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Sample records for aetiological mechanisms underlying

  1. Role of Gut Microbiota in the Aetiology of Obesity: Proposed Mechanisms and Review of the Literature

    Directory of Open Access Journals (Sweden)

    Muhammad Jaffar Khan

    2016-01-01

    Full Text Available The aetiology of obesity has been attributed to several factors (environmental, dietary, lifestyle, host, and genetic factors; however none of these fully explain the increase in the prevalence of obesity worldwide. Gut microbiota located at the interface of host and environment in the gut are a new area of research being explored to explain the excess accumulation of energy in obese individuals and may be a potential target for therapeutic manipulation to reduce host energy storage. Several mechanisms have been suggested to explain the role of gut microbiota in the aetiology of obesity such as short chain fatty acid production, stimulation of hormones, chronic low-grade inflammation, lipoprotein and bile acid metabolism, and increased endocannabinoid receptor system tone. However, evidence from animal and human studies clearly indicates controversies in determining the cause or effect relationship between the gut microbiota and obesity. Metagenomics based studies indicate that functionality rather than the composition of gut microbiota may be important. Further mechanistic studies controlling for environmental and epigenetic factors are therefore required to help unravel obesity pathogenesis.

  2. Role of Gut Microbiota in the Aetiology of Obesity: Proposed Mechanisms and Review of the Literature

    Science.gov (United States)

    Gerasimidis, Konstantinos; Edwards, Christine Ann; Shaikh, M. Guftar

    2016-01-01

    The aetiology of obesity has been attributed to several factors (environmental, dietary, lifestyle, host, and genetic factors); however none of these fully explain the increase in the prevalence of obesity worldwide. Gut microbiota located at the interface of host and environment in the gut are a new area of research being explored to explain the excess accumulation of energy in obese individuals and may be a potential target for therapeutic manipulation to reduce host energy storage. Several mechanisms have been suggested to explain the role of gut microbiota in the aetiology of obesity such as short chain fatty acid production, stimulation of hormones, chronic low-grade inflammation, lipoprotein and bile acid metabolism, and increased endocannabinoid receptor system tone. However, evidence from animal and human studies clearly indicates controversies in determining the cause or effect relationship between the gut microbiota and obesity. Metagenomics based studies indicate that functionality rather than the composition of gut microbiota may be important. Further mechanistic studies controlling for environmental and epigenetic factors are therefore required to help unravel obesity pathogenesis. PMID:27703805

  3. Riskfactors and underlying mechanisms

    OpenAIRE

    Bockers, Estelle Simone

    2015-01-01

    Childhood interpersonal traumatizations increase the risk for revictimizations as well as for psychological disorders like the posttraumatic stress disorder (PTSD). Different variables and mechanisms underlying revictimization are discussed in current literature. However, empiri-cal data on revictimization is poor and inconsistant. Guilt and shame following traumatic events are considered as risk factors for the development and persistence of PTSD. PTSD is frequently associated with trauma-re...

  4. Biochemical mechanisms underlying atherogenesis

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    Dr.P.V.L.N. Srinivasa Rao

    2012-02-01

    Full Text Available Atherosclerosis remains one of the major causes of death and premature disability in developed countries. Though atherosclerosis was formerly considered a bland lipid storage disease, substantial advances in basic and experimental sciences have illuminated the role of endothelium, inflammation and immune mechanisms in its pathogenesis. Current concept of atherosclerosis is that of a dynamic and progressive disease arising from in- jury to endothelium, also known as endothelial dysfunction and an inflammatory response to that injury. The lesions of atherosclerosis occur principally in large and medium sized arteries. Atherosclerosis affects various regions of the circulation preferentially and can lead to ischemia of heart, brain or extremities resulting in in- farction.This produces distinct clinical manifestations depending on the vessel involved. Several predisposing factors to cardiovascular diseases such as diabetes mellitus, hypertension, obesity, infections act as triggers to the devel- opment of atherosclerosis by causing endothelial dysfunction and/or promoting inflammatory response. The evolution of pathogenetic mechanisms has passed through various directions such as oxidative stress, inflam- mation and immune responses. It is now known that all these are not acting independently but are interrelated and getting unified in the current concept of atherogenesis. The following discussion aims at providing an in- sight into these developments which can help in a better comprehension of the disease and management of its clinical complications

  5. Aetiological role of common respiratory viruses in acute lower respiratory infections in children under five years: A systematic review and meta–analysis

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    Ting Shi

    2015-06-01

    Full Text Available Background: Acute lower respiratory infection (ALRI remains a major cause of childhood hospitalization and mortality in young children and the causal attribution of respiratory viruses in the aetiology of ALRI is unclear. We aimed to quantify the absolute effects of these viral exposures. Methods: We conducted a systematic literature review (across 7 databases of case–control studies published from 1990 to 2014 which investigated the viral profile of 18592 children under 5 years with and without ALRI. We then computed a pooled odds ratio and virus–specific attributable fraction among the exposed of 8 common viruses – respiratory syncytial virus (RSV, influenza (IFV, parainfluenza (PIV, human metapneumovirus (MPV, adenovirus (AdV, rhinovirus (RV, bocavirus (BoV, and coronavirus (CoV. Findings: From the 23 studies included, there was strong evidence for causal attribution of RSV (OR 9.79; AFE 90%, IFV (OR 5.10; AFE 80%, PIV (OR 3.37; AFE 70% and MPV (OR 3.76; AFE 73%, and less strong evidence for RV (OR 1.43; AFE 30% in young children presenting with ALRI compared to those without respiratory symptoms (asymptomatic or healthy children. However, there was no significant difference in the detection of AdV, BoV, or CoV in cases and controls. Conclusions This review supports RSV, IFV, PIV, MPV and RV as important causes of ALRI in young children, and provides quantitative estimates of the absolute proportion of virus–associated ALRI cases to which a viral cause can be attributed.

  6. Kinesin's backsteps under mechanical load

    CERN Document Server

    Hyeon, Changbong; Onuchic, Jose' N

    2009-01-01

    Kinesins move processively toward the plus end of microtubules by hydrolyzing ATP for each step. From an enzymatic perspective, the mechanism of mechanical motion coupled to the nucleotide chemistry is often well explained using a single-loop cyclic reaction. However, several difficulties arise in interpreting kinesin's backstepping within this framework, especially when external forces oppose the motion of kinesin. We review evidence, such as an ATP-independent stall force and a slower cycle time for backsteps, that has emerged to challenge the idea that kinesin backstepping is due to ATP synthesis, i.e., the reverse cycle of kinesin's forward-stepping chemomechanics. Supplementing the conventional single-loop chemomechanics with routes for ATP-hydrolyzing backward steps and nucleotide-free steps, especially under load, gives a better physical interpretation of the experimental data on backsteps.

  7. Abnormal fetal head shape: aetiology and management

    DEFF Research Database (Denmark)

    Petersen, Olav Bjørn; David, Anna; Thomasson, Louise;

    2007-01-01

    Background: Abnormal head shape is an uncommon finding on prenatal ultrasound, often associated with breech presentation, spinabifida, aneuploidy or secondary to oligohydramnios or fetal position. Other aetiologies are rarer and may be more difficult to define. Objective: To determine the aetiology...... (lemon-shaped), 18.4% with aneuploidy (mostly strawberry-shaped). 19.5% were dolicocephalic, most secondary to fetal position or oligohydramnios (see table). 13 had confirmed craniosynostosis, including thanatophoric dysplasia, Craniofrontonasal dysplasia, Aperts syndrome, Baller-Gerold syndrome, I......-cell disease, Muenke craniosynostosis and two with an as yet undefined craniosynostosis syndrome. Overall, 16.5 % had an underlying genetic syndrome. Conclusions: Abnormal fetal head shape may be a normal variant, but is commonly associated with a wide variety of underlying pathologies. In view of the high...

  8. The aetiology of deep venous thrombosis.

    Science.gov (United States)

    Malone, P C; Agutter, P S

    2006-09-01

    Most ideas about the pathogenesis of deep venous thrombosis (DVT) are dominated by a 'consensus model' first articulated around 1962. This model invokes 'Virchow's triad' and attributes thrombogenesis in veins to some combination of 'hypercoagulability', 'stasis' and 'intimal injury'. This arose as a by-product of studies on the mechanisms of haemostasis and bleeding diatheses that were at best only indirectly relevant to thrombosis, and there are reasons for doubting the causal significance of 'hypercoagulability' and 'stasis' in the aetiology of DVT. Proponents of the consensus model make little reference to a substantial literature, mostly historical, that: (a) emphasizes the significance of the venous valve pockets (VVP) and blood rheology in DVT pathogenesis; and (b) describes morphological features specific to venous thrombi that a valid aetiological model must explain. This literature provides the basis for an alternative hypothesis of DVT aetiology, published some 30 years ago, which has been experimentally corroborated and is compatible with recent cell and molecular biological studies of the venous endothelium. We review this alternative hypothesis, considering its potential value for future research on DVT and embolism, and its significance for clinical practice.

  9. Neural mechanisms underlying breathing complexity.

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    Agathe Hess

    Full Text Available Breathing is maintained and controlled by a network of automatic neurons in the brainstem that generate respiratory rhythm and receive regulatory inputs. Breathing complexity therefore arises from respiratory central pattern generators modulated by peripheral and supra-spinal inputs. Very little is known on the brainstem neural substrates underlying breathing complexity in humans. We used both experimental and theoretical approaches to decipher these mechanisms in healthy humans and patients with chronic obstructive pulmonary disease (COPD. COPD is the most frequent chronic lung disease in the general population mainly due to tobacco smoke. In patients, airflow obstruction associated with hyperinflation and respiratory muscles weakness are key factors contributing to load-capacity imbalance and hence increased respiratory drive. Unexpectedly, we found that the patients breathed with a higher level of complexity during inspiration and expiration than controls. Using functional magnetic resonance imaging (fMRI, we scanned the brain of the participants to analyze the activity of two small regions involved in respiratory rhythmogenesis, the rostral ventro-lateral (VL medulla (pre-Bötzinger complex and the caudal VL pons (parafacial group. fMRI revealed in controls higher activity of the VL medulla suggesting active inspiration, while in patients higher activity of the VL pons suggesting active expiration. COPD patients reactivate the parafacial to sustain ventilation. These findings may be involved in the onset of respiratory failure when the neural network becomes overwhelmed by respiratory overload We show that central neural activity correlates with airflow complexity in healthy subjects and COPD patients, at rest and during inspiratory loading. We finally used a theoretical approach of respiratory rhythmogenesis that reproduces the kernel activity of neurons involved in the automatic breathing. The model reveals how a chaotic activity in

  10. Pyrexia: aetiology in the ICU.

    Science.gov (United States)

    Niven, Daniel J; Laupland, Kevin B

    2016-01-01

    Elevation in core body temperature is one of the most frequently detected abnormal signs in patients admitted to adult ICUs, and is associated with increased mortality in select populations of critically ill patients. The definition of an elevated body temperature varies considerably by population and thermometer, and is commonly defined by a temperature of 38.0 °C or greater. Terms such as hyperthermia, pyrexia, and fever are often used interchangeably. However, strictly speaking hyperthermia refers to the elevation in body temperature that occurs without an increase in the hypothalamic set point, such as in response to specific environmental (e.g., heat stroke), pharmacologic (e.g., neuroleptic malignant syndrome), or endocrine (e.g., thyrotoxicosis) stimuli. On the other hand, pyrexia and fever refer to the classical increase in body temperature that occurs in response to a vast list of infectious and noninfectious aetiologies in association with an increase in the hypothalamic set point. In this review, we examine the contemporary literature investigating the incidence and aetiology of pyrexia and hyperthermia among medical and surgical patients admitted to adult ICUs with or without an acute neurological condition. A temperature greater than 41.0 °C, although occasionally observed among patients with infectious or noninfectious pyrexia, is more commonly observed in patients with hyperthermia. Most episodes of pyrexia are due to infections, but incidence estimates of infectious and noninfectious aetiologies are limited by studies with small sample size and inconsistent reporting of noninfectious aetiologies. Pyrexia commonly triggers a full septic work-up, but on its own is a poor predictor of culture-positivity. In order to improve culturing practices, and better guide the diagnostic approach to critically ill patients with pyrexia, additional research is required to provide more robust estimates of the incidence of infectious and noninfectious aetiologies

  11. Molecular Mechanisms Underlying Pituitary Pathogenesis.

    Science.gov (United States)

    Sapochnik, Melanie; Nieto, Leandro Eduardo; Fuertes, Mariana; Arzt, Eduardo

    2016-04-01

    During the last years, progress has been made on the identification of mechanisms involved in anterior pituitary cell transformation and tumorigenesis. Oncogene activation, tumor suppressor gene inactivation, epigenetic changes, and microRNAs deregulation contribute to the initiation of pituitary tumors. Despite the high prevalence of pituitary adenomas, they are mostly benign, indicating that intrinsic mechanisms may regulate pituitary cell expansion. Senescence is characterized by an irreversible cell cycle arrest and represents an important protective mechanism against malignancy. Pituitary tumor transforming gene (PTTG) is an oncogene involved in early stages of pituitary tumor development, and also triggers a senescence response by activating DNA-damage signaling pathway. Cytokines, as well as many other factors, play an important role in pituitary physiology, affecting not only cell proliferation but also hormone secretion. Special interest is focused on interleukin-6 (IL-6) because its dual function of stimulating pituitary tumor cell growth but inhibiting normal pituitary cells proliferation. It has been demonstrated that IL-6 has a key role in promoting and maintenance of the senescence program in tumors. Senescence, triggered by PTTG activation and mediated by IL-6, may be a mechanism for explaining the benign nature of pituitary tumors. PMID:26718581

  12. [The neural mechanisms underlying swallowing].

    Science.gov (United States)

    Inoue, Makoto

    2015-02-01

    Swallowing is regarded as the first step in nutrition; it transports food boluses and liquid from the mouth to the stomach and is a defensive response to prevent aspiration. Swallowing movements are produced by a central pattern generator (CPG) located in the lower brainstem. The swallowing CPG includes two main groups of neurons: one is located within the nucleus tractus solitarii and contains the generator neurons involved in triggering, shaping, and timing the sequential or rhythmic swallowing pattern and the other is located in the ventrolateral medulla and contains switching neurons that distribute the swallowing drive to various pools of related motoneurons. Swallowing movements can be triggered by either central inputs or peripheral inputs from pharyngeal and laryngeal regions, but the precise neural mechanisms of the swallowing CPG remain to be fully elucidated. This review discusses the fundamental knowledge of ingestion behaviors, with a focus on swallowing.

  13. Metacognitive mechanisms underlying lucid dreaming.

    Science.gov (United States)

    Filevich, Elisa; Dresler, Martin; Brick, Timothy R; Kühn, Simone

    2015-01-21

    Lucid dreaming is a state of awareness that one is dreaming, without leaving the sleep state. Dream reports show that self-reflection and volitional control are more pronounced in lucid compared with nonlucid dreams. Mostly on these grounds, lucid dreaming has been associated with metacognition. However, the link to lucid dreaming at the neural level has not yet been explored. We sought for relationships between the neural correlates of lucid dreaming and thought monitoring. Human participants completed a questionnaire assessing lucid dreaming ability, and underwent structural and functional MRI. We split participants based on their reported dream lucidity. Participants in the high-lucidity group showed greater gray matter volume in the frontopolar cortex (BA9/10) compared with those in the low-lucidity group. Further, differences in brain structure were mirrored by differences in brain function. The BA9/10 regions identified through structural analyses showed increases in blood oxygen level-dependent signal during thought monitoring in both groups, and more strongly in the high-lucidity group. Our results reveal shared neural systems between lucid dreaming and metacognitive function, in particular in the domain of thought monitoring. This finding contributes to our understanding of the mechanisms enabling higher-order consciousness in dreams.

  14. Molecular Mechanisms Underlying Hepatocellular Carcinoma

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    Christian Trepo

    2009-11-01

    Full Text Available Hepatocarcinogenesis is a complex process that remains still partly understood. That might be explained by the multiplicity of etiologic factors, the genetic/epigenetic heterogeneity of tumors bulks and the ignorance of the liver cell types that give rise to tumorigenic cells that have stem cell-like properties. The DNA stress induced by hepatocyte turnover, inflammation and maybe early oncogenic pathway activation and sometimes viral factors, leads to DNA damage response which activates the key tumor suppressive checkpoints p53/p21Cip1 and p16INK4a/pRb responsible of cell cycle arrest and cellular senescence as reflected by the cirrhosis stage. Still obscure mechanisms, but maybe involving the Wnt signaling and Twist proteins, would allow pre-senescent hepatocytes to bypass senescence, acquire immortality by telomerase reactivation and get the last genetic/epigenetic hits necessary for cancerous transformation. Among some of the oncogenic pathways that might play key driving roles in hepatocarcinogenesis, c-myc and the Wnt/β-catenin signaling seem of particular interest. Finally, antiproliferative and apoptosis deficiencies involving TGF-β, Akt/PTEN, IGF2 pathways for instance are prerequisite for cancerous transformation. Of evidence, not only the transformed liver cell per se but the facilitating microenvironment is of fundamental importance for tumor bulk growth and metastasis.

  15. Metacognitive mechanisms underlying lucid dreaming.

    Science.gov (United States)

    Filevich, Elisa; Dresler, Martin; Brick, Timothy R; Kühn, Simone

    2015-01-21

    Lucid dreaming is a state of awareness that one is dreaming, without leaving the sleep state. Dream reports show that self-reflection and volitional control are more pronounced in lucid compared with nonlucid dreams. Mostly on these grounds, lucid dreaming has been associated with metacognition. However, the link to lucid dreaming at the neural level has not yet been explored. We sought for relationships between the neural correlates of lucid dreaming and thought monitoring. Human participants completed a questionnaire assessing lucid dreaming ability, and underwent structural and functional MRI. We split participants based on their reported dream lucidity. Participants in the high-lucidity group showed greater gray matter volume in the frontopolar cortex (BA9/10) compared with those in the low-lucidity group. Further, differences in brain structure were mirrored by differences in brain function. The BA9/10 regions identified through structural analyses showed increases in blood oxygen level-dependent signal during thought monitoring in both groups, and more strongly in the high-lucidity group. Our results reveal shared neural systems between lucid dreaming and metacognitive function, in particular in the domain of thought monitoring. This finding contributes to our understanding of the mechanisms enabling higher-order consciousness in dreams. PMID:25609624

  16. Traumatic Tympanic Membrane perforation: An aetiological profile

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    Alabi Biodun S

    2009-11-01

    Full Text Available Abstract Background Traumatic perforation of the tympanic membrane may be due to direct or indirect source. The aim of the study is to profile the various aetiologies of traumatic tympanic membrane perforation in Ilorin, north central Nigeria. A retrospective review of 64 patients seen at the University of Ilorin Teaching hospital, Ilorin, Nigeria over a ten year period (January 1998 to Dec 2007 with history of traumatic tympanic membrane perforation from various causes, these also included multiply injured patients with bleeding from middle ear as part of their presentations. The data retrieved included the biodata, the clinical presentations, source of injury, the clinical findings and the treatment outcome. The data were entered into an SPSS version 11 computer soft ware and analyzed descriptively. Findings Sixty four (64 ears were analysed, Age range 6 months to 50 yrs, mean age of 29.2 yrs 7.9% of them were ≤5 years, 29.7% between 21-34 years, and 37.7% were 35 years and above. The male to female ratio was 2.5:1.0. Commonest aetiology was from slaps, then road traffic injury (RTI in 35.9% and 23.5%, Majority of the slap injury were from fights (30.5%, security agents, senior students and cultists at schools (17.4% each. Sudden hearing loss was a typical presentation (95.3%, majority of the patient defaulted from follow up once the symptoms of bleeding and pain subsided. Only 7.8% had neomembrane formation on follow up Conclusion Traumatic perforation of the tympanic membrane is an uncommon injury that is under-reported, there is the need to educate on alternative punitive measure among students and security agents, unskilled removal of foreign body, early identification, evaluation and referral of patients reduces the attendant morbidity.

  17. Mechanisms underlying the portion-size effect.

    Science.gov (United States)

    Peter Herman, C; Polivy, Janet; Pliner, Patricia; Vartanian, Lenny R

    2015-05-15

    The portion-size effect (PSE) refers to the fact that people eat more when served larger portions. This effect is neither obvious nor artifactual. We examine the prevailing explanations (or underlying mechanisms) that have been offered for the PSE. The dominant candidate mechanism is "appropriateness"; that is, people accept the portion that they are served as being of an appropriate size and eat accordingly. Because people do not necessarily finish the portion that they are served, variations on the basic appropriateness mechanism have been suggested. We also consider some evidence that is inconsistent with an appropriateness explanation, including the appearance of the PSE in children as young as two years of age. We also examine other mechanisms that do not rely on appropriateness norms. Visual food cues may assist in assessing appropriateness but may also drive food intake in a more mindless fashion. Larger portions induce larger bites, which may increase intake by reducing oral exposure time and sensory-specific satiety. We consider further research questions that could help to clarify the mechanisms underlying the PSE. PMID:25802021

  18. Mechanical characteristics and microcosmic mechanisms of granite under temperature loads

    Institute of Scientific and Technical Information of China (English)

    XU Xiao-li; GAO Feng; SHEN Xiao-ming; XIE He-ping

    2008-01-01

    The relationships between mechanical characteristics of rock and microcosmic mechanism at high temperatures were investigated by MTS815, as well as the stress-strain behavior of granite under the action of temperatures ranging from room tem-perature to 1200 ℃. Based on a micropore structure analyzer and SEM, the changes in rock porosity and micro'structural mor-phology of sample fractures and brittle-plastic characteristics under high temperatures were analyzed. The results are as follows: 1) Mechanical characteristics do not show obvious variations before 800 ℃; strength decreases suddenly after 800 ℃ and bearing capacity is almost lost at 1200 ℃. 2) Rock porosity increases with rising temperatures; the threshold temperature is about 800 ℃;at this temperature its effect is basically uniform with strength decreasing rapidly. 3) The failure type of granite is a brittle tensile fracture at temperatures below 800 ℃ which transforms into plasticity at temperatures higher than 800 ℃ and crystal formation takes place at this time. Chemical reactions take place at 1200 ℃. Failure of granite under high temperature is a common result of thermal stress as indicated by an increase in the thermal expansion coefficient, transformation to crystal formation of minerals and structural chemical reactions.

  19. DNA under Force: Mechanics, Electrostatics, and Hydration

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    Jingqiang Li

    2015-02-01

    Full Text Available Quantifying the basic intra- and inter-molecular forces of DNA has helped us to better understand and further predict the behavior of DNA. Single molecule technique elucidates the mechanics of DNA under applied external forces, sometimes under extreme forces. On the other hand, ensemble studies of DNA molecular force allow us to extend our understanding of DNA molecules under other forces such as electrostatic and hydration forces. Using a variety of techniques, we can have a comprehensive understanding of DNA molecular forces, which is crucial in unraveling the complex DNA functions in living cells as well as in designing a system that utilizes the unique properties of DNA in nanotechnology.

  20. An Underlying Geometrical Manifold for Hamiltonian Mechanics

    CERN Document Server

    Horwitz, L P; Levitan, J; Lewkowicz, M

    2015-01-01

    We show that there exists an underlying manifold with a conformal metric and compatible connection form, and a metric type Hamiltonian (which we call the geometrical picture) that can be put into correspondence with the usual Hamilton-Lagrange mechanics. The requirement of dynamical equivalence of the two types of Hamiltonians, that the momenta generated by the two pictures be equal for all times, is sufficient to determine an expansion of the conformal factor, defined on the geometrical coordinate representation, in its domain of analyticity with coefficients to all orders determined by functions of the potential of the Hamilton-Lagrange picture, defined on the Hamilton-Lagrange coordinate representation, and its derivatives. Conversely, if the conformal function is known, the potential of a Hamilton-Lagrange picture can be determined in a similar way. We show that arbitrary local variations of the orbits in the Hamilton-Lagrange picture can be generated by variations along geodesics in the geometrical pictu...

  1. Evolved Mechanisms Versus Underlying Conditional Relations

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    Astorga Miguel López

    2015-03-01

    Full Text Available The social contracts theory claims that, in social exchange circumstances, human reasoning is not necessarily led by logic, but by certain evolved mental mechanisms that are useful for catching offenders. An emblematic experiment carried out with the intention to prove this thesis is the first experiment described by Fiddick, Cosmides, and Tooby in their paper of 2000. Lopez Astorga has questioned that experiment claiming that its results depend on an underlying conditional logical form not taken into account by Fiddick, Cosmides, and Tooby. In this paper, I propose an explanation alternative to that of Lopez Astorga, which does not depend on logical forms and is based on the mental models theory. Thus, I conclude that this other alternative explanation is one more proof that the experiment in question does not demonstrate the fundamental thesis of the social contracts theory.

  2. Mechanisms underlying UV-induced immune suppression

    Energy Technology Data Exchange (ETDEWEB)

    Ullrich, Stephen E. [Department of Immunology, University of Texas, MD Anderson Cancer Center, South Campus Research Building 1, 7455 Fannin St., P.O. Box 301402, Houston, TX 77030-1903 (United States)]. E-mail: sullrich@mdanderson.org

    2005-04-01

    Skin cancer is the most prevalent form of human neoplasia. Estimates suggest that in excess of one million new cases of skin cancer will be diagnosed this year alone in the United States (www.cancer.org/statistics). Fortunately, because of their highly visible location, skin cancers are more rapidly diagnosed and more easily treated than other types of cancer. Be that as it may, approximately 10,000 Americans a year die from skin cancer. The cost of treating non-melanoma skin cancer is estimated to be in excess of US$ 650 million a year [J.G. Chen, A.B. Fleischer, E.D. Smith, C. Kancler, N.D. Goldman, P.M. Williford, S.R. Feldman, Cost of non-melanoma skin cancer treatment in the United States, Dermatol. Surg. 27 (2001) 1035-1038], and when melanoma is included, the estimated cost of treating skin cancer in the United States is estimated to rise to US$ 2.9 billion annually (www.cancer.org/statistics). Because the morbidity and mortality associated with skin cancer is a major public health problem, it is important to understand the mechanisms underlying skin cancer development. The primary cause of skin cancer is the ultraviolet (UV) radiation found in sunlight. In addition to its carcinogenic potential, UV radiation is also immune suppressive. In fact, data from studies with both experimental animals and biopsy proven skin cancer patients suggest that there is an association between the immune suppressive effects of UV radiation and its carcinogenic potential. The focus of this manuscript will be to review the mechanisms underlying the induction of immune suppression following UV exposure. Particular attention will be directed to the role of soluble mediators in activating immune suppression.

  3. Two distinct neural mechanisms underlying indirect reciprocity.

    Science.gov (United States)

    Watanabe, Takamitsu; Takezawa, Masanori; Nakawake, Yo; Kunimatsu, Akira; Yamasue, Hidenori; Nakamura, Mitsuhiro; Miyashita, Yasushi; Masuda, Naoki

    2014-03-18

    Cooperation is a hallmark of human society. Humans often cooperate with strangers even if they will not meet each other again. This so-called indirect reciprocity enables large-scale cooperation among nonkin and can occur based on a reputation mechanism or as a succession of pay-it-forward behavior. Here, we provide the functional and anatomical neural evidence for two distinct mechanisms governing the two types of indirect reciprocity. Cooperation occurring as reputation-based reciprocity specifically recruited the precuneus, a region associated with self-centered cognition. During such cooperative behavior, the precuneus was functionally connected with the caudate, a region linking rewards to behavior. Furthermore, the precuneus of a cooperative subject had a strong resting-state functional connectivity (rsFC) with the caudate and a large gray matter volume. In contrast, pay-it-forward reciprocity recruited the anterior insula (AI), a brain region associated with affective empathy. The AI was functionally connected with the caudate during cooperation occurring as pay-it-forward reciprocity, and its gray matter volume and rsFC with the caudate predicted the tendency of such cooperation. The revealed difference is consistent with the existing results of evolutionary game theory: although reputation-based indirect reciprocity robustly evolves as a self-interested behavior in theory, pay-it-forward indirect reciprocity does not on its own. The present study provides neural mechanisms underlying indirect reciprocity and suggests that pay-it-forward reciprocity may not occur as myopic profit maximization but elicit emotional rewards.

  4. Two distinct neural mechanisms underlying indirect reciprocity.

    Science.gov (United States)

    Watanabe, Takamitsu; Takezawa, Masanori; Nakawake, Yo; Kunimatsu, Akira; Yamasue, Hidenori; Nakamura, Mitsuhiro; Miyashita, Yasushi; Masuda, Naoki

    2014-03-18

    Cooperation is a hallmark of human society. Humans often cooperate with strangers even if they will not meet each other again. This so-called indirect reciprocity enables large-scale cooperation among nonkin and can occur based on a reputation mechanism or as a succession of pay-it-forward behavior. Here, we provide the functional and anatomical neural evidence for two distinct mechanisms governing the two types of indirect reciprocity. Cooperation occurring as reputation-based reciprocity specifically recruited the precuneus, a region associated with self-centered cognition. During such cooperative behavior, the precuneus was functionally connected with the caudate, a region linking rewards to behavior. Furthermore, the precuneus of a cooperative subject had a strong resting-state functional connectivity (rsFC) with the caudate and a large gray matter volume. In contrast, pay-it-forward reciprocity recruited the anterior insula (AI), a brain region associated with affective empathy. The AI was functionally connected with the caudate during cooperation occurring as pay-it-forward reciprocity, and its gray matter volume and rsFC with the caudate predicted the tendency of such cooperation. The revealed difference is consistent with the existing results of evolutionary game theory: although reputation-based indirect reciprocity robustly evolves as a self-interested behavior in theory, pay-it-forward indirect reciprocity does not on its own. The present study provides neural mechanisms underlying indirect reciprocity and suggests that pay-it-forward reciprocity may not occur as myopic profit maximization but elicit emotional rewards. PMID:24591599

  5. Vascular Adventitia Calcification and Its Underlying Mechanism.

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    Na Li

    Full Text Available Previous research on vascular calcification has mainly focused on the vascular intima and media. However, we show here that vascular calcification may also occur in the adventitia. The purpose of this work is to help elucidate the pathogenic mechanisms underlying vascular calcification. The calcified lesions were examined by Von Kossa staining in ApoE-/- mice which were fed high fat diets (HFD for 48 weeks and human subjects aged 60 years and older that had died of coronary heart disease, heart failure or acute renal failure. Explant cultured fibroblasts and smooth muscle cells (SMCswere obtained from rat adventitia and media, respectively. After calcification induction, cells were collected for Alizarin Red S staining. Calcified lesions were observed in the aorta adventitia and coronary artery adventitia of ApoE-/-mice, as well as in the aorta adventitia of human subjects examined. Explant culture of fibroblasts, the primary cell type comprising the adventitia, was successfully induced for calcification after incubation with TGF-β1 (20 ng/ml + mineralization media for 4 days, and the phenotype conversion vascular adventitia fibroblasts into myofibroblasts was identified. Culture of SMCs, which comprise only a small percentage of all cells in the adventitia, in calcifying medium for 14 days resulted in significant calcification.Vascular calcification can occur in the adventitia. Adventitia calcification may arise from the fibroblasts which were transformed into myofibroblasts or smooth muscle cells.

  6. Molecular Mechanisms Underlying Psychological Stress and Cancer.

    Science.gov (United States)

    Shin, Kyeong Jin; Lee, Yu Jin; Yang, Yong Ryoul; Park, Seorim; Suh, Pann-Ghill; Follo, Matilde Yung; Cocco, Lucio; Ryu, Sung Ho

    2016-01-01

    Psychological stress is an emotion experienced when people are under mental pressure or encounter unexpected problems. Extreme or repetitive stress increases the risk of developing human disease, including cardiovascular disease (CVD), immune diseases, mental disorders, and cancer. Several studies have shown an association between psychological stress and cancer growth and metastasis in animal models and case studies of cancer patients. Stress induces the secretion of stress-related mediators, such as catecholamine, cortisol, and oxytocin, via the activation of the hypothalamic-pituitary-adrenocortical (HPA) axis or the sympathetic nervous system (SNS). These stress-related hormones and neurotransmitters adversely affect stress-induced tumor progression and cancer therapy. Catecholamine is the primary factor that influences tumor progression. It can regulate diverse cellular signaling pathways through adrenergic receptors (ADRs), which are expressed by several types of cancer cells. Activated ADRs enhance the proliferation and invasion abilities of cancer cells, alter cell activity in the tumor microenvironment, and regulate the interaction between cancer and its microenvironment to promote tumor progression. Additionally, other stress mediators, such as glucocorticoids and oxytocin, and their cognate receptors are involved in stress-induced cancer growth and metastasis. Here, we will review how each receptor-mediated signal cascade contributes to tumor initiation and progression and discuss how we can use these molecular mechanisms for cancer therapy.

  7. Aetiology and Pathogenesis of Trigeminal Neuralgia: a Comprehensive Review

    Directory of Open Access Journals (Sweden)

    Gintautas Sabalys

    2012-12-01

    Full Text Available Objectives: The aim of present paper was to discuss issues related to trigeminal neuralgia with strong emphasis on the aetiology and pathogenesis of this problem. Material and Methods: An electronic search of 5 databases (1965 - Oct 2012 and a hand search of peer-reviewed journals for relevant articles were performed. In addition, experience acquired from treating 3263 patients in the Department of Maxillofacial Surgery, Lithuanian University of Health Sciences, were also summarized. Results: Generally, aetiological factors can be classified into 3 most popular theories that were based on: 1 Related to other disease, 2 Direct injury to the trigeminal nerve, and 3 Propagates the polyetiologic origin of the disease. In addition, two pathogenesis mechanisms of trigeminal neuralgia were proposed. First: the peripheral pathogenetic mechanism that is often induced by progressive dystrophy around the peripheral branches of the trigeminal nerve. Second, central pathogenetic mechanism which often triggered by peripheral pathogen that causes long-lasting afferent impulsation and the formation of a stable pathologic paroxysmal type irritation focus on the central nerve system (CNS. Conclusions: Patients with susceptive trigeminal neuralgia should be examined carefully by specialists who have expertise in assessing and diagnosing of possible pathological processes and be able to eliminate the contributing factors so the trigeminal neuralgia can be properly managed.

  8. Car drivers with dementia : different complications due to different aetiologies?

    NARCIS (Netherlands)

    Piersma, D. Waard, D. de Davidse, R. Tucha, O. & Brouwer,W.

    2015-01-01

    Older drivers with dementia are an at-risk group for unsafe driving. However, dementia refers to various aetiologies and the question is whether dementias of different aetiology have similar effects on driving ability. The literature on the effects of dementia of various aetiologies on driving abili

  9. Aetiology of Oral Cancer in the Sudan

    OpenAIRE

    Hussain Gadelkarim Ahmed

    2013-01-01

    ABSTRACT Objectives To review the studied risk factors that linked to aetiology of oral cancer in the Sudan. There have been numerous reports in the increase in the incidence of oral cancer from various parts of the world. A recent trend for a rising incidence of oral cancer, with the absence of the well established risk factors, has raised concern. Although, there are inconsistent data on incidence and demographical factors, studies suggest that the physiologic response to risk factors by me...

  10. Aetiology of Oral Cancer in the Sudan

    Directory of Open Access Journals (Sweden)

    Hussain Gadelkarim Ahmed

    2013-04-01

    Full Text Available Objectives: To review the studied risk factors that linked to aetiology of oral cancer in the Sudan. There have been numerous reports in the increase in the incidence of oral cancer from various parts of the world. A recent trend for a rising incidence of oral cancer, with the absence of the well established risk factors, has raised concern. Although, there are inconsistent data on incidence and demographical factors, studies suggest that the physiologic response to risk factors by men and women vary in different populations.Material and Methods: This review principally examines 33 publications devoted to aetiology of oral cancer in the Sudan, in addition to some risk factors that are commonly practiced in the Sudan.Results: Several studies examining risk factors for oral cancer include tobacco use (Smoked and Smokeless, alcohol consumption, occupational risk, familial risk, immune deficits, virus infection and genetic factors.Conclusions: Toombak use and infection with high risk Human Papilloma Virus (HPV were extensively investigated and linked to the aetiology of oral cancer in Sudan.

  11. Curved Nanotube Structures under Mechanical Loading

    OpenAIRE

    Hamidreza Yazdani Sarvestani; Ali Naghashpour

    2015-01-01

    Configuration of carbon nanotube (CNT) has been the subject of research to perform theoretical development for analyzing nanocomposites. A new theoretical solution is developed to study curved nanotube structures subjected to mechanical loadings. A curved nanotube structure is considered. A nonlocal displacement-based solution is proposed by using a displacement approach of Toroidal Elasticity based on Eringen’s theory of nonlocal continuum mechanics. The governing equations of curved nanotub...

  12. Curved Nanotube Structures under Mechanical Loading

    Directory of Open Access Journals (Sweden)

    Hamidreza Yazdani Sarvestani

    2015-01-01

    Full Text Available Configuration of carbon nanotube (CNT has been the subject of research to perform theoretical development for analyzing nanocomposites. A new theoretical solution is developed to study curved nanotube structures subjected to mechanical loadings. A curved nanotube structure is considered. A nonlocal displacement-based solution is proposed by using a displacement approach of Toroidal Elasticity based on Eringen’s theory of nonlocal continuum mechanics. The governing equations of curved nanotube structures are developed in toroidal coordinate system. The method of successive approximation is used to discretize the displacement-based governing equations and find the general solution subjected to bending moment. The numerical results show that all displacement components increase with increasing the nonlocal parameter. The present theoretical study highlights the significance of the geometry and nonlocal parameter effects on mechanical behavior of nanotube structures.

  13. Mechanisms underlying an ability to behave ethically.

    Science.gov (United States)

    Pfaff, Donald W; Kavaliers, Martin; Choleris, Elena

    2008-05-01

    Cognitive neuroscientists have anticipated the union of neural and behavioral science with ethics (Gazzaniga 2005). The identification of an ethical rule--the dictum that we should treat others in the manner in which we would like to be treated--apparently widespread among human societies suggests a dependence on fundamental human brain mechanisms. Now, studies of neural and molecular mechanisms that underlie the feeling of fear suggest how this form of ethical behavior is produced. Counterintuitively, a new theory presented here states that it is actually a loss of social information that leads to sharing others' fears with our own, thus allowing us to treat others as we would like to be treated. Adding to that hypothetical mechanism is the well-studied predilection toward affiliative behaviors. Thus, even as Chomsky hypothesizes that humans are predisposed to utter grammatical sentences, we propose that humans are 'wired for reciprocity'. However, these two neural forces supporting ethical behavior do not explain individual or collective violence. At any given moment, the ability to produce behavior that obeys this ethical rule is proposed to depend on a balance between mechanisms for prosocial and antisocial behaviors. That balance results not only from genetic influences on temperament but also from environmental effects particularly during critical neonatal and pubertal periods. PMID:18642189

  14. Cellular and molecular mechanisms underlying muscular dystrophy

    OpenAIRE

    Rahimov, Fedik; Kunkel, Louis M

    2013-01-01

    The muscular dystrophies are a group of heterogeneous genetic diseases characterized by progressive degeneration and weakness of skeletal muscle. Since the discovery of the first muscular dystrophy gene encoding dystrophin, a large number of genes have been identified that are involved in various muscle-wasting and neuromuscular disorders. Human genetic studies complemented by animal model systems have substantially contributed to our understanding of the molecular pathomechanisms underlying ...

  15. Mechanisms Underlying Induction of Tolerance to Foods.

    Science.gov (United States)

    Berin, M Cecilia; Shreffler, Wayne G

    2016-02-01

    Oral tolerance refers to a systemic immune nonresponsiveness to antigens first encountered by the oral route, and a failure in development of this homeostatic process can result in food allergy. Clinical tolerance induced by allergen immunotherapy is associated with alterations in immune mechanisms relevant to the allergic response, including reduction of basophil reactivity, induction of IgG4, loss of effector Th2 cells, and induction of Tregs. The relative contribution of these immune changes to clinical tolerance to foods, and the duration of these immune changes after termination of immunotherapy, remains to be identified. PMID:26617229

  16. [Salivary stones: aetiology, composition and treatment].

    Science.gov (United States)

    Kraaij, S; Brand, H S; Karagozoglu, K H; Forouzanfar, T; Veerman, E C I

    2014-11-01

    Salivary stones or sialoliths, are calcified concrements which are most frequently located in the submandibular glands and their ducts. Their size and weight show considerable variation. The aetiology is unknown. It has been suggested that salivary stones could be related to an altered saliva composition, the anatomy of the ducts of the salivary gland and/or the fusion of microsialoliths. Salivary stones consist mainly of anorganic material such as hydroxyapatite, whitlockite and calciumphosphate, but they also contain organic components such as proteins and lipids. Treatment can consist of salivary gland massage combined with an acid diet, ultrasonic pulverisation, and surgical or sialendoscopical removal. PMID:26188478

  17. Habitats under Mechanical and Herbicide Management Regimes

    Directory of Open Access Journals (Sweden)

    Wendy-Ann P. Isaac

    2012-01-01

    Full Text Available Commelina diffusa is a colonising species of banana orchard habitats in St. Vincent in the Windward Islands of the Caribbean. In the present study, the population dynamics of C. diffusa were investigated in response to mechanical weed management with either a rotary string trimmer or glufosinate in ruderal and banana habitats. The study focused on density and size distribution of the weed over time and their response to two weed management strategies. The population dynamics of C. diffusa differed between the two habitats. Seedling establishment appeared to be an important factor influencing the dynamics of C. diffusa in banana orchards as there was little recruitment of seeds with less flower production compared with ruderal habitats where plants produced more flowers. Plants of C. diffusa in the banana orchard habitat had a longer growth cycle. In the banana orchard habitat, the C. diffusa population was greater and the plants were shorter with mechanical management than in areas treated with glufosinate. The results suggest that it is possible to manipulate the dynamics of C. diffusa in banana orchards as there is less chance of seed recruitment. Further research is necessary to refine an IPM approach for the management of C. diffusa.

  18. Environmental genotoxicity: Probing the underlying mechanisms

    Energy Technology Data Exchange (ETDEWEB)

    Shugart, L. [Oak Ridge National Lab., TN (United States); Theodorakis, C. [Tennessee Univ., Knoxville, TN (United States)

    1993-12-31

    Environmental pollution is a complex issue because of the diversity of anthropogenic agents, both chemical and physical, that have been detected and catalogued. The consequences to biota from exposure to genotoxic agents present an additional problem because of the potential for these agents to produce adverse change at the cellular and organismal levels. Past studies in genetic toxicology at the Oak Ridge National Laboratory have focused on structural damage to the DNA of environmental species that may occur after exposure to genotoxic agents and the use of this information to document exposure and to monitor remediation. In an effort to predict effects at the population, community and ecosystem levels, current studies in genetic ecotoxicology are attempting to characterize the biological mechanisms at the gene level that regulate and limit the response of an individual organism to genotoxic factors in their environment.

  19. Imprinting in Plants and Its Underlying Mechanisms

    Institute of Scientific and Technical Information of China (English)

    Hongyu Zhang; Abed Chaudhury; Xianjun Wu

    2013-01-01

    Genomic imprinting (or imprinting) refers to an epigenetic phenomenon by which the allelic expression of a gene depends on the parent of origin.It has evolved independently in placental mammals and flowering plants.In plants,imprinting is mainly found in endosperm.Recent genome-wide surveys in Arabidopsis,rice,and maize identified hundreds of imprinted genes in endosperm.Since these genes are of diverse functions,endosperm development is regulated at different regulatory levels.The imprinted expression of only a few genes is conserved between Arabidopsis and monocots,suggesting that imprinting evolved quickly during speciation.In Arabidopsis,DEMETER (DME) mediates hypomethylation in the maternal genome at numerous loci (mainly transposons and repeats) in the central cell and results in many differentially methylated regions between parental genomes in the endosperm,and subsequent imprinted expression of some genes.In addition,histone modification mediated by Polycomb group (PcG) proteins is also involved in regulating imprinting.DMEinduced hypomethylated alleles in the central cell are considered to produce small interfering RNAs (siRNAs) which are imported to the egg to reinforce DNA methylation.In parallel,the activity of DME in the vegetative cell of the male gametophyte demethylates many regions which overlap with the demethylated regions in the central cell.siRNAs from the demethylated regions are hypothesized to be also transferred into sperm to reinforce DNA methylation.Imprinting is partly the result of genome-wide epigenetic reprogramming in the central cell and vegetative cell and evolved under different selective pressures.

  20. Fungal Nail Infections: Spectrum of Aetiologic Agents and Pattern of Lesions

    Directory of Open Access Journals (Sweden)

    Anyimson James

    2016-03-01

    Full Text Available Objective: Worldwide, fungal nail infections have been on the increase, with social, cultural and economic factors contributing to it. Information on the spectrum of fungal nail infection is sparse in Nigeria. This study was carried out to establish the infection rates, aetiology and clinical types of onychomycosis in Calabar. Methods: Subjects were drawn from manicure and pedicure salons, farming settlements, mechanic workshops and dermatology clinic. A structured questionnaire was administered to participants for demographic data. Nail scrapings and clippings were obtained from subjects under standard aseptic procedure. Samples were pulverized and subjected to microscopy and culture. Standard mycological techniques were used to identify and characterize isolates. Results: Out of the 32.7% infection rates in the study, males 33.8%% were more infected than females 32.3% and subjects aged 41-50 years had the highest rate of infections. Candida species were more prevalent 63.6% than dermatophytic moulds 36.4%. Trichophyton rubrum was the most prevalent 18.2% dermatophyte. The distribution of pathogenic isolates on fingernails 45.5% and toenails 42.4% was statistically significant (χ2 =7.2, p= 0.03. Disto-lateral subungual onychomycosis (DLSO 51(50.5% was the most common type of nail lesion but most of the isolates 14(42.4% were recovered from TDO. Conclusion: Onychomycosis affected more adults than adolescents of both sexes in our locality. Candida species are becoming prevalent aetiologic agents of these infections, and their importance should not be overlooked in the management of patients. J Microbiol Infect Dis 2016;6(1: 23-27

  1. Arsenic in the aetiology of cancer.

    Science.gov (United States)

    Tapio, Soile; Grosche, Bernd

    2006-06-01

    Arsenic, one of the most significant hazards in the environment affecting millions of people around the world, is associated with several diseases including cancers of skin, lung, urinary bladder, kidney and liver. Groundwater contamination by arsenic is the main route of exposure. Inhalation of airborne arsenic or arsenic-contaminated dust is a common health problem in many ore mines. This review deals with the questions raised in the epidemiological studies such as the dose-response relationship, putative confounders and synergistic effects, and methods evaluating arsenic exposure. Furthermore, it describes the metabolic pathways of arsenic, and its biological modes of action. The role of arsenic in the development of cancer is elucidated in the context of combined epidemiological and biological studies. However, further analyses by means of molecular epidemiology are needed to improve the understanding of cancer aetiology induced by arsenic.

  2. Noma: an "infectious" disease of unknown aetiology.

    Science.gov (United States)

    Baratti-Mayer, Denise; Pittet, Brigitte; Montandon, Denys; Bolivar, Ignacio; Bornand, Jacques-Etienne; Hugonnet, Stéphane; Jaquinet, Alexandre; Schrenzel, Jacques; Pittet, Didier

    2003-07-01

    Noma (cancrum oris) is a devastating gangrenous disease that leads to severe tissue destruction in the face and is associated with high morbidity and mortality. It is seen almost exclusively in young children living in remote areas of less developed countries, particularly in Africa. The exact prevalence of the disease is unknown, but a conservative estimate is that 770000 people are currently affected by noma sequelae. The cause remains unknown, but a combination of several elements of a plausible aetiology has been identified: malnutrition, a compromised immune system, poor oral hygiene and a lesion of the gingival mucosal barrier, and an unidentified bacterial factor acting as a trigger for the disease. This review discusses the epidemiology, clinical features, current understanding of the pathophysiology, and treatment of the acute phase and sequelae requiring reconstructive surgery. Noma may be preventable if recognised at an early stage. Further research is needed to identify more exactly the causative agents.

