the observed negative flatband voltage shifts in our metal-insulator-semiconductor planar capacitor structures, where hydrogen induced unstable fast and slow donor type interface states are hypothesized to be the root cause of the observed shifts. We suggest that atomic hydrogen is released from the dielectric during electron injection and migrates to the interfacial region. Our model is further supported by an observed irreversible SILC change during the recovery and anneal studies. The degradation mechanism proposed in this work, supported by the low field lifetime data, provides a feasible explanation for intrinsic low-k dielectric failure.

  4. Mechanism of Calcium Lactate Facilitating Phytic Acid Degradation in Soybean during Germination.

    PubMed

    Hui, Qianru; Yang, Runqiang; Shen, Chang; Zhou, Yulin; Gu, Zhenxin

    2016-07-13

    Calcium lactate facilitates the growth and phytic acid degradation of soybean sprouts, but the mechanism is unclear. In this study, calcium lactate (Ca) and calcium lactate with lanthanum chloride (Ca+La) were used to treat soybean sprouts to reveal the relevant mechanism. Results showed that the phytic acid content decreased and the availability of phosphorus increased under Ca treatment. This must be due to the enhancement of enzyme activity related to phytic acid degradation. In addition, the energy metabolism was accelerated by Ca treatment. The energy status and energy metabolism-associated enzyme activity also increased. However, the transmembrane transport of calcium was inhibited by La(3+) and concentrated in intercellular space or between the cell wall and cell membrane; thus, Ca+La treatment showed reverse results compared with those of Ca treatment. Interestingly, gene expression did not vary in accordance with their enzyme activity. These results demonstrated that calcium lactate increased the rate of phytic acid degradation by enhancing growth, phosphorus metabolism, and energy metabolism. PMID:27324823

  5. Determination of the in vivo degradation mechanism of PEGDA hydrogels3

    PubMed Central

    Browning, M.B.; Cereceres, S.N.; Luong, P.T.; Cosgriff-Hernandez, E.M.

    2014-01-01

    Poly(ethylene glycol) (PEG) hydrogels are one of the most extensively utilized biomaterials systems due to their established biocompatibility and highly tunable properties. It is widely acknowledged that traditional acrylate-derivatized PEG (PEGDA) hydrogels are susceptible to slow degradation in vivo and are therefore unsuitable for long-term implantable applications. However, there is speculation whether the observed degradation is due to hydrolysis of endgroup acrylate esters or oxidation of the ether backbone both of which are possible in the foreign body response to implanted devices. PEG diacrylamide (PEGDAA) is a polyether-based hydrogel system with similar properties to PEGDA but with amide linkages in place of the acrylate esters. This provides a hydrolytically-stable control that can be used to isolate the relative contributions of hydrolysis and oxidation to the in vivo degradation of PEGDA. Here we show that PEGDAA hydrogels remained stable over 12 weeks of subcutaneous implantation in a rat model while PEGDA hydrogels underwent significant degradation as indicated by both increased swelling ratio and decreased modulus. As PEGDA and PEGDAA have similar susceptibility to oxidation, these results demonstrate for the first time that the primary in vivo degradation mechanism of PEGDA is hydrolysis of the endgroup acrylate ester. Additionally, the maintenance of PEGDAA hydrogel properties in vivo indicates their suitability for long-term implants. These studies serve to elucidate key information about a widely used biomaterial system to allow for better implantable device design and to provide a biostable replacement option for PEGDA in applications that require long-term stability. PMID:24464985

  6. Influence of Age-Related Versus Non-Age-Related Renal Dysfunctionon Survival in Patients with Left Ventricular Dysfunction

    PubMed Central

    Testani, Jeffrey M.; Brisco, Meredith A.; Han, Gang; Laur, Olga; Kula, Alexander J.; Cheng, Susan J.; Tang, W. H. Wilson; Parikh, Chirag R.

    2013-01-01

    Normal aging results in a predictable decline in glomerular filtration rate (GFR) and low GFR is associated with worsened survival. If this survival disadvantage is directly caused by the low GFR, as opposed to the disease causing the low GFR, the risk should be similar regardless of the underlying mechanism. Our objective was to determine if age related declines in estimated GFR (eGFR) carry the same prognostic importance as disease attributable losses in patients with ventricular dysfunction. We analyzed the Studies Of Left Ventricular Dysfunction (SOLVD) limited data set (n=6337). The primary analysis focused on determining if the eGFR mortality relationship differed by the extent the eGFR was consistent with normal ageing. Mean eGFR was 65.7 ± 19.0ml/min/1.73m2. Across the range of age in the population (27 to 80 years), baseline eGFR decreased by 0.67 ml/min/1.73m2 per year (95% CI 0.63 to 0.71). The risk of death associated with eGFR was strongly modified by the degree to which the low eGFR could be explained by aging (p interaction <0.0001). For example, in a model incorporating the interaction, uncorrected eGFR was no longer significantly related to mortality (adjusted HR=1.0 per 10 ml/min/1.73m2, 95% CI 0.97–1.1, p=0.53) whereas a disease attributable decrease in eGFR above the median carried significant risk (adjusted HR=2.8, 95% CI 1.6–4.7, p<0.001). In conclusion, in the setting of LV dysfunction, renal dysfunction attributable to normal aging had a limited risk for mortality, suggesting that the mechanism underlying renal dysfunction is critical in determining prognosis. PMID:24216124

  7. Peroxisome homeostasis: Mechanisms of division and selective degradation of peroxisomes in mammals.

    PubMed

    Honsho, Masanori; Yamashita, Shun-ichi; Fujiki, Yukio

    2016-05-01

    Peroxisome number and quality are maintained by its biogenesis and turnover and are important for the homeostasis of peroxisomes. Peroxisomes are increased in number by division with dynamic morphological changes including elongation, constriction, and fission. In the course of peroxisomal division, peroxisomal morphogenesis is orchestrated by Pex11β, dynamin-like protein 1 (DLP1), and mitochondrial fission factor (Mff). Conversely, peroxisome number is reduced by its degradation. Peroxisomes are mainly degraded by pexophagy, a type of autophagy specific for peroxisomes. Upon pexophagy, an adaptor protein translocates on peroxisomal membrane and connects peroxisomes to autophagic machineries. Molecular mechanisms of pexophagy are well studied in yeast systems where several specific adaptor proteins are identified. Pexophagy in mammals also proceeds in a manner dependent on adaptor proteins. In this review, we address the recent progress in studies on peroxisome morphogenesis and pexophagy. PMID:26434997

  8. Mechanical degradation of cold-worked 304 stainless steel in salt spray environments

    NASA Astrophysics Data System (ADS)

    Chiang, M. F.; Hsu, H. H.; Young, M. C.; Huang, J. Y.

    2012-03-01

    Saline corrosion is one of the major degradation mechanisms for stainless steel 304 (SS304) spent fuel canisters during the dry storage period. Slow strain rate tensile tests (SSRT) were conducted to determine the tensile strength and notched tensile strength (NTS) of cold-rolled SS304 in 0.5 and 5 wt% saline spray environments at 358 K. The YS and UTS of the steels did not decrease significantly in the 0.5 wt% saline spray environment, but a remarkable decrease in elongation was observed in the 5 wt% saline spray. Furthermore, a notch could exacerbate the saline corrosion degradation and aggravate the hydrogen embrittlement of SS304. The cold work of higher degrees could slightly improve SCC resistance of the SS304 under the lower chloride containing spray. However, the NaCl concentration is a crucial factor affecting the SCC susceptibility of SS304.

  9. Can DRYAD explain age-related associative memory deficits?

    PubMed

    Smyth, Andrea C; Naveh-Benjamin, Moshe

    2016-02-01

    A recent interesting theoretical account of aging and memory judgments, the DRYAD (density of representations yields age-related deficits; Benjamin, 2010; Benjamin, Diaz, Matzen, & Johnson, 2012), attributes the extensive findings of disproportional age-related deficits in memory for source, context, and associations, to a global decline in memory fidelity. It is suggested that this global deficit, possibly due to a decline in attentional processes, is moderated by weak representation of contextual information to result in disproportional age-related declines. In the current article, we evaluate the DRYAD model, comparing it to specific age-related deficits theories, in particular, the ADH (associative deficit hypothesis, Naveh-Benjamin, 2000). We question some of the main assumptions/hypotheses of DRYAD in light of data reported in the literature, and we directly assess the role of attention in age-related deficits by manipulations of divided attention and of the instructions regarding what to pay attention to in 2 experiments (one from the literature and a new one). The results of these experiments fit the predictions of the ADH and do not support the main assumption/hypotheses of DRYAD. PMID:25961878

  10. Parainflammation, chronic inflammation, and age-related macular degeneration.

    PubMed

    Chen, Mei; Xu, Heping

    2015-11-01

    Inflammation is an adaptive response of the immune system to noxious insults to maintain homeostasis and restore functionality. The retina is considered an immune-privileged tissue as a result of its unique anatomic and physiologic properties. During aging, the retina suffers from a low-grade chronic oxidative insult, which sustains for decades and increases in level with advancing age. As a result, the retinal innate-immune system, particularly microglia and the complement system, undergoes low levels of activation (parainflammation). In many cases, this parainflammatory response can maintain homeostasis in the healthy aging eye. However, in patients with age-related macular degeneration, this parainflammatory response becomes dysregulated and contributes to macular damage. Factors contributing to the dysregulation of age-related retinal parainflammation include genetic predisposition, environmental risk factors, and old age. Dysregulated parainflammation (chronic inflammation) in age-related macular degeneration damages the blood retina barrier, resulting in the breach of retinal-immune privilege, leading to the development of retinal lesions. This review discusses the basic principles of retinal innate-immune responses to endogenous chronic insults in normal aging and in age-related macular degeneration and explores the difference between beneficial parainflammation and the detrimental chronic inflammation in the context of age-related macular degeneration. PMID:26292978

  11. Mechanical, degradation and cytocompatibility properties of magnesium coated phosphate glass fibre reinforced polycaprolactone composites.

    PubMed

    Liu, Xiaoling; Hasan, Muhammad S; Grant, David M; Harper, Lee T; Parsons, Andrew J; Palmer, Graham; Rudd, Chris D; Ahmed, Ifty

    2014-11-01

    Retention of mechanical properties of phosphate glass fibre reinforced degradable polyesters such as polycaprolactone and polylactic acid in aqueous media has been shown to be strongly influenced by the integrity of the fibre/polymer interface. A previous study utilising 'single fibre' fragmentation tests found that coating with magnesium improved the fibre and matrix interfacial shear strength. Therefore, the aim of this study was to investigate the effects of a magnesium coating on the manufacture and characterisation of a random chopped fibre reinforced polycaprolactone composite. Short chopped strand non-woven phosphate glass fibre mats were sputter coated with degradable magnesium to manufacture phosphate glass fibre/polycaprolactone composites. The degradation behaviour (water uptake, mass loss and pH change of the media) of these polycaprolactone composites as well as of pure polycaprolactone was investigated in phosphate buffered saline. The Mg coated fibre reinforced composites revealed less water uptake and mass loss during degradation compared to the non-coated composites. The cations released were also explored and a lower ion release profile for all three cations investigated (namely Na(+), Mg(2+) and Ca(2+)) was seen for the Mg coated composite samples. An increase of 17% in tensile strength and 47% in tensile modulus was obtained for the Mg coated composite samples. Both flexural and tensile properties were investigated and a higher retention of mechanical properties was obtained for the Mg coated fibre reinforced composite samples up to 10 days immersion in PBS. Cytocompatibility study showed both composite samples (coated and non-coated) had good cytocompatibility with human osteosarcoma cell line. PMID:25028389

  12. Region-dependent aggrecan degradation patterns in the rat intervertebral disc are affected by mechanical loading in vivo

    PubMed Central

    Iatridis, James C.; Godburn, Karolyn; Wuertz, Karin; Alini, Mauro; Roughley, Peter J.

    2010-01-01

    Structured Abstract Study Design Immunoblotting study to evaluate aggrecan degradation patterns in rat intervertebral discs(IVDs) subjected to mechanical overload. Objective To evaluate the effects of in vivo dynamic compression overloading on aggrecan degradation products associated with matrix metalloproteinase(MMP) and aggrecanase activity in different regions of the IVD. Summary of Background Data Aggrecan cleavage at the MMP and aggrecanase sites are important events in human IVD aging, with distinct cleavage patterns in the annulus and nucleus regions. No such information is available on regional variations in rat IVDs, nor on how such cleavage is affected by mechanical loading. Methods Sprague-Dawley rats were instrumented with an Ilizarov-type device and subjected to dynamic compression (1 MPa and 1 Hz for 8 hours per day for 8 weeks). Control, sham, and overloaded IVDs were separated by disc region and analyzed for aggrecan degradation products using immunoblotting techniques with antibodies specific for the aggrecanase and MMP cleavage sites in the interglobular domain of aggrecan. Results Control IVDs exhibited strong regional variation in aggrecan degradation patterns with minimal degradation products being present in the nucleus pulposus(NP), degradation products associated with aggrecanase cleavage predominating in the inner annulus fibrosus(AF), and degradation products associated with MMP cleavage predominating in the outer annulus fibrosus. Dynamic compression overloading increased the amount of aggrecan degradation products associated with MMP cleavage particularly in the AF but also in the NP. Degradation profiles of sham IVDs were similar to control. Conclusions Aggrecan G1 regions resulting from proteolysis were found to have a strong regionally-specific pattern in the rat IVD, which was altered under excessive loading. The shift from aggrecanase to MMP-induced degradation products with dynamic compression overloading suggests that protein

  13. Effect of hydrogen on degradation mechanism of zirconium: A molecular dynamics study

    NASA Astrophysics Data System (ADS)

    Chakraborty, Poulami; Moitra, Amitava; Saha-Dasgupta, Tanusri

    2015-11-01

    Using large scale molecular dynamics simulation, we investigate the deleterious effect of hydrogen in Zr. We consider both dilute and concentrated limit of H. In the dilute and concentrated H limits, we study the effect of 1-5 atomic percentage of hydrogen, and that of ε-ZrH2 precipitate having 5-10 nm diameters, respectively. From the stress-strain curves and micro-structure analysis at different strain values, we characterize the deformation behavior and correlate our result with previously reported mechanisms. We show hydrogen atoms in dilute limit help in dislocation multiplication, following the hydrogen-enhanced localized plasticity mechanism. In the concentrated limit, on the other hand, dislocations and cracks nucleate from precipitate-matrix interface, indicating the decohesion mechanism as primary method for Zr degradation. These findings are corroborated with a nucleation and growth model as expressed in Kolmogorov-Johnson-Mehl-Avrami equation.

  14. Investigation of accelerated stress factors and failure/degradation mechanisms in terrestrial solar cells

    NASA Technical Reports Server (NTRS)

    Lathrop, J. W.

    1983-01-01

    Results of an ongoing research program into the reliability of terrestrial solar cells are presented. Laboratory accelerated testing procedures are used to identify failure/degradation modes which are then related to basic physical, chemical, and metallurgical phenomena. In the most recent tests, ten different types of production cells, both with and without encapsulation, from eight different manufacturers were subjected to a variety of accelerated tests. Results indicated the presence of a number of hitherto undetected failure mechanisms, including Schottky barrier formation at back contacts and loss of adhesion of grid metallization. The mechanism of Schottky barrier formation is explained by hydrogen, formed by the dissociation of water molecules at the contact surface, diffusing to the metal semiconductor interface. This same mechanism accounts for the surprising increase in sensitivity to accelerated stress conditions that was observed in some cells when encapsulated.

  15. Glutamatergic treatment strategies for age-related memory disorders.

    PubMed

    Müller, W E; Scheuer, K; Stoll, S

    1994-01-01

    Age-related changes of N-methyl-D-aspartate (NMDA) receptors have been found in cortical areas and in the hippocampus of many species. On the basis of a variety of experimental observations it has been suggested that the decrease of NMDA receptor density might be one of the causative factors of the cognitive decline with aging. Based on these findings several strategies have been developed to improve cognition by compensating the NMDA receptor deficits in aging. The most promising approaches are the indirect activation of glutamatergic neurotransmission by agonists of the glycine site or the restoration of the age-related deficit of receptor density by several nootropics. PMID:7997073

  16. Irradiation imposed degradation of the mechanical and electrical properties of electrical insulation for future accelerator magnets

    SciTech Connect

    Polinski, J.; Chorowski, M.; Bogdan, P.; Strychalski, M.; Rijk, G. de

    2014-01-27

    Future accelerators will make extensive use of superconductors made of Nb{sub 3}Sn, which allows higher magnetic fields than NbTi. However, the wind-and-react technology of Nb{sub 3}Sn superconducting magnet production makes polyimide Kapton® non applicable for the coils' electrical insulation. A Nb{sub 3}Sn technology compatible insulation material should be characterized by high radiation resistivity, good thermal conductivity, and excellent mechanical properties. Candidate materials for the electrical insulation of future accelerator's magnet coils have to be radiation certified with respect to potential degradation of their electrical, thermal, and mechanical properties. This contribution presents procedures and results of tests of the electrical and mechanical properties of DGEBA epoxy + D400 hardener, which is one of the candidates for the electrical insulation of future magnets. Two test sample types have been used to determine the material degradation due to irradiation: a untreated one (unirradiated) and irradiated at 77 K with 11 kGy/min intense, 4MeV energy electrons beam to a total dose of 50 MGy.

  17. Mechanism of strength degradation for hot corrosion of alpha-SiC

    NASA Technical Reports Server (NTRS)

    Smialek, J. L.; Jacobson, N. S.

    1984-01-01

    Sintered alpha SiC was corroded by thin films of Na2SO4 and Na2CO3 molten salts at 1000%. This hot corrosion attack reduced room temperature strengths by as much as 50%. Strength degradation was porportional to the degree and uniformity of corrosion pitting attack as controlled by the chemistry of the molten salt. Extensive fractography identified corrosion pits as the most prevalent source of failure. A fracture mechanics treatment of the strength/pit depth relationship produced an average K sub IC equal to 2.6 MPa sub m 1/2, which is consistent with published values.

  18. Chemical durability and degradation mechanisms of HT9 based alloy waste forms with variable Zr content

    SciTech Connect

    Olson, L. N.

    2015-10-30

    In Corrosion studies were undertaken on alloy waste forms that can result from advanced electrometallurgical processing techniques to better classify their durability and degradation mechanisms. The waste forms were based on the RAW3-(URe) composition, consisting primarily of HT9 steel and other elemental additions to simulate nuclear fuel reprocessing byproducts. The solution conditions of the corrosion studies were taken from an electrochemical testing protocol, and meant to simulate conditions in a repository. The alloys durability was examined in alkaline and acidic brines.

  19. Anticataractogenesis Mechanisms of Curcumin and a Comparison of Its Degradation Products: An in Vitro Study.

    PubMed

    Liao, Jiahn-Haur; Huang, Yi-Shiang; Lin, Yu-Ching; Huang, Fu-Yung; Wu, Shih-Hsiung; Wu, Tzu-Hua

    2016-03-16

    Curcumin (Cur) exhibits anticataractogenesis activity. This study aimed to compare the activities of Cur with those of its degradation products in a series of in vitro lens protein turbidity assays. The results show that Cur (200 μM) ameliorates selenite-induced crystallin aggregation, and the mean OD value was 0.10 ± 0.02 (p < 0.05), which was significantly different from controls (0.15 ± 0.01) after incubating for 3 days. However, Cur did not significantly inhibit calcium-induced proteolysis after incubating for 3 days. Such results were supported by isothermal titration calorimetry observation that Cur binds with selenite but not with calcium. Presence of Cur and the degradation products examined (ferulic acid, cinnamic acid, vanillin, and vanillic acid) indicates significantly protective activities on lens γ-crystallins after UVC exposure for 3 h. Among the compounds examined, only ferulic acid exhibited a significant inhibitory effect against UVB-induced turbidity with a mean OD of 0.32 ± 0.01 (p < 0.05), which was significantly different from controls (0.49 ± 0.02). The previously reported anticataract effects of Cur may stem not only from Cur but also from its degradation products through various cataractogenesis mechanisms in vitro. PMID:26905955

  20. Experimental approach to evaluating environmental degradation mechanisms in bisphenol-A polycarbonate films on metallic substrates

    SciTech Connect

    Webb, J.D.

    1983-11-01

    A technique is presented for in situ study of degradative changes in bisphenol-A polycarbonate (BPA-PC) coatings on metallic substrates. The technique uses a controlled environmental exposure chamber in conjunction with a Fourier transform infrared spectrophotometer. The chamber design permits collection of infrared reflection-absorbance (IR-RA) spectra from a sample undergoing exposure to controlled ultraviolet radiation, gas mixtures, and temperatures. A technique for relating the IR-RA band heights measured with the apparatus to the concentration of polymeric functional groups and reaction products in the coatings is presented. Comparison of the results of uv and ir spectroscopy with those obtained using gel permeation chromatography to determine changes in the molecular weight distribution of the BPA-PC films following exposure enabled identification of several degradation pathways. The major mechanisms, in order of importance, appear to be the first and second photo-Fries rearrangements at carbonyl, and chain scission, also at carbonyl. The quantum yield of the first photo-Fries reaction product, measured using IR-RA, was 0.020+-0.004. Some evidence for photooxidation of the BPA-PC methyl functional groups is also presented. The techniques presented should be applicable to the study of both surface and interfacial degradation, especially with samples having polymer film thicknesses within the optimum range (0.1 to 1.0 ..mu..m).

  1. Studies on adsorption, reaction mechanisms and kinetics for photocatalytic degradation of CHD, a pharmaceutical waste.

    PubMed

    Sarkar, Santanu; Bhattacharjee, Chiranjib; Curcio, Stefano

    2015-11-01

    The photocatalytic degradation of chlorhexidine digluconate (CHD), a disinfectant and topical antiseptic and adsorption of CHD catalyst surface in dark condition has been studied. Moreover, the value of kinetic parameters has been measured and the effect of adsorption on photocatalysis has been investigated here. Substantial removal was observed during the photocatalysis process, whereas 40% removal was possible through the adsorption route on TiO2 surface. The parametric variation has shown that alkaline pH, ambient temperature, low initial substrate concentration, high TiO2 loading were favourable, though at a certain concentration of TiO2 loading, photocatalytic degradation efficiency was found to be maximum. The adsorption study has shown good confirmation with Langmuir isotherm and during the reaction at initial stage, it followed pseudo-first-order reaction, after that Langmuir Hinshelwood model was found to be appropriate in describing the system. The present study also confirmed that there is a significant effect of adsorption on photocatalytic degradation. The possible mechanism for adsorption and photocatalysis has been shown here and process controlling step has been identified. The influences of pH and temperature have been explained with the help of surface charge distribution of reacting particles and thermodynamic point of view respectively. PMID:25956186

  2. Cycling stability and degradation mechanism of LiMnPO4 based electrodes

    NASA Astrophysics Data System (ADS)

    Moskon, J.; Pivko, M.; Jerman, I.; Tchernychova, E.; Logar, N. Zabukovec; Zorko, M.; Selih, V. S.; Dominko, R.; Gaberscek, M.

    2016-01-01

    Long term stability of LiMnPO4 particles with a crystallite size between ˜20 and 50 nm covered with a dense native carbon coating (14 wt.%) is demonstrated. More than 500 cycles at a rate of C/20, in the potential window of 2.7-4.5 V and a temperature of 55 °C were achieved. During most of the cycling the average capacity decay was less than 0.06% per cycle. After about 500 cycles a sudden capacity drop was observed. Degradation processes in various stages of cycling were thoroughly examined using a range of techniques. Severe surface film formation, manganese dissolution and degradation of LixMnPO4 accompanied by formation of Li4P2O7 were clearly identified. The good long term stability seems to be due to dense, protective carbon coating. Decomposition is most likely initiated at local defects in the microstructure of pyrolytic carbon coating around LiMnPO4 particles. In addition to known degradation mechanisms of LiMnPO4 we observed pronounced gradual amorphization of the olivine crystallites during long-term cycling at 55 °C. Finally, changes in morphology of the carbon black additive after prolonged cycling are reported and commented.

  3. Degradation mechanisms of nylon separator materials for a nickel-cadmium cell in KOH electrolytes

    SciTech Connect

    Lim, H.S.; Margerum, J.D.; Verzwyvelt, S.A.; Lackner, A.M.; Knechtli, R.C.

    1989-03-01

    Degradation reactions of a nylon 6 battery separator material have been studied in 4-34% aqueous KOH electrolytes at 35/sup 0/-110/sup 0/C. In a Ni/Cd cell, this degradation involves a slow hydrolysis reaction followed by fast electrochemical oxidations of the hydrolysis reaction products. Arrhenius activation energy of the hydrolysis reaction in 34% KOH was 20.0 +- 0.3 kcal/mole. A plot of the hydrolysis rate at 100/sup 0/C vs. hydroxyl ion concentration gave a rate maximum at about 16% KOH, and the mechanism for this effect is discussed. Electrochemical oxidations of the hydrolysis product, 6-aminocaproate ion, appear to proceed rapidly in several sequential steps at a nickel oxide electrode. In a Ni/Cd cell, the combination of nylon separator hydrolysis followed by electrochemical oxidation of the products can seriously degrade the battery lifetime. The rate of the hydrolysis of nylon 66 separator material was approximately one half of that of the nylon 6 material.

  4. Ozonation of Cationic Red X-GRL in aqueous solution: degradation and mechanism.

    PubMed

    Zhao, Weirong; Shi, Huixiang; Wang, Dahui

    2004-12-01

    Ozonation of the azo dye Cationic Red X-GRL was investigated in a bubble column reactor at varying operating parameters such as oxygen flow rate, temperature, initial Cationic Red X-GRL concentration, and pH. The conversion of dye increased with the increasing of pH and oxygen flow rate. As the reaction rate constant and the volumetric mass transfer coefficient increase while the ozone equilibrium concentration decreases with the temperature, there is a minimum conversion of dye at 25 degrees C. The increasing of initial dye concentration leads to a decreasing conversion of dye while the ozonation rate increases. The formation of intermediates and the variation of pH, TOC, and nitrate ion during ozonation were investigated by the use of some analytical instruments such as GC/MS, GC, and IC. The intermediates of weak organic acids lower the pH value of the solution. The probable degradation mechanism of the Cationic Red X-GRL in aqueous solution was deliberated with the aid of Molecular Orbital calculations. The N(12)-C(13) site in Cationic Red X-GRL, instead of the N(6)-N(7) site, is found to be the principal site for ozone cycloaddition in the degradation processes. During the degradation process, among the six nitrogen atoms of Cationic Red X-GRL, one is transferred into a nitrate ion, one is converted into an amine compound, and the remaining four are transformed into two molecules of nitrogen. PMID:15504479

  5. Impact of lipid-induced degradation on the mechanical properties of ultra-high molecular weight polyethylene for joint replacements.

    PubMed

    Sakoda, Hideyuki; Niimi, Shingo

    2016-01-01

    Gamma or electron beam irradiation of ultra-high molecular weight polyethylene (UHMWPE) used in artificial joints for sterilization and/or crosslinking purposes generates free radicals in the material, which causes long-term oxidative degradation of UHMWPE. Recently, another mechanism for the degradation of UHMWPE by the absorption of lipids during in vivo clinical use was proposed. However, knowledge on lipid-induced degradation is quite limited, compared with that on radical-induced degradation. In this study, lipid-induced degradation was simulated using squalene absorption and subsequent accelerated aging, and its impact on the mechanical properties of UHMWPE was evaluated. The simulated lipid-induced degradation caused an increased elastic modulus and decreased elongation with maximum degradation at the surfaces. These results imply that degradation of UHMWPE may occur during in vivo long-term use, even if free radicals are completely eliminated. Therefore, further investigation is required to clarify the impact of lipid-induced degradation on clinical outcomes, such as the wear and fatigue characteristics of UHMWPE components. PMID:26340645

  6. Stability and Degradation Mechanisms of Radiation-Grafted Polymer Electrolyte Membranes for Water Electrolysis.

    PubMed

    Albert, Albert; Lochner, Tim; Schmidt, Thomas J; Gubler, L

    2016-06-22

    Radiation-grafted membranes are a promising alternative to commercial membranes for water electrolyzers, since they exhibit lower hydrogen crossover and area resistance, better mechanical properties, and are of potentially lower cost than perfluoroalkylsulfonic acid membranes, such as Nafion. Stability is an important factor in view of the expected lifetime of 40 000 h or more of an electrolyzer. In this study, combinations of styrene (St), α-methylstyrene (AMS), acrylonitrile (AN), and 1,3-diisopropenylbenzene (DiPB) are cografted into 50 μm preirradiated poly(ethylene-co-tetrafluoroethylene) (ETFE) base film, followed by sulfonation to produce radiation-grafted membranes. The stability of the membranes with different monomer combinations is compared under an accelerated stress test (AST), and the degradation mechanisms are investigated. To mimic the conditions in an electrolyzer, in which the membrane is always in contact with liquid water at elevated temperature, the membranes are immersed in water for 5 days at 90 °C, so-called thermal stress test (TST). In addition to testing in air atmosphere tests are also carried out under argon to investigate the effect of the absence of oxygen. The water is analyzed with UV-vis spectroscopy and ion chromatography. The ion exchange capacity (IEC), swelling degree, and Fourier transform infrared (FTIR) spectra of the membranes are compared before and after the test. Furthermore, energy-dispersive X-ray (EDX) spectroscopic analysis of the membrane cross-section is performed. Finally, the influence of the TST to the membrane area resistance and hydrogen crossover is measured. The stability increases along the sequence St/AN, St/AN/DiPB, AMS/AN, and AMS/AN/DiPB grafted membrane. The degradation at the weak-link, oxygen-induced degradation, and hydrothermal degradation are proposed in addition to the "swelling-induced detachment" reported in the literature. By mitigating the possible paths of degradation, the AMS

  7. Dizziness and Imbalance in the Elderly: Age-related Decline in the Vestibular System.

    PubMed

    Iwasaki, Shinichi; Yamasoba, Tatsuya

    2015-02-01

    Dizziness and imbalance are amongst the most common complaints in older people, and are a growing public health concern since they put older people at a significantly higher risk of falling. Although the causes of dizziness in older people are multifactorial, peripheral vestibular dysfunction is one of the most frequent causes. Benign paroxysmal positional vertigo is the most frequent form of vestibular dysfunction in the elderly, followed by Meniere's disease. Every factor associated with the maintenance of postural stability deteriorates during aging. Age-related deterioration of peripheral vestibular function has been demonstrated through quantitative measurements of the vestibulo-ocular reflex with rotational testing and of the vestibulo-collic reflex with testing of vestibular evoked myogenic potentials. Age-related decline of vestibular function has been shown to correlate with the age-related decrease in the number of vestibular hair cells and neurons. The mechanism of age-related cellular loss in the vestibular endorgan is unclear, but it is thought that genetic predisposition and cumulative effect of oxidative stress may both play an important role. Since the causes of dizziness in older people are multi-factorial, management of this disease should be customized according to the etiologies of each individual. Vestibular rehabilitation is found to be effective in treating both unilateral and bilateral vestibular dysfunction. Various prosthetic devices have also been developed to improve postural balance in older people. Although there have been no medical treatments improving age-related vestibular dysfunction, new medical treatments such as mitochondrial antioxidants or caloric restriction, which have been effective in preventing age-related hearing loss, should be ienvestigated in the future. PMID:25657851

  8. Dizziness and Imbalance in the Elderly: Age-related Decline in the Vestibular System

    PubMed Central

    Iwasaki, Shinichi; Yamasoba, Tatsuya

    2015-01-01

    Dizziness and imbalance are amongst the most common complaints in older people, and are a growing public health concern since they put older people at a significantly higher risk of falling. Although the causes of dizziness in older people are multifactorial, peripheral vestibular dysfunction is one of the most frequent causes. Benign paroxysmal positional vertigo is the most frequent form of vestibular dysfunction in the elderly, followed by Meniere’s disease. Every factor associated with the maintenance of postural stability deteriorates during aging. Age-related deterioration of peripheral vestibular function has been demonstrated through quantitative measurements of the vestibulo-ocular reflex with rotational testing and of the vestibulo-collic reflex with testing of vestibular evoked myogenic potentials. Age-related decline of vestibular function has been shown to correlate with the age-related decrease in the number of vestibular hair cells and neurons. The mechanism of age-related cellular loss in the vestibular endorgan is unclear, but it is thought that genetic predisposition and cumulative effect of oxidative stress may both play an important role. Since the causes of dizziness in older people are multi-factorial, management of this disease should be customized according to the etiologies of each individual. Vestibular rehabilitation is found to be effective in treating both unilateral and bilateral vestibular dysfunction. Various prosthetic devices have also been developed to improve postural balance in older people. Although there have been no medical treatments improving age-related vestibular dysfunction, new medical treatments such as mitochondrial antioxidants or caloric restriction, which have been effective in preventing age-related hearing loss, should be ienvestigated in the future. PMID:25657851

  9. Differing mechanisms of simple nitrile formation on glucosinolate degradation in Lepidium sativum and Nasturtium officinale seeds.