  3. Anorexia nervosa: aetiology, assessment, and treatment.

    Science.gov (United States)

    Zipfel, Stephan; Giel, Katrin E; Bulik, Cynthia M; Hay, Phillipa; Schmidt, Ulrike

    2015-12-01

    Anorexia nervosa is an important cause of physical and psychosocial morbidity. Recent years have brought advances in understanding of the underlying psychobiology that contributes to illness onset and maintenance. Genetic factors influence risk, psychosocial and interpersonal factors can trigger onset, and changes in neural networks can sustain the illness. Substantial advances in treatment, particularly for adolescent patients with anorexia nervosa, point to the benefits of specialised family-based interventions. Adults with anorexia nervosa too have a realistic chance of achieving recovery or at least substantial improvement, but no specific approach has shown clear superiority, suggesting a combination of re-nourishment and anorexia nervosa-specific psychotherapy is most effective. To successfully fight this enigmatic illness, we have to enhance understanding of the underlying biological and psychosocial mechanisms, improve strategies for prevention and early intervention, and better target our treatments through improved understanding of specific disease mechanisms. PMID:26514083

  4. Prevalence, and Intellectual Outcome of Unilateral Focal Cortical Brain Damage as a Function of Age, Sex and Aetiology

    Directory of Open Access Journals (Sweden)

    C. M. J. Braun

    2002-01-01

    Full Text Available Neurologists and neuropsychologists are aware that aging men are more at risk than women for brain damage, principally because of the well known male-predominant risk for cardiovascular disease and related cerebrovascular accidents. However, a disproportion in prevalence of brain damage between the sexes in childhood may be less suspected. Furthermore, sex-specific risk for other aetiologies of brain damage may be little known, whether in the pediatric or adult populations. Proposals of a sex difference in cognitive recovery from brain damage have also been controversial. Six hundred and thirty five “consecutive” cases with cortical focal lesions including cases of all ages and both sexes were reviewed. Aetiology of the lesion was determined for each case as was postlesion IQ. Risk was highly male prevalent in all age groups, with a predominance of cardiovascular aetiology explaining much of the adult male prevalence. However, several other aetiological categories were significantly male prevalent in juveniles (mitotic, traumatic, dysplasic and adults (mitotic, traumatic. There was no sex difference in outcome (i.e., postlesion IQ of these cortical brain lesions for the cohort as a whole, after statistical removal of the influence of lesion extent, aetiology and presence of epilepsy. Mechanisms potentially responsible for sex differences in prevalence, aetiology of brain damage, and recovery, are reviewed and discussed.

  5. Wound Pruritus: Prevalence, Aetiology and Treatment.

    OpenAIRE

    Upton D, Richardson C, Van Acker K, Andrews A and Springett K

    2013-01-01

    l O bjective: To review the literature into itching or pruritus, in relation to burns or other types of wound, with a focus on the physiological mechanisms underlying itching and the issues associated with itching in people with wounds. l Method: A literature search was conducted using PubMed, MEDLINE and Google Scholar, including English-language papers published up to 2012. The search terms used were: [‘pruritus’ OR ‘itching’] OR [‘chronic’] AND [‘wounds’ OR â...

  6. Changes in aetiological determinants of urinary fistula

    Institute of Scientific and Technical Information of China (English)

    Prosper E. Gharoro; Chukwunwendu A. Okonkwo

    2009-01-01

    Objective: Objective: To investigate the localization and aetiological factors associated with urinary fistulae at the University Teaching Hospital in Benin-City, Nigeria. Methods: Records on 96 patients treated by the authors at the gynaecological ward of the University of Benin Teaching Hospital, Benin-City, Nigeria between January 1997 and December 2006 were analyzed. Information extracted and analyzed included data on socio-biological, demographic, and obstetric event of the antecedent pregnancy. Results: The average age of patients with vesico-vaginal fistula(VVF) was 34 years with a mean parity of 3. The various mean values for patients' height, weight and body mass index (BMI) were 1.58m, 58.29kg and 24.13 respectively. The majority (92.7%) of fistulas are obstetric in origin. While 5.21% were due to total abdominal hysterectomy and 2.08% due to post irradiation for advanced gynecological malignancy. 53(55.21%) patients had obstetric operative interventions (Forceps or vacuum extraction, and or caesarean section). Caesarean section contributed 23.96% to the total figure. Juxta-cervical fistula was the most frequent, next mid vagina and followed by vesico-uterine (32. 98%, 24.4% and 19.15% respectively).Conclusion: Obstetric surgical intervention by care providers is a major cause of VVF formation with particular reference to Caesarean section. Vesico-uterine fistulas are on the increase.

  7. Enterovesical Fistulae: Aetiology, Imaging, and Management

    Directory of Open Access Journals (Sweden)

    Tomasz Golabek

    2013-01-01

    Full Text Available Background and Study Objectives. Enterovesical fistula (EVF is a devastating complication of a variety of inflammatory and neoplastic diseases. Radiological imaging plays a vital role in the diagnosis of EVF and is indispensable to gastroenterologists and surgeons for choosing the correct therapeutic option. This paper provides an overview of the diagnosis of enterovesical fistulae. The treatment of fistulae is also briefly discussed. Material and Methods. We performed a literature review by searching the Medline database for articles published from its inception until September 2013 based on clinical relevance. Electronic searches were limited to the keywords: “enterovesical fistula,” “colovesical fistula” (CVF, “pelvic fistula”, and “urinary fistula”. Results. EVF is a rare pathology. Diverticulitis is the commonest aetiology. Over two-thirds of affected patients describe pathognomonic features of pneumaturia, fecaluria, and recurrent urinary tract infections. Computed tomography is the modality of choice for the diagnosis of enterovesical fistulae as not only does it detect a fistula, but it also provides information about the surrounding anatomical structures. Conclusions. In the vast majority of cases, this condition is diagnosed because of unremitting urinary symptoms after gastroenterologist follow-up procedures for a diverticulitis or bowel inflammatory disease. Computed tomography is the most sensitive test for enterovesical fistula.

  8. An Adaptive Mechanism for Accurate Query Answering under Differential Privacy

    CERN Document Server

    Li, Chao

    2012-01-01

    We propose a novel mechanism for answering sets of count- ing queries under differential privacy. Given a workload of counting queries, the mechanism automatically selects a different set of "strategy" queries to answer privately, using those answers to derive answers to the workload. The main algorithm proposed in this paper approximates the optimal strategy for any workload of linear counting queries. With no cost to the privacy guarantee, the mechanism improves significantly on prior approaches and achieves near-optimal error for many workloads, when applied under (\\epsilon, \\delta)-differential privacy. The result is an adaptive mechanism which can help users achieve good utility without requiring that they reason carefully about the best formulation of their task.

  9. Cooperative Mechanism of Supply Chain Under Asymmetric Information

    Institute of Scientific and Technical Information of China (English)

    郭敏; 王红卫; 瞿坦

    2003-01-01

    The cooperative mechanism is one main issue in the decentralized supply chain system, especially in an asymmetric information structure. We analyze the non-cooperative game behavior of a 2-echelon distribution supply chain, compare the results with the system optimal solution, and give the supplier dominated cooperative mechanisms. We also analyze the validity of our contract under the asymmetric retailers' holding cost information and give some useful conclusions.

  10. Micronutrients and cancer aetiology: the epidemiological evidence.

    Science.gov (United States)

    Key, T

    1994-11-01

    Micronutrient deficiencies occur most commonly in poor countries and, therefore, are most likely to be associated with cancers common in these countries. Epidemiological studies are hampered by inaccurate measurement of micronutrient intake and by the correlations between intakes of many nutrients. The strongest evidence for a protective effect of micronutrients is for oesophageal cancer. The identity of the micronutrients is not certain, but may include retinol, riboflavin, ascorbic acid and Zn; alcohol, smoking and dietary nitrosamines increase the risk for oesophageal cancer. For stomach cancer there is good evidence that fruit and vegetables are protective. The protective effect of these foods might be largely due to ascorbic acid, but other nutrients and non-nutrients may also be important; the risk for stomach cancer is increased by salt, some types of preserved foods, and by infection of the stomach with the bacterium Helicobacter pylori. The risk for lung cancer appears to be reduced by a high intake of fruit and vegetables, but it is not clear which agents are responsible and the major cause of lung cancer is cigarette smoking. Diet is probably the major determinant of the risk for colo-rectal cancer; there is evidence that fruit and vegetables and fibre reduce risk and that meat and animal fat increase risk, but there is no convincing evidence that these relationships are mediated by micronutrients. The risk for cervical cancer is inversely related to fruit and vegetable consumption and, therefore, to consumption of carotenoids and ascorbic acid, but the major cause of this cancer is human papillomavirus and it is not yet clear whether the dietary associations indicate a true protective effect or whether they are due to confounding by other variables. The evidence that micronutrients are important in the aetiology of either breast cancer or prostate cancer is weak, but the possible roles of 1,25-dihydroxycholecalciferol and alpha-tocopherol in prostate

  11. Aetiological and clinical aspects of symptomatic gallstone disease and pancreatic cancer.

    OpenAIRE

    Banim, Paul

    2011-01-01

    Introduction This work investigated in a UK prospective cohort study, firstly, the aetiology of gallstone disease, and secondly, that of pancreatic cancer, with a focus on physical activity and diet. The epidemiological studies benefitted from the accuracy of measurement tools, namely a validated physical activity questionnaire and a sevenday food diary (7-DFD). These novel methods aided the improved definition of risk factors thus highlighting biological mechanisms leading to disease and ...

  12. Neural Circuitry and Plasticity Mechanisms Underlying Delay Eyeblink Conditioning

    Science.gov (United States)

    Freeman, John H.; Steinmetz, Adam B.

    2011-01-01

    Pavlovian eyeblink conditioning has been used extensively as a model system for examining the neural mechanisms underlying associative learning. Delay eyeblink conditioning depends on the intermediate cerebellum ipsilateral to the conditioned eye. Evidence favors a two-site plasticity model within the cerebellum with long-term depression of…

  13. Failure mechanisms in thin rubber sheet composites under static solicitation

    Directory of Open Access Journals (Sweden)

    E. Bayraktar

    2007-03-01

    Full Text Available Purpose: Mechanical behaviour and damage mechanisms in thin rubber sheet composites were investigated under static solicitation at room temperature. Two types of rubber are used in this study; Natural rubber, NR vulcanised and reinforced by carbon black and Synthetic rubber (styrene-butadiene-rubber, SBR.Design/methodology/approach: A comprehensive study has been carried out in order to identify a threshold criterion for the damage mechanism to explain a tearing criterion for the concept of tearing energy of the elastomers and also to give a detail for the damage mechanism depending on the loading conditions. A typical type of specimen geometry of thin sheet rubber composite materials was studied under static tensile tests conducted on the smooth and notched specimens with variable depths. In this way, the effects of the plane stress on the damage mechanism are characterized depending on the rubber materials.Findings: Damage mechanisms during tensile test have been described for both of rubber types and the criteria which characterize the tearing resistance, characteristic energy for tearing (T was explained. Damage in the specimens were evaluated just at the beginning of the tearing by means of the observations in the scanning electron microscopy (SEM.Practical implications: A tearing criterion was suggested in the case of simple tension conditions by assuming large strain. In the next step of this study, a finite element analysis (FEA will be applied under the same conditions of this part in order to obtain the agreement between experimental and FEA results.Originality/value: This study propses a threshold criterion for the damage just at the beginning of the tearing for thin sheet rubber composites and gives a detail discussion for explaining the damage mechanisms by SEM results. This type of study gives many facilities for the sake of simplicity in industrial application.

  14. Lamsiekte (botulism: Solving the aetiology riddle

    Directory of Open Access Journals (Sweden)

    Rudolph D. Bigalke

    2012-10-01

    Full Text Available The reason or reasons why it took Sir Arnold Theiler so many years to unravel the riddle of the aetiology of lamsiekte in cattle and whether P.R. Viljoen’s lifelong grudge for receiving insufficient credit from Theiler for his research contribution was justified are analysed in this paper. By 1912, Theiler knew that Duncan Hutcheon had advocated the use of bonemeal as a prophylactic against the disease in the early 1880s. Hutcheon’s colleague, J.D. Borthwick, had shown conclusively in a field experiment in 1895 that lamsiekte did not occur in cattle fed a liberal allowance of bonemeal; and bone-craving had been identified by Hutcheon and several farmers as being associated with the occurrence of the disease (a ‘premonitory’ sign. Hutcheon regarded a phosphate deficiency of the pastures as the direct cause of lamsiekte. However, Theiler did not accept this, was convinced that intoxication was involved and developed a ‘grass toxin’ theory. Viljoen (1918 also latched onto the grass toxin theory. He did not believe that osteophagia existed, stating categorically that he had not observed it on the experimental farm Armoedsvlakte where > 100 cases of lamsiekte had occurred during the > 3 years that he spent there. Moreover, he did not believe in the prophylactic value of bonemeal. However, careful analysis of a subsequent publication, of which he was a co-author, revealed that in late 1918 and early 1919 he reproduced the disease by drenching cattle with blowfly pupae and larvae as well as with crushed bones from decomposing bovine carcasses. For this breakthrough he did not get proper credit from Theiler. Reappointed to study lamsiekte on Armoedsvlakte in the autumn of 1919, Theiler, probably already aware that the toxin he was seeking was in the decomposing bones or carcass material rather than the grass, deliberately ‘walked with the cattle’ on the farm to encounter a classic manifestation of bone-craving (osteophagia. The penny

  15. Mechanical Analysis of Concrete Specimen under Restrained Condition

    Institute of Scientific and Technical Information of China (English)

    MA Xinwei; NIU Changren; R D Hooton

    2005-01-01

    In order to quantify the development of the tensile stresses and obtain a reliable estimation of the cracking risk, the concrete was subjected to restrained conditions. The fully restrained condition was achieved by keeping the length constant of a concrete specimen. Comparing the free shrinkage with the restrained shrinkage,tensile creep could be discriminated from shrinkage. The testing method was introduced in details, and the mechanical behaviors under tensile load were analyzed. Results show that concrete exhibits a pronounced viscoelasticity. Under restrained condition, the self induced tensile stress increases with time. The lower the water to cement ratio, the larger the tensile stress at the same age. The tensile creep of hardening concrete is much larger than that of hardened concrete. The relationships among autogenous shrinkage under free condition, elastic strain and creep under restrained condition are described, and the mathematical model for the calculation of elastic strain and creep is proposed.

  16. Nanomaterial-modulated autophagy: underlying mechanisms and functional consequences.

    Science.gov (United States)

    Zheng, Wei; Wei, Min; Li, Song; Le, Weidong

    2016-06-01

    Autophagy is an essential lysosome-dependent process that controls the quality of the cytoplasm and maintains cellular homeostasis, and dysfunction of this protein degradation system is correlated with various disorders. A growing body of evidence suggests that nanomaterials (NMs) have autophagy-modulating effects, thus predicting a valuable and promising application potential of NMs in the diagnosis and treatment of autophagy-related diseases. NMs exhibit unique physical, chemical and biofunctional properties, which may endow NMs with capabilities to modulate autophagy via various mechanisms. The present review highlights the impacts of various NMs on autophagy and their functional consequences. The possible underlying mechanisms for NM-modulated autophagy are also discussed.

  17. A possible realization of Einstein's causal theory underlying quantum mechanics

    International Nuclear Information System (INIS)

    It is shown that a new microscopic mechanics formulated earlier can be looked upon as a possible causal theory underlying quantum mechanics, which removes Einstein's famous objections against quantum theory. This approach is free from objections raised against Bohm's hidden variable theory and leads to a clear physical picture in terms of familiar concepts, if self interactions are held responsible for deviations from classical behaviour. The new level of physics unfolded by this approach may reveal novel frontiers in high-energy physics. (author)

  18. Permeability and mechanical properties of cracked glass under pressure

    International Nuclear Information System (INIS)

    Crack initiation and growth in brittle solids under tension have been extensively studied by various experimental, theoretical and numerical approaches. If has been established that dynamic brittle fracture is related to fundamental physical parameters and processes, such as crack speed, crack branching, surface roughening, and dynamic instabilities. On the other hand, less studies have been done in the area of compressive fracture despite its vital importance in geology, material science and engineering applications (such as the improvement and the insurance of the nuclear wastes storage). The present work aims to investigate thermo-mechanical cracking effects on elastic wave velocities, mechanical strength and permeability und r pressure to evaluate damage evolution, brittle failure and transport properties on a synthetic glass (SON 68), and to highlight the very different behavior of the glass amorphous structure compared to any rock structure. The original glass, produced in ideal conditions of slow cooling that prevent from any crack formation, exhibits a linear and reversible mechanical behavior and isotropic elastic velocities, as expected. It also presents a high strength as it fails at about 700 MPa of deviatoric stress for a confining pressure of 15 MPa. We choose to apply to some original glass samples a reproducible method (thermal treatment with a thermal shock of T=100,200 and 300 C) which creates cracks with a homogeneous distribution. The impact of the thermal treatment is clearly visible through the elastic wave velocity measurements as we observe crack closure under hydrostatic conditions (at about 30 MPa). For T ≥ 200 C, the glass mechanical behavior becomes non linear and records an irreversible damage. The total damage observed with the acoustic emissions in these samples underlines the combination of the thermal and the mechanical cracks which drive to the sample failure. The results obtained with pore fluid pressure show a very small

  19. The problems of urinary tract infections with Candida spp. aetiology in women.

    Science.gov (United States)

    Tomczak, Hanna; Szałek, Edyta; Grześkowiak, Edmund

    2014-01-01

    Urinary tract infections (UTIs) in women are a growing clinical concern. The most frequent risk factors of UTIs with fungal aetiology in women are: antibiotic therapy (especially broad-spectrum antibiotics), immunosuppressive therapy, diabetes, malnutrition, pregnancy, and frequent intercourse. The aim of the study was to analyse urinary tract infections with Candida spp. aetiology in women hospitalised at the Clinical Hospital in Poznań, Poland, between 2009 and 2011. The investigations revealed that as many as 71% of positive urine cultures with Candida fungi came from women. The following fungi were most frequently isolated from the patients under analysis: C. albicans (47%), C. glabrata (31%), C. tropicalis (6%), C. krusei (3%). In order to diagnose a UTI the diagnosis cannot be based on a single result of a urine culture. Due to the small number of antifungal drugs and high costs of treatment, antifungal drugs should be applied with due consideration and care.

  20. Emotional responses to music: the need to consider underlying mechanisms.

    Science.gov (United States)

    Juslin, Patrik N; Västfjäll, Daniel

    2008-10-01

    Research indicates that people value music primarily because of the emotions it evokes. Yet, the notion of musical emotions remains controversial, and researchers have so far been unable to offer a satisfactory account of such emotions. We argue that the study of musical emotions has suffered from a neglect of underlying mechanisms. Specifically, researchers have studied musical emotions without regard to how they were evoked, or have assumed that the emotions must be based on the "default" mechanism for emotion induction, a cognitive appraisal. Here, we present a novel theoretical framework featuring six additional mechanisms through which music listening may induce emotions: (1) brain stem reflexes, (2) evaluative conditioning, (3) emotional contagion, (4) visual imagery, (5) episodic memory, and (6) musical expectancy. We propose that these mechanisms differ regarding such characteristics as their information focus, ontogenetic development, key brain regions, cultural impact, induction speed, degree of volitional influence, modularity, and dependence on musical structure. By synthesizing theory and findings from different domains, we are able to provide the first set of hypotheses that can help researchers to distinguish among the mechanisms. We show that failure to control for the underlying mechanism may lead to inconsistent or non-interpretable findings. Thus, we argue that the new framework may guide future research and help to resolve previous disagreements in the field. We conclude that music evokes emotions through mechanisms that are not unique to music, and that the study of musical emotions could benefit the emotion field as a whole by providing novel paradigms for emotion induction. PMID:18826699

  1. Aetiological factors behind adipose tissue inflammation

    DEFF Research Database (Denmark)

    von Scholten, Bernt J; Andresen, Erik N; Sørensen, Thorkild I A;

    2013-01-01

    Despite extensive research into the biological mechanisms behind obesity-related inflammation, knowledge of environmental and genetic factors triggering such mechanisms is limited. In the present narrative review we present potential determinants of adipose tissue inflammation and suggest ways...

  2. Cellular mechanisms underlying eosinophilic and neutrophilic airway inflammation in asthma.

    Science.gov (United States)

    Pelaia, Girolamo; Vatrella, Alessandro; Busceti, Maria Teresa; Gallelli, Luca; Calabrese, Cecilia; Terracciano, Rosa; Maselli, Rosario

    2015-01-01

    Asthma is a phenotypically heterogeneous chronic disease of the airways, characterized by either predominant eosinophilic or neutrophilic, or even mixed eosinophilic/neutrophilic inflammatory patterns. Eosinophilic inflammation can be associated with the whole spectrum of asthma severity, ranging from mild-to-moderate to severe uncontrolled disease, whereas neutrophilic inflammation occurs mostly in more severe asthma. Eosinophilic asthma includes either allergic or nonallergic phenotypes underlying immune responses mediated by T helper (Th)2 cell-derived cytokines, whilst neutrophilic asthma is mostly dependent on Th17 cell-induced mechanisms. These immune-inflammatory profiles develop as a consequence of a functional impairment of T regulatory (Treg) lymphocytes, which promotes the activation of dendritic cells directing the differentiation of distinct Th cell subsets. The recent advances in the knowledge of the cellular and molecular mechanisms underlying asthmatic inflammation are contributing to the identification of novel therapeutic targets, potentially suitable for the implementation of future improvements in antiasthma pharmacologic treatments. PMID:25878402

  3. Cellular Mechanisms Underlying Eosinophilic and Neutrophilic Airway Inflammation in Asthma

    Directory of Open Access Journals (Sweden)

    Girolamo Pelaia

    2015-01-01

    Full Text Available Asthma is a phenotypically heterogeneous chronic disease of the airways, characterized by either predominant eosinophilic or neutrophilic, or even mixed eosinophilic/neutrophilic inflammatory patterns. Eosinophilic inflammation can be associated with the whole spectrum of asthma severity, ranging from mild-to-moderate to severe uncontrolled disease, whereas neutrophilic inflammation occurs mostly in more severe asthma. Eosinophilic asthma includes either allergic or nonallergic phenotypes underlying immune responses mediated by T helper (Th2 cell-derived cytokines, whilst neutrophilic asthma is mostly dependent on Th17 cell-induced mechanisms. These immune-inflammatory profiles develop as a consequence of a functional impairment of T regulatory (Treg lymphocytes, which promotes the activation of dendritic cells directing the differentiation of distinct Th cell subsets. The recent advances in the knowledge of the cellular and molecular mechanisms underlying asthmatic inflammation are contributing to the identification of novel therapeutic targets, potentially suitable for the implementation of future improvements in antiasthma pharmacologic treatments.

  4. Shared Genetic Aetiology between Cognitive Ability and Cardiovascular Disease Risk Factors: Generation Scotland's Scottish Family Health Study

    Science.gov (United States)

    Luciano, Michelle; Batty, G. David; McGilchrist, Mark; Linksted, Pamela; Fitzpatrick, Bridie; Jackson, Cathy; Pattie, Alison; Dominiczak, Anna F.; Morris, Andrew D.; Smith, Blair H.; Porteous, David; Deary, Ian J.

    2010-01-01

    People with higher general cognitive ability in early life have more favourable levels of cardiovascular disease (CVD) risk factors in adulthood and CVD itself. The mechanism of these associations is not known. Here we examine whether general cognitive ability and CVD risk factors share genetic and/or environmental aetiology. In this large,…

  5. Brain mechanisms underlying sensation-seeking in humans

    OpenAIRE

    Norbury, A. E.

    2015-01-01

    Sensation-seeking is a personality trait concerned with motivation for intense and unusual sensory experiences, that has been identified as risk factor for a variety of psychopathologies with high social cost; in particular gambling and substance addictions. It has previously proved difficult to tease out neural mechanisms underlying sensation-seeking in humans, due to a lack of cognitive-behavioural paradigms probing sensation-seeking-like behaviour in the lab. The first aim of this thesis w...

  6. Shared Neural Mechanisms Underlying Social Warmth and Physical Warmth

    OpenAIRE

    Inagaki, TK; Eisenberger, NI

    2013-01-01

    Many of people's closest bonds grow out of socially warm exchanges and the warm feelings associated with being socially connected. Indeed, the neurobiological mechanisms underlying thermoregulation may be shared by those that regulate social warmth, the experience of feeling connected to other people. To test this possibility, we placed participants in a functional MRI scanner and asked them to (a) read socially warm and neutral messages from friends and family and (b) hold warm and neutral-t...

  7. Mechanisms underlying the antidepressant response and treatment resistance

    OpenAIRE

    Levinstein, Marjorie R.; Samuels, Benjamin A.

    2014-01-01

    Depression is a complex and heterogeneous disorder affecting millions of Americans. There are several different medications and other treatments that are available and effective for many patients with depression. However, a substantial percentage of patients fail to achieve remission with these currently available interventions, and relapse rates are high. Therefore, it is necessary to determine both the mechanisms underlying the antidepressant response and the differences between responders ...

  8. Mechanisms Underlying the Antidepressant Response and Treatment Resistance

    OpenAIRE

    Marjorie Rose Levinstein; Benjamin Adam Samuels

    2014-01-01

    Depression is a complex and heterogeneous disorder affecting millions of Americans. There are several different medications and other treatments that are available and effective for many patients with depression. However, a substantial percentage of patients fail to achieve remission with these currently available interventions, and relapse rates are high. Therefore, it is necessary to determine both the mechanisms underlying the antidepressant response and the differences between responders ...

  9. Mechanisms Underlying the Link between Cannabis Use and Prospective Memory

    OpenAIRE

    Carrie Cuttler; McLaughlin, Ryan J.; Peter Graf

    2012-01-01

    While the effects of cannabis use on retrospective memory have been extensively examined, only a limited number of studies have focused on the links between cannabis use and prospective memory. We conducted two studies to examine the links between cannabis use and both time-based and event-based prospective memory as well as potential mechanisms underlying these links. For the first study, 805 students completed an online survey designed to assess cannabis consumption, problems with cannabis ...

  10. Control of a perturbed under-actuated mechanical system

    KAUST Repository

    Zayane, Chadia

    2015-11-05

    In this work, the trajectory tracking problem for an under-actuated mechanical system in presence of unknown input disturbances is addressed. The studied inertia wheel inverted pendulum falls in the class of non minimum phase systems. The proposed high order sliding mode control architecture including a controller and differentiator allows to track accurately the predefined trajectory and to stabilize the internal dynamics. The robustness of the proposed approach is illustrated through different perturbation and output noise configurations.

  11. Crack arrest saturation model under combined electrical and mechanical loadings

    OpenAIRE

    R.R. Bhargava; A. Setia

    2009-01-01

    Purpose: The investigation aims at proposing a model for cracked piezoelectric strip which is capable to arrest the crack.Design/methodology/approach: Under the combined effect of electrical and mechanical loadings applied at the edges of the strip, the developed saturation zone is produced at each tip of the crack. To arrest further opening of the crack, the rims of the developed saturation zones are subjected to in-plane cohesive, normal uniform constant saturation point electrical displace...

  12. An NMDA Receptor-Dependent Mechanism Underlies Inhibitory Synapse Development

    Directory of Open Access Journals (Sweden)

    Xinglong Gu

    2016-01-01

    Full Text Available In the mammalian brain, GABAergic synaptic transmission provides inhibitory balance to glutamatergic excitatory drive and controls neuronal output. The molecular mechanisms underlying the development of GABAergic synapses remain largely unclear. Here, we report that NMDA-type ionotropic glutamate receptors (NMDARs in individual immature neurons are the upstream signaling molecules essential for GABAergic synapse development, which requires signaling via Calmodulin binding motif in the C0 domain of the NMDAR GluN1 subunit. Interestingly, in neurons lacking NMDARs, whereas GABAergic synaptic transmission is strongly reduced, the tonic inhibition mediated by extrasynaptic GABAA receptors is increased, suggesting a compensatory mechanism for the lack of synaptic inhibition. These results demonstrate a crucial role for NMDARs in specifying the development of inhibitory synapses, and suggest an important mechanism for controlling the establishment of the balance between synaptic excitation and inhibition in the developing brain.

  13. Closure mechanisms of ventilated supercavities under steady and unsteady flows

    Science.gov (United States)

    Karn, Ashish; De, Rohan; Hong, Jiarong; Arndt, Roger E. A.

    2015-12-01

    The present work reports some interesting experimental results for ventilated supercavitation in steady and unsteady flows. First, a variety of closure modes obtained as a result of systematic variation in Froude number and air entrainment, are reported. The closure mechanisms were found to differ from the standard criterion reported in the literature. Further, the occurrence of a variety of stable and unstable closure mechanisms were discovered that have not been reported in the literature. Next, a hypothesis is presented to explain the cause behind these different closure mechanisms. The proposed hypothesis is then validated by synchronized high-speed imaging and pressure measurements inside and outside of the supercavity. These measurements show that the supercavity closure is a function of instantaneous cavitation number under unsteady flow conditions. (Research sponsored by Office of Naval Research, USA)

  14. Neural mechanisms underlying morphine withdrawal in addicted patients: a review

    Directory of Open Access Journals (Sweden)

    Nima Babhadiashar

    2015-06-01

    Full Text Available Morphine is one of the most potent alkaloid in opium, which has substantial medical uses and needs and it is the first active principle purified from herbal source. Morphine has commonly been used for relief of moderate to severe pain as it acts directly on the central nervous system; nonetheless, its chronic abuse increases tolerance and physical dependence, which is commonly known as opiate addiction. Morphine withdrawal syndrome is physiological and behavioral symptoms that stem from prolonged exposure to morphine. A majority of brain regions are hypofunctional over prolonged abstinence and acute morphine withdrawal. Furthermore, several neural mechanisms are likely to contribute to morphine withdrawal. The present review summarizes the literature pertaining to neural mechanisms underlying morphine withdrawal. Despite the fact that morphine withdrawal is a complex process, it is suggested that neural mechanisms play key roles in morphine withdrawal.

  15. Analysis of internal crack healing mechanism under rolling deformation.

    Science.gov (United States)

    Gao, Haitao; Ai, Zhengrong; Yu, Hailiang; Wu, Hongyan; Liu, Xianghua

    2014-01-01

    A new experimental method, called the 'hole filling method', is proposed to simulate the healing of internal cracks in rolled workpieces. Based on the experimental results, the evolution in the microstructure, in terms of diffusion, nucleation and recrystallisation were used to analyze the crack healing mechanism. We also validated the phenomenon of segmented healing. Internal crack healing involves plastic deformation, heat transfer and an increase in the free energy introduced by the cracks. It is proposed that internal cracks heal better under high plastic deformation followed by slow cooling after rolling. Crack healing is controlled by diffusion of atoms from the matrix to the crack surface, and also by the nucleation and growth of ferrite grain on the crack surface. The diffusion mechanism is used to explain the source of material needed for crack healing. The recrystallisation mechanism is used to explain grain nucleation and growth, accompanied by atomic migration to the crack surface. PMID:25003518

  16. Optical tests of a space mechanism under an adverse environment: GAIA secondary mirror mechanism under vaccum and thermal controlled conditions

    Science.gov (United States)

    Ramos Zapata, Gonzalo; Sánchez Rodríguez, Antonio; Belenguer Dávila, Tomás; Urgoiti, Eduardo; Ramírez Quintana, Argiñe

    2007-09-01

    In this work, the optical evaluation of a mechanism for space applications under vacuum and temperature controlled conditions at the facilities of the Space Instrumentation Laboratory (LINES) of the Aerospace Technical Nacional Institute of Spain (INTA) is reported. The mechanism was developed by the Spanish company SENER to fulfill the high performance requirements from ESA technology preparatory program for GAIA Astrometric Mission; in particular, a five degrees of freedom (dof), three translations and two rotations positioning mechanism for the secondary mirror of the GAIA instrument. Both interferometric tests and autocollimator measurements have been combined in order to extract the information about the accuracy of the mechanism movements as well as their repeatability under adverse environmental conditions: vacuum and thermal controlled conditions, up to a 10 -6mbar and 100K. The scope of this paper will cover the measurements concept selection, the presentation of verification activities, the results of such dedicated optical measurements, the correlation with the mechanical models and a brief description of the design process followed to meet the test requirements.

  17. Aetiology of thrombosed external haemorrhoids: a questionnaire study

    Directory of Open Access Journals (Sweden)

    Rohde Henning

    2009-10-01

    Full Text Available Abstract Background It is important to better understand the aetiology of thrombosed external haemorrhoids (TEH because recurrence rates are high, prophylaxis is unknown, and optimal therapy is highly debated. Findings We conducted a questionnaire study of individuals with and without TEH. Aetiology was studied by comparison of answers to a questionnaire given to individuals with and without TEH concerning demography, history, and published aetiologic hypotheses. Participants were evaluated consecutively at our institution from March 2004 through August 2005. One hundred forty-eight individuals were enrolled, including 72 patients with TEH and 76 individuals without TEH but with alternative diagnoses, such as a screening colonoscopy or colonic polyps. Out of 38 possible aetiologic factors evaluated, 20 showed no significant bivariate correlation to TEH and were no longer traced, and 16 factors showed a significant bivariate relationship to TEH. By multivariate analysis, six independent variables were found to predict TEH correctly in 79.1% of cases: age of 46 years or younger, use of excessive physical effort, and use of dry toilet paper combined with wet cleaning methods after defaecation were associated with a significantly higher risk of developing TEH; use of bathtub, use of the shower, and genital cleaning before sleep at least once a week were associated with a significantly lower risk of developing TEH. Conclusion Six hypotheses on the causes of TEH have a high probability of being correct and should be considered in future studies on aetiology, prophylaxis, and therapy of TEH.

  18. Giant panda׳s tooth enamel: Structure, mechanical behavior and toughening mechanisms under indentation.

    Science.gov (United States)

    Weng, Z Y; Liu, Z Q; Ritchie, R O; Jiao, D; Li, D S; Wu, H L; Deng, L H; Zhang, Z F

    2016-12-01

    The giant panda׳s teeth possess remarkable load-bearing capacity and damage resistance for masticating bamboos. In this study, the hierarchical structure and mechanical behavior of the giant panda׳s tooth enamel were investigated under indentation. The effects of loading orientation and location on mechanical properties of the enamel were clarified and the evolution of damage in the enamel under increasing load evaluated. The nature of the damage, both at and beneath the indentation surfaces, and the underlying toughening mechanisms were explored. Indentation cracks invariably were seen to propagate along the internal interfaces, specifically the sheaths between enamel rods, and multiple extrinsic toughening mechanisms, e.g., crack deflection/twisting and uncracked-ligament bridging, were active to shield the tips of cracks from the applied stress. The giant panda׳s tooth enamel is analogous to human enamel in its mechanical properties, yet it has superior hardness and Young׳s modulus but inferior toughness as compared to the bamboo that pandas primarily feed on, highlighting the critical roles of the integration of underlying tissues in the entire tooth and the highly hydrated state of bamboo foods. Our objective is that this study can aid the understanding of the structure-mechanical property relations in the tooth enamel of mammals and further provide some insight on the food habits of the giant pandas. PMID:27498423

  19. Investigating the mechanism(s) underlying switching between states in bipolar disorder

    OpenAIRE

    Young, Jared W.; Dulcis, Davide

    2015-01-01

    Bipolar Disorder (BD) is a unique disorder that transcends domains of function since the same patient can exhibit depression or mania, states with polar opposite mood symptoms. During depression, people feel helplessness, reduced energy, and risk aversion, while with mania behaviors include grandiosity, increased energy, less sleep, and risk preference. The neural mechanism(s) underlying each state are gaining clarity, with catecholaminergic disruption seen during mania, and cholinergic dysfu...

  20. Adaptive response: some underlying mechanisms and open questions

    Directory of Open Access Journals (Sweden)

    Evgeniya G. Dimova

    2008-01-01

    Full Text Available Organisms are affected by different DNA damaging agents naturally present in the environment or released as a result of human activity. Many defense mechanisms have evolved in organisms to minimize genotoxic damage. One of them is induced radioresistance or adaptive response. The adaptive response could be considered as a nonspecific phenomenon in which exposure to minimal stress could result in increased resistance to higher levels of the same or to other types of stress some hours later. A better understanding of the molecular mechanism underlying the adaptive response may lead to an improvement of cancer treatment, risk assessment and risk management strategies, radiation protection, e.g. of astronauts during long-term space flights. In this mini-review we discuss some open questions and the probable underlying mechanisms involved in adaptive response: the transcription of many genes and the activation of numerous signaling pathways that trigger cell defenses - DNA repair systems, induction of proteins synthesis, enhanced detoxification of free radicals and antioxidant production.

  1. Large Chip Production Mechanism under the Extreme Load Cutting Conditions

    Institute of Scientific and Technical Information of China (English)

    LIU Xianli; HE Genghuang; YAN Fugang; CHENG Yaonan; LIU Li

    2015-01-01

    There has existed a great deal of theory researches in term of chip production and chip breaking characteristics under conventional cutting and high speed cutting conditions, however, there isn’t sufficient research on chip formation mechanism as well as its influence on cutting state regarding large workpieces under extreme load cutting. This paper presents a model of large saw-tooth chip through applying finite element simulation method, which gives a profound analysis about the characteristics of the extreme load cutting as well as morphology and removal of the large chip. In the meantime, a calculation formula that gives a quantitative description of the saw-tooth level regarding the large chip is established on the basis of cutting experiments on high temperature and high strength steel 2.25Cr-1Mo-0.25V. The cutting experiments are carried out by using the scanning electron microscope and super depth of field electron microscope to measure and calculate the large chip produced under different cutting parameters, which can verify the validity of the established model. The calculating results show that the large saw-toothed chip is produced under the squeezing action between workpiece and cutting tools. In the meanwhile, the chip develops a hardened layer where contacts the cutting tool and the saw-tooth of the chip tend to form in transverse direction. This research creates the theoretical model for large chip and performs the cutting experiments under the extreme load cutting condition, as well as analyzes the production mechanism of the large chip in the macro and micro conditions. Therefore, the proposed research could provide theoretical guidance and technical support in improving productivity and cutting technology research.

  2. Peptide Formation Mechanism on Montmorillonite Under Thermal Conditions

    Science.gov (United States)

    Fuchida, Shigeshi; Masuda, Harue; Shinoda, Keiji

    2014-02-01

    The oligomerization of amino acids is an essential process in the chemical evolution of proteins, which are precursors to life on Earth. Although some researchers have observed peptide formation on clay mineral surfaces, the mechanism of peptide bond formation on the clay mineral surface has not been clarified. In this study, the thermal behavior of glycine (Gly) adsorbed on montmorillonite was observed during heating experiments conducted at 150 °C for 336 h under dry, wet, and dry-wet conditions to clarify the mechanism. Approximately 13.9 % of the Gly monomers became peptides on montmorillonite under dry conditions, with diketopiperazine (cyclic dimer) being the main product. On the other hand, peptides were not synthesized in the absence of montmorillonite. Results of IR analysis showed that the Gly monomer was mainly adsorbed via hydrogen bonding between the positively charged amino groups and negatively charged surface sites (i.e., Lewis base sites) on the montmorillonite surface, indicating that the Lewis base site acts as a catalyst for peptide formation. In contrast, peptides were not detected on montmorillonite heated under wet conditions, since excess water shifted the equilibrium towards hydrolysis of the peptides. The presence of water is likely to control thermodynamic peptide production, and clay minerals, especially those with electrophilic defect sites, seem to act as a kinetic catalyst for the peptide formation reaction.

  3. Mechanisms underlying astringency: introduction to an oral tribology approach

    Science.gov (United States)

    Upadhyay, Rutuja; Brossard, Natalia; Chen, Jianshe

    2016-03-01

    Astringency is one of the predominant factors in the sensory experience of many foods and beverages ranging from wine to nuts. The scientific community is discussing mechanisms that explain this complex phenomenon, since there are no conclusive results which correlate well with sensory astringency. Therefore, the mechanisms and perceptual characteristics of astringency warrant further discussion and investigation. This paper gives a brief introduction of the fundamentals of oral tribology forming a basis of the astringency mechanism. It discusses the current state of the literature on mechanisms underlying astringency describing the existing astringency models. The review discusses the crucial role of saliva and its physiology which contributes significantly in astringency perception in the mouth. It also provides an overview of research concerned with the physiological and psychophysical factors that mediate the perception of this sensation, establishing the ground for future research. Thus, the overall aim of the review is to establish the critical roles of oral friction (thin-film lubrication) in the sensation of astringency and possibly of some other specific sensory features.

  4. Mechanisms underlying KCNQ1channel cell volume sensitivity

    DEFF Research Database (Denmark)

    Hammami, Sofia

    to the process of cell volume adjustments. A great diversity of potassium channels being members of either the 6TM, 4 TM or 2 TM K+ channel gene family have been shown to be strictly regulated by small, fast changes in cell volume. However, the precise mechanism underlying the K+ channel sensitivity to cell...... volume alterations is not yet fully understood. The KCNQ1 channel belonging to the voltage gated KCNQ family is considered a precise sensor of volume changes. The goal of this thesis was to elucidate the mechanism that induces cell volume sensitivity. Until now, a number of investigators have implicitly...... current. It is debated whether this increase in macroscopic current upon expression of KCNQ1 with KCNE1 is due to an increase in ion channel conductance (¿), the open state probability (Po) or an increase in the number of channels in the plasma membrane (N). The latter was quantified by measuring...

  5. Nanomaterial-modulated autophagy: underlying mechanisms and functional consequences.

    Science.gov (United States)

    Zheng, Wei; Wei, Min; Li, Song; Le, Weidong

    2016-06-01

    Autophagy is an essential lysosome-dependent process that controls the quality of the cytoplasm and maintains cellular homeostasis, and dysfunction of this protein degradation system is correlated with various disorders. A growing body of evidence suggests that nanomaterials (NMs) have autophagy-modulating effects, thus predicting a valuable and promising application potential of NMs in the diagnosis and treatment of autophagy-related diseases. NMs exhibit unique physical, chemical and biofunctional properties, which may endow NMs with capabilities to modulate autophagy via various mechanisms. The present review highlights the impacts of various NMs on autophagy and their functional consequences. The possible underlying mechanisms for NM-modulated autophagy are also discussed. PMID:27193191

  6. Quasi-nano wear mechanism under repeated impact contact loading

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    A new quasi-nano wear mechanism (QNWM) has been proposed in this paper based on the facts of wear curve turning under high energy impact contact loading.Its characteristic is that the wear rate of QNWM is only 1/10-1/3 that of delamination mechanism at the same energy density.The diameters of wear debris and pits on the worn surfaces fall into the quasi-nanometer scale (about 50-120 nm).The necessary and sufficient conditions,which bring about the QNWM,are:(i) the nano-structure (nano-crystalline + amorphous phase) in impact contact surface layer has formed by the intensive impact strain;(ii) the delamination wear cracking in sub-surface layer must be restrained;(iii) the microcracks of QNWM are produced in amorphous phase of surface nano-structure layer rather than in nano-crystalline.

  7. Believing versus interacting: Behavioural and neural mechanisms underlying interpersonal coordination

    DEFF Research Database (Denmark)

    Konvalinka, Ivana; Bauer, Markus; Kilner, James;

    When two people engage in a bidirectional interaction with each other, they use both bottom-up sensorimotor mechanisms such as monitoring and adapting to the behaviour of the other, as well as top-down cognitive processes, modulating their beliefs and allowing them to make decisions. Most research...... was measured from one co-actor, with the other co-actor seated outside the scanner. Our findings show frontal alpha suppression during anticipation of the task with a person vs. a computer, and frontal-sensorimotor suppression during task execution with the person vs. computer. This provides insight...... into neural mechanisms underlying belief of interacting with another person as well as engaging in interaction with the responsive other....

  8. Biochemical mechanisms of signaling: perspectives in plants under arsenic stress.

    Science.gov (United States)

    Islam, Ejazul; Khan, Muhammad Tahir; Irem, Samra

    2015-04-01

    Plants are the ultimate food source for humans, either directly or indirectly. Being sessile in nature, they are exposed to various biotic and abiotic stresses because of changing climate that adversely effects their growth and development. Contamination of heavy metals is one of the major abiotic stresses because of anthropogenic as well as natural factors which lead to increased toxicity and accumulation in plants. Arsenic is a naturally occurring metalloid toxin present in the earth crust. Due to its presence in terrestrial and aquatic environments, it effects the growth of plants. Plants can tolerate arsenic using several mechanisms like phytochelation, vacuole sequestration and activation of antioxidant defense systems. Several signaling mechanisms have evolved in plants that involve the use of proteins, calcium ions, hormones, reactive oxygen species and nitric oxide as signaling molecules to cope with arsenic toxicity. These mechanisms facilitate plants to survive under metal stress by activating their defense systems. The pathways by which these stress signals are perceived and responded is an unexplored area of research and there are lots of gaps still to be filled. A good understanding of these signaling pathways can help in raising the plants which can perform better in arsenic contaminated soil and water. In order to increase the survival of plants in contaminated areas there is a strong need to identify suitable gene targets that can be modified according to needs of the stakeholders using various biotechnological techniques. This review focuses on the signaling mechanisms of plants grown under arsenic stress and will give an insight of the different sensory systems in plants. Furthermore, it provides the knowledge about several pathways that can be exploited to develop plant cultivars which are resistant to arsenic stress or can reduce its uptake to minimize the risk of arsenic toxicity through food chain thus ensuring food security.

  9. Study of mechanical properties of nanomaterials under high pressure

    Science.gov (United States)

    Sharma, Jyoti; Kaur, Namrat; Srivastava, A. K.

    2015-08-01

    In the present work, the study of physical properties and behaviour of nanomaterials i.e. n-γ- Al2O3and n-Si3C4 under high pressure is done. For this purpose Murnaghan equation of state is used. The applicability of Murnaghan equation of state is fully tested by calculating mechanical properties of nano materials i.e. volume compression (V/Vo), bulk modulus (KT) and relative isothermal compression coefficient (α(P)/α0) at different pressures. The present calculated values of compression curve for the cited nanomaterials come out to be in reasonable good agreement with the available experimental data.

  10. Genomic interrogation of mechanism(s) underlying cellular responses to toxicants

    International Nuclear Information System (INIS)

    Assessment of the impact of xenobiotic exposure on human health and disease progression is complex. Knowledge of mode(s) of action, including mechanism(s) contributing to toxicity and disease progression, is valuable for evaluating compounds. Toxicogenomics, the subdiscipline which merges genomics with toxicology, holds the promise to contributing significantly toward the goal of elucidating mechanism(s) by studying genome-wide effects of xenobiotics. Global gene expression profiling, revolutionized by microarray technology and a crucial aspect of a toxicogenomic study, allows measuring transcriptional modulation of thousands of genes following exposure to a xenobiotic. We use our results from previous studies on compounds representing two different classes of xenobiotics (barbiturate and peroxisome proliferator) to discuss the application of computational approaches for analyzing microarray data to elucidate mechanism(s) underlying cellular responses to toxicants. In particular, our laboratory demonstrated that chemical-specific patterns of gene expression can be revealed using cDNA microarrays. Transcript profiling provides discrimination between classes of toxicants, as well as, genome-wide insight into mechanism(s) of toxicity and disease progression. Ultimately, the expectation is that novel approaches for predicting xenobiotic toxicity in humans will emerge from such information

  11. Mechanisms Underlying the Antidepressant Response and Treatment Resistance

    Directory of Open Access Journals (Sweden)

    Marjorie Rose Levinstein

    2014-06-01

    Full Text Available Depression is a complex and heterogeneous disorder affecting millions of Americans. There are several different medications and other treatments that are available and effective for many patients with depression. However, a substantial percentage of patients fail to achieve remission with these currently available interventions, and relapse rates are high. Therefore, it is necessary to determine both the mechanisms underlying the antidepressant response and the differences between responders and non-responders to treatment. Delineation of these mechanisms largely relies on experiments that utilize animal models. Therefore, this review provides an overview of the various mouse models that are currently used to assess the antidepressant response, such as chronic mild stress, social defeat, and chronic corticosterone. We discuss how these mouse models can be used to advance our understanding of the differences between responders and non-responders to antidepressant treatment. We also provide an overview of experimental treatment modalities that are used for treatment-resistant depression, such as deep brain stimulation and ketamine administration. We will then review the various genetic polymorphisms and transgenic mice that display resistance to antidepressant treatment. Finally, we synthesize the published data to describe a potential neural circuit underlying the antidepressant response and treatment resistance.