    PubMed

    Williams, David J; Critchley, Christa; Pun, Sharon; Chaliha, Mridusmita; O'Hare, Timothy J

    2009-01-01

    Glucosinolates are sulphur-containing glycosides found in brassicaceous plants that can be hydrolysed enzymatically by plant myrosinase or non-enzymatically to form primarily isothiocyanates and/or simple nitriles. From a human health perspective, isothiocyanates are quite important because they are major inducers of carcinogen-detoxifying enzymes. Two of the most potent inducers are benzyl isothiocyanate (BITC) present in garden cress (Lepidium sativum), and phenylethyl isothiocyanate (PEITC) present in watercress (Nasturtium officinale). Previous studies on these salad crops have indicated that significant amounts of simple nitriles are produced at the expense of the isothiocyanates. These studies also suggested that nitrile formation may occur by different pathways: (1) under the control of specifier protein in garden cress and (2) by an unspecified, non-enzymatic path in watercress. In an effort to understand more about the mechanisms involved in simple nitrile formation in these species, we analysed their seeds for specifier protein and myrosinase activities, endogenous iron content and glucosinolate degradation products after addition of different iron species, specific chelators and various heat treatments. We confirmed that simple nitrile formation was predominantly under specifier protein control (thiocyanate-forming protein) in garden cress seeds. Limited thermal degradation of the major glucosinolate, glucotropaeolin (benzyl glucosinolate), occurred when seed material was heated to >120 degrees C. In the watercress seeds, however, we show for the first time that gluconasturtiin (phenylethyl glucosinolate) undergoes a non-enzymatic, iron-dependent degradation to a simple nitrile. On heating the seeds to 120 degrees C or greater, thermal degradation of this heat-labile glucosinolate increased simple nitrile levels many fold. PMID:19747700

  10. [Photocatalytic degradation kinetics of perfluorooctanoic acid (PFOA) in TiO2 dispersion and its mechanism].

    PubMed

    Li, Ming-Jie; Yu, Ze-Bin; Chen, Ying; Wang, Li; Liu, Qing; Liu, Yu-Xin; He, Li-Li

    2014-07-01

    Decomposition of perfluorooctanoic acid (PFOA) is of prime importance since it is recognized as a persistent organic pollutant and is widespread in the environment. Heterogeneous photocatalytic decomposition of PFOA by TiO2 (P25) was investigated under 254 nm UV light. Experimental conditions including initial pH, TiO2 content and PFOA concentration, were varied to demonstrate their effects on the decomposition of PFOA. It was observed that the photocatalytic degradation kinetics of PFOA could be fitted to the quasi-first-order equation. The pH played a determinant role in the decomposition of PFOA and the presence of O2 increased the degradation rate. Optimal conditions for a complete removal were obtained using 1.5 g x L(-1) TiO2 at pH 3 in air atmosphere, with a rate constant of 0.420 6 h(-1). The contribution experiments of various reactive species produced during the photocatalysis were also investigated with the addition of different scavengers and it was found that photogenerated holes (h+) was the major reactive species which was responsible for 66.1% of the degradation rate, and the *OH was involved in PFOA degradation as well. In addition, the photocatalytic experiment with the addition of NaF indicated that the adsorption of PFOA was of primary importance for the photocatalytic decomposition. Perfluorocarboxylic acids (PFCAs) with shorter carbon chain length as intermediates and products were identified with UPLC-QTOF/MS, and a possible mechanism for PFOA decomposition was proposed. PMID:25244845

  11. The Experience of Age-Related Macular Degeneration

    ERIC Educational Resources Information Center

    Wong, Elaine Y. H.; Guymer, Robyn H.; Hassell, Jennifer B.; Keeffe, Jill E.

    2004-01-01

    This qualitative article describes the impact of age-related macular degeneration (ARMD) among 15 participants: how a person makes sense of ARMD, the effect of ARMD on the person's quality of life, the psychological disturbances associated with the limitations of ARMD, and the influence of ARMD on social interactions. Such in-depth appreciation of…

  12. Awareness, Knowledge, and Concern about Age-Related Macular Degeneration

    ERIC Educational Resources Information Center

    Cimarolli, Verena R.; Laban-Baker, Allie; Hamilton, Wanda S.; Stuen, Cynthia

    2012-01-01

    Age-related macular degeneration (AMD)--a common eye disease causing vision loss--can be detected early through regular eye-health examinations, and measures can be taken to prevent visual decline. Getting eye examinations requires certain levels of awareness, knowledge, and concern related to AMD. However, little is known about AMD-related…

  13. Neuroanatomical Substrates of Age-Related Cognitive Decline

    ERIC Educational Resources Information Center

    Salthouse, Timothy A.

    2011-01-01

    There are many reports of relations between age and cognitive variables and of relations between age and variables representing different aspects of brain structure and a few reports of relations between brain structure variables and cognitive variables. These findings have sometimes led to inferences that the age-related brain changes cause the…

  14. Age-Related Differences in Moral Identity across Adulthood

    ERIC Educational Resources Information Center

    Krettenauer, Tobias; Murua, Lourdes Andrea; Jia, Fanli

    2016-01-01

    In this study, age-related differences in adults' moral identity were investigated. Moral identity was conceptualized a context-dependent self-structure that becomes differentiated and (re)integrated in the course of development and that involves a broad range of value-orientations. Based on a cross-sectional sample of 252 participants aged 14 to…

  15. Neuroimaging explanations of age-related differences in task performance

    PubMed Central

    Steffener, Jason; Barulli, Daniel; Habeck, Christian; Stern, Yaakov

    2014-01-01

    Advancing age affects both cognitive performance and functional brain activity and interpretation of these effects has led to a variety of conceptual research models without always explicitly linking the two effects. However, to best understand the multifaceted effects of advancing age, age differences in functional brain activity need to be explicitly tied to the cognitive task performance. This work hypothesized that age-related differences in task performance are partially explained by age-related differences in functional brain activity and formally tested these causal relationships. Functional MRI data was from groups of young and old adults engaged in an executive task-switching experiment. Analyses were voxel-wise testing of moderated-mediation and simple mediation statistical path models to determine whether age group, brain activity and their interaction explained task performance in regions demonstrating an effect of age group. Results identified brain regions whose age-related differences in functional brain activity significantly explained age-related differences in task performance. In all identified locations, significant moderated-mediation relationships resulted from increasing brain activity predicting worse (slower) task performance in older but not younger adults. Findings suggest that advancing age links task performance to the level of brain activity. The overall message of this work is that in order to understand the role of functional brain activity on cognitive performance, analysis methods should respect theoretical relationships. Namely, that age affects brain activity and brain activity is related to task performance. PMID:24672481

  16. Glycosaminoglycans in the Human Cornea: Age-Related Changes

    PubMed Central

    Pacella, Elena; Pacella, Fernanda; De Paolis, Giulio; Parisella, Francesca Romana; Turchetti, Paolo; Anello, Giulia; Cavallotti, Carlo

    2015-01-01

    AIM To investigate possible age-related changes in glycosaminoglycans (GAGs) in the human cornea. The substances today called GAGs were previously referred to as mucopolysaccharides. METHODS Samples of human cornea were taken from 12 younger (age 21 ± 1.2) and 12 older (age 72 ± 1.6) male subjects. Samples were weighed, homogenized, and used for biochemical and molecular analyses. All the quantitative results were statistically analyzed. RESULTS The human cornea appears to undergo age-related changes, as evidenced by our biochemical and molecular results. The total GAG and hyaluronic acid counts were significantly higher in the younger subjects than in the older subjects. The sulfated heavy GAGs, such as chondroitin, dermatan, keratan, and heparan sulfate, were lower in the younger subjects than in the older subjects. DISCUSSION GAGs of the human cornea undergo numerous age-related changes. Their quantity is significantly altered in the elderly in comparison with younger subjects. GAGs play an important role in age-related diseases of the human cornea. PMID:25674020

  17. PPARα agonist, fenofibrate, ameliorates age-related renal injury.

    PubMed

    Kim, Eun Nim; Lim, Ji Hee; Kim, Min Young; Kim, Hyung Wook; Park, Cheol Whee; Chang, Yoon Sik; Choi, Bum Soon

    2016-08-01

    The kidney ages quickly compared with other organs. Expression of senescence markers reflects changes in the energy metabolism in the kidney. Two important issues in aging are mitochondrial dysfunction and oxidative stress. Peroxisome proliferator-activated receptor α (PPARα) is a member of the ligand-activated nuclear receptor superfamily. PPARα plays a major role as a transcription factor that regulates the expression of genes involved in various processes. In this study, 18-month-old male C57BL/6 mice were divided into two groups, the control group (n=7) and the fenofibrate-treated group (n=7) was fed the normal chow plus fenofibrate for 6months. The PPARα agonist, fenofibrate, improved renal function, proteinuria, histological change (glomerulosclerosis and tubular interstitial fibrosis), inflammation, and apoptosis in aging mice. This protective effect against age-related renal injury occurred through the activation of AMPK and SIRT1 signaling. The activation of AMPK and SIRT1 allowed for the concurrent deacetylation and phosphorylation of their target molecules and decreased the kidney's susceptibility to age-related changes. Activation of the AMPK-FOXO3a and AMPK-PGC-1α signaling pathways ameliorated oxidative stress and mitochondrial dysfunction. Our results suggest that activation of PPARα and AMPK-SIRT1 signaling may have protective effects against age-related renal injury. Pharmacological targeting of PPARα and AMPK-SIRT1 signaling molecules may prevent or attenuate age-related pathological changes in the kidney. PMID:27130813

  18. Age-Related Differences in the Production of Textual Descriptions

    ERIC Educational Resources Information Center

    Marini, Andrea; Boewe, Anke; Caltagirone, Carlo; Carlomagno, Sergio

    2005-01-01

    Narratives produced by 69 healthy Italian adults were analyzed for age-related changes of microlinguistic, macrolinguistic and informative aspects. The participants were divided into five age groups (20-24, 25-39, 40-59, 60-74, 75-84). One single-picture stimulus and two cartoon sequences were used to elicit three stories per subject. Age-related…

  19. APOLIPOPROTEIN E GENE AND EARLY AGE-RELATED MACULOPATHY

    Technology Transfer Automated Retrieval System (TEKTRAN)

    OBJECTIVE: To examine the association between the apolipoprotein E (APOE) gene and early age-related maculopathy (ARM) in middle-aged persons. DESIGN: Population-based cross-sectional study. PARTICIPANTS: Participants from the Atherosclerosis Risk in Communities Study (n = 10139; age range, 49-73 ye...

  20. Nutritional antioxidants and age-related cataract and maculopathy

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Loss of vision is the second greatest, next to death, fear among the elderly. Age-related cataract (ARC) and maculopathy (ARM) are two major causes of blindness worldwide. There are several important reasons to study relationships between risk for ARC/ARM and nutrition: (1) because it is likely that...

  1. Nutritional modulation of age-related macular degeneration

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Age-related macular degeneration (AMD) is the leading cause of blindness in the elderly worldwide. It affects 30-50 million individuals and clinical hallmarks of AMD are observed in at least one third of persons over the age of 75 in industrialized countries (Gehrs et al., 2006). Costs associated wi...

  2. Age-Related Factors in Second Language Acquisition.

    ERIC Educational Resources Information Center

    Twyford, Charles William

    The convergence of several lines of psycholinguistic and sociolinguistic research suggests possible explanations for age-related influences on language acquisition. These factors, which include cognitive development, sociocultural context, affective factors, and language input, can be helpful to language educators. By being alert to the cognitive…

  3. Determination of the degradation mechanism for polychlorinated biphenyl congeners using mechanically alloyed magnesium/palladium in methanol

    NASA Astrophysics Data System (ADS)

    Devor, Robert William

    Polychlorinated biphenyls are a ubiquitous environmental contaminant that can be found today throughout the world in soils and sediments, lakes and rivers, and flora and fauna. PCBs have percolated throughout the food chain, so that almost every human being has a detectable amount of the contaminant within their blood stream. Existing remediation methods include incineration, dredging and landfilling, and microbial degradation, but all of these methods have drawbacks that limit their effectiveness as treatment options. Recently, the use of zero-valent metals as a means of reductive dechlorination has been explored. Using a combination of zerovalent magnesium and catalytic palladium, a successful bimetallic system capable of degrading PCBs has been created and optimized. Determining the mechanism for the reductive dechlorination has proven to be an arduous task, but experimental evidence has suggested three possible radical-type mechanisms for the use Mg/Pd specifically in methanol (as compared to aqueous systems). These possible mechanisms differ in the type of hydrogen species that replaces the chlorine atom on the PCB. Thermodynamic information has also aided in narrowing down which of the suggested pathways is most likely. It appears likely that the hydrogen involved in the dechlorination has the form of a "hydride-like" radical, which is a form of electron-rich atomic hydrogen. According to the literature, Pd catalysts create this species within the first few subsurface layers of the palladium in the presence of molecular hydrogen. Further work will be necessary to confirm that the "hydride-like" radical is actually the species involved in the dechlorination.

  4. Spermidine mediates degradation of ornithine decarboxylase by a non-lysosomal, ubiquitin-independent mechanism

    SciTech Connect

    Glass, J.R.; Gerner, E.W.

    1987-01-01

    The mechanism of spermidine-induced ornithine decarboxylase (OCD, E.C. 4.1.1.17) inactivation was investigated using Chinese hamster ovary (CHO) cells, maintained in serum-free medium, which display a stabilization of ODC owing to the lack of accumulation of putrescine and spermidine. Treatment of cells with 10 ..mu..M exogenous spermidine leads to rapid decay of ODC activity accompanied by a parallel decrease in enzyme protein. Analysis of the decay of (/sup 35/S)methionine-labeled ODC and separation by two-dimensional electrophoresis revealed no detectable modification in ODC structure during enhanced degradation. Spermidine-mediated inactivation of ODC occurred in a temperature-dependent manner exhibiting pseudo-first-order kinetics over a temperature range of 22-37/sup 0/C. In cultures treated continuously, an initial lag was observed after treatment with spermidine, followed by a rapid decline in activity as an apparent critical concentration of intracellular spermidine was achieved. Treating cells at 22/sup 0/C for 3 hours with 10 ..mu.. M spermidine, followed by removal of exogenous polyamine, and then shifting to varying temperatures, resulted in rates of ODC inactivation identical with that determined with a continuous treatment. Arrhenius analysis showed that polyamine mediated inactivation of ODC occurred with an activation energy of approximately 16 kcal/mol. Treatment of cells with lysosomotrophic agents had no effect of ODC degradation. ODC turnover was not dependent on ubiquitin-dependent proteolysis. These data support the hypothesis that spermidine regulates ODC degradation via a mechanism requiring new protein synthesis, and that this occurs via a non-lysosomal, ubiquitin-independent pathway.

  5. Age-Related Changes in 1/f Neural Electrophysiological Noise

    PubMed Central

    Kramer, Mark A.; Case, John; Lepage, Kyle Q.; Tempesta, Zechari R.; Knight, Robert T.; Gazzaley, Adam

    2015-01-01

    Aging is associated with performance decrements across multiple cognitive domains. The neural noise hypothesis, a dominant view of the basis of this decline, posits that aging is accompanied by an increase in spontaneous, noisy baseline neural activity. Here we analyze data from two different groups of human subjects: intracranial electrocorticography from 15 participants over a 38 year age range (15–53 years) and scalp EEG data from healthy younger (20–30 years) and older (60–70 years) adults to test the neural noise hypothesis from a 1/f noise perspective. Many natural phenomena, including electrophysiology, are characterized by 1/f noise. The defining characteristic of 1/f is that the power of the signal frequency content decreases rapidly as a function of the frequency (f) itself. The slope of this decay, the noise exponent (χ), is often <−1 for electrophysiological data and has been shown to approach white noise (defined as χ = 0) with increasing task difficulty. We observed, in both electrophysiological datasets, that aging is associated with a flatter (more noisy) 1/f power spectral density, even at rest, and that visual cortical 1/f noise statistically mediates age-related impairments in visual working memory. These results provide electrophysiological support for the neural noise hypothesis of aging. SIGNIFICANCE STATEMENT Understanding the neurobiological origins of age-related cognitive decline is of critical scientific, medical, and public health importance, especially considering the rapid aging of the world's population. We find, in two separate human studies, that 1/f electrophysiological noise increases with aging. In addition, we observe that this age-related 1/f noise statistically mediates age-related working memory decline. These results significantly add to this understanding and contextualize a long-standing problem in cognition by encapsulating age-related cognitive decline within a neurocomputational model of 1/f noise

  6. Mechanical Properties Degradation of Teflon(Trademark) FEP Returned from the Hubble Space Telescope

    NASA Technical Reports Server (NTRS)

    Dever, Joyce A.; deGroh, Kim K.; Townsend, Jacqueline A.; Wang, L. Len

    1998-01-01

    After 6.8 years on orbit, degradation has been observed in the mechanical properties of second-surface metalized Teflon(Reg) FEP (fluorinated ethylene propylene) used on the Hubble Space Telescope (HST) on the outer surface of the multi-layer insulation (MLI) blankets and on radiator surfaces. Cracking of FEP surfaces on HST was first observed upon close examination of samples with high solar exposure retrieved during the first servicing mission (SM1) conducted 3.6 years after HST was put into orbit. Astronaut observations and photographs from the second servicing mission (SM2), conducted after 6.8 years on orbit, revealed severe cracks in the FEP surfaces of the MLI on many locations around the telescope. This paper describes results of mechanical properties testing of FEP surfaces exposed for 3.6 years and 6.8 years to the space environment on HST. These tests include tensile testing, surface micro-hardness testing, and bend testing.

  7. Reaction mechanisms and rate constants of waste degradation in landfill bioreactor systems with enzymatic-enhancement.

    PubMed

    Jayasinghe, P A; Hettiaratchi, J P A; Mehrotra, A K; Kumar, S

    2014-06-01

    Augmenting leachate before recirculation with peroxidase enzymes is a novel method to increase the available carbon, and therefore the food supply to microorganisms at the declining phase of the anaerobic landfill bioreactor operation. In order to optimize the enzyme-catalyzed leachate recirculation process, it is necessary to identify the reaction mechanisms and determine rate constants. This paper presents a kinetic model developed to ascertain the reaction mechanisms and determine the rate constants for enzyme catalyzed anaerobic waste degradation. The maximum rate of reaction (Vmax) for MnP enzyme-catalyzed reactors was 0.076 g(TOC)/g(DS).day. The catalytic turnover number (k(cat)) of the MnP enzyme-catalyzed was 506.7 per day while the rate constant (k) of the un-catalyzed reaction was 0.012 per day. PMID:24759644

  8. Degradation and corresponding failure mechanism for GaN-based LEDs

    NASA Astrophysics Data System (ADS)

    Fu, Jiajia; Zhao, Lixia; Cao, Haicheng; Sun, Xuejiao; Sun, Baojuan; Wang, Junxi; Li, Jinmin

    2016-05-01

    The degradation behaviors of high power GaN-based vertical blue LEDs on Si substrates were measured using in-situ accelerated life test. The results show that the dominant failure mechanism would be different during the operation. Besides that, the corresponding associated failure mechanisms were investigated systematically by using different analysis technologies, such as Scan Electron Microscopy, Reflectivity spectroscopy, Transient Thermal Analysis, Raman Spectra, etc. It is shown that initially, the failure modes were mainly originated from the semiconductor die and interconnect, while afterwards, the following serious deterioration of the radiant fluxes was attributed to the package. The interface material and quality, such as die attach and frame, play an important role in determining the thermal performance and reliability. In addition, the heating effect during the operation will also release the compressive strain in the chip. These findings will help to improve the reliability of GaN-based LEDs, especially for the LEDs with vertical structure.

  9. Degradation mechanism of Cu(In,Ga)Se2 solar cells induced by exposure to air

    NASA Astrophysics Data System (ADS)

    Nishinaga, Jiro; Kamikawa, Yukiko; Koida, Takashi; Shibata, Hajime; Niki, Shigeru

    2016-07-01

    The degradation mechanism of unencapsulated Cu(In,Ga)Se2 (CIGS) solar cells upon exposure to air has been investigated. Exposure to air at room temperature slightly reduces the conversion efficiency of CIGS solar cells. However, this conversion efficiency decreases significantly under damp heat testing at 85 °C and a relative humidity of 85% for 15 h. The shunt resistance and conversion efficiency are completely recovered after removing the side edges of the CIGS solar cells by mechanical scribing. This result suggests that low-resistive layers are formed on the sidewalls of the solar cells during damp heat testing. In addition, alkaline solution etching has been confirmed to be an effective way of removing the low-resistive layers. The low-resistive layers on the sidewalls are identified to be molybdenum oxides and sodium molybdate by Auger electron spectroscopy. After etching the oxides on the sidewalls, the saturation current density and ideality factor are confirmed to be improved.

  10. Trimethylene carbonate and epsilon-caprolactone based (co)polymer networks: mechanical properties and enzymatic degradation.

    PubMed

    Bat, Erhan; Plantinga, Josée A; Harmsen, Martin C; van Luyn, Marja J A; Zhang, Zheng; Grijpma, Dirk W; Feijen, Jan

    2008-11-01

    High molecular weight trimethylene carbonate (TMC) and epsilon-caprolactone (CL) (co)polymers were synthesized. Melt pressed (co)polymer films were cross-linked by gamma irradiation (25 kGy or 50 kGy) in vacuum, yielding gel fractions of up to 70%. The effects of copolymer composition and irradiation dose on the cytotoxicity, surface properties, degradation behavior, and mechanical and thermal properties of these (co)polymers and networks were investigated. Upon incubation with cell culture medium containing extracts of (co)polymers and networks, human foreskin fibroblasts remained viable. For all (co)polymers and networks, cell viabilities were determined to be higher than 94%. The formed networks were flexible, with elastic moduli ranging from 2.7 to 5.8 MPa. Moreover, these form-stable networks were creep resistant under dynamic conditions. The permanent deformation after 2 h relaxation was as low as 1% after elongating to 50% strain for 20 times. The in vitro enzymatic erosion behavior of these hydrophobic (co)polymers and networks was investigated using aqueous lipase solutions. The erosion rates in lipase solution could be tuned linearly from 0.8 to 45 mg/(cm (2) x day) by varying the TMC to CL ratio and the irradiation dose. The copolymers and networks degraded essentially by a surface erosion mechanism. PMID:18855440

  11. Radiation induced oxidative degradation of polymers—III. Effect of radiation on mechanical properties

    NASA Astrophysics Data System (ADS)

    Seguchi, Tadao; Arakawa, Kazuo; Ito, Masayuki; Hayakawa, Naohiro; Machi, Sueo

    The changes of mechanical properties of various kinds of polyethylene (PE) and ethylene-propylene copolymer (EPR) with the irradiation in air, in oxygen of 10 atm, and under vacuum were investigated. The decrease in the elongation ( E b) and the tensile strength ( T b) of PE by the irradiation in oxygen is larger than under vacuum. The changes of E b well reflect the degradation of PE. In case of EPR, the T b decreases sharply with dose in any environments, and the E b decreases under vacuum to a larger extent than in oxygen. The modulus at 200% elongation of EPR increases with dose under vacuum, but decreases in oxygen. When the samples were irradiated in air, the changes of the mechanical properties were the intermediate between oxygen and vacuum and dependent on the ratio of oxidation and non-oxidation layers in the film. The antioxidant (Irganox 1010 or DPPD) mixed in polymers was found to retard effectively the polymer degradation by the irradiation in oxygen.

  12. New insights into atrazine degradation by cobalt catalyzed peroxymonosulfate oxidation: kinetics, reaction products and transformation mechanisms.

    PubMed

    Ji, Yuefei; Dong, Changxun; Kong, Deyang; Lu, Junhe

    2015-03-21

    The widespread occurrence of atrazine in waters poses potential risk to ecosystem and human health. In this study, we investigated the underlying mechanisms and transformation pathways of atrazine degradation by cobalt catalyzed peroxymonosulfate (Co(II)/PMS). Co(II)/PMS was found to be more efficient for ATZ elimination in aqueous solution than Fe(II)/PMS process. ATZ oxidation by Co(II)/PMS followed pseudo-first-order kinetics, and the reaction rate constant (k(obs)) increased appreciably with increasing Co(II) concentration. Increasing initial PMS concentration favored the decomposition of ATZ, however, no linear relationship between k(obs) and PMS concentration was observed. Higher efficiency of ATZ oxidation was observed around neutral pH, implying the possibility of applying Co(II)/PMS process under environmental realistic conditions. Natural organic matter (NOM), chloride (Cl(-)) and bicarbonate (HCO3(-)) showed detrimental effects on ATZ degradation, particularly at higher concentrations. Eleven products were identified by applying solid phase extraction-liquid chromatography-mass spectrometry (SPE-LC/MS) techniques. Major transformation pathways of ATZ included dealkylation, dechlorination-hydroxylation, and alkyl chain oxidation. Detailed mechanisms responsible for these transformation pathways were discussed. Our results reveal that Co(II)/PMS process might be an efficient technique for remediation of groundwater contaminated by ATZ and structurally related s-triazine herbicides. PMID:25544494

  13. Mechanical degradation of biological heart valve tissue induced by low diameter crimping: an early assessment.

    PubMed

    Khoffi, Foued; Heim, Frederic

    2015-04-01

    Transcatheter aortic valve implantation (TAVI) has become today an increasingly attractive procedure to relieve patients from aortic valve disease. However, the procedure requires crimping biological tissue within a metallic stent for low diameter catheter insertion purpose. This step induces specific stress in the leaflets especially when the crimping diameter is small. One concern about crimping is the potential degradations undergone by the biological tissue, which may limit the durability of the valve once implanted. The purpose of the present work is to study the effect of low diameter crimping on the mechanical performances of pericardium valve prototypes. The prototypes were compressed to a diameter of 1mm within braided stents for 20 min. SEM observations performed on crimped material show that crimped leaflets undergo degradations characterized by apparent surface defects. Moreover mechanical extension tests were performed on pericardium strips before and after crimping. The strips (15 mm long, 5mm wide) were taken from both crimped and native leaflets considering 2 different valve diameters, 19 and 21 mm. In order to prevent the premature drying of the pericardium tissue during the procedure, the biological tissue was kept in contact with a formaldehyde solution. Results show that the ultimate strength value decreases nearly by up to 50%. The modifications observed in the material may jeopardize the long term durability of the device. However, further tests are necessary with a larger amount of samples to confirm these early results. PMID:25621851

  14. An investigation on focused electron/ion beam induced degradation mechanisms of conjugated polymers.

    PubMed

    Sezen, Meltem; Plank, Harald; Fisslthaler, Evelin; Chernev, Boril; Zankel, Armin; Tchernychova, Elena; Blümel, Alexander; List, Emil J W; Grogger, Werner; Pölt, Peter

    2011-12-01

    Irradiation damage, caused by the use of beams in the electron microscopes, leads to undesired physical/chemical material property changes or uncontrollable modification of structures that are being processed. Particularly, soft matter such as polymers or biological materials is highly susceptible and very much prone to react on irradiation by electron and ion beams. The effect is even higher when materials are subjected to energetic species such as ions that possess high momentum and relatively low mean path due to their mass. Especially when Ga(+) ions (used as the ion source in Focused Ion Beam (FIB) instruments) are considered, the end-effect might even be the total loss of the material's properties. This paper will discuss the possible types of degradation mechanisms and defect formations that can take place during ion and electron beam irradiation of the conjugated polymers: e.g. polyfluorene (PF) and poly-3-hexylthiophene (P3HT) thin films. For the investigation of the irradiation induced degradation mechanisms in this study, complementary analytical techniques such as Raman Spectroscopy (RS), Infrared Spectroscopy (IR), Electron Energy Loss Spectroscopy (EELS), Atomic Force Microscopy (AFM), and Fluorescence Microscopy including Photoluminescence (PL) and Electroluminescence (EL) Microscopy were applied. PMID:21993473

  15. Aggrecanolysis and in vitro matrix degradation in the immature bovine meniscus: mechanisms and functional implications

    PubMed Central

    2009-01-01

    Introduction Little is known about endogenous or cytokine-stimulated aggrecan catabolism in the meniscal fibrocartilage of the knee. The objectives of this study were to characterize the structure, distribution, and processing of aggrecan in menisci from immature bovines, and to identify mechanisms of extracellular matrix degradation that lead to changes in the mechanical properties of meniscal fibrocartilage. Methods Aggrecanase activity in the native immature bovine meniscus was examined by immunolocalization of the aggrecan NITEGE neoepitope. To investigate mechanisms of cytokine-induced aggrecan catabolism in this tissue, explants were treated with interleukin-1α (IL-1) in the absence or presence of selective or broad spectrum metalloproteinase inhibitors. The sulfated glycosaminoglycan (sGAG) and collagen contents of explants and culture media were quantified by biochemical methods, and aggrecan catabolism was examined by Western analysis of aggrecan fragments. The mechanical properties of explants were determined by dynamic compression and shear tests. Results The aggrecanase-generated NITEGE neoepitope was preferentially localized in the middle and outer regions of freshly isolated immature bovine menisci, where sGAG density was lowest and blood vessels were present. In vitro treatment of explants with IL-1 triggered the accumulation of NITEGE in the inner and middle regions. Middle region explants stimulated with IL-1 exhibited substantial decreases in sGAG content, collagen content, and mechanical properties. A broad spectrum metalloproteinase inhibitor significantly reduced sGAG loss, abrogated collagen degradation, and preserved tissue mechanical properties. In contrast, an inhibitor selective for ADAMTS-4 and ADAMTS-5 was least effective at blocking IL-1-induced matrix catabolism and loss of mechanical properties. Conclusions Aggrecanase-mediated aggrecanolysis, typical of degenerative articular cartilage, may play a physiologic role in the development

  16. Mixed-mode sorption of hydroxylated atrazine degradation products to sell: A mechanism for bound residue

    USGS Publications Warehouse

    Lerch, R.N.; Thurman, E.M.; Kruger, E.L.

    1997-01-01

    This study tested the hypothesis that sorption of hydroxylated atrazine degradation products (HADPs: hydroxyatrazine, HA; deethylhydroxyatrazine, DEHA; and deisopropylhydroxyatrazine, DIHA) to soils occurs by mixed-mode binding resulting from two simultaneous mechanisms: (1) cation exchange and (2) hydrophobic interaction. The objective was to use liquid chromatography and soil extraction experiments to show that mixed-mode binding is the mechanism controlling HADP sorption to soils and is also a mechanism for bound residue. Overall, HADP binding to solid-phase extraction (SPE) sorbents occurred in the order: cation exchange >> octadecyl (C18) >> cyanopropyl. Binding to cation exchange SPE and to a high-performance liquid chromatograph octyl (C8) column showed evidence for mixed-mode binding. Comparison of soil extracted by 0.5 M KH2P04, pH 7.5, or 25% aqueous CH3CN showed that, for HA and DIHA, cation exchange was a more important binding mechanism to soils than hydrophobic interaction. Based on differences between several extractants, the extent of HADP mixed-mode binding to soil occurred in the following order: HA > DIHA > DEHA. Mixed-mode extraction recovered 42.8% of bound atrazine residues from aged soil, and 88% of this fraction was identified as HADPs. Thus, a significant portion of bound atrazine residues in soils is sorbed by the mixed-mode binding mechanisms.

  17. Physical mechanisms affecting hot carrier-induced degradation in gallium nitride HEMTs

    NASA Astrophysics Data System (ADS)

    Mukherjee, Shubhajit

    Gallium Nitride or GaN-based high electron mobility transistors (HEMTs) is currently the most promising device technology in several key military and civilian applications due to excellent high-power as well as high-frequency performance. Even though the performance figures are outstanding, GaN-based HEMTs are not as mature as some competing technologies, which means that establishing the reliability of the technology is important to enable use in critical applications. The objective of this research is to understand the physical mechanisms affecting the reliability of GaN HEMTs at moderate drain biases (typically VDS < 30 V in the devices considered here). The degradation in device performance is believed to be due to the formation or modification of charged defects near the interface by hydrogen depassivation processes (due to electron-activated hydrogen removal) from energetic carriers. A rate-equation describing the defect generation process is formulated based on this assumption. A combination of ensemble Monte-Carlo (EMC) simulation statistics, ab-initio density functional theory (DFT) calculations, and accelerated stress experiments is used to relate the candidate defects to the overall degradation behavior (VT and gm). The focus of this work is on the 'semi-ON' mode of transistor operation in which the degradation is usually observed to be at its highest. This semi-ON state is reasonably close to the biasing region of class-AB high power amplifiers, which are popular because of the combination of high efficiency and low distortion that is associated with this configuration. The carrier-energy distributions are obtained using an EMC simulator that was developed specifically for III-V HFETs. The rate equation is used to model the degradation at different operating conditions as well as longer stress times from the result of one short duration stress test, by utilizing the carrier-energy distribution obtained from EMC simulations for one baseline condition

  18. Polysorbate 20 Degradation in Biopharmaceutical Formulations: Quantification of Free Fatty Acids, Characterization of Particulates, and Insights into the Degradation Mechanism.

    PubMed

    Tomlinson, Anthony; Demeule, Barthélemy; Lin, Baiwei; Yadav, Sandeep

    2015-11-01

    Polysorbate 20 (PS20), a commonly used surfactant in biopharmaceuticals, showed degradation upon long-term (∼18-36 months) storage of two monoclonal antibody (mAb, mAb-A, and mAb-B) drug products at 2-8 °C. The PS20 degradation resulted in the accumulation of free fatty acids (FFA), which ultimately precipitated to form particles upon long-term storage. This study documents the development, qualification, and application of a method for FFA quantification in soluble and insoluble fraction of protein formulation. The method was applied to the quantification of capric acid, lauric acid, myristic acid, palmitic/oleic acid, and stearic acid in placebo as well as active protein formulations on stability. Quantification of FFA in both the soluble and insoluble fraction of mAb-A and mAb-B provided a better mechanistic understanding of PS20 degradation and the dynamics of subsequent fatty acid particle formation. Additionally, the use of this method for monitoring and quantitation of the FFA on real time storage stability appears to aid in identifying batches with higher probability for particulate formation upon extended storage at 5 °C. PMID:26419339

  19. Oxidative stress, innate immunity, and age-related macular degeneration

    PubMed Central

    Shaw, Peter X.; Stiles, Travis; Douglas, Christopher; Ho, Daisy; Fan, Wei; Du, Hongjun; Xiao, Xu

    2016-01-01

    Age-related macular degeneration (AMD) is a leading cause of vision loss affecting tens of millions of elderly worldwide. Early AMD is characterized by the appearance of soft drusen, as well as pigmentary changes in the retinal pigment epithelium (RPE). These soft, confluent drusen can progress into two forms of advanced AMD: geographic atrophy (GA, or dry AMD) or choroidal neovascularization (CNV, or wet AMD). Both forms of AMD result in a similar clinical progression in terms of loss of central vision. The exact mechanism for developing early AMD, as well as triggers responsible for progressing to advanced stage of disease, is still largely unknown. However, significant evidence exists demonstrating a complex interplay of genetic and environmental factors as causes of AMD progression. Multiple genes and/or single nucleotide polymorphisms (SNPs) have been found associated with AMD, including various genes involved in the complement pathway, lipid metabolism and extracellular matrix (ECM) remodeling. Of the known genetic contributors to disease risk, the CFH Y402H and HTRA1/ARMS polymorphisms contribute to more than 50% of the genetic risk for AMD. Environmentally, oxidative stress plays a critical role in many aging diseases including cardiovascular disease, cancer, Alzheimer’s disease and AMD. Due to the exposure to sunlight and high oxygen concentration, the oxidative stress burden is higher in the eye than other tissues, which can be further complicated by additional oxidative stressors such as smoking. Increasingly, evidence is accumulating suggesting that functional abnormalities of the innate immune system incurred via high risk genotypes may be contributing to the pathogenesis of AMD by altering the inflammatory homeostasis in the eye, specifically in the handling of oxidation products. As the eye in non-pathological instances maintains a low level of inflammation despite the presence of a relative abundance of potentially inflammatory molecules, we have

  20. Serum Antioxidative Enzymes Levels and Oxidative Stress Products in Age-Related Cataract Patients

    PubMed Central

    Chang, Dong; Zhang, Xuefei; Rong, Shengzhong; Sha, Qian; Liu, Peipei; Han, Tao; Pan, Hongzhi

    2013-01-01

    Purpose. To investigate the activity of antioxidative enzymes and the products of oxidative stress in patients with age-related cataracts and compare the findings with those in healthy control subjects. Method. Sixty patients with age-related cataract and sixty healthy controls of matched age and gender were included in this study. Serum samples were obtained to detect the antioxidative enzymes of superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-Px), and oxidation degradation products of malondialdehyde (MDA), 4-hydroxynonenal (4-HNE), conjugated diene (CD), advanced oxidation protein products (AOPP), protein carbonyl (PC), and 8-hydroxydeoxyguanosine (8-OHdG). Results. Serum SOD, GSH-Px, and CAT activities in cataract group were significantly decreased as compared to the control subjects (P < 0.05). The levels of MDA, 4-HNE, and CD in cataract patients were significantly higher than those in the control subjects (P < 0.05, P < 0.01). Cataract patients had higher levels of 8-OHdG, AOPP, and PC with respect to the comparative group of normal subjects (P < 0.01). And there was no statistical significance in concentration of antioxidative enzymes and oxidative stress products in patients with different subtype cataract. Conclusions. Oxidative stress is an important risk factor in the development of age-related cataract, and augmentation of the antioxidant defence systems may be of benefit to prevent or delay cataractogenesis. PMID:23781296

  1. Dietary compound score and risk of age-related macular degeneration in the Age-Related Eye Disease Study

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Purpose: Because foods provide many nutrients, which may interact with each other to modify risk for multifactorial diseases such as age-related macular degeneration (AMD), we sought to develop a composite scoring system to summarize the combined effect of multiple dietary nutrients on AMD risk. Th...

  2. Age-Related Changes to the Neural Correlates of Social Evaluation

    PubMed Central

    Cassidy, Brittany S.; Shih, Joanne Y.; Gutchess, Angela H.

    2012-01-01

    Recent work suggests the existence of a specialized neural system underlying social processing that may be relatively spared with age, unlike pervasive aging-related decline occurring in many cognitive domains. We investigated how neural mechanisms underlying social evaluation are engaged with age, and how age-related changes to socioemotional goals affect recruitment of regions within this network. In a functional MRI study, fifteen young and fifteen older adults formed behavior-based impressions of individuals. They also responded to a prompt that was interpersonally meaningful, social but interpersonally irrelevant, or non-social. Both age groups engaged regions implicated in mentalizing and impression formation when making social relative to non-social evaluations, including dorsal and ventral medial prefrontal cortices, precuneus, and temporoparietal junction. Older adults had increased activation over young in right temporal pole when making social relative to non-social evaluations, suggesting reliance on past experiences when evaluating others. Young had greater activation than old in posterior cingulate gyrus when making interpersonally irrelevant, compared to interpersonally meaningful, evaluations, potentially reflecting enhanced valuation of this information. The findings demonstrate the age-related preservation of the neural correlates underlying social evaluation, and suggest that functioning in these regions might be mediated by age-related changes in socioemotional goals. PMID:22439896

  3. Physiological Antioxidative Network of the Bilirubin System in Aging and Age-Related Diseases

    PubMed Central

    Kim, Sung Young; Park, Sang Chul

    2012-01-01

    Oxidative stress is detrimental to life process and is particularly responsible for aging and age-related diseases. Thus, most organisms are well equipped with a spectrum of biological defense mechanisms against oxidative stress. The major efficient antioxidative mechanism is the glutathione system, operating a redox cycling mechanism for glutathione utilization, which consists of glutathione and its peroxidase and reductase. However, this system is mainly effective for hydrophilic oxidants, while lipophilic oxidants require another scavenging system. Since many age-related pathological conditions are related to lipid peroxidation, especially in association with the aging process, the physiological role of the scavenging system for lipophilic oxidants should be considered. In this regard, the biliverdin to bilirubin conversion pathway, via biliverdin reductase (BVR), is suggested to be another major protective mechanism that scavenges lipophilic oxidants because of the lipophilic nature of bilirubin. The efficiency of this bilirubin system might be potentiated by operation of the intertwined bicyclic systems of the suggested redox metabolic cycle of biliverdin and bilirubin and the interactive control cycle of BVR and heme oxygenase. In order to combat oxidative stress, both antioxidative systems against hydrophilic and lipophilic oxidants are required to work cooperatively. In this regard, the roles of the bilirubin system in aging and age-related diseases are reassessed in this review, and their interacting networks are evaluated. PMID:22457648

  4. Arthritis Induces Early Bone High Turnover, Structural Degradation and Mechanical Weakness

    PubMed Central

    Vidal, Bruno; Cascão, Rita; Vale, Ana Catarina; Cavaleiro, Inês; Vaz, Maria Fátima; Brito, José Américo Almeida; Canhão, Helena; Fonseca, João Eurico

    2015-01-01

    Background We have previously found in the chronic SKG mouse model of arthritis that long standing (5 and 8 months) inflammation directly leads to high collagen bone turnover, disorganization of the collagen network, disturbed bone microstructure and degradation of bone biomechanical properties. The main goal of the present work was to study the effects of the first days of the inflammatory process on the microarchitecture and mechanical properties of bone. Methods Twenty eight Wistar adjuvant-induced arthritis (AIA) rats were monitored during 22 days after disease induction for the inflammatory score, ankle perimeter and body weight. Healthy non-arthritic rats were used as controls for compar-ison. After 22 days of disease progression rats were sacrificed and bone samples were collected for histomorphometrical, energy dispersive X-ray spectroscopical analysis and 3-point bending. Blood samples were also collected for bone turnover markers. Results AIA rats had an increased bone turnover (as inferred from increased P1NP and CTX1, p = 0.0010 and p = 0.0002, respectively) and this was paralleled by a decreased mineral content (calcium p = 0.0046 and phos-phorus p = 0.0046). Histomorphometry showed a lower trabecular thickness (p = 0.0002) and bone volume (p = 0.0003) and higher trabecular sepa-ration (p = 0.0009) in the arthritic group as compared with controls. In addition, bone mechanical tests showed evidence of fragility as depicted by diminished values of yield stress and ultimate fracture point (p = 0.0061 and p = 0.0279, re-spectively) in the arthritic group. Conclusions We have shown in an AIA rat model that arthritis induc-es early bone high turnover, structural degradation, mineral loss and mechanical weak-ness. PMID:25617902

  5. Depth profiling of mechanical degradation of PV backsheets after UV exposure

    NASA Astrophysics Data System (ADS)

    Gu, Xiaohong; Krommenhoek, Peter J.; Lin, Chiao-Chi; Yu, Li-Chieh; Nguyen, Tinh; Watson, Stephanie S.

    2015-09-01

    Polymeric multilayer backsheets protect the photovoltaic modules from damage of moisture and ultraviolet (UV) while providing electrical insulation. Due to the multilayer structures, the properties of the inner layers of the backsheets, including their interfaces, during weathering are not well known. In this study, a commercial type of PPE (polyethylene terephthalate (PET)/PET/ethylene vinyl acetate (EVA)) backsheet films was selected as a model system for a depth profiling study of mechanical properties of a backsheet film during UV exposure. The NIST SPHERE (Simulated Photodegradation via High Energy Radiant Exposure) was used for the accelerated laboratory exposure of the materials with UV at 85°C and two relative humidities (RH) of 5 % (dry) and 60 % (humid). Cryomicrotomy was used to obtain cross-sectional PPE samples. Mechanical depth profiling of the cross-sections of aged and unaged samples was conducted by nanoindentation, and a peak-force based quantitative nanomechanical atomic force microscopy (QNM-AFM) mapping techniquewas used to investigate the microstructure and adhesion properties of the adhesive tie layers. The nanoindentation results show the stiffening of the elastic modulus in the PET outer and pigmented EVA layers. From QNM-AFM, the microstructures and adhesion properties of the adhesive layers between PET outer and core layers and between PET core and EVA inner layers are revealed and found to degrade significantly after aging under humidity environment. The results from mechanical depth profiling of the PPE backsheet are further related to the previous chemical depth profiling of the same material, providing new insights into the effects of accelerated UV and humidity on the degradation of multilayer backsheet.

  6. Microscopic degradation mechanism of polyimide film caused by surface discharge under bipolar continuous square impulse voltage

    NASA Astrophysics Data System (ADS)

    Luo, Yang; Wu, Guang-Ning; Liu, Ji-Wu; Peng, Jia; Gao, Guo-Qiang; Zhu, Guang-Ya; Wang, Peng; Cao, Kai-Jiang

    2014-02-01

    Polyimide (PI) film is an important type of insulating material used in inverter-fed motors. Partial discharge (PD) under a sequence of high-frequency square impulses is one of the key factors that lead to premature failures in insulation systems of inverter-fed motors. In order to explore the damage mechanism of PI film caused by discharge, an aging system of surface discharge under bipolar continuous square impulse voltage (BCSIV) is designed based on the ASTM 2275 01 standard and the electrical aging tests of PI film samples are performed above the partial discharge inception voltage (PDIV). The chemical bonds of PI polymer chains are analyzed through Fourier transform infrared spectroscopy (FTIR) and the dielectric properties of unaged and aged PI samples are investigated by LCR testers HIOKI 3532-50. Finally, the micro-morphology and micro-structure changes of PI film samples are observed through scanning electron microscopy (SEM). The results show that the physical and chemical effects of discharge cut off the chemical bonds of PI polymer chains. The fractures of ether bond (C—O—C) and imide ring (C—N—C) on the backbone of a PI polymer chain leads to the decrease of molecular weight, which results in the degradation of PI polymers and the generation of new chemical groups and materials, like carboxylic acid, ketone, aldehydes, etc. The variation of microscopic structure of PI polymers can change the orientation ability of polarizable units when the samples are under an AC electric field, which would cause the dielectric constant ɛ to increase and dielectric loss tan δ to decrease. The SEM images show that the degradation path of PI film is initiated from the surface and then gradually extends to the interior with continuous aging. The injection charge could result in the PI macromolecular chain degradation and increase the trap density in the PI polymer bulk.

  7. Age-related percutaneous penetration part 1: skin factors.

    PubMed

    Konda, S; Meier-Davis, S R; Cayme, B; Shudo, J; Maibach, H I

    2012-05-01

    Changes in the skin that occur in the elderly may put them at increased risk for altered percutaneous penetration from pharmacotherapy along with potential adverse effects. Skin factors that may have a role in age-related percutaneous penetration include blood flow, pH, skin thickness, hair and pore density, and the content and structure of proteins, glycosaminoglycans (GAGs), water, and lipids. Each factor is examined as a function of increasing age along with its potential impact on percutaneous penetration. Additionally, topical drugs that successfully overcome the barrier function of the skin can still fall victim to cutaneous metabolism, thereby producing metabolites that may have increased or decreased activity. This overview discusses the current data and highlights the importance of further studies to evaluate the impact of skin factors in age-related percutaneous penetration. PMID:22622279

  8. Veterans have less age-related cognitive decline.

    PubMed

    McLay, R N; Lyketsos, C G

    2000-08-01

    Military service involves exposure to a number of stresses, both psychological and physical. On the other hand, military personnel generally maintain excellent fitness, and veterans have increased access to education and health care. The overall effect on age-related cognitive decline, whether for good or ill, of having served in the armed forces has not been investigated previously. In this study, we examined a diverse population of 208 veterans and 1,216 civilians followed as part of the Epidemiologic Catchment Area Study in 1981, 1982, and 1993 to 1996. We examined change in Mini-Mental State Examination (MMSE) score after a median of 11.5 years. Veterans were found to have significantly less decrease in MMSE scores at follow-up even after sex, race, and education were taken into account. These results suggest an overall positive effect of military service on the rate of age-related cognitive decline. PMID:10957857

  9. Genetic and Environmental Underpinnings to Age-Related Ocular Diseases

    PubMed Central

    Seddon, Johanna M.

    2013-01-01

    Age-related macular degeneration (AMD), cataract, glaucoma and diabetic retinopathy are common causes of visual loss. Both environmental and genetic factors contribute to the development of these diseases. The modifiable factors related to some of these age-related and visually threatening diseases are smoking, obesity, and dietary factors, and a cardiovascular risk profile. Many common and a few rare genetic factors are associated with AMD. The role of genetic variants for the other diseases are less clear. Interactions between environmental, therapeutic, and genetic factors are being explored. Knowledge of genetic risk and environmental factors, especially for AMD, has grown markedly over the past 2.5 decades and has led to some sight-saving approaches in preventive management. PMID:24335064

  10. Idiom understanding in adulthood: examining age-related differences.

    PubMed

    Hung, Pei-Fang; Nippold, Marilyn A

    2014-03-01

    Idioms are figurative expressions such as hold your horses, kick the bucket, and lend me a hand, which commonly occur in everyday spoken and written language. Hence, the understanding of these expressions is essential for daily communication. In this study, we examined idiom understanding in healthy adults in their 20s, 40s, 60s and 80s (n=30 per group) to determine if performance would show an age-related decline. Participants judged their own familiarity with a set of 20 idioms, explained the meaning of each, described a situation in which the idiom could be used, and selected the appropriate interpretation from a set of choices. There was no evidence of an age-related decline on any tasks. Rather, the 60s group reported greater familiarity and offered better explanations than did the 20s group. Moreover, greater familiarity with idioms was associated with better understanding in adults. PMID:24405225

  11. Age-Related Hyperkyphosis: Its Causes, Consequences, and Management

    PubMed Central

    Katzman, Wendy B.; Wanek, Linda; Shepherd, John A.; Sellmeyer, Deborah E.

    2010-01-01

    Age-related postural hyperkyphosis is an exaggerated anterior curvature of the thoracic spine, sometimes referred to as Dowager’s hump or gibbous deformity. This condition impairs mobility,2,31 and increases the risk of falls33 and fractures.26 The natural history of hyperkyphosis is not firmly established. Hyperkyphosis may develop from either muscle weakness and degenerative disc disease, leading to vertebral fractures and worsening hyperkyphosis, or from initial vertebral fractures that precipitate its development. PMID:20511692

  12. Dietary Approaches that Delay Age-Related Diseases

    PubMed Central

    Everitt, Arthur V; Hilmer, Sarah N; Brand-Miller, Jennie C; Jamieson, Hamish A; Truswell, A Stewart; Sharma, Anita P; Mason, Rebecca S; Morris, Brian J; Le Couteur, David G

    2006-01-01

    Reducing food intake in lower animals such as the rat decreases body weight, retards many aging processes, delays the onset of most diseases of old age, and prolongs life. A number of clinical trials of food restriction in healthy adult human subjects running over 2–15 years show significant reductions in body weight, blood cholesterol, blood glucose, and blood pressure, which are risk factors for the development of cardiovascular disease and diabetes. Lifestyle interventions that lower energy balance by reducing body weight such as physical exercise can also delay the development of diabetes and cardiovascular disease. In general, clinical trials are suggesting that diets high in calories or fat along with overweight are associated with increased risk for cardiovascular disease, type 2 diabetes, some cancers, and dementia. There is a growing literature indicating that specific dietary constituents are able to influence the development of age-related diseases, including certain fats (trans fatty acids, saturated, and polyunsaturated fats) and cholesterol for cardiovascular disease, glycemic index and fiber for diabetes, fruits and vegetables for cardiovascular disease, and calcium and vitamin D for osteoporosis and bone fracture. In addition, there are dietary compounds from different functional foods, herbs, and neutraceuticals such as ginseng, nuts, grains, and polyphenols that may affect the development of age-related diseases. Long-term prospective clinical trials will be needed to confirm these diet—disease relationships. On the basis of current research, the best diet to delay age-related disease onset is one low in calories and saturated fat and high in wholegrain cereals, legumes, fruits and vegetables, and which maintains a lean body weight. Such a diet should become a key component of healthy aging, delaying age-related diseases and perhaps intervening in the aging process itself. Furthermore, there are studies suggesting that nutrition in childhood

  13. Dietary approaches that delay age-related diseases.

    PubMed

    Everitt, Arthur V; Hilmer, Sarah N; Brand-Miller, Jennie C; Jamieson, Hamish A; Truswell, A Stewart; Sharma, Anita P; Mason, Rebecca S; Morris, Brian J; Le Couteur, David G

    2006-01-01

    Reducing food intake in lower animals such as the rat decreases body weight, retards many aging processes, delays the onset of most diseases of old age, and prolongs life. A number of clinical trials of food restriction in healthy adult human subjects running over 2-15 years show significant reductions in body weight, blood cholesterol, blood glucose, and blood pressure, which are risk factors for the development of cardiovascular disease and diabetes. Lifestyle interventions that lower energy balance by reducing body weight such as physical exercise can also delay the development of diabetes and cardiovascular disease. In general, clinical trials are suggesting that diets high in calories or fat along with overweight are associated with increased risk for cardiovascular disease, type 2 diabetes, some cancers, and dementia. There is a growing literature indicating that specific dietary constituents are able to influence the development of age-related diseases, including certain fats (trans fatty acids, saturated, and polyunsaturated fats) and cholesterol for cardiovascular disease, glycemic index and fiber for diabetes, fruits and vegetables for cardiovascular disease, and calcium and vitamin D for osteoporosis and bone fracture. In addition, there are dietary compounds from different functional foods, herbs, and neutraceuticals such as ginseng, nuts, grains, and polyphenols that may affect the development of age-related diseases. Long-term prospective clinical trials will be needed to confirm these diet-disease relationships. On the basis of current research, the best diet to delay age-related disease onset is one low in calories and saturated fat and high in wholegrain cereals, legumes, fruits and vegetables, and which maintains a lean body weight. Such a diet should become a key component of healthy aging, delaying age-related diseases and perhaps intervening in the aging process itself. Furthermore, there are studies suggesting that nutrition in childhood and

  14. Degradation Mechanisms of an Advanced Jet Engine Service-Retired TBC Component

    NASA Astrophysics Data System (ADS)

    Wu, Rudder T.; Osawa, Makoto; Yokokawa, Tadaharu; Kawagishi, Kyoko; Harada, Hiroshi

    Current use of TBCs is subjected to premature spallation failure mainly due to the formation of thermally grown oxides (TGOs). Although extensive research has been carried out to gain better understanding of the thermo - mechanical and -chemical characteristics of TBCs, laboratory-scale studies and simulation tests are often carried out in conditions significantly differed from the complex and extreme environment typically of a modern gas-turbine engine, thus, failed to truly model service conditions. In particular, the difference in oxygen partial pressure and the effects of contaminants present in the engine compartment have often been neglected. In this respect, an investigation is carried out to study the in-service degradation of an EB-PVD TBC coated nozzle-guide vane. Several modes of degradation were observed due to three factors: 1) presence of residual stresses induced by the thermal-expansion mismatches, 2) evolution of bond coat microstructure and subsequent formation of oxide spinels, 3) deposition of CMAS on the surface of TBC.

  15. Lattice distortion mechanism study of TiO{sub 2} nanoparticles during photocatalysis degradation and reactivation

    SciTech Connect

    Wu, Wenhui; Xue, Xudong; Jiang, Xudong; Zhang, Yupeng; Wu, Yichu; Pan, Chunxu

    2015-05-15

    In this paper, the photocatalytic process of TiO{sub 2} (P25) is directly characterized by using a positron annihilation lifetime spectroscopy (PALS), high-resolution transmission electron microscopy (HRTEM), Photoluminescence spectroscopy (PL) and UV Raman spectroscopy (Raman). The experimental results reveal that: 1) From PALS measurements, because τ{sub 1} and τ{sub 2} values and their intensity (I{sub 1} and I{sub 2}) assigned to the different size and amounts of defects, respectively, their variations indicate the formation of different types and amounts of defects during the absorption and degradation. 2) HRTEM observations show that the lattice images become partly blurring when the methylene blue is fully degradated, and clear again after exposed in the air for 30 days. According to the results, we propose a mechanism that the lattice distortion induces the defects as electron capture sites and provides energy for improving photocatalytic process. Meanwhile, the lattice distortion relaxation after exposing in the air for 30 days perfectly explains the gradual deactivation of TiO{sub 2}, because the smaller vacancy defects grow and agglomerate through the several photocatalytic processes. The instrumental PL and Raman are also used to analyze the samples and approved the results of PALS and HRTEM.

  16. Ozonation of parabens in aqueous solution: kinetics and mechanism of degradation.

    PubMed

    Tay, Kheng Soo; Rahman, Noorsaadah Abd; Abas, Mhd Radzi Bin

    2010-12-01

    This study investigated the reaction kinetics and degradation mechanism of parabens (methylparaben, ethylparaben, propylparaben and butylparaben) during ozonation. Experiments were performed at pH 2, 6 and 12 to determine the rate constants for the reaction of protonated, undissociated and dissociated paraben with ozone. The rate constants for the reaction of ozone with dissociated parabens (3.3 × 10(9)-4.2 × 10(9)M(-1)s(-1)) were found to be 10(4) times higher than the undissociated parabens (2.5 × 10(5)-4.4 × 10(5)M(-1)s(-1)) and 10(7) times higher than with the protonated parabens (1.02 × 10(2)-1.38 × 10(2)M(-1)s(-1)). The second-order rate constants for the reaction between parabens with hydroxyl radicals were found to vary from 6.8 × 10(9) to 9.2 × 10(9)M(-1)s(-1). Characterization of degradation by-products (DBPs) formed during the ozonation of each selected parabens has been carried out using GCMS after silylation. Twenty DBPs formed during ozonation of selected parabens have been identified. Hydroxylation has been found to be the major reaction for the formation of the identified DBPs. Through the hydroxylation reaction, a variety of hydroxylated parabens was formed. PMID:20875662

  17. Mechanism of the enhanced degradation of pentachlorophenol by ultrasound in the presence of elemental iron.

    PubMed

    Dai, Youzhi; Li, Fenfang; Ge, Fei; Zhu, Fei; Wu, Lanyan; Yang, Xiangzheng

    2006-10-11

    Ultrasound combined with elemental iron (US/Fe(0)) is effective in oxidizing organic contaminants in water. The sonolysis degradation of pentachlorophenol (PCP) was significantly enhanced by a factor of 4.2 with the addition of elemental iron, mainly via reaction with hydroxyl radicals (OH radicals), and the synergistic mechanism of the enhancement in the combined system was investigated. Experiments were performed with (1) sole ultrasonic treatment; (2) ultrasound in presence of iron; (3) ultrasound combined with copper powder as the same particle size as iron powder; (4) ultrasound in presence of Fe(II). It was observed that PCP degradation and OH radicals production were both enhanced in these combined methods, and the pitting on the sonicated iron surface was apparent. These results indicated that the rate enhancements in US/Fe(0) system were attributed to (1) the iron solid effect and the catalysis of Fe(II) produced from corroded-iron with promoting the production of OH radicals; (2) the increased surface area of iron particles by acoustic cavitation with promoting the adsorption process. PMID:16762499

  18. Sequential RNA degradation pathways provide a fail-safe mechanism to limit the accumulation of unspliced transcripts in Saccharomyces cerevisiae

    PubMed Central

    Sayani, Shakir; Chanfreau, Guillaume F.