  12. Shared neural mechanisms underlying social warmth and physical warmth.

    Science.gov (United States)

    Inagaki, Tristen K; Eisenberger, Naomi I

    2013-11-01

    Many of people's closest bonds grow out of socially warm exchanges and the warm feelings associated with being socially connected. Indeed, the neurobiological mechanisms underlying thermoregulation may be shared by those that regulate social warmth, the experience of feeling connected to other people. To test this possibility, we placed participants in a functional MRI scanner and asked them to (a) read socially warm and neutral messages from friends and family and (b) hold warm and neutral-temperature objects (a warm pack and a ball, respectively). Findings showed an overlap between physical and social warmth: Participants felt warmer after reading the positive (compared with neutral) messages and more connected after holding the warm pack (compared with the ball). In addition, neural activity during social warmth overlapped with neural activity during physical warmth in the ventral striatum and middle insula, but neural activity did not overlap during another pleasant task (soft touch). Together, these results suggest that a common neural mechanism underlies physical and social warmth. PMID:24048423

  13. Shared neural mechanisms underlying social warmth and physical warmth.

    Science.gov (United States)

    Inagaki, Tristen K; Eisenberger, Naomi I

    2013-11-01

    Many of people's closest bonds grow out of socially warm exchanges and the warm feelings associated with being socially connected. Indeed, the neurobiological mechanisms underlying thermoregulation may be shared by those that regulate social warmth, the experience of feeling connected to other people. To test this possibility, we placed participants in a functional MRI scanner and asked them to (a) read socially warm and neutral messages from friends and family and (b) hold warm and neutral-temperature objects (a warm pack and a ball, respectively). Findings showed an overlap between physical and social warmth: Participants felt warmer after reading the positive (compared with neutral) messages and more connected after holding the warm pack (compared with the ball). In addition, neural activity during social warmth overlapped with neural activity during physical warmth in the ventral striatum and middle insula, but neural activity did not overlap during another pleasant task (soft touch). Together, these results suggest that a common neural mechanism underlies physical and social warmth.

  14. Cell Mechanisms of Bone Tissue Loss Under Space Flight Conditions

    Science.gov (United States)

    Rodionova, Natalia

    Investigations on the space biosatellites has shown that the bone skeleton is one of the most im-portant targets of the effect space flight factors on the organism. Bone tissue cells were studied by electron microscopy in biosamples of rats' long bones flown on the board american station "SLS-2" and in experiments with modelling of microgravity ("tail suspension" method) with using autoradiography. The analysis of data permits to suppose that the processes of remod-eling in bone tissue at microgravity include the following succession of cell-to-cell interactions. Osteocytes as mechanosensory cells are first who respond to a changing "mechanical field". The next stage is intensification of osteolytic processes in osteocytes, leading to a volume en-largement of the osteocytic lacunae and removal of the "excess bone". Then mechanical signals have been transmitted through a system of canals and processes of the osteocytic syncitium to certain superficial bone zones and are perceived by osteoblasts and bone-lining cells (superficial osteocytes), as well as by the bone-marrow stromal cells. The sensitivity of stromal cells, pre-osteoblasts and osteoblasts, under microgravity was shown in a number of works. As a response to microgravity, the system of stromal cells -preosteoblasts -osteoblasts displays retardation of proliferation, differentiation and specific functions of osteogenetic cells. This is supported by the 3H-thymidine studies of the dynamics of differentiation of osteogenetic cells in remodeling zones. But unloading is not adequate and in part of the osteocytes are apoptotic changes as shown by our electron microscopic investigations. An osteocytic apoptosis can play the role in attraction the osteoclasts and in regulation of bone remodeling. The apoptotic bodies with a liquid flow through a system of canals are transferred to the bone surface, where they fulfil the role of haemoattractants for monocytes come here and form osteoclasts. The osteoclasts destroy

  15. Autophagy as a Possible Underlying Mechanism of Nanomaterial Toxicity

    Directory of Open Access Journals (Sweden)

    Vanessa Cohignac

    2014-07-01

    Full Text Available The rapid development of nanotechnologies is raising safety concerns because of the potential effects of engineered nanomaterials on human health, particularly at the respiratory level. Since the last decades, many in vivo studies have been interested in the pulmonary effects of different classes of nanomaterials. It has been shown that some of them can induce toxic effects, essentially depending on their physico-chemical characteristics, but other studies did not identify such effects. Inflammation and oxidative stress are currently the two main mechanisms described to explain the observed toxicity. However, the exact underlying mechanism(s still remain(s unknown and autophagy could represent an interesting candidate. Autophagy is a physiological process in which cytoplasmic components are digested via a lysosomal pathway. It has been shown that autophagy is involved in the pathogenesis and the progression of human diseases, and is able to modulate the oxidative stress and pro-inflammatory responses. A growing amount of literature suggests that a link between nanomaterial toxicity and autophagy impairment could exist. In this review, we will first summarize what is known about the respiratory effects of nanomaterials and we will then discuss the possible involvement of autophagy in this toxicity. This review should help understand why autophagy impairment could be taken as a promising candidate to fully understand nanomaterials toxicity.

  16. Behaviour of bcc technical superconductors under dynamic mechanical stress

    International Nuclear Information System (INIS)

    The behavior of bcc technical superconductors NbTi, NbZr and Nb under dynamic mechanical stress was investigated using two measuring techniques. In shot-sample training experiments the load was measured at which, in wire samples with a transport current applied, normal transitions occured in succesive straining cycles. Complementary, the acoustic emission from superconductors was monitored during strain at 4.2 K. A mechanism based on the formation of a stress induced shear transformation was proposed to account for the training behavior. This partially reversible shearing of the lattice is not sufficient to furnish the required energy for transition in the normal state but it may be detected by means of acoustic emission. On the other hand, a time correlation between acoustic emission and normal transition was found although training behavior and emission responded differently to the same metallurgical treatment. The experiments strongly indicate that the mechanism directly responsible for local energy release is microyielding, induced by the shear transformation. The stress relaxation which accompanies this transformation results in an increased load on the rest of the sample cross-section. Consequently microyielding caused by the transformation could occur in that region of the sample without being detected on the stress-strain curve. This would result in a sufficient release of energy to increase the sample temperature above its critical value. (orig./HP)

  17. Piezoelectric compliant mechanism energy harvesters under large base excitations

    Science.gov (United States)

    Ma, Xiaokun; Trolier-McKinstry, Susan; Rahn, Christopher D.

    2016-09-01

    A piezoelectric compliant mechanism (PCM) energy harvester is designed, modeled, and analyzed that consists of a polyvinylidene diflouoride, PVDF unimorph clamped at its base and attached to a compliant mechanism at its tip. The compliant hinge stiffness is carefully tuned to approach a low frequency first mode with an efficient (nearly quadratic) shape that provides a uniform strain distribution. A nonlinear model of the PCM energy harvester under large base excitation is derived to determine the maximum power that can be generated by the device. Experiments with a fabricated PCM energy harvester prototype show that the compliant mechanism introduces a stiffening effect and a much wider bandwidth than a benchmark proof mass cantilever design. The PCM bridge structure self-limits the displacement and maximum strain at large excitations compared with the proof mass cantilever, improving the device robustness. The PCM outperforms the cantilever in both average power and power-strain sensitivity at high accelerations due to the PCM axial stretching effect and its more uniform strain distribution.

  18. Effects of manual hyperinflation in preterm newborns under mechanical ventilation

    Science.gov (United States)

    Viana, Camila Chaves; Nicolau, Carla Marques; Juliani, Regina Celia Turola Passos; de Carvalho, Werther Brunow; Krebs, Vera Lucia Jornada

    2016-01-01

    Objective To assess the effects of manual hyperinflation, performed with a manual resuscitator with and without the positive end-expiratory pressure valve, on the respiratory function of preterm newborns under mechanical ventilation. Methods Cross-sectional study of hemodynamically stable preterm newborns with gestational age of less than 32 weeks, under mechanical ventilation and dependent on it at 28 days of life. Manual hyperinflation was applied randomly, alternating the use or not of the positive end-expiratory pressure valve, followed by tracheal aspiration for ending the maneuver. For nominal data, the two-tailed Wilcoxon test was applied at the 5% significance level and 80% power. Results Twenty-eight preterm newborns, with an average birth weight of 1,005.71 ± 372.16g, an average gestational age of 28.90 ± 1.79 weeks, an average corrected age of 33.26 ± 1.78 weeks, and an average mechanical ventilation time of 29.5 (15 - 53) days, were studied. Increases in inspiratory and expiratory volumes occurred between time-points A5 (before the maneuver) and C1 (immediately after tracheal aspiration) in both the maneuver with the valve (p = 0.001 and p = 0.009) and without the valve (p = 0.026 and p = 0.001), respectively. There was also an increase in expiratory resistance between time-points A5 and C1 (p = 0.044). Conclusion Lung volumes increased when performing the maneuver with and without the valve, with a significant difference in the first minute after aspiration. There was a significant difference in expiratory resistance between the time-points A5 (before the maneuver) and C1 (immediately after tracheal aspiration) in the first minute after aspiration within each maneuver. PMID:27737427

  19. Molecular Mechanisms Regulating Muscle Fiber Composition Under Microgravity

    Science.gov (United States)

    Rosenthal, Nadia A.

    1999-01-01

    The overall goal of this project is to reveal the molecular mechanisms underlying the selective and debilitating atrophy of specific skeletal muscle fiber types that accompanies sustained conditions of microgravity. Since little is currently known about the regulation of fiber-specific gene expression programs in mammalian muscle, elucidation of the basic mechanisms of fiber diversification is a necessary prerequisite to the generation of therapeutic strategies for attenuation of muscle atrophy on earth or in space. Vertebrate skeletal muscle development involves the fusion of undifferentiated mononucleated myoblasts to form multinucleated myofibers, with a concomitant activation of muscle-specific genes encoding proteins that form the force-generating contractile apparatus. The regulatory circuitry controlling skeletal muscle gene expression has been well studied in a number of vertebrate animal systems. The goal of this project has been to achieve a similar level of understanding of the mechanisms underlying the further specification of muscles into different fiber types, and the role played by innervation and physical activity in the maintenance and adaptation of different fiber phenotypes into adulthood. Our recent research on the genetic basis of fiber specificity has focused on the emergence of mature fiber types and have implicated a group of transcriptional regulatory proteins, known as E proteins, in the control of fiber specificity. The restriction of E proteins to selected muscle fiber types is an attractive hypothetical mechanism for the generation of muscle fiber-specific patterns of gene expression. To date our results support a model wherein different E proteins are selectively expressed in muscle cells to determine fiber-restricted gene expression. These studies are a first step to define the molecular mechanisms responsible for the shifts in fiber type under conditions of microgravity, and to determine the potential importance of E proteins as

  20. [AETIOLOGY AND PATHOGENESIS GASTRO-DUODENALES ULCERATIVE LESIONS IN ELDERLY].

    Science.gov (United States)

    Chernekhovskaya, N E; Povalayev, A V; Layshenko, G A

    2015-01-01

    In review today conceptions of view to aetiology and pathogenesis gastro-duodenales ulcerative lesions in elderly. Atherosclerosis, ischemic disease of the heart and hypertension are reasons of acute ulcers and erosions in elderly. The breaking of microcirculation are very importance.

  1. The aetiology of idiopathic scoliosis : biomechanical and neuromuscular factors

    NARCIS (Netherlands)

    Veldhuizen, AG; Webb, PJ

    2000-01-01

    The aetiology of adolescent idiopathic scoliosis (AIS) remains an enigma. In the literature there are two opinions: one believes a deviating growth pattern is responsible for the condition - patients with AIS lend to be growing faster/be taller - while the other opinion assumes that the growth patte

  2. Worn Down by Toothwear? Aetiology, Diagnosis and Management Revisited.

    Science.gov (United States)

    Yule, Pamela L; Barclay, Stewart C

    2015-01-01

    The incidence of toothwear in the population is increasing, as is the number of referrals regarding this problem to secondary care dental hospital consultants and specialists. This paper outlines current theories in aetiology, diagnosis and management of localized and generalized toothwear, as well as describing clinical tips for assessing such patients.

  3. Exploration of mechanisms underlying the strain-rate-dependent mechanical property of single chondrocytes

    Energy Technology Data Exchange (ETDEWEB)

    Nguyen, Trung Dung; Gu, YuanTong, E-mail: yuantong.gu@qut.edu.au [School of Chemistry, Physics and Mechanical Engineering, Queensland University of Technology, Brisbane, Queensland (Australia)

    2014-05-05

    Based on the characterization by Atomic Force Microscopy, we report that the mechanical property of single chondrocytes has dependency on the strain-rates. By comparing the mechanical deformation responses and the Young's moduli of living and fixed chondrocytes at four different strain-rates, we explore the deformation mechanisms underlying this dependency property. We found that the strain-rate-dependent mechanical property of living cells is governed by both of the cellular cytoskeleton and the intracellular fluid when the fixed chondrocytes are mainly governed by their intracellular fluid, which is called the consolidation-dependent deformation behavior. Finally, we report that the porohyperelastic constitutive material model which can capture the consolidation-dependent behavior of both living and fixed chondrocytes is a potential candidature to study living cell biomechanics.

  4. Conserved Molecular Mechanisms Underlying Homeostasis of the Golgi Complex

    Directory of Open Access Journals (Sweden)

    Cathal Wilson

    2010-01-01

    Full Text Available The Golgi complex performs a central function in the secretory pathway in the sorting and sequential processing of a large number of proteins destined for other endomembrane organelles, the plasma membrane, or secretion from the cell, in addition to lipid metabolism and signaling. The Golgi apparatus can be regarded as a self-organizing system that maintains a relatively stable morphofunctional organization in the face of an enormous flux of lipids and proteins. A large number of the molecular players that operate in these processes have been identified, their functions and interactions defined, but there is still debate about many aspects that regulate protein trafficking and, in particular, the maintenance of these highly dynamic structures and processes. Here, we consider how an evolutionarily conserved underlying mechanism based on retrograde trafficking that uses lipids, COPI, SNAREs, and tethers could maintain such a homeodynamic system.

  5. Mechanisms underlying epithelium-dependent relaxation in rat bronchioles

    DEFF Research Database (Denmark)

    Kroigaard, Christel; Dalsgaard, Thomas; Simonsen, Ulf

    2010-01-01

    This study investigated the mechanisms underlying epithelium-derived hyperpolarizing factor (EpDHF)-type relaxation in rat bronchioles. Immunohistochemistry was performed, and rat bronchioles and pulmonary arteries were mounted in microvascular myographs for functional studies. An opener of small...... (SK(Ca)) and intermediate (IK(Ca))-conductance calcium-activated potassium channels, NS309 (6,7-dichloro-1H-indole-2,3-dione 3-oxime) was used to induce EpDHF-type relaxation. IK(Ca) and SK(Ca)3 positive immunoreactions were observed mainly in the epithelium and endothelium of bronchioles and arteries......, respectively. In 5-hydroxytryptamine (1 microM)-contracted bronchioles (828 +/- 20 microm, n = 84) and U46619 (0.03 microM)-contracted arteries (720 +/- 24 microm, n = 68), NS309 (0.001-10 microM) induced concentration-dependent relaxations that were reduced by epithelium/endothelium removal and by blocking IK...

  6. Mechanisms underlying allergy vaccination with recombinant hypoallergenic allergen derivatives.

    Science.gov (United States)

    Linhart, Birgit; Valenta, Rudolf

    2012-06-19

    Hundred years ago therapeutic vaccination with allergen-containing extracts has been introduced as a clinically effective, disease-modifying, allergen-specific and long-lasting form of therapy for allergy, a hypersensitivity disease affecting more than 25% of the population. Today, the structures of most of the disease-causing allergens have been elucidated and recombinant hypoallergenic allergen derivatives with reduced allergenic activity have been engineered to reduce side effects during allergen-specific immunotherapy (SIT). These recombinant hypoallergens have been characterized in vitro, in experimental animal models and in clinical trials in allergic patients. This review provides a summary of the molecular, immunological and preclinical evaluation criteria applied for this new generation of allergy vaccines. Furthermore, we summarize the mechanisms underlying SIT with recombinant hypoallergens which are thought to be responsible for their therapeutic effect.

  7. Neural mechanisms underlying nicotine addiction: acute positive reinforcement and withdrawal.

    Science.gov (United States)

    Watkins, S S; Koob, G F; Markou, A

    2000-02-01

    The neurobiology of nicotine addiction is reviewed within the context of neurobiological and behavioral theories postulated for other drugs of abuse. The roles of various neurotransmitter systems, including acetylcholine, dopamine, serotonin, glutamate, gamma-aminobutyric acid, and opioid peptides in acute nicotine reinforcement and withdrawal from chronic administration are examined followed by a discussion of potential neuroadaptations within these neurochemical systems that may lead to the development of nicotine dependence. The link between nicotine administration, depression and schizophrenia are also discussed. Finally, a theoretical model of the neurobiological mechanisms underlying acute nicotine withdrawal and protracted abstinence involves alterations within dopaminergic, serotonergic, and stress systems that are hypothesized to contribute to the negative affective state associated with nicotine abstinence.

  8. Data on the mechanisms underlying succinate-induced aortic contraction.

    Science.gov (United States)

    Gonzaga, Natália A; Simplicio, Janaina A; Leite, Letícia N; Vale, Gabriel T; Carballido, José M; Alves-Filho, José C; Tirapelli, Carlos R

    2016-12-01

    We describe the mechanisms underlying the vascular contraction induced by succinate. The data presented here are related to the article entitled "Pharmacological characterization of the mechanisms underlying the vascular effects of succinate" (L.N. Leite, N.A. Gonzaga, J.A. Simplicio, G.T. Vale, J.M. Carballido, J.C. Alves-Filho, C.R. Tirapelli, 2016) [1]. Succinate acts as a signaling molecule by binding to a G-protein-coupled receptor termed GPR91, "Citric acid cycle intermediates as ligands for orphan G-protein-coupled receptors" (W. He, F.J. Miao, D.C. Lin, R.T. Schwandner, Z. Wang, J. Gao, J.L. Chen, H. Tian, L. Ling, 2004) [2]. Here we include data on the contractile effect of succinate in the aorta. Succinate contracted both endothelium-intact and endothelium-denuded aortic rings isolated from male Wistar rats or C57BL/6 mice. Succinate was less effective at inducing contraction in arteries isolated from GPR91-deficient mice, when compared to its vascular effect in aortas from wild type mice. SB203508 (p38MAK inhibitor), SP600125 (JNK inhibitor) and Y27632 (Rho-kinase inhibitor) reduced succinate-induced contraction in both endothelium-intact and endothelium-denuded rat aortic rings, while PD98059 (ERK1/2 inhibitor) did not affect succinate-induced contraction. The contractile response induced by succinate on endothelium-intact and endothelium-denuded rat aortic rings was reduced by indomethacin (non-selective cyclooxygenase inhibitor), H7 (protein kinase C inhibitor), verapamil (Ca(2+) channel blocker) and tiron (superoxide anion scavenger).

  9. Crack arrest saturation model under combined electrical and mechanical loadings

    Directory of Open Access Journals (Sweden)

    R.R. Bhargava

    2009-12-01

    Full Text Available Purpose: The investigation aims at proposing a model for cracked piezoelectric strip which is capable to arrest the crack.Design/methodology/approach: Under the combined effect of electrical and mechanical loadings applied at the edges of the strip, the developed saturation zone is produced at each tip of the crack. To arrest further opening of the crack, the rims of the developed saturation zones are subjected to in-plane cohesive, normal uniform constant saturation point electrical displacement. The problem is solved using Fourier integral transform method which reduces the problem to the solution of Fredholm integral equation of the second kind. This integral equation in turn is solved numerically.Findings: The expressions are derived for different intensity factors and energy release rate. A qualitative analysis of the parameters affecting the arrest of opening of the crack and fatigue crack growth with respect to strip thickness and material constants are presented graphically.Research limitations/implications: The investigations are carried out by considering the material electrical brittle. Consequently, the zones protrude along the straight lines ahead of the crack tips. And further, the small scale electrical yielding conditions are used.Practical implications: Piezoelectric materials are widely getting used nowadays, even in day to day life like piezoelectric cigarette lighter, children toys etc. And, its advance used in technology like transducers, actuators has been already in progress. So, the aspect of cracking of piezoelectric materials are of great practical importance.Originality/value: The piezoelectric material under the combined effect of electrical and mechanical loadings gives the assessment of electrical displacement which is required to arrest the crack. The various useful interpretations are also drawn from the graphs.

  10. POSSIBLE MECHANISMS UNDERLYING THE THERAPEUTIC EFFECTS OF TRANSCRANIAL MAGNETIC STIMULATION

    Directory of Open Access Journals (Sweden)

    Alexander eChervyakov

    2015-06-01

    Full Text Available Transcranial magnetic stimulation (TMS is an effective method used to diagnose and treat many neurological disorders. Although repetitive TMS (rTMS has been used to treat a variety of serious pathological conditions including stroke, depression, Parkinson's disease, epilepsy, pain, and migraines, the pathophysiological mechanisms underlying the effects of long-term TMS remain unclear. In the present review, the effects of rTMS on neurotransmitters and synaptic plasticity are described, including the classic interpretations of TMS effects on synaptic plasticity via long-term potentiation (LTP and long-term depression (LTD. We also discuss the effects of rTMS on the genetic apparatus of neurons, glial cells and the prevention of neuronal death. The neurotrophic effects of rTMS on dendritic growth and sprouting and neurotrophic factors are described, including change in brain-derived neurotrophic factor (BDNF concentration under the influence of rTMS. Also, non-classical effects of TMS related to biophysical effects of magnetic fields are described, including the quantum effects, the magnetic spin effects, genetic magnetoreception, the macromolecular effects of TMS, and the electromagnetic theory of consciousness. Finally, we discuss possible interpretations of TMS effects according to dynamical systems theory. Evidence suggests that a rTMS-induced magnetic field should be considered a separate physical factor that can be impactful at the subatomic level and that rTMS is capable of significantly altering the reactivity of molecules (radicals. It is thought that these factors underlie the therapeutic benefits of therapy with TMS. Future research on these mechanisms will be instrumental to the development of more powerful and reliable TMS treatment protocols.

  11. Mechanisms underlying the social enhancement of vocal learning in songbirds.

    Science.gov (United States)

    Chen, Yining; Matheson, Laura E; Sakata, Jon T

    2016-06-14

    Social processes profoundly influence speech and language acquisition. Despite the importance of social influences, little is known about how social interactions modulate vocal learning. Like humans, songbirds learn their vocalizations during development, and they provide an excellent opportunity to reveal mechanisms of social influences on vocal learning. Using yoked experimental designs, we demonstrate that social interactions with adult tutors for as little as 1 d significantly enhanced vocal learning. Social influences on attention to song seemed central to the social enhancement of learning because socially tutored birds were more attentive to the tutor's songs than passively tutored birds, and because variation in attentiveness and in the social modulation of attention significantly predicted variation in vocal learning. Attention to song was influenced by both the nature and amount of tutor song: Pupils paid more attention to songs that tutors directed at them and to tutors that produced fewer songs. Tutors altered their song structure when directing songs at pupils in a manner that resembled how humans alter their vocalizations when speaking to infants, that was distinct from how tutors changed their songs when singing to females, and that could influence attention and learning. Furthermore, social interactions that rapidly enhanced learning increased the activity of noradrenergic and dopaminergic midbrain neurons. These data highlight striking parallels between humans and songbirds in the social modulation of vocal learning and suggest that social influences on attention and midbrain circuitry could represent shared mechanisms underlying the social modulation of vocal learning.

  12. Using Drosophila to discover mechanisms underlying type 2 diabetes

    Directory of Open Access Journals (Sweden)

    Ronald W. Alfa

    2016-04-01

    Full Text Available Mechanisms of glucose homeostasis are remarkably well conserved between the fruit fly Drosophila melanogaster and mammals. From the initial characterization of insulin signaling in the fly came the identification of downstream metabolic pathways for nutrient storage and utilization. Defects in these pathways lead to phenotypes that are analogous to diabetic states in mammals. These discoveries have stimulated interest in leveraging the fly to better understand the genetics of type 2 diabetes mellitus in humans. Type 2 diabetes results from insulin insufficiency in the context of ongoing insulin resistance. Although genetic susceptibility is thought to govern the propensity of individuals to develop type 2 diabetes mellitus under appropriate environmental conditions, many of the human genes associated with the disease in genome-wide association studies have not been functionally studied. Recent advances in the phenotyping of metabolic defects have positioned Drosophila as an excellent model for the functional characterization of large numbers of genes associated with type 2 diabetes mellitus. Here, we examine results from studies modeling metabolic disease in the fruit fly and compare findings to proposed mechanisms for diabetic phenotypes in mammals. We provide a systematic framework for assessing the contribution of gene candidates to insulin-secretion or insulin-resistance pathways relevant to diabetes pathogenesis.

  13. Thermal stability of nafion membranes under mechanical stress

    Energy Technology Data Exchange (ETDEWEB)

    Quintilii, M.; Struis, R. [Paul Scherrer Inst. (PSI), Villigen (Switzerland)

    1997-06-01

    The feasibility of adequately modified fluoro-ionomer membranes (NAFION{sup R}) is demonstrated for the selective separation of methanol synthesis products from the raw reactor gas at temperatures around 200{sup o}C. For an economically relevant application of this concept on a technical scale the Nafion membranes should be thin ({approx_equal}10 {mu}m) and thermally stable over a long period of time (1-2 years). In cooperation with industry (Methanol Casale SA, Lugano (CH)), we test the thermal stability of Nafion hollow fibers and supported Nafion thin sheet membranes at temperatures between 160 and 200{sup o}C under mechanical stress by applying a gas pressure difference over the membrane surface ({Delta}P{<=} 40 bar). Tests with the hollow fibers revealed that Nafion has visco-elastic properties. Tests with 50 {mu}m thin Nafion sheets supported by a porous metal carrier at 200{sup o}C and {Delta}P=39 bar showed no mechanical defects over a period of 92 days. (author) 5 figs., 4 refs.

  14. Investigating the mechanism(s) underlying switching between states in bipolar disorder.

    Science.gov (United States)

    Young, Jared W; Dulcis, Davide

    2015-07-15

    Bipolar disorder (BD) is a unique disorder that transcends domains of function since the same patient can exhibit depression or mania, states with polar opposite mood symptoms. During depression, people feel helplessness, reduced energy, and risk aversion, while with mania behaviors include grandiosity, increased energy, less sleep, and risk preference. The neural mechanism(s) underlying each state are gaining clarity, with catecholaminergic disruption seen during mania, and cholinergic dysfunction during depression. The fact that the same patient cycles/switches between these states is the defining characteristic of BD however. Of greater importance therefore, is the mechanism(s) underlying cycling from one state - and its associated neural changes - to another, considered the 'holy grail' of BD research. Herein, we review studies investigating triggers that induce switching to these states. By identifying such triggers, researchers can study neural mechanisms underlying each state and importantly how such mechanistic changes can occur in the same subject. Current animal models of this switch are also discussed, from submissive- and dominant-behaviors to kindling effects. Focus however, is placed on how seasonal changes can induce manic and depressive states in BD sufferers. Importantly, changing photoperiod lengths can induce local switches in neurotransmitter expression in normal animals, from increased catecholaminergic expression during periods of high activity, to increased somatostatin and corticotrophin releasing factor during periods of low activity. Identifying susceptibilities to this switch would enable the development of targeted animal models. From animal models, targeted treatments could be developed and tested that would minimize the likelihood of switching. PMID:25814263

  15. Different neurophysiological mechanisms underlying word and rule extraction from speech.

    Directory of Open Access Journals (Sweden)

    Ruth De Diego Balaguer

    Full Text Available The initial process of identifying words from spoken language and the detection of more subtle regularities underlying their structure are mandatory processes for language acquisition. Little is known about the cognitive mechanisms that allow us to extract these two types of information and their specific time-course of acquisition following initial contact with a new language. We report time-related electrophysiological changes that occurred while participants learned an artificial language. These changes strongly correlated with the discovery of the structural rules embedded in the words. These changes were clearly different from those related to word learning and occurred during the first minutes of exposition. There is a functional distinction in the nature of the electrophysiological signals during acquisition: an increase in negativity (N400 in the central electrodes is related to word-learning and development of a frontal positivity (P2 is related to rule-learning. In addition, the results of an online implicit and a post-learning test indicate that, once the rules of the language have been acquired, new words following the rule are processed as words of the language. By contrast, new words violating the rule induce syntax-related electrophysiological responses when inserted online in the stream (an early frontal negativity followed by a late posterior positivity and clear lexical effects when presented in isolation (N400 modulation. The present study provides direct evidence suggesting that the mechanisms to extract words and structural dependencies from continuous speech are functionally segregated. When these mechanisms are engaged, the electrophysiological marker associated with rule-learning appears very quickly, during the earliest phases of exposition to a new language.

  16. Microcracking in composite laminates under thermal and mechanical loading. Thesis

    Science.gov (United States)

    Maddocks, Jason R.

    1995-01-01

    Composites used in space structures are exposed to both extremes in temperature and applied mechanical loads. Cracks in the matrix form, changing the laminate thermoelastic properties. The goal of the present investigation is to develop a predictive methodology to quantify microcracking in general composite laminates under both thermal and mechanical loading. This objective is successfully met through a combination of analytical modeling and experimental investigation. In the analysis, the stress and displacement distributions in the vicinity of a crack are determined using a shear lag model. These are incorporated into an energy based cracking criterion to determine the favorability of crack formation. A progressive damage algorithm allows the inclusion of material softening effects and temperature-dependent material properties. The analysis is implemented by a computer code which gives predicted crack density and degraded laminate properties as functions of any thermomechanical load history. Extensive experimentation provides verification of the analysis. AS4/3501-6 graphite/epoxy laminates are manufactured with three different layups to investigate ply thickness and orientation effects. Thermal specimens are cooled to progressively lower temperatures down to -184 C. After conditioning the specimens to each temperature, cracks are counted on their edges using optical microscopy and in their interiors by sanding to incremental depths. Tensile coupons are loaded monotonically to progressively higher loads until failure. Cracks are counted on the coupon edges after each loading. A data fit to all available results provides input parameters for the analysis and shows them to be material properties, independent of geometry and loading. Correlation between experiment and analysis is generally very good under both thermal and mechanical loading, showing the methodology to be a powerful, unified tool. Delayed crack initiation observed in a few cases is attributed to a

  17. Mechanical Modeling of a WIPP Drum Under Pressure

    Energy Technology Data Exchange (ETDEWEB)

    Smith, Jeffrey A. [Sandia National Laboratories, Albuquerque, NM (United States)

    2014-11-25

    Mechanical modeling was undertaken to support the Waste Isolation Pilot Plant (WIPP) technical assessment team (TAT) investigating the February 14th 2014 event where there was a radiological release at the WIPP. The initial goal of the modeling was to examine if a mechanical model could inform the team about the event. The intention was to have a model that could test scenarios with respect to the rate of pressurization. It was expected that the deformation and failure (inability of the drum to contain any pressure) would vary according to the pressurization rate. As the work progressed there was also interest in using the mechanical analysis of the drum to investigate what would happen if a drum pressurized when it was located under a standard waste package. Specifically, would the deformation be detectable from camera views within the room. A finite element model of a WIPP 55-gallon drum was developed that used all hex elements. Analyses were conducted using the explicit transient dynamics module of Sierra/SM to explore potential pressurization scenarios of the drum. Theses analysis show similar deformation patterns to documented pressurization tests of drums in the literature. The calculated failure pressures from previous tests documented in the literature vary from as little as 16 psi to 320 psi. In addition, previous testing documented in the literature shows drums bulging but not failing at pressures ranging from 69 to 138 psi. The analyses performed for this study found the drums failing at pressures ranging from 35 psi to 75 psi. When the drums are pressurized quickly (in 0.01 seconds) there is significant deformation to the lid. At lower pressurization rates the deformation of the lid is considerably less, yet the lids will still open from the pressure. The analyses demonstrate the influence of pressurization rate on deformation and opening pressure of the drums. Analyses conducted with a substantial mass on top of the closed drum demonstrate that the

  18. Molecular mechanisms underlying progesterone-enhanced breast cancer cell migration.

    Science.gov (United States)

    Wang, Hui-Chen; Lee, Wen-Sen

    2016-01-01

    Progesterone (P4) was demonstrated to inhibit migration in vascular smooth muscle cells (VSMCs), but to enhance migration in T47D breast cancer cells. To investigate the mechanism responsible for this switch in P4 action, we examined the signaling pathway responsible for the P4-induced migration enhancement in breast cancer cell lines, T47D and MCF-7. Here, we demonstrated that P4 activated the cSrc/AKT signaling pathway, subsequently inducing RSK1 activation, which in turn increased phosphorylation of p27 at T198 and formation of the p27pT198-RhoA complex in the cytosol, thereby preventing RhoA degradation, and eventually enhanced migration in T47D cells. These findings were confirmed in the P4-treated MCF-7. Comparing the P4-induced molecular events in between breast cancer cells and VSMCs, we found that P4 increased p27 phosphorylation at T198 in breast cancer cells through RSK1 activation, while P4 increased p27 phosphorlation at Ser10 in VSMCs through KIS activation. P27pT198 formed the complex with RhoA and prevented RhoA degradation in T47D cells, whereas p-p27Ser10 formed the complex with RhoA and caused RhoA degradation in VSMCs. The results of this study highlight the molecular mechanism underlying P4-enhanced breast cancer cell migration, and suggest that RSK1 activation is responsible for the P4-induced migration enhancement in breast cancer cells. PMID:27510838

  19. Mechanisms underlying stage-1 TRPL channel translocation in Drosophila photoreceptors.

    Directory of Open Access Journals (Sweden)

    Minh-Ha Lieu

    Full Text Available BACKGROUND: TRP channels function as key mediators of sensory transduction and other cellular signaling pathways. In Drosophila, TRP and TRPL are the light-activated channels in photoreceptors. While TRP is statically localized in the signaling compartment of the cell (the rhabdomere, TRPL localization is regulated by light. TRPL channels translocate out of the rhabdomere in two distinct stages, returning to the rhabdomere with dark-incubation. Translocation of TRPL channels regulates their availability, and thereby the gain of the signal. Little, however, is known about the mechanisms underlying this trafficking of TRPL channels. METHODOLOGY/PRINCIPAL FINDINGS: We first examine the involvement of de novo protein synthesis in TRPL translocation. We feed flies cycloheximide, verify inhibition of protein synthesis, and test for TRPL translocation in photoreceptors. We find that protein synthesis is not involved in either stage of TRPL translocation out of the rhabdomere, but that re-localization to the rhabdomere from stage-1, but not stage-2, depends on protein synthesis. We also characterize an ex vivo eye preparation that is amenable to biochemical and genetic manipulation. We use this preparation to examine mechanisms of stage-1 TRPL translocation. We find that stage-1 translocation is: induced with ATP depletion, unaltered with perturbation of the actin cytoskeleton or inhibition of endocytosis, and slowed with increased membrane sterol content. CONCLUSIONS/SIGNIFICANCE: Our results indicate that translocation of TRPL out of the rhabdomere is likely due to protein transport, and not degradation/re-synthesis. Re-localization from each stage to the rhabdomere likely involves different strategies. Since TRPL channels can translocate to stage-1 in the absence of ATP, with no major requirement of the cytoskeleton, we suggest that stage-1 translocation involves simple diffusion through the apical membrane, which may be regulated by release of a

  20. Mechanisms underlying reduced fertility in anovular dairy cows.

    Science.gov (United States)

    Santos, J E P; Bisinotto, R S; Ribeiro, E S

    2016-07-01

    Resumption of ovulation after parturition is a coordinated process that involves recoupling of the GH/insulin-like growth factor 1 axis in the liver, increase in follicular development and steroidogenesis, and removal of negative feedback from estradiol in the hypothalamus. Infectious diseases and metabolic disorders associated with extensive negative energy balance during early lactation disrupt this pathway and delay first ovulation postpartum. Extended periods of anovulation postpartum exert long-lasting effects on fertility in dairy cows including the lack of spontaneous estrus, reduced pregnancy per artificial insemination (P/AI), and increased risk of pregnancy loss. Concentrations of progesterone in anovular cows subjected to synchronized programs for AI are insufficient to optimize follicular maturation, oocyte competence, and subsequent fertility to AI. Ovulation of first wave follicles, which develop under low concentrations of progesterone, reduces embryo quality in the first week after fertilization and P/AI in dairy cows. Although the specific mechanisms by which anovulation and low concentrations of progesterone impair oocyte quality have not been defined, studies with persistent follicles support the involvement of premature resumption of meiosis and degradation of maternal RNA. Suboptimal concentrations of progesterone before ovulation also increase the synthesis of PGF2α in response to oxytocin during the subsequent estrous cycle, which explains the greater incidence of short luteal phases after the first AI postpartum in anovular cows compared with estrous cyclic herd mates. It is suggested that increased spontaneous luteolysis early in the estrous cycle is one of the mechanisms that contributes to early embryonic losses in anovular cows. Anovulation also leads to major shifts in gene expression in elongated conceptuses during preimplantation stages of pregnancy. Transcripts involved with control of energy metabolism and DNA repair were

  1. Spallation Mechanism of RC Slabs Under Contact Detonation

    Institute of Scientific and Technical Information of China (English)

    YUAN Lin; GONG Shunfeng; JIN Weiliang

    2008-01-01

    The spallation of the concrete slabs or walls resulting from contact detonation constitutes risk to the personnel and equipment inside the structures because of the high speed concrete fragments even though the overall structures or structural members are not destroyed completely.Correctly predicting the damage caused by any potential contact detonation can lead to better fortification design to withstand the blast Ioadings.It is therefore of great significance to study the mechanism involved in the spallation of concrete slabs and walls.Existing studies on this topic often employ simplified material models and 1D wave analysis, which cannot reproduce the realistic response in the spallation process.Numerical simulations are therefore carried out under different contact blast Ioadings in the free air using LS-DYNA.Sophisticated concrete and reinforcing bar material models are adopted, taking into account the strain rate effect on both tension and compression.The erosion technique is used to model the fracture and failure of materials under tensile stress.Full processes of the deformation and dynamic damage of reinforced concrete (RC) slabs and plain concrete slabs are thus observed realistically.It is noted that with the increase of quantity of explosive, the dimensions of damage crater increase and the slabs experience four different damage patterns, namely explosive crater, spalling, perforation, and punching.Comparison between the simulation results of plain concrete slabs and those of RC slabs show that reinforcing bars can enhance the integrity and shearing resistance of the slabs to a certain extent, and meanwhile attenuate the ejection velocity and decrease the size of the concrete fragments.Therefore,optimizing reinforcement arrangement can improve the anti-spallation capability of the slabs and walls to a certain extent.

  2. Aetiology of childhood viral gastroenteritis in Lucknow, north India

    OpenAIRE

    Shilpi Gupta; Singh, K. P.; Amita Jain; Shilpi Srivastava; Vishwajeet Kumar; Mastan Singh

    2015-01-01

    Background & objectives: Due to limited availability of data on viral aetiology of acute gastroenteritis in north India, the present study was planned to detect rotavirus, norovirus, sapovirus and astrovirus in stool samples of both in hospitalized and non-hospitalized children less than five years of age presenting with acute gastroenteritis. Methods: A total of 278 stool samples from equal number of children were tested for rotavirus antigen using ELISA and for norovirus, sapovirus and...

  3. The role of FKBP5 in cancer aetiology and chemoresistance

    OpenAIRE

    Li, L.; Lou, Z.; Wang, L

    2010-01-01

    FK506 binding protein 51 (FKBP51, also called FKBP5) belongs to a family of immunophilins, FK506 binding proteins (FKBPs). Members of this family are targets for drugs such as rapamycin and cyclosporine. Although FKBP5 shares characteristics with other FKBPs, it also has unique features, especially its role in the regulation of multiple signalling pathways and in tumourigenesis and chemoresistance. In this review, we will focus on the recently discovered role of FKBP5 in cancer aetiology and ...

  4. The aetiology and modification of food preferences in early childhood

    OpenAIRE

    Fildes, A. M.

    2014-01-01

    Poor diet contributes to the global burden of disease and food preferences play an important role, especially for children. Children generally like sweet, energy-dense foods and often dislike vegetables. However, there are considerable individual differences in liking and explanations for this variation remain elusive. This thesis uses data from a UK cohort of twins to examine the aetiology and development of children’s food preferences with the aim of informing effective dietary intervention...

  5. Vulvovaginitis: clinical features, aetiology, and microbiology of the genital tract

    OpenAIRE

    Jaquiery, A; Stylianopoulos, A; Hogg, G; Grover, S

    1999-01-01

    AIM—To clarify the contribution of clinical and environmental factors and infection to the aetiology of vulvovaginitis in premenarchal girls, and to determine clinical indicators of an infectious cause.
DESIGN—It was necessary first to define normal vaginal flora. Cases were 50 premenarchal girls > 2 years old with symptoms of vulvovaginitis; 50 controls were recruited from girls in the same age group undergoing minor or elective surgery.
RESULTS—Interview questionnaire show...

  6. Neural mechanisms underlying the induction and relief of perceptual curiosity.

    Science.gov (United States)

    Jepma, Marieke; Verdonschot, Rinus G; van Steenbergen, Henk; Rombouts, Serge A R B; Nieuwenhuis, Sander

    2012-01-01

    Curiosity is one of the most basic biological drives in both animals and humans, and has been identified as a key motive for learning and discovery. Despite the importance of curiosity and related behaviors, the topic has been largely neglected in human neuroscience; hence little is known about the neurobiological mechanisms underlying curiosity. We used functional magnetic resonance imaging (fMRI) to investigate what happens in our brain during the induction and subsequent relief of perceptual curiosity. Our core findings were that (1) the induction of perceptual curiosity, through the presentation of ambiguous visual input, activated the anterior insula and anterior cingulate cortex (ACC), brain regions sensitive to conflict and arousal; (2) the relief of perceptual curiosity, through visual disambiguation, activated regions of the striatum that have been related to reward processing; and (3) the relief of perceptual curiosity was associated with hippocampal activation and enhanced incidental memory. These findings provide the first demonstration of the neural basis of human perceptual curiosity. Our results provide neurobiological support for a classic psychological theory of curiosity, which holds that curiosity is an aversive condition of increased arousal whose termination is rewarding and facilitates memory.

  7. Neural mechanisms underlying the induction and relief of perceptual curiosity

    Directory of Open Access Journals (Sweden)

    Marieke eJepma

    2012-02-01

    Full Text Available Curiosity is one of the most basic biological drives in both animals and humans, and has been identified as a key motive for learning and discovery. Despite the importance of curiosity and related behaviors, the topic has been largely neglected in human neuroscience; hence little is known about the neurobiological mechanisms underlying curiosity. We used functional magnetic resonance imaging (fMRI to investigate what happens in our brain during the induction and subsequent relief of perceptual curiosity. Our core findings were that (i the induction of perceptual curiosity, through the presentation of ambiguous visual input, activated the anterior insula and anterior cingulate cortex, brain regions sensitive to conflict and arousal; (ii the relief of perceptual curiosity, through visual disambiguation, activated regions of the striatum that have been related to reward processing; and (iii the relief of perceptual curiosity was associated with hippocampal activation and enhanced incidental memory. These findings provide the first demonstration of the neural basis of human perceptual curiosity. Our results provide neurobiological support for a classic psychological theory of curiosity, which holds that curiosity is an aversive condition of increased arousal whose termination is rewarding and facilitates memory.

  8. Beyond membrane channelopathies: alternative mechanisms underlying complex human disease

    Institute of Scientific and Technical Information of China (English)

    Konstantinos Dean BOUDOULAS; Peter J MOHLER

    2011-01-01

    Over the past fifteen years, our understanding of the molecular mechanisms underlying human disease has flourished in large part due to the discovery of gene mutations linked with membrane ion channels and transporters. In fact, ion channel defects ("channelopathies" - the focus of this review series) have been associated with a spectrum of serious human disease phenotypes including cystic fibrosis, cardiac arrhythmia, diabetes, skeletal muscle defects, and neurological disorders. However, we now know that human disease, particularly excitable cell disease, may be caused by defects in non-ion channel polypeptides including in cellular components residing well beneath the plasma membrane. For example, over the past few years, a new class of potentially fatal cardiac arrhythmias has been linked with cytoplasmic proteins that include sub-membrane adapters such as ankyrin-B (ANK2),ankyrin-G (ANK3), and alpha-1 syntrophin, membrane coat proteins including caveolin-3 (CAV3), signaling platforms including yotiao (AKAPg), and cardiac enzymes (GPD1L). The focus of this review is to detail the exciting role of lamins, yet another class of gene products that have provided elegant new insight into human disease.

  9. Cellular mechanisms underlying the interaction between cannabinoid and opioid system.

    Science.gov (United States)

    Parolaro, D; Rubino, T; Viganò, D; Massi, P; Guidali, C; Realini, N

    2010-04-01

    Recently, the presence of functional interaction between the opioid and cannabinoid system has been shown in various pharmacological responses. Although there is an increasing interest for the feasible therapeutic application of a co-administration of cannabinoids and opioids in some disorders (i.e. to manage pain, to modulate immune system and emotions) and the combined use of the two drugs by drug abusers is becoming largely diffuse, only few papers focused on cellular and molecular mechanisms underlying this interaction. This review updates the biochemical and molecular underpinnings of opioid and cannabinoid interaction, both within the central nervous system and periphery. The most convincing theory for the explanation of this reciprocal interaction involves (i) the release of opioid peptides by cannabinoids or endocannabinoids by opioids, (ii) the existence of a direct receptor-receptor interaction when the receptors are co-expressed in the same cells, and (iii) the interaction of their intracellular pathways. Finally, the cannabinoid/opioid interaction might be different in the brain rewarding networks and in those accounting for other pharmacological effects (antinociception, modulation of emotionality and cognitive behavior), as well as between the central nervous system and periphery. Further insights about the cannabinoid/opioid interaction could pave the way for new and promising therapeutic approaches. PMID:20017730

  10. [Molecular mechanisms underlying the formation of neuromuscular junction].