    2012-01-01

    The nuclear exosome and the nonsense-mediated mRNA decay (NMD) pathways have been implicated in the degradation of distinct unspliced transcripts in Saccharomyces cerevisiae. In this study we show that these two systems can act sequentially on specific unspliced pre-mRNAs to limit their accumulation. Using steady-state and decay analyses, we show that while specific unspliced transcripts rely mostly on NMD or on the nuclear exosome for their degradation, some unspliced RNAs are stabilized only when both the nuclear exosome and NMD are inactivated. We found that the mechanism of degradation of these unspliced pre-mRNAs is not influenced by promoter identity. However, the specificity in the pre-mRNAs degradation pathways can be manipulated by changing the rate of export or retention of these mRNAs. For instance, reducing the nuclear export of pre-mRNAs mostly degraded by NMD results in a higher fraction of unspliced transcripts degraded by the nuclear exosome. Reciprocally, inactivating the Mlp retention factors results in a higher fraction of unspliced transcripts degraded by NMD for precursors normally targeted by the nuclear exosome. Overall, these results demonstrate that a functional redundancy exists between nuclear and cytoplasmic degradation pathways for unspliced pre-mRNAs, and suggest that the degradation routes of these species are mainly determined by the efficiency of their nuclear export rates. The presence of these two sequential degradation pathways for unspliced pre-mRNAs underscores the importance of limiting their accumulation and might serve as a fail-safe mechanism to prevent the expression of these nonfunctional RNAs. PMID:22753783

  19. Age-related changes in the adaptability of neuromuscular output.

    PubMed

    Morrison, Steven; Sosnoff, Jacob J

    2009-05-01

    The aging process is associated with a general decline in biological function. One characteristic that researchers believe represents this diminished functioning of the aging neuromuscular system is increased physiological tremor. The present study is constructed to assess what age-related differences exist in the dynamics of tremor and forearm muscle activity under postural conditions in which the number of arm segments involved in the task was altered. The authors predicted that any alteration in the tremor or electromyographic (EMG) output of these two groups would provide a clearer understanding of the differential effects of aging or task dynamics on physiological function. Results reveal no age-related differences in finger tremor or forearm extensor muscle EMG activity under conditions in which participants were only required to extend their index finger against gravity. However, when participants had to hold their entire upper limb steady against gravity, the authors observed significant increases in forearm EMG activity, finger-tremor amplitude, power in the 8-12-Hz range, and signal regularity between the 2 age groups. The selective changes in signal regularity, EMG activity, and 8-12-Hz tremor amplitude under more challenging postural demands support the view that the age-related changes in neuromuscular dynamics are not fully elucidated when single task demands are utilized. PMID:19366659

  20. Soybean β-Conglycinin Prevents Age-Related Hearing Impairment

    PubMed Central

    Tanigawa, Tohru; Shibata, Rei; Kondo, Kazuhisa; Katahira, Nobuyuki; Kambara, Takahiro; Inoue, Yoko; Nonoyama, Hiroshi; Horibe, Yuichiro; Ueda, Hiromi; Murohara, Toyoaki

    2015-01-01

    Obesity-related complications are associated with the development of age-related hearing impairment. β-Conglycinin (β-CG), one of the main storage proteins in soy, offers multiple health benefits, including anti-obesity and anti-atherosclerotic effects. Here, to elucidate the potential therapeutic application of β-CG, we investigated the effect of β-CG on age-related hearing impairment. Male wild-type mice (age 6 months) were randomly divided into β-CG-fed and control groups. Six months later, the body weight was significantly lower in β-CG-fed mice than in the controls. Consumption of β-CG rescued the hearing impairment observed in control mice. Cochlear blood flow also increased in β-CG-fed mice, as did the expression of eNOS in the stria vascularis (SV), which protects vasculature. β-CG consumption also ameliorated oxidative status as assessed by 4-HNE staining. In the SV, lipofuscin granules of marginal cells and vacuolar degeneration of microvascular pericytes were decreased in β-CG-fed mice, as shown by transmission electron microscopy. β-CG consumption prevented loss of spiral ganglion cells and reduced the frequencies of lipofuscin granules, nuclear invaginations, and myelin vacuolation. Our observations indicate that β-CG ameliorates age-related hearing impairment by preserving cochlear blood flow and suppressing oxidative stress. PMID:26348726

  1. Hypermnesia: age-related differences between young and older adults.

    PubMed

    Widner, R L; Otani, H; Smith, A D

    2000-06-01

    Hypermnesia is a net improvement in memory performance that occurs across tests in a multitest paradigm with only one study session. Our goal was to identify possible age-related differences in hypermnesic recall. We observed hypermnesia for young adults using verbal (Experiment 1) as well as pictorial (Experiment 2) material, but no hypermnesia for older adults in either experiment. We found no age-related difference in reminiscence (Experiments 1 and 2), though there was a substantial difference in intertest forgetting (Experiments 1 and 2). Older, relative to young, adults produced more forgetting, most of which occurred between Tests 1 and 2 (Experiments 1 and 2). Furthermore, older, relative to young, adults produced more intrusions. We failed to identify a relationship between intrusions and intertest forgetting. We suggest that the age-related difference in intertest forgetting may be due to less efficient reinstatement of cues at test by older adults. The present findings reveal that intertest forgetting plays a critical role in hypermnesic recall, particularly for older adults. PMID:10946539

  2. Age-related differences in working memory updating components.

    PubMed

    Linares, Rocío; Bajo, M Teresa; Pelegrina, Santiago

    2016-07-01

    The aim of this study was to investigate possible age-related changes throughout childhood and adolescence in different component processes of working memory updating (WMU): retrieval, transformation, and substitution. A set of numerical WMU tasks was administered to four age groups (8-, 11-, 14-, and 21-year-olds). To isolate the effect of each of the WMU components, participants performed different versions of a task that included different combinations of the WMU components. The results showed an expected overall decrease in response times and an increase in accuracy performance with age. Most important, specific age-related changes in the retrieval component were found, demonstrating that the effect of retrieval on accuracy was larger in children than in adolescents or young adults. These findings indicate that the availability of representations from outside the focus of attention may change with age. Thus, the retrieval component of updating could contribute to the age-related changes observed in the performance of many updating tasks. PMID:26985577

  3. Hhip haploinsufficiency sensitizes mice to age-related emphysema.

    PubMed

    Lao, Taotao; Jiang, Zhiqiang; Yun, Jeong; Qiu, Weiliang; Guo, Feng; Huang, Chunfang; Mancini, John Dominic; Gupta, Kushagra; Laucho-Contreras, Maria E; Naing, Zun Zar Chi; Zhang, Li; Perrella, Mark A; Owen, Caroline A; Silverman, Edwin K; Zhou, Xiaobo

    2016-08-01

    Genetic variants in Hedgehog interacting protein (HHIP) have consistently been associated with the susceptibility to develop chronic obstructive pulmonary disease and pulmonary function levels, including the forced expiratory volume in 1 s (FEV1), in general population samples by genome-wide association studies. However, in vivo evidence connecting Hhip to age-related FEV1 decline and emphysema development is lacking. Herein, using Hhip heterozygous mice (Hhip(+/-)), we observed increased lung compliance and spontaneous emphysema in Hhip(+/-) mice starting at 10 mo of age. This increase was preceded by increases in oxidative stress levels in the lungs of Hhip(+/-) vs. Hhip(+/+) mice. To our knowledge, these results provide the first line of evidence that HHIP is involved in maintaining normal lung function and alveolar structures. Interestingly, antioxidant N-acetyl cysteine treatment in mice starting at age of 5 mo improved lung function and prevented emphysema development in Hhip(+/-) mice, suggesting that N-acetyl cysteine treatment limits the progression of age-related emphysema in Hhip(+/-) mice. Therefore, reduced lung function and age-related spontaneous emphysema development in Hhip(+/-) mice may be caused by increased oxidative stress levels in murine lungs as a result of haploinsufficiency of Hhip. PMID:27444019

  4. Mechanical properties and in vitro degradation of self-reinforced radiopaque bioresorbable polylactide fibres.

    PubMed

    Nuutinen, Juha-Pekka; Clerc, Claude; Törmälä, Pertti

    2003-01-01

    The aim of this study was to evaluate the effect of the radiopaque filler, barium sulfate (BaSO4), on the mechanical properties of self-reinforced bioresorbable fibres. The bioresorbable polymer was a copolymer of L- and D-lactide with an L/D monomer ratio of 96:4 (96L/4D PLA). The fibres were manufactured using an extrusion and a drawing process. Three different methods of processing the composites were studied. The materials were blended prior to extrusion. In the first method, the BaSO4 powder was mixed with the polymer granulates by hand (manual blending). The blend was then processed using a twin-screw extruder. The second and third methods utilized a single-screw extruder. In the second method, the BaSO4 powder was manually mixed with the polymer prior to extrusion. In the third method, the BaSO4 powder was mechanically attached on the polymer granulates (mechanical blending) prior to extrusion. The mechanical and chemical properties of the radiopaque bioresorbable fibres were measured after processing and during in vitro degradation. The fibres were gamma, plasma or EtO sterilized. There was no statistical difference in the mechanical properties of the fibres when manufactured using the twin-screw extrusion with manual blending or the single-screw extrusion with mechanical blending. The gamma sterilization markedly decreased the initial intrinsic viscosity of all fibres, whereas the plasma and EtO sterilization methods had no effect on the initial intrinsic viscosity. During in vitro testing, the loss in the intrinsic viscosity occurred at the same rate whether the fibres were loaded with the barium sulfate or not. PMID:12903735

  5. Heterogeneous electro-Fenton using modified iron-carbon as catalyst for 2,4-dichlorophenol degradation: influence factors, mechanism and degradation pathway.

    PubMed

    Zhang, Chao; Zhou, Minghua; Ren, Gengbo; Yu, Xinmin; Ma, Liang; Yang, Jie; Yu, Fangke

    2015-03-01

    Modified iron-carbon with polytetrafluoroethylene (PTFE) was firstly investigated as heterogeneous electro-Fenton (EF) catalyst for 2,4-dichlorophenol (2,4-DCP) degradation in near neutral pH condition. The catalyst was characterized by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD), and the effects of some important operating parameters such as current intensity and pH on the 2,4-DCP degradation were investigated. After the catalyst modification with 20% PTFE, the degradation performance maintained well with much lower iron leaching, and at current intensity 100 mA, initial pH 6.7, catalyst loading 6 g/L, the degradation efficiency of 2,4-DCP could exceed 95% within 120 min treatment. Two-stage pseudo first-order kinetics of 2,4-DCP degradation was observed, including a slow anodic oxidation stage (first-stage) and much faster heterogeneous EF oxidation (second-stage), in which the automatic drop of pH in the first-stage initiated the Fe(2+) release from micro-electrolysis and thus benefited to the subsequent EF reaction. Aromatic intermediates such as 3,5-dichlorocatechol, 4,6-dichlororesorcinol and 2-chlorohydroquinone were detected by GC-MS. Oxalic acid, acetic acid, formic acid and Cl(-) were quantified by ion chromatograph. Based on these analysis as well as the detection of H₂O₂ and OH, a possible mechanism and degradation pathway for 2,4-DCP were proposed. This work demonstrated that such a heterogeneous EF using cheap modified Fe-C catalyst was promising for organic wastewater treatment in initial neutral pH condition. PMID:25559487

  6. Differential proteomics analysis of proteins from human diabetic and age-related cataractous lenses

    PubMed Central

    Zhu, Jing; Shao, Jun; Yao, Yong; Chu, Zhao Dong; Yu, Qian Qian; Zhao, Wei; Lin, Qing; Zhang, Zi Yin

    2013-01-01

    Backgound: To investigate the differential lens proteomics between diabetic cataract, age-related cataract, and natural subjects. Materials and Methods: Two-dimensional electrophoresis (2-DE), mass spectrometry (MS), and enzyme-linked immunosorbent assay (ELISA) were employed. Total soluble proteins in lenses of type I diabetic cataract, age-related cataract (nondiabetic) patients, and normal control were extracted and subjected to 2-DE. The differential protein spots were recovered, digested with trypsin, and further applied to MALDI-TOF-MS. ELISA analysis was used to determine the levels of differential proteins in lenses of three groups. Results: 2-DE analysis reflected that lens proteins of normal control, diabetic, and age-related cataract subjects were in the section of pH 5-9 and the relative molecular weights were 14-97 kDa, while relative molecular weight of more abundant crystallines was localized at 20-31 kDa. five differential protein spots were detected and identified using MALDI-TOF-MS, including beta-crystallin A3, alpha-crystallin B chain, chain A of crystal structure of truncated human beta-B1-crystallin, beta-crystallin B1, and an interesting unnamed protein product highly similar to alpha-crystallin B chain, respectively. ELISA analysis revealed that lenses of diabetic cataract patients should contain significantly more concentrations of beta-crystallin A3, alpha-crystallin B chain, and beta-crystallin B1 than those of age-related cataract patients and normal control. Conclusion: This study clearly reflected the differential proteins of diabetic cataract, age-related cataract lenses compared with natural subjects, and it is helpful for the further research on the principles and mechanisms of different types of cataract. PMID:24520233

  7. Age-related change of technetium-99m-HMDP distribution in the skeleton

    SciTech Connect

    Kigami, Yusuke; Yamamoto, Itsuo; Ohnishi, Hideo

    1996-05-01

    To understand age-related changes of whole-body and regional skeletal metabolism, it is important to investigate the mechanisms of age-related bone loss and to develop suitable treatments for it. Bone biopsies show metabolism of the particular site examined while biochemical markers for bone metabolism reflect total skeletal metabolis. Bone scintigraphy is a convenient and simple way to analyze whole-body and regional skeletal metabolism. We attempted to study and understand age-related changes in bone metabolism by quantifying the bone scan and correlating it with biochemical bone metabolic markers. The whole-body skeletal uptake (WBSU) and whole-body skeletal tracer distribution pattern were studied in men and women by bone scintigraphy using {sup 99m}Tc-hydroxy-methane-diphosphonate (HMDP). Bone scans were performed using a standard protocol and quantified by setting regions of interest (ROIs) on selected regions. WBSU and the skeletal distribution pattern were compared with simultaneously obtained serum biochemical markers. WBSU showed an increase with age in both sexes, but in women, uptake in the head and legs increased more relatively than in the thoracic region, while in men no such tendency was observed. Increase of WBSU and relative increase of uptakes in the head demonstrated a weak correlation with the serum levels of alkaline phosphatase and type 1 collagen metabolites. These results show an age-related increase of skeletal turnover and sex-dependent regional skeletal metabolism. The age-related changes seen in bone scintigrams might be a sign of progressive bone loss, reflecting changes in local bone matabolism. 23 refs., 3 figs., 1 tab.

  8. Degradation Mechanisms of Solution-Processed Planar Perovskite Solar Cells: Thermally Stimulated Current Measurement for Analysis of Carrier Traps.

    PubMed

    Qin, Chuanjiang; Matsushima, Toshinori; Fujihara, Takashi; Potscavage, William J; Adachi, Chihaya

    2016-01-20

    Degradation mechanisms of CH3 NH3 PbI3 -based planar perovskite solar cells (PSCs) are investigated using a thermally stimulated current technique. Hole traps lying above the valence-band edge of the CH3 NH3 PbI3 are detected in PSCs degraded by continuous simulated solar illumination. One source of the hole traps is the photodegradation of CH3 NH3 PbI3 in the presence of water. PMID:26598398

  9. Degradation kinetics and mechanism of antibiotic ceftiofur in recycled water derived from a beef farm.

    PubMed

    Li, Xiaolin; Zheng, Wei; Machesky, Michael L; Yates, Scott R; Katterhenry, Michael

    2011-09-28

    Ceftiofur is a third-generation cephalosporin antibiotic that has been widely used to treat bacterial infections in concentrated animal feeding operations (CAFOs). Land application of CAFO waste may lead to the loading of ceftiofur residues and its metabolites to the environment. To understand the potential contamination of the antibiotic in the environment, the degradation kinetics and mechanisms of ceftiofur in solutions blended with and without the recycled water derived from a beef farm were investigated. The transformation of ceftiofur in aqueous solutions in the presence of the CAFO recycled water was the combined process of hydrolysis and biodegradation. The total degradation rates of ceftiofur at 15 °C, 25 °C, 35 °C, and 45 °C varied from 0.4-2.8×10(-3), 1.4-4.4×10(-3), 6.3-11×10(-3), and 11-17×10(-3) h(-1), respectively, in aqueous solutions blended with 1 to 5% CAFO recycled water. Hydrolysis of ceftiofur increased with incubation temperature from 15 to 45 °C. The biodegradation rates of ceftiofur were also temperature-dependent and increased with the application amounts of the recycled CAFO water. Cef-aldehyde and desfuroylceftiofur (DFC) were identified as the main biodegradation and hydrolysis products, respectively. This result suggests that the primary biodegradation mechanism of ceftiofur was the cleavage of the β-lactam ring, while hydrolytic cleavage occurred at the thioester bond. Unlike DFC and ceftiofur, cef-aldehyde does not contain a β-lactam ring and has less antimicrobial activity, indicating that the biodegradation of ceftiofur in animal wastewater may mitigate the potentially adverse impact of the antibiotic to the environment. PMID:21863813

  10. Processing and mechanical behavior of lamellar structured degradable magnesium-hydroxyapatite implants.

    PubMed

    Ratna Sunil, B; Ganapathy, C; Sampath Kumar, T S; Chakkingal, Uday

    2014-12-01

    Multilayered (laminated) composites exhibit tunable mechanical behavior compared to bulk materials due to the presence of more interfaces and therefore magnesium based composites are gaining wide popularity as biodegradable materials targeted for temporary implant applications. The objective of the present work is to fabricate magnesium based lamellar metal matrix composites (MMCs) for degradable implant applications. Nano-hydroxyapatite (HA) powder was selected as the secondary phase and lamellar structured magnesium-nano-hydroxyapatite (Mg-HA) composites of 8, 10 and 15wt% HA were fabricated by ball milling and spark plasma sintering. It was found that HA particles were coated on the Mg flakes after 20h of ball milling carried out using tungsten carbide (WC) as the milling media. Spark plasma sintering of the milled powders resulted in the formation of lamellar structure of Mg with the presence of HA and magnesium oxide (MgO) at the inter-lamellar sites of the composites. Phase analysis of the milled powder by an X-ray diffraction (XRD) method confirms the presence of HA and MgO along with Mg after sintering. Corrosion behavior of the composites investigated by potentiodynamic polarization tests shows a reduction in the inter-lamellar corrosion with increase in HA content and the best corrosion resistance is found for the Mg-10% HA composite. This composite also exhibits maximum Vickers hardness. Young׳s modulus and fracture toughness measured by nano-indentation method were higher for the Mg-8% HA composite. The results thus suggest that lamellar structured Mg composites with 8% and 10% HA show promise for temporary degradable orthopedic implant applications because of their improved corrosion resistance and superior mechanical properties. PMID:25241282

  11. Potential corrosion and degradation mechanisms of Zircaloy cladding on spent nuclear fuel in a tuff repository

    SciTech Connect

    Rothman, A.J.

    1984-09-01

    A literature review and analysis were made of corrosion and degradation processes applicable to Zircaloy cladding on spent nuclear fuel in a tuff repository. In particular, lifetime sought for the Zircaloy is 10,000 years. Among the potential failure mechanisms examined were: oxidation by steam, air, and water, including the effects of ions whose presence is anticipated in the water; mechanical overload; stress (creep) rupture; stress-corrosion cracking (SCC); and delayed failure due to hydride cracking. The conclusion is that failure due to oxidation is not credible, although a few experiments are suggested to confirm the effect of aqueous fluoride on the Zircaloy cladding. Mechanical overload is not a problem, and failure from stress-rupture does not appear likely based on a modified Larson-Miller analysis. Analysis shows that delayed hydride cracking is not anticipated for the bulk of spent fuel pins. However, for a minority of pins under high stress, there is some uncertainty in the analysis as a result of: (1) uncertainty about crack depths in spent fuel claddings and (2) the effect of slow cooling on the formation of radially oriented hydride precipitates. Experimental resolution is called for. Finally, insufficient information is currently available on stress-corrosion cracking. While evidence is presented that SCC failure is not likely to occur, it is difficult to demonstrate this conclusively because the process is not clearly understood and data are limited. Further experimental work on SCC susceptibility is especially needed.

  12. Thermochemical Degradation Mechanisms for the Reinforced Carbon/Carbon Panels on the Space Shuttle

    NASA Technical Reports Server (NTRS)

    Jacobson, Nathan S.; Rapp, Robert A.

    1995-01-01

    The wing leading edge and nose cone of the Space Shuttle are fabricated from a reinforced carbon/carbon material (RCC). The material attains its oxidation resistance from a diffusion coating of SiC and a glass sealant. During re-entry, the RCC material is subjected to an oxidizing high temperature environment, which leads to degradation via several mechanisms. These mechanisms include oxidation to form a silica scale, reaction of the SiO2 with the SiC to evolve gaseous products, viscous flow of the glass, and vaporization of the glass. Each of these is discussed in detail. Following extended service and many missions, the leading-edge wing surfaces have exhibited small pinholes. A chloridation/oxidation mechanism is proposed to arise from the NaCl deposited on the wings from the sea-salt laden air in Florida. This involves a local chloridation reaction of the SiC and subsequent re-oxidation at the external surface. Thermodynamic calculations indicate the feasibility of these reactions at active pits. Kinetic calculations predict pore depths close to those observed.

  13. Formation of degradation compounds from lignocellulosic biomass in the biorefinery: sugar reaction mechanisms.

    PubMed

    Rasmussen, Helena; Sørensen, Hanne R; Meyer, Anne S

    2014-02-19

    The degradation compounds formed during pretreatment when lignocellulosic biomass is processed to ethanol or other biorefinery products include furans, phenolics, organic acids, as well as mono- and oligomeric pentoses and hexoses. Depending on the reaction conditions glucose can be converted to 5-(hydroxymethyl)-2-furaldehyde (HMF) and/or levulinic acid, formic acid and different phenolics at elevated temperatures. Correspondingly, xylose can follow different reaction mechanisms resulting in the formation of furan-2-carbaldehyde (furfural) and/or various C-1 and C-4 compounds. At least four routes for the formation of HMF from glucose and three routes for furfural formation from xylose are possible. In addition, new findings show that biomass monosaccharides themselves can react further to form pseudo-lignin and humins as well as a wide array of other compounds when exposed to high temperatures. Hence, several aldehydes and ketones and many different organic acids and aromatic compounds may be generated during hydrothermal treatment of lignocellulosic biomass. The reaction mechanisms are of interest because the very same compounds that are possible inhibitors for biomass processing enzymes and microorganisms may be valuable biobased chemicals. Hence a new potential for industrial scale synthesis of chemicals has emerged. A better understanding of the reaction mechanisms and the impact of the reaction conditions on the product formation is thus a prerequisite for designing better biomass processing strategies and forms an important basis for the development of new biorefinery products from lignocellulosic biomass as well. PMID:24412507

  14. Degradation mechanism of SiC/super {alpha}{sub 2} composite due to interfacial reaction

    SciTech Connect

    Ochiai, S.; Inoue, T.; Fujita, T.; Hojo, M.; Dudek, H.J.; Leucht, R.

    1999-10-01

    The degradation mechanism of SiC(SCS-6)/Super {alpha}{sub 2} composite due to the interfacial reaction was studied using single-fiber composite specimens fabricated by the sputtering method, heat treated at 1,273 K for various times, and tensile tested at room temperature. The main results are summarized as follows. (1) The tensile strength was reduced with progress of interfacial reaction by the formed defects on the fiber surface, while the formation of the reaction layers in the matrix side was not the direct reason for the reduction. (2) From the fracture mechanical analysis of the experimentally observed relation of the size and shape of the surface defects to the fiber strength, the fracture toughness of the fiber employed in the present work was estimated to be 2 to 4 MPa {radical}m. (3) The change in distribution of strength of the reacted fiber with progressing reaction was simulated successfully by combining the Monte Carlo method with the Weibull distribution function for the strength of the unreacted fiber, the Gumbell distribution function for the maximum effective size of the surface defect of the reacted fiber, and the fracture mechanics.

  15. Age-related changes in total protein and collagen metabolism in rat liver.

    PubMed

    Mays, P K; McAnulty, R; Laurent, G J

    1991-12-01

    Liver collagen levels are determined by a balance between synthesis and degradation, processes known to have rapid rates in growing animals. We report age-related changes in liver collagen synthesis and degradation rates, as well as protein synthesis rates, in rats at five ages from 1 to 24 mo. Fractional collagen synthesis rates were determined after injection of [14C]proline with a flooding dose of unlabeled proline and its incorporation as hydroxy-[14C]proline into proteins. Fractional protein synthesis rates were based on the uptake of [14C]proline into proteins. Fractional collagen degradation rates were calculated from the difference between collagen fractional synthesis and deposition rates. Fractional rates of collagen synthesis were similar between 1 mo (23.0% +/- 4.6%/day) and 24 mo (19.6% +/- 3.4%/day) of age. Collagen deposition into the extracellular matrix was extremely low at every age studied; therefore degradation pathways accounted for the bulk of the collagen synthesized. The mean fractional synthesis rate for the total protein pool was unaltered between 1 mo (105.0% +/- 7.2%/day) and 15 mo (89.9% +/- 6.0%/day) of age, after which it increased to 234.9% +/- 33.0%/day (p less than 0.05) by 24 mo of age. These results indicate that liver collagen and total protein synthesis rates were maintained at relatively high levels during development and maturity but that protein synthesis rates were highest in senescent animals. PMID:1959872

  16. Aquaporin-1 Translocation and Degradation Mediates the Water Transportation Mechanism of Acetazolamide

    PubMed Central

    Gao, Junwei; Han, Jing; Pan, Xueyang; Pan, Yan; Tie, Lu; Li, Xuejun

    2012-01-01

    Background Diuretic agents are widely used on the treatment of water retention related diseases, among which acetazolamide (AZA) acts originally as a carbonic anhydrase (CA) inhibitor. Aquaporin-1 (AQP1) being located in renal proximal tubules is required for urine concentration. Previously our lab has reported AZA putatively modulated AQP1. Aim of this study is to testify our hypothesis that regulating AQP1 may mediate diuretic effect of AZA. Methodology/Principal Findings For in vivo study, we utilized Sprague Dawley rats, as well as AQP1 knock-out (AQP1−/−) mice to examine urine volume, and human kidney-2 (HK-2) cell line was used for in vitro mechanism study. In our present study we found that AZA decreased CAs activity initially but the activity gradually recovered. Contrarily, diuretic effect was consistently significant. AQP1 protein expression was significantly decreased on day 7 and 14. By utilizing AQP1−/− mice, we found diuretic effect of AZA was cancelled on day 14, while urine volume continuously increased in wild-type mice. Surface plasmon resonance (SPR) results indicated AQP1 was physiologically bound by myosin heavy chain (MHC), immunoprecipitation and immunofluorescence results confirmed this protein interaction. In vitro study results proved AZA facilitated AQP1 translocation onto cell membrane by promoting interaction with MHC, dependent on ERK/ myosin light chain kinase (MLCK) pathway activation. MHC inhibitor BDM and ERK inhibitor U0126 both abolished above effect of AZA. Eventually AZA induced AQP1 ubiquitination, while proteasome inhibitor MG132 reversed AZA's down-regulating effect upon AQP1. Conclusions/Significance Our results identified AZA exerted diuretic effect through an innovative mechanism by regulating AQP1 and verified its inhibitory mechanism was via promoting MHC-dependent translocation onto cell membrane and then ubiquitin mediated degradation, implicating a novel mechanism and target for diuretic agent discovering

  17. Age-Related Changes in Skeletal Muscle of Cattle.

    PubMed

    Costagliola, A; Wojcik, S; Pagano, T B; De Biase, D; Russo, V; Iovane, V; Grieco, E; Papparella, S; Paciello, O

    2016-03-01

    Sarcopenia, the age-related loss of muscle mass and strength, is a multifactorial condition that represents a major healthcare concern for the elderly population. Although its morphologic features have been extensively studied in humans, animal models, and domestic and wild animals, only a few reports about spontaneous sarcopenia exist in other long-lived animals. In this work, muscle samples from 60 healthy Podolica-breed old cows (aged 15-23 years) were examined and compared with muscle samples from 10 young cows (3-6 years old). Frozen sections were studied through standard histologic and histoenzymatic procedures, as well as by immunohistochemistry, immunofluorescence, and Western blot analysis. The most prominent age-related myopathic features seen in the studied material included angular fiber atrophy (90% of cases), mitochondrial alterations (ragged red fibers, 70%; COX-negative fibers, 60%), presence of vacuolated fibers (75%), lymphocytic (predominantly CD8+) inflammation (40%), and type II selective fiber atrophy (40%). Immunohistochemistry revealed increased expression of major histocompatibility complex I in 36 cases (60%) and sarcoplasmic accumulations of β-amyloid precursor protein-positive material in 18 cases (30%). In aged cows, muscle atrophy was associated with accumulation of myostatin. Western blot analysis indicated increased amount of both proteins-myostatin and β-amyloid precursor protein-in muscles of aged animals compared with controls. These findings confirm the presence of age-related morphologic changes in cows similar to human sarcopenia and underline the possible role of amyloid deposition and subsequent inflammation in muscle senescence. PMID:26869152

  18. Rapid degradation of phenol by ultrasound-dispersed nano-metallic particles (NMPs) in the presence of hydrogen peroxide: A possible mechanism for phenol degradation in water.

    PubMed

    Singh, Jiwan; Yang, Jae-Kyu; Chang, Yoon-Young

    2016-06-15

    The present study was carried out to investigate the degradation of phenol by ultrasonically dispersed nano-metallic particles (NMPs) in an aqueous solution of phenol. Leaching liquor from automobile shredder residue (ASR) was used to obtain the NMPs. The prepared NMPs were analyzed by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), and by X-ray diffraction (XRD). The SEM images show that the diameters of the NMPs were less than 50 nm. An SEM-EDX elemental analysis reveals that Fe was the most commonly found element (weight %) in the NMPs. The FTIR and XRD peaks indicate the presence of metals oxides on the surfaces of the NMPs. The results of the XPS analysis indicate that various elements (e.g., C, O, Zn, Cu, Mn, Fe) are present on the surfaces of the NMPs. The effects of the NMP dose, the initial solution pH, and of different concentrations of phenol and H2O2 on the phenol degradation characteristics were evaluated. The results of this study demonstrate that phenol degradation can be improved by increasing the amount of NMPs, whereas it is reduced with an increase in the phenol concentration. The degradation of phenol by ultrasonically dispersed NMPs followed the pseudo-first-order kinetics. The probable mechanism of phenol degradation by ultrasonically dispersed NMPs was the oxidation of phenol caused by the hydroxyl radicals produced during the reaction between H2O2 and the NMPs during the ultrasonication process. PMID:27038433

  19. Age-related decline in differentiated neural responses to rare target versus frequent standard stimuli.

    PubMed

    Mott, Katherine K; Alperin, Brittany R; Holcomb, Phillip J; Daffner, Kirk R

    2014-10-31

    One mechanism hypothesized to contribute to cognitive aging is the failure to recruit specialized neural modules and generate differentiated neural responses to various classes of stimuli. Here, ERPs were used to examine the extent to which target and standard stimulus types were processed differently by well-matched adults ages 19-99. Subjects responded to designated visual target letters under low and high load conditions. Temporospatial PCA was used to parse the P3b component, an index of categorization/memory updating. The P3b amplitude difference between targets and standards decreased substantially as a function of age. Dedifferentiation began in middle age, and continued into old-old age. The reduced differentiation of neural responses was driven by an age-related decline in the size of the P3b to targets and an age-related increase in the P3b to standards. Larger P3b amplitude to standards among older subjects was associated with higher executive capacity and better task performance. In summary, dedifferentiation begins relatively early in adulthood and progresses in a linear fashion throughout the lifespan. The age-related augmentation of the P3b to standards appears to reflect a compensatory mechanism that helps maintain task performance. PMID:25171804

  20. Age-related decline in differentiated neural responses to rare target versus frequent standard stimuli

    PubMed Central

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

    2014-01-01

    One mechanism hypothesized to contribute to cognitive aging is the failure to recruit specialized neural modules and generate differentiated neural responses to various classes of stimuli. Here, ERPs were used to examine the extent to which target and standard stimulus types were processed differently by well-matched adults ages 19–99. Subjects responded to designated visual target letters under low and high load conditions. Temporospatial PCA was used to parse the P3b component, an index of categorization/memory updating. The P3b amplitude difference between targets and standards decreased substantially as a function of age. Dedifferentiation began in middle age, and continued into old-old age. The reduced differentiation of neural responses was driven by an age-related decline in the size of the P3b to targets and an age-related increase in the P3b to standards. Larger P3b amplitude to standards among older subjects was associated with higher executive capacity and better task performance. In summary, dedifferentiation begins relatively early in adulthood and progresses in a linear fashion throughout the lifespan. The age-related augmentation of the P3b to standards appears to reflect a compensatory mechanism that helps maintain task performance. PMID:25171804

  1. Age-Related Macular Degeneration: Advances in Management and Diagnosis.

    PubMed

    Yonekawa, Yoshihiro; Miller, Joan W; Kim, Ivana K

    2015-01-01

    Age-related macular degeneration (AMD) is the most common cause of irreversible visual impairment in older populations in industrialized nations. AMD is a late-onset deterioration of photoreceptors and retinal pigment epithelium in the central retina caused by various environmental and genetic factors. Great strides in our understanding of AMD pathogenesis have been made in the past several decades, which have translated into revolutionary therapeutic agents in recent years. In this review, we describe the clinical and pathologic features of AMD and present an overview of current diagnosis and treatment strategies. PMID:26239130

  2. Age-related macular degeneration: Complement in action.

    PubMed

    van Lookeren Campagne, Menno; Strauss, Erich C; Yaspan, Brian L

    2016-06-01

    The complement system plays a key role in host-defense against common pathogens but must be tightly controlled to avoid inflammation and tissue damage. Polymorphisms in genes encoding two important negative regulators of the alternative complement pathway, complement factor H (CFH) and complement factor I (CFI), are associated with the risk for Age-Related Macular Degeneration (AMD), a leading cause of vision impairment in the ageing population. In this review, we will discuss the genetic basis of AMD and the potential impact of complement de-regulation on disease pathogenesis. Finally, we will highlight recent therapeutic approaches aimed at controlling complement activation in patients with AMD. PMID:26742632

  3. Effects of Vitreomacular Adhesion on Age-Related Macular Degeneration

    PubMed Central

    Kang, Eui Chun; Koh, Hyoung Jun

    2015-01-01

    Herein, we review the association between vitreomacular adhesion (VMA) and neovascular age-related macular degeneration (AMD). Meta-analyses have shown that eyes with neovascular AMD are twice as likely to have VMA as normal eyes. VMA in neovascular AMD may induce inflammation, macular traction, decrease in oxygenation, sequestering of vascular endothelial growth factor (VEGF), and other cytokines or may directly stimulate VEGF production. VMA may also interfere with the treatment effects of anti-VEGF therapy, which is the standard treatment for neovascular AMD, and releasing VMA can improve the treatment response to anti-VEGF treatment in neovascular AMD. We also reviewed currently available methods of relieving VMA. PMID:26425354

  4. Present and Possible Therapies for Age-Related Macular Degeneration

    PubMed Central

    Kamal, Ahmed

    2014-01-01

    Age-related macular degeneration (AMD) is the most common cause of blindness in the elderly population worldwide and is defined as a chronic, progressive disorder characterized by changes occurring within the macula reflective of the ageing process. At present, the prevalence of AMD is currently rising and is estimated to increase by a third by 2020. Although our understanding of the several components underpinning the pathogenesis of this condition has increased significantly, the treatment options for this condition remain substantially limited. In this review, we outline the existing arsenal of therapies available for AMD and discuss the additional role of further novel therapies currently under investigation for this debilitating disease. PMID:25097787

  5. The role of mitochondria in age-related hearing loss.

    PubMed

    Chen, Hengchao; Tang, Jianguo

    2014-02-01

    Age-related hearing loss (ARHL), the hearing loss associated with aging, is a vital problem in present society. The severity of hearing loss is possibly associated with the degeneration of cochlear cells. Mitochondria play a key role in the energy supply, cellular redox homeostasis, signaling, and regulation of programmed cell death. In this review, we focus on the central role of mitochondria in ARHL. The mitochondrial redox imbalance and mitochondrial DNA mutation might collaboratively involve in the process of cochlear senescence in response to the aging stress. Subsequent responses, including alteration of mitochondrial biogenesis, mitophagy, apoptosis and paraptosis, participate in the aging process from different respects. PMID:24202185

  6. [Diagnostic Criteria for Atrophic Age-related Macular Degeneration].

    PubMed

    Takahashi, Kanji; Shiraga, Fumio; Ishida, Susumu; Kamei, Motohiro; Yanagi, Yasuo; Yoshimura, Nagahisa

    2015-10-01

    Diagnostic criteria for dry age-related macular degeneration is described. Criteria include visual acuity, fundscopic findings, diagnostic image findings, exclusion criteria and classification of severity grades. Essential findings to make diagnosis as "geographic atrophy" are, 1) at least 250 μm in diameter, 2) round/oval/cluster-like or geographic in shape, 3) sharp delineation, 4) hypopigmentation or depigmentation in retinal pigment epithelium, 5) choroidal vessels are more visible than in surrounding area. Severity grades were classified as mild, medium and severe by relation of geographic atrophy to the fovea and attendant findings. PMID:26571627

  7. [Glaucoma and age-related macular degeneration intricacy].

    PubMed

    Valtot, F

    2008-07-01

    Age-related macular degeneration (AMD) is the leading cause of legal blindness among the elderly in Western nations. Age is also a well-known and well-evidenced risk factor for glaucoma. With increasing longevity and the rising prevalence of older people around the world, more and more patients will have glaucoma and AMD. Clinical evaluation of these patients still poses problems for clinicians. It is very important to order the right tests at the right time to distinguish glaucomatous defects from those caused by retinal lesions, because appropriate therapy has a beneficial effect on slowing or halting damage. PMID:18957915

  8. Age-Related Macular Degeneration: Advances in Management and Diagnosis

    PubMed Central

    Yonekawa, Yoshihiro; Miller, Joan W.; Kim, Ivana K.

    2015-01-01

    Age-related macular degeneration (AMD) is the most common cause of irreversible visual impairment in older populations in industrialized nations. AMD is a late-onset deterioration of photoreceptors and retinal pigment epithelium in the central retina caused by various environmental and genetic factors. Great strides in our understanding of AMD pathogenesis have been made in the past several decades, which have translated into revolutionary therapeutic agents in recent years. In this review, we describe the clinical and pathologic features of AMD and present an overview of current diagnosis and treatment strategies. PMID:26239130

  9. Superoxide Dismutase 1 Loss Disturbs Intracellular Redox Signaling, Resulting in Global Age-Related Pathological Changes

    PubMed Central

    2014-01-01

    Aging is characterized by increased oxidative stress, chronic inflammation, and organ dysfunction, which occur in a progressive and irreversible manner. Superoxide dismutase (SOD) serves as a major antioxidant and neutralizes superoxide radicals throughout the body. In vivo studies have demonstrated that copper/zinc superoxide dismutase-deficient (Sod1−/−) mice show various aging-like pathologies, accompanied by augmentation of oxidative damage in organs. We found that antioxidant treatment significantly attenuated the age-related tissue changes and oxidative damage-associated p53 upregulation in Sod1−/− mice. This review will focus on various age-related pathologies caused by the loss of Sod1 and will discuss the molecular mechanisms underlying the pathogenesis in Sod1−/− mice. PMID:25276767

  10. Age-related hearing impairment and the triad of acquired hearing loss

    PubMed Central

    Yang, Chao-Hui; Schrepfer, Thomas; Schacht, Jochen

    2015-01-01

    Understanding underlying pathological mechanisms is prerequisite for a sensible design of protective therapies against hearing loss. The triad of age-related, noise-generated, and drug-induced hearing loss displays intriguing similarities in some cellular responses of cochlear sensory cells such as a potential involvement of reactive oxygen species (ROS) and apoptotic and necrotic cell death. On the other hand, detailed studies have revealed that molecular pathways are considerably complex and, importantly, it has become clear that pharmacological protection successful against one form of hearing loss will not necessarily protect against another. This review will summarize pathological and pathophysiological features of age-related hearing impairment (ARHI) in human and animal models and address selected aspects of the commonality (or lack thereof) of cellular responses in ARHI to drugs and noise. PMID:26283913

  11. Preventing Age-Related Decline of Gut Compartmentalization Limits Microbiota Dysbiosis and Extends Lifespan.

    PubMed

    Li, Hongjie; Qi, Yanyan; Jasper, Heinrich

    2016-02-10

    Compartmentalization of the gastrointestinal (GI) tract of metazoans is critical for health. GI compartments contain specific microbiota, and microbiota dysbiosis is associated with intestinal dysfunction. Dysbiosis develops in aging intestines, yet how this relates to changes in GI compartmentalization remains unclear. The Drosophila GI tract is an accessible model to address this question. Here we show that the stomach-like copper cell region (CCR) in the middle midgut controls distribution and composition of the microbiota. We find that chronic activation of JAK/Stat signaling in the aging gut induces a metaplasia of the gastric epithelium, CCR decline, and subsequent commensal dysbiosis and epithelial dysplasia along the GI tract. Accordingly, inhibition of JAK/Stat signaling in the CCR specifically prevents age-related metaplasia, commensal dysbiosis and functional decline in old guts, and extends lifespan. Our results establish a mechanism by which age-related chronic inflammation causes the decline of intestinal compartmentalization and microbiota dysbiosis, limiting lifespan. PMID:26867182

  12. Mechanical degradation of TiO2 nanotubes with and without nanoparticulate silver coating.

    PubMed

    Shivaram, Anish; Bose, Susmita; Bandyopadhyay, Amit

    2016-06-01

    The primary objective of this research was to evaluate the extent of mechanical degradation on TiO2 nanotubes on Ti with and without nano-particulate silver coating using two different lengths of TiO2 nanotubes-300nm and ~1µm, which were fabricated on commercially pure Titanium (cp-Ti) rods using anodization method using two different electrolytic mediums-(1) deionized (DI) water with 1% HF, and (2) ethylene glycol with 1% HF, 0.5wt% NH4F and 10% DI water. Nanotubes fabricated rods were implanted into equine cadaver bone to evaluate mechanical damage at the surface. Silver was electrochemically deposited on these nanotubes and using a release study, silver ion concentrations were measured before and after implantation, followed by surface characterization using a Field Emission Scanning Electron Microscope (FESEM). In vitro cell-material interaction study was performed using human fetal osteoblast cells (hFOB) to understand the effect of silver coating using an MTT assay for proliferation and to determine any cytotoxic effect on the cells and to study its biocompatibility. No significant damage due to implantation was observed for nanotubes up to ~1µm length under current experimental conditions. Cell-materials interaction showed no cytotoxic effects on the cells due to silver coating and anodization of samples. PMID:27017285

  13. A conserved mechanism of TOR-dependent RCK-mediated mRNA degradation regulates autophagy

    PubMed Central

    Park, Yoon-Dong; Qiu, Jin; Vural, Ali; Zhang, Nannan; Waterman, Scott R.; Blewett, Nathan H.; Myers, Timothy G.; Maraia, Richard J.; Kehrl, John H.; Uzel, Gulbu; Klionsky, Daniel J.; Williamson, Peter R.

    2015-01-01

    Autophagy is an essential eukaryotic pathway requiring tight regulation to maintain homeostasis and preclude disease. Using yeast and mammalian cells, we report a conserved mechanism of autophagy regulation by RNA helicase RCK family members in association with the decapping enzyme Dcp2. Under nutrient-replete conditions, Dcp2 undergoes TOR-dependent phosphorylation and associates with RCK members to form a complex with autophagy-related (ATG) mRNA transcripts, leading to decapping, degradation and autophagy suppression. Simultaneous with the induction of ATG mRNA synthesis, starvation reverses the process, facilitating ATG mRNA accumulation and autophagy induction. This conserved post-transcriptional mechanism modulates fungal virulence and the mammalian inflammasome, the latter providing mechanistic insight into autoimmunity reported in a patient with a PIK3CD/p110δ gain-of-function mutation. We propose a dynamic model wherein RCK family members, in conjunction with Dcp2, function in controlling ATG mRNA stability to govern autophagy, which in turn modulates vital cellular processes affecting inflammation and microbial pathogenesis. PMID:26098573

  14. Lithium chloride prevents interleukin‐1β induced cartilage degradation and loss of mechanical properties

    PubMed Central

    Yasmin, Habiba; Varone, Anna; Wiles, Anna; Poole, C. Anthony; Knight, Martin M.

    2015-01-01

    ABSTRACT Osteoarthritis is a chronic degenerative disease that affects the articular cartilage. Recent studies have demonstrated that lithium chloride exhibits significant efficacy as a chondroprotective agent, blocking cartilage degradation in response to inflammatory cytokines. However, conflicting literature suggests lithium may affect the physicochemical properties of articular cartilage and thus long‐term exposure may negatively affect the mechanical functionality of this tissue. This study aims to investigate the effect of lithium chloride on the biomechanical properties of healthy and interleukin‐1β treated cartilage in vitro and examines the consequences of long‐term exposure to lithium on cartilage health in vivo. Bovine cartilage explants were treated with lithium chloride for 12 days. Chondrocyte viability, matrix catabolism and the biomechanical properties of bovine cartilage explants were not significantly altered following treatment. Consistent with these findings, long term‐exposure (9 months) to dietary lithium did not induce osteoarthritis in rats, as determined by histological staining. Moreover, lithium chloride did not induce the expression of catabolic enzymes in human articular chondrocytes. In an inflammatory model of cartilage destruction, lithium chloride blocked interleukin‐1β signaling in the form of nitric oxide and prostaglandin E2 release and prevented matrix catabolism such that the loss of mechanical integrity observed with interleukin‐1β alone was inhibited. This study provides further support for lithium chloride as a novel compound for the treatment of osteoarthritis. © 2015 The Authors. Journal of Orthopaedic Research published by Wiley Periodicals, Inc. J Orthop Res 33:1552–1559, 2015. PMID:26174175

  15. Thermal Degradation, Mechanical Properties and Morphology of Wheat Straw Flour Filled Recycled Thermoplastic Composites

    PubMed Central

    Mengeloglu, Fatih; Karakus, Kadir

    2008-01-01

    Thermal behaviors of wheat straw flour (WF) filled thermoplastic composites were measured applying the thermogravimetric analysis and differential scanning calorimetry. Morphology and mechanical properties were also studied using scanning electron microscope and universal testing machine, respectively. Presence of WF in thermoplastic matrix reduced the degradation temperature of the composites. One for WF and one for thermoplastics, two main decomposition peaks were observed. Morphological study showed that addition of coupling agent improved the compatibility between WFs and thermoplastic. WFs were embedded into the thermoplastic matrix indicating improved adhesion. However, the bonding was not perfect because some debonding can also be seen on the interface of WFs and thermoplastic matrix. In the case of mechanical properties of WF filled recycled thermoplastic, HDPE and PP based composites provided similar tensile and flexural properties. The addition of coupling agents improved the properties of thermoplastic composites. MAPE coupling agents performed better in HDPE while MAPP coupling agents were superior in PP based composites. The composites produced with the combination of 50-percent mixture of recycled HDPE and PP performed similar with the use of both coupling agents. All produced composites provided flexural properties required by the ASTM standard for polyolefin-based plastic lumber decking boards.

  16. Rationalizing the mechanism of HMDS degradation in air and effective control of the reaction byproducts

    NASA Astrophysics Data System (ADS)

    Seguin, Kevin; Dallas, Andrew J.; Weineck, Gerald

    2008-03-01

    The concern over molecular contamination on the surfaces of optics continues to grow. Most recently, this concern has focused on siloxane contamination resulting from hexamethyldisilazane (HMDS) which is commonly used as a wafer treatment to improve photoresist adhesion onto wafers. From this process, HMDS vapor can be found within FABs and process tools where it has been linked to issues related to lens hazing. This type of surface contamination is significantly detrimental to the imaging process and is generally corrected by extensive surface cleaning or even lens replacement. Additionally, this type of repair also requires adjustment of the optical axis, thereby contributing to an extended downtime. HMDS is known to be very sensitive to the presence of water and is therefore believed to degrade in humid airstreams. This research focuses on rationalizing the reaction mechanisms of HMDS in dry and humid airstreams and in the presence of several adsorbent surfaces. It is shown that HMDS hydrolyzes in humid air to trimethylsilanol (TMS) and ammonia (NH 3). Furthermore, it is shown that TMS can dimerize in air, or on specific types of adsorption media, to form hexamethyldisiloxane (HMDSO). Additionally, we report on the relative impact of these reaction mechanisms on the removal of both HMDS and its hydrolysis products (TMS, HMDSO and NH 3).

  17. Dynamic mechanical analysis and esterase degradation of dentin adhesives containing a branched methacrylate

    PubMed Central

    Park, Jong-Gu; Ye, Qiang; Topp, Elizabeth M.; Lee, Chi H.; Kostoryz, Elisabet L.; Misra, Anil; Spencer, Paulette

    2010-01-01

    A study of the dynamic mechanical properties and the enzymatic degradation of new dentin adhesives containing a multifunctional methacrylate are described. Adhesives contained 2-hydroxyethyl methacrylate (HEMA), 2,2-bis[4-(2-hydroxy-3-methacryloxypropoxy) phenyl]-propane (BisGMA), and a new multifunctional methacrylate with a branched side chain-trimethylolpropane mono allyl ether dimethacrylate (TMPEDMA). Adhesives were photopolymerized in the presence of 0, 8 and 16 wt% water to simulate wet bonding conditions in the mouth and compared to control adhesives. The degree of conversion as a function of irradiation time was comparable for experimental and control adhesives. In dynamic mechanical analysis (DMA), broad tan δ peaks were obtained for all samples, indicating that the polymerized networks are heterogeneous; comparison of the full-width-at-half-maximum values obtained from the tan δ curves indicated increased heterogeneity for samples cured in the presence of water and/or containing TMPEDMA. The experimental adhesive showed higher Tg and higher rubbery modulus indicating increased crosslink density as compared to the control. The improvement in esterase resistance afforded by adhesives containing the TMPEDMA is greater when this material is photopolymerized in the presence of water, suggesting better performance in the moist environment of the mouth. The improved esterase resistance of the new adhesive could be explained in terms of the densely crosslinked network structure and/or the steric hindrance of branched alkyl side chains. PMID:19358261

  18. Age-Related Neural Oscillation Patterns During the Processing of Temporally Manipulated Speech.

    PubMed

    Rufener, Katharina S; Oechslin, Mathias S; Wöstmann, Malte; Dellwo, Volker; Meyer, Martin

    2016-05-01

    This EEG-study aims to investigate age-related differences in the neural oscillation patterns during the processing of temporally modulated speech. Viewing from a lifespan perspective, we recorded the electroencephalogram (EEG) data of three age samples: young adults, middle-aged adults and older adults. Stimuli consisted of temporally degraded sentences in Swedish-a language unfamiliar to all participants. We found age-related differences in phonetic pattern matching when participants were presented with envelope-degraded sentences, whereas no such age-effect was observed in the processing of fine-structure-degraded sentences. Irrespective of age, during speech processing the EEG data revealed a relationship between envelope information and the theta band (4-8 Hz) activity. Additionally, an association between fine-structure information and the gamma band (30-48 Hz) activity was found. No interaction, however, was found between acoustic manipulation of stimuli and age. Importantly, our main finding was paralleled by an overall enhanced power in older adults in high frequencies (gamma: 30-48 Hz). This occurred irrespective of condition. For the most part, this result is in line with the Asymmetric Sampling in Time framework (Poeppel in Speech Commun 41:245-255, 2003), which assumes an isomorphic correspondence between frequency modulations in neurophysiological patterns and acoustic oscillations in spoken language. We conclude that speech-specific neural networks show strong stability over adulthood, despite initial processes of cortical degeneration indicated by enhanced gamma power. The results of our study therefore confirm the concept that sensory and cognitive processes undergo multidirectional trajectories within the context of healthy aging. PMID:26613726

  19. Photocatalytic degradation and removal mechanism of ibuprofen via monoclinic BiVO4 under simulated solar light.

    PubMed

    Li, Fuhua; Kang, Yapu; Chen, Min; Liu, Guoguang; Lv, Wenying; Yao, Kun; Chen, Ping; Huang, Haoping

    2016-05-01

    Characterized as by X-ray diffraction, scanning electron microscopy and UV-vis diffuse reflectance spectra techniques, BiVO4 photocatalyst was hydrothermally synthesized. The photocatalytic degradation mechanisms of ibuprofen (IBP) were evaluated in aqueous media via BiVO4. Results demonstrated that the prepared photocatalyst corresponded to phase-pure monoclinic scheelite BiVO4. The synthesized BiVO4 showed superior photocatalytic properties under the irradiation of visible-light. The photocatalytic degradation rate of IBP decreased with an increase in the initial IBP concentration. The degradation process followed first-order kinetics model. At an IBP concentration of 10 mg L(-1), while a BiVO4 concentration of 5.0 g L(-1) with pH value of 4.5, the rate of IBP degradation was obtained as 90% after 25 min. The photocatalytic degradation of IBP was primarily accomplished via the generation of superoxide radical (O2(•-)) and hydroxyl radicals ((•)OH). During the process of degradation, part of the (•)OH was converted from the O2(•-). The direct oxidation of holes (h(+)) made a minimal contribution to the degradation of IBP. PMID:26901469

  20. Atmospheric degradation mechanisms of hydrogen containing chlorofluorocarbons (HCFC) and fluorocarbons (HFC)

    NASA Technical Reports Server (NTRS)

    Zellner, Reinhard

    1990-01-01

    The current knowledge of atmospheric degradation of hydrogen containing chlorofluorocarbons (HCFC 22 (CHClF2), HCFC 123 (CHCl2CF3), HCFC 124 (CHClFCF3), HCFC 141b (CFCl2CH3), HCFC 142b (CF2ClCH3)) and fluorocarbons (HFC 125 (CHF2CF3), HFC 134a (CH2FCF3), HFC 152a (CHF2CH3)) is assessed. Except for the initiation reaction by OH radicals, there are virtually no experimental data available concerning the subsequent oxidative breakdown of these molecules. However, from an analogy to the degradation mechanisms of simple alkanes, some useful guidelines as to the expected intermediates and final products can be derived. A noteable exception from this analogy, however, appears for the oxi-radicals. Here, halogen substitution induces new reaction types (C-Cl and C-C bond ruptures) which are unknown to the unsubstituted analogues and which modify the nature of the expected carbonyl products. Based on an evaluation of these processes using estimated bond strength data, the following simplified rules with regards to the chlorine content of the HCFC's may be deduced: (1) HCFC's containing one chlorine atom such as 22 and 142b seem to release their chlorine content essentially instantaneous with the initial attack on the parent by OH radicals, and for HCFC 124, such release is apparently prevented; (2) HCFC's such as 123 and 141b with two chlorine atoms are expected to release only one of these instantaneously; and the second chlorine atom may be stored in potentially long-lived carbonyl compounds such as CF3CClO or CClFO.

  1. The mechanism study of efficient degradation of hydrophobic nonylphenol in solution by a chemical-free technology of sonophotolysis.

    PubMed

    Xu, L J; Chu, W; Lee, Po-Heng; Wang, Jian

    2016-05-01

    Nonylphenol is a hydrophobic endocrine disrupting compound, which can inhibit the growth of sewage bacteria in biological processes. This study investigated the degradation of 4-n-nonylphenol (NP) in water by a chemical-free technology of sonophotolysis with emphasis on the impacts of several important parameters, including light intensity, solution pH, two commonly seen inorganic ions (i.e. NO3(-) and HCO3(-)), and principally on the examination of degradation mechanisms. It was found that, solution pH could significantly influence both NP degradation efficiency and the synergistic effect of sonophotolytic process, where higher synergistic effect was obtained at more acidic condition. In addition, the presence of NO3(-) accelerated NP degradation by both acting as a photosensitizer and providing NO2 radicals, while HCO3(-) had little effect on NP degradation. Identification of intermediates of NP degradation indicated that NP sonophotolysis was mainly initiated by the formation of hydroxy-NP, and a new intermediate di-hydroxy-NP was identified for the first time ever in this study. Through thermodynamic analysis, results indicated that both ortho- and meta-hydroxy-NP species can coexist in the solution but the ortho-4-NBZQ (4-nonyl-benzoquinone) is dominant. In addition, the mechanism of ortho-hydroxy-NP formation was suggested by the addition of HO and H radicals. PMID:26855185

  2. Parainflammation, chronic inflammation and age-related macular degeneration

    PubMed Central

    Chen, Mei; Xu, Heping

    2016-01-01

    Inflammation is an adaptive response of the immune system to noxious insults to maintain homeostasis and restore functionality. The retina is considered an immune privileged tissue due to its unique anatomical and physiological properties. During aging, the retina suffers from a low-grade chronic oxidative insult, which sustains for decades and increases in level with advancing age. As a result, the retinal innate immune system, particularly microglia and the complement system, undergo low levels of activation (para-inflammation). In many cases, this para-inflammatory response can maintain homeostasis in the healthy aging eye. However, in patients with age-related macular degeneration (AMD), this para-inflammatory response becomes dysregulated and contributes to macular damage. Factors contributing to the dysregulation of age-related retinal para-inflammation include genetic predisposition, environmental risk factors and old age. Dysregulated para-inflammation (chronic inflammation) in AMD damages the blood retina barrier (BRB), resulting in the breach of retinal immune privilege leading to the development of retinal lesions. This review discusses the basic principles of retinal innate immune responses to endogenous chronic insults in normal aging and in AMD, and explores the difference between beneficial para-inflammation and the detrimental chronic inflammation in the context of AMD. PMID:26292978

  3. Oxidative stress and age-related neuronal deficits.

    PubMed

    Joseph, J A; Denisova, N; Villalobos-Molina, R; Erat, S; Strain, J

    1996-01-01

    Research from our laboratory has indicated that the loss of sensitivity that occurs in several receptor systems as a function of age may be an index of an increasing inability to respond to oxidative stress (OS). This loss occurs partially as a result of altered signal transduction (ST). Assessments have involved determining the nature of age-related reductions in oxotremorine enhancement of K(+)-evoked dopamine release (K(+)-ERDA) from superfused striatal slices. Using this model, we have found that 1. Reductions can be restored with in vivo administration of the free-radical trapping agent, N-tert-butyl-alpha-phenylnitrone (PBN); 2. Decrements in DA release induced by NO or H2O2 from striatal slices from both young and old animals could be restored with alpha-tocopherol or PBN; 3. ST decrements, such as those seen in aging, could be induced with radiation exposure; and 4. Pre-incubation of the striatal slices with cholesterol decreased subsequent deleterious effects of NO or OH. on DA release. Thus, cholesterol, which increases in neuronal membranes as a function of age, may function as a potent antioxidant and protectant against neuronal damage. These results suggest that therapeutic efforts to restore cognitive deficits in aging and age-related disease might begin with antioxidant reversal of ST decrements. PMID:8871939

  4. Fertility preservation for age-related fertility decline.

    PubMed

    Stoop, Dominic; Cobo, Ana; Silber, Sherman

    2014-10-01

    Cryopreservation of eggs or ovarian tissue to preserve fertility for patients with cancer has been studied since 1994 with R G Gosden's paper describing restoration of fertility in oophorectomised sheep, and for decades previously by others in smaller mammals. Clinically this approach has shown great success. Many healthy children have been born from eggs cryopreserved with the Kuwayama egg vitrification technique for non-medical (social) indications, but until now very few patients with cancer have achieved pregnancy with cryopreserved eggs. Often, oncologists do not wish to delay cancer treatment while the patient goes through multiple ovarian stimulation cycles to retrieve eggs, and the patient can only start using the oocytes after full recovery from cancer. Ovarian stimulation and egg retrieval is not a barrier for patients without cancer who wish to delay childbearing, which makes oocyte cryopreservation increasingly popular to overcome an age-related decline in fertility. Cryopreservation of ovarian tissue is an option if egg cryopreservation is ruled out. More than 35 babies have been born so far with cryopreserved ovarian tissue in patients with cancer who have had a complete return of hormonal function, and fertility to baseline. Both egg and ovarian tissue cryopreservation might be ready for application to the preservation of fertility not only in patients with cancer but also in countering the increasing incidence of age-related decline in female fertility. PMID:25283572

  5. Age-related mutations and chronic myelomonocytic leukemia.

    PubMed

    Mason, C C; Khorashad, J S; Tantravahi, S K; Kelley, T W; Zabriskie, M S; Yan, D; Pomicter, A D; Reynolds, K R; Eiring, A M; Kronenberg, Z; Sherman, R L; Tyner, J W; Dalley, B K; Dao, K-H; Yandell, M; Druker, B J; Gotlib, J; O'Hare, T; Deininger, M W

    2016-04-01

    Chronic myelomonocytic leukemia (CMML) is a hematologic malignancy nearly confined to the elderly. Previous studies to determine incidence and prognostic significance of somatic mutations in CMML have relied on candidate gene sequencing, although an unbiased mutational search has not been conducted. As many of the genes commonly mutated in CMML were recently associated with age-related clonal hematopoiesis (ARCH) and aged hematopoiesis is characterized by a myelomonocytic differentiation bias, we hypothesized that CMML and aged hematopoiesis may be closely related. We initially established the somatic mutation landscape of CMML by whole exome sequencing followed by gene-targeted validation. Genes mutated in ⩾10% of patients were SRSF2, TET2, ASXL1, RUNX1, SETBP1, KRAS, EZH2, CBL and NRAS, as well as the novel CMML genes FAT4, ARIH1, DNAH2 and CSMD1. Most CMML patients (71%) had mutations in ⩾2 ARCH genes and 52% had ⩾7 mutations overall. Higher mutation burden was associated with shorter survival. Age-adjusted population incidence and reported ARCH mutation rates are consistent with a model in which clinical CMML ensues when a sufficient number of stochastically acquired age-related mutations has accumulated, suggesting that CMML represents the leukemic conversion of the myelomonocytic-lineage-biased aged hematopoietic system. PMID:26648538

  6. Age-related differences in electroencephalogram connectivity and network topology.

    PubMed

    Knyazev, Gennady G; Volf, Nina V; Belousova, Ludmila V

    2015-05-01

    To better understand age-related differences in brain function and behavior, connectivity between brain regions was estimated from electroencephalogram source time series in eyes closed versus eyes open resting condition. In beta band, decrease of connectivity upon eyes opening was more pronounced in younger than in older participants. The extent of this decrease was associated with reaction time in attention tasks, and this relationship was fully mediated by participants' age, implying that physiological processes, which lead to age-related slowing, include changes in beta reactivity. Graph-theoretical analysis showed a decrease of modularity and clustering in beta and gamma band networks in older adults, implying that age makes brain networks more random. The overall number of nodes identified as hubs in posterior cortical regions decreased in older participants. At the same time, increase of connectedness of anterior nodes, probably reflecting compensatory activation of the anterior attentional system, was observed in beta-band network of older adults. These findings show that normal aging mostly affects interactions in beta band, which are probably involved in attentional processes. PMID:25766772

  7. Age-related changes to the production of linguistic prosody

    NASA Astrophysics Data System (ADS)

    Barnes, Daniel R.

    The production of speech prosody (the rhythm, pausing, and intonation associated with natural speech) is critical to effective communication. The current study investigated the impact of age-related changes to physiology and cognition in relation to the production of two types of linguistic prosody: lexical stress and the disambiguation of syntactically ambiguous utterances. Analyses of the acoustic correlates of stress: speech intensity (or sound-pressure level; SPL), fundamental frequency (F0), key word/phrase duration, and pause duration revealed that both young and older adults effectively use these acoustic features to signal linguistic prosody, although the relative weighting of cues differed by group. Differences in F0 were attributed to age-related physiological changes in the laryngeal subsystem, while group differences in duration measures were attributed to relative task complexity and the cognitive-linguistic load of these respective tasks. The current study provides normative acoustic data for older adults which informs interpretation of clinical findings as well as research pertaining to dysprosody as the result of disease processes.