    Science.gov (United States)

    Higuchi, Osamu; Yamanashi, Yuji

    2011-07-01

    The neuromuscular junction (NMJ) is a synapse between a motor neuron and skeletal muscle. The contraction of skeletal muscle is controlled by the neurotransmitter acetylcholine (ACh), which is released from the motor nerve terminal. To achieve efficient neuromuscular transmission, acetylcholine receptors (AChRs) must be densely clustered on the muscle membrane of the NMJ. Failure of AChR clustering is associated with disorders of neuromuscular transmission such as congenital myasthenic syndromes (CMS) and myasthenia gravis (MG). Motoneuronal agrin and muscle-specific receptor tyrosine kinase (MuSK) are known to play essential roles in the formation and maintenance of NMJs in the central region of each muscle. However, it had been unclear how agrin activates MuSK. Recent studies have elucidated the roles of several key molecules, including the cytoplasmic adaptor protein Dok-7 and LDL receptor-related protein 4 (Lrp4), in agrin-induced MuSK activation. Moreover, new evidence indicates that cyclin-dependent kinase 5 (Cdk5) regulates postsynaptic differentiation. In this review, we summarize the latest developments in molecular mechanisms underlying NMJ formation in vertebrates. PMID:21747134

  11. Molecular mechanism underlying promiscuous polyamine recognition by spermidine acetyltransferase.

    Science.gov (United States)

    Sugiyama, Shigeru; Ishikawa, Sae; Tomitori, Hideyuki; Niiyama, Mayumi; Hirose, Mika; Miyazaki, Yuma; Higashi, Kyohei; Murata, Michio; Adachi, Hiroaki; Takano, Kazufumi; Murakami, Satoshi; Inoue, Tsuyoshi; Mori, Yusuke; Kashiwagi, Keiko; Igarashi, Kazuei; Matsumura, Hiroyoshi

    2016-07-01

    Spermidine acetyltransferase (SAT) from Escherichia coli, which catalyses the transfer of acetyl groups from acetyl-CoA to spermidine, is a key enzyme in controlling polyamine levels in prokaryotic cells. In this study, we determined the crystal structure of SAT in complex with spermidine (SPD) and CoA at 2.5Å resolution. SAT is a dodecamer organized as a hexamer of dimers. The secondary structural element and folding topology of the SAT dimer resemble those of spermidine/spermine N(1)-acetyltransferase (SSAT), suggesting an evolutionary link between SAT and SSAT. However, the polyamine specificity of SAT is distinct from that of SSAT and is promiscuous. The SPD molecule is also located at the inter-dimer interface. The distance between SPD and CoA molecules is 13Å. A deep, highly acidic, water-filled cavity encompasses the SPD and CoA binding sites. Structure-based mutagenesis and in-vitro assays identified SPD-bound residues, and the acidic residues lining the walls of the cavity are mostly essential for enzymatic activities. Based on mutagenesis and structural data, we propose an acetylation mechanism underlying promiscuous polyamine recognition for SAT. PMID:27163532

  12. Deciphering molecular mechanism underlying hypolipidemic activity of echinocystic Acid.

    Science.gov (United States)

    Han, Li; Lai, Peng; Du, Jun-Rong

    2014-01-01

    Our previous study showed that a triterpene mixture, consisting of echinocystic acid (EA) and oleanolic acid (OA) at a ratio of 4 : 1, dose-dependently ameliorated the hyperlipidemia and atherosclerosis in rabbits fed with high fat/high cholesterol diets. This study was aimed at exploring the mechanisms underlying antihyperlipidemic effect of EA. Molecular docking simulation of EA was performed using Molegro Virtual Docker (version: 4.3.0) to investigate the potential targets related to lipid metabolism. Based on the molecular docking information, isotope labeling method or spectrophotometry was applied to examine the effect of EA on the activity of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase, acyl-CoA:cholesterol acyltransferase (ACAT), and diacylglycerol acyltransferase (DGAT) in rat liver microsomes. Our results revealed a strong affinity of EA towards ACAT and DGAT in molecular docking analysis, while low binding affinity existed between EA and HMG-CoA reductase as well as between EA and cholesteryl ester transfer protein. Consistent with the results of molecular docking, in vitro enzyme activity assays showed that EA inhibited ACAT and DGAT, with IC50 values of 103 and 139  μ M, respectively, and exhibited no significant effect on HMG-CoA reductase activity. The present findings suggest that EA may exert hypolipidemic effect by inhibiting the activity of ACAT and DGAT. PMID:24669228

  13. Deciphering Molecular Mechanism Underlying Hypolipidemic Activity of Echinocystic Acid

    Directory of Open Access Journals (Sweden)

    Li Han

    2014-01-01

    Full Text Available Our previous study showed that a triterpene mixture, consisting of echinocystic acid (EA and oleanolic acid (OA at a ratio of 4 : 1, dose-dependently ameliorated the hyperlipidemia and atherosclerosis in rabbits fed with high fat/high cholesterol diets. This study was aimed at exploring the mechanisms underlying antihyperlipidemic effect of EA. Molecular docking simulation of EA was performed using Molegro Virtual Docker (version: 4.3.0 to investigate the potential targets related to lipid metabolism. Based on the molecular docking information, isotope labeling method or spectrophotometry was applied to examine the effect of EA on the activity of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA reductase, acyl-CoA:cholesterol acyltransferase (ACAT, and diacylglycerol acyltransferase (DGAT in rat liver microsomes. Our results revealed a strong affinity of EA towards ACAT and DGAT in molecular docking analysis, while low binding affinity existed between EA and HMG-CoA reductase as well as between EA and cholesteryl ester transfer protein. Consistent with the results of molecular docking, in vitro enzyme activity assays showed that EA inhibited ACAT and DGAT, with IC50 values of 103 and 139 μM, respectively, and exhibited no significant effect on HMG-CoA reductase activity. The present findings suggest that EA may exert hypolipidemic effect by inhibiting the activity of ACAT and DGAT.

  14. Molecular mechanisms underlying phosphate sensing, signaling, and adaptation in plants

    Institute of Scientific and Technical Information of China (English)

    Zhaoliang Zhang; Hong Liao; William J. Lucas

    2014-01-01

    As an essential plant macronutrient, the low availability of phosphorus (P) in most soils imposes serious limitation on crop production. Plants have evolved complex responsive and adaptive mechanisms for acquisition, remobiliza-tion and recycling of phosphate (Pi) to maintain P homeostasis. Spatio-temporal molecular, physiological, and biochemical Pi deficiency responses developed by plants are the consequence of local and systemic sensing and signaling pathways. Pi deficiency is sensed local y by the root system where hormones serve as important signaling components in terms of develop-mental reprogramming, leading to changes in root system architecture. Root-to-shoot and shoot-to-root signals, delivered through the xylem and phloem, respectively, involving Pi itself, hormones, miRNAs, mRNAs, and sucrose, serve to coordinate Pi deficiency responses at the whole-plant level. A combination of chromatin remodeling, transcriptional and posttranslational events contribute to global y regulating a wide range of Pi deficiency responses. In this review, recent advances are evaluated in terms of progress toward developing a comprehen-sive understanding of the molecular events underlying control over P homeostasis. Application of this knowledge, in terms of developing crop plants having enhanced attributes for P use efficiency, is discussed from the perspective of agricultural sustainability in the face of diminishing global P supplies.

  15. CFRP Mechanical Anchorage for Externally Strengthened RC Beams under Flexure

    Science.gov (United States)

    Ali, Alnadher; Abdalla, Jamal; Hawileh, Rami; Galal, Khaled

    De-bonding of carbon fiber reinforced polymers (CFRP) sheets and plates from the concrete substrate is one of the major reasons behind premature failures of beams that are externally strengthened with such CFRP materials. To delay or prevent de-bonding and therefore enhancing the load carrying capacity of strengthened beams, several anchorage systems were developed and used. This paper investigates the use of CFRP mechanical anchorage of CFRP sheets and plates used to externally strengthen reinforced concrete beams under flexure. The pin-and-fan shape CFRP anchor, which is custom-made from typical rolled fiber sheets and bundles of loose fiber is used. Several reinforced concrete beams were casted and tested in standard four-point bending scheme to study the effectiveness of this anchorage system. The beams were externally strengthened in flexure with bonded CFRP sheets and plates and then fastened to the soffit of the beams' using various patterns of CFRP anchors. It is observed that the CFRP plates begins to separate from the beams as soon as de-bonding occurs in specimens without CFRP anchors, while in beams with CFRP anchors de-bonding was delayed leading to increase in the load carrying capacity over the un-anchored strengthened beams.

  16. Spinal cord ischemia: aetiology, clinical syndromes and imaging features

    Energy Technology Data Exchange (ETDEWEB)

    Weidauer, Stefan [Frankfurt Univ., Sankt Katharinen Hospital Teaching Hospital, Frankfurt am Main (Germany). Dept. of Neurology; Hattingen, Elke; Berkefeld, Joachim [Frankfurt Univ., Frankfurt am Main (Germany). Inst. of Neuroradiology; Nichtweiss, Michael

    2015-03-01

    The purpose of this study was to analyse MR imaging features and lesion patterns as defined by compromised vascular territories, correlating them to different clinical syndromes and aetiological aspects. In a 19.8-year period, clinical records and magnetic resonance imaging (MRI) features of 55 consecutive patients suffering from spinal cord ischemia were evaluated. Aetiologies of infarcts were arteriosclerosis of the aorta and vertebral arteries (23.6 %), aortic surgery or interventional aneurysm repair (11 %) and aortic and vertebral artery dissection (11 %), and in 23.6 %, aetiology remained unclear. Infarcts occurred in 38.2 % at the cervical and thoracic level, respectively, and 49 % of patients suffered from centromedullar syndrome caused by anterior spinal artery ischemia. MRI disclosed hyperintense pencil-like lesion pattern on T2WI in 98.2 %, cord swelling in 40 %, enhancement on post-contrast T1WI in 42.9 % and always hyperintense signal on diffusion-weighted imaging (DWI) when acquired. The most common clinical feature in spinal cord ischemia is a centromedullar syndrome, and in contrast to anterior spinal artery ischemia, infarcts in the posterior spinal artery territory are rare. The exclusively cervical location of the spinal sulcal artery syndrome seems to be a likely consequence of anterior spinal artery duplication which is observed preferentially here. (orig.)

  17. Mechanism of crack initiation and crack growth under thermal and mechanical fatigue loading

    Energy Technology Data Exchange (ETDEWEB)

    Utz, S.; Soppa, E.; Silcher, H.; Kohler, C. [Stuttgart Univ. (Germany). Materials Testing Inst.

    2013-07-01

    The present contribution is focused on the experimental investigations and numerical simulations of the deformation behaviour and crack development in the austenitic stainless steel X6CrNiNb18-10 under thermal and mechanical cyclic loading in HCF and LCF regimes. The main objective of this research is the understanding of the basic mechanisms of fatigue damage and the development of simulation methods, which can be applied further in safety evaluations of nuclear power plant components. In this context the modelling of crack initiation and crack growth inside the material structure induced by varying thermal or mechanical loads are of particular interest. The mechanisms of crack initiation depend among other things on the type of loading, microstructure, material properties and temperature. The Nb-stabilized austenitic stainless steel in the solution-annealed condition was chosen for the investigations. Experiments with two kinds of cyclic loading - pure thermal and pure mechanical - were carried out and simulated. The fatigue behaviour of the steel X6CrNiNb18-10 under thermal loading was studied within the framework of the joint research project [4]. Interrupted thermal cyclic tests in the temperature range of 150 C to 300 C combined with non-destructive residual stress measurements (XRD) and various microscopic investigations, e.g. in SEM (Scanning Electron Microscope), were used to study the effects of thermal cyclic loading on the material. This thermal cyclic loading leads to thermal induced stresses and strains. As a result intrusions and extrusions appear inside the grains (at the surface), at which microcracks arise and evolve to a dominant crack. Finally, these microcracks cause a continuous and significant decrease of residual stresses. The fatigue behaviour of the steel X6CrNiNb18-10 under mechanical loading at room temperature was studied within the framework of the research project [5], [8]. With a combination of interrupted LCF tests and EBSD

  18. Mechanism of crack initiation and crack growth under thermal and mechanical fatigue loading

    International Nuclear Information System (INIS)

    The present contribution is focused on the experimental investigations and numerical simulations of the deformation behaviour and crack development in the austenitic stainless steel X6CrNiNb18-10 under thermal and mechanical cyclic loading in HCF and LCF regimes. The main objective of this research is the understanding of the basic mechanisms of fatigue damage and the development of simulation methods, which can be applied further in safety evaluations of nuclear power plant components. In this context the modelling of crack initiation and crack growth inside the material structure induced by varying thermal or mechanical loads are of particular interest. The mechanisms of crack initiation depend among other things on the type of loading, microstructure, material properties and temperature. The Nb-stabilized austenitic stainless steel in the solution-annealed condition was chosen for the investigations. Experiments with two kinds of cyclic loading - pure thermal and pure mechanical - were carried out and simulated. The fatigue behaviour of the steel X6CrNiNb18-10 under thermal loading was studied within the framework of the joint research project [4]. Interrupted thermal cyclic tests in the temperature range of 150 C to 300 C combined with non-destructive residual stress measurements (XRD) and various microscopic investigations, e.g. in SEM (Scanning Electron Microscope), were used to study the effects of thermal cyclic loading on the material. This thermal cyclic loading leads to thermal induced stresses and strains. As a result intrusions and extrusions appear inside the grains (at the surface), at which microcracks arise and evolve to a dominant crack. Finally, these microcracks cause a continuous and significant decrease of residual stresses. The fatigue behaviour of the steel X6CrNiNb18-10 under mechanical loading at room temperature was studied within the framework of the research project [5], [8]. With a combination of interrupted LCF tests and EBSD

  19. Antioxidant Property of Jobelyn as the Possible Mechanism Underlying

    Directory of Open Access Journals (Sweden)

    Solomon Umukoro

    2013-01-01

    Full Text Available   Introduction: Amnesia or loss of memory is the cardinal hallmark of Alzheimer’s disease (AD, a progressive neurodegenerative disorder associated with ageing process. Although, AD had been discovered over a century ago, drugs which could cure or halt the progression of the disease are yet to see the light of the day. However, there has been a growing interest in the use of phytomedicines with multipronged mechanisms of action that could target various aspects of the pathologies of AD. Jobelyn (JB is a potent antioxidant African polyherbal formulation with active components that have been acclaimed to show neuroprotection. T his investigation was carried out to evaluate whether JB has anti-amnesic and antioxidant activities.   Methods: The alteration of alternation behavior in the Y-maze paradigm was utilized as the test for memory function in mice. The effect of JB on a cetylcholinesterase (AChE activity, malondialdehyde (MDA level and the concentrations of glutathione (GSH in the frontal cortex and hippocampus were assessed in rats as means of providing insight into the mechanism underlying its anti-amnesic activity. The animals were given JB (1, 2.5 or 5mg/kg, i.p. daily for 7 days before the biochemical assays or test for memory functions were carried out.   Results: JB was found to produce a significant increase in the level of alternation behavior compared with the control, suggesting anti-amnesic activity. Also, JB reversed the memory impairment induced by scopolamine, which further indicates anti-amnesic property. Furthermore, JB demonstrated a significant inhibition of MDA formation in the frontal cortex and hippocampus of rats, indicating antioxidant property. In addition, it increased the defense armory of the brain tissues, as it significantly increased the concentrations of GSH in the frontal cortex and hippocampus of rats. However, JB did not demonstrate any inhibitory effect against AChE activity in the frontal cortex and

  20. Alteration mechanisms of UOX spent fuel under water

    International Nuclear Information System (INIS)

    The mechanisms of spent fuel alteration in aqueous media need to be understood on the assumption of a direct disposal of the assemblies in a geological formation or for long duration storage in pool. This work is a contribution to the study of the effects of the alpha and/or beta/gamma radiolysis of water on the oxidation and the dissolution of the UO2 matrix of UOX spent fuel. The effects of the alpha radiolysis, predominant in geological disposal conditions, were quantified by using samples of UO2 doped with plutonium. The leaching experiments highlighted two types of control for the matrix alteration according to the alpha activity. The first is based on the radiolytic oxidation of the surface and leads to a continuous release of uranium in solution whereas the second is based on a control by the solubility of uranium. An activity threshold, between 18 MBq.g-1 and 33 MBq.g-1, was defined in a carbonated water. The value of this threshold is dependent on the experimental conditions and the presence or not of electro-active species such as hydrogen in the system. The effects of the alpha/beta/gamma radiolysis in relation with the storage conditions were also quantified. The experimental data obtained on spent fuel indicate that the alteration rate of the matrix based on the behaviour of tracer elements (caesium and strontium) reached a maximum value of some mg.m-2.d-1, even under very oxidizing conditions. The solubility of uranium and the nature of the secondary phases depend however on the extent of the oxidizing conditions. (author)

  1. Unraveling the Molecular Mechanisms Underlying the Nasopharyngeal Bacterial Community Structure.

    Science.gov (United States)

    de Steenhuijsen Piters, Wouter A A; Bogaert, Debby

    2016-01-01

    The upper respiratory tract is colonized by a diverse array of commensal bacteria that harbor potential pathogens, such as Streptococcus pneumoniae. As long as the local microbial ecosystem-also called "microbiome"-is in balance, these potentially pathogenic bacterial residents cause no harm to the host. However, similar to macrobiological ecosystems, when the bacterial community structure gets perturbed, potential pathogens can overtake the niche and cause mild to severe infections. Recent studies using next-generation sequencing show that S. pneumoniae, as well as other potential pathogens, might be kept at bay by certain commensal bacteria, including Corynebacterium and Dolosigranulum spp. Bomar and colleagues are the first to explore a specific biological mechanism contributing to the antagonistic interaction between Corynebacterium accolens and S. pneumoniae in vitro [L. Bomar, S. D. Brugger, B. H. Yost, S. S. Davies, K. P. Lemon, mBio 7(1):e01725-15, 2016, doi:10.1128/mBio.01725-15]. The authors comprehensively show that C. accolens is capable of hydrolyzing host triacylglycerols into free fatty acids, which display antipneumococcal properties, suggesting that these bacteria might contribute to the containment of pneumococcus. This work exemplifies how molecular epidemiological findings can lay the foundation for mechanistic studies to elucidate the host-microbe and microbial interspecies interactions underlying the bacterial community structure. Next, translation of these results to an in vivo setting seems necessary to unveil the magnitude and importance of the observed effect in its natural, polymicrobial setting. PMID:26838716

  2. Unraveling the Molecular Mechanisms Underlying the Nasopharyngeal Bacterial Community Structure

    Directory of Open Access Journals (Sweden)

    Wouter A. A. de Steenhuijsen Piters

    2016-03-01

    Full Text Available The upper respiratory tract is colonized by a diverse array of commensal bacteria that harbor potential pathogens, such as Streptococcus pneumoniae. As long as the local microbial ecosystem—also called “microbiome”—is in balance, these potentially pathogenic bacterial residents cause no harm to the host. However, similar to macrobiological ecosystems, when the bacterial community structure gets perturbed, potential pathogens can overtake the niche and cause mild to severe infections. Recent studies using next-generation sequencing show that S. pneumoniae, as well as other potential pathogens, might be kept at bay by certain commensal bacteria, including Corynebacterium and Dolosigranulum spp. Bomar and colleagues are the first to explore a specific biological mechanism contributing to the antagonistic interaction between Corynebacterium accolens and S. pneumoniae in vitro [L. Bomar, S. D. Brugger, B. H. Yost, S. S. Davies, K. P. Lemon, mBio 7(1:e01725-15, 2016, doi:10.1128/mBio.01725-15]. The authors comprehensively show that C. accolens is capable of hydrolyzing host triacylglycerols into free fatty acids, which display antipneumococcal properties, suggesting that these bacteria might contribute to the containment of pneumococcus. This work exemplifies how molecular epidemiological findings can lay the foundation for mechanistic studies to elucidate the host-microbe and microbial interspecies interactions underlying the bacterial community structure. Next, translation of these results to an in vivo setting seems necessary to unveil the magnitude and importance of the observed effect in its natural, polymicrobial setting.

  3. Mechanisms underlying the link between cannabis use and prospective memory.

    Directory of Open Access Journals (Sweden)

    Carrie Cuttler

    Full Text Available While the effects of cannabis use on retrospective memory have been extensively examined, only a limited number of studies have focused on the links between cannabis use and prospective memory. We conducted two studies to examine the links between cannabis use and both time-based and event-based prospective memory as well as potential mechanisms underlying these links. For the first study, 805 students completed an online survey designed to assess cannabis consumption, problems with cannabis use indicative of a disorder, and frequency of experiencing prospective memory failures. The results showed small to moderate sized correlations between cannabis consumption, problems with cannabis use, and prospective memory. However, a series of mediation analyses revealed that correlations between problems with cannabis use and prospective memory were driven by self-reported problems with retrospective memory. For the second study, 48 non-users (who had never used cannabis, 48 experimenters (who had used cannabis five or fewer times in their lives, and 48 chronic users (who had used cannabis at least three times a week for one year were administered three objective prospective memory tests and three self-report measures of prospective memory. The results revealed no objective deficits in prospective memory associated with chronic cannabis use. In contrast, chronic cannabis users reported experiencing more internally-cued prospective memory failures. Subsequent analyses revealed that this effect was driven by self-reported problems with retrospective memory as well as by use of alcohol and other drugs. Although our samples were not fully characterized with respect to variables such as neurological disorders and family history of substance use disorders, leaving open the possibility that these variables may play a role in the detected relationships, the present findings indicate that cannabis use has a modest effect on self-reported problems with

  4. Neural Mechanisms Underlying Compensatory and Noncompensatory Strategies in Risky Choice.

    Science.gov (United States)

    Van Duijvenvoorde, Anna C K; Figner, Bernd; Weeda, Wouter D; Van der Molen, Maurits W; Jansen, Brenda R J; Huizenga, Hilde M

    2016-09-01

    Individuals may differ systematically in their applied decision strategies, which has critical implications for decision neuroscience but is yet scarcely studied. Our study's main focus was therefore to investigate the neural mechanisms underlying compensatory versus noncompensatory strategies in risky choice. Here, we compared people using a compensatory expected value maximization with people using a simplified noncompensatory loss-minimizing choice strategy. To this end, we used a two-choice paradigm including a set of "simple" items (e.g., simple condition), in which one option was superior on all attributes, and a set of "conflict" items, in which one option was superior on one attribute but inferior on other attributes. A binomial mixture analysis of the decisions elicited by these items differentiated between decision-makers using either a compensatory or a noncompensatory strategy. Behavioral differences were particularly pronounced in the conflict condition, and these were paralleled by neural results. That is, we expected compensatory decision-makers to use an integrated value comparison during choice in the conflict condition. Accordingly, the compensatory group tracked the difference in expected value between choice options reflected in neural activation in the parietal cortex. Furthermore, we expected noncompensatory, compared with compensatory, decision-makers to experience increased conflict when attributes provided conflicting information. Accordingly, the noncompensatory group showed greater dorsomedial PFC activation only in the conflict condition. These pronounced behavioral and neural differences indicate the need for decision neuroscience to account for individual differences in risky choice strategies and to broaden its scope to noncompensatory risky choice strategies. PMID:27167399

  5. Cognitive mechanisms underlying instructed choice exploration of small city maps

    Directory of Open Access Journals (Sweden)

    Sofia eSakellaridi

    2015-03-01

    Full Text Available We investigated the cognitive mechanisms underlying the exploration and decision-making in realistic and novel environments. Twelve human subjects were shown small circular U.S. city maps with two locations highlighted on the circumference, as possible choices for a post office (targets. At the beginning of a trial, subjects fixated a spot at the center of the map and ultimately chose one of the two locations. A space syntax analysis of the map paths (from the center to each target revealed that the chosen location was associated with the less convoluted path, as if subjects navigated mentally the paths in an ant’s way, i.e. by staying within street boundaries, and ultimately choosing the target that could be reached from the center in the shortest way, and the fewest turns and intersections. The subjects’ strategy for map exploration and decision making was investigated by monitoring eye position during the task. This revealed a restricted exploration of the map delimited by the location of the two alternative options and the center of the map. Specifically, subjects explored the areas around the two target options by repeatedly looking at them before deciding which one to choose, presumably implementing an evaluation and decision-making process. The ultimate selection of a specific target was significantly associated with the time spent exploring the area around that target. Finally, an analysis of the sequence of eye fixations revealed that subjects tended to look systematically towards the target ultimately chosen even from the beginning of the trial. This finding indicates an early cognitive selection bias for the ensuing decision process.

  6. [Neural mechanism underlying autistic savant and acquired savant syndrome].

    Science.gov (United States)

    Takahata, Keisuke; Kato, Motoichiro

    2008-07-01

    , especially that of the prefrontal cortex and the posterior regions of the brain. (3) Autistic models, including those based on weak central coherence theory (Frith, 1989), that focus on how savant skills emerge from an autistic brain. Based on recent neuroimaging studies of ASD, Just et al. (2004) suggested the underconnectivity theory, which emphasizes the disruption of long-range connectivity and the relative intact or even more enhanced local connectivity in the autistic brain. All the models listed above have certain advantages and shortcomings. At the end of this review, we propose another integrative model of savant syndrome. In this model, we predict an altered balance of local/global connectivity patterns that contribute to an altered functional segregation/integration ratio. In particular, we emphasize the crucial role played by the disruption of global connectivity in a parallel distributed cortical network, which might result in impairment in integrated cognitive processing, such as impairment in executive function and social cognition. On the other hand, the reduced inter-regional collaboration could lead to a disinhibitory enhancement of neural activity and connectivity in local cortical regions. In addition, enhanced connectivity in the local brain regions is partly due to the abnormal organization of the cortical network as a result of developmental and pathological states. This enhanced local connectivity results in the specialization and facilitation of low-level cognitive processing. The disruption of connectivity between the prefrontal cortex and other regions is considered to be a particularly important factor because the prefrontal region shows the most influential inhibitory control on other cortical areas. We propose that these neural mechanisms as the underlying causes for the emergence of savant ability in ASD and FTD patients.

  7. The utility of the polymerase chain reaction assay for aetiologic definition of unspecified bacterial meningitis cases

    Directory of Open Access Journals (Sweden)

    Mari Tuyama

    2008-03-01

    Full Text Available Most patients with acute suppurative meningitis are otherwise healthy individuals with regard to immune mechanisms against invasive bacterial disease. This medical emergency is among the most dramatic and potentially ravaging diseases that affect humans, particularly young children. The illness often strikes suddenly, and can either result in death or leave the survivors with significant neurological dysfunctions. The demonstration of a bacterial aetiology is necessary for decisions regarding treatment and prophylaxis. Conventional bacteriological methods frequently fail to identify an agent, as a result of administration of antibiotics or delayed lumbar punctures. We investigated the major aetiologic sources of unspecified bacterial meningitis cases (G00.9, ISCD-10 by polymerase chain reaction (PCR-based identification of Neisseria meningitidis (crgA, Streptococcus pneumoniae (ply and Haemophilus influenzae (bexA in cerebrospinal fluid samples. The multiplex PCR detected N. meningitidis in 92%, S. pneumoniae in 4% and H. influenzae in 1% of the 192 clinical samples assayed; 3% were negative for all three DNA targets. Bacterial DNA detection was found to be a valuable adjunct to enhance bacterial meningitis surveillance when the yield of specimens by culture is reduced. The implementation of PCR assays as a diagnostic procedure in Public Health Laboratories is perceived to be a significant advance in the investigation of bacterial meningitis.

  8. Epigenetic mechanisms underlying learning and the inheritance of learned behaviors.

    Science.gov (United States)

    Dias, Brian G; Maddox, Stephanie A; Klengel, Torsten; Ressler, Kerry J

    2015-02-01

    Gene expression and regulation is an important sculptor of the behavior of organisms. Epigenetic mechanisms regulate gene expression not by altering the genetic alphabet but rather by the addition of chemical modifications to proteins associated with the alphabet or of methyl marks to the alphabet itself. Being dynamic, epigenetic mechanisms of gene regulation serve as an important bridge between environmental stimuli and genotype. In this review, we outline epigenetic mechanisms by which gene expression is regulated in animals and humans. Using fear learning as a framework, we then delineate how such mechanisms underlie learning and stress responsiveness. Finally, we discuss how epigenetic mechanisms might inform us about the transgenerational inheritance of behavioral traits that are being increasingly reported.

  9. Mechanisms and pharmacogenetic signals underlying thiazide diuretics blood pressure response.

    Science.gov (United States)

    Shahin, Mohamed H; Johnson, Julie A

    2016-04-01

    Thiazide (TZD) diuretics are among the most commonly prescribed antihypertensives globally; however their chronic blood pressure (BP) lowering mechanism remains unclear. Herein we discuss the current evidence regarding specific mechanisms regulating the antihypertensive effects of TZDs, suggesting that TZDs act via multiple complex and interacting mechanisms, including natriuresis with short term use and direct vasodilatory effects chronically. Additionally, we review pharmacogenomics signals that have been associated with TZDs BP-response in several cohorts (i.e. NEDD4L, PRKCA, EDNRA-GNAS, and YEATS4) and discuss how these genes might be related to TZD BP-response mechanism. Understanding the association between these genes and TZD BP mechanism might facilitate the development of new drugs and therapeutic approaches based on a deeper understanding of the determinants of BP-response.

  10. Aetiology and Outcome of Acute Liver Failure in Children: Experience at a Tertiary Care Hospital of Bangladesh.

    Science.gov (United States)

    Mazumder, M W; Karim, A B; Rukunuzzaman, M; Rahman, M A

    2016-07-01

    Acute liver failure (ALF) is a rapidly progressive, potentially fatal syndrome resulting from rapid death or injury to a large proportion of hepatocytes, caused by a variety of insult, leaving insufficient hepatic paranchymal mass to sustain liver function. The aetiology of ALF varies according to the age of patient and development of the country. The outcome of ALF also varies according to aetiology: survival is better in paracetamol poisoning whereas it is poor in metabolic diseases. The present study was undertaken to observe the underlying aetiology and outcome of ALF in children under 18 years of age admitted at the department of Paediatric Gastroenterology & Nutrition, Bangabandhu Sheikh Mujib Medical University, Dhaka, Bangladesh. It was a retrospective review of medical records from November 2011 through October 2014. During this period a total of 35 patients were diagnosed to have ALF. Aetiology was established in 25(71.4%) cases, whereas in 10(28.6%) cases, no identifiable cause was found. Viral hepatitis was the underlying cause in 12(34.3%) cases. After treatment 15(43%) ALF patients survived, 8(23%) left hospital with risk bond (DORB), and 12(34%) patients died. The study showed that among the 12 death patients, 5(41.7%) had viral hepatitis, 3(25%) Wilson's disease, and in 4(33.3%) no cause could be identified. Viral hepatitis and Wilson disease were found to be two common causes of ALF in this study. Future studies with larger sample size are required to know the actual causes of acute liver failure in Bangladeshi children. PMID:27612896

  11. Mechanical response of collagen molecule under hydrostatic compression

    Energy Technology Data Exchange (ETDEWEB)

    Saini, Karanvir, E-mail: karans@iitrpr.ac.in; Kumar, Navin

    2015-04-01

    Proteins like collagen are the basic building blocks of various body tissues (soft and hard). Collagen molecules find their presence in the skeletal system of the body where they bear mechanical loads from different directions, either individually or along with hydroxy-apatite crystals. Therefore, it is very important to understand the mechanical behavior of the collagen molecule which is subjected to multi-axial state of loading. The estimation of strains of collagen molecule along different directions resulting from the changes in hydrostatic pressure magnitude, can provide us new insights into its mechanical behavior. In the present work, full atomistic simulations have been used to study global (volumetric) as well as local (along different directions) mechanical properties of the hydrated collagen molecule which is subjected to different hydrostatic pressure magnitudes. To estimate the local mechanical properties, the strains of collagen molecule along its longitudinal and transverse directions have been acquired at different hydrostatic pressure magnitudes. In spite of non-homogeneous distribution of atoms within the collagen molecule, the calculated values of local mechanical properties have been found to carry the same order of magnitude along the longitudinal and transverse directions. It has been demonstrated that the values of global mechanical properties like compressibility, bulk modulus, etc. as well as local mechanical properties like linear compressibility, linear elastic modulus, etc. are functions of magnitudes of applied hydrostatic pressures. The mechanical characteristics of collagen molecule based on the atomistic model have also been compared with that of the continuum model in the present work. The comparison showed up orthotropic material behavior for the collagen molecule. The information on collagen molecule provided in the present study can be very helpful in designing the future bio-materials.

  12. Clinical presentation, aetiology and complications of pancreatitis in children

    International Nuclear Information System (INIS)

    Background: Childhood Pancreatitis is an uncommon but serious condition with incidence on the rise. It manifests as acute or chronic form with epigastric pain, vomiting and elevated serum -amylase and lipase. This study was conducted with the aim to determine the clinical presentation, aetiology, and complications of pancreatitis in children. Method: This descriptive case series was conducted in the Department of Paediatric Gastroenterology, Hepatology and Nutrition, The Children's Hospital and the Institute of Child Health, Lahore from 1st January to 31st December 2014. Seventy-two patients up to the age of 15 years having abdominal pain, Amylase >200 IU/L and/or lipase >165 IU/L, with features of acute or chronic pancreatitis on abdominal imaging; were included in study. Data analysis was done using SPSS-20. Results: Of the total 72 patients, 43 (60 percentage) had acute pancreatitis, males were 25 (58 percentage) and females 18 (42 percentage) and chronic pancreatitis was diagnosed in 29 (40 percentage), males 10 (34 percentage) and females 19 (66 percentage). Common clinical features were abdominal pain (100 percentage), nausea and vomiting (79 percentage). Common aetiologies were idiopathic (40 percentage) while choledochal cyst 8 percentage, hyperlipidaemia 7 percentage, biliary tract stones/sludge 7 percentage and abdominal trauma 6percentage. Complications were more frequently associated with acute pancreatitis (60 percentage) than with chronic pancreatitis (34 percentage). Common complications were pseudo-pancreatic cyst (36 percentage), ascites (17 percentage) and pleural effusion (4 percentage). Conclusion: Abdominal pain, nausea and vomiting were common presenting features of childhood pancreatitis. Common aetiologies were idiopathic hyperlipidemia, biliary tract stones/sludge, choledochal cyst and abdominal trauma. Common complications were Pseudo-pancreatic cyst, ascites and pleural effusion. (author)

  13. Mechanical fatigue performance of PCL-chondroprogenitor constructs after cell culture under bioreactor mechanical stimulus.

    Science.gov (United States)

    Panadero, Juan Alberto; Sencadas, Vitor; Silva, Sonia C M; Ribeiro, Clarisse; Correia, Vitor; Gama, Francisco M; Gomez Ribelles, José Luis; Lanceros-Mendez, Senentxu

    2016-02-01

    In tissue engineering of cartilage, polymeric scaffolds are implanted in the damaged tissue and subjected to repeated compression loading cycles. The possibility of failure due to mechanical fatigue has not been properly addressed in these scaffolds. Nevertheless, the macroporous scaffold is susceptible to failure after repeated loading-unloading cycles. This is related to inherent discontinuities in the material due to the micropore structure of the macro-pore walls that act as stress concentration points. In this work, chondrogenic precursor cells have been seeded in poly-ε-caprolactone (PCL) scaffolds with fibrin and some were submitted to free swelling culture and others to cyclic loading in a bioreactor. After cell culture, all the samples were analyzed for fatigue behavior under repeated loading-unloading cycles. Moreover, some components of the extracellular matrix (ECM) were identified. No differences were observed between samples undergoing free swelling or bioreactor loading conditions, neither respect to matrix components nor to mechanical performance to fatigue. The ECM did not achieve the desired preponderance of collagen type II over collagen type I which is considered the main characteristic of hyaline cartilage ECM. However, prediction in PCL with ECM constructs was possible up to 600 cycles, an enhanced performance when compared to previous works. PCL after cell culture presents an improved fatigue resistance, despite the fact that the measured elastic modulus at the first cycle was similar to PCL with poly(vinyl alcohol) samples. This finding suggests that fatigue analysis in tissue engineering constructs can provide additional information missed with traditional mechanical measurements.

  14. Gemella morbillorum: an underestimated aetiology of central nervous system infection?

    Science.gov (United States)

    Benedetti, Paolo; Rassu, Mario; Branscombe, Michele; Sefton, Armine; Pellizzer, Giampietro

    2009-12-01

    A case is reported of cerebellar abscess and diffuse cerebritis due to Gemella morbillorum. The clinical course was 'biphasic', developing with an acute meningeal infection followed shortly afterwards by suppuration in the cerebellar and cerebral parenchyma; this pattern seemed to suggest a latent survival of the aetiological agent, probably within the central nervous system (CNS), despite systemic antibiotic therapy. Based upon a review of cases so far described, infections of the CNS caused by G. morbillorum appear to be an emerging reality. PMID:19713361

  15. Antenatal brain injury: aetiology and possibilities of prevention.

    Science.gov (United States)

    Hagberg, H; Mallard, C

    2000-02-01

    Although the aetiology of antenatal brain injury is often unclear, procedures can be employed to prevent or reduce the risk of injury. Defective neuropore closure can be prevented by periconceptional administration of folic acid, and the incidence of other severe malformations and genetic disorders can be reduced by early identification and termination of pregnancy. Antenatal identification of IUGR, administration of corticosteroids to cases with pending preterm birth, and treatment of maternal/fetal infections would also reduce the incidence of injury. Mothers can decrease the risk of injury by maintaining a good diet, avoiding smoking, alcohol intake and exposure to TORCH infections during pregnancy. PMID:10802749

  16. Epidemiology, aetiology, diagnosis and screening of lung cancer

    International Nuclear Information System (INIS)

    Lung cancer is the leading cause of cancer death globally. Smoking causes about 90 % of all lung cancer cases. Passive, i.e. involuntary smoking has been confirmed to enhance the risk of lung cancer in exposed people. Individual susceptibility is one of important factors in lung cancer formation. New knowledge in epidemiology and aetiology of lung cancer gives new possibilities in diagnostic and screening of this disease. Results of large randomised trials aimed at new technologies in lung cancer screening will be available in a few years. (author)

  17. Poroelastic Mechanical Effects of Hemicelluloses on Cellulosic Hydrogels under Compression

    Science.gov (United States)

    Lopez-Sanchez, Patricia; Cersosimo, Julie; Wang, Dongjie; Flanagan, Bernadine; Stokes, Jason R.; Gidley, Michael J.

    2015-01-01

    Hemicelluloses exhibit a range of interactions with cellulose, the mechanical consequences of which in plant cell walls are incompletely understood. We report the mechanical properties of cell wall analogues based on cellulose hydrogels to elucidate the contribution of xyloglucan or arabinoxylan as examples of two hemicelluloses displaying different interactions with cellulose. We subjected the hydrogels to mechanical pressures to emulate the compressive stresses experienced by cell walls in planta. Our results revealed that the presence of either hemicellulose increased the resistance to compression at fast strain rates. However, at slow strain rates, only xyloglucan increased composite strength. This behaviour could be explained considering the microstructure and the flow of water through the composites confirming their poroelastic nature. In contrast, small deformation oscillatory rheology showed that only xyloglucan decreased the elastic moduli. These results provide evidence for contrasting roles of different hemicelluloses in plant cell wall mechanics and man-made cellulose-based composite materials. PMID:25794048

  18. The Signaling Mechanisms Underlying Cell Polarity and Chemotaxis

    OpenAIRE

    Wang, Fei

    2009-01-01

    Chemotaxis—the directed movement of cells in a gradient of chemoattractant—is essential for neutrophils to crawl to sites of inflammation and infection and for Dictyostelium discoideum (D. discoideum) to aggregate during morphogenesis. Chemoattractant-induced activation of spatially localized cellular signals causes cells to polarize and move toward the highest concentration of the chemoattractant. Extensive studies have been devoted to achieving a better understanding of the mechanism(s) use...

  19. Statistical Structures Underlying Quantum Mechanics and Social Science

    OpenAIRE

    Wright, Ron

    2003-01-01

    Common observations of the unpredictability of human behavior and the influence of one question on the answer to another suggest social science experiments are probabilistic and may be mutually incompatible with one another, characteristics attributed to quantum mechanics (as distinguished from classical mechanics). This paper examines this superficial similarity in depth using the Foulis-Randall Operational Statistics language. In contradistinction to physics, social science deals with compl...

  20. Numerical investigation of pulmonary drug delivery under mechanical ventilation conditions

    Science.gov (United States)

    Banerjee, Arindam; van Rhein, Timothy

    2012-11-01

    The effects of mechanical ventilation waveform on fluid flow and particle deposition were studied in a computer model of the human airways. The frequency with which aerosolized drugs are delivered to mechanically ventilated patients demonstrates the importance of understanding the effects of ventilation parameters. This study focuses specifically on the effects of mechanical ventilation waveforms using a computer model of the airways of patient undergoing mechanical ventilation treatment from the endotracheal tube to generation G7. Waveforms were modeled as those commonly used by commercial mechanical ventilators. Turbulence was modeled with LES. User defined particle force models were used to model the drag force with the Cunningham correction factor, the Saffman lift force, and Brownian motion force. The endotracheal tube (ETT) was found to be an important geometric feature, causing a fluid jet towards the right main bronchus, increased turbulence, and a recirculation zone in the right main bronchus. In addition to the enhanced deposition seen at the carinas of the airway bifurcations, enhanced deposition was also seen in the right main bronchus due to impaction and turbulent dispersion resulting from the fluid structures created by the ETT. Authors acknowledge financial support through University of Missouri Research Board Award.

  1. Coping styles and behavioural flexibility: towards underlying mechanisms

    OpenAIRE

    Coppens, Caroline M.; de Boer, Sietse F.; Koolhaas, Jaap M.

    2010-01-01

    A coping style (also termed behavioural syndrome or personality) is defined as a correlated set of individual behavioural and physiological characteristics that is consistent over time and across situations. This relatively stable trait is a fundamental and adaptively significant phenomenon in the biology of a broad range of species, i.e. it confers differential fitness consequences under divergent environmental conditions. Behavioural flexibility appears to be an important underlying attribu...

  2. Analysis of nanoscale mechanical grasping under ambient conditions

    International Nuclear Information System (INIS)

    In this paper, in order to understand mechanical grasping at the nanoscale, contact mechanics between nanogrippers and nanoobjects is studied. Contact models are introduced to simulate elastic contacts between various profiles of a flat surface, sphere and cylinder for different types of nanoobjects and nanogrippers. Analyses and evaluation instances indicate that friction forces, commonly used in macro-grasping to overcome gravity, at the nanoscale are often insufficient to overcome the relatively strong adhesion forces when picking up the nanoobject deposited on a substrate due to the tiny contact area. For stable nanoscale grasping, nonparallel two-finger grippers with a 'V' configuration are demonstrated to have better grasping capabilities than parallel grippers. To achieve mechanical nanoscale grasping, a nanogripper constructed from two microcantilevers is presented. Experimental results for the pick-and-place manipulation of silicon nanowires validate the theoretical analyses and capabilities of the proposed nanogripper.

  3. Epigenetic mechanisms underlying the pathogenesis of neurogenetic diseases.

    Science.gov (United States)

    Qureshi, Irfan A; Mehler, Mark F

    2014-10-01

    There have been considerable advances in uncovering the complex genetic mechanisms that underlie nervous system disease pathogenesis, particularly with the advent of exome and whole genome sequencing techniques. The emerging field of epigenetics is also providing further insights into these mechanisms. Here, we discuss our understanding of the interplay that exists between genetic and epigenetic mechanisms in these disorders, highlighting the nascent field of epigenetic epidemiology-which focuses on analyzing relationships between the epigenome and environmental exposures, development and aging, other health-related phenotypes, and disease states-and next-generation research tools (i.e., those leveraging synthetic and chemical biology and optogenetics) for examining precisely how epigenetic modifications at specific genomic sites affect disease processes.

  4. Strain-driven criticality underlies nonlinear mechanics of fibrous networks

    CERN Document Server

    Sharma, A; Rens, R; Vahabi, M; Jansen, K A; Koenderink, G H; MacKintosh, F C

    2016-01-01

    Networks with only central force interactions are floppy when their average connectivity is below an isostatic threshold. Although such networks are mechanically unstable, they can become rigid when strained. It was recently shown that the transition from floppy to rigid states as a function of simple shear strain is continuous, with hallmark signatures of criticality (Nat. Phys. 12, 584 (2016)). The nonlinear mechanical response of collagen networks was shown to be quantitatively described within the framework of such mechanical critical phenomenon. Here, we provide a more quantitative characterization of critical behavior in subisostatic networks. Using finite size scaling we demonstrate the divergence of strain fluctuations in the network at well-defined critical strain. We show that the characteristic strain corresponding to the onset of strain stiffening is distinct from but related to this critical strain in a way that depends on critical exponents. We confirm this prediction experimentally for collagen...

  5. Statistical Structures Underlying Quantum Mechanics and Social Science

    CERN Document Server

    Wright, R

    2003-01-01

    Common observations of the unpredictability of human behavior and the influence of one question on the answer to another suggest social science experiments are probabilistic and may be mutually incompatible with one another, characteristics attributed to quantum mechanics (as distinguished from classical mechanics). This paper examines this superficial similarity in depth using the Foulis-Randall Operational Statistics language. In contradistinction to physics, social science deals with complex, open systems for which the set of possible experiments is unknowable and outcome interference is a graded phenomenon resulting from the ways the human brain processes information. It is concluded that social science is, in some ways, "less classical" than quantum mechanics, but that generalized "quantum" structures may provide appropriate descriptions of social science experiments. Specific challenges to extending "quantum" structures to social science are identified.

  6. Mechanisms underlying the inhibition of interferon signaling by viruses.

    Science.gov (United States)

    Devasthanam, Anand S

    2014-02-15

    A hallmark of the antiviral response is the induction of interferons. First discovered in 1957 by Issac and Lindeman, interferons are noted for their ability to interfere with viral replication. Interferons act via autocrine and paracrine pathways to induce an antiviral state in infected cells and in neighboring cells containing interferon receptors. Interferons are the frontline defenders against viral infection and their primary function is to locally restrict viral propagation. Viruses have evolved mechanisms to escape the host interferon response, thus gaining a replicative advantage in host cells. This review will discuss recent findings on the mechanisms viruses use to evade the host interferon response. This knowledge is important because the treatment of viral infections is a challenge of global proportions and a better understanding of the mechanisms viruses use to persist in the host may uncover valuable insights applicable to the discovery of novel drug targets.

  7. Underlying molecular and cellular mechanisms in childhood irritable bowel syndrome.

    Science.gov (United States)

    Chumpitazi, Bruno P; Shulman, Robert J

    2016-12-01

    Irritable bowel syndrome (IBS) affects a large number of children throughout the world. The symptom expression of IBS is heterogeneous, and several factors which may be interrelated within the IBS biopsychosocial model play a role. These factors include visceral hyperalgesia, intestinal permeability, gut microbiota, psychosocial distress, gut inflammation, bile acids, food intolerance, colonic bacterial fermentation, and genetics. The molecular and cellular mechanisms of these factors are being actively investigated. In this mini-review, we present updates of these mechanisms and, where possible, relate the findings to childhood IBS. Mechanistic elucidation may lead to the identification of biomarkers as well as personalized childhood IBS therapies. PMID:26883355

  8. Nematodynamics modelling under extreme mechanical and electric stresses

    Science.gov (United States)

    Amoddeo, Antonino

    2015-01-01

    Nematic liquid crystals confined in asymmetric π-cells and subjected to intense electrical and mechanical stresses undergo strong distortions which can be relaxed by means of the order reconstruction, a fast switching mechanism connecting topologically different textures, assuming bulk and/or surface characteristics depending on both amplitude of the applied electric fields and anchoring angles of the nematic molecules on the confining surfaces. In the frame of the Landau-de Gennes order tensor theory, we provide a numerical model implemented with a moving mesh finite element method appropriate to describe the nematic order dynamics, allowing to map the switching properties of the nematic texture.

  9. The Class V lesion--aetiology and restoration.

    Science.gov (United States)

    Tyas, M J

    1995-06-01

    The aetiology of non-carious cervical lesions is discussed. These have been variously described as 'abrasion', 'erosion', 'abrasion/erosion', and 'idiopathic cervical'. However, many lesions do not fit the classical appearance or location of an erosive and/or abrasive origin, and there is increasing interest in the possible role of occlusal stress in their aetiology. Non-carious cervical lesions often require restoration, and there are essentially three options using tooth-coloured materials: a restorative glass ionomer cement, a liner/base glass ionomer cement overlayed with a resin composite, or a resin composite bonded by an enamel/dentine-adhesive. The materials and techniques used in these options are discussed, indicating their advantages and disadvantages. Results of available clinical trials of these systems are given, and the link with the stress theory of cervical tooth loss is described. The preferred restorative approaches in order are: resin-modified restorative glass ionomer; resin-modified liner/base glass ionomer with a microfine resin composite overlay; enamel/dentine bonding agent with a microfine resin composite.