  8. Age-related preferences and age weighting health benefits.

    PubMed

    Tsuchiya, A

    1999-01-01

    This paper deals with the relevance of age in the paradigm of quality adjusted life years (QALYs). The first section outlines two rationales for incorporating age weights into QALYs. One of them is based on efficiency concerns; and the other on equity concerns. Both of these are theoretical constructs. The main purpose of this paper is to examine the extent of published empirical support for such age weighting. The second section is a brief survey of nine empirical studies that elicited age-related preferences from the general public. Six of these quantified the strength of the preferences, and these are discussed in more detail in the third section. The analysis distinguishes three kinds of age-related preference: productivity ageism, utilitarian ageism and egalitarian ageism. The relationship between them and their relevance to the two different rationales for age weighting are then explored. It is concluded that, although there is strong prima facie evidence of public support for both types of age weighting, the empirical evidence to support any particular set of weights is at present weak. PMID:10048783

  9. Age-related differences in moral identity across adulthood.

    PubMed

    Krettenauer, Tobias; Murua, Lourdes Andrea; Jia, Fanli

    2016-06-01

    In this study, age-related differences in adults' moral identity were investigated. Moral identity was conceptualized a context-dependent self-structure that becomes differentiated and (re)integrated in the course of development and that involves a broad range of value-orientations. Based on a cross-sectional sample of 252 participants aged 14 to 65 years (148 women, M = 33.5 years, SD = 16.9) and a modification of the Good Self-Assessment, it was demonstrated that mean-level of moral identity (averaged across the contexts of family, school/work, and community) significantly increased in the adult years, whereas cross-context differentiation showed a nonlinear trend peaking at the age of 25 years. Value-orientations that define individuals' moral identity shifted so that self-direction and rule-conformity became more important with age. Age-related differences in moral identity were associated with, but not fully attributable to changes in personality traits. Overall, findings suggest that moral identity development is a lifelong process that starts in adolescence but expands well into middle age. (PsycINFO Database Record PMID:27124654

  10. Solar photocatalytic degradation of chlorophenols mixture (4-CP and 2,4-DCP): Mechanism and kinetic modelling.

    PubMed

    Abeish, Abdulbasit M; Ang, Ha Ming; Znad, Hussein

    2015-01-01

    The solar-photocatalytic degradation mechanisms and kinetics of 4-chlorophenol (4-CP) and 2,4-dichlorophenol (2,4-DCP) using TiO2 have been investigated both individually and combined. The individual solar-photocatalytic degradation of both phenolic compounds showed that the reaction rates follow pseudo-first-order reaction. During the individual photocatalytic degradation of both 4-CP and 2,4-DCP under the same condition of TiO2 (0.5 g L(-1)) and light intensities (1000 mW cm(-2)) different intermediates were detected, three compounds associated with 4-CP (hydroquinone (HQ), phenol (Ph) and 4-chlorocatechol (4-cCat)) and two compounds associated with 2,4-DCP (4-CP and Ph). The photocatalytic degradation of the combined mixture (4-CP and 2,4-DCP) was also investigated at the same conditions and different 2,4-DCP initial concentrations. The results showed that the degradation rate of 4-CP decreases when the 2,4-DCP concentration increases. Furthermore, the intermediates detected were similar to that found in the individual degradation but with high Ph concentration. Therefore, a possible reaction mechanism for degradation of this combined mixture was proposed. Moreover, a modified Langmuir-Hinshelwood (L-H) kinetic model considering all detected intermediates was developed. A good agreement between experimental and estimated results was achieved. This model can be useful for scaling-up purposes more accurately as its considering the intermediates formed, which has a significant effect on degrading the main pollutants (4-CP and 2,4-DCP). PMID:25560258

  11. Age-related declines in immune response in a wild mammal are unrelated to immune cell telomere length.

    PubMed

    Beirne, Christopher; Waring, Laura; McDonald, Robbie A; Delahay, Richard; Young, Andrew

    2016-02-24

    Senescence has been hypothesized to arise in part from age-related declines in immune performance, but the patterns and drivers of within-individual age-related changes in immunity remain virtually unexplored in natural populations. Here, using a long-term epidemiological study of wild European badgers (Meles meles), we (i) present evidence of a within-individual age-related decline in the response of a key immune-signalling cytokine, interferon-gamma (IFNγ), to ex vivo lymphocyte stimulation, and (ii) investigate three putative drivers of individual variation in the rate of this decline (sex, disease and immune cell telomere length; ICTL). That the within-individual rate of age-related decline markedly exceeded that at the population level suggests that individuals with weaker IFNγ responses are selectively lost from this population. IFNγ responses appeared to decrease with the progression of bovine tuberculosis infection (independent of age) and were weaker among males than females. However, neither sex nor disease influenced the rate of age-related decline in IFNγ response. Similarly, while ICTL also declines with age, variation in ICTL predicted neither among- nor within-individual variation in IFNγ response. Our findings provide evidence of within-individual age-related declines in immune performance in a wild mammal and highlight the likely complexity of the mechanisms that generate them. PMID:26888036

  12. Age-related declines in immune response in a wild mammal are unrelated to immune cell telomere length

    PubMed Central

    Waring, Laura; McDonald, Robbie A.; Delahay, Richard; Young, Andrew

    2016-01-01

    Senescence has been hypothesized to arise in part from age-related declines in immune performance, but the patterns and drivers of within-individual age-related changes in immunity remain virtually unexplored in natural populations. Here, using a long-term epidemiological study of wild European badgers (Meles meles), we (i) present evidence of a within-individual age-related decline in the response of a key immune-signalling cytokine, interferon-gamma (IFNγ), to ex vivo lymphocyte stimulation, and (ii) investigate three putative drivers of individual variation in the rate of this decline (sex, disease and immune cell telomere length; ICTL). That the within-individual rate of age-related decline markedly exceeded that at the population level suggests that individuals with weaker IFNγ responses are selectively lost from this population. IFNγ responses appeared to decrease with the progression of bovine tuberculosis infection (independent of age) and were weaker among males than females. However, neither sex nor disease influenced the rate of age-related decline in IFNγ response. Similarly, while ICTL also declines with age, variation in ICTL predicted neither among- nor within-individual variation in IFNγ response. Our findings provide evidence of within-individual age-related declines in immune performance in a wild mammal and highlight the likely complexity of the mechanisms that generate them. PMID:26888036

  13. Diagnostic examination of Generation 2 lithium-ion cells and assessment ofperformance degradation mechanisms.

    SciTech Connect

    Abraham, D. P.; Dees, D. W.; Knuth, J.; Reynolds, E.; Gerald, R.; Hyung,Y.-E.; Belharouak, I.; Stoll, M.; Sammann, E.; MacLaren, S.; Haasch, R.; Twesten,R.; Sardela, M.; Battaglia, V.; Cairns, E.; Kerr, J.; Kerlau, M.; Kostecki, R.; Lei,J.; McCarthy, K.; McLarnon, F.; Reimer, J.; Richardson, T.; Ross, P.; Sloop,S.; Song, X.; Zhuang, V.; Balasubramanian, M.; McBreen, J.; Chung, K.-Y.; Yang, X.Q.; Yoon, W.-S.; Norin, L.

    2005-07-15

    The Advanced Technology Development (ATD) Program is a multilaboratory effort to assist industrial developers of high-power lithium-ion batteries overcome the barriers of cost, calendar life, abuse tolerance, and low-temperature performance so that this technology may be rendered practical for use in hybrid electric vehicles (HEVs). Included in the ATD Program is a comprehensive diagnostics effort conducted by researchers at Argonne National Laboratory (ANL), Brookhaven National Laboratory (BNL), and Lawrence Berkeley National Laboratory (LBNL). The goals of this effort are to identify and characterize processes that limit lithium-ion battery performance and calendar life, and ultimately to describe the specific mechanisms that cause performance degradation. This report is a compilation of the diagnostics effort conducted since spring 2001 to characterize Generation 2 ATD cells and cell components. The report is divided into a main body and appendices. Information on the diagnostic approach, details from individual diagnostic techniques, and details on the phenomenological model used to link the diagnostic data to the loss of 18650-cell electrochemical performance are included in the appendices. The main body of the report includes an overview of the 18650-cell test data, summarizes diagnostic data and modeling information contained in the appendices, and provides an assessment of the various mechanisms that have been postulated to explain performance degradation of the 18650 cells during accelerated aging. This report is intended to serve as a ready reference on ATD Generation 2 18650-cell performance and provide information on the tools for diagnostic examination and relevance of the acquired data. A comprehensive account of our experimental procedures and resulting data may be obtained by consulting the various references listed in the text. We hope that this report will serve as a roadmap for the diagnostic analyses of other lithium-ion technologies being

  14. Mechanical degradation under hydrogen of yttrium doped barium zirconate electrolyte material prepared with NiO additive

    NASA Astrophysics Data System (ADS)

    Ciria, D.; Ben Hassine, M.; Jiménez-Melendo, M.; Iakovleva, A.; Haghi-Ashtiani, P.; Aubin, V.; Dezanneau, G.

    2016-07-01

    Recently, a novel process was presented to fabricate dense yttrium-doped barium zirconate electrolytes with high proton conductivity. This process was based on the use of a NiO additive during reactive sintering. We show here that materials made from this process present a fast degradation of mechanical properties when put in hydrogen-rich conditions, while material made from conventional sintering without NiO aid remains intact in the same conditions. The fast degradation of samples made from reactive sintering, leading to sample failure under highly compressive conditions, is due to the reduction of NiO nanoparticles at grain boundaries as shown from structural and chemical analyses using Transmission Electron Microscopy. By the present study, we alert about the potential risk of cell failure due to this mechanical degradation.

  15. Inflammatory networks in ageing, age-related diseases and longevity.

    PubMed

    Vasto, Sonya; Candore, Giuseppina; Balistreri, Carmela Rita; Caruso, Marco; Colonna-Romano, Giuseppina; Grimaldi, Maria Paola; Listi, Florinda; Nuzzo, Domenico; Lio, Domenico; Caruso, Calogero

    2007-01-01

    Inflammation is considered a response set by the tissues in response to injury elicited by trauma or infection. It is a complex network of molecular and cellular interactions that facilitates a return to physiological homeostasis and tissue repair. The individual response against infection and trauma is also determined by gene variability. Ageing is accompanied by chronic low-grade inflammation state clearly showed by 2-4-fold increase in serum levels of inflammatory mediators. A wide range of factors has been claimed to contribute to this state; however, the most important role seems to be played by the chronic antigenic stress, which affects immune system thorough out life with a progressive activation of macrophages and related cells. This pro-inflammatory status, interacting with the genetic background, potentially triggers the onset of age-related inflammatory diseases as atherosclerosis. Thus, the analysis of polymorphisms of the genes that are key nodes of the natural immunity response might clarify the patho-physiology of age-related inflammatory diseases as atherosclerosis. On the other hand, centenarians are characterized by marked delay or escape from age-associated diseases that, on average, cause mortality at earlier ages. In addition, centenarian offspring have increased likelihood of surviving to 100 years and show a reduced prevalence of age-associated diseases, as cardiovascular disease (CVD) and less prevalence of cardiovascular risk factors. So, genes involved in CVD may play an opposite role in human longevity. Thus, the model of centenarians can be used to understand the role of these genes in successful and unsuccessful ageing. Accordingly, we report the results of several studies in which the frequencies of pro-inflammatory alleles were significantly higher in patients affected by infarction and lower in centenarians whereas age-related controls displayed intermediate values. These findings point to a strong relationship between the genetics

  16. Age-related changes in intrinsic function of the superior temporal sulcus in autism spectrum disorders.

    PubMed

    Alaerts, Kaat; Nayar, Kritika; Kelly, Clare; Raithel, Jessica; Milham, Michael P; Di Martino, Adriana

    2015-10-01

    Currently, the developmental trajectories of neural circuits implicated in autism spectrum disorders (ASD) are largely unknown. Here, we specifically focused on age-related changes in the functional circuitry of the posterior superior temporal sulcus (pSTS), a key hub underlying social-cognitive processes known to be impaired in ASD. Using a cross-sectional approach, we analysed resting-state functional magnetic resonance imaging (fMRI) data collected from children, adolescents and adults available through the autism brain imaging data exchange repository [n = 106 with ASD and n = 109 typical controls (TC), ages 7-30 years]. The observed age-related changes of pSTS intrinsic functional connectivity (iFC) suggest that no single developmental pattern characterizes ASD. Instead, pSTS circuitry displayed a complex developmental picture, with some functional circuits showing patterns consistent with atypical development in ASD relative to TC (pSTS-iFC with fusiform gyrus and angular gyrus) and others showing delayed maturation (pSTS-iFC with regions of the action perception network). Distinct developmental trajectories in different functional circuits in ASD likely reflect differential age-related changes in the socio-cognitive processes they underlie. Increasing insight on these mechanisms is a critical step in the development of age-specific interventions in ASD. PMID:25809403

  17. Age-related decline of precision and binding in visual working memory.

    PubMed

    Peich, Muy-Cheng; Husain, Masud; Bays, Paul M

    2013-09-01

    Working memory declines with normal aging, but the nature of this impairment is debated. Studies based on detecting changes to arrays of visual objects have identified two possible components to age-related decline: a reduction in the number of items that can be stored, or a deficit in maintaining the associations (bindings) between individual object features. However, some investigations have reported intact binding with aging, and specific deficits arising only in Alzheimer's disease. Here, using a recently developed continuous measure of recall fidelity, we tested the precision with which adults of different ages could reproduce from memory the orientation and color of a probed array item. The results reveal a further component of cognitive decline: an age-related decrease in the resolution with which visual information can be maintained in working memory. This increase in recall variability with age was strongest under conditions of greater memory load. Moreover, analysis of the distribution of errors revealed that older participants were more likely to incorrectly report one of the unprobed items in memory, consistent with an age-related increase in misbinding. These results indicate a systematic decline with age in working memory resources that can be recruited to store visual information. The paradigm presented here provides a sensitive index of both memory resolution and feature binding, with the potential for assessing their modulation by interventions. The findings have implications for understanding the mechanisms underpinning working memory deficits in both health and disease. PMID:23978008

  18. Progressive Age-Related Changes Similar to Age-Related Macular Degeneration in a Transgenic Mouse Model

    PubMed Central

    Rakoczy, Piroska Elizabeth; Zhang, Dan; Robertson, Terry; Barnett, Nigel L.; Papadimitriou, John; Constable, Ian Jeffrey; Lai, Chooi-May

    2002-01-01

    Age-related macular degeneration (AMD) is the major cause of blindness in the developed world. Its pathomechanism is unknown and its late onset, complex genetics and strong environmental components have all hampered investigations. Here we demonstrate the development of an animal model for AMD that reproduces features associated with geographic atrophy; a transgenic mouse line (mcd/mcd) expressing a mutated form of cathepsin D that is enzymatically inactive thus impairing processing of phagocytosed photoreceptor outer segments in the retinal pigment epithelial (RPE) cells. Pigmentary changes indicating RPE cell atrophy and a decreased response to flash electroretinograms were observed in 11- to 12-month-old mcd/mcd mice. Histological studies showed RPE cell proliferation, photoreceptor degeneration, shortening of photoreceptor outer segments, and accumulation of immunoreactive photoreceptor breakdown products in the RPE cells. An accelerated photoreceptor cell death was detected in 12-month-old mcd/mcd mice. Transmission electron microscopy demonstrated presence of basal laminar and linear deposits that are considered to be the hallmarks of AMD. Small hard drusen associated with human age-related maculopathy were absent in the mcd/mcd mouse model at the ages analyzed. In summary, this model presents several features of AMD, thus providing a valuable tool for investigating the underlying biological processes and pathomechanism of AMD. PMID:12368224

  19. Degradation Mechanism of Cyanobacterial Toxin Cylindrospermopsin by Hydroxyl Radicals in Homogeneous UV/H2O2 Process

    EPA Science Inventory

    The degradation of cylindrospermopsin (CYN), a widely distributed and highly toxic cyanobacterial toxin (cyanotoxin), remains poorly elucidated. In this study, the mechanism of CYN destruction by UV-254 nm/H2O2 advanced oxidation process (AOP) was investigated by mass spectrometr...

  20. Degradation mechanism of alkyl carbonate solvents used in lithium-ion cells during initial charging

    NASA Astrophysics Data System (ADS)

    Yoshida, H.; Fukunaga, T.; Hazama, T.; Terasaki, M.; Mizutani, M.; Yamachi, M.

    The degradation mechanism of electrolytes in the lithium-ion cell with LiCoO 2 and graphite electrodes was investigated by analyzing: (i) the composition of generated gases; (ii) thin films formed on the electrode, and (iii) the compositional change of the electrolyte during the initial charging. The solvents in this work were ethylene carbonate (EC), dimethyl carbonate (DMC), ethylmethyl carbonate (EMC) and diethyl carbonate (DEC). LiPF 6 was used as a salt. In the one- to three-component systems containing EC, carbon monoxide and ethane were detected, whereas Li 2CO 3, RCOOLi and (CH 2OLi) 2 were the main components of the surface film on the negative electrode. From these results, it can be assumed that the decomposition of the systems was mainly due to the reductive reaction of EC at the initial charging. Through the additional analysis of the electrolyte composition, it was confirmed that the dialkyl-2,5-dioxahexane carboxylate was produced in the electrolyte after initial charging. This suggests the occurrence of trans-esterification.

  1. Sonochemical degradation of diclofenac: byproduct assessment, reaction mechanisms and environmental considerations.

    PubMed

    Ziylan, Asu; Dogan, Sifa; Agopcan, Sesil; Kidak, Rana; Aviyente, Viktorya; Ince, Nilsun H

    2014-05-01

    The study covers a thorough assessment of the overall degradation of diclofenac-Na (DCF) by high-frequency ultrasound, focusing particularly on identification, interpretation, and characterization of the oxidation byproducts and their reaction mechanisms. It was found that sonication of 5 mg L(-1) DCF at near neutral pH rendered complete conversion of the compound, 45 % carbon, 30 % chlorine, and 25 % nitrogen mineralization. Density functional theory (DFT) calculations confirmed the experimentally detected major byproduct 2,6-dichloroaniline, the formation of which was explained by OH• addition to the ipso-position of the amino group. The stability of UV absorption at around 276-280 nm throughout reaction was in agreement with the detected byproduct structures, i.e., the presence of amino/amine groups and phenolic, aniline, benzene, and quinine-type derivatives, which all absorbed at around the same band. Microtox toxicity of the reactor aliquots at early reaction showed that initially the reaction products, specifically 1-(2,6-dichlorophenyl)-2-indoline-one, were very toxic; subsequently toxicity exhibited a fluctuating pattern, and a steady declination towards the "non-toxic" level was observed only after 90 min. Oxygen uptake analysis also revealed the formation of harmful products at early reaction, but the reactor was totally biodegradable upon 1-h sonication. PMID:24453014

  2. Primary study on the contact degradation mechanism of CdZnTe detectors

    NASA Astrophysics Data System (ADS)

    Sang, Wenbin; Wei, Jin; Qi, Zhang; Wanwan, Li; Jiahua, Min; Jianyong, Teng; Yongbiao, Qian

    2004-07-01

    The metal-CdZnTe (CZT) interface plays a vital role in determining the contact characteristics, which is often the dominant factor influencing detector performance. The effects of the degradation of the interfacial layer between the metal contact layer and CZT surface on the mechanical and electrical properties have been investigated in this paper. The interfacial thermal stresses were simulated using 3-D finite element method (FEM). The results indicate that the maximum thermal stress is concentrated on the midst of the electrode and the magnitude of the stress produced by the different electrode materials in order is Al>Au>Pt>In. The adhesion forces between the metal contact layer and CZT surface were measured by using a Dage PC2400 Micro tester with the shear-off-method. The inter-diffusion between the metal contact layer and CZT was identified using the Anger depth profiles. The experimental results indicate that the electroless Au electrode on p-type high resistivity CZT is of smaller interfacial adhesion strength, but of better ohmicity than the sputtered Au. In addition, the aging effects on the contact characteristics of the detector were also examined.

  3. Mechanism of chlorite degradation to chloride and dioxygen by the enzyme chlorite dismutase.

    PubMed

    Schaffner, Irene; Hofbauer, Stefan; Krutzler, Michael; Pirker, Katharina F; Furtmüller, Paul G; Obinger, Christian

    2015-05-15

    Heme b containing chlorite dismutase (Cld) catalyses the conversion of chlorite to chloride and dioxygen which includes an unusual OO bond formation. This review summarizes our knowledge about the interaction of chlorite with heme enzymes and introduces the biological role, phylogeny and structure of functional chlorite dismutases with differences in overall structure and subunit architecture. The paper sums up the available experimental and computational studies on chlorite degradation by water soluble porphyrin complexes as well as a model based on the active site of Cld. Finally, it reports the available biochemical and biophysical data of Clds from different organisms which allow the presentation of a general reaction mechanism. It includes binding of chlorite to ferric Cld followed by subsequent heterolytic OCl bond cleavage leading to the formation of Compound I and hypochlorite, which finally recombine for production of chloride and O2. The role of the Cld-typical distal arginine in catalysis is discussed together with the pH dependence of the reaction and the role of transiently produced hypochlorite in irreversible inactivation of the enzyme. PMID:25748001

  4. Influence of the intramedullary nail preparation method on nail's mechanical properties and degradation rate.

    PubMed

    Morawska-Chochół, Anna; Chłopek, Jan; Szaraniec, Barbara; Domalik-Pyzik, Patrycja; Balacha, Ewa; Boguń, Maciej; Kucharski, Rafael

    2015-06-01

    When it comes to the treatment of long bone fractures, scientists are still investigating new materials for intramedullary nails and different manufacturing methods. Some of the most promising materials used in the field are resorbable polymers and their composites, especially since there is a wide range of potential manufacturing and processing methods. The aim of this work was to select the best manufacturing method and technological parameters to obtain multiphase, and multifunctional, biodegradable intramedullary nails. All composites were based on a poly(l-lactide) matrix. Either magnesium alloy wires or carbon and alginate fibres were introduced in order to reinforce the nails. The polylactide matrix was also modified with tricalcium phosphate and gentamicin sulfate. The composite nails were manufactured using three different methods: forming from solution, injection moulding and hot pressing. The effect of each method of manufacturing on mechanical properties and degradation rate of the nails was evaluated. The study showed that injection moulding provides higher uniformity and homogeneity of the particle-modified polylactide matrix, whereas hot pressing favours applying higher volume fractions of fibres and their better impregnation with the polymer matrix. Thus, it was concluded that the fabrication method should be individually selected dependently on the nail's desired phase composition. PMID:25842113

  5. Calcium-Magnesium-Aluminosilicate (CMAS) Reactions and Degradation Mechanisms of Advanced Environmental Barrier Coatings

    NASA Technical Reports Server (NTRS)

    Ahlborg, Nadia L.; Zhu, Dongming

    2013-01-01

    The thermochemical reactions between calcium-magnesium-aluminosilicate- (CMAS-) based road sand and several advanced turbine engine environmental barrier coating (EBC) materials were studied. The phase stability, reaction kinetics and degradation mechanisms of rare earth (RE)-silicates Yb2SiO5, Y2Si2O7, and RE-oxide doped HfO2 and ZrO2 under the CMAS infiltration condition at 1500 C were investigated, and the microstructure and phase characteristics of CMAS-EBC specimens were examined using Scanning Electron Microscopy (SEM) and X-ray Diffraction (XRD). Experimental results showed that the CMAS dissolved RE-silicates to form crystalline, highly non-stoichiometric apatite phases, and in particular attacking the silicate grain boundaries. Cross-section images show that the CMAS reacted with specimens and deeply penetrated into the EBC grain boundaries and formed extensive low-melting eutectic phases, causing grain boundary recession with increasing testing time in the silicate materials. The preliminary results also showed that CMAS reactions also formed low melting grain boundary phases in the higher concentration RE-oxide doped HfO2 systems. The effect of the test temperature on CMAS reactions of the EBC materials will also be discussed. The faster diffusion exhibited by apatite and RE-doped oxide phases and the formation of extensive grain boundary low-melting phases may limit the CMAS resistance of some of the environmental barrier coatings at high temperatures.

  6. Degradation mechanism of monosaccharides and xylan under pyrolytic conditions with theoretic modeling on the energy profiles.

    PubMed

    Wang, Shurong; Ru, Bin; Lin, Haizhou; Luo, Zhongyang

    2013-09-01

    Xylan and three monosaccharides (mannose, galactose, and arabinose) were selected as model compounds to investigate the mechanism of hemicellulose pyrolysis. The evolution of several typical pyrolysis products were observed by thermogravimetric analysis coupled to Fourier transform infrared spectroscopy. Monosaccharides underwent similar pyrolysis routes involving ring opening and secondary decomposition. Breakage of the O-acetyl groups and 4-O-methylglucuronic acid units in xylan branches resulted in its different pyrolysis behavior for the formation of acetic acid, CO2, and CO. The detailed reaction pathways of the monosaccharides were studied using density functional theory calculations. Furfural formation was more favorable than the formation of 1-hydroxy-2-propanone and 4-hydroxydihydrofuran-2(3H)-one during xylose degradation. However, in the pyrolysis of mannose and galactose, formation of 5-hydroxymethyl-2-furaldehyde was preferred because of the high energy barrier of the dissociation of the hydroxymethyl group. Meanwhile, the breakage of O-acetyl groups leading to acetic acid formation easily occurred because of its lower energy barrier. PMID:23819973

  7. Age-related changes of mitochondrial transcription factor a expression in rotator cuff degeneration

    PubMed Central

    Ichiseki, Toru; Ueda, Shusuke; Ueda, Yoshimichi; Kaneuji, Ayumi; Kawahara, Norio; Matsumoto, Tadami

    2015-01-01

    One cause of rotator cuff tears is thought to be age-related degenerative changes occurring in the rotator cuff. Using Rat rotator cuff we determined age-related changes in mitochondrial transcription factor A (TFAM) expression in rotator cuff degeneration to clarify the presence/absence of mitochondrial stress. The materials used were rotator cuffs (supraspinatus) of 5-, 24-, 48-, and 100-week-old Wistar Rats (five animals each). Histopathological study revealed a 4-layer structure consisting of a bone layer, calcified cartilage layer, non-calcified cartilage layer, and tendinous component), with age-related narrowing of the non-calcified cartilage layer confirmed to be present. In an immunohistochemical TFAM study positive findings of the non-calcified cartilage layer were less prominent in the 100-week-old group. In an Enzyme-Linked Immunosorbent Assay (ELISA) study, these were more prominent in the 5-week-old to 24-week-old groups, and slightly less so in the 48-week-old group as compared to the 24-week-old one. In the 100-week-old group as compared to the 24-week-old one they were significantly less prominent (p<0.05). The non-calcified cartilage layer is a major site for the dispersion of mechanical energy, and the change in TFAM expression noted at the same site in the present study and the results of ELISA suggest that age-related changes in mitochondrial stress may be one cause of rotator cuff degeneration. PMID:26692954

  8. Effects of chronic estrogen treatment on modulating age-related bone loss in female mice.

    PubMed

    Syed, Farhan A; Mödder, Ulrike Il; Roforth, Matthew; Hensen, Ira; Fraser, Daniel G; Peterson, James M; Oursler, Merry Jo; Khosla, Sundeep

    2010-11-01

    While female mice do not have the equivalent of a menopause, they do undergo reproductive senescence. Thus, to dissociate the effects of aging versus estrogen deficiency on age-related bone loss, we sham-operated, ovariectomized, or ovariectomized and estrogen-replaced female C57/BL6 mice at 6 months of age and followed them to age 18 to 22 months. Lumbar spines and femurs were excised for analysis, and bone marrow hematopoietic lineage negative (lin-) cells (enriched for osteoprogenitor cells) were isolated for gene expression studies. Six-month-old intact control mice were euthanized to define baseline parameters. Compared with young mice, aged/sham-operated mice had a 42% reduction in lumbar spine bone volume/total volume (BV/TV), and maintaining constant estrogen levels over life in ovariectomized/estrogen-treated mice did not prevent age-related trabecular bone loss at this site. By contrast, lifelong estrogen treatment of ovariectomized mice completely prevented the age-related reduction in cortical volumetric bone mineral density (vBMD) and thickness at the tibial diaphysis present in the aged/sham-operated mice. As compared with cells from young mice, lin- cells from aged/sham-operated mice expressed significantly higher mRNA levels for osteoblast differentiation and proliferation marker genes. These data thus demonstrate that, in mice, age-related loss of cortical bone in the appendicular skeleton, but not loss of trabecular bone in the spine, can be prevented by maintaining constant estrogen levels over life. The observed increase in osteoblastic differentiation and proliferation marker gene expression in progenitor bone marrow cells from aged versus young mice may represent a compensatory mechanism in response to ongoing bone loss. PMID:20499336

  9. Molecular mechanism of lysosomal sialidase deficiency in galactosialidosis involves its rapid degradation.

    PubMed Central

    Vinogradova, M V; Michaud, L; Mezentsev, A V; Lukong, K E; El-Alfy, M; Morales, C R; Potier, M; Pshezhetsky, A V

    1998-01-01

    Galactosialidosis is an inherited lysosomal storage disease caused by the combined deficiency of lysosomal sialidase and beta-galactosidase secondary to the deficiency of cathepsin A/protective protein, which is associated with sialidase and beta-galactosidase in a high-molecular weight (1.27MDa) complex. Clinical phenotypes of patients as well as the composition of compounds which are stored in patient's tissues implicate sialidase deficiency as the underlying pathogenic defect. The recent cloning and sequencing of lysosomal sialidase [Pshezhetsky, Richard, Michaud, Igdoura, Wang, Elsliger, Qu, Leclerc, Gravel, Dallaire and Potier (1997), Nature Genet. 15, 316-320] allowed us to study the molecular mechanism of sialidase deficiency in galactosialidosis. By Western blotting, using antibodies against the recombinant human enzyme, and by NH2-terminal sequencing, we showed that sialidase is synthesized as a 45.5 kDa precursor and after the cleavage of the 47-amino acid signal peptide and glycosylation becomes a 48.3 kDa mature active enzyme present in the 1.27 kDa complex. Transgenic expression of sialidase in cultured skin fibroblasts from normal controls and from galactosialidosis patients, followed by immunofluorescent and immunoelectron microscopy showed that in both normal and affected cells the expressed sialidase was localized on lysosomal and plasma membranes, but the amount of sialidase found in galactosialidosis cells was approximately 5-fold reduced. Metabolic labelling studies demonstrated that the 48.3 kDa mature active form of sialidase was stable in normal fibroblasts (half-life approximately 2.7 h), whereas in galactosialidosis fibroblasts the enzyme was rapidly converted (half-life approximately 30 min) into 38.7 and 24 kDa catalytically inactive forms. Altogether our data provide evidence that the molecular mechanism of sialidase deficiency in galactosialidosis is associated with abnormal proteolytic cleavage and fast degradation. PMID:9480870

  10. Carnosine and Homocarnosine Degradation Mechanisms by the Human Carnosinase Enzyme CN1: Insights from Multiscale Simulations.