  10. Dynamics of mechanical system for electromechanical integrated toroidal drive under electric disturbance

    Institute of Scientific and Technical Information of China (English)

    许立忠; 郝秀红

    2014-01-01

    Based on electromagnetics and mechanics, electromechanical coupled dynamic equations for the drive were developed. Using method of perturbation, free vibrations of the mechanical system under electric disturbance were investigated. The forced responses of the mechanical system to mechanical excitation under electric disturbance were also presented. It is known that for the system with electric disturbance, as time grows, beat occurs. When electric disturbing frequency is near to the natural frequencies of the mechanical system or their integer multiple, resonance vibrations occur. The forced responses of the mechanical system to mechanical excitation under electric disturbance are compound vibrations decided by mechanical excitation, electric disturbance and parameters of the system. The coupled resonance vibration caused by electric disturbance and mechanical excitation was discussed as well. The conditions under which above coupled resonance occurs were presented. The results show that when the difference of the excitation frequency and the perturbation frequency is equal to some order of natural frequency, coupled resonance vibrations occur.

  11. MECHANICAL BEHAVIORS OF SATURATED SAND UNDER COMPLICATED LOADING

    Institute of Scientific and Technical Information of China (English)

    ShaoShengjun

    2004-01-01

    The different physical states of saturated sand, including shear elasticity, positive dilatancy, and negative dilatancy (preliminary negative dilatancy, secondary negative dilatancy and reversal negative dilatancy) are revealed based on the pore water pressure response of saturated sand in undrained dynamic torsional tests of thin cylinder samples and also checked by the drained cyclic triaxial tests under a given mean effective normal stress. According to the effective stress path of different physical states under the undrained cyclic torsional tests the physical state transformation surface, stress history boundary and yield surface are determined, and the state boundary surface is also determined by the range of effective frictional stress state movement.Based on the moving yield surface without rotation, and the expanding stress history boundary surface relevant to the stress path variations under different physical states in 3D stress space,a physical state model is proposed to provide a new approach to calculating the transient pore water pressure under the undrained condition,and the volume strain of dilatation under drained condition in this paper.

  12. Peer influence: neural mechanisms underlying in-group conformity

    NARCIS (Netherlands)

    Stallen, Mirre; Smidts, A.; Sanfey, A.G.

    2013-01-01

    People often conform to the behavior of others with whom they identify. However, it is unclear what fundamental mechanisms underlie this type of conformity. Here, we investigate the processes mediating in-group conformity by using functional magnetic resonance imaging (fMRI). Participants completed

  13. Peer influence: Neural mechanisms underlying in-group conformity

    NARCIS (Netherlands)

    M. Stallen (Mirre); A. Smidts (Ale); A.G. Sanfey (Alan)

    2013-01-01

    textabstractPeople often conform to the behavior of others with whom they identify. However, it is unclear what fundamental mechanisms underlie this type of conformity. Here, we investigate the processes mediating in-group conformity by using functional magnetic resonance imaging (fMRI). Participant

  14. A possible mechanism of current in medium under electromagnetic wave

    Institute of Scientific and Technical Information of China (English)

    Zhang Tao

    2006-01-01

    In this paper a possible mechanism of current in medium is presented. Comparison between this current and the magnetization current was made. Expression for this current was derived. This work is helpful to understanding the interaction between medium and electromagnetic wave.

  15. A review of mechanisms underlying anticarcinogenicity by brassica vegetables

    NARCIS (Netherlands)

    Verhoeven, D.T.H.; Verhagen, H.; Goldbohm, R.A.; Brandt, P.A. van den; Poppel, G. van

    1997-01-01

    The mechanisms by which brassica vegetables might decrease the risk of cancer are reviewed in this paper. Brassicas, including all types of cabbages, broccoli, cauliflower and Brussels sprouts, may be protective against cancer due to their relatively high glucosinolate content. Glucosinolates are us

  16. Underlying mechanisms of transient luminous events: a review

    Directory of Open Access Journals (Sweden)

    V. V. Surkov

    2012-08-01

    Full Text Available Transient luminous events (TLEs occasionally observed above a strong thunderstorm system have been the subject of a great deal of research during recent years. The main goal of this review is to introduce readers to recent theories of electrodynamics processes associated with TLEs. We examine the simplest versions of these theories in order to make their physics as transparent as possible. The study is begun with the conventional mechanism for air breakdown at stratospheric and mesospheric altitudes. An electron impact ionization and dissociative attachment to neutrals are discussed. A streamer size and mobility of electrons as a function of altitude in the atmosphere are estimated on the basis of similarity law. An alternative mechanism of air breakdown, runaway electron mechanism, is discussed. In this section we focus on a runaway breakdown field, characteristic length to increase avalanche of runaway electrons and on the role played by fast seed electrons in generation of the runaway breakdown. An effect of thunderclouds charge distribution on initiation of blue jets and gigantic jets is examined. A model in which the blue jet is treated as upward-propagating positive leader with a streamer zone/corona on the top is discussed. Sprite models based on streamer-like mechanism of air breakdown in the presence of atmospheric conductivity are reviewed. To analyze conditions for sprite generation, thunderstorm electric field arising just after positive cloud-to-ground stroke is compared with the thresholds for propagation of positively/negatively charged streamers and with runway breakdown. Our own estimate of tendril's length at the bottom of sprite is obtained to demonstrate that the runaway breakdown can trigger the streamer formation. In conclusion we discuss physical mechanisms of VLF (very low frequency and ELF (extremely low frequency phenomena associated with sprites.

  17. Mechanism of NBTI Recovery under Negative Voltage Stress

    Institute of Scientific and Technical Information of China (English)

    CAO Yan-Rong; HU Shi-Gang; MA Xiao-Hua; HAO Yue

    2008-01-01

    Recovery phenomenon is observed under negative gate voltage stress which is smaller than the previous degradation stress. We focus on the drain current to study the degradation and recovery of negative bias temperature instability (NBTI) with a real-time method. By this method, different recovery phenomena among different size devices are observed. Under negative recovery stress, the drain current gradually recovers for the large size devices and gets into recovery saturation when long recovery time is involved. For small-size devices, a step-like recovery of drain current is observed. The recovery of the drain current is mainly caused by the holes detrapping and tunnelling back to the channel surface which are trapped in oxide. The model of hole detrapping explains the recovery under negative voltage stress reasonably.

  18. Mechanisms underlying social inequality in post-menopausal breast cancer.

    Science.gov (United States)

    Hvidtfeldt, Ulla Arthur

    2014-10-01

    This thesis is based on studies conducted in the period 2010-2014 at Department of Public Health, University of Copenhagen and at Department of Epidemiology and Population Health, Albert Einstein College of Medicine, New York. The results are presented in three scientific papers and a synopsis. The main objective of the thesis was to determine mechanisms underlying social inequality (defined by educational level) in postmenopausal breast cancer (BC) by addressing mediating effects through hormone therapy (HT) use, BMI, lifestyle and reproductive factors. The results of previous studies suggest that the higher risk of postmenopausal BC among women of high socioeconomic position (SEP) may be explained by reproductive factors and health behaviors. Women of higher SEP generally have fewer children and give birth at older ages than women of low SEP, and these factors have been found to affect the risk of BC - probably through altered hormone levels. Adverse effects on BC risk have also been documented for modifiable health behaviors that may affect hormone levels, such as alcohol consumption, high BMI, physical inactivity, and HT use. Alcohol consumption and HT use are likewise more common among women of higher SEP. The analyses were based on the Social Inequality in Cancer (SIC) cohort and a subsample of the Women's Health Initiative Observational Study (WHI-OS). The SIC cohort was derived by pooling 6 individual studies from the Copenhagen area including 33,562 women (1,733 BC cases) aged 50-70 years at baseline. The subsample of WHI-OS consisted of two case-cohort studies with measurements of endogenous estradiol (N = 1,601) and insulin (N = 791). Assessment of mediation often relies on comparing multiplicative models with and without the potential mediator. Such approaches provide potentially biased results, because they do not account for mediator-outcome confounding, exposure-dependent mediator-outcome confounding, exposure-mediator interaction and interactions

  19. The genetic aetiology of cannabis use initiation: A meta-analysis of genome-wide association studies and a SNP-based heritability estimation

    NARCIS (Netherlands)

    Verweij, C.J.H.; Vinkhuyzen, A.A.E.; Benyamin, B.; Lynskey, M.T.; Quaye, L.; Agrawal, A.; Gordon, S.D.; Montgomery, G.W.; Madden, P.A.F.; Heath, A.C.; Spector, T.D.; Martin, N.G.; Medland, S.E.

    2013-01-01

    While initiation of cannabis use is around 40% heritable, not much is known about the underlying genetic aetiology. Here, we meta-analysed two genome-wide association studies of initiation of cannabis use with >10000 individuals. None of the genetic variants reached genome-wide significance. We a

  20. Mechanism and kinetics of mineral weathering under acid conditions.

    NARCIS (Netherlands)

    Anbeek, C.

    1994-01-01

    This study deals with the relationships between crystal structure, grain diameter, surface morphology and dissolution kinetics for feldspar and quartz under acid conditions.Intensively ground samples from large, naturally weathered mineral fragments are frequently used in dissolution studies. The su

  1. Molecular Mechanism Underlying Lymphatic Metastasis in Pancreatic Cancer

    Directory of Open Access Journals (Sweden)

    Zhiwen Xiao

    2014-01-01

    Full Text Available As the most challenging human malignancies, pancreatic cancer is characterized by its insidious symptoms, low rate of surgical resection, high risk of local invasion, metastasis and recurrence, and overall dismal prognosis. Lymphatic metastasis, above all, is recognized as an early adverse event in progression of pancreatic cancer and has been described to be an independent poor prognostic factor. It should be noted that the occurrence of lymphatic metastasis is not a casual or stochastic but an ineluctable and designed event. Increasing evidences suggest that metastasis-initiating cells (MICs and the microenvironments may act as a double-reed style in this crime. However, the exact mechanisms on how they function synergistically for this dismal clinical course remain largely elusive. Therefore, a better understanding of its molecular and cellular mechanisms involved in pancreatic lymphatic metastasis is urgently required. In this review, we will summarize the latest advances on lymphatic metastasis in pancreatic cancer.

  2. Peer influence: neural mechanisms underlying in-group conformity.

    Science.gov (United States)

    Stallen, Mirre; Smidts, Ale; Sanfey, Alan G

    2013-01-01

    People often conform to the behavior of others with whom they identify. However, it is unclear what fundamental mechanisms underlie this type of conformity. Here, we investigate the processes mediating in-group conformity by using functional magnetic resonance imaging (fMRI). Participants completed a perceptual decision-making task while undergoing fMRI, during which they were exposed to the judgments of both in-group and out-group members. Our data suggest that conformity to the in-group is mediated by both positive affect as well as the cognitive capacity of perspective taking. Examining the processes that drive in-group conformity by utilizing a basic decision-making paradigm combined with neuroimaging methods provides important insights into the potential mechanisms of conformity. These results may provide an integral step in developing more effective campaigns using group conformity as a tool for behavioral change.

  3. Mental imagery in music performance: underlying mechanisms and potential benefits.

    Science.gov (United States)

    Keller, Peter E

    2012-04-01

    This paper examines the role of mental imagery in music performance. Self-reports by musicians, and various other sources of anecdotal evidence, suggest that covert auditory, motor, and/or visual imagery facilitate multiple aspects of music performance. The cognitive and motor mechanisms that underlie such imagery include working memory, action simulation, and internal models. Together these mechanisms support the generation of anticipatory images that enable thorough action planning and movement execution that is characterized by efficiency, temporal precision, and biomechanical economy. In ensemble performance, anticipatory imagery may facilitate interpersonal coordination by enhancing online predictions about others' action timing. Overlap in brain regions subserving auditory imagery and temporal prediction is consistent with this view. It is concluded that individual differences in anticipatory imagery may be a source of variation in expressive performance excellence and the quality of ensemble cohesion. Engaging in effortful musical imagery is therefore justified when artistic perfection is the goal.

  4. "Adaptive response" - some underlying mechanisms and open questions

    OpenAIRE

    Evgeniya G. Dimova; Bryant, Peter E.; Chankova, Stephka G

    2008-01-01

    Organisms are affected by different DNA damaging agents naturally present in the environment or released as a result of human activity. Many defense mechanisms have evolved in organisms to minimize genotoxic damage. One of them is induced radioresistance or adaptive response. The adaptive response could be considered as a nonspecific phenomenon in which exposure to minimal stress could result in increased resistance to higher levels of the same or to other types of stress some hours later. A ...

  5. POLYSTYRENE THERMAL AND CATALYTIC DEGRADATION MECHANISMS UNDER HYDROCRACKING CONDITIONS

    OpenAIRE

    Edwin G. Fuentes; María P. González-Marcos; Rubén López-Fonseca; José I. Gutiérrez-Ortiz; Juan R. González-Velasco

    2012-01-01

    In this study, differences between reaction mechanisms involved in thermal and catalytic processes of polystyrene degradation, 30% wt. in decalin, over Pt/Al2O3 bifunctional catalyst, are presented. Oligomers and aromatic derivates, mainly styrene, are mainly produced through the thermal process, whereas, with Pt/Al2O3, both depolymerisation and hydrogenation reactions have occured. Oligomers, in a lower concentration than in the thermal process, and aromatics, mainly ethyl benzene, are obtai...

  6. MACROECONOMIC EFFECTS OF FISCAL POLICY TRANSMISSION MECHANISM UNDER FINANCIAL CRISIS

    OpenAIRE

    Virchenko, A.

    2012-01-01

    The paper focuses on specific effects of each of the element of fiscal policy transmission mechanism on real economy sector. Key approaches to fiscal policy implementation and fiscal transmission channels definition are highlighted. A formalized description is suggested as to the effect of fiscal impulses on main macroeconomic indices. A necessity of implementing of macro-prudential fiscal policy aimed to meet the financial crisis is emphasized. Using logical method and comparative analysis, ...

  7. The Survival Advantage: Underlying Mechanisms and Extant Limitations

    Directory of Open Access Journals (Sweden)

    Stephanie A. Kazanas

    2015-04-01

    Full Text Available Recently, researchers have begun to investigate the function of memory in our evolutionary history. According to Nairne and colleagues (e.g., Nairne, Pandeirada, and Thompson, 2008; Nairne, Thompson, and Pandeirada, 2007, the best mnemonic strategy for learning lists of unrelated words may be one that addresses the same problems that our Pleistocene ancestors faced: fitness-relevant problems including securing food and water, as well as protecting themselves from predators. Survival processing has been shown to promote better recall and recognition memory than many well-known mnemonic strategies (e.g., pleasantness ratings, imagery, generation, etc.. However, the survival advantage does not extend to all types of stimuli and tasks. The current review presents research that has replicated Nairne et al.'s (2007 original findings, in addition to the research designs that fail to replicate the survival advantage. In other words, there are specific manipulations in which survival processing does not appear to benefit memory any more than other strategies. Potential mechanisms for the survival advantage are described, with an emphasis on those that are the most plausible. These proximate mechanisms outline the memory processes that may contribute to the advantage, although the ultimate mechanism may be the congruity between the survival scenario and Pleistocene problem-solving.

  8. Photooxidation of tetrahydrobiopterin under UV irradiation: possible pathways and mechanisms.

    Science.gov (United States)

    Buglak, Andrey A; Telegina, Taisiya A; Lyudnikova, Tamara A; Vechtomova, Yulia L; Kritsky, Mikhail S

    2014-01-01

    Tetrahydrobiopterin (H4 Bip) is a cofactor for several key enzymes, including NO synthases and aromatic amino acid hydroxylases (AAHs). Normal functioning of the H4 Bip regeneration cycle is extremely important for the work of AAHs. Oxidized pterins may accumulate if the H4 Bip regeneration cycle is disrupted or if H4 Bip autoxidation occurs. These oxidized pterins can photosensitize the production of singlet molecular oxygen (1)O2 and thus cause oxidative stress. In this context, we studied the photooxidation of H4 Bip in phosphate buffer at pH 7.2. We found that UV irradiation of H4 Bip affected its oxidation rate (quantum yield Φ300 = (2.7 ± 0.4) × 10(-3)). The effect of UV irradiation at λ = 350 nm on H4 Bip oxidation was stronger, especially in the presence of biopterin (Bip) (Φ350 = (9.7 ± 1.5) × 10(-3)). We showed that the rate of H4 Bip oxidation linearly depends on Bip concentration. Experiments with KI, a selective quencher of triplet pterins at micromolar concentrations, demonstrated that the oxidation is sensitized by the triplet state biopterin (3) Bip. Apparently, electron transfer sensitization (Type-I mechanism) is dominant. Energy transfer (Type-II mechanism) and singlet oxygen generation play only a secondary role. The mechanisms of H4 Bip photooxidation and their biological meaning are discussed. PMID:24773158

  9. Dislocation mechanism of deuterium retention in tungsten under plasma implantation

    International Nuclear Information System (INIS)

    We have developed a new theoretical model for deuterium (D) retention in tungsten-based alloys on the basis of its being trapped at dislocations and transported to the surface via the dislocation network with parameters determined by ab initio calculations. The model is used to explain experimentally observed trends of D retention under sub-threshold implantation, which does not produce stable lattice defects to act as traps for D in conventional models. Saturation of D retention with implantation dose and effects due to alloying of tungsten with, e.g. tantalum, are evaluated, and comparison of the model predictions with experimental observations under high-flux plasma implantation conditions is presented. (paper)

  10. Spontaneous chylothorax complicating small cell lung cancer – Review of aetiology and diagnosis

    Directory of Open Access Journals (Sweden)

    S. Hanina

    2015-01-01

    Full Text Available We report the first case of spontaneous chylothorax complicating small cell lung cancer. A 52 year old female presented with exertional dyspnoea, left-sided chest and neck pain, and dysphagia. The chest X-ray on admission revealed a large left-sided pleural effusion. A subsequent CT chest showed a large anterior mediastinal mass with a left brachiocephalic and jugular vein thrombosis. The patient underwent medical thoracoscopy with chest drain insertion, which drained pleural fluid high in triglycerides, consistent with a chylothorax. Due to its uncommon nature, the management of chylothorax is not well defined. Alongside the case report, we provide a review of aetiology, mechanism and diagnosis with a brief summary of treatment options.

  11. Time Windows of Interneuron Development: Implications to Our Understanding of the Aetiology and Treatment of Schizophrenia

    Directory of Open Access Journals (Sweden)

    Zarina Greenberg

    2015-11-01

    Full Text Available Schizophrenia is a devastating neuropsychiatric disorder widely believed to arise from defects during brain development. Indeed, dysfunction in the formation and function of GABAergic cortical interneurons has been implicated as a central pathogenic mechanism in this, and other, neurodevelopmental disorders. Understanding the coordination and timing of interneuron development including the complex processes of specification, proliferation, migration and their incorporation into finely tuned cortical networks is therefore essential in determining their role in neurodevelopmental disease. Studies using mouse models have highlighted the functional relevance of transcription factor networks and common signalling pathways in interneuron development but have faced challenges in identifying clear time windows where these factors are essential. Here we discuss recent developments highlighting critical time frames in the specification and migration of cortical interneurons and the impact of aberrant development to aetiology and treatments of schizophrenia.

  12. Molecular and Electrophysiological Mechanisms Underlying Cardiac Arrhythmogenesis in Diabetes Mellitus.

    Science.gov (United States)

    Tse, Gary; Lai, Eric Tsz Him; Tse, Vivian; Yeo, Jie Ming

    2016-01-01

    Diabetes is a common endocrine disorder with an ever increasing prevalence globally, placing significant burdens on our healthcare systems. It is associated with significant cardiovascular morbidities. One of the mechanisms by which it causes death is increasing the risk of cardiac arrhythmias. The aim of this article is to review the cardiac (ion channel abnormalities, electrophysiological and structural remodelling) and extracardiac factors (neural pathway remodelling) responsible for cardiac arrhythmogenesis in diabetes. It is concluded by an outline of molecular targets for future antiarrhythmic therapy for the diabetic population. PMID:27642609

  13. Electronic, mechanical and dielectric properties of silicane under tensile strain

    Energy Technology Data Exchange (ETDEWEB)

    Jamdagni, Pooja, E-mail: j.poojaa1228@gmail.com; Sharma, Munish; Ahluwalia, P. K. [Physics Department, Himachal Pradesh University, Shimla, Himachal Pradesh, India 171005 (India); Kumar, Ashok [Physics Department, Panjab University, Chandigarh, India, 160014 (India); Thakur, Anil [Physics Department, Govt. Collage Solan, Himachal Pradesh, India,173212 (India)

    2015-05-15

    The electronic, mechanical and dielectric properties of fully hydrogenated silicene i.e. silicane in stable configuration are studied by means of density functional theory based calculations. The band gap of silicane monolayer can be flexibly reduced to zero when subjected to bi-axial tensile strain, leading to semi-conducting to metallic transition, whereas the static dielectric constant for in-plane polarization increases monotonically with increasing strain. Also the EEL function show the red shift in resonance peak with tensile strain. Our results offer useful insight for the application of silicane monolayer in nano-optical and electronics devices.

  14. Advanced waterflooding in chalk reservoirs: Understanding of underlying mechanisms

    DEFF Research Database (Denmark)

    Zahid, Adeel; Sandersen, Sara Bülow; Stenby, Erling Halfdan;

    2011-01-01

    pressure. We have also observed formation of a microemulsion phase between brine and oil with the increase in sulfate ion concentration at high temperature and pressure. In addition, sulfate ions can reduce interfacial tension (IFT) between oil and water. We propose that the decrease in viscosity and...... formation of a microemulsion phase could be the possible reasons for the observed increase in oil recovery with sulfate ions at high temperature in chalk reservoirs besides the mechanism of the rock wettability alteration, which has been reported in most previous studies....

  15. Analysis of thermal conductivity of polymeric nanocomposites under mechanical loading

    Science.gov (United States)

    Yu, Suyoung; Yang, Seunghwa; Cho, Maenghyo

    2013-12-01

    When the plastic deformation is applied to neat polymer, the polymer chains are aligned and the thermal conductivity of neat polymer increases linearly along the loading direction. However, the thermal conductivity change of nanocomposites consisting of polymer matrix and nanofillers during plastic deformation is not simple. The volume fraction and size of nanofillers scarcely affect the structural change of polymer chains during the plastic deformation. In this study, the structural change of polymeric materials according to the mechanical loading and its effect on the thermal transport properties are investigated through a molecular dynamics simulation. To investigate the effects of nanofiller, its volume fraction, and size on the thermal transport properties, the unit cells of neat amorphous nylon 6 and nanocomposites consisting of amorphous nylon 6 matrix and spherical silica particles are prepared. The molecular unit cells are uniaxially stretched by applying constant strain along the loading directions. Then, non-equilibrium molecular dynamics (NEMD) simulations are performed to estimate the thermal conductivities during plastic deformation. The alignment of polymer chains is analyzed by tracing the orientation correlation function of each polymer molecule and the free volume change during the mechanical loading is also analyzed.

  16. Understanding ultrasound induced sonoporation: definitions and underlying mechanisms.

    Science.gov (United States)

    Lentacker, I; De Cock, I; Deckers, R; De Smedt, S C; Moonen, C T W

    2014-06-01

    In the past two decades, research has underlined the potential of ultrasound and microbubbles to enhance drug delivery. However, there is less consensus on the biophysical and biological mechanisms leading to this enhanced delivery. Sonoporation, i.e. the formation of temporary pores in the cell membrane, as well as enhanced endocytosis is reported. Because of the variety of ultrasound settings used and corresponding microbubble behavior, a clear overview is missing. Therefore, in this review, the mechanisms contributing to sonoporation are categorized according to three ultrasound settings: i) low intensity ultrasound leading to stable cavitation of microbubbles, ii) high intensity ultrasound leading to inertial cavitation with microbubble collapse, and iii) ultrasound application in the absence of microbubbles. Using low intensity ultrasound, the endocytotic uptake of several drugs could be stimulated, while short but intense ultrasound pulses can be applied to induce pore formation and the direct cytoplasmic uptake of drugs. Ultrasound intensities may be adapted to create pore sizes correlating with drug size. Small molecules are able to diffuse passively through small pores created by low intensity ultrasound treatment. However, delivery of larger drugs such as nanoparticles and gene complexes, will require higher ultrasound intensities in order to allow direct cytoplasmic entry.

  17. Molecular mechanisms underlying the effects of acupuncture on neuropathic pain**

    Institute of Scientific and Technical Information of China (English)

    Ziyong Ju; Huashun Cui; Xiaohui Guo; Huayuan Yang; Jinsen He; Ke Wang

    2013-01-01

    Acupuncture has been used to treat neuropathic pain for a long time, but its mechanisms of action remain unknown. In this study, we observed the effects of electroacupuncture and manual acu-puncture on neuropathic pain and on ephrin-B/EphB signaling in rats models of chronic constriction injury-induced neuropathic pain. The results showed that manual acupuncture and elec-puncture significantly reduced mechanical hypersensitivity fol owing chronic constriction injury, es-pecial y electroacupuncture treatment. Real-time PCR results revealed that ephrin-B1/B3 and EphB1/B2 mRNA expression levels were significantly increased in the spinal dorsal horns of chronic constriction injury rats. Electroacupuncture and manual acupuncture suppressed the high sion of ephrin-B1 mRNA, and elevated EphB3/B4 mRNA expression. Electroacupuncture signifi-cantly enhanced the mRNA expression of ephrin-B3 and EphB3/B6 in the dorsal horns of neuro-pathic pain rats. Western blot results revealed that electroacupuncture in particular, and manual acupuncture, significantly up-regulated ephrin-B3 protein levels in rat spinal dorsal horns. The re-sults of this study suggest that acupuncture could activate ephrin-B/EphB signaling in neuropathic pain rats and improve neurological function.

  18. Ethanol Neurotoxicity in the Developing Cerebellum: Underlying Mechanisms and Implications

    Directory of Open Access Journals (Sweden)

    Ambrish Kumar

    2013-06-01

    Full Text Available Ethanol is the main constituent of alcoholic beverages that exerts toxicity to neuronal development. Ethanol affects synaptogenesis and prevents proper brain development. In humans, synaptogenesis takes place during the third trimester of pregnancy, and in rodents this period corresponds to the initial few weeks of postnatal development. In this period neuronal maturation and differentiation begin and neuronal cells start migrating to their ultimate destinations. Although the neuronal development of all areas of the brain is affected, the cerebellum and cerebellar neurons are more susceptible to the damaging effects of ethanol. Ethanol’s harmful effects include neuronal cell death, impaired differentiation, reduction of neuronal numbers, and weakening of neuronal plasticity. Neuronal development requires many hormones and growth factors such as retinoic acid, nerve growth factors, and cytokines. These factors regulate development and differentiation of neurons by acting through various receptors and their signaling pathways. Ethanol exposure during development impairs neuronal signaling mechanisms mediated by the N-methyl-d-aspartate (NMDA receptors, the retinoic acid receptors, and by growth factors such as brain-derived neurotrophic factor (BDNF, insulin-like growth factor 1 (IGF-I, and basic fibroblast growth factor (bFGF. In combination, these ethanol effects disrupt cellular homeostasis, reduce the survival and migration of neurons, and lead to various developmental defects in the brain. Here we review the signaling mechanisms that are required for proper neuronal development, and how these processes are impaired by ethanol resulting in harmful consequences to brain development.

  19. The antimicrobial propeptide hCAP-18 plasma levels in neutropenia of various aetiologies

    DEFF Research Database (Denmark)

    Ye, Ying; Carlsson, Göran; Karlsson-Sjöberg, Jenny M T;

    2015-01-01

    The underlying cause of neutropenia may be difficult to determine due to similar clinical presentation in many neutropenic conditions. The neutrophil protein hCAP-18 (pro-LL-37) is a major component of neutrophil secondary granules and in this prospective study we assessed the use of hCAP-18 levels...... in blood plasma for differential diagnosis of neutropenic patients (n = 133) of various aetiologies. Plasma levels of hCAP-18 were determined using immunoblot and ELISA. Patients with severe congenital neutropenia (n = 23) presented with the lowest levels of plasma hCAP-18 and differential diagnostic...... diagnostic value in differential diagnosis of chronic neutropenia. Neutropenic patients with Shwachman-Diamond syndrome, Barth syndrome, Cohen syndrome, acute myeloid leukaemia and specific granule deficiency presented with reduced plasma hCAP-18 levels as well. The blood plasma level of hCAP-18 was thus low...

  20. Mechanisms Underlying Mammalian Hybrid Sterility in Two Feline Interspecies Models.

    Science.gov (United States)

    Davis, Brian W; Seabury, Christopher M; Brashear, Wesley A; Li, Gang; Roelke-Parker, Melody; Murphy, William J

    2015-10-01

    The phenomenon of male sterility in interspecies hybrids has been observed for over a century, however, few genes influencing this recurrent phenotype have been identified. Genetic investigations have been primarily limited to a small number of model organisms, thus limiting our understanding of the underlying molecular basis of this well-documented "rule of speciation." We utilized two interspecies hybrid cat breeds in a genome-wide association study employing the Illumina 63 K single-nucleotide polymorphism array. Collectively, we identified eight autosomal genes/gene regions underlying associations with hybrid male sterility (HMS) involved in the function of the blood-testis barrier, gamete structural development, and transcriptional regulation. We also identified several candidate hybrid sterility regions on the X chromosome, with most residing in close proximity to complex duplicated regions. Differential gene expression analyses revealed significant chromosome-wide upregulation of X chromosome transcripts in testes of sterile hybrids, which were enriched for genes involved in chromatin regulation of gene expression. Our expression results parallel those reported in Mus hybrids, supporting the "Large X-Effect" in mammalian HMS and the potential epigenetic basis for this phenomenon. These results support the value of the interspecies feline model as a powerful tool for comparison to rodent models of HMS, demonstrating unique aspects and potential commonalities that underpin mammalian reproductive isolation. PMID:26006188

  1. Mechanisms Underlying Mammalian Hybrid Sterility in Two Feline Interspecies Models.

    Science.gov (United States)

    Davis, Brian W; Seabury, Christopher M; Brashear, Wesley A; Li, Gang; Roelke-Parker, Melody; Murphy, William J

    2015-10-01

    The phenomenon of male sterility in interspecies hybrids has been observed for over a century, however, few genes influencing this recurrent phenotype have been identified. Genetic investigations have been primarily limited to a small number of model organisms, thus limiting our understanding of the underlying molecular basis of this well-documented "rule of speciation." We utilized two interspecies hybrid cat breeds in a genome-wide association study employing the Illumina 63 K single-nucleotide polymorphism array. Collectively, we identified eight autosomal genes/gene regions underlying associations with hybrid male sterility (HMS) involved in the function of the blood-testis barrier, gamete structural development, and transcriptional regulation. We also identified several candidate hybrid sterility regions on the X chromosome, with most residing in close proximity to complex duplicated regions. Differential gene expression analyses revealed significant chromosome-wide upregulation of X chromosome transcripts in testes of sterile hybrids, which were enriched for genes involved in chromatin regulation of gene expression. Our expression results parallel those reported in Mus hybrids, supporting the "Large X-Effect" in mammalian HMS and the potential epigenetic basis for this phenomenon. These results support the value of the interspecies feline model as a powerful tool for comparison to rodent models of HMS, demonstrating unique aspects and potential commonalities that underpin mammalian reproductive isolation.

  2. Mechanisms underlying rapid aldosterone effects in the kidney.

    LENUS (Irish Health Repository)

    Thomas, Warren

    2011-03-17

    The steroid hormone aldosterone is a key regulator of electrolyte transport in the kidney and contributes to both homeostatic whole-body electrolyte balance and the development of renal and cardiovascular pathologies. Aldosterone exerts its action principally through the mineralocorticoid receptor (MR), which acts as a ligand-dependent transcription factor in target tissues. Aldosterone also stimulates the activation of protein kinases and secondary messenger signaling cascades that act independently on specific molecular targets in the cell membrane and also modulate the transcriptional action of aldosterone through MR. This review describes current knowledge regarding the mechanisms and targets of rapid aldosterone action in the nephron and how aldosterone integrates these responses into the regulation of renal physiology.

  3. Understanding the Mechanisms Underlying Gambling Behaviour and Sleep.

    Science.gov (United States)

    Loft, Marisa H; Loo, Jasmine M Y

    2015-12-01

    Problem gambling and sleep difficulty threaten health. Using the basis of self-regulatory theory, potential mechanisms for these problems were investigated. Fifty-nine treatment-seeking gamblers completed the Pittsburgh Sleep Quality Index (sleep difficulty), the Sleep Hygiene Index (negative sleep habits), the Problem Gambling Severity Index and measures of self-regulatory capacity and arousability with data entered into regression analyses. Results supported the relationship between problem gambling and greater sleep difficulty (β = .18, t = 3.22, p change = .15, F(2, 57) = 12.14, β = -.45, t = -3.45, p change = .17, F(2, 57) = 13.57, β = -.28, t = -3.76, p behaviour and if targeted could reduce behavioural threats to health. PMID:25381635

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

    Science.gov (United States)

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

    2008-12-01

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

  5. Mechanisms underlying rapid aldosterone effects in the kidney.

    LENUS (Irish Health Repository)

    Thomas, Warren

    2012-02-01

    The steroid hormone aldosterone is a key regulator of electrolyte transport in the kidney and contributes to both homeostatic whole-body electrolyte balance and the development of renal and cardiovascular pathologies. Aldosterone exerts its action principally through the mineralocorticoid receptor (MR), which acts as a ligand-dependent transcription factor in target tissues. Aldosterone also stimulates the activation of protein kinases and secondary messenger signaling cascades that act independently on specific molecular targets in the cell membrane and also modulate the transcriptional action of aldosterone through MR. This review describes current knowledge regarding the mechanisms and targets of rapid aldosterone action in the nephron and how aldosterone integrates these responses into the regulation of renal physiology.

  6. Molecular mechanism for cavitation in water under tension

    CERN Document Server

    Menzl, Georg; Geiger, Philipp; Caupin, Frédéric; Abascal, Jose L F; Valeriani, Chantal; Dellago, Christoph

    2016-01-01

    Despite its relevance in biology and engineering, the molecular mechanism driving cavitation in water remains unknown. Using computer simulations, we investigate the structure and dynamics of vapor bubbles emerging from metastable water at negative pressures. We find that in the early stages of cavitation, bubbles are irregularly shaped and become more spherical as they grow. Nevertheless, the free energy of bubble formation can be perfectly reproduced in the framework of classical nucleation theory (CNT) if the curvature dependence of the surface tension is taken into account. Comparison of the observed bubble dynamics to the predictions of the macroscopic Rayleigh--Plesset (RP) equation, augmented with thermal fluctuations, demonstrates that the growth of nanoscale bubbles is governed by viscous forces. Combining the dynamical prefactor determined from the RP equation with the free energy of CNT yields an analytical expression for the cavitation rate that reproduces the simulation results very well over a w...

  7. Mechanisms underlying probucol-induced hERG-channel deficiency

    Directory of Open Access Journals (Sweden)

    Shi YQ

    2015-07-01

    Full Text Available Yuan-Qi Shi,1,* Cai-Chuan Yan,1,* Xiao Zhang,1 Meng Yan,1 Li-Rong Liu,1 Huai-Ze Geng,1 Lin Lv,1 Bao-Xin Li1,21Department of Pharmacology, Harbin Medical University, 2State-Province Key Laboratory of Biopharmaceutical Engineering, Harbin, Heilongjiang, People’s Republic of China*These authors contributed equally to this workAbstract: The hERG gene encodes the pore-forming α-subunit of the rapidly activating delayed rectifier potassium channel (IKr, which is important for cardiac repolarization. Reduction of IhERG due to genetic mutations or drug interferences causes long QT syndrome, leading to life-threatening cardiac arrhythmias (torsades de pointes or sudden death. Probucol is a cholesterol-lowering drug that could reduce hERG current by decreasing plasma membrane hERG protein expression and eventually cause long QT syndrome. Here, we investigated the mechanisms of probucol effects on IhERG and hERG-channel expression. Our data demonstrated that probucol reduces SGK1 expression, known as SGK isoform, in a concentration-dependent manner, resulting in downregulation of phosphorylated E3 ubiquitin ligase Nedd4-2 expression, but not the total level of Nedd4-2. As a result, the hERG protein reduces, due to the enhanced ubiquitination level. On the contrary, carbachol could enhance the phosphorylation level of Nedd4-2 as an alternative to SGK1, and thus rescue the ubiquitin-mediated degradation of hERG channels caused by probucol. These discoveries provide a novel mechanism of probucol-induced hERG-channel deficiency, and imply that carbachol or its analog may serve as potential therapeutic compounds for the handling of probucol cardiotoxicity.Keywords: long QT, hERG potassium channels, probucol, SGK1, Nedd4-2

  8. Uranium dioxide sintering Kinetics and mechanisms under controlled oxygen potentials

    International Nuclear Information System (INIS)

    The initial, intermediate, and final sintering stages of uranium dioxide were investigated as a function of stoichiometry and temperature by following the kinetics of the sintering reaction. Stoichiometry was controlled by means of the oxygen potential of the sintering atmosphere, which was measured continuously by solid-state oxygen sensors. Included in the kinetic study were microspheres originated from UO2 gels and UO2 pellets produced by isostatic pressing ceramic grade powders. The microspheres sintering behavior was examined using hot-stage microscopy and a specially designed high-temperature, controlled atmosphere furnace. This same furnace was employed as part of an optical dilatometer, which was utilized in the UO2 pellet sintering investigations. For controlling the deviations from stoichiometry during heat treatment, the oxygen partial pressure in the sintering atmosphere was varied by passing the gas through a Cu-Ti-Cu oxygen trap. The trap temperature determined the oxygen partial pressure of the outflowing mixture. Dry hydrogen was also used in some of the UO sub(2+x) sintering experiments. The determination of diametrial shrinkages and sintering indices was made utilizing high-speed microcinematography and ultra-microbalance techniques. It was observed that the oxygen potential has a substantial influence on the kinetics of the three sintering stages. The control of the sintering atmosphere oxygen partial pressure led to very fast densification of UO sub(2+x). Values in the interval 95.0 to 99.5% of theoretical density were reached in less than one minute. Uranium volume diffusion is the dominant mechanism in the initial and intermediate sintering stages. For the final stage, uranium grain boundary diffusion was found to be the main sintering mechanism. (Author)

  9. Neural mechanisms underlying neurooptometric rehabilitation following traumatic brain injury

    Directory of Open Access Journals (Sweden)

    Hudac CM

    2012-01-01

    Full Text Available Caitlin M Hudac1, Srinivas Kota1, James L Nedrow2, Dennis L Molfese1,31Department of Psychology, University of Nebraska-Lincoln, 2Oculi Vision Rehabilitation, 3Center for Brain, Biology, and Behavior, University of Nebraska-Lincoln, Lincoln, NEAbstract: Mild to severe traumatic brain injuries have lasting effects on everyday functioning. Issues relating to sensory problems are often overlooked or not addressed until well after the onset of the injury. In particular, vision problems related to ambient vision and the magnocellular pathway often result in posttrauma vision syndrome or visual midline shift syndrome. Symptoms from these syndromes are not restricted to the visual domain. Patients commonly experience proprioceptive, kinesthetic, vestibular, cognitive, and language problems. Neurooptometric rehabilitation often entails the use of corrective lenses, prisms, and binasal occlusion to accommodate the unstable magnocellular system. However, little is known regarding the neural mechanisms engaged during neurooptometric rehabilitation, nor how these mechanisms impact other domains. Event-related potentials from noninvasive electrophysiological recordings can be used to assess rehabilitation progress in patients. In this case report, high-density visual event-related potentials were recorded from one patient with posttrauma vision syndrome and secondary visual midline shift syndrome during a pattern reversal task, both with and without prisms. Results indicate that two factors occurring during the end portion of the P148 component (168–256 milliseconds poststimulus onset map onto two separate neural systems that were engaged with and without neurooptometric rehabilitation. Without prisms, neural sources within somatosensory, language, and executive brain regions engage inefficient magnocellular system processing. However, when corrective prisms were worn, primary visual areas were appropriately engaged. The impact of using early

  10. Mechanical behavior of enamel rods under micro-compression.

    Science.gov (United States)

    Yilmaz, Ezgi D; Schneider, Gerold A

    2016-10-01

    Exploring the structural strategies behind the optimized mechanical performance of hierarchical materials has been a focal point of extensive research over the past decades. Dental enamel is one such natural material, comprising a complicated hierarchical structure with a high level of mineral content. Bundles of hydroxyapatite nanofibers (level-1) Ø: 50nm form enamel rods (level-2) Ø: 5µm, which constitute bands (level-3) Ø: 50µm. While a number of studies in the last decade using advanced fracture mechanical methods have revealed an increasing trend in the fracture toughness of enamel with each additional level of hierarchy, there is still no general agreement on how hierarchical structuring affects the stiffness and strength of enamel. In this study, we identified the stiffness and strength values of the isolated rods (level-2) via micro-compression. The rods were tested in three different orientations with respect to the loading direction: parallel, perpendicular and oblique. The highest stress level withstood before catastrophic fracture was observed to be ~1500MPa in perpendicular orientation. In the oblique loading, the specimens failed by shearing and exhibited a damage-tolerant deformation behavior, which was attributed to the conjugation spots identified between the rods and interrod sheets. The elastic modulus was ~60GPa on average and similar in all orientations. The isotropy in stiffness was attributed to the mineral contacts residing between rods. This was verified by an analytical model derived for level-1 and extended over higher hierarchical levels. The experimental results obtained at level-2 were comparable to the compressive strength and stiffness values reported for level-1 and bulk enamel in the literature. In general, our results suggest that hierarchy has only a minor influence on the compressive properties of enamel. PMID:27415405

  11. Villitis of unknown aetiology: correlation of recurrence with clinical outcome.

    LENUS (Irish Health Repository)

    Feeley, L

    2010-01-01

    Villitis of unknown aetiology (VUA) is associated with adverse pregnancy outcome. Consequently, an ability to predict recurrence could be clinically relevant. We examined placentas where villitis was diagnosed in a previous pregnancy to establish the risk of recurrence and outcome. A total of 304 cases of VUA were diagnosed in our laboratory over a 4-year period. Subsequently, 19 of this cohort had a second placenta examined histologically. Recurrence and clinical outcome were recorded. Villitis recurred in 7 of 19 cases (37%). There was a high level of adverse pregnancy outcome in this cohort overall, characterised by small for gestational age infants and stillbirth, particularly in cases with high-grade villitis. We identified recurrent villitis more frequently than previously reported. Our findings confirm an association between high-grade villitis and poor outcome. Adequately powered prospective studies are required to determine if enhanced surveillance of subsequent pregnancies is indicated following a diagnosis of villitis.

  12. Algorithmic mechanisms for reliable crowdsourcing computation under collusion.

    Directory of Open Access Journals (Sweden)

    Antonio Fernández Anta

    Full Text Available We consider a computing system where a master processor assigns a task for execution to worker processors that may collude. We model the workers' decision of whether to comply (compute the task or not (return a bogus result to save the computation cost as a game among workers. That is, we assume that workers are rational in a game-theoretic sense. We identify analytically the parameter conditions for a unique Nash Equilibrium where the master obtains the correct result. We also evaluate experimentally mixed equilibria aiming to attain better reliability-profit trade-offs. For a wide range of parameter values that may be used in practice, our simulations show that, in fact, both master and workers are better off using a pure equilibrium where no worker cheats, even under collusion, and even for colluding behaviors that involve deviating from the game.

  13. Mechanisms of microstructural changes of fuel under irradiation

    International Nuclear Information System (INIS)

    Nuclear fuels are subjected to high levels of radiation damage mainly due to the slowing of fission fragments, which results in substantial modifications of the initial fuel microstructure. Microstructure changes alter practically all engineering fuel properties such as atomic transport or thermomechanical properties so understanding these changes is essential to predicting the performance of fuel elements. Also, with increasing burn-up, the fuel drifts away from its initial composition as the fission process produces new chemical elements. Because nuclear fuels operate at high temperature and usually under high-temperature gradients, damage annealing, foreign atom or defect clustering and migration occur on multiple time and length scales, which make long-term predictions difficult. The end result is a fuel microstructure which may show extensive differences on the scale of a single fuel pellet. The main challenge we are faced with is, therefore, to identify the phenomena occurring on the atom scale that are liable to have macroscopic effects that will determine the microstructure changes and ultimately the life-span of a fuel element. One step towards meeting this challenge is to develop and apply experimental or modelling methods capable of connecting events that occur over very short length and timescales to changes in the fuel microstructure over engineering length and timescales. In the first part of this chapter, we provide an overview of some of the more important microstructure modifications observed in nuclear fuels. The emphasis is placed on oxide fuels because of the extensive amount of data available in relation to these materials under neutron or ion irradiation. When possible and relevant, the specifics of other types of fuels such as metallic or carbide fuels are alluded to. Throughout this chapter but more specifically in the latter part, we attempt to give examples of how modelling and experimentation at various scales can provide us with

  14. Synaptic mechanisms underlying sparse coding of active touch.

    Science.gov (United States)

    Crochet, Sylvain; Poulet, James F A; Kremer, Yves; Petersen, Carl C H

    2011-03-24

    Sensory information is actively gathered by animals, but the synaptic mechanisms driving neuronal circuit function during active sensory processing are poorly understood. Here, we investigated the synaptically driven membrane potential dynamics during active whisker sensation using whole-cell recordings from layer 2/3 pyramidal neurons in the primary somatosensory barrel cortex of behaving mice. Although whisker contact with an object evoked rapid depolarization in all neurons, these touch responses only drove action potentials in ∼10% of the cells. Such sparse coding was ensured by cell-specific reversal potentials of the touch-evoked response that were hyperpolarized relative to action potential threshold for most neurons. Intercontact interval profoundly influenced touch-evoked postsynaptic potentials, interestingly without affecting the peak membrane potential of the touch response. Dual whole-cell recordings indicated highly correlated membrane potential dynamics during active touch. Sparse action potential firing within synchronized cortical layer 2/3 microcircuits therefore appears to robustly signal each active touch response.

  15. Testing of short superconducting wire samples under mechanical stress

    International Nuclear Information System (INIS)

    It is well known that degradation and training effects are serious problems in large-scale, complex-shaped superconducting magnets. This behavior is attributed to plastic deformation of the superconductor and/or the matrix, which is produced by forces in the coil and concomitant heating. The current-carrying capacity of short superconducting samples immersed in liquid helium in a magnetic field and subjected to a tensile test was investigated. It was found that the critical current of the superconducting wire was reduced by 25 percent as a result of mechanically straining it beyond the breaking point. At approximately 60 percent of the limiting load, voltage jumps corresponding to the short time the sample was in the normal state appeared in the sample after the current was turned on. This transition occurred only once at a given load. No voltage jumps were observed in the sample up to the critical current after the current was turned on again at the same or a reduced load. These results may serve as guidelines in studying the effects of training and degradation and developing methods of eliminating them in superconducting magnets

  16. RISK FACTORS FOR PANCREATIC CANCER: UNDERLYING MECHANISMS AND POTENTIAL TARGETS

    Directory of Open Access Journals (Sweden)

    Thomas eKolodecik

    2014-01-01

    Full Text Available Purpose of the review:Pancreatic cancer is extremely aggressive, forming highly chemo-resistant tumors, and has one of the worst prognoses. The evolution of this cancer is multi-factorial. Repeated acute pancreatic injury and inflammation are important contributing factors in the development of pancreatic cancer. This article attempts to understand the common pathways linking pancreatitis to pancreatic cancer.Recent Findings:Intracellular activation of both pancreatic enzymes and the transcription factor NF-kB are important mechanisms that induce acute pancreatitis. Recurrent pancreatic injury due to genetic susceptibility, environmental factors such as smoking, alcohol intake, and conditions such as obesity lead to increases in oxidative stress, impaired autophagy and constitutive activation of inflammatory pathways. These processes can stimulate pancreatic stellate cells, thereby increasing fibrosis and encouraging chronic disease development. Activation of oncogneic Kras mutations through inflammation, coupled with altered levels of tumor suppressor proteins (p53 and p16 can ultimately lead to development of pancreatic cancer. Summary:Although our understanding of pancreatitis and pancreatic cancer has tremendously increased over many years, much remains to be elucidated in terms of common pathways linking these conditions.

  17. Neurobiological mechanisms underlying the blocking effect in aversive learning.

    Science.gov (United States)

    Eippert, Falk; Gamer, Matthias; Büchel, Christian

    2012-09-19

    Current theories of classical conditioning assume that learning depends on the predictive relationship between events, not just on their temporal contiguity. Here we employ the classic experiment substantiating this reasoning-the blocking paradigm-in combination with functional magnetic resonance imaging (fMRI) to investigate whether human amygdala responses in aversive learning conform to these assumptions. In accordance with blocking, we demonstrate that significantly stronger behavioral and amygdala responses are evoked by conditioned stimuli that are predictive of the unconditioned stimulus than by conditioned stimuli that have received the same pairing with the unconditioned stimulus, yet have no predictive value. When studying the development of this effect, we not only observed that it was related to the strength of previous conditioned responses, but also that predictive compared with nonpredictive conditioned stimuli received more overt attention, as measured by fMRI-concurrent eye tracking, and that this went along with enhanced amygdala responses. We furthermore observed that prefrontal regions play a role in the development of the blocking effect: ventromedial prefrontal cortex (subgenual anterior cingulate) only exhibited responses when conditioned stimuli had to be established as nonpredictive for an outcome, whereas dorsolateral prefrontal cortex also showed responses when conditioned stimuli had to be established as predictive. Most importantly, dorsolateral prefrontal cortex connectivity to amygdala flexibly switched between positive and negative coupling, depending on the requirements posed by predictive relationships. Together, our findings highlight the role of predictive value in explaining amygdala responses and identify mechanisms that shape these responses in human fear conditioning.

  18. Neural mechanism underlying autobiographical memory modulated by remoteness and emotion

    Science.gov (United States)

    Ge, Ruiyang; Fu, Yan; Wang, DaHua; Yao, Li; Long, Zhiying

    2012-03-01

    Autobiographical memory is the ability to recollect past events from one's own life. Both emotional tone and memory remoteness can influence autobiographical memory retrieval along the time axis of one's life. Although numerous studies have been performed to investigate brain regions involved in retrieving processes of autobiographical memory, the effect of emotional tone and memory age on autobiographical memory retrieval remains to be clarified. Moreover, whether the involvement of hippocampus in consolidation of autobiographical events is time dependent or independent has been controversial. In this study, we investigated the effect of memory remoteness (factor1: recent and remote) and emotional valence (factor2: positive and negative) on neural correlates underlying autobiographical memory by using functional magnetic resonance imaging (fMRI) technique. Although all four conditions activated some common regions known as "core" regions in autobiographical memory retrieval, there are some other regions showing significantly different activation for recent versus remote and positive versus negative memories. In particular, we found that bilateral hippocampal regions were activated in the four conditions regardless of memory remoteness and emotional valence. Thus, our study confirmed some findings of previous studies and provided further evidence to support the multi-trace theory which believes that the role of hippocampus involved in autobiographical memory retrieval is time-independent and permanent in memory consolidation.

  19. Mechanisms underlying global stereopsis in fovea and periphery.

    Science.gov (United States)

    Witz, Nirel; Hess, Robert F

    2013-07-19

    To better understand the pooling properties underlying global stereopsis we examined the relationship between carrier luminance spatial frequency and modulator disparity spatial frequency. Thresholds for detecting global sinusoidal disparity corrugations of spatially band-pass noise were measured as a function of modulator disparity spatial frequency for both centrally and peripherally located stimuli using a standard 2-IFC task. We found a characteristic relationship that depended on modulator disparity spatial frequency. At high modulator disparity spatial frequencies (>1c/d), there is an optimal ratio of around 2.6, whereas at low modulator disparity spatial frequencies, there is an optimal absolute carrier luminance spatial frequency (i.e., 3c/d). In the periphery, vision is restricted to modulator disparity spatial frequencies below 1c/d and, as a consequence, following the above rule, there is an optimum absolute carrier luminance spatial frequency that reduces in spatial frequency with increasing eccentricity. This finding is consistent with there being more than one channel processing global stereo that is subsequently confirmed using a 2×2 AFC detection/discrimination paradigm. Furthermore, because of the different carrier/modulator relationships in central and peripheral vision, peripheral global stereo cannot be simply related to central global stereo by a scaling factor and thus cannot be simply due to cortical magnification, as originally thought. PMID:23680486

  20. Neural network mechanisms underlying stimulus driven variability reduction.

    Science.gov (United States)

    Deco, Gustavo; Hugues, Etienne

    2012-01-01

    It is well established that the variability of the neural activity across trials, as measured by the Fano factor, is elevated. This fact poses limits on information encoding by the neural activity. However, a series of recent neurophysiological experiments have changed this traditional view. Single cell recordings across a variety of species, brain areas, brain states and stimulus conditions demonstrate a remarkable reduction of the neural variability when an external stimulation is applied and when attention is allocated towards a stimulus within a neuron's receptive field, suggesting an enhancement of information encoding. Using an heterogeneously connected neural network model whose dynamics exhibits multiple attractors, we demonstrate here how this variability reduction can arise from a network effect. In the spontaneous state, we show that the high degree of neural variability is mainly due to fluctuation-driven excursions from attractor to attractor. This occurs when, in the parameter space, the network working point is around the bifurcation allowing multistable attractors. The application of an external excitatory drive by stimulation or attention stabilizes one specific attractor, eliminating in this way the transitions between the different attractors and resulting in a net decrease in neural variability over trials. Importantly, non-responsive neurons also exhibit a reduction of variability. Finally, this reduced variability is found to arise from an increased regularity of the neural spike trains. In conclusion, these results suggest that the variability reduction under stimulation and attention is a property of neural circuits. PMID:22479168

  1. Neural network mechanisms underlying stimulus driven variability reduction.

    Directory of Open Access Journals (Sweden)

    Gustavo Deco

    Full Text Available It is well established that the variability of the neural activity across trials, as measured by the Fano factor, is elevated. This fact poses limits on information encoding by the neural activity. However, a series of recent neurophysiological experiments have changed this traditional view. Single cell recordings across a variety of species, brain areas, brain states and stimulus conditions demonstrate a remarkable reduction of the neural variability when an external stimulation is applied and when attention is allocated towards a stimulus within a neuron's receptive field, suggesting an enhancement of information encoding. Using an heterogeneously connected neural network model whose dynamics exhibits multiple attractors, we demonstrate here how this variability reduction can arise from a network effect. In the spontaneous state, we show that the high degree of neural variability is mainly due to fluctuation-driven excursions from attractor to attractor. This occurs when, in the parameter space, the network working point is around the bifurcation allowing multistable attractors. The application of an external excitatory drive by stimulation or attention stabilizes one specific attractor, eliminating in this way the transitions between the different attractors and resulting in a net decrease in neural variability over trials. Importantly, non-responsive neurons also exhibit a reduction of variability. Finally, this reduced variability is found to arise from an increased regularity of the neural spike trains. In conclusion, these results suggest that the variability reduction under stimulation and attention is a property of neural circuits.

  2. Mechanical Model for Dynamic Behavior of Concrete Under Impact Loading

    Science.gov (United States)

    Sun, Yuanxiang

    Concrete is a geo-material which is used substantively in the civil building and military safeguard. One coupled model of damage and plasticity to describe the complex behavior of concrete subjected to impact loading is proposed in this research work. The concrete is assumed as homogeneous continuum with pre-existing micro-cracks and micro-voids. Damage to concrete is caused due to micro-crack nucleation, growth and coalescence, and defined as the probability of fracture at a given crack density. It induces a decrease of strength and stiffness of concrete. Compaction of concrete is physically a collapse of the material voids. It produces the plastic strain in the concrete and, at the same time, an increase of the bulk modulus. In terms of crack growth model, micro-cracks are activated, and begin to propagate gradually. When crack density reaches a critical value, concrete takes place the smashing destroy. The model parameters for mortar are determined using plate impact experiment with uni-axial strain state. Comparison with the test results shows that the proposed model can give consistent prediction of the impact behavior of concrete. The proposed model may be used to design and analysis of concrete structures under impact and shock loading. This work is supported by State Key Laboratory of Explosion science and Technology, Beijing Institute of Technology (YBKT14-02).

  3. Particle behavior and char burnout mechanisms under pressurized combustion conditions

    Energy Technology Data Exchange (ETDEWEB)

    Bauer, C.M.; Spliethoff, H.; Hein, K.R.G.

    1999-07-01

    Combined cycle systems with coal-fired gas turbines promise highest cycle efficiencies for this fuel. Pressurized pulverized coal combustion, in particular, yields high cycle efficiencies due to the high flue gas temperatures possible. The main problem, however, is to ensure a flue gas clean enough to meet the high gas turbine standards with a dirty fuel like coal. On the one hand, a profound knowledge of the basic chemical and physical processes during fuel conversion under elevated pressures is required whereas on the other hand suitable hot gas cleaning systems need to be developed. The objective of this work was to provide experimental data to enable a detailed description of pressurized coal combustion processes. A series of experiments were performed with two German hvb coals, Ensdorf and Goettelborn, and one German brown coal, Garzweiler, using a semi-technical scale pressurized entrained flow reactor. The parameters varied in the experiments were pressure, gas temperature and bulk gas oxygen concentration. A two-color pyrometer was used for in-situ determination of particle surface temperatures and particle sizes. Flue gas composition was measured and solid residue samples taken and subsequently analyzed. The char burnout reaction rates were determinated varying the parameters pressure, gas temperature and initial oxygen concentration. Variation of residence time was achieved by taking the samples at different points along the reaction zone. The most influential parameters on char burnout reaction rates were found to be oxygen partial pressure and fuel volatile content. With increasing pressure the burn-out reactions are accelerated and are mostly controlled by product desorption and pore diffusion being the limiting processes. The char burnout process is enhanced by a higher fuel volatile content.

  4. Photodegradation kinetics, products and mechanism of timolol under simulated sunlight

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Yong, E-mail: ychen@hust.edu.cn [School of Environmental Science and Engineering, Huazhong University of Science and Technology, Wuhan 430074 (China); Liang, Qi; Zhou, Danna [College of Material Science and Chemical Engineering, China University of Geosciences, Wuhan 430074 (China); Wang, Zongping, E-mail: zongpingw@hust.edu.cn [School of Environmental Science and Engineering, Huazhong University of Science and Technology, Wuhan 430074 (China); Tao, Tao [School of Environmental Science and Engineering, Huazhong University of Science and Technology, Wuhan 430074 (China); Zuo, Yuegang [Department of Chemistry and Biochemistry, University of Massachusetts Dartmouth, 285 Old Westport Road, North Dartmouth, MA 02747 (United States)

    2013-05-15

    Highlights: ► The indirect degradation of timolol is first investigated in fulvic acid solution. ► {sup 3}FA{sup *} and {sup 1}O{sub 2} accounted for the degradation of timolol in the aerated FA solutions. ► The presence of halides inhibited the degradation in the order of Cl{sup −} < Br{sup −} < I{sup −}. ► The role of I{sup −} in the degradation was first found to be concentration-dependent. ► The photoproducts of timolol were identified by LC-DAD/ESI-MS/MS analysis. -- Abstract: The photodegradation of β-blocker timolol in fulvic acid (FA) solution was investigated under simulated sunlight. The triplet excited state of FA ({sup 3}FA{sup *}) and singlet oxygen ({sup 1}O{sub 2}) were the main reactive species responsible for the degradation of timolol in the aerated FA solutions. Both dissolved oxygen and iodide ions (I{sup −}) are the efficient quenchers of {sup 3}FA{sup *}. The photodegradation was drastically accelerated after removing the dissolved oxygen. The presence of I{sup −} inhibited the photosensitized degradation of timolol in the deoxygenated FA solutions, whereas the role of I{sup −} in the reaction was concentration-dependent in the aerated solutions. The other halide ions such as chloride (Cl{sup −}) and bromide (Br{sup −}) exhibited less effect on the photodegradation of timolol in both aerated and deoxygenated solutions. By LC-DAD/ESI-MS/MS analysis, the photoproducts of timolol in both aerated and deoxygenated FA solutions were identified. Electron transfer interaction occurred between {sup 3}FA{sup *} and amine moiety of timolol, leading to the cleavage of C–O bond in the side chain and oxidation of the hexatomic ring. These findings suggest the photosensitized degradation was a significant pathway for the elimination of timolol in natural waters.

  5. Mechanism of attenuation of leptin signaling under chronic ligand stimulation

    Directory of Open Access Journals (Sweden)

    Bamberg-Lemper Simone

    2010-01-01

    Full Text Available Abstract Background Leptin is an adipocyte-derived hormone that acts via its hypothalamic receptor (LEPRb to regulate energy balance. A downstream effect essential for the weight-regulatory action of leptin is the phosphorylation and activation of the latent transcription factor STAT3 by LEPRb-associated Janus kinases (JAKs. Obesity is typically associated with chronically elevated leptin levels and a decreased ability of LEPRb to activate intracellular signal transduction pathways (leptin resistance. Here we have studied the roles of the intracellular tyrosine residues in the negative feedback regulation of LEPRb-signaling under chronic leptin stimulation. Results Mutational analysis showed that the presence of either Tyr985 and Tyr1077 in the intracellular domain of LEPRb was sufficient for the attenuation of STAT3 phosphorylation, whereas mutation of both tyrosines rendered LEPRb resistant to feedback regulation. Overexpression and RNA interference-mediated downregulation of suppressor of cytokine signaling 3 (SOCS3 revealed that both Tyr985 and Tyr1077 were capable of supporting the negative modulatory effect of SOCS3 in reporter gene assays. In contrast, the inhibitory effect of SOCS1 was enhanced by the presence of Tyr985 but not Tyr1077. Finally, the reduction of the STAT-phosphorylating activity of the LEPRb complex after 2 h of leptin stimulation was not accompanied by the dephosphorylation or degradation of LEPRb or the receptor-associated JAK molecule, but depended on Tyr985 and/or Tyr1077. Conclusions Both Tyr985 and Tyr1077 contribute to the negative regulation of LEPRb signaling. The inhibitory effects of SOCS1 and SOCS3 differ in the dependence on the tyrosine residues in the intracellular domain of LEPRb.

  6. Project on Transfer Mechanism of Radioactive Source Term Under Severe Accident

    Institute of Scientific and Technical Information of China (English)

    SUN; Xue-ting; JI; Song-tao; CHEN; Lin-lin

    2012-01-01

    <正>The "Transfer mechanism of radioactive source term under severe accident" is a sub-project of the research program of "Mechanism and phenomenology of severe accident". An aerosol transfer mechanism experimental facility is built to simulate the passive containment cooling system (PCCS) of advanced pressurizer reactors to research effects to the transfer process of fission products under severe accident. An advanced CFD method is also utilized to research the effects. The objective of this project is to understand

  7. Cochlear implantation in children with single-sided deafness: does aetiology and duration of deafness matter?

    Science.gov (United States)

    Arndt, Susan; Prosse, Susanne; Laszig, Roland; Wesarg, Thomas; Aschendorff, Antje; Hassepass, Frederike

    2015-01-01

    For adult patients with single-sided deafness (SSD), treatment with a cochlear implant (CI) is well established as an acceptable and beneficial hearing rehabilitation method administered routinely in clinical practice. In contrast, for children with SSD, CI has been applied less often to date, with the rationale to decide either on a case-by-case basis or under the realm of clinical research. The aim of our clinical study was to evaluate the longitudinal benefits of CI for a group of children diagnosed with SSD and to compare their outcomes with respect to patient characteristics. Evaluating a pool of paediatric SSD patients presenting for possible CI surgery revealed that the primary aetiology of deafness was congenital cochlear nerve deficiency. A subgroup of children meeting the CI candidacy criteria for the affected ear (the majority with acquired hearing loss) were enrolled in the study. Preliminary group results suggest substantial improvements in speech comprehension in noise and in the ability to localise sound, which was demonstrated through objective and subjective assessments after CI treatment for the group, with results varying from patient to patient. Our study shows a trend towards superior outcomes for children with acquired hearing loss and a shorter duration of hearing loss compared to congenitally deafened children who had a longer duration of SSD. This indicates an interactive influence of the age at onset, aetiology and duration of deafness upon the restoration of binaural integration and the overall benefits of sound stimulation to two ears after CI treatment. Continued longitudinal investigation of these children and further studies in larger groups may provide more guidance on the optimal timing of treatment for paediatric patients with acquired and congenital SSD.

  8. Coupled mechanical-electrical-thermal modeling for short-circuit prediction in a lithium-ion cell under mechanical abuse

    Science.gov (United States)

    Zhang, Chao; Santhanagopalan, Shriram; Sprague, Michael A.; Pesaran, Ahmad A.

    2015-09-01

    In order to better understand the behavior of lithium-ion batteries under mechanical abuse, a coupled modeling methodology encompassing the mechanical, electrical and thermal response is presented for predicting short-circuit under external crush. The combined mechanical-electrical-thermal response is simulated in a commercial finite element software LS-DYNA® using a representative-sandwich finite-element model, where electrical-thermal modeling is conducted after an instantaneous mechanical crush. The model includes an explicit representation of each individual component such as the active material, current collector, separator, etc., and predicts their mechanical deformation under quasi-static indentation. Model predictions show good agreement with experiments: the fracture of the battery structure under an indentation test is accurately predicted. The electrical-thermal simulation predicts the current density and temperature distribution in a reasonable manner. Whereas previously reported models consider the mechanical response exclusively, we use the electrical contact between active materials following the failure of the separator as a criterion for short-circuit. These results are used to build a lumped representative sandwich model that is computationally efficient and captures behavior at the cell level without resolving the individual layers.

  9. Electrical Response of Cement-Based Piezoelectric Ceramic Composites under Mechanical Loadings

    Directory of Open Access Journals (Sweden)

    Biqin Dong

    2011-01-01

    Full Text Available Electrical responses of cement-based piezoelectric ceramic composites under mechanical loadings are studied. A simple high order model is presented to explain the nonlinear phenomena, which is found in the electrical response of the composites under large mechanical loadings. For general situation, this nonlinear piezoelectric effect is quite small, and the composite is suitable for dynamic mechanical sensor as holding high static stability. The experimental results are consistent with the relationship quite well. The study shows that cement-based piezoelectric composite is suitable for potential application as dynamic mechanical sensor with excellent dynamic response and high static stability.

  10. Comparison of radiological findings and microbial aetiology of childhood pneumonia

    International Nuclear Information System (INIS)

    61 children were treated in hospital from 1981 to 1982 because of both radiologically and microbiologically verified viral or bacterial pneumonia. The chest radiographs were interpreted by two radiologists, not familiar with the clinical data, on two occasions three years apart, and only those patients with a definite alveolar or interstitial pneumonia at both evaluations were included in the present analysis. In addition, all patients had viral, mixed viral-bacterial or bacterial infections diagnosed by viral or bacterial antibody or antigen assays. Viral infection alone was seen in 7, mixed viral-bacterial infection in 8 and bacterial infection alone in 12 of the 27 patients with alveolar pneumonia. The respective figures were 13, 13 and 8 for the 34 patients with interstitial pneumonia. C-reactive protein concentration was greater than 40 mg/l in 15 of the patients with alveolar and in 11 of the patients with interstitial pneumonia. Thus 74% of the patients with alveolar and 62% with interstitial pneumonia had bacterial infection, either alone or as a mixed viral-bacterial infection. The results suggest that the presence of an alveolar infiltrate in a chest radiograph is a specific but insensitive indicator of bacterial pneumonia. It is concluded that patients with alveolar pneumonia should be treated with antibiotics. In patients with interstitial pneumonia, however, both viral and bacterial aetiology are possible. In those, the decision concerning antibiotic treatment should be based on clinical and laboratory findings. 21 refs., 4 tabs

  11. INCIDENCE, AETIOLOGY AND PATTERN OF MANDIBULAR FRACTURES IN PONDICHERRY

    Directory of Open Access Journals (Sweden)

    Karthik

    2015-12-01

    Full Text Available BACKGROUND The mandible is the second most commonly fractured part of the maxillofacial region after nasal bones. The incidence, etiology and pattern of mandibular fractures vary considerably among the different study population, there is a need to evaluate aspects of mandibular trauma in Pondicherry. This study was undertaken to evaluate the results of mandibular fractures treated in a population of Pondicherry. PATIENT AND METHOD A total of sixty nine patients treated for mandibular fractures at the Department Of Dentistry, Sri Manakula Vinayagar Medical College and Hospital, Pondicherry from January 2011 to December 2014 were retrospectively evaluated. The variables analyzed in the study were gender, age, aetiology, fracture site, method of treatment and complications. RESULTS This study included 106 fractures in 69 patients. The ratio of male to female was 16:1. The highest prevalence of fracture occurred in 21 to 30 years (37.7% and the minimum in patients over 61 years old. The most common cause of fractures were road traffic accident (RTA, 56.5% followed by fall. In our study most commonly reported fracture site was parasymphysis (37.7%, followed by angle (19.8% and condyle (19.8%. Mandibular fractures were generally treated by Open Reduction and Internal Fixation (ORIF in 76.4% of the patients. CONCLUSION The retrospective study of mandibular fractures has shown, road traffic accidents are main cause of fracture and young men in their 20s are predominantly affected.

  12. Comparison of radiological findings and microbial aetiology of childhood pneumonia

    Energy Technology Data Exchange (ETDEWEB)

    Korppi, M.; Kiekara, O.; Kosma, T.H.; Soimakallio, S. (Kuopio Univ. Hospital (Finland))

    1993-04-01

    61 children were treated in hospital from 1981 to 1982 because of both radiologically and microbiologically verified viral or bacterial pneumonia. The chest radiographs were interpreted by two radiologists, not familiar with the clinical data, on two occasions three years apart, and only those patients with a definite alveolar or interstitial pneumonia at both evaluations were included in the present analysis. In addition, all patients had viral, mixed viral-bacterial or bacterial infections diagnosed by viral or bacterial antibody or antigen assays. Viral infection alone was seen in 7, mixed viral-bacterial infection in 8 and bacterial infection alone in 12 of the 27 patients with alveolar pneumonia. The respective figures were 13, 13 and 8 for the 34 patients with interstitial pneumonia. C-reactive protein concentration was greater than 40 mg/l in 15 of the patients with alveolar and in 11 of the patients with interstitial pneumonia. Thus 74% of the patients with alveolar and 62% with interstitial pneumonia had bacterial infection, either alone or as a mixed viral-bacterial infection. The results suggest that the presence of an alveolar infiltrate in a chest radiograph is a specific but insensitive indicator of bacterial pneumonia. It is concluded that patients with alveolar pneumonia should be treated with antibiotics. In patients with interstitial pneumonia, however, both viral and bacterial aetiology are possible. In those, the decision concerning antibiotic treatment should be based on clinical and laboratory findings. 21 refs., 4 tabs.

  13. Gastrointestinal Perforation in Neonates: Aetiology and Risk Factors

    Directory of Open Access Journals (Sweden)

    Ekwunife Okechukwu Hyginus

    2013-07-01

    Full Text Available Background: Gastrointestinal perforation (GIP in neonates presents important challenges and mortality can be high. This is a report of recent experience with GIP in neonates in a developing country. Patients and methods: A retrospective review of 16 neonates treated for GIP in a 3 year period. Results: There were 9 males and 7 females, aged 0-28 days (median age =7days. Their weights at presentation ranged from 0.9 - 4.7kg (median =2.6. Five infants were premature. Twelve infants presented more than 72 hours after onset of symptoms. Plain abdominal radiographs showed peumoperitoneum in 9 infants. The cause of perforation was necrotising enterocolitis 6, intestinal obstruction 6, iatrogenic 3 and spontaneous 1. The site of perforation was ileum in 12 infants, stomach in 4 and colon in 4; 4 patients had involvement of more than one site. All the neonates underwent exploratory laparotomy with primary closure ( n=5 , resection and anastomosis( n=6, colostomy (n=3, Ileostomy ( n=2, partial gastrectomy (n=2 ,or gastrojejunostomy ( n=1. Two neonates had multiple procedures. Two very sick preterm babies had an initial peritoneal lavage. Surgical site infection is the commonest postoperative complication occurring in 9 infants. Anaesthesia sepsis and malnutrition is responsible for the seven deaths recorded.Conclusions: Neonatal GIP has multiple aetiologies; NEC is the most common cause. Major mortality risk factors include NEC, multiple perforations, delayed presentation and prematurity.

  14. Inflammatory aetiology of human myometrial activation tested using directed graphs.

    Directory of Open Access Journals (Sweden)

    2005-07-01

    Full Text Available THERE ARE THREE MAIN HYPOTHESES FOR THE ACTIVATION OF THE HUMAN UTERUS AT LABOUR: functional progesterone withdrawal, inflammatory stimulation, and oxytocin receptor activation. To test these alternatives we have taken information and data from the literature to develop causal pathway models for the activation of human myometrium. The data provided quantitative RT-PCR results on key genes from samples taken before and during labour. Principal component analysis showed that pre-labour samples form a homogenous group compared to those during labour. We therefore modelled the alternative causal pathways in non-labouring samples using directed graphs and statistically compared the likelihood of the different models using structural equations and D-separation approaches. Using the computer program LISREL, inflammatory activation as a primary event was highly consistent with the data (p = 0.925, progesterone withdrawal, as a primary event, is plausible (p = 0.499, yet comparatively unlikely, oxytocin receptor mediated initiation is less compatible with the data (p = 0.091. DGraph, a software program that creates directed graphs, produced similar results (p= 0.684, p= 0.280, and p = 0.04, respectively. This outcome supports an inflammatory aetiology for human labour. Our results demonstrate the value of directed graphs in determining the likelihood of causal relationships in biology in situations where experiments are not possible.

  15. Gastrointestinal Perforation in Neonates: Aetiology and Risk Factors

    Directory of Open Access Journals (Sweden)

    Hyginus Okechukwu Ekwunife

    2013-06-01

    Full Text Available Background: Gastrointestinal perforation (GIP in neonates presents important challenges and mortality can be high. This is a report of recent experience with GIP in neonates in a developing country.Patients and methods: A retrospective review of 16 neonates treated for GIP in a 3 year period.Results: There were 9 males and 7 females, aged 0-28 days (median age =7days. Their weights at presentation ranged from 0.9 - 4.7kg (median =2.6. Five infants were premature. Twelve infants presented more than 72 hours after onset of symptoms. Plain abdominal radiographs showed peumoperitoneum in 9 infants. The cause of perforation was necrotising enterocolitis 6, intestinal obstruction 6, iatrogenic 3 and spontaneous 1. The site of perforation was ileum in 12 infants, stomach in 4 and colon in 4; 4 patients had involvement of more than one site. All the neonates underwent exploratory laparotomy with primary closure ( n=5 , resection and anastomosis( n=6, colostomy (n=3, Ileostomy ( n=2, partial gastrectomy (n=2 ,or gastrojejunostomy ( n=1. Two neonates had multiple procedures. Two very sick preterm babies had an initial peritoneal lavage. Surgical site infection is the commonest postoperative complication occurring in 9 infants. Anaesthesia sepsis and malnutrition is responsible for the seven deaths recorded.Conclusions: Neonatal GIP has multiple aetiologies; NEC is the most common cause. Major mortality risk factors include NEC, multiple perforations, delayed presentation and prematurity.

  16. Multivariate refutation of aetiological hypotheses in non-experimental epidemiology.

    Science.gov (United States)

    Maclure, M

    1990-12-01

    Extension of Karl Popper's logic of refutation from the realm of contingency tables to multivariate modelling leads to the conclusion that rigorously scientific multivariate analysis in non-experimental epidemiology differs from the traditional quasi-scientific approach. Instead of aiming for high sensitivity in detecting aetiological agents, the goal in refutation is high specificity--to give the best defence of the 'innocence' of every exposure hypothesized as being a cause. Instead of 'forward selection' or 'backward elimination', multivariate refutation uses the method of 'forward elimination'. This entails a likelihood approach (which may be complemented by, but should be demarcated from, Bayesian methods) not only for statistical inference but also, by analogy, for study design and conduct: one starts with the conclusion (the estimate or hypothesis) and works backwards to the observations (the likelihood of the data or the design of the study). Differences in practice can sometimes be large, as illustrated by a study of hypothesized triggers of myocardial infarction. Multivariate refutation should replace the concept of multivariate modelling in non-experimental epidemiology.

  17. Interactivity effects in social media marketing on brand engagement: an investigation of underlying mechanisms

    NARCIS (Netherlands)

    M.L. Antheunis; G. van Noort

    2011-01-01

    Although, SNS advertising spending increases, research on SNS campaigning is still underexposed. First, this study aims to investigate the effect of SNS campaign interactivity on the receivers brand engagement, taking four underlying mechanisms into account (brand identification, campaign divergence

  18. News with an attitude: assessing the mechanisms underlying the effects of opinionated news

    NARCIS (Netherlands)

    M. Boukes; H.G. Boomgaarden; M. Moorman; C.H. de Vreese

    2014-01-01

    Opinionated news targets communities of likeminded viewers, relies on dramaturgical storytelling techniques, and shares characteristics with political satire. Accordingly, opinionated news should be understood as a specific form of political entertainment. We have investigated the mechanisms underly

  19. Large Deflections Mechanical Analysis of a Suspended Single-Wall Carbon Nanotube under Thermoelectrical Loading

    OpenAIRE

    Assaf Ya'akobovitz; Slava Krylov; Yael Hanein

    2011-01-01

    Following the recent progress in integrating single-wall carbon nanotubes (SWCNTs) into silicon-based micro-electromechanical systems (MEMS), new modeling tools are needed to predict their behavior under different loads, including thermal, electrical and mechanical. In the present study, the mechanical behavior of SWCNTs under thermoelectrical loading is analyzed using a large deflection geometrically nonlinear string model. The effect of the resistive heating was found to have a substantial ...

  20. Mechanical behaviors and phase transition of Ho2O3 nanocrystals under high pressure

    International Nuclear Information System (INIS)

    Mechanical properties and phase transition often show quite large crystal size dependent behavior, especially at nanoscale under high pressure. Here, we have investigated Ho2O3 nanocrystals with in-situ x-ray diffraction and Raman spectroscopy under high pressure up to 33.5 GPa. When compared to the structural transition routine cubic -> monoclinic -> hexagonal phase in bulk Ho2O3 under high pressure, the nano-sized Ho2O3 shows a much higher onset transition pressure from cubic to monoclinic structure and followed by a pressure-induced-amorphization under compression. The detailed analysis on the Q (Q = 2π/d) dependent bulk moduli reveals the nanosized Ho2O3 particles consist of a clear higher compressible shell and a less compressible core. Insight into these phenomena shed lights on micro-mechanism studies of the mechanical behavior and phase evolution for nanomaterials under high pressure, in general.

  1. micro-mechanical experimental investigation and modelling of strain and damage of argillaceous rocks under combined hydric and mechanical loads

    International Nuclear Information System (INIS)

    The hydro-mechanical behavior of argillaceous rocks, which are possible host rocks for underground radioactive nuclear waste storage, is investigated by means of micro-mechanical experimental investigations and modellings. Strain fields at the micrometric scale of the composite structure of this rock, are measured by the combination of environmental scanning electron microscopy, in situ testing and digital image correlation technique. The evolution of argillaceous rocks under pure hydric loading is first investigated. The strain field is strongly heterogeneous and manifests anisotropy. The observed nonlinear deformation at high relative humidity (RH) is related not only to damage, but also to the nonlinear swelling of the clay mineral itself, controlled by different local mechanisms depending on RH. Irreversible deformations are observed during hydric cycles, as well as a network of microcracks located in the bulk of the clay matrix and/or at the inclusion-matrix interface. Second, the local deformation field of the material under combined hydric and mechanical loadings is quantified. Three types of deformation bands are evidenced under mechanical loading, either normal to stress direction (compaction), parallel (microcracking) or inclined (shear). Moreover, they are strongly controlled by the water content of the material: shear bands are in particular prone to appear at high RH states. In view of understanding the mechanical interactions a local scale, the material is modeled as a composite made of non-swelling elastic inclusions embedded in an elastic swelling clay matrix. The internal stress field induced by swelling strain incompatibilities between inclusions and matrix, as well as the overall deformation, is numerically computed at equilibrium but also during the transient stage associated with a moisture gradient. An analytical micro-mechanical model based on Eshelby's solution is proposed. In addition, 2D finite element computations are performed. Results

  2. Mechanisms Underlying Lexical Access in Native and Second Language Processing of Gender and Number Agreement

    Science.gov (United States)

    Romanova, Natalia

    2013-01-01

    Despite considerable evidence suggesting that second language (L2) learners experience difficulties when processing morphosyntactic aspects of L2 in online tasks, the mechanisms underlying these difficulties remain unknown. The aim of this dissertation is to explore possible causes for the difficulties by comparing attentional mechanisms engaged…

  3. Cognitive mechanisms underlying disorganization of thought in a genetic syndrome (47,XXY)

    NARCIS (Netherlands)

    Van Rijn, Sophie; Aleman, Andre; De Sonneville, Leo; Swaab, Hanna

    2009-01-01

    Because of the risk for development of psychopathology such as psychotic symptoms, it has been suggested that studying men with the XXY karyotype may help in the search for underlying cognitive, neural and genetic mechanisms. The aim of this study was to identify cognitive mechanisms that may contri

  4. The aetiology of deep tissue injury: a literature review.

    Science.gov (United States)

    Peart, Joanna

    2016-08-11

    Deep tissue injury affects patients of all ages in a variety of healthcare settings. It is therefore essential that nurses are aware of the underlying pathogenesis, in order to accurately assess the pressure ulcer risk of vulnerable patients, and to subsequently reduce patient harm. The majority of pressure ulcers are avoidable, however, a variety of intrinsic and extrinsic factors can contribute towards the development of deep tissue injury. Understanding the body's internal responses to external pressure will enable nurses to recognise that a visual assessment alone may not necessarily identify patients at risk of deep tissue damage. This article reviews the evidence for the internal causative mechanisms of deep tissue injury, while linking to clinical practice and pressure ulcer prevention. PMID:27523755

  5. Comparison of radiological findings and microbial aetiology of childhood pneumonia.

    Science.gov (United States)

    Korppi, M; Kiekara, O; Heiskanen-Kosma, T; Soimakallio, S

    1993-04-01

    Sixty-one children were treated in hospital from 1981 to 1982 because of both radiologically and microbiologically verified viral or bacterial pneumonia. The chest radiographs were interpreted by two radiologists, not familiar with the clinical data, on two occasions three years apart, and only those patients with a definite alveolar (n = 27) or interstitial (n = 34) pneumonia at both evaluations were included in the present analysis. In addition, all patients had viral (n = 20), mixed viral-bacterial (n = 21) or bacterial (n = 20) infections diagnosed by viral or bacterial antibody or antigen assays. Viral infection alone was seen in 7 (26%), mixed viral-bacterial infection in 8 (30%) and bacterial infection alone in 12 (44%) of the 27 patients with alveolar pneumonia. The respective figures were 13 (38%), 13 (38%) and 8 (24%) for the 34 patients with interstitial pneumonia. C-reactive protein concentration was greater than 40 mg/l (a screening limit for viral and bacterial infections) in 15 (56%) of the patients with alveolar and in 11 (32%) of the patients with interstitial pneumonia. Thus 74% of the patients with alveolar and 62% with interstitial pneumonia had bacterial infection, either alone or as a mixed viral-bacterial infection. Our results suggest that the presence of an alveolar infiltrate in a chest radiograph is a specific but insensitive indicator of bacterial pneumonia. We conclude that patients with alveolar pneumonia should be treated with antibiotics. In patients with interstitial pneumonia, however, both viral and bacterial aetiology are possible. In those, the decision concerning antibiotic treatment should be based on clinical and laboratory findings. PMID:8318803

  6. AETIOLOGICAL PROFILE OF NEONATAL HYPERBILIRUBINEMIA IN NEONATAL INTENSIVE CARE UNIT OF GAUHATI MEDICAL COLLEGE AND HOSPITAL, GUWAHATI, ASSAM

    Directory of Open Access Journals (Sweden)

    Dulal

    2016-05-01

    Full Text Available BACKGROUND Jaundice is the most common problem in the first week of life. About 25-50% of all term neonates and higher percentage of preterm neonates develop clinical jaundice during neonatal period. Jaundice in newborn is a medical emergency, because unconjugated hyperbilirubinemia may cause bilirubin encephalopathy and needs urgent treatment. The objective of the study was to know the aetiology of hyperbilirubinemia in neonate admitted in neonatal intensive care unit of Gauhati Medical College and Hospital. METHODS This observational study was conducted in Neonatal Intensive Care Unit, Gauhati Medical College and Hospital, over a period of one year (February 2015 to January 2016. A total number of 520 neonates with hyperbilirubinemia were included in the present study. Data collection was done by history taking, clinical examination and essential laboratory tests. RESULTS In this study, out of 520 jaundiced neonates 251 (48.26% were term babies and 269 (51.74% were preterm babies. Physiological jaundice was seen in 224 (43.07% babies and pathological jaundice were 296 (56.93% babies. Among the various aetiologies causing neonatal hyperbilirubinemia, the most common causes were physiological jaundice 224 (43.07%, ABO incompatibility 108 (20.76%, Idiopathic 54 (10.43%, neonatal sepsis 36 (6.92%, G6PD deficiency 35 (6.73% and Rh Incompatibility 31 (5.96%. Other less common causes were cephalhematoma 15 (2.88%, intrauterine infection 7 (1.34%, breast milk jaundice 6 (1.15% and hypothyroidism 4 (0.76%. CONCLUSION We should investigate all newborns with pathological jaundice to find out the aetiology. Moreover, early detection of neonatal jaundice, proper monitoring and timely interventions like phototherapy, exchange blood transfusion and treating the underlying cause will reduce the morbidity and mortality among neonates. Thus, we can prevent mental retardation and cerebral palsy due to neonatal hyperbilirubinemia at the community level.

  7. Electro-oxidation process and mechanism of molybdenite decomposition under ultrasonic effect

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    According to the characteristics and shortcomings of the traditional roasting process and the electro-oxidation process in the molybdenum metallurgical industry,the ultrasound electro-oxidation process was proposed to strengthen the oxidative decomposition or leaching of molybdenum.Laboratory work was carried out in an electrochemical cell with 15 nun electrode spacing at 25℃ under ultrasonic effect.The optimum conditions were found through experiments.The electro-oxidation mechanism of molybdenite decomposition under ultrasonic was investigated.A model of electro-oxidation mechanism of molybdenum under ultrasonic was given.

  8. Chronic kidney disease of uncertain aetiology: prevalence and causative factors in a developing country

    OpenAIRE

    Jayatilake, Nihal; Mendis, Shanthi; Maheepala, Palitha; Mehta, Firdosi R

    2013-01-01

    Background This study describes chronic kidney disease of uncertain aetiology (CKDu), which cannot be attributed to diabetes, hypertension or other known aetiologies, that has emerged in the North Central region of Sri Lanka. Methods A cross-sectional study was conducted, to determine the prevalence of and risk factors for CKDu. Arsenic, cadmium, lead, selenium, pesticides and other elements were analysed in biological samples from individuals with CKDu and compared with age- and sex-matched ...

  9. The aetiology of acute and chronic pancreatitis over time in a hospital in Copenhagen

    DEFF Research Database (Denmark)

    Nøjgaard, Camilla; Bendtsen, Flemming; Matzen, Peter;

    2010-01-01

    The change in aetiology over time of acute and chronic pancreatitis has been sparsely described, as has also the validity of the diagnostic codes. The aim of the study was 1) to clarify whether the aetiology of acute and chronic pancreatitis changed during the period 1983-2005, and 2) to validate...... the diagnostic codes over time for acute and chronic pancreatitis registered in the Danish National Patient Registry (NPR) in the same period....

  10. Aetiology of community-acquired neonatal sepsis in low- and middle-income countries

    Directory of Open Access Journals (Sweden)

    Donald Waters

    2011-12-01

    Full Text Available 99% of the approximate 1 million annual neonatal deaths from life-threatening invasive bacterial infections occur in developing countries, at least 50% of which are from home births or community settings. Data concerning aetiology of sepsis in these settings are necessary to inform targeted therapy and devise management guidelines. This review describes and analyses the bacterial aetiology of community-acquired neonatal sepsis in developing countries.

  11. Numerical investigation of aerosolized drug delivery in the human lungs under mechanical ventilator conditions

    Science.gov (United States)

    Vanrhein, Timothy; Banerjee, Arindam

    2010-11-01

    Particle deposition for aerosolized drug delivery in the human airways is heavily dependent upon flow conditions. Numerical modeling techniques have proven valuable for determining particle deposition characteristics under steady flow conditions. For the case of patients under mechanical ventilation, however, flow conditions change drastically and there is an increased importance to understand particle deposition characteristics. This study focuses on mechanically ventilated conditions in the upper trachea-bronchial (TB) region of the human airways. Solution of the continuous phase flow is done under ventilator waveform conditions with a suitable turbulence model in conjunction with a realistic model of upper TB airways. A discrete phase Euler-Lagrange approach is applied to solve for particle deposition characteristics with a focus on the effect of the ventilator inlet waveform. The purpose of this study is to accurately model flow conditions in the upper TB airways under mechanically ventilated conditions with a focus on real-time patient specific targeted aerosolized drug delivery.

  12. Research of mechanics of the compact bone microvolume and porous ceramics under uniaxial compression

    Energy Technology Data Exchange (ETDEWEB)

    Kolmakova, T. V., E-mail: kolmakova@ftf.tsu.ru; Buyakova, S. P., E-mail: sbuyakova@ispms.tsc.ru; Kul’kov, S. N., E-mail: kulkov@ms.tsc.ru [Institute of Strength Physics and Materials Science of Siberian Branch of Russian Academy of Sciences (Russian Federation); National Research Tomsk State University (Russian Federation)

    2015-11-17

    The research results of the mechanics are presented and the effective mechanical characteristics under uniaxial compression of the simulative microvolume of the compact bone are defined subject to the direction of the collagen-mineral fibers, porosity and mineral content. The experimental studies of the mechanics are performed and the effective mechanical characteristics of the produced porous zirconium oxide ceramics are defined. The recommendations are developed on the selection of the ceramic samples designed to replace the fragment of the compact bone of a definite structure and mineral content.

  13. INFECTIOUS AETIOLOGY OF MARGINAL ZONE LYMPHOMA AND ROLE OF ANTI-INFECTIVE THERAPY

    Directory of Open Access Journals (Sweden)

    Salvatore Perrone

    2016-01-01

    Full Text Available Marginal zone lymphomas have been associated with several infectious agents covering both viral and bacterial pathogens and in some cases a clear aetiological role has been established. Pathogenetic mechanisms are currently not completely understood, however the role of chronic stimulation of the host immune response with persistent lymphocyte activation represents the most convincing explanation for lymphoproliferation. Gastric MALT lymphoma is strictly associated with Helicobacter pylori infection and various eradicating protocols, developed due to increasing antibiotic resistance, represent the first line therapy. The response rate to eradication is good with 80% of response at 1 year; this finding is also noteworthy because recapitulates a cancer cured only by antibacterial approach and it satisfies the Koch postulates of causation, establishing a causative relationship between Hp and gastric MALT lymphoma. Patients with chronic HCV infection have 5 times higher risk to develop MZL, in particular an association with splenic and nodal MZL has been shown in several studies. Moreover, there is evidence of lymphoma regression after antiviral therapy with interferon+ribavirin, thus rising hope that new available drugs, extremely effective against HCV replication, could improve outcome also in HCV-driven lymphomas. The rare cases of MZL localized to orbital fat and eye conjunctivas have been associated with Chlamydia psittaci infection carried by birds. Efficacy of antibacterial therapy against C. psittaci are conflicting and generally poorer thain gastric MALT. Finally some case-reports will cover the relationship between primary cutaneous B-cell Lymphomas and Borrelia Burgdorferi.

  14. Commentary: Not just genes--reclaiming a role for environmental influences on aetiology and outcome in autism. A commentary on Mandy and Lai (2016).

    Science.gov (United States)

    Charman, Tony; Chakrabarti, Bhismadev

    2016-03-01

    Mandy and Lai (2015) do the field a service in 'reclaiming' the role of pre- and postnatal environmental influences on the aetiology and course of autism spectrum conditions (ASC). This follows several decades where now discredited theories about putative psychogenic and biological disease models held sway, not least in the public mind. We discuss issues that arise from their review; including the need to identify how large the environmental influences on ASC are likely to be; the specificity of these environmental influences to ASC as opposed to a broader range of neurodevelopmental conditions and outcomes; how best to study complex interactions between genetic and environmental influences; and the promise of novel insights into their mechanisms of action. The review highlights current research that aims to better our understanding of the role of environmental factors in the aetiology and course of ASC and, in the near future, may offer the potential for personalised medicine approaches to intervention based on these discoveries.

  15. Evaluation of explosive sublimation as the mechanism of nanosecond laser ablation of tungsten under vacuum conditions

    Science.gov (United States)

    Oderji, Hassan Yousefi; Farid, Nazar; Sun, Liying; Fu, Cailong; Ding, Hongbin

    2016-08-01

    A non-equilibrium mechanism for nanosecond laser ablation is suggested herein, and its predictions are compared to the results of W experiments performed under vacuum conditions. A mechanism of particle formation is explained via this model, with partial sublimation of the superheated irradiated zone of the target considered to be the mechanism of laser ablation. In this study, a mixture of vapor and particles was explosively generated and subsequently prevented the rest of a laser pulse from reaching its intended target. This mechanism was found to play an essential role in the ablation of W under vacuum conditions, and it provides a theoretical justification for particle formation. Moreover, special considerations were taken into account for the expansion of plasma into a vacuum. The model was evaluated by measuring the mass of ablated particles using a quartz crystal deposition monitor and time-resolved optical emission spectroscopy. The results of this model were found to be in good agreement with experimental values.

  16. Chronic kidney disease of unknown aetiology in Sri Lanka: is cadmium a likely cause?

    Directory of Open Access Journals (Sweden)

    Peiris-John Roshini J

    2011-07-01

    Full Text Available Abstract Background The rising prevalence of chronic kidney disease (CKD and subsequent end stage renal failure necessitating renal replacement therapy has profound consequences for affected individuals and health care resources. This community based study was conducted to identify potential predictors of microalbuminuria in a randomly selected sample of adults from the North Central Province (NCP of Sri Lanka, where the burden of CKD is pronounced and the underlying cause still unknown. Methods Exposures to possible risk factors were determined in randomly recruited subjects (425 females and 461 males from selected areas of the NCP of Sri Lanka using an interviewer administered questionnaire. Sulphosalicylic acid and the Light Dependent Resister microalbumin gel filtration method was used for initial screening for microalbuminuria and reconfirmed by the Micral strip test. Results Microalbumnuria was detected in 6.1% of the females and 8.5% of the males. Smoking (p Conclusions Hypertension, diabetes mellitus, UTI, and smoking are known risk factors for microalbuminuria. The association between microalbuminuria and consumption of well water suggests an environmental aetiology to CKD in NCP. The causative agent is yet to be identified. Investigations for cadmium as a potential causative agent needs to be initiated.

  17. Modelling of damage initiation mechanism in rubber sheet composites under the static loading

    OpenAIRE

    Da Silva Botelho, T; N. Isac; E. Bayraktar

    2007-01-01

    Purpose: Modelling – Finite Element Analysis (FEA) of the damage initiation mechanisms in thin rubber sheet composites were carried out under static solicitation at room temperature. Natural rubber vulcanised and reinforced by carbon, NR is used in this study.Design/methodology/approach: Experimental results were compared with that of the Finite Element Analysis (FEA). Damage mechanism has been described with a threshold criterion to identify the tearing resistance, characteristic energy for ...