    PubMed

    Pavlin, Matic; Rossetti, Giulia; De Vivo, Marco; Carloni, Paolo

    2016-05-17

    The endogenous dipeptide l-carnosine, and its derivative homocarnosine, prevent and reduce several pathologies like amytrophic lateral sclerosis (ALS), Alzheimer's disease, and Parkinson's disease. Their beneficial action is severely hampered because of the hydrolysis by carnosinase enzymes, in particular the human carnosinase, hCN1. This belongs to the metallopeptidase M20 family, where a cocatalytic active site is formed by two Zn(2+) ions, bridged by a hydroxide anion. The protein may exist as a monomer and as a dimer in vivo. Here we used hybrid quantum mechanics/molecular mechanics simulations based on the dimeric apoenzyme's structural information to predict the Michaelis complexes with l-carnosine and its derivative homocarnosine. On the basis of our calculations, we suggest that (i) l-carnosine degradation occurs through a nucleophilic attack of a Zn(2+)-coordinated bridging moiety for both monomer and dimer. This mechanistic hypothesis for hCN1 catalysis differs from previous proposals, while it is in agreement with available experimental data. (ii) The experimentally measured higher affinity of homocarnosine for the enzyme relative to l-carnosine might be explained, at least in part, by more extensive interactions inside the monomeric and dimeric hCN1's active site. (iii) Hydrogen bonds at the binding site, present in the dimer but absent in the monomer, might play a role in the experimentally observed higher activity of the dimeric form. Investigations of the enzymatic reaction are required to establish or disprove this hypothesis. Our results may serve as a basis for the design of potent hCN1 inhibitors. PMID:27105448

  11. Thermo-mechanical processing of austenitic steel to mitigate surface related degradation

    NASA Astrophysics Data System (ADS)

    Idell, Yaakov Jonathan

    Thermo-mechanical processing plays an important role in materials property optimization through microstructure modification, required by demanding modern materials applications. Due to the critical role of austenitic stainless steels, such as 316L, as structural components in harsh environments, e.g. in nuclear power plants, improved degradation resistance is desirable. A novel two-dimensional plane strain machining process has shown promise achieving significant grain size refinement through severe plastic deformation (SPD) and imparting large strains in the surface and subsurface regions of the substrate in various metals and alloys. The deformation process creates a heavily deformed 20 -- 30 micron thick nanocrystalline surface layer with increased hardness and minimal martensite formation. Post-deformation processing annealing treatments have been applied to assess stability of the refined scale microstructures and the potential for obtaining grain boundary engineered microstructures with increased fraction of low-energy grain boundaries and altered grain boundary network structure. Varying the deformation and heat treatment process parameters, allows for development of a full understanding of the nanocrystalline layer and cross-section of the surface substrate created. Micro-characterization was performed using hardness measurements, magnetometry, x-ray diffraction, scanning and transmission electron microscopy to assess property and microstructural changes. This study provides a fundamental understanding of two-dimensional plane strain machining as a thermo-mechanical processing technique, which may in the future deliver capabilities for creating grain boundary engineered surface modified components, typified by a combination of grain refinement with improved grain boundary network interconnectivity attributes suitable for use in harsh environments, such as those in commercial nuclear power plants where improved resistance to irradiation stress corrosion

  12. Degradation of abamectin by newly isolated Stenotrophomonas maltophilia ZJB-14120 and characterization of its abamectin-tolerance mechanism.

    PubMed

    Wang, Yuan-Shan; Zheng, Xing-Chang; Hu, Qi-Wei; Zheng, Yu-Guo

    2015-06-01

    An abamectin (ABM)-degrading bacterium, Stenotrophomonas maltophilia ZJB-14120, was isolated and identified. This strain is capable of degrading 84.82% of ABM at an initial concentration of 200 mg/L over a 48 h incubation period. This strain showed efficient biodegradation ability (7.81 mg/L/h) to ABM and high tolerance (1000 mg/L) to all macrolides tested. In addition to ABM, emamectin, erythromycin and spiramycin can also be degraded by this strain. Modifications involving either reduction of the double bond between C22-C23 or replacement of the C25-group of ABM with a cyclohexyl group can completely inhibit biodegradation of ABM. The ABM-degrading capability of strain ZJB-14120 is likely to be intrinsic to its metabolism and could be inhibited by incubating with erythromycin, azithromycin, spiramycin or rifampicin. A new and successive degradation pathway was proposed based on metabolite analysis. Although there is evidence for metabolite inhibition, this strain has high ABM degradation activity and reusability. Further investigation showed that activated macrolide efflux pump(s) and an undetermined mechanism for regulating the intracellular ABM concentration are responsible for normal uptake of essential metabolites while pumping out excess harmful compounds. Strain ZJB-14120 may provide efficient treatment of water and soil contaminated by toxic levels of abamectin and emamectin. PMID:25957243

  13. Age-related cochlear synaptopathy: an early-onset contributor to auditory functional decline.

    PubMed

    Sergeyenko, Yevgeniya; Lall, Kumud; Liberman, M Charles; Kujawa, Sharon G

    2013-08-21

    Aging listeners experience greater difficulty understanding speech in adverse listening conditions and exhibit degraded temporal resolution, even when audiometric thresholds are normal. When threshold evidence for peripheral involvement is lacking, central and cognitive factors are often cited as underlying performance declines. However, previous work has uncovered widespread loss of cochlear afferent synapses and progressive cochlear nerve degeneration in noise-exposed ears with recovered thresholds and no hair cell loss (Kujawa and Liberman 2009). Here, we characterize age-related cochlear synaptic and neural degeneration in CBA/CaJ mice never exposed to high-level noise. Cochlear hair cell and neuronal function was assessed via distortion product otoacoustic emissions and auditory brainstem responses, respectively. Immunostained cochlear whole mounts and plastic-embedded sections were studied by confocal and conventional light microscopy to quantify hair cells, cochlear neurons, and synaptic structures, i.e., presynaptic ribbons and postsynaptic glutamate receptors. Cochlear synaptic loss progresses from youth (4 weeks) to old age (144 weeks) and is seen throughout the cochlea long before age-related changes in thresholds or hair cell counts. Cochlear nerve loss parallels the synaptic loss, after a delay of several months. Key functional clues to the synaptopathy are available in the neural response; these can be accessed noninvasively, enhancing the possibilities for translation to human clinical characterization. PMID:23966690

  14. Radiation Therapy for Neovascular Age-related Macular Degeneration

    SciTech Connect

    Kishan, Amar U.; Modjtahedi, Bobeck S.; Morse, Lawrence S.; Lee, Percy

    2013-03-01

    In the enormity of the public health burden imposed by age-related macular degeneration (ARMD), much effort has been directed toward identifying effective and efficient treatments. Currently, anti-vascular endothelial growth factor (VEGF) injections have demonstrated considerably efficacy in treating neovascular ARMD, but patients require frequent treatment to fully benefit. Here, we review the rationale and evidence for radiation therapy of ARMD. The results of early photon external beam radiation therapy are included to provide a framework for the sequential discussion of evidence for the usage of stereotactic radiation therapy, proton therapy, and brachytherapy. The evidence suggests that these 3 modern modalities can provide a dose-dependent benefit in the treatment of ARMD. Most importantly, preliminary data suggest that all 3 can be used in conjunction with anti-VEGF therapeutics, thereby reducing the frequency of anti-VEGF injections required to maintain visual acuity.

  15. Molecular pathology of age-related macular degeneration

    PubMed Central

    Ding, Xiaoyan; Patel, Mrinali; Chan, Chi-Chao

    2009-01-01

    Age-related macular degeneration (AMD) is a leading cause of irreversible blindness in the world. Although the etiology and pathogenesis of AMD remain largely unclear, a complex interaction of genetic and environmental factors is thought to exist. AMD pathology is characterized by degeneration involving the retinal photoreceptors, retinal pigment epithelium, and Bruch’s membrane, as well as, in some cases, alterations in choroidal capillaries. Recent research on the genetic and molecular underpinnings of AMD brings to light several basic molecular pathways and pathophysiological processes that might mediate AMD risk, progression, and/or response to therapy. This review summarizes, in detail, the molecular pathological findings in both humans and animal models, including genetic variations in CFH, CX3CR1, and ARMS2/HtrA1, as well as the role of numerous molecules implicated in inflammation, apoptosis, cholesterol trafficking, angiogenesis, and oxidative stress. PMID:19026761

  16. Complement Factor H Polymorphism in Age-Related Macular Degeneration

    PubMed Central

    Klein, Robert J.; Zeiss, Caroline; Chew, Emily Y.; Tsai, Jen-Yue; Sackler, Richard S.; Haynes, Chad; Henning, Alice K.; SanGiovanni, John Paul; Mane, Shrikant M.; Mayne, Susan T.; Bracken, Michael B.; Ferris, Frederick L.; Ott, Jurg; Barnstable, Colin; Hoh., Josephine

    2006-01-01

    Age-related macular degeneration (AMD) is a major cause of blindness in the elderly. We report a genome-wide screen of 96 cases and 50 controls for polymorphisms associated with AMD. Among 116,204 single-nucleotide polymorphisms genotyped, an intronic and common variant in the complement factor H gene (CFH) is strongly associated with AMD (nominal P value <10−7). In individuals homozygous for the risk allele, the likelihood of AMD is increased by a factor of 7.4 (95% confidence interval 2.9 to 19). Resequencing revealed a polymorphism in linkage disequilibrium with the risk allele representing a tyrosine-histidine change at amino acid 402. This polymorphism is in a region of CFH that binds heparin and C-reactive protein. The CFH gene is located on chromosome 1 in a region repeatedly linked to AMD in family-based studies. PMID:15761122

  17. Translational strategies in aging and age-related disease.

    PubMed

    Armanios, Mary; de Cabo, Rafael; Mannick, Joan; Partridge, Linda; van Deursen, Jan; Villeda, Saul

    2015-12-01

    Aging is a risk factor for several of the world's most prevalent diseases, including neurodegenerative disorders, cancer, cardiovascular disease and metabolic disease. Although our understanding of the molecular pathways that contribute to the aging process and age-related disease is progressing through the use of model organisms, how to apply this knowledge in the clinic is less clear. In September, Nature Medicine, in collaboration with the Volkswagen Foundation, hosted a conference at the beautiful Herrenhausen Palace in Hannover, Germany with the goal of broadening our understanding of the aging process and its meaning as a 'risk factor' in disease. Here, several of the speakers at that conference answer questions posed by Nature Medicine. PMID:26646495

  18. Retinal phagocytes in age-related macular degeneration

    PubMed Central

    Kim, Soo-Young

    2015-01-01

    Age-related macular degeneration (AMD) is the leading cause of blindness in industrial countries. Vision loss caused by AMD results from geographic atrophy (dry AMD) and/or choroidal neovascularization (wet AMD). Presently, the etiology and pathogenesis of AMD is not fully understood and there is no effective treatment. Oxidative stress in retinal pigment epithelial (RPE) cells is considered to be one of the major factors contributing to the pathogenesis of AMD. Also retinal glia, as scavengers, are deeply related with diseases and could play a role. Therefore, therapeutic approaches for microglia and Müller glia, as well as RPE, may lead to new strategies for AMD treatment. This review summarizes the pathological findings observed in RPE cells, microglia and Müller glia of AMD murine models. PMID:26052551

  19. Treatment of neovascular age-related macular degeneration: Current therapies

    PubMed Central

    Augustin, Albert J; Scholl, Stefan; Kirchhof, Janna

    2009-01-01

    Choroidal neovascularization (CNV) secondary to age-related macular degeneration (AMD) is now the leading cause of blindness and severe vision loss among people over the age of 40 in the Western world. Its prevalence is certain to increase substantially as the population ages. Treatments currently available for the disease include laser photocoagulation, verteporfin photodynamic therapy, and intravitreal injections of corticosteroids and anti-angiogenic agents. Many studies have reported the benefits of each of these treatments, although none is without its risks. No intervention actually cures AMD, nor the neovascularization associated with it. However, its symptoms are treated with varying degrees of success. Some treatments stabilize or arrest the progress of the disease. Others have been shown to reverse some of the damage that has already been done. These treatments can even lead to visual improvement. This paper will review the major classes of drugs and therapies designed to treat this condition. PMID:19668562

  20. Targeting MAPK Signaling in Age-Related Macular Degeneration

    PubMed Central

    Kyosseva, Svetlana V.

    2016-01-01

    Age-related macular degeneration (AMD) is a major cause of irreversible blindness affecting elderly people in the world. AMD is a complex multifactorial disease associated with demographic, genetics, and environmental risk factors. It is well established that oxidative stress, inflammation, and apoptosis play critical roles in the pathogenesis of AMD. The mitogen-activated protein kinase (MAPK) signaling pathways are activated by diverse extracellular stimuli, including growth factors, mitogens, hormones, cytokines, and different cellular stressors such as oxidative stress. They regulate cell proliferation, differentiation, survival, and apoptosis. This review addresses the novel findings from human and animal studies on the relationship of MAPK signaling with AMD. The use of specific MAPK inhibitors may represent a potential therapeutic target for the treatment of this debilitating eye disease. PMID:27385915

  1. Complement factor H polymorphism and age-related macular degeneration.

    PubMed

    Edwards, Albert O; Ritter, Robert; Abel, Kenneth J; Manning, Alisa; Panhuysen, Carolien; Farrer, Lindsay A

    2005-04-15

    Age-related macular degeneration (AMD) is a common, late-onset, and complex trait with multiple risk factors. Concentrating on a region harboring a locus for AMD on 1q25-31, the ARMD1 locus, we tested single-nucleotide polymorphisms for association with AMD in two independent case-control populations. Significant association (P = 4.95 x 10(-10)) was identified within the regulation of complement activation locus and was centered over a tyrosine-402 --> histidine-402 protein polymorphism in the gene encoding complement factor H. Possession of at least one histidine at amino acid position 402 increased the risk of AMD 2.7-fold and may account for 50% of the attributable risk of AMD. PMID:15761121

  2. Age-Related Macular Degeneration: Insights into Inflammatory Genes

    PubMed Central

    Ragazzo, Michele; Missiroli, Filippo; Borgiani, Paola; Angelucci, Francesco; Marsella, Luigi Tonino; Cusumano, Andrea; Novelli, Giuseppe; Ricci, Federico; Giardina, Emiliano

    2014-01-01

    Age-related macular degeneration (AMD) is a progressive neurodegenerative disease that affects approximately 8.7% of elderly people worldwide (>55 years old). AMD is characterized by a multifactorial aetiology that involves several genetic and environmental risk factors (genes, ageing, smoking, family history, dietary habits, oxidative stress, and hypertension). In particular, ageing and cigarette smoking (including oxidative compounds and reactive oxygen species) have been shown to significantly increase susceptibility to the disease. Furthermore, different genes (CFH, CFI, C2, C3, IL-6, IL-8, and ARMS2) that play a crucial role in the inflammatory pathway have been associated with AMD risk. Several genetic and molecular studies have indicated the participation of inflammatory molecules (cytokines and chemokines), immune cells (macrophages), and complement proteins in the development and progression of the disease. Taking into consideration the genetic and molecular background, this review highlights the genetic role of inflammatory genes involved in AMD pathogenesis and progression. PMID:25478207

  3. Age-related differences in arithmetic strategy sequential effects.

    PubMed

    Lemaire, Patrick

    2016-03-01

    In this article, I review a series of new findings concerning how age-related changes in strategic variations are modulated by sequential effects. Sequential effects refer to how strategy selection and strategy execution on current problems are influenced by which strategy is used on immediately preceding problems. Two sequential effects during strategy selection (i.e., strategy revisions and strategy perseverations) and during strategy execution (i.e., strategy switch costs and modulations of poorer strategy effects) are presented. I also discuss how these effects change with age during adulthood. These phenomena are important, as they shed light on arithmetic processes and how these processes change with age during adulthood. In particular, they speak to the role of executive control while participants select and execute arithmetic strategies. Finally, I discuss the implications of sequential effects for theories of strategies and of arithmetic. (PsycINFO Database Record PMID:26372058

  4. Gene Therapies for Neovascular Age-Related Macular Degeneration.

    PubMed

    Pechan, Peter; Wadsworth, Samuel; Scaria, Abraham

    2015-07-01

    Pathological neovascularization is a key component of the neovascular form (also known as the wet form) of age-related macular degeneration (AMD) and proliferative diabetic retinopathy. Several preclinical studies have shown that antiangiogenesis strategies are effective for treating neovascular AMD in animal models. Vascular endothelial growth factor (VEGF) is one of the main inducers of ocular neovascularization, and several clinical trials have shown the benefits of neutralizing VEGF in patients with neovascular AMD or diabetic macular edema. In this review, we summarize several preclinical and early-stage clinical trials with intraocular gene therapies, which have the potential to reduce or eliminate the repeated intravitreal injections that are currently required for the treatment of neovascular AMD. PMID:25524721

  5. Age-related differences in multiple task monitoring.

    PubMed

    Todorov, Ivo; Del Missier, Fabio; Mäntylä, Timo

    2014-01-01

    Coordinating multiple tasks with narrow deadlines is particularly challenging for older adults because of age related decline in cognitive control functions. We tested the hypothesis that multiple task performance reflects age- and gender-related differences in executive functioning and spatial ability. Young and older adults completed a multitasking session with four monitoring tasks as well as separate tasks measuring executive functioning and spatial ability. For both age groups, men exceeded women in multitasking, measured as monitoring accuracy. Individual differences in executive functioning and spatial ability were independent predictors of young adults' monitoring accuracy, but only spatial ability was related to sex differences. For older adults, age and executive functioning, but not spatial ability, predicted multitasking performance. These results suggest that executive functions contribute to multiple task performance across the adult life span and that reliance on spatial skills for coordinating deadlines is modulated by age. PMID:25215609

  6. Age-related macular degeneration: Evidence of a major gene

    SciTech Connect

    Bhatt, S.; Warren, C.; Yang, H.

    1994-09-01

    Age-related macular degeneration is a major cause of blindness in developing countries. It remains a very poorly understood disorder. Although environmental and genetic factors have been implicated in its pathogenesis, none have been firmly implicated. The purpose of this study was to use pedigree analysis to evaluate the possible role of a major gene as a determinant of familial aggregation. Information was collected regarding occupation, smoking, sun exposure, associated medical problems and family history. 50 probands with age-related macular degeneration (ARMD) and 39 age, race and sex-matched controls were included in the study. In the ARMD group 15/50 (30%) of probands reported a positive family history; 22 out of 222 first degree relatives over age 60 were reported to be affected. In the control groups, none of the 138 first degree relatives over age 50 had a history of ARMD. This difference is statistically significant (p = 0.0003), indicating that genetic factors may play an important role in the pathogenesis of ARMD. In the ARMD group more siblings as compared to parents (16/127 vs. 5/82) were affected. 5/50 (10%) of the ARMD probands also gave a history of a second degree relative affected with ARMD, compared to none known among the relatives of controls. Data from 50 pedigrees were analyzed by complex segregation analysis under a class A regressive logistic model using the REGD program implemented in the SAGE package. Preliminary results allow rejection of a polygenic model and suggest there is a major gene for ARMD in these families. The inheritance model most compatible with the observed familial aggregation is autosomal recessive. In conclusion, these results are suggestive of a major gene effect in the etiology of ARMD. Identification of a major gene effect is a first step to further pursue linkage analysis and to search for the gene(s) involved in the causation of ARMD.

  7. Genetic risk factors and age-related macular degeneration (AMD)

    PubMed Central

    Mousavi, Maryam; Armstrong, Richard A.

    2013-01-01

    Age related macular degeneration (AMD) is the leading cause of blindness in individuals older than 65 years of age. It is a multifactorial disorder and identification of risk factors enables individuals to make lifestyle choices that may reduce the risk of disease. Collaboration between geneticists, ophthalmologists, and optometrists suggests that genetic risk factors play a more significant role in AMD than previously thought. The most important genes are associated with immune system modulation and the complement system, e.g., complement factor H (CFH), factor B (CFB), factor C3, and serpin peptidase inhibitor (SERPING1). Genes associated with membrane transport, e.g., ATP-binding cassette protein (ABCR) and voltage-dependent calcium channel gamma 3 (CACNG3), the vascular system, e.g., fibroblast growth factor 2 (FGF2), fibulin-5, lysyl oxidase-like gene (LOXL1) and selectin-P (SELP), and with lipid metabolism, e.g., apolipoprotein E (APOE) and hepatic lipase (LIPC) have also been implicated. In addition, several other genes exhibit some statistical association with AMD, e.g., age-related maculopathy susceptibility protein 2 (ARMS2) and DNA excision repair protein gene (ERCC6) but more research is needed to establish their significance. Modifiable risk factors for AMD should be discussed with patients whose lifestyle and/or family history place them in an increased risk category. Furthermore, calculation of AMD risk using current models should be recommended as a tool for patient education. It is likely that AMD management in future will be increasingly influenced by assessment of genetic risk as such screening methods become more widely available.

  8. Age-related oxidative modifications of transthyretin modulate its amyloidogenicity

    PubMed Central

    Zhao, Lei; Buxbaum, Joel N; Reixach, Natàlia

    2013-01-01

    The transthyretin amyloidoses are diseases of protein misfolding characterized by the extracellular deposition of fibrils and other aggregates of the homotetrameric protein transthyretin (TTR) in peripheral nerves, heart and other tissues. Age is the major risk factor for the development of these diseases. We hypothesized that an age-associated increase in protein oxidation could be involved in the onset of the senile forms of the TTR amyloidoses. To test this hypothesis we have produced and characterized relevant age-related oxidative modifications of wild type (WT) and the Val122Ile (V122I) TTR variant, both involved in cardiac TTR deposition in the elderly. Our studies show that methionine/cysteine oxidized TTR and carbonylated TTR either from WT or the V122I variant, are thermodynamically less stable than their non-oxidized counterparts. Moreover, carbonylated WT and carbonylated V122I TTR have a greater propensity to form aggregates and fibrils than WT and V122I TTR, respectively, at physiologically attainable pH. It is well known that TTR tetramer dissociation, the limiting step for aggregation and amyloid fibril formation, can be prevented by small molecules that bind the TTR tetramer interface. Here, we report that carbonylated WT TTR is less amenable to resveratrol-mediated tetramer stabilization than WT TTR. All the oxidized forms of TTR tested are cytotoxic to a human cardiomyocyte cell line known to be a target for cardiac-specific TTR variants. Overall these studies demonstrate that age-related oxidative modifications of TTR can contribute to the onset of the senile forms of the TTR amyloidoses. PMID:23414091

  9. Age-related oxidative modifications of transthyretin modulate its amyloidogenicity.

    PubMed

    Zhao, Lei; Buxbaum, Joel N; Reixach, Natàlia

    2013-03-19

    The transthyretin amyloidoses are diseases of protein misfolding characterized by the extracellular deposition of fibrils and other aggregates of the homotetrameric protein transthyretin (TTR) in peripheral nerves, heart, and other tissues. Age is the major risk factor for the development of these diseases. We hypothesized that an age-associated increase in the level of protein oxidation could be involved in the onset of the senile forms of the TTR amyloidoses. To test this hypothesis, we have produced and characterized relevant age-related oxidative modifications of the wild type (WT) and the Val122Ile (V122I) TTR variant, both involved in cardiac TTR deposition in the elderly. Our studies show that methionine/cysteine-oxidized TTR and carbonylated TTR from either the WT or the V122I variant are thermodynamically less stable than their nonoxidized counterparts. Moreover, carbonylated WT and carbonylated V122I TTR have a stronger propensity to form aggregates and fibrils than WT and V122I TTR, respectively, at physiologically attainable pH values. It is well-known that TTR tetramer dissociation, the limiting step for aggregation and amyloid fibril formation, can be prevented by small molecules that bind the TTR tetramer interface. Here, we report that carbonylated WT TTR is less amenable to resveratrol-mediated tetramer stabilization than WT TTR. All the oxidized forms of TTR tested are cytotoxic to a human cardiomyocyte cell line known to be a target for cardiac-specific TTR variants. Overall, these studies demonstrate that age-related oxidative modifications of TTR can contribute to the onset of the senile forms of the TTR amyloidoses. PMID:23414091

  10. Age-related vascular stiffening: causes and consequences

    PubMed Central

    Kohn, Julie C.; Lampi, Marsha C.; Reinhart-King, Cynthia A.

    2015-01-01

    Arterial stiffening occurs with age and is closely associated with the progression of cardiovascular disease. Stiffening is most often studied at the level of the whole vessel because increased stiffness of the large arteries can impose increased strain on the heart leading to heart failure. Interestingly, however, recent evidence suggests that the impact of increased vessel stiffening extends beyond the tissue scale and can also have deleterious microscale effects on cellular function. Altered extracellular matrix (ECM) architecture has been recognized as a key component of the pre-atherogenic state. Here, the underlying causes of age-related vessel stiffening are discussed, focusing on age-related crosslinking of the ECM proteins as well as through increased matrix deposition. Methods to measure vessel stiffening at both the macro- and microscale are described, spanning from the pulse wave velocity measurements performed clinically to microscale measurements performed largely in research laboratories. Additionally, recent work investigating how arterial stiffness and the changes in the ECM associated with stiffening contributed to endothelial dysfunction will be reviewed. We will highlight how changes in ECM protein composition contribute to atherosclerosis in the vessel wall. Lastly, we will discuss very recent work that demonstrates endothelial cells (ECs) are mechano-sensitive to arterial stiffening, where changes in stiffness can directly impact EC health. Overall, recent studies suggest that stiffening is an important clinical target not only because of potential deleterious effects on the heart but also because it promotes cellular level dysfunction in the vessel wall, contributing to a pathological atherosclerotic state. PMID:25926844

  11. Age-Related Neurochemical Changes in the Vestibular Nuclei

    PubMed Central

    Smith, Paul F.

    2016-01-01

    There is evidence that the normal aging process is associated with impaired vestibulo-ocular reflexes (VOR) and vestibulo-spinal reflexes, causing reduced visual acuity and postural instability. Nonetheless, the available evidence is not entirely consistent, especially with respect to the VOR. Some recent studies have reported that VOR gain can be intact even above 80 years of age. Similarly, although there is evidence for age-related hair cell loss and neuronal loss in Scarpa’s ganglion and the vestibular nucleus complex (VNC), it is not entirely consistent. Whatever structural and functional changes occur in the VNC as a result of aging, either to cause vestibular impairment or to compensate for it, neurochemical changes must underlie them. However, the neurochemical changes that occur in the VNC with aging are poorly understood because the available literature is very limited. This review summarizes and critically evaluates the available evidence relating to the noradrenaline, serotonin, dopamine, glutamate, GABA, glycine, and nitric oxide neurotransmitter systems in the aging VNC. It is concluded that, at present, it is difficult, if not impossible, to relate the neurochemical changes observed to the function of specific VNC neurons and whether the observed changes are the cause of a functional deficit in the VNC or an effect of it. A better understanding of the neurochemical changes that occur during aging may be important for the development of potential drug treatments for age-related vestibular disorders. However, this will require the use of more sophisticated methodology such as in vivo microdialysis with single neuron recording and perhaps new technologies such as optogenetics. PMID:26973593

  12. Age-Related Neurochemical Changes in the Vestibular Nuclei.

    PubMed

    Smith, Paul F

    2016-01-01

    There is evidence that the normal aging process is associated with impaired vestibulo-ocular reflexes (VOR) and vestibulo-spinal reflexes, causing reduced visual acuity and postural instability. Nonetheless, the available evidence is not entirely consistent, especially with respect to the VOR. Some recent studies have reported that VOR gain can be intact even above 80 years of age. Similarly, although there is evidence for age-related hair cell loss and neuronal loss in Scarpa's ganglion and the vestibular nucleus complex (VNC), it is not entirely consistent. Whatever structural and functional changes occur in the VNC as a result of aging, either to cause vestibular impairment or to compensate for it, neurochemical changes must underlie them. However, the neurochemical changes that occur in the VNC with aging are poorly understood because the available literature is very limited. This review summarizes and critically evaluates the available evidence relating to the noradrenaline, serotonin, dopamine, glutamate, GABA, glycine, and nitric oxide neurotransmitter systems in the aging VNC. It is concluded that, at present, it is difficult, if not impossible, to relate the neurochemical changes observed to the function of specific VNC neurons and whether the observed changes are the cause of a functional deficit in the VNC or an effect of it. A better understanding of the neurochemical changes that occur during aging may be important for the development of potential drug treatments for age-related vestibular disorders. However, this will require the use of more sophisticated methodology such as in vivo microdialysis with single neuron recording and perhaps new technologies such as optogenetics. PMID:26973593

  13. Age-related changes in the tiger salamander retina.

    PubMed

    Townes-Anderson, E; Colantonio, A; St Jules, R S

    1998-05-01

    Tiger salamanders have been used in visual science because of the large size of their cells and the ease of preparation and maintenance of in vitro retinal preparations. We have found that salamanders over 27 cm in length show a variety of visual abnormalities. Compared to smaller animals (15-23 cm), large animals exhibited a decrease in visual responses determined by tests of the optomotor reflex. Small animals responded correctly an average of 84.5% of the time in visual testing at three light levels compared to an average of 68.4% for the large animals with the poorest visual performance at the lowest level of illumination. In addition, large animals contained (i) histological degeneration of the outer retina, in particular, loss and disruption of outer segments and abnormalities of the retinal pigmented epithelium, (ii) loss of cells, including photoreceptors, by apoptosis as evaluated with the TUNEL technique, and (iii) an increase in the number of macrophages and lymphocytes within the retina as determined by morphological examination. These histological changes were present in all large animals and all quadrants of their retinas. In contrast, small animals showed virtually no retinal degeneration, no TUNEL-positive cells, and few immune-like cells in the retina. Since large animals are also older animals. the visual changes are age-related. Loss of visual function and histological degeneration in the outer retina also typify aged human eyes. Thus, we propose that large salamanders serve as an animal model for age-related retinal degeneration. In addition to providing a source of aging retina that is readily accessible to experimental manipulation, the salamander provides a pigmented retina with a mixed (2:1, rod:cone) population of photoreceptors, similar to the degeneration-prone parafoveal region of the human eye. PMID:9631666

  14. Kinetics and mechanism of the degradation of methyl parathion in aqueous hydrogen sulfide solution: investigation of natural organic matter effects.

    PubMed

    Guo, Xiaofen; Jans, Urs

    2006-02-01

    The kinetics of the transformation of methyl parathion have been investigated in aqueous solution containing reduced sulfur species and small concentrations of natural organic matter (NOM) from different sources such as soil, river, and peat. It was shown that NOM mediates the degradation of methyl parathion in aqueous solutions containing hydrogen sulfide. After evaluating and quantifying the effect of the NOM concentration on the degradation kinetics of methyl parathion in the presence of hydrogen sulfide, it was found that the observed pseudo-first-order reaction rate constants (k(obs)) were proportional to NOM concentrations. The influence of pH on the degradation of methyl parathion in the aqueous solutions containing hydrogen sulfide and NOM has been studied. The rate of degradation of methyl parathion was strongly pH dependent. The results indicate k(obs) with a commercially available humic acid has a maximum value at approximately pH 8.3. Two main reaction mechanisms are identified to dominate the degradation of methyl parathion in aqueous solution containing hydrogen sulfide and NOM based on the products aminomethyl parathion and desmethyl methyl parathion. The two mechanisms are nitro-group reduction and nucleophilic attack at the methoxy-carbon. The reduction of the nitro-group is only observed in the presence of NOM. The results of this study form an important base for the evaluation and interpretation of transformation processes of methyl parathion in the environment. PMID:16509335

  15. Effects of material thickness and processing method on poly(lactic-co-glycolic acid) degradation and mechanical performance.