  18. Mechanical deformation of WC–Co composite micropillars under uniaxial compression

    OpenAIRE

    Tarragó Cifre, Jose María; Roa Rovira, Joan Josep; Jiménez Piqué, Emilio; Keown, Eugene; Fair, Jonathan; Llanes Pitarch, Luis Miguel

    2015-01-01

    In thiswork,WC–Co micropillars machined by focused ion beamhave been tested under uniaxial compression to investigate the stress–strain behavior and associated deformation mechanisms. The results indicate that yielding phenomena is evidenced by multiple strain bursts. Experimental data is found to fall within the bounds defined by the mechanical responses expected for an unconstrained Co-binder like model alloy and a bulk-like constrained binder region in WC–Co composites; capturing then l...

  19. A novel platform for in situ investigation of cells and tissues under mechanical strain

    OpenAIRE

    Ahmed, Wylie W.; Kural, Mehmet H.; Saif, Taher A.

    2010-01-01

    The mechanical micro-environment influences cellular responses such as migration, proliferation, differentiation, and apoptosis. Cells are subjected to mechanical stretching in vivo, e.g., epithelial cells during embryogenesis. Current methodologies do not allow high resolution in situ observation of cells and tissues under applied strain, which may reveal intracellular dynamics and the origin of cell mechanosensitivity. We have developed a novel polydimethylsiloxane (PDMS) substrate capable ...

  20. Adsorption mechanism of different coal ranks under variable temperature and pressure conditions

    Institute of Scientific and Technical Information of China (English)

    ZHANG Qing-ling

    2008-01-01

    Variable temperature and pressure adsorption tests were conducted on four coal samples with different coal ranks, under simulated temperatures and pressures corresponding to coal reservoirs at different depths. The regularity of the variation in the amounts of adsorption by coals under variable temperature and pressure and 30 ~C isothermal conditions are compared and the adsorption characteristics of coal under the composite effect of temperature and pressure were obtained. The adsorption test and data processing method of coal under variable temperature and pressure are presented and the effect of the mechanism of tempera-ture and pressure on the adsorption capacity of coal has been studied. The research results are of significant importance in the in-vestigation of coalbed methane storage mechanism and for the prediction of the amounts of coalbed methane at various depths.

  1. Mechanical model for yield strength of nanocrystalline materials under high strain rate loading

    Institute of Scientific and Technical Information of China (English)

    朱荣涛; 周剑秋; 马璐; 张振忠

    2008-01-01

    To understand the high strain rate deformation mechanism and determine the grain size,strain rate and porosity dependent yield strength of nanocrystalline materials,a new mechanical model based on the deformation mechanism of nanocrystalline materials under high strain rate loading was developed.As a first step of the research,the yield behavior of the nanocrystalline materials under high strain rate loading was mainly concerned in the model and uniform deformation was assumed for simplification.Nanocrystalline materials were treated as composites consisting of grain interior phase and grain boundary phase,and grain interior and grain boundary deformation mechanisms under high strain rate loading were analyzed,then Voigt model was applied to coupling grain boundary constitutive relation with mechanical model for grain interior phase to describe the overall yield mechanical behavior of nanocrystalline materials.The predictions by the developed model on the yield strength of nanocrysatlline materials at high strain rates show good agreements with various experimental data.Further discussion was presented for calculation results and relative experimental observations.

  2. CFD Analysis of Migration Mechanism of Source Term Under Severe Accident

    Institute of Scientific and Technical Information of China (English)

    CHEN; Lin-lin; SUN; Xue-ting; JI; Song-tao

    2013-01-01

    The analysis of the migration of source term under severe accident is one of the important aspects of‘Studies on Migration Mechanism of the Source Term under Severe Accident’,which is a significant task of the National Large Advanced PWR Research Program.This research aims at building up a method for analyzing fission product behavior in the containment with CFD code.The effect of PCCS(Passive

  3. Molecular mechanisms of tirapazamine (SR 4233, Win 59075)-induced hepatocyte toxicity under low oxygen concentrations.

    OpenAIRE

    Khan, S.; O'Brien, P. J.

    1995-01-01

    Previously we showed that tirapazamine (SR 4233, Win 59075) is cytotoxic towards hepatocytes under conditions of hypoxia but not in 10% or 95% oxygen and that bioreduction by DT-diaphorase or cytochrome P450 is not a major pathway. In the present study, we report that tirapazamine is highly cytotoxic to isolated rat hepatocytes maintained under 1% oxygen and the molecular cytotoxic mechanism has been elucidated. Cytotoxicity was prevented by the cytochrome P450 2E1 inhibitors phenyl imidazole...

  4. Model test study of evaporation mechanism of sand under constant atmospheric condition

    OpenAIRE

    Cui, Yu Jun; DING, Wenqi; Song, Weikang

    2014-01-01

    The evaporation mechanism of Fontainebleau sand using a large-scale model chamber is studied. First, the evaporation test on a layer of water above sand surface is performed under various atmospheric conditions, validating the performance of the chamber and the calculation method of actual evaporation rate by comparing the calculated and measured cumulative evaporations. Second,the evaporation test on sand without water layer is conducted under constant atmospheric condition. Both the evoluti...

  5. Superelastic damping of TiNi alloy wire under heavy mechanical shock in structural engineering

    Institute of Scientific and Technical Information of China (English)

    陈庆福; 田文彦; 左晓宝; 倪立峰

    2004-01-01

    Based on superelastic damping application in structural engineering, the damping characteristics of commercial Ti-50.8Ni(mole fraction, %) alloy have been systematically studied by adjusting frequency of mechanical shock, temperature, stress, strain and number of cycling. The results show that at extremely low frequency mechanical shock at room temperature, the superelastic damping capacity increases with controlled strain, and such capacity of each cycle is greater than 50%. When the frequency of mechanical shock is 0.1 - 0.3 Hz, the superelastic damping capacity above room temperature is relatively large at high strain; when the temperature approaches to Md,the damping begins at low stress. For specimen cycled under 0.5 Hz, above 6 % strain mechanical shock at relatively high temperature, further large-strain cycling exhibits more than 35% damping capacity. The superelastic damping of trained specimen is relatively stable at 20 - 50 ℃ and 0.1 - 0.5 Hz frequency mechanical shock.

  6. Modeling and numerical analysis of granite rock specimen under mechanical loading and fire

    Institute of Scientific and Technical Information of China (English)

    Luc Leroy Ngueyep. Mambou; Joseph Ndop; Jean-Marie Bienvenu Ndjaka

    2015-01-01

    The effect of ISO 834 fire on the mechanical properties of granite rock specimen submitted to uniaxial loading is numerically investigated. Based on Newton’s second law, the rate-equation model of granite rock specimen under mechanical load and fire is established. The effect of heat treatment on the me-chanical performance of granite is analyzed at the center and the ends of specimen. At the free end of granite rock specimen, it is shown that from 20 ?C to 500 ?C, the internal stress and internal strain are weak; whereas above 500 ?C, they start to increase rapidly, announcing the imminent collapse. At the center of specimen, the analysis of the internal stress and internal strain reveals that the fire reduces the mechanical performance of granite significantly. Moreover, it is found that after 3 min of exposure to fire, the mechanical energy necessary to fragment the granite can be reduced up to 80%.

  7. Structural and Mechanical Properties of Intermediate Filaments under Extreme Conditions and Disease

    Science.gov (United States)

    Qin, Zhao

    Intermediate filaments are one of the three major components of the cytoskeleton in eukaryotic cells. It was discovered during the recent decades that intermediate filament proteins play key roles to reinforce cells subjected to large-deformation as well as participate in signal transduction. However, it is still poorly understood how the nanoscopic structure, as well as the biochemical properties of these protein molecules contribute to their biomechanical functions. In this research we investigate the material function of intermediate filaments under various extreme mechanical conditions as well as disease states. We use a full atomistic model and study its response to mechanical stresses. Learning from the mechanical response obtained from atomistic simulations, we build mesoscopic models following the finer-trains-coarser principles. By using this multiple-scale model, we present a detailed analysis of the mechanical properties and associated deformation mechanisms of intermediate filament network. We reveal the mechanism of a transition from alpha-helices to beta-sheets with subsequent intermolecular sliding under mechanical force, which has been inferred previously from experimental results. This nanoscale mechanism results in a characteristic nonlinear force-extension curve, which leads to a delocalization of mechanical energy and prevents catastrophic fracture. This explains how intermediate filament can withstand extreme mechanical deformation of > 1 00% strain despite the presence of structural defects. We combine computational and experimental techniques to investigate the molecular mechanism of Hutchinson-Gilford progeria syndrome, a premature aging disease. We find that the mutated lamin tail .domain is more compact and stable than the normal one. This altered structure and stability may enhance the association of intermediate filaments with the nuclear membrane, providing a molecular mechanism of the disease. We study the nuclear membrane association

  8. The Mediated MIMIC Model for Understanding the Underlying Mechanism of DIF

    Science.gov (United States)

    Cheng, Ying; Shao, Can; Lathrop, Quinn N.

    2016-01-01

    Due to its flexibility, the multiple-indicator, multiple-causes (MIMIC) model has become an increasingly popular method for the detection of differential item functioning (DIF). In this article, we propose the mediated MIMIC model method to uncover the underlying mechanism of DIF. This method extends the usual MIMIC model by including one variable…

  9. Deformation Microstructures and Creep Mechanisms in Advanced ZR-Based Cladding Under Biazal Loading

    Energy Technology Data Exchange (ETDEWEB)

    K. Linga (KL) Murty

    2008-08-11

    Investigate creep behavior of Zr-based cladding tubes with attention to basic creep mechanisms and transitions in them at low stresses and/or temperatures and study the dislocation microstructures of deformed samples for correlation with the underlying micromechanism of creep

  10. Compressive damage mechanism of GFRP composites under off-axis loading: Experimental and numerical investigations

    DEFF Research Database (Denmark)

    Zhou, H.W.; Li, H.Y.; Gui, L.L.;

    2013-01-01

    Experimental and computational studies of the microscale mechanisms of damage formation and evolution in unidirectional glass fiber reinforced polymer composites (GFRP) under axial and off-axis compressive loading are carried out. A series of compressive testing of the composites with different a...

  11. Experimental Investigation on Mechanical Behavior and Permeability Evolution of a Porous Limestone Under Compression

    Science.gov (United States)

    Han, B.; Xie, S. Y.; Shao, J. F.

    2016-09-01

    This paper presents an experimental investigation on the mechanical behavior and permeability evolution of a typical porous limestone, the Anstrude limestone. Hydrostatic and triaxial compression tests are first performed under drained condition to study the basic mechanical behavior of the porous rock. Permeability measurement under both hydrostatic and triaxial compression is carried out for investigating effects of stress state on the permeability evolution along the axial direction of sample. The obtained results allow to identifying two basic plastic deformation mechanisms, the plastic shearing and pore collapse, and their effects on the permeability evolution. Under low confining pressures, the permeability diminution in the elastic phase is controlled by deviatoric stress. After the onset of plastic shearing, the deviatoric stress induces a plastic volumetric dilatation and a permeability increase. When the deviatoric stress reaches the peak strength or after the onset of shear bands, the permeability slightly decreases. Under high confining pressures, the deviatoric stress also induces a permeability diminution before the onset of plastic pore collapse. After the onset of pore collapse, the deviatoric stress leads to a plastic volumetric compaction and permeability decrease. When the deviatoric stress reaches the onset of plastic shearing, the two plastic mechanisms are in competition, the permeability continuously decreases but with a reduced rate. Finally, after the compaction-dilatation transition, the plastic shearing dominates the deformation process while the pore collapse still controls the permeability evolution.

  12. ANALYSIS OF THE MECHANICAL STATE AT HOMOGENEOUS DISLOCATION GENERATION UNDER SHOCK WAVE LOADING

    OpenAIRE

    Popov, G.; Gagov, V.

    1988-01-01

    The strains and stresses under shock wave loading of metals are analysed. The assumtion for elastic behaviour at the shock front is used as it was proposed in the Meyers model for homogeneous dislocation generation. The mechanical state in plane and oblique shock wave is compared with the experimenta1 data for the residual hardness of Hadfield steel.

  13. Relative Damage Stress: Dominant Mechanical Factor for the Failure of Soldered Joints under Temperature Cycling

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    By temperature normalization of the concept of equivalent damage stress proposed by Lemaitre,a new concept of relative damage stress has been put forward as the dominant mechanical factor for the failure of soldered joints under temperature cycling. Finite element numerical simulation results showed that the highest value of relative damage stress occurred at the high temperaturehold time during temperature cycling history.

  14. On the mechanical behaviour of a butt jointed thermoplastic composite under bending

    NARCIS (Netherlands)

    Baran, I.; Warnet, L.; Akkerman, R.; Thomsen, O.T

    2015-01-01

    In the present work, the mechanical behavior of a recently developed novel butt jointed thermoplastic composite was investigated under bending conditions. The laminated skin and the web were made of carbon fiber (AS4) and polyetherketoneketone (PEKK). The butt joint (filler) was injection molded fro

  15. Effects of competition on endurance performance and the underlying psychological and physiological mechanisms.

    Science.gov (United States)

    Cooke, Andrew; Kavussanu, Maria; McIntyre, David; Ring, Christopher

    2011-03-01

    Competition can influence performance, however, the underlying psychological and physiological mechanisms are poorly understood. To address this issue we tested mechanisms underlying the competition-performance relationship. Measures of anxiety, effort, enjoyment, autonomic activity and muscle activity were obtained from 94 participants during a handgrip endurance task completed in individual and competition conditions. Competition improved endurance performance, increased anxiety, effort, enjoyment, heart rate and muscle activity, and decreased heart rate variability, R-wave to pulse interval and pulse amplitude. Enjoyment fully mediated whereas effort and heart rate variability partially mediated the effects of competition on performance. In addition, anxiety moderated the competition-performance relationship; those with lower anxiety performed better in competition. We confirm that competition elicits effects on performance through psychological and physiological pathways, and identify mechanisms that underlie improved endurance performance during competition. PMID:21295108

  16. Mechanical shield support for longwall working under artificial roof used at the Petrosani collieries

    Energy Technology Data Exchange (ETDEWEB)

    Koronka, F.

    1979-04-01

    The article presents a new mechanical shield support meant for longwall workings under artificial roof in the Valea Jiului mines, tested and used with good results in the third seam of the Lupeni and Lonea collieries. Evaluating the results of the underground tests, it is concluded that the mechanical shield support meets the requirements of the working conditions under artificial roof in the third seam. One of the advantages it provides is that it can be easily adapted to the height variations of the longwalls, controlling the underground pressure, ensuring complete working security for the working personnel and providing a gentle lowering of the artificial roof without damaging the wire mesh. The mechanical shield support is compact, easy to set up and dismount and easy to control. (In Romanian)

  17. Large Deflections Mechanical Analysis of a Suspended Single-Wall Carbon Nanotube under Thermoelectrical Loading

    Directory of Open Access Journals (Sweden)

    Assaf Ya'akobovitz

    2011-01-01

    Full Text Available Following the recent progress in integrating single-wall carbon nanotubes (SWCNTs into silicon-based micro-electromechanical systems (MEMS, new modeling tools are needed to predict their behavior under different loads, including thermal, electrical and mechanical. In the present study, the mechanical behavior of SWCNTs under thermoelectrical loading is analyzed using a large deflection geometrically nonlinear string model. The effect of the resistive heating was found to have a substantial influence on the SWCNTs behavior, including significant enhancement of the strain (up to the millistrains range and buckling due to the thermal expansion. The effect of local buckling sites was also studied and was found to enhance the local strain. The theoretical and numerical results obtained in the present study demonstrate the importance of resistive heating in the analysis of SWCNTs and provide an additional insight into the unique mechanics of suspended SWCNTs.

  18. Electronic and Mechanical Properties of Tetragonal Nb2Al Under High Pressure: First-Principles Calculations

    Science.gov (United States)

    Jiao, Zhen; Liu, Qi-Jun; Liu, Fu-Sheng; Wang, Wen-Peng; Wang, Yi-Gao; Li, Yong; Liu, Zheng-Tang

    2016-04-01

    We have investigated the structure, density of states, mechanical stability, elastic properties, and Debye temperature of tetragonal Nb2Al under high pressure using the generalized gradient approximation WC (GGA-WC) functional within density functional theory (DFT). Our obtained lattice constants were in good agreement with the reported experimental and theoretical data at zero pressure. The volume decreased with the increasing pressure. The effects of pressure on the electronic properties have been discussed. The elastic constants under pressure have been calculated, which all satisfied the stability criterion, meaning that tetragonal Nb2Al was mechanical stability from 0 to 100 GPa. Then, the mechanical properties including bulk modulus B, shear modulus G, Young's modulus E, G/B, and Poisson's ratio ν under pressure were determined using the Voigt-Reuss-Hill method. The G/B value suggested that tetragonal Nb2Al exhibited ductile behavior under pressure. Poisson's ratio indicated that the interatomic forces in tetragonal Nb2Al were mainly central forces. Finally, the transverse, longitudinal, and average sound velocities and Debye temperature of tetragonal Nb2Al under pressure have been estimated.

  19. Dual mechanisms regulate ecosystem stability under decade-long warming and hay harvest.

    Science.gov (United States)

    Shi, Zheng; Xu, Xia; Souza, Lara; Wilcox, Kevin; Jiang, Lifen; Liang, Junyi; Xia, Jianyang; García-Palacios, Pablo; Luo, Yiqi

    2016-01-01

    Past global change studies have identified changes in species diversity as a major mechanism regulating temporal stability of production, measured as the ratio of the mean to the standard deviation of community biomass. However, the dominant plant functional group can also strongly determine the temporal stability. Here, in a grassland ecosystem subject to 15 years of experimental warming and hay harvest, we reveal that warming increases while hay harvest decreases temporal stability. This corresponds with the biomass of the dominant C4 functional group being higher under warming and lower under hay harvest. As a secondary mechanism, biodiversity also explains part of the variation in temporal stability of production. Structural equation modelling further shows that warming and hay harvest regulate temporal stability through influencing both temporal mean and variation of production. Our findings demonstrate the joint roles that dominant plant functional group and biodiversity play in regulating the temporal stability of an ecosystem under global change. PMID:27302085

  20. The Mechanical Analysis and Experimental Study of Shock Wave Effect of Electrical Discharge under Water In Filth Cleaning

    Institute of Scientific and Technical Information of China (English)

    Deng Qilin; Zhang Lei; Zhou Jinjin

    2004-01-01

    Filth adhering to metal pipes can be cleaned by shock wave generated by electrical discharge under water. The mechanism of shock wave effect of electrical discharge under water on filth cleaning is analyzed by building a mechanical model. A metal pipe coated with cement to simulate real filth is cleaned by using electrical discharge under water. The experimental results confirm the mechanical analysis and also show the technology of electrical discharge under water is an very effective method for filth cleaning.

  1. TS-EUROTRAIN: A European-wide investigation and training network on the aetiology and pathophysiology of Gilles de la Tourette Syndrome

    Directory of Open Access Journals (Sweden)

    Natalie J Forde

    2016-08-01

    Full Text Available Gilles de la Tourette Syndrome (GTS is characterised by the presence of multiple motor and phonic tics with a fluctuating course of intensity, frequency and severity. Up to 90% of patients with GTS present with comorbid conditions, most commonly attention-deficit/hyperactivity disorder (ADHD and obsessive-compulsive disorder (OCD, thus providing an excellent model for the exploration of shared aetiology across disorders. TS-EUROTRAIN (FP7-PEOPLE-2012-ITN, Grant Agr.No.316978 is a Marie Curie Initial Training Network (http://ts-eurotrain.eu that aims to elucidate the complex aetiology of the onset and clinical course of GTS, investigate the neurobiological underpinnings of GTS and related disorders, translate research findings into clinical applications and establish a pan-European infrastructure for the study of GTS. This includes the challenges of (i assembling a large genetic database for the evaluation of the genetic architecture with high statistical power; (ii exploring the role of gene-environment interactions including the effects of epigenetic phenomena; (iii employing endophenotype-based approaches to understand the shared aetiology between GTS, OCD and ADHD; (iv establishing a developmental animal model for GTS; (v gaining new insights into the neurobiological mechanisms of GTS via cross-sectional and longitudinal neuroimaging studies; and (vi partaking in outreach activities including the dissemination of scientific knowledge about GTS to the public. Fifteen partners from academia and industry and twelve PhD candidates pursue the project. Our ultimate aims are to elucidate the complex aetiology and neurobiological underpinnings of GTS, translate research findings into clinical applications and establish Pan-European infrastructure for the study of GTS and associated disorders.

  2. A triphasic constrained mixture model of engineered tissue formation under in vitro dynamic mechanical conditioning.

    Science.gov (United States)

    Soares, Joao S; Sacks, Michael S

    2016-04-01

    While it has become axiomatic that mechanical signals promote in vitro engineered tissue formation, the underlying mechanisms remain largely unknown. Moreover, efforts to date to determine parameters for optimal extracellular matrix (ECM) development have been largely empirical. In the present work, we propose a two-pronged approach involving novel theoretical developments coupled with key experimental data to develop better mechanistic understanding of growth and development of dense connective tissue under mechanical stimuli. To describe cellular proliferation and ECM synthesis that occur at rates of days to weeks, we employ mixture theory to model the construct constituents as a nutrient-cell-ECM triphasic system, their transport, and their biochemical reactions. Dynamic conditioning protocols with frequencies around 1 Hz are described with multi-scale methods to couple the dissimilar time scales. Enhancement of nutrient transport due to pore fluid advection is upscaled into the growth model, and the spatially dependent ECM distribution describes the evolving poroelastic characteristics of the scaffold-engineered tissue construct. Simulation results compared favorably to the existing experimental data, and most importantly, distinguish between static and dynamic conditioning regimes. The theoretical framework for mechanically conditioned tissue engineering (TE) permits not only the formulation of novel and better-informed mechanistic hypothesis describing the phenomena underlying TE growth and development, but also the exploration/optimization of conditioning protocols in a rational manner. PMID:26055347

  3. Study of the damaging mechanisms of a copper / carbon - carbon composite under thermomechanical loading

    International Nuclear Information System (INIS)

    The purpose of this work is to understand and to identify the damaging mechanisms of Carbon-Carbon composite bonded to copper under thermomechanical loading. The study of the composite allowed the development of non-linear models. These ones have been introduced in the finite elements analysis code named CASTEM2000. They have been validated according to a correlation between simulation and mechanical tests on multi-material samples. These tests have also permitted us to better understand the behaviour of the bonding between composite and copper (damaging and fracture modes for different temperatures) under shear and tensile loadings. The damaging mechanisms of the bond under thermomechanical loading have been studied and identified according to microscopic observations on mock-ups which have sustained thermal cycling tests: some cracks appear in the composite, near the bond between the composite and the copper. The correlation between numerical and experimental results have been improved because of the reliability of the composite modelization, the use of residual stresses and the results of the bond mechanical characterization. (author)

  4. Study of the damaging mechanisms of a carbon - carbon composite bonded to copper under thermomechanical loading

    International Nuclear Information System (INIS)

    The purpose of this work is to understand and to identify the damaging mechanisms of Carbon-Carbon composite bonded to copper under thermomechanical loading. The study of the composite allowed the development of non-linear models. These ones have been introduced in the finite elements analysis code named CASTEM 2000. They have been validated according to a correlation between simulation and mechanical tests on multi-material samples. These tests have also permitted us to better understand the behaviour of the bonding between composite and copper (damaging and fracture modes for different temperatures) under shear and tensile loadings. The damaging mechanisms of the bond under thermomechanical loading have been studied and identified according to microscopic observations on mock-ups which have sustained thermal cycling tests: some cracks appear in the composite, near the bond between the composite and the copper. The correlation between numerical and experimental results have been improved because of the reliability of the composite modelization, the use of residual stresses and the results of the bond mechanical characterisation. (author)

  5. NUMERICAL SIMULATION STUDY ON ROCK BREAKING MECHANISM AND PROCESS UNDER HIGH PRESSURE WATER JET

    Institute of Scientific and Technical Information of China (English)

    NI Hong-jian; WANG Rui-he; ZHANG Yan-qing

    2005-01-01

    The numerical simulation method to study rock breaking process and mechanism under high pressure water jet was developed with the continuous mechanics and the FEM theory. The rock damage model and the damage-coupling model suited to analyze the whole process of water jet breaking rock were established with continuum damage mechanics and micro damage mechanics. The numerical results show the dynamic response of rock under water jet and the evolvement of hydrodynamic characteristic of jet during rock breaking is close to reality, and indicates that the body of rock damage and breakage under the general continual jet occurs within several milliseconds, the main damage form is tensile damage caused by rock unload and jet impact, and the evolvement of rock damage shows a step-change trend. On the whole,the numerical results can agree with experimental conclusions, which manifest that the analytical method is feasible and can be applied to guide the research and application of jet breaking rock theory.

  6. An analytical model of the mechanical properties of bulk coal under confined stress

    Science.gov (United States)

    Wang, G.X.; Wang, Z.T.; Rudolph, V.; Massarotto, P.; Finley, R.J.

    2007-01-01

    This paper presents the development of an analytical model which can be used to relate the structural parameters of coal to its mechanical properties such as elastic modulus and Poisson's ratio under a confined stress condition. This model is developed primarily to support process modeling of coalbed methane (CBM) or CO2-enhanced CBM (ECBM) recovery from coal seam. It applied an innovative approach by which stresses acting on and strains occurring in coal are successively combined in rectangular coordinates, leading to the aggregated mechanical constants. These mechanical properties represent important information for improving CBM/ECBM simulations and incorporating within these considerations of directional permeability. The model, consisting of constitutive equations which implement a mechanically consistent stress-strains correlation, can be used as a generalized tool to study the mechanical and fluid behaviors of coal composites. An example using the model to predict the stress-strain correlation of coal under triaxial confined stress by accounting for the elastic and brittle (non-elastic) deformations is discussed. The result shows a good agreement between the prediction and the experimental measurement. ?? 2007 Elsevier Ltd. All rights reserved.

  7. Mechanism of degradation of electrolyte solutions for dye-sensitized solar cells under ultraviolet light irradiation

    Science.gov (United States)

    Nakajima, Shohei; Katoh, Ryuzi

    2015-01-01

    We studied the mechanism of the degradation of I-/I3--containing electrolyte solutions for dye-sensitized solar cells under UV light irradiation. The yellow electrolyte solutions underwent achromatization during irradiation, indicating the reduction of I3-. We propose a mechanism involving the production of holes in TiO2, reaction of the holes with solvent molecules, and subsequent reduction of I3- by electrons remaining in the TiO2. Although the quantum yield of the photodegradation reaction is estimated to be low (3 × 10-3), this reaction can nevertheless be expected to affect the long-term stability of dye-sensitized solar cell devices.

  8. Mechanical failure of zigzag graphene nanoribbons under tensile strain induced by edge reconstruction

    KAUST Repository

    Cheng, Yingchun

    2012-10-01

    The structural and mechanical properties of graphene nanoribbons (GNRs) under uniaxial tensile strain are studied by density functional theory. The ideal strength of a zigzag GNR (120 GPa) is close to that of pristine graphene. However, for a GNR with both edges reconstructed to pentagon–heptagon pairs (from hexagon–hexagon pairs) it decreases to 94 GPa and the maximum tensile strain is reduced to 15%. Our results constitute a comprehensive picture of the edge structure effect on the mechanical properties of GNRs.

  9. Oxidative Stress and Mitochondrial Activation as the Main Mechanisms Underlying Graphene Toxicity against Human Cancer Cells

    Directory of Open Access Journals (Sweden)

    Anna Jarosz

    2016-01-01

    Full Text Available Due to the development of nanotechnology graphene and graphene-based nanomaterials have attracted the most attention owing to their unique physical, chemical, and mechanical properties. Graphene can be applied in many fields among which biomedical applications especially diagnostics, cancer therapy, and drug delivery have been arousing a lot of interest. Therefore it is essential to understand better the graphene-cell interactions, especially toxicity and underlying mechanisms for proper use and development. This review presents the recent knowledge concerning graphene cytotoxicity and influence on different cancer cell lines.

  10. Damage mechanism of single-layer reticulated domes under severe earthquakes

    Institute of Scientific and Technical Information of China (English)

    YU Xiao-ye; FAN Feng; ZHI Xu-dong; SHEN Shi-zhao

    2009-01-01

    To study the damage mechanism of single-layer reticulated domes subject to severe earthquakes,three limit states of single-layer reticulated domes under earthquakes are defined firstly in this paper. Then, two failure modes are presented by analyzing damage behaviors, and their characteristics are pointed out respectively. Furthermore, the damage process is analyzed and the causes of structural damage in different levels are studied. Finally, by comparing deformation and vibration status of domes with different failure modes, the principles of different failures are revealed and an integrated frame of damage mechanism is set up.

  11. Uncovering the underlying physical mechanisms of biological systems via quantification of landscape and flux

    Science.gov (United States)

    Li, Xu; Xiakun, Chu; Zhiqiang, Yan; Xiliang, Zheng; Kun, Zhang; Feng, Zhang; Han, Yan; Wei, Wu; Jin, Wang

    2016-01-01

    In this review, we explore the physical mechanisms of biological processes such as protein folding and recognition, ligand binding, and systems biology, including cell cycle, stem cell, cancer, evolution, ecology, and neural networks. Our approach is based on the landscape and flux theory for nonequilibrium dynamical systems. This theory provides a unifying principle and foundation for investigating the underlying mechanisms and physical quantification of biological systems. Project supported by the Natural Science Foundation of China (Grant Nos. 21190040, 11174105, 91225114, 91430217, and 11305176) and Jilin Province Youth Foundation, China (Grant No. 20150520082JH).

  12. Mechanistic modeling of thermal-mechanical deformation of CANDU pressure tube under localized high temperature condition

    International Nuclear Information System (INIS)

    Thermal strain deformation is a pressure tube failure mechanism. The main objective of this paper is to develop mechanistic models to evaluate local thermal-mechanical deformation of a pressure tube in CANDU reactor and to investigate fuel channel integrity under localized contact between fuel elements and pressure tube. The consequence of concern is potential creep strain failure of a pressure tube and calandria tube. The initial focus will be on the case where a fuel rod contacts the pressure tube at full power with highly cooling condition

  13. Potent Activities of Roemerine against Candida albicans and the Underlying Mechanisms.

    Science.gov (United States)

    Ma, Chaoyu; Du, Faya; Yan, Lan; He, Gonghao; He, Jianchang; Wang, Chengying; Rao, Gaoxiong; Jiang, Yuanying; Xu, Guili

    2015-01-01

    Roemerine (RM) is an aporphine alkaloid isolated from the fresh rattan stem of Fibraurea recisa, and it has been demonstrated to have certain antifungal activity. This study aimed to investigate the antifungal activity of RM and the underlying mechanisms in Candida albicans (C. albicans). The in vitro antifungal activity of RM was evaluated by a series of experiments, including the XTT reduction assay, confocal laser scanning microscopy assay, scanning electron microscope assay. Results showed that 1 μg/mL RM inhibited biofilm formation significantly (p anti-biofilm mechanism may be related to the cAMP pathway. PMID:26426004

  14. The mechanical strength of phosphates under friction-induced cross-linking

    Directory of Open Access Journals (Sweden)

    Z. Pawlak

    2006-04-01

    Full Text Available Purpose: In the present study, we consider mechanical properties of phosphate glasses under high temperature-induced and under friction-induced cross-linking, which enhance the modulus of elasticity.Design/methodology/approach: Two nanomechanical properties are evaluated, the first parameter is the modulus of elasticity (E (or Young’s modulus and the second parameter is the hardness (H. Zinc meta-, pyro - and orthophosphates were recognized as amorphous-colloidal nanoparticles were synthesized under laboratory conditions and showed antiwear properties in engine oil.Findings: Young’s modulus of the phosphate glasses formed under high temperature was in the 60-89 GPa range. For phosphate tribofilm formed under friction hardness and the Young’s modulus were in the range of 2-10 GPa and 40-215 GPa, respectively. The degree of cross-linking during friction is provided by internal pressure of about 600 MPa and temperature close to 1000°C enhancing mechanical properties by factor of 3 (see Fig 1.Research limitations/implications: The addition of iron or aluminum ions to phosphate glasses under high temperature - and friction-induced amorphization of zinc metaphosphate and pyrophosphate tends to provide more cross-linking and mechanically stronger structures. Iron and aluminum (FeO4 or AlO4 units, incorporated into phosphate structure as network formers, contribute to the anion network bonding by converting the P=O bonds into bridging oxygen. Future work should consider on development of new of materials prepared by sol-gel processes, eg., zinc (II-silicic acid.Originality/value: This paper analyses the friction pressure-induced and temperature–induced the two factors lead phosphate tribofilm glasses to chemically advanced glass structures, which may enhance the wear inhibition. Adding the coordinating ions alters the pressure at which cross-linking occurs and increases the antiwear properties of the surface material significantly

  15. Degradation mechanism of rock under impact loadings by integrated investigation on crack and damage development

    Institute of Scientific and Technical Information of China (English)

    周子龙; 江益辉; 邹洋; 翁磊

    2014-01-01

    Failure of rock under impact loadings involves complex micro-fracturing and progressive damage. Strength increase and splitting failure have been observed during dynamic tests of rock materials. However, the failure mechanism still remains unclear. In this work, based on laboratory tests, numerical simulations with the particle flow code (PFC) were carried out to reproduce the micro-fracturing process of granite specimens. Shear and tensile cracks were both recorded to investigate the failure mode of rocks under different loading conditions. At the same time, a dynamic damage model based on the Weibull distribution was established to predict the deformation and degradation behavior of specimens. It is found that micro-cracks play important roles in controlling the dynamic deformation and failure process of rock under impact loadings. The sharp increase in the number of cracks may be the reason for the strength increase of rock under high strain rates. Tensile cracks tend to be the key reason for splitting failure of specimens. Numerical simulation of crack propagation by PFC can give vivid description of the failure process. However, it is not enough for evaluation of material degradation. The dynamic damage model is able to predict the stress−strain relationship of specimens reasonably well, and can be used to explain the degradation of specimens under impact loadings at macro-scale. Crack and damage can describe material degradation at different scales and can be used together to reveal the failure mechanism of rocks.

  16. Fatal breakthrough infection with Fusarium andiyazi: new multi-resistant aetiological agent cross-reacting with Aspergillus galactomannan enzyme immunoassay.

    Science.gov (United States)

    Kebabcı, Nesrin; van Diepeningen, Anne D; Ener, Beyza; Ersal, Tuba; Meijer, Martin; Al-Hatmi, Abdullah M S; Ozkocaman, Vildan; Ursavaş, Ahmet; Cetinoğlu, Ezgi D; Akalın, Halis

    2014-04-01

    Disseminated infections caused by members of the Fusarium fujikuroi species complex (FFSC) occur regularly in immunocompromised patients. Here, we present the first human case caused by FFSC-member Fusarium andiyazi. Fever, respiratory symptoms and abnormal computerised tomography findings developed in a 65-year-old man with acute myelogenous leukaemia who was under posaconazole prophylaxis during his remission-induction chemotherapy. During the course of infection, two consecutive blood galactomannan values were found to be positive, and two blood cultures yielded strains resembling Fusarium species, according to morphological appearance. The aetiological agent proved to be F. andiyazi based on multilocus sequence typing. The sequencing of the internal transcribed spacer region did not resolve the closely related members of the FFSC, but additional data on partial sequence of transcription elongation factor 1 alpha subunit did. A detailed morphological study confirmed the identification of F. andiyazi, which had previously only been reported as a plant pathogen affecting various food crops.

  17. Mechanical Behavior of Tissue Simulants and Soft Tissues Under Extreme Loading Conditions

    Science.gov (United States)

    Kalcioglu, Zeynep Ilke

    Recent developments in computer-integrated surgery and in tissue-engineered constructs necessitate advances in experimental and analytical techniques in characterizing properties of mechanically compliant materials such as gels and soft tissues, particularly for small sample volumes. One goal of such developments is to quantitatively predict and mimic tissue deformation due to high rate impact events typical of industrial accidents and ballistic insults. This aim requires advances in mechanical characterization to establish tools and design principles for tissue simulant materials that can recapitulate the mechanical responses of hydrated soft tissues under dynamic contact-loading conditions. Given this motivation, this thesis studies the mechanical properties of compliant synthetic materials developed for tissue scaffold applications and of soft tissues, via modifying an established contact based technique for accurate, small scale characterization under fully hydrated conditions, and addresses some of the challenges in the implementation of this method. Two different engineered material systems composed of physically associating block copolymer gels, and chemically crosslinked networks including a solvent are presented as potential tissue simulants for ballistic applications, and compared directly to soft tissues from murine heart and liver. In addition to conventional quasistatic and dynamic bulk mechanical techniques that study macroscale elastic and viscoelastic properties, new methodologies are developed to study the small scale mechanical response of the aforementioned material systems to concentrated impact loading. The resistance to penetration and the energy dissipative constants are quantified in order to compare the deformation of soft tissues and mechanically optimized simulants, and to identify the underlying mechanisms by which the mechanical response of these tissue simulant candidates are modulated. Finally, given that soft tissues are biphasic in

  18. Reliability-based optimization of maintenance scheduling of mechanical components under fatigue

    Science.gov (United States)

    Beaurepaire, P.; Valdebenito, M.A.; Schuëller, G.I.; Jensen, H.A.

    2012-01-01

    This study presents the optimization of the maintenance scheduling of mechanical components under fatigue loading. The cracks of damaged structures may be detected during non-destructive inspection and subsequently repaired. Fatigue crack initiation and growth show inherent variability, and as well the outcome of inspection activities. The problem is addressed under the framework of reliability based optimization. The initiation and propagation of fatigue cracks are efficiently modeled using cohesive zone elements. The applicability of the method is demonstrated by a numerical example, which involves a plate with two holes subject to alternating stress. PMID:23564979

  19. CISM course on mechanical behaviour of soils under environmentally induced cyclic loads

    CERN Document Server

    Wood, David; Mechanical Behaviour of Soils Under Environmentally Induced Cyclic Loads

    2012-01-01

    The book gives a comprehensive description of the mechanical response of soils (granular and cohesive materials) under cyclic loading. It provides the geotechnical engineer with the theoretical and analytical tools necessary for the evaluation of settlements developng with time under cyclic, einvironmentally idncued loads (such as wave motion, wind actions, water table level variation) and their consequences for the serviceability and durability of structures such as the shallow or deep foundations used in offshore engineering, caisson beakwaters, ballast and airport pavements and also to interpret monitoring data, obtained from both natural and artificial slopes and earth embankments, for the purposes of risk assessment and mitigation.

  20. Risk factors for metachronous contralateral breast cancer suggest two aetiological pathways.

    Science.gov (United States)

    Vichapat, Voralak; Gillett, Cheryl; Fentiman, Ian S; Tutt, Andrew; Holmberg, Lars; Lüchtenborg, Margreet

    2011-09-01

    Although many studies show an increased risk of metachronous contralateral breast cancer (CBC) in women with a positive family history and young age at diagnosis of the initial breast cancer, the aetiological pathways are still enigmatic. In a cohort of 8478 primary breast cancer patients diagnosed between 1975 and 2006, 558 cases of metachronous CBC were identified. Using multivariate Cox proportional hazards models, we analysed risk factors assessed at the time of the first primary tumour, including patient demographics, tumour characteristics and treatment among 4681 breast cancer patients for whom data on key variables were available. The analysis was performed separately in patients who developed CBC without and with prior recurrence(s). Risk of CBC without prior recurrent disease was increased by a positive family history [adjusted relative risk (RR) 2.8 (95% confidence interval (CI) 1.4-5.5)]; and decreased by endocrine treatment [RR 0.6 (95% CI 0.4-1.0)]. We found an increased risk of CBC with prior recurrent disease with younger age [RR 1.2 (95% CI 1.4-3.0)]; positive family history [RR 2.1 (95%CI 0.8-5.0)]; and extensive lymph node involvement [RR 2.0 (95% CI 1.2-3.6)]. Our results suggest that nodal status of the primary tumour may be as important a risk factor as family history or age, which indicates a high susceptibility to breast cancer or an impaired host defence mechanism. It may also imply that some CBCs are metastases from the first primary tumour, particularly in patients who present with recurrent disease before CBC. PMID:21658939

  1. Dynamic Mechanical Behavior and Numerical Simulation of Frozen Soil under Impact Loading

    Directory of Open Access Journals (Sweden)

    Dan Zhang

    2016-01-01

    Full Text Available Split Hopkinson pressure bars (SHBP were used to perform impact experiments on frozen soil under various impact velocities and temperatures to analyze the effect of these parameters on the mechanical behavior of the soil. Based on the Holmquist-Johnson-Cook constitutive model, the dynamic mechanical properties under impact loading were analyzed. The SHPB experiments of frozen soil were also simulated using the finite element analysis software LS-DYNA, and the simulation results were similar to the experimental results. The temperature effect, strain rate effect, and the destruction process of the frozen soil as well as the propagation process of stress waves in the incident bar, transmission bar, and frozen soil specimen were investigated. This work provides a good theoretical basis and technical support for frozen soil engineering applications.

  2. Mechanism analysis on pillar instability induced by micro-disturbance under critical condition

    Institute of Scientific and Technical Information of China (English)

    LI Jiang-teng; CAO Ping

    2005-01-01

    A simplified mechanical model of ultra-high pillar was established and its potential energy expression was derived under axial load on the basis of energy theory. Under critical conditions according to the nonlinear theory,the critical behaviors and the forming mechanism of pillar instability were discussed by external disturbance , such as stresses waves by blasting , axial force eccentricity ratherish and imperfections in pillar. The results show that the micro-disturbances attenuate with time and they are independence each other when pillar is in the stability state.Their effects on the stability of system are inessential. The correlation degree of disturbances increases sharply and various micro-disturbances are relative and nested reciprocally when the system is in critical state and they also cooperate with each other, which induces system to reach a new state.

  3. Size and Geometry Effects on the Mechanical Properties of Carrara Marble Under Dynamic Loadings

    Science.gov (United States)

    Zou, Chunjiang; Wong, Louis Ngai Yuen

    2016-05-01

    The effects of specimen size and geometry on the dynamic mechanical properties of Carrara marble including compressive strength, failure strain and elastic modulus are investigated in this research. Four different groups of specimens of different sizes and cross-sectional geometries are loaded under a wide range of strain rates by the split Hopkinson pressure bar setup. The experimental results indicate that all these mechanical properties are significantly influenced by the specimen size and geometry to different extent, hence highlighting the importance of taking into account of the specimen size and geometry in dynamic tests on rock materials. In addition, the transmission coefficient and the determination of strain rate under dynamic tests are discussed in detail.

  4. Damage evolution of TBC system under in-phase thermo-mechanical tests

    Energy Technology Data Exchange (ETDEWEB)

    Kitazawa, R.; Tanaka, M.; Kagawa, Y. [Research Center for Advanced Science and Technology, University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8904 (Japan); Liu, Y.F., E-mail: yfliu@hyper.rcast.u-tokyo.ac.jp [Research Center for Advanced Science and Technology, University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8904 (Japan)

    2010-10-15

    In-phase thermo-mechanical tests (TMF) of EB-PVD Y{sub 2}O{sub 3}-ZrO{sub 2} thermal barrier coating (TBC) system (8 wt% Y{sub 2}O{sub 3}-ZrO{sub 2}/CoNiCrAlY/IN-738 substrate) were done under a through-the-thick-direction thermal gradient from TBC surface temperature at 1150 deg. C to substrate temperature at 1000 deg. C. Deformation and failure behaviors of the TBC system were observed at the macroscopic and microscopic scales and damage evolution of the system under in-phase thermo-mechanical test was discussed. Special attention was paid to TBC layer cracking, thermally grown oxide (TGO) layer formation and void formation in bond coat and substrate. Effect of TMF conditions on the damage evolution behaviors was also discussed.

  5. Music and Memory in Alzheimer's Disease and The Potential Underlying Mechanisms.

    Science.gov (United States)

    Peck, Katlyn J; Girard, Todd A; Russo, Frank A; Fiocco, Alexandra J

    2016-01-01

    With population aging and a projected exponential expansion of persons diagnosed with Alzheimer's disease (AD), the development of treatment and prevention programs has become a fervent area of research and discovery. A growing body of evidence suggests that music exposure can enhance memory and emotional function in persons with AD. However, there is a paucity of research that aims to identify specific underlying neural mechanisms associated with music's beneficial effects in this particular population. As such, this paper reviews existing anecdotal and empirical evidence related to the enhancing effects of music exposure on cognitive function and further provides a discussion on the potential underlying mechanisms that may explain music's beneficial effect. Specifically, this paper will outline the potential role of the dopaminergic system, the autonomic nervous system, and the default network in explaining how music may enhance memory function in persons with AD. PMID:26967216

  6. First-principles calculations of structural stability and mechanical properties of tungsten carbide under high pressure

    Science.gov (United States)

    Li, Xinting; Zhang, Xinyu; Qin, Jiaqian; Zhang, Suhong; Ning, Jinliang; Jing, Ran; Ma, Mingzhen; Liu, Riping

    2014-11-01

    The structural stability and mechanical properties of WC in WC-, MoC- and NaCl-type structures under high pressure are investigated systematically by first-principles calculations. The calculated equilibrium lattice constants at zero pressure agree well with available experimental and theoretical results. The formation enthalpy indicates that the most stable WC is in WC-type, then MoC-type finally NaCl-type. By the elastic stability criteria, it is predicted that the three structures are all mechanically stable. The elastic constants Cij, bulk modulus B, shear modulus G, Young's modulus E and Poisson's ratio ν of the three structures are studied in the pressure range from 0 to 100 GPa. Furthermore, by analyzing the B/G ratio, the brittle/ductile behavior under high pressure is assessed. Moreover, the elastic anisotropy of the three structures up to 100 GPa is also discussed in detail.

  7. Electroluminescence and cathodoluminescence from polyethylene and polypropylene films: Spectra reconstruction from elementary components and underlying mechanisms

    Energy Technology Data Exchange (ETDEWEB)

    Qiao, B. [Université de Toulouse, UPS, INP, LAPLACE (Laboratoire Plasma et Conversion d' Energie), 118 route de Narbonne, F-31062 Toulouse (France); Teyssedre, G.; Laurent, C. [Université de Toulouse, UPS, INP, LAPLACE (Laboratoire Plasma et Conversion d' Energie), 118 route de Narbonne, F-31062 Toulouse (France); CNRS, LAPLACE, F-31062 Toulouse (France)

    2016-01-14

    The mechanisms of electroluminescence from large band gap polymers used as insulation in electric components are still under debate. It becomes important to unravel the underlying physics of the emission because of increasing thermo-electric stress and a possible relationship between electroluminescence and field withstand. We report herein on the cathodoluminescence spectra of polyethylene and polypropylene films as a way to uncover the nature of its contributions to electroluminescence emission. It is shown that spectra from the two materials are structured around four elementary components, each of them being associated with a specific process contributing to the overall emission with different weights depending on excitation conditions and on materials. The cathodoluminescence and electroluminescence spectra of each material are reconstructed from the four spectral components and their relative contribution are discussed. It is shown that electroluminescence from polyethylene and polypropylene has the same origin pointing towards generic mechanisms in both.

  8. Electroluminescence and cathodoluminescence from polyethylene and polypropylene films: Spectra reconstruction from elementary components and underlying mechanisms

    Science.gov (United States)

    Qiao, B.; Teyssedre, G.; Laurent, C.