    PubMed

    Shirazi, Reyhaneh Neghabat; Aldabbagh, Fawaz; Ronan, William; Erxleben, Andrea; Rochev, Yury; McHugh, Peter

    2016-10-01

    In this study, the effects of material thickness and processing method on the degradation rate and the changes in the mechanical properties of poly(lactic-co-glycolic acid) material during simulated physiological degradation were investigated. Two types of poly(lactic-co-glycolic acid) materials were considered: 0.12 mm solvent-cast films and 1 mm compression-moulded plates. The experimental results presented in this study were compared to the experimental results of Shirazi et al. (Acta Biomaterialia 10(11):4695-703, 2014) for 0.25 mm solvent-cast films. These experimental observations were used to validate the computational modelling predictions of Shirazi et al. (J Mech Behav Biomed Mater 54: 48-59, 2016) on critical diffusion length scale and also to refine the model parameters. The specific material processing methods considered here did not have a significant effect on the degradation rate and the changes in mechanical properties during degradation; however, they influenced the initial molecular weight and they determined the stiffness and hardness of the poly(lactic-co-glycolic acid) material. The experimental observations strongly supported the computational modelling predictions that showed no significant difference in the degradation rate and the changes in the elastic modulus of poly(lactic-co-glycolic acid) films for thicknesses larger than 100 μm. PMID:27590824

  16. Age-related changes in monocytes exacerbate neointimal hyperplasia after vascular injury

    PubMed Central

    Martinez, Laisel; Gomez, Camilo; Vazquez-Padron, Roberto I.

    2015-01-01

    Neointimal hyperplasia is the leading cause of restenosis after endovascular interventions. It is characterized by the accumulation of myofibroblast-like cells and extracellular matrix in the innermost layer of the wall and is exacerbated by inflammation. Monocytes from either young or aged rats were applied perivascularly to injured vascular walls of young recipient animals. Monocytes from aged rats, but not young donors, increased neointima thickness. Accordingly, the gene expression profiles of CD11b+ monocytes from aged rats showed significant up-regulation of genes involved in cellular adhesion, lipid degradation, cytotoxicity, differentiation, and inflammation. These included cadherin 13 (Cdh13), colony stimulating factor 1 (Csf1), chemokine C-X-C motif ligand 1 (Cxcl1), endothelial cell-selective adhesion molecule (Esam), and interferon gamma (Ifng). In conclusion, our results suggest that the increased inflammatory and adhesive profile of monocytes contributes to pathological wall remodeling in aged-related vascular diseases. PMID:25965835

  17. Age-related changes in monocytes exacerbate neointimal hyperplasia after vascular injury.

    PubMed

    Martinez, Laisel; Gomez, Camilo; Vazquez-Padron, Roberto I

    2015-07-10

    Neointimal hyperplasia is the leading cause of restenosis after endovascular interventions. It is characterized by the accumulation of myofibroblast-like cells and extracellular matrix in the innermost layer of the wall and is exacerbated by inflammation. Monocytes from either young or aged rats were applied perivascularly to injured vascular walls of young recipient animals. Monocytes from aged rats, but not young donors, increased neointima thickness. Accordingly, the gene expression profiles of CD11b+ monocytes from aged rats showed significant up-regulation of genes involved in cellular adhesion, lipid degradation, cytotoxicity, differentiation, and inflammation. These included cadherin 13 (Cdh13), colony stimulating factor 1 (Csf1), chemokine C-X-C motif ligand 1 (Cxcl1), endothelial cell-selective adhesion molecule (Esam), and interferon gamma (Ifng). In conclusion, our results suggest that the increased inflammatory and adhesive profile of monocytes contributes to pathological wall remodeling in aged-related vascular diseases. PMID:25965835

  18. MECHANICAL DEGRADATION OF EMPLACEMENT DRIFTS AT YUCCA MOUNTAIN - A CASE STUDY IN ROCK MECHANICS, PART 1: NONLITHOPHYSAL ROCK, PART 2: LITHOPHYSAL ROCK

    SciTech Connect

    M. Lin, D. Kicker, B. Damjanac, M. Board, and M. Karakouzian

    2006-02-27

    This paper outlines rock mechanics investigations associated with mechanical degradation of planned emplacement drifts at Yucca Mountain, which is the designated site for a US high-level nuclear waste repository. The factors leading to drift degradation include stresses from the overburden, stresses induced by the heat released from the emplaced waste, stresses due to seismically related ground motions, and time-dependent strength degradation. The welded tuff emplacement horizon consists of two groups of rock with distinct engineering properties: nonlithophysal units and lithophysal units, based on the relative proportion of lithophysal cavities. Part I of the paper concentrates on the generally hard, strong, and fractured nonlithophysal rock. The degradation behavior of the tunnels in the nonlithophysal rock is controlled by the occurrence of keyblocks. A statistically equivalent fracture model was generated based on extensive underground fracture mapping data from the Exploratory Studies Facility at Yucca Mountain. Three-dimensional distinct block analyses, generated with the fracture patterns randomly selected from the fracture model, were developed with the consideration of in situ, thermal, seismic loads. In this study, field data, laboratory data, and numerical analyses are well integrated to provide a solution for the unique problem of modeling drift degradation throughout the regulatory period for repository performance.

  19. Mechanisms Underpinning Degradation of Protective Oxides and Thermal Barrier Coatings in High Hydrogen Content (HHC) - Fueled Turbines

    SciTech Connect

    Mumm, Daniel

    2013-08-31

    The overarching goal of this research program has been to evaluate the potential impacts of coal-derived syngas and high-hydrogen content fuels on the degradation of turbine hot-section components through attack of protective oxides and thermal barrier coatings. The primary focus of this research program has been to explore mechanisms underpinning the observed degradation processes, and connections to the combustion environments and characteristic non-combustible constituents. Based on the mechanistic understanding of how these emerging fuel streams affect materials degradation, the ultimate goal of the program is to advance the goals of the Advanced Turbine Program by developing materials design protocols leading to turbine hot-section components with improved resistance to service lifetime degradation under advanced fuels exposures. This research program has been focused on studying how: (1) differing combustion environments – relative to traditional natural gas fired systems – affect both the growth rate of thermally grown oxide (TGO) layers and the stability of these oxides and of protective thermal barrier coatings (TBCs); and (2) how low levels of fuel impurities and characteristic non-combustibles interact with surface oxides, for instance through the development of molten deposits that lead to hot corrosion of protective TBC coatings. The overall program has been comprised of six inter-related themes, each comprising a research thrust over the program period, including: (i) evaluating the role of syngas and high hydrogen content (HHC) combustion environments in modifying component surface temperatures, heat transfer to the TBC coatings, and thermal gradients within these coatings; (ii) understanding the instability of TBC coatings in the syngas and high hydrogen environment with regards to decomposition, phase changes and sintering; (iii) characterizing ash deposition, molten phase development and infiltration, and associated corrosive

  20. Improvement of physico-mechanical, thermomechanical, thermal and degradation properties of PCL/gelatin biocomposites: Effect of gamma radiation

    NASA Astrophysics Data System (ADS)

    Zaman, Haydar U.; Beg, M. D. H.

    2015-04-01

    This research was to study the effects of gelatin content variation and gamma radiation after the 2-ethylhexyl acrylate (EHA) pre-treatment on the foundamental properties of gelatin film laminated polycaprolactone (PCL) biocomposites. PCL/gelatin film (PCL/GF) composites were fabricated by compression molding and their properties were studied by physico-mechanical, thermomechanical, thermal and degradation properties. The results from mechanical properties such as tensile modulus and impact strength of the composites increased with increasing of gelatin content up to 10 wt% and then decreased while the tensile strength and elongation at break decreased. EHA monomer (2-8 wt%) was added to the gelatin solution and films were prepared by casting and found to increase the mechanical properties of the PCL/EHA blended gelatin film (PCL/EGF) composites. Treatment of the gelatin film with gamma radiation after the EHA pre-treatment showed the best mechanical properties of the resulting composites. Dynamic mechanical thermal analysis results showed that the storage modulus of the PCL/EGF and PCL/EHA blended gelatin film with gamma radiation (PCL/GEGF) composites was increased significantly. The degradation properties in water and soil were determined for the non-irradiated and irradiated composites. It was observed that the non-irradiated composite degrades more than that of the irradiated composites.

  1. Age-Related Changes in CD8 T Cell Homeostasis and Immunity to Infection

    PubMed Central

    Nikolich-Zugich, Janko; Li, Gang; Uhrlaub, Jennifer L.; Renkema, Kristin R.; Smithey, Megan J.

    2012-01-01

    Studies of CD8 T cell responses to vaccination or infection with various pathogens in both animal models and human subjects have revealed a markedly consistent array of age-related defects. In general, recent work shows that aged CD8 T cell responses are decreased in magnitude, and show poor differentiation into effector cells, with a reduced arsenal of effector functions. Here we review potential mechanisms underlying these defects. We specifically address phenotypic and numeric changes to the naïve CD8 T cell precursor pool, the impact of persistent viral infection(s) and inflammation, and contributions of the aging environment in which these cells are activated. PMID:22554418

  2. [The immunomodulatory role of retinal microglial cells in age-related macular degeneration].

    PubMed

    Zhang, P F; Sun, X D

    2016-05-11

    Age-related macular degeneration (AMD) is one of the major causes of visual impairment in the elder population. Recent studies have revealed that retinal microgliacytes may play an important role in the pathogenesis of AMD, and the activation of retinal microglia could regulate the progress of AMD. The immunomodulatory role of retinal microglial cells is reviewed in this article, so as to investigate the mechanism and provide new insight for prevention and treatment of AMD.(Chin J Ophthalmol, 2016, 52: 386-390). PMID:27220713

  3. Recent developments in the treatment of age-related macular degeneration

    PubMed Central

    Holz, Frank G.; Schmitz-Valckenberg, Steffen; Fleckenstein, Monika

    2014-01-01

    Age-related macular degeneration (AMD) is a common cause of visual loss in the elderly, with increasing prevalence due to increasing life expectancy. While the introduction of anti-VEGF therapy has improved outcomes, there are still major unmet needs and gaps in the understanding of underlying biological processes. These include early, intermediate, and atrophic disease stages. Recent studies have assessed therapeutic approaches addressing various disease-associated pathways, including complement inhibitors. Drug-delivery aspects are also relevant, as many agents have to be administered repeatedly. Herein, relevant pathogenetic factors and underlying mechanisms as well as recent and potential therapeutic approaches are reviewed. PMID:24691477

  4. Dry age-related macular degeneration: A currently unmet clinical need

    PubMed Central

    Girmens, Jean-François; Sahel, José-Alain; Marazova, Katia

    2012-01-01

    Summary Age-related macular degeneration (AMD) is a leading cause of severe visual impairment and disability in older people worldwide. Although considerable advances in the management of the neovascular form of AMD have been made in the last decade, no therapy is yet available for the advanced dry form of AMD (geographic atrophy). This review focuses on current trends in the development of new therapies targeting specific pathophysiological pathways of dry AMD. Increased understanding of the complex mechanisms that underlie dry AMD will help to address this largely unmet clinical need. PMID:25343081

  5. Modelling ecogeomorphic feedbacks: investigating mechanisms of land degradation in semi-arid grassland and shrubland

    NASA Astrophysics Data System (ADS)

    Turnbull, Laura; Mueller, Eva; Tietjen, Britta; Wainwright, John

    2014-05-01

    Across vast areas of the world's drylands, land degradation is exacerbated by ecohydrological processes, which alter the structure, function and connectivity of dryland hillslopes. These processes are often interlinked through feedback mechanisms in such a way that a trigger may result in a re-organization of the affected landscape. Here, we present a spatially explicit process-based ecogeomorphic model, MAHLERAN-EcoHyD to enhance our understanding of complex linkages between abiotic and biotic drivers and processes of degradation in drylands. This ecogeomorphic modelling approach is innovative in two main ways: it couples biotic and abiotic processes, and simulates intra and inter-event dynamics, thus overcoming a key limitation of previous modelling approaches in terms of their temporal scaling, by simulating key ecogeomorphic processes at process-relevant time steps. Redistribution of water, sediment and nutrients during high-intensity rainstorms is simulated at 1-sec time steps, soil moisture and transpiration dynamics at daily time steps, and vegetation dynamics (establishment, growth, mortality) at 14-day time steps, over a high-resolution 1x1 m grid. We use this innovative modelling approach to investigate soil-vegetation feedback mechanisms within a grassland-shrubland transition zone at the Sevilleta Long Term Ecological Research site in the south-western United States. Results from three modelling experiments are presented: the first modelling experiment investigates the impact of annual variations in individual high-intensity storms to assess long-term variations in runoff, soil-moisture conditions and sediment and nutrient fluxes over two decades; the second modelling experiment assesses the impact of vegetation composition on spatial changes in surface soil texture due to soil erosion by water; and the third modelling experiment investigates how long-term changes in vegetation alter feedbacks between biotic and abiotic processes using scenarios for

  6. Thermal degradation mechanism of triangular Ag@SiO2 nanoparticles.

    PubMed

    Gangishetty, Mahesh K; Scott, Robert W J; Kelly, Timothy L

    2016-06-14

    Triangular silver nanoparticles are promising materials for light harvesting applications because of their strong plasmon bands; these absorption bands are highly tunable, and can be varied over the entire visible range based on the particle size. A general concern with these materials is that they are unstable at elevated temperatures. When thermally annealed, they suffer from changes to the particle morphology, which in turn affects their optical properties. Because of this stability issue, these materials cannot be used in applications requiring elevated temperatures. In order to address this problem, it is important to first understand the degradation mechanism. Here, we measure the changes in particle morphology, oxidation state, and coordination environment of Ag@SiO2 nanotriangles caused by thermal annealing. UV-vis spectroscopy and TEM reveal that upon annealing the Ag@SiO2 nanotriangles in air, the triangular cores are truncated and smaller nanoparticles are formed. Ag K-edge X-ray absorption spectroscopy (XANES and EXAFS) shows that the small particles consist of Ag(0), and that there is a decrease in the Ag-Ag coordination number with an increase in the annealing temperature. We hypothesize that upon annealing Ag in air, it is first oxidized to AgxO, after which it subsequently decomposes back to well-dispersed Ag(0) nanoparticles. In contrast, when the Ag@SiO2 nanotriangles are annealed in N2, since there is no possibility of oxidation, no small particles are formed. Instead, the triangular core rearranges to form a disc-like shape. PMID:26875498

  7. Inhibition of endogenous NGF degradation induces mechanical allodynia and thermal hyperalgesia in rats

    PubMed Central

    2013-01-01

    Background We have previously shown a sprouting of sympathetic fibers into the upper dermis of the skin following subcutaneous injection of complete Freund’s adjuvant (CFA) into the hindpaw. This sprouting correlated with an increase in pain-related sensitivity. We hypothesized that this sprouting and pain-related behavior were caused by an increase in nerve growth factor (NGF) levels. In this study, we investigated whether the inhibition of mature NGF degradation, using a matrix metalloproteinase 2 and 9 (MMP-2/9) inhibitor, was sufficient to reproduce a similar phenotype. Results Behavioral tests performed on male Sprague–Dawley rats at 1, 3, 7 and 14 days after intra-plantar MMP-2/9 inhibitor administration demonstrated that acute and chronic injections of the MMP-2/9 inhibitor induced sensitization, in a dose dependent manner, to mechanical, hot and cold stimuli as measured by von Frey filaments, Hargreaves and acetone tests, respectively. Moreover, the protein levels of mature NGF (mNGF) were increased, whereas the levels and enzymatic activity of matrix metalloproteinase 9 were reduced in the glabrous skin of the hind paw. MMP-2/9 inhibition also led to a robust sprouting of sympathetic fibers into the upper dermis but there were no changes in the density of peptidergic nociceptive afferents. Conclusions These findings indicate that localized MMP-2/9 inhibition provokes a pattern of sensitization and fiber sprouting comparable to that previously obtained following CFA injection. Accordingly, the modulation of endogenous NGF levels should be considered as a potential therapeutic target for the management of inflammatory pain associated with arthritis. PMID:23889761

  8. Catalytic degradation of gaseous benzene by using TiO2/goethite immobilized on palygorskite: Preparation, characterization and mechanism

    NASA Astrophysics Data System (ADS)

    Ma, Jianzhong; Zhu, Chengzhu; Lu, Jun; Liu, Haibo; Huang, Li; Chen, Tianhu; Chen, Dong

    2015-11-01

    The nano-TiO2/goethite/palygorskite catalysts were prepared by sol-gel method. The morphology and structure of the catalysts were analyzed by X-ray diffraction (XRD), UV-Vis reflection spectrometer, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and N2 adsorption-desorption measurement. The results indicated that the self-made catalysts had excellent catalytic performance on gaseous benzene degradation. In the case of benzene concentration at 30 mg/m3, the degradation efficiency, over TiO2/goethite/palygorskite composite with mass ratio of 10:5:5, reached 70.4% after 180 min 254 nm UV irradiation. The reaction mechanism and kinetics study showed that palygorskite/goethite/TiO2 composites photocatalytic degradation benzene was mainly caused by oxidizing property of electron-holes and oxygen synergy effect.

  9. Harboring oil-degrading bacteria: a potential mechanism of adaptation and survival in corals inhabiting oil-contaminated reefs.

    PubMed

    Al-Dahash, Lulwa M; Mahmoud, Huda M

    2013-07-30

    Certain coral reef systems north of the Arabian Gulf are characterized by corals with a unique ability to thrive and flourish despite the presence of crude oil continuously seeping from natural cracks in the seabed. Harboring oil-degrading bacteria as a part of the holobiont has been investigated as a potential mechanism of adaptation and survival for corals in such systems. The use of conventional and molecular techniques verified a predominance of bacteria affiliated with Gammaproteobacteria, Actinobacteria and Firmicutes in the mucus and tissues of Acropora clathrata and Porites compressa. These bacteria were capable of degrading a wide range of aliphatic (C9-C28) aromatic hydrocarbons (Phenanthrene, Biphenyl, Naphthalene) and crude oil. In addition, microcosms supplied with coral samples and various concentrations of crude oil shifted their bacterial population toward the more advantageous types of oil degraders as oil concentrations increased. PMID:23014479

  10. Investigating Age-Related Changes in Fine Motor Control Across Different Effectors and the Impact of White Matter Integrity

    PubMed Central

    Holtrop, Joseph L.; Loucks, Torrey M; Sosnoff, Jacob J; Sutton, Bradley P

    2014-01-01

    Changes in fine motor control that eventually compromise dexterity accompany advanced age; however there is evidence that age-related decline in motor control may not be uniform across effectors. Particularly, the role of central mechanisms in effector-specific decline has not been examined but is relevant for placing age-related motor declines into the growing literature of age-related changes in brain function. We examined sub-maximal force control across three different effectors (fingers, lips, and tongue) in 18 young and 14 older adults. In parallel with the force variability measures we examined changes in white matter structural integrity in effector-specific pathways in the brain with diffusion tensor imaging (DTI). Motor pathways for each effector were identified by using an fMRI localizer task followed by tractography to identify the fiber tracts propagating to the midbrain. Increases in force control variability were found with age in all three effectors but the effectors showed different degrees of age-related variability. Motor control changes were accompanied by a decline in white matter structural integrity with age shown by measures of fractional anisotropy and radial diffusivity. The DTI metrics appear to mediate some of the age-related declines in motor control. Our findings indicate that the structural integrity of descending motor systems may play a significant role in age-related increases in motor performance variability, but that differential age-related declines in oral and manual effectors are not likely due to structural integrity of descending motor pathways in the brain. PMID:24657352

  11. Mechanism driven structural elucidation of forced degradation products from hydrocortisone in solution.

    PubMed

    Zhang, Fa; Zhou, Jay; Shi, Yiqun; Tavlarakis, Panagiotis; Karaisz, Kenneth

    2016-09-01

    Hydrocortisone degradation products 1, 2, 3, and 4 along with hemiacetal derivatives 5, 6, 7, and 8 were observed through stressed hydrocortisone in solution. Their structures were identified based on HPLC-UV, HPLC-MS, and HPLC-HRMS (high resolution/high accuracy mass spectrometry) analyses as well as reaction mechanistic investigation and synthesis for structural confirmation. 1 and 2 are a pair of E/Z isomers and they were generated through acid catalyzed tautomerization/dehydration of hydrocortisone. Incorporation of water to 1 and 2 resulted in the formation of 3. We also discovered new degradation product 4 which was converted from 3 by oxidation. The degradation products were synthesized by stressing hydrocortisone under the optimized conditions and their structures were characterized by NMR ((1)H/(13)C, COSY, HMBC, HSQC, NOESY) and HRMS analyses. The degradation pathway of hydrocortisone is postulated. PMID:27328360

  12. Atmospheric degradation mechanism of CF{sub 3}OCH{sub 3}

    SciTech Connect

    Christensen, L.K.; Wallington, T.J.; Guschin, A.; Hurley, M.D.

    1999-05-27

    Recognition of the adverse effect of chlorofluorocarbon (CFC) release into the atmosphere has led to an international effort to replace CFCs with environmentally acceptable alternatives. Hydrofluoroethers (HFEs) are a class of compounds which have been developed to replace CFCs in applications such as the cleaning of electronic equipment, heat transfer agents in refrigeration systems, and carrier fluids for lubricant deposition. HFEs are volatile compounds and are released into the atmosphere when used. CF{sub 3}OCH{sub 3} has not been used commercially but is one of the simplest fluoroethers and serves as a model compound for the group of fluorinated ethers. A smog chamber/FTIR technique was used to study the Cl atom initiated oxidation of CF{sub 3}OCH{sub 3} in 700 Torr of N{sub 2}/O{sub 2} at 296 K. Using relative rate techniques it was determined that {kappa}(Cl + CF{sub 3}OCH{sub 3}) = (1.4 {+-} 0.2) {times} 10{sup {minus}13} and {kappa}(Cl + CF{sub 3}OC(O)H) = (9.8 {+-} 1.2) {times} 10{sup {minus}15} cm{sup 3} molecule{sup {minus}1} s{sup {minus}1}. At 700 Torr of N{sub 2}/O{sub 2} diluent at 296 K reaction with O{sub 2} is the only loss mechanism of the CF{sub 3}OCH{sub 2}O{sup {sm_bullet}} radical. The infrared spectra of the peroxy nitrates CF{sub 3}OCH{sub 2}O{sub 2}NO{sub 2} and CF{sub 3}OC(O)O{sub 2}NO{sub 2} were recorded and compared to the nonfluorinated analogues CH{sub 3}OCH{sub 2}O{sub 2}NO{sub 2} and CH{sub 3}OC(O)O{sub 2}NO{sub 2}. The thermal decomposition rate of CF{sub 3}OC(O)NO{sub 2} is (2.3 {+-} 0.1) {times} 10{sup {minus}4} s{sup {minus}1} in 700 Torr of N{sub 2} at 295.8 K. The reaction of CF{sub 3}OC(O)O{sub 2} radicals with HO{sub 2} radicals gives CF{sub 3}OC(O)H in a yield of (80 {+-} 11)%. The results are discussed with respect to the atmospheric degradation mechanism of CF{sub 3}OCH{sub 3} and other ethers.

  13. Kinetic analysis of acid orange 7 degradation by pulsed discharge plasma combined with activated carbon and the synergistic mechanism exploration.

    PubMed

    Guo, He; Wang, Huijuan; Wu, Qiangshun; Zhou, Guangshun; Yi, Chengwu

    2016-09-01

    The synergistic technique of pulsed discharge plasma (PDP) and activated carbon (AC) was built to investigate the kinetics of acid orange 7 (AO7) degradation under different conditions of AC addition, electrode gap, initial pH value of solution, gas variety and gas flow rate. Emission spectra of OH and O, UV-vis absorption spectra of the AO7 solution and TOC removal were measured to illustrate the synergistic mechanism of the PDP and the AC. The obtained results indicated that the kinetic constant of AO7 degradation increased from 0.00947 min(-1) to 0.01419 min(-1) when 4 g AC was added into the PDP system; AO7 degradation was higher in the case of alkaline solution when oxygen was used as the flow gas in the PDP/AC system, 2 L/min oxygen flow was more favorable for the degradation. Results of the relative emission intensities of OH and O indicated the catalytic effect of the AC on the active species formation as well as the important role of the two radicals for the AO7 degradation. There was no new peaks appeared by the UV-vis analysis of the AO7 solution after 60 min treatment. The highest TOC removal in the PDP/AC system was 30.3%, which was achieved under the condition of 4 L/min air flow rate and 3 initial pH value. PMID:27295438

  14. Age-related differences in pulmonary effects of acute and subchronic episodic ozone exposures in Brown Norway rats

    EPA Science Inventory

    Ozone (O3) is known to induce adverse pulmonary and systemic health effects. Importantly, children and older persons are considered at-risk populations for O3-induced dysfunction, yet the mechanisms accounting for the age-related pulmonary responses to O3 are uncertain. In this s...

  15. Automatic age-related macular degeneration detection and staging

    NASA Astrophysics Data System (ADS)

    van Grinsven, Mark J. J. P.; Lechanteur, Yara T. E.; van de Ven, Johannes P. H.; van Ginneken, Bram; Theelen, Thomas; Sánchez, Clara I.

    2013-03-01

    Age-related macular degeneration (AMD) is a degenerative disorder of the central part of the retina, which mainly affects older people and leads to permanent loss of vision in advanced stages of the disease. AMD grading of non-advanced AMD patients allows risk assessment for the development of advanced AMD and enables timely treatment of patients, to prevent vision loss. AMD grading is currently performed manually on color fundus images, which is time consuming and expensive. In this paper, we propose a supervised classification method to distinguish patients at high risk to develop advanced AMD from low risk patients and provide an exact AMD stage determination. The method is based on the analysis of the number and size of drusen on color fundus images, as drusen are the early characteristics of AMD. An automatic drusen detection algorithm is used to detect all drusen. A weighted histogram of the detected drusen is constructed to summarize the drusen extension and size and fed into a random forest classifier in order to separate low risk from high risk patients and to allow exact AMD stage determination. Experiments showed that the proposed method achieved similar performance as human observers in distinguishing low risk from high risk AMD patients, obtaining areas under the Receiver Operating Characteristic curve of 0.929 and 0.934. A weighted kappa agreement of 0.641 and 0.622 versus two observers were obtained for AMD stage evaluation. Our method allows for quick and reliable AMD staging at low costs.

  16. Age-related thermal response: the cellular resilience of juveniles.

    PubMed

    Clark, M S; Thorne, M A S; Burns, G; Peck, L S

    2016-01-01

    Understanding species' responses to environmental challenges is key to predicting future biodiversity. However, there is currently little data on how developmental stages affect responses and also whether universal gene biomarkers to environmental stress can be identified both within and between species. Using the Antarctic clam, Laternula elliptica, as a model species, we examined both the tissue-specific and age-related (juvenile versus mature adult) gene expression response to acute non-lethal warming (12 h at 3 °C). In general, there was a relatively muted response to this sub-lethal thermal challenge when the expression profiles of treated animals, of either age, were compared with those of 0 °C controls, with none of the "classical" stress response genes up-regulated. The expression profiles were very variable between the tissues of all animals, irrespective of age with no single transcript emerging as a universal biomarker of thermal stress. However, when the expression profiles of treated animals of the different age groups were directly compared, a very different pattern emerged. The profiles of the younger animals showed significant up-regulation of chaperone and antioxidant transcripts when compared with those of the older animals. Thus, the younger animals showed evidence of a more robust cellular response to warming. These data substantiate previous physiological analyses showing a more resilient juvenile population. PMID:26364303

  17. Ocular Surface Temperature in Age-Related Macular Degeneration

    PubMed Central

    Sodi, Andrea; Giacomelli, Giovanni; Corvi, Andrea; Menchini, Ugo

    2014-01-01

    Background. The aim of this study is to investigate the ocular thermographic profiles in age-related macular degeneration (AMD) eyes and age-matched controls to detect possible hemodynamic abnormalities, which could be involved in the pathogenesis of the disease. Methods. 32 eyes with early AMD, 37 eyes with atrophic AMD, 30 eyes affected by untreated neovascular AMD, and 43 eyes with fibrotic AMD were included. The control group consisted of 44 healthy eyes. Exclusion criteria were represented by any other ocular diseases other than AMD, tear film abnormalities, systemic cardiovascular abnormalities, diabetes mellitus, and a body temperature higher than 37.5°C. A total of 186 eyes without pupil dilation were investigated by infrared thermography (FLIR A320). The ocular surface temperature (OST) of three ocular points was calculated by means of an image processing technique from the infrared images. Two-sample t-test and one-way analysis of variance (ANOVA) test were used for statistical analyses. Results. ANOVA analyses showed no significant differences among AMD groups (P value >0.272). OST in AMD patients was significantly lower than in controls (P > 0.05). Conclusions. Considering the possible relationship between ocular blood flow and OST, these findings might support the central role of ischemia in the pathogenesis of AMD. PMID:25436140

  18. Age-Related Macular Degeneration: A Scientometric Analysis

    PubMed Central

    Ramin, Shahrokh; Soheilian, Masoud; Habibi, Gholamreza; Ghazavi, Roghayeh; Gharebaghi, Reza; Heidary, Fatemeh

    2015-01-01

    Age-related macular degeneration (ARMD) is a major cause of central blindness among working aged adults across the world. Systematic research planning on any subject, including ARMD is in need of solid data regarding previous efforts in this field and to identify the gaps in the research. This study aimed to elucidate the most important trends, directions, and gap in this subject. The data extracted from the Institute for Scientific Information were used to perform a bibliometric analysis of the scientific productions (1993–2013) about ARMD. Specific parameters related to ARMD were analyzed to obtain a view of the topic’s structure, history, and document relationships. Additionally, the trends and authors in the most influential publications were analyzed. The number of articles in this field was found constantly increasing. Most highly cited articles addressed genetic epidemiology and clinical research topics in this field. During the past 3 years, there has been a trend toward biomarker research. Through performing the first scientometric survey on ARMD research, we analyzed the characteristics of papers and the trends in scientific production. We also identified some of the critical gaps in the current research efforts that would help in large-scale research strategic planning. PMID:26060829

  19. Mathematical morphologic analysis of aging-related epidermal changes.

    PubMed

    Moragas, A; Castells, C; Sans, M

    1993-04-01

    Fractographic techniques based on mathematical morphology were used to study aging-related epidermal changes in abdominal skin samples obtained from 96 autopsy cases. Three linear roughness indices were evaluated for the rete peg profile and the shrinkage effect on the basal layer and interface between the granular and horny layers. Elderly subjects had a 36.3% decrease in rete peg-related roughness index when compared with younger subjects. This roughness index has been corrected, with shrinkage due to skin elasticity taken into account. For females, fitting of a logistic decay function yielded a curve with right and left asymptotes and a steeper descent between 40 and 60 years. Half value time--i.e., the time when half rete peg profile flattening occurred--was 46.8 years. In contrast, males showed almost monotonical decay. Epidermal thickness measured between rete pegs showed the same exponential decline for both sexes, with values from 22.6 to 11.4 microns. Skin shrinkage in elderly subjects decreased 22% in superficial layers and only 6% in the lower epidermis. In both cases shrinkage had a linear relation with age, and no sex differences were found. PMID:8318130

  20. Seven New Loci Associated with Age-Related Macular Degeneration

    PubMed Central

    2013-01-01

    Age-related macular degeneration (AMD) is a common cause of blindness in older individuals. To accelerate understanding of AMD biology and help design new therapies, we executed a collaborative genomewide association study, examining >17,100 advanced AMD cases and >60,000 controls of European and Asian ancestry. We identified 19 genomic loci associated with AMD with p<5×10−8 and enriched for genes involved in regulation of complement activity, lipid metabolism, extracellular matrix remodeling and angiogenesis. Our results include 7 loci reaching p<5×10−8 for the first time, near the genes COL8A1/FILIP1L, IER3/DDR1, SLC16A8, TGFBR1, RAD51B, ADAMTS9/MIR548A2, and B3GALTL. A genetic risk score combining SNPs from all loci displayed similar good ability to distinguish cases and controls in all samples examined. Our findings provide new directions for biological, genetic and therapeutic studies of AMD. PMID:23455636