    2016-01-01

    The mechanisms of electroluminescence from large band gap polymers used as insulation in electric components are still under debate. It becomes important to unravel the underlying physics of the emission because of increasing thermo-electric stress and a possible relationship between electroluminescence and field withstand. We report herein on the cathodoluminescence spectra of polyethylene and polypropylene films as a way to uncover the nature of its contributions to electroluminescence emission. It is shown that spectra from the two materials are structured around four elementary components, each of them being associated with a specific process contributing to the overall emission with different weights depending on excitation conditions and on materials. The cathodoluminescence and electroluminescence spectra of each material are reconstructed from the four spectral components and their relative contribution are discussed. It is shown that electroluminescence from polyethylene and polypropylene has the same origin pointing towards generic mechanisms in both.

  9. A Review on Solidification and Change in Mechanical Properties Under Vibratory Welding Condition

    Directory of Open Access Journals (Sweden)

    Jyoti Prakash

    2010-04-01

    Full Text Available Welding has been applied to various industries in particular, automotive, aerospace and microelectronics. Thermal cycle produced near weld line generates residual stress and inhomogeneous plastic deformation in weldments. However there are many methods for welding the workpieces and one of the method among these is vibratory welding. It has the advantages of less investment, more convenient operation, less pollution and shorter manufacturing period. In vibratory welding, workpiece vibrates in the whole welding process and it mainly effects the welding solidification to improve the quality. Vibration facilitates the release of dissolved gases and the resulting weld beads greatly exhibit reduced porosity. Mechanical properties of the welds prepared under vibratory conditions are dependent on the structural changes of the welds This paper presents the solidification behaviour and changes occurs in mechanical properties under vibratory welding condition.

  10. Behavioral Effects of Upper Respiratory Tract Illnesses: A Consideration of Possible Underlying Cognitive Mechanisms

    Directory of Open Access Journals (Sweden)

    Andrew P. Smith

    2012-03-01

    Full Text Available Previous research has shown that both experimentally induced upper respiratory tract illnesses (URTIs and naturally occurring URTIs influence mood and performance. The present study investigated possible cognitive mechanisms underlying the URTI-performance changes. Those who developed a cold (N = 47 had significantly faster, but less accurate, performance than those who remained healthy (N = 54. Illness had no effect on manipulations designed to influence encoding, response organisation (stimulus-response compatilibility or response preparation. Similarly, there was no evidence that different components of working memory were impaired. Overall, the present research confirms that URTIs can have an effect on performance efficiency. Further research is required to identify the physiological and behavioral mechanisms underlying these effects.

  11. From Sound to Significance: Exploring the Mechanisms Underlying Emotional Reactions to Music.

    Science.gov (United States)

    Juslin, Patrik N; Barradas, Gonçalo; Eerola, Tuomas

    2015-01-01

    A common approach to studying emotional reactions to music is to attempt to obtain direct links between musical surface features such as tempo and a listener's responses. However, such an analysis ultimately fails to explain why emotions are aroused in the listener. In this article we explore an alternative approach, which aims to account for musical emotions in terms of a set of psychological mechanisms that are activated by different types of information in a musical event. This approach was tested in 4 experiments that manipulated 4 mechanisms (brain stem reflex, contagion, episodic memory, musical expectancy) by selecting existing musical pieces that featured information relevant for each mechanism. The excerpts were played to 60 listeners, who were asked to rate their felt emotions on 15 scales. Skin conductance levels and facial expressions were measured, and listeners reported subjective impressions of relevance to specific mechanisms. Results indicated that the target mechanism conditions evoked emotions largely as predicted by a multimechanism framework and that mostly similar effects occurred across the experiments that included different pieces of music. We conclude that a satisfactory account of musical emotions requires consideration of how musical features and responses are mediated by a range of underlying mechanisms. PMID:26442337

  12. Contact force and mechanical loss of multistage cable under tension and bending

    Science.gov (United States)

    Ru, Yanyun; Yong, Huadong; Zhou, Youhe

    2016-07-01

    A theoretical model for calculating the stress and strain states of cabling structures with different loadings has been developed in this paper. We solve the problem for the first- and second-stage cable with tensile or bending strain. The contact and friction forces between the strands are presented by two-dimensional contact model. Several theoretical models have been proposed to verify the results when the triplet subjected to the tensile strain, including contact force, contact stresses, and mechanical loss. It is found that loadings will affect the friction force and the mechanical loss of the triplet. The results show that the contact force and mechanical loss are dependent on the twist pitch. A shorter twist pitch can lead to higher contact force, while the trend of mechanical loss with twist pitch is complicated. The mechanical loss may be reduced by adjusting the twist pitch reasonably. The present model provides a simple analysis method to investigate the mechanical behaviors in multistage-structures under different loads.

  13. The chemical and mechanical behaviors of polymer / reactive metal systems under high strain rates

    Science.gov (United States)

    Shen, Yubin

    As one category of energetic materials, impact-initiated reactive materials are able to release a high amount of stored chemical energy under high strain rate impact loading, and are used extensively in civil and military applications. In general, polymers are introduced as binder materials to trap the reactive metal powders inside, and also act as an oxidizing agent for the metal ingredient. Since critical attention has been paid on the metal / metal reaction, only a few types of polymer / reactive metal interactions have been studied in the literature. With the higher requirement of materials resistant to different thermal and mechanical environments, the understanding and characterization of polymer / reactive metal interactions are in great demand. In this study, PTFE (Polytetrafluoroethylene) 7A / Ti (Titanium) composites were studied under high strain rates by utilizing the Taylor impact and SHPB tests. Taylor impact tests with different impact velocities, sample dimensions and sample configurations were conducted on the composite, equipped with a high-speed camera for tracking transient images during the sudden process. SHPB and Instron tests were carried out to obtain the stress vs. strain curves of the composite under a wide range of strain rates, the result of which were also utilized for fitting the constitutive relations of the composite based on the modified Johnson-Cook strength model. Thermal analyses by DTA tests under different flow rates accompanied with XRD identification were conducted to study the reaction mechanism between PTFE 7A and Ti when only heat was provided. Numerical simulations on Taylor impact tests and microstructural deformations were also performed to validate the constitutive model built for the composite system, and to investigate the possible reaction mechanism between two components. The results obtained from the high strain rate tests, thermal analyses and numerical simulations were combined to provide a systematic study on

  14. Mechanical Behavior of BFRP-Steel Composite Plate under Axial Tension

    OpenAIRE

    Yunyu Li; Yanlei Wang; Jinping Ou

    2014-01-01

    Combining the advantages of basalt fiber-reinforced polymer (BFRP) material and steel material, a novel BFRP-steel composite plate (BSP) is proposed, where a steel plate is sandwiched between two outer BFRP laminates. The main purpose of this research is to investigate the mechanical behavior of the proposed BSP under uniaxial tension and cyclic tension. Four groups of BSP specimens with four different BFRP layers and one control group of steel plate specimens were prepared. A uniaxial tensil...

  15. Genetic mechanisms underlying apimaysin and maysin synthesis and corn earworm antibiosis in maize (Zea mays L.).

    OpenAIRE

    Lee, E A; Byrne, P.F.; McMullen, M D; Snook, M E; Wiseman, B. R.; Widstrom, N W; Coe, E. H.

    1998-01-01

    C-glycosyl flavones in maize silks confer resistance (i.e., antibiosis) to corn earworm (Helicoverpa zea [Boddie]) larvae and are distinguished by their B-ring substitutions, with maysin and apimaysin being the di- and monohydroxy B-ring forms, respectively. Herein, we examine the genetic mechanisms underlying the synthesis of maysin and apimaysin and the corresponding effects on corn earworm larval growth. Using an F2 population, we found a quantitative trait locus (QTL), rem1, which account...

  16. Mechanical property evaluation of apricot fruits under quasi-static and dynamic loading

    OpenAIRE

    Ahmadi, E.; H Barikloo

    2016-01-01

    Introduction: Some forces and impacts that occur during transporting and handling can reduce the apricot quality. Bruise damage is a major cause of fruit quality loss. Bruises occur under dynamic and static loading when stress induced in the fruit exceeds the failure stress of the fruit tissue. Needless to say that physical and mechanical properties of fruits in the design and optimization of systems related to production, processing and packaging of the products are important. Harvesting, tr...

  17. Mechanisms underlying reductant-induced reactive oxygen species formation by anticancer copper(II) compounds

    OpenAIRE

    Kowol, Christian R.; Heffeter, Petra; Miklos, Walter; Gille, Lars; Trondl, Robert; Cappellacci, Loredana; Berger, Walter; Keppler, Bernhard K.

    2011-01-01

    Intracellular generation of reactive oxygen species (ROS) via thiol-mediated reduction of copper(II) to copper(I) has been assumed as the major mechanism underlying the anticancer activity of copper(II) complexes. The aim of this study was to compare the anticancer potential of copper(II) complexes of Triapine (3-amino-pyridine-2-carboxaldehyde thiosemicarbazone; currently in phase II clinical trials) and its terminally dimethylated derivative with that of 2-formylpyridine thiosemicarbazone a...

  18. Contribution to the study of the dynamic behavior of mechanical transmissions under non-stationary conditions

    OpenAIRE

    Hammami, Ahmed

    2015-01-01

    ABSTRACT: Research developments devoted todynamic behavior characterization of mechanical transmissions is always an interesting topic since there is a continuous need to decrease vibration and noise while keeping high compactness and efficiency. Most studies were focused on transmissions running under stationary condition where speed and load are assumed constant. However, repetitive run ups, time varying loading and speed conditions are very common in many industrial applications which impl...

  19. Identifying serotonergic mechanisms underlying the corticolimbic response to threat in humans

    DEFF Research Database (Denmark)

    Fisher, Patrick M; Hariri, Ahmad R

    2013-01-01

    A corticolimbic circuit including the amygdala and medial prefrontal cortex (mPFC) plays an important role in regulating sensitivity to threat, which is heightened in mood and anxiety disorders. Serotonin is a potent neuromodulator of this circuit; however, specific serotonergic mechanisms......-dependent functional magnetic resonance imaging. This multi-modal neuroimaging strategy can be integrated with additional techniques including imaging genetics and pharmacological challenge paradigms to more clearly understand how serotonin signalling modulates neural pathways underlying sensitivity to threat...

  20. Degradation Of H.V. Generator Insulation Under Mechanical, Electrical And Thermal Stresses

    OpenAIRE

    Ramu, TS

    1990-01-01

    The paper presents the results of ageing experiments under combined electrical, mechanical (vibration) and thermal stresses on epoxy bonded mica insulation. Actual 11 KV machine coils designed for use in 1 MW rotating machines are used as the specimens. Both diagnostic and destructive tests were carried out to assess the amount of ageing. It was observed that the incremental loss tangent and partial discharge energy per cycle increase monotonically with time of ageing and that the dielectric...

  1. The statistical mechanics of a polygenic character under stabilizing selection, mutation and drift

    OpenAIRE

    de Vladar, H. P.; Barton, N. H.

    2011-01-01

    By exploiting an analogy between population genetics and statistical mechanics, we study the evolution of a polygenic trait under stabilizing selection, mutation and genetic drift. This requires us to track only four macroscopic variables, instead of the distribution of all the allele frequencies that influence the trait. These macroscopic variables are the expectations of: the trait mean and its square, the genetic variance, and of a measure of heterozygosity, and are derived from a generati...

  2. COSTS OF GREENHOUSE GAS EMISSIONS ABATEMENT UNDER THE CLEAN DEVELOPMENT MECHANISM

    OpenAIRE

    Rahman, Shaikh M.; Larson, Donald F.; ARIEL DINAR

    2015-01-01

    This paper examines the costs of emissions abatement through various types of projects financed under the Clean Development Mechanism (CDM) of the Kyoto Protocol. Using project data, cost functions are estimated applying alternative functional forms. Results show that the average cost of abatement decreases with the volume of abatement, showing economies of scale and suggesting that reducing emissions through small projects is relatively expensive. Results also show significant variation in t...

  3. Neural mechanisms underlying the integration of situational information into attribution outcomes

    OpenAIRE

    Brosch, Tobias; Schiller, Daniela; Mojdehbakhsh, Rachel; Uleman, James S.; Phelps, Elizabeth A.

    2013-01-01

    When forming impressions and trying to figure out why other people behave the way they do, we should take into account not only dispositional factors (i.e. personality traits) but also situational constraints as potential causes for a behavior. However, in their attributions, people often ignore the importance of situational factors. To investigate the neural mechanisms underlying the integration of situational information into attributions, we decomposed the attribution process by separately...

  4. Mechanisms underlying the effects of inulin-type fructans on the intestinal calcium absorption

    OpenAIRE

    Raschka, Ladislav

    2005-01-01

    Inulin-type fructans in a diet are selectively fermented by the large intestinal microflora which causes a multitude of effects that are considered as beneficial for human health and well-being. One of these well documented actions is an increased intestinal calcium absorption, similarly observed in experimental animals and in humans. Since the underlying mechanisms are not yet understood, various in vivo and in vitro experiments with rats were conducted to elucidate the molecular actions of ...

  5. Mechanical Properties of Brittle Materials and Their Single Fracture under Dynamic Loading

    OpenAIRE

    YASHIMA, Saburo; Kanda, Yoshiteru; Saito, Fumio; Sasaki, Toru; Iijima, Masayoshi; HASHIMOTO, Hitoshi

    1983-01-01

    The meaning of study on single particle crushing is recognized at which it is regarded the accumulation of single particle crushing as the comminution performed in practical operations stochastic phenomena. Especially, experimental data concerning the mechanical properties of brittle solids measured under dynamic loading are so far very few. Further, the experimental data concerning compressive strength, sphere compressive strength, fracture energy, new surface produced and fracture surface e...

  6. Optimal Contract Design for Cooperative Relay Incentive Mechanism under Moral Hazard

    OpenAIRE

    Nan Zhao; Minghu Wu; Wei Xiong; Cong Liu

    2015-01-01

    Cooperative relay can effectively improve spectrum efficiency by exploiting the spatial diversity in the wireless networks. However, wireless nodes may acquire different network information with various users’ location and mobility, channels’ conditions, and other factors, which results in asymmetric information between the source and the relay nodes (RNs). In this paper, the relay incentive mechanism between relay nodes and the source is investigated under the asymmetric information. By mode...

  7. THE EQUIVALENT MECHANICAL MODELS OF LIQUID SLOSHING IN A SPHERICAL TANK WITH SPACER UNDER LOW GRAVITY

    Institute of Scientific and Technical Information of China (English)

    CHENG Xu-duo; HU Mei-zhu; WEN Ji-hua

    2005-01-01

    The dynamics of liquid sloshing in a spherical tank with spacer under low gravity was investigated. By extending the characteristic functions, the frequencies of liquid free-sloshing, reaction force and moments on the wall of tank were obtained. By mechanical equivalent principle, the equivalent models of spring-vibrator-damper of liquid sloshing were given. The numerical results obtained show when a spacer is inserted in the tank, the sloshing frequency of liquid and the sloshing mass of liquid will decrease.

  8. Diesel exhaust: current knowledge of adverse effects and underlying cellular mechanisms

    OpenAIRE

    Steiner, Sandro; Bisig, Christoph; Petri-Fink, Alke; Rothen-Rutishauser, Barbara

    2016-01-01

    Diesel engine emissions are among the most prevalent anthropogenic pollutants worldwide, and with the growing popularity of diesel-fueled engines in the private transportation sector, they are becoming increasingly widespread in densely populated urban regions. However, a large number of toxicological studies clearly show that diesel engine emissions profoundly affect human health. Thus the interest in the molecular and cellular mechanisms underlying these effects is large, especially c...

  9. A fracture mechanics study of tungsten failure under high heat flux loads

    International Nuclear Information System (INIS)

    The performance of fusion devices is highly dependent on plasma-facing components. Tungsten is the most promising candidate material for armors in plasma-facing components in ITER and DEMO. However, the brittleness of tungsten below the ductile-to-brittle transition temperature is very critical to the reliability of plasma-facing components. In this work, thermo-mechanical and fracture behaviors of tungsten are predicted numerically under fusion relevant thermal loadings.

  10. Transcriptional and epigenetic mechanisms underlying enhanced in vitro adipocyte differentiation by the brominated flame retardant BDE-47

    DEFF Research Database (Denmark)

    Kamstra, Jorke H; Hruba, Eva; Blumberg, Bruce;

    2014-01-01

    . The mechanisms by which EDCs direct preadipocytes to form adipocytes are poorly understood. Here, we examined transcriptional and epigenetic mechanisms underlying the induction of in vitro adipocyte differentiation by BDE-47. Quantitative high content microscopy revealed concentration-dependent enhanced...

  11. Behaviour of radiation defects under the influence of mechanical strain in ion-implanted silicon

    Science.gov (United States)

    Suprun-Belevich, Yu.; Palmetshofer, L.

    1997-05-01

    The interactions between radiation defects and internal mechanical strain in ion-implanted semiconductor crystals have been investigated by means of Hall-effect measurements, deep-level transient spectroscopy (DLTS) and X-ray diffraction. The mechanical strain had been intentionally introduced into silicon crystals by 320 keV Ge-ion implantation (10 15-3 × 10 16 cm -2) and subsequent annealing. The samples were then subjected to H + - or Si +-ion bombardment for the introduction of radiation defects. Both Hall-effect and DLTS measurements showed a decrease of the defect production rate in a wide dose interval and accelerated annealing of the radiation defects in strained samples compared to unstrained reference samples. The reduction of the defect concentration during implantation and annealing under the influence of strain is supposed to be connected with an energy transfer from the elastic mechanical strain field to the defects.

  12. FInal Report: First Principles Modeling of Mechanisms Underlying Scintillator Non-Proportionality

    Energy Technology Data Exchange (ETDEWEB)

    Aberg, Daniel [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Sadigh, Babak [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Zhou, Fei [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

    2015-01-01

    This final report presents work carried out on the project “First Principles Modeling of Mechanisms Underlying Scintillator Non-Proportionality” at Lawrence Livermore National Laboratory during 2013-2015. The scope of the work was to further the physical understanding of the microscopic mechanisms behind scintillator nonproportionality that effectively limits the achievable detector resolution. Thereby, crucial quantitative data for these processes as input to large-scale simulation codes has been provided. In particular, this project was divided into three tasks: (i) Quantum mechanical rates of non-radiative quenching, (ii) The thermodynamics of point defects and dopants, and (iii) Formation and migration of self-trapped polarons. In the following, the progress and results of each of these subtasks will be detailed.

  13. Experimental research on buckling of thin films in nano-scale under mechanical and thermal loading

    Science.gov (United States)

    Wang, S. B.; Jia, H. K.; Ren, X. C.; Li, L. A.

    2008-11-01

    In this paper, the mechanical and thermal properties of compressed thin film titanium films with 150nm thickness deposited on an organic glass substrate under mechanical and thermal loads were measured and characterized. In order to simulate the thin films in IT which subjected compound loads and to produce the buckle modes, the external uniaxial compression and thermal loading are subjected to the specimen by the symmetric loading device and the electrical resistance film in this experiment. The temperature of the thin film deposited on substrate was measured using thermoelectric couple. The range of temperature accords with the temperature range of the MEMS. It is found that the size and number of the delamination and buckling of the film are depended upon the pre-fixed mechanical loading. The transient conduction and thermal stability of the film and substrate was studied with finite element method.

  14. FInal Report: First Principles Modeling of Mechanisms Underlying Scintillator Non-Proportionality

    Energy Technology Data Exchange (ETDEWEB)

    Aberg, Daniel [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Sadigh, Babak [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Zhou, Fei [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

    2015-01-01

    This final report presents work carried out on the project “First Principles Modeling of Mechanisms Underlying Scintillator Non-Proportionality” at Lawrence Livermore National Laboratory during 2013-2015. The scope of the work was to further the physical understanding of the microscopic mechanisms behind scintillator nonproportionality that effectively limits the achievable detector resolution. Thereby, crucial quantitative data for these processes as input to large-scale simulation codes has been provided. In particular, this project was divided into three tasks: (i) Quantum mechanical rates of non-radiative quenching, (ii) The thermodynamics of point defects and dopants, and (iii) Formation and migration of self-trapped polarons. The progress and results of each of these subtasks are detailed.

  15. Experimental Study on the Thermal Damage Characteristics of Limestone and Underlying Mechanism

    Science.gov (United States)

    Zhang, Weiqiang; Sun, Qiang; Hao, Shuqing; Wang, Bo

    2016-08-01

    This work discusses an experimental investigation on the thermal damage characteristics of limestone and underlying mechanism. Cylindrical rock samples were heated to a specific temperature level of 25, 100, 200, 300, 400, 500, 600, 700, 800, and 900 °C. Then the thermal damage evolution equation was established based on the experimental results and the characteristics of thermal damage were analyzed. Last, possible mechanisms for the observed thermo-physical and mechanical response are discussed. The results show that with the increase of temperature in the tested range of temperature, the P-wave velocity, peak compressive strength and elastic modulus decrease, but the peak strain increases; the damage factors increase faster in 200-600 °C; the development of high-temperature-induced cracks conforms to the dislocation theory; the decomposition of magnesium carbonate and dolomite is the main reaction in the tested temperature range.

  16. Scaling laws and deformation mechanisms of nanoporous copper under adiabatic uniaxial strain compression

    Directory of Open Access Journals (Sweden)

    Fuping Yuan

    2014-12-01

    Full Text Available A series of large-scale molecular dynamics simulations were conducted to investigate the scaling laws and the related atomistic deformation mechanisms of Cu monocrystal samples containing randomly placed nanovoids under adiabatic uniaxial strain compression. At onset of yielding, plastic deformation is accommodated by dislocations emitted from void surfaces as shear loops. The collapse of voids are observed by continuous emissions of dislocations from void surfaces and their interactions with further plastic deformation. The simulation results also suggest that the effect modulus, the yield stress and the energy aborption density of samples under uniaxial strain are linearly proportional to the relative density ρ. Moreover, the yield stress, the average flow stress and the energy aborption density of samples with the same relative density show a strong dependence on the void diameter d, expressed by exponential relations with decay coefficients much higher than -1/2. The corresponding atomistic mechanisms for scaling laws of the relative density and the void diameter were also presented. The present results should provide insights for understanding deformation mechanisms of nanoporous metals under extreme conditions.

  17. Investigation of mechanical properties of twin gold crystal nanowires under uniaxial load by molecular dynamics method

    Science.gov (United States)

    Zhang, Guo-Wei; Yang, Zai-Lin; Luo, Gang

    2016-08-01

    Twin gold crystal nanowires, whose loading direction is parallel to the twin boundary orientation, are simulated. We calculate the nanowires under tensile or compressive loads, different length nanowires, and different twin boundary nanowires respectively. The Young modulus of nanowires under compressive load is about twice that under tensile load. The compressive properties of twin gold nanowires are superior to their tensile properties. For different length nanowires, there is a critical value of length with respect to the mechanical properties. When the length of nanowire is greater than the critical value, its mechanical properties are sensitive to length. The twin boundary spacing hardly affects the mechanical properties. Project supported by the National Science and Technology Pillar Program, China (Grant No. 2015BAK17B06), the Earthquake Industry Special Science Research Foundation Project, China (Grant No. 201508026-02), the Natural Science Foundation of Heilongjiang Province, China (Grant No. A201310), and the Scientific Research Starting Foundation for Post Doctorate of Heilongjiang Province, China (Grant No. LBHQ13040).

  18. Design options for cooperation mechanisms under the new European renewable energy directive

    International Nuclear Information System (INIS)

    In June 2009, a new EU directive on the promotion of renewable energy sources (RES) entered into effect. The directive 2009/28/EC, provides for three cooperation mechanisms that will allow member states to achieve their national RES target in cooperation with other member states: statistical transfer, joint projects, and joint support schemes. This article analyses the pros and cons of the three mechanisms and explores design options for their implementation through strategic and economic questions: How to counterbalance the major drawbacks of each mechanism? How to reflect a balance of costs and benefits between the involved member states? The analysis identifies a number of design options that respond to these questions, e.g. long term contracts to ensure sufficient flexibility for statistical transfers, a coordinated, standardised joint project approach to increase transparency in the European market, and a stepwise harmonisation of joint support schemes that is based on a cost-effective accounting approach. One conclusion is that the three cooperation mechanisms are closely interlinked. One can consider their relation to be a gradual transition from member state cooperation under fully closed national support systems in case of statistical transfers, to cooperation under fully open national support systems in a joint support scheme.

  19. Wear mechanism for spray deposited Al-Si/SiCp composites under dry sliding condition

    Institute of Scientific and Technical Information of China (English)

    滕杰; 李华培; 陈刚

    2015-01-01

    Al-Si/15%SiCp (volume fraction) composites with different silicon contents were fabricated by spray deposition technique, and typical microstructures of these composites were studied by optical microscopy (OM). Dry sliding wear tests were carried out using a block-on-ring wear machine to investigate the effect of applied load range of 10−220 N on the wear and friction behavior of these composites sliding against SAE 52100 grade bearing steel. Scanning electron microscopy (SEM) and energy-dispersive X-ray microanalysis (EDAX) were utilized to examine the morphologies of the worn surfaces in order to observe the wear characteristics and investigate the wear mechanism. The results show that the wear behavior of these composites is dependent on the silicon content in the matrix alloy and the applied load. Al-Si/15%SiCp composites with higher silicon content exhibit better wear resistance in the applied load range. Under lower loads, the major wear mechanisms are oxidation wear and abrasive wear for all tested composites. Under higher loads, severe adhesive wear becomes the main wear mechanisms for Al-7Si/15%SiCp and Al-13Si/15%SiCp composites, while Al-20Si/15%SiCp presents a compound wear mechanism, consisting of oxidation, abrasive wear and adhesion wear.

  20. A mathematical model of cortical bone remodeling at cellular level under mechanical stimulus

    Institute of Scientific and Technical Information of China (English)

    Qing-Hua Qin; Ya-Nan Wang

    2012-01-01

    A bone cell population dynamics model for cortical bone remodeling under mechanical stimulus is developed in this paper.The external experiments extracted from the literature which have not been used in the creation of the model are used to test the validity of the model.Not only can the model compare reasonably well with these experimental results such as the increase percentage of final values of bone mineral content (BMC) and bone fracture energy (BFE) among different loading schemes (which proves the validity of the model),but also predict the realtime development pattern of BMC and BFE,as well as the dynamics of osteoblasts (OBA),osteoclasts (OCA),nitric oxide (NO) and prostaglandin E2 (PGE2) for each loading scheme,which can hardly be monitored through experiment.In conclusion,the model is the first of its kind that is able to provide an insight into the quantitative mechanism of bone remodeling at cellular level by which bone cells are activated by mechanical stimulus in order to start resorption/formation of bone mass.More importantly,this model has laid a solid foundation based on which future work such as systemic control theory analysis of bone remodeling under mechanical stimulus can be investigated.The to-be identified control mechanism will help to develop effective drugs and combined nonpharmacological therapies to combat bone loss pathologies.Also this deeper understanding of how mechanical forces quantitatively interact with skeletal tissue is essential for the generation of bone tissue for tissue replacement purposes in tissue engineering.

  1. Individuality of breathing patterns in patients under noninvasive mechanical ventilation evidenced by chaotic global models

    Science.gov (United States)

    Letellier, Christophe; Rodrigues, Giovani G.; Muir, Jean-François; Aguirre, Luis A.

    2013-03-01

    Autonomous global models based on radial basis functions were obtained from data measured from patients under noninvasive mechanical ventilation. Some of these models, which are discussed in the paper, turn out to have chaotic or quasi-periodic solutions, thus providing a first piece of evidence that the underlying dynamics of the data used to estimate the global models are likely to be chaotic or, at least, have a chaotic component. It is explicitly shown that one of such global models produces attractors characterized by a Horseshoe map, two models produce toroidal chaos, and one model produces a quasi-periodic regime. These topologically inequivalent attractors evidence the individuality of breathing profiles observed in patient under noninvasive ventilation.

  2. Aetiology of male urethritis in patients recruited from a population with a high HIV prevalence

    NARCIS (Netherlands)

    Sturm, P.D.J.; Moodley, P.; Khan, N.; Ebrahim, S.; Govender, K.; Connolly, C.E.; Sturm, A.W.

    2004-01-01

    The aetiology of urethritis, the significance of potential pathogens and the relation of urethritis to HIV infection were determined in 335 men (cases) with and 100 men (controls) without urethral symptoms. Urethral swab specimens were tested for different organisms by PCR or by culture for Neisseri

  3. A review of the current literature on aetiology and measurement methods of halitosis.

    NARCIS (Netherlands)

    Broek, A.M. van den; Feenstra, L.; Baat, C. de

    2007-01-01

    OBJECTIVES: This work reviews the current knowledge of aetiology and measurement methods of halitosis. DATA: Halitosis is an unpleasant or offensive odour emanating from the breath. The condition is multifactorial and may involve both oral and non-oral conditions. SOURCES: A private, monthly with ke

  4. Aetiology and resistance patterns of community-acquired pneumonia in León, Nicaragua

    NARCIS (Netherlands)

    Matute, A J; Brouwer, W P; Hak, E; Delgado, E; Alonso, E; Hoepelman, I M

    2006-01-01

    We conducted a prevalence study to gain greater insight into the aetiology, bacterial resistance and risk factors for community-acquired pneumonia (CAP) in the region of León, Nicaragua. During the period from July 2002 to January 2005, all consecutive patients with signs and symptoms suggestive of

  5. Perspectives on the Aetiology of ODD and CD: A Grounded Theory Approach

    Science.gov (United States)

    McFarland, Patrick; Sanders, James; Hagen, Bradley

    2016-01-01

    Antisocial disorders, such as oppositional defiant disorder (ODD) and conduct disorder (CD), are common reasons for youth to be seen for clinical intervention. The intent of this constructivist grounded theory study was to evaluate clinicians' perspectives on the aetiology of antisocial disorders. Six professionals from various professional…

  6. Value of rapid aetiological diagnosis in optimization of antimicrobial treatment in bacterial community acquired pneumonia.

    Science.gov (United States)

    Mareković, Ivana; Plecko, Vanda; Boras, Zagorka; Pavlović, Ladislav; Budimir, Ana; Bosnjak, Zrinka; Puretić, Hrvoje; Zele-Starcević, Lidija; Kalenić, Smilja

    2012-06-01

    In 80 adult patients with community acquired pneumonia (CAP) conventional microbiological methods, polymerase chain reaction (PCR) and serum C-reactive protein (CRP) levels were performed and the appropriateness of the empirical antimicrobial treatment was evaluated according to bacterial pathogen detected. The aetiology was determined in 42 (52.5%) patients, with Streptococcus pneumoniae as the most common pathogen. PCR applied to bronchoalveolar lavage (BAL) provided 2 and PCR on sputum samples 1 additional aetiological diagnosis of CAP The mean CRP values in the S. pneumoniae group were not significantly higher than in the group with other aetiological diagnoses (166.89 mg/L vs. 160.11 mg/L, p = 0.457). In 23.8% (10/42) of patients with determined aetiology, the empirical antimicrobial treatment was inappropriate. PCR tests need further investigation, particularly those for the atypical pathogens, as they are predominant in inappropriately treated patients. Our results do not support the use of CRP as a rapid test to guide the antimicrobial treatment in patients with CAP. PMID:22856222

  7. Aetiology of maxillofacial fractures: a review of published studies during the last 30 years

    NARCIS (Netherlands)

    P. Boffano; S.C. Kommers; K.H. Karagozoglu; T. Forouzanfar

    2014-01-01

    The epidemiology of facial trauma may vary widely across countries (and even within the same country), and is dependent on several cultural and socioeconomic factors. We know of few reviews of published reports that have considered the sex distribution and aetiology of maxillofacial trauma throughou

  8. Modeling and numerical analysis of granite rock specimen under mechanical loading and fire

    Directory of Open Access Journals (Sweden)

    Luc Leroy Ngueyep. Mambou

    2015-02-01

    Full Text Available The effect of ISO 834 fire on the mechanical properties of granite rock specimen submitted to uniaxial loading is numerically investigated. Based on Newton's second law, the rate-equation model of granite rock specimen under mechanical load and fire is established. The effect of heat treatment on the mechanical performance of granite is analyzed at the center and the ends of specimen. At the free end of granite rock specimen, it is shown that from 20 °C to 500 °C, the internal stress and internal strain are weak; whereas above 500 °C, they start to increase rapidly, announcing the imminent collapse. At the center of specimen, the analysis of the internal stress and internal strain reveals that the fire reduces the mechanical performance of granite significantly. Moreover, it is found that after 3 min of exposure to fire, the mechanical energy necessary to fragment the granite can be reduced up to 80%.

  9. Main mechanisms of material properties degradation under reactor pressure vessel operating conditions

    International Nuclear Information System (INIS)

    In the process of NPP equipment operation materials are subjected to a prolonged influence of loads, associated with the variation of inner pressure and temperature under various conditions. Each equipment element damage is associated with some material fracture mechanism. For NPP equipment the mechanisms of irreversible damage accumulation are related with: irradiation embrittlement, thermal and strain aging, fatigue damages from mechanical and thermal loading, stress corrosion and fatigue corrosion, creep and thermal relaxation stresses, erosion and weak, thermal shock. The basic tasks of specialists working in the sphere of the provision of reliability and service life of nuclear power equipment are not only the determination of the main mechanisms of damages and reasons of their appearance, but also the study of methods which would permit to control these properties completely. By giving some examples of Russian NPP equipment with VVER-440 and VVER-1000 reactors the paper presents most typical degradation mechanisms of equipment material properties, including weldments, in the process of operation and methods to recover by using various technological means. (author)

  10. Modelling of damage initiation mechanism in rubber sheet composites under the static loading

    Directory of Open Access Journals (Sweden)

    T. Da Silva Botelho

    2007-06-01

    Full Text Available Purpose: Modelling – Finite Element Analysis (FEA of the damage initiation mechanisms in thin rubber sheet composites were carried out under static solicitation at room temperature. Natural rubber vulcanised and reinforced by carbon, NR is used in this study.Design/methodology/approach: Experimental results were compared with that of the Finite Element Analysis (FEA. Damage mechanism has been described with a threshold criterion to identify the tearing resistance, characteristic energy for tearing (T and damage in the specimens was evaluated just at the beginning of the tearing by assuming large strain. Typical specimen geometry of thin sheet rubber composite materials was considered under static tensile tests conducted on the smooth and notched specimens with variable depths.Findings: This stage of this research, a finite element analysis (FEA has been applied under the same conditions of this part in order to obtain the agreement between experimental and FEA results. The numerical modelling is a representation of a previous experimental study. The specimen is stretched more than once its initial size, so that large strains occur. A hyper elastic Mooney-Rivlin law and a Griffith criterion are chosen.Practical implications: A tearing criterion was suggested in the case of simple tension conditions by assuming large strain. In the next step of this study, a finite element analysis (FEA will be applied under the same conditions of this part in order to obtain the agreement between experimental and FEA results.Originality/value: This study proposes a threshold criterion for the damage just at the beginning of the tearing for thin sheet rubber composites and gives a detail discussion for explaining the damage mechanisms. Comparison of FEA results with those of experimental studies gives many facilities for the sake of simplicity in industrial application.

  11. Mechanisms of hydroxyl radical production from abiotic oxidation of pyrite under acidic conditions

    Science.gov (United States)

    Zhang, Peng; Yuan, Songhu; Liao, Peng

    2016-01-01

    Hydroxyl radicals (radOH) produced from pyrite oxidation by O2 have been recognized, but mechanisms regarding the production under anoxic and oxic conditions are not well understood. In this study, the mechanisms of radOH production from pyrite oxidation under anoxic and oxic conditions were explored using benzoic acid (BA) as an radOH probe. Batch experiments were conducted at pH 2.6 to explore radOH production under anoxic and oxic conditions. The cumulative radOH concentrations produced under anoxic and oxic conditions increased linearly to 7.5 and 52.2 μM, respectively within 10 h at 10 g/L pyrite. Under anoxic conditions, radOH was produced from the oxidation of H2O on the sulfur-deficient sites on pyrite surface, showing an increased production with the increase of pyrite surface exposure due to oxidation. Under oxic conditions, the formation of radOH proceeds predominantly via the two-electron reduction of O2 on pyrite surface along with a minor contribution from the oxidation of H2O on surface sulfur-defects and the reactions of Fe2+/sulfur intermediates with O2. For both O2 reduction and H2O oxidation on the surface sulfur-defects, H2O2 was the predominant intermediate, which subsequently transformed to radOH through Fenton mechanism. The radOH produced had a significant impact on the transformation of contaminants in the environment. Anoxic pyrite suspensions oxidized 13.9% As(III) (C0 = 6.67 μM) and 17.6% sulfanilamide (C0 = 2.91 μM) within 10 h at pH 2.6 and 10 g/L pyrite, while oxic pyrite suspensions improved the oxidation percentages to 55.4% for As(III) and 51.9% for sulfanilamide. The ratios of anoxic to oxic oxidation are consistent with the relative contribution of surface sulfur-defects to radOH production. However, Fe2+ produced from pyrite oxidation competed with the contaminants for radOH, which is of particular significance with the increase of time in a static environment. We conclude that radOH can be produced from abiotic oxidation of

  12. Psychogenic non-epileptic seizures: so-called psychiatric comorbidity and underlying defense mechanisms

    Directory of Open Access Journals (Sweden)

    Beghi M

    2015-09-01

    Full Text Available Massimiliano Beghi,1,2 Paola Beffa Negrini,1 Cecilia Perin,1,3 Federica Peroni,1,3 Adriana Magaudda,4 Cesare Cerri,1,3 Cesare Maria Cornaggia1,3 1Department of Surgery and Translational Medicine, University of Milano-Bicocca, 2Department of Mental Health, “Guido Salvini” Hospital, Garbagnate Milanese, Milan, Italy; 3Rehabilitation Medicine, Istituti Clinici Zucchi, Carate Brianza, Monza and Brianza, Italy; 4Epilepsy Center, Department of Neuroscience, University of Messina, Messina, Italy Abstract: In Diagnostic and Statistical Manual of Mental Disorders, fifth edition, psychogenic non-epileptic seizures (PNES do not have a unique classification as they can be found within different categories: conversion, dissociative, and somatization disorders. The ICD-10, instead, considers PNES within dissociative disorders, merging the dissociative disorders and conversion disorders, although the underlying defense mechanisms are different. The literature data show that PNES are associated with cluster B (mainly borderline personality disorders and/or to people with depressive or anxiety disorders. Defense mechanisms in patients with PNES with a prevalence of anxious/depressive symptoms are of “neurotic” type; their goal is to lead to a “split”, either vertical (dissociation or horizontal (repression. The majority of patients with this type of PNES have alexithymia traits, meaning that they had difficulties in feeling or perceiving emotions. In subjects where PNES are associated with a borderline personality, in which the symbolic function is lost, the defense mechanisms are of a more archaic nature (denial. PNES with different underlying defense mechanisms have different prognoses (despite similar severity of PNES and need usually a different treatment (pharmacological or psychological. Thus, it appears superfluous to talk about psychiatric comorbidity, since PNES are a different symptomatic expression of specific psychiatric disorders

  13. Interactive evolution concept for analyzing a rock salt cavern under cyclic thermo-mechanical loading

    Science.gov (United States)

    König, Diethard; Mahmoudi, Elham; Khaledi, Kavan; von Blumenthal, Achim; Schanz, Tom

    2016-04-01

    The excess electricity produced by renewable energy sources available during off-peak periods of consumption can be used e.g. to produce and compress hydrogen or to compress air. Afterwards the pressurized gas is stored in the rock salt cavities. During this process, thermo-mechanical cyclic loading is applied to the rock salt surrounding the cavern. Compared to the operation of conventional storage caverns in rock salt the frequencies of filling and discharging cycles and therefore the thermo-mechanical loading cycles are much higher, e.g. daily or weekly compared to seasonally or yearly. The stress strain behavior of rock salt as well as the deformation behavior and the stability of caverns in rock salt under such loading conditions are unknown. To overcome this, existing experimental studies have to be supplemented by exploring the behavior of rock salt under combined thermo-mechanical cyclic loading. Existing constitutive relations have to be extended to cover degradation of rock salt under thermo-mechanical cyclic loading. At least the complex system of a cavern in rock salt under these loading conditions has to be analyzed by numerical modeling taking into account the uncertainties due to limited access in large depth to investigate material composition and properties. An interactive evolution concept is presented to link the different components of such a study - experimental modeling, constitutive modeling and numerical modeling. A triaxial experimental setup is designed to characterize the cyclic thermo-mechanical behavior of rock salt. The imposed boundary conditions in the experimental setup are assumed to be similar to the stress state obtained from a full-scale numerical simulation. The computational model relies primarily on the governing constitutive model for predicting the behavior of rock salt cavity. Hence, a sophisticated elasto-viscoplastic creep constitutive model is developed to take into account the dilatancy and damage progress, as well as

  14. Refeeding syndrome in children with different clinical aetiology.

    Science.gov (United States)

    Lenicek Krleza, J; Misak, Z; Jadresin, O; Skaric, I

    2013-08-01

    Refeeding syndrome (RFS) is a well-described state of the series of metabolic and biochemical changes that can occur during the feeding of malnourished persons. The shifts in fluids and electrolytes can lead to complications during artificial feeding, which if not recognised and untreated can lead to death. Although the physiology and pathophysiology of RFS is well known, the circumstances under which the RFS appears, clinical manifestations and management of these patients are less clear. There are few published studies describing the occurrence of RFS in children. We describe two cases of RFS in children. The first case is a boy with unrecognised coeliac disease and second case is a girl with cerebral palsy. In both cases, the RFS has developed without clinical symptoms and it was shown only through laboratory findings. Electrolyte disturbances have been successfully corrected and treatment of the underlying disease continued.

  15. Mechanisms underlying reductions in stroke volume at rest and during exercise at high altitude.

    Science.gov (United States)

    Stembridge, Mike; Ainslie, Philip N; Shave, Rob

    2016-08-01

    High-altitude exposure challenges the cardiovascular system to maintain oxygen delivery to the mitochondria under conditions of hypoxic stress. Following acclimatisation (3-5 days), stroke volume (SV) falls to below sea-level values but heart rate remains elevated, such that cardiac output is maintained compared to sea level. The decrease in SV has been a topic of research for over 40 years, but the underlying mechanisms are incompletely understood. Impaired systolic contractile function secondary to reduced coronary arterial oxygen tension has been investigated as a potential cause for the decrease in SV. However, despite in vitro evidence of impaired cardiac contractile force in severe hypoxia, the majority of studies to date have reported enhanced in vivo ventricular systolic function at rest and during exercise in humans up to and above 5000 m. However, the elevated function observed at rest has recently been suggested to reduce the functional reserve available during exercise. While in vivo systolic function appears enhanced at high altitude, a decrease in left ventricular end-diastolic volume (EDV) and altered filling patterns of both ventricles has been observed. The reduction in ventricular filling will undoubtedly affect SV, and four potential mechanisms have been proposed to explain the reduction in left ventricular filling. In this article, both historical and recent reports of systolic function at high altitude will be reviewed, and evidence supporting and refuting each of the four mechanisms underpinning reduced left ventricular filling will be discussed. PMID:26325452

  16. Failure mechanism of monolayer graphene under hypervelocity impact of spherical projectile.

    Science.gov (United States)

    Xia, Kang; Zhan, Haifei; Hu, De'an; Gu, Yuantong

    2016-01-01

    The excellent mechanical properties of graphene have enabled it as appealing candidate in the field of impact protection or protective shield. By considering a monolayer graphene membrane, in this work, we assessed its deformation mechanisms under hypervelocity impact (from 2 to 6 km/s), based on a serial of in silico studies. It is found that the cracks are formed preferentially in the zigzag directions which are consistent with that observed from tensile deformation. Specifically, the boundary condition is found to exert an obvious influence on the stress distribution and transmission during the impact process, which eventually influences the penetration energy and crack growth. For similar sample size, the circular shape graphene possesses the best impact resistance, followed by hexagonal graphene membrane. Moreover, it is found the failure shape of graphene membrane has a strong relationship with the initial kinetic energy of the projectile. The higher kinetic energy, the more number the cracks. This study provides a fundamental understanding of the deformation mechanisms of monolayer graphene under impact, which is crucial in order to facilitate their emerging future applications for impact protection, such as protective shield from orbital debris for spacecraft. PMID:27618989

  17. Ageing and Static Reliability of Concrete Structures under Temperature and Mechanical Loading

    International Nuclear Information System (INIS)

    The contribution presents some aspects of the static reliability of concrete structures under temperature effects and under mechanical loading. The mathematical model of a load-bearing concrete structure was performed using the FEM method. The temperature field and static stress that generated states of stress were taken into account. A brief description of some aspects of evaluation of the reliability within the primary circuit concrete structures is stated. The knowledge of actual physical and mechanical characteristics and chemical composition of concrete were necessary for obtaining correct results of numerical analysis. Studied problems were divided into a number of fields and worked out in details: 1. Verification of contemporary physical and mechanical characteristics of concrete (input parameters of the FEM models). 2. Checking of the concrete microstructure and verification of the grade and kind of possible microstructure changes. 3. Experimental verification of the boundary conditions from point of view of the temperature field and the radiation stress. 4. Setting up a mathematical model of the structure for an examination of the interaction of temperature and static stresses (finite element method, software ANSYS) in two alternatives: a) Macro-model representing the essential part of concrete structures in the proximity of the reactor, b) Model of extremely stressed parts of the concrete structure (a part of the macro-model)

  18. Transdifferentiation of pancreatic α-cells into insulinsecreting cells: From experimental models to underlying mechanisms

    Institute of Scientific and Technical Information of China (English)

    Jieli; Lu; Rami; Jaafer; Rémy; Bonnavion; Philippe; Bertolino; Chang-Xian; Zhang

    2014-01-01

    Pancreatic insulin-secreting β-cells are essential regulators of glucose metabolism. New strategies are cur-rently being investigated to create insulin-producing β cells to replace deficient β cells, including the differentiation of either stem or progenitor cells, and the newly uncovered transdifferentiation of mature non-β islet cell types. However, in order to correctly drive any cell to adopt a new β-cell fate, a better understanding of the in vivo mechanisms involved in the plasticity and biology of islet cells is urgently required. Here, we review the recent studies reporting the phenomenon of transdifferentiation of α cells into β cells by focusing on the major candidates and contexts revealed to be involved in adult β-cell regeneration through this process. The possible underlying mechanisms of transdifferentiation and the interactions between several key factors involved in the process are also addressed. We propose that it is of importance to further study the molecular and cellular mechanisms underlying α- to β-cell transdifferentiation, in order to make β-cell regeneration from α cells a relevant and realizable strategy for developing cell-replacement therapy.

  19. Mechanism Underlying the Spatial Pattern Formation of Dominant Tree Species in a Natural Secondary Forest.

    Directory of Open Access Journals (Sweden)

    Guodong Jia

    Full Text Available Studying the spatial pattern of plant species may provide significant insights into processes and mechanisms that maintain stand stability. To better understand the dynamics of naturally regenerated secondary forests, univariate and bivariate Ripley's L(r functions were employed to evaluate intra-/interspecific relationships of four dominant tree species (Populus davidiana, Betula platyphylla, Larix gmelinii and Acer mono and to distinguish the underlying mechanism of spatial distribution. The results showed that the distribution of soil, water and nutrients was not fragmented but presented clear gradients. An overall aggregated distribution existed at most distances. No correlation was found between the spatial pattern of soil conditions and that of trees. Both positive and negative intra- and interspecific relationships were found between different DBH classes at various distances. Large trees did not show systematic inhibition of the saplings. By contrast, the inhibition intensified as the height differences increased between the compared pairs. Except for Larix, universal inhibition of saplings by upper layer trees occurred among other species, and this reflected the vertical competition for light. Therefore, we believe that competition for light rather than soil nutrients underlies the mechanism driving the formation of stand spatial pattern in the rocky mountainous areas examined.

  20. Mechanical and structural characterization of tibial prosthetic interfaces before and after aging under simulated service conditions.

    Science.gov (United States)

    Cavaco, A; Ramalho, A; Pais, S; Durães, L

    2015-03-01

    Prosthesis interface is one of the most important components to promote individual׳s health and comfort, as it establishes direct contact with the skin and transfers loads generated during gait. The aim of this study was to mechanically characterize, three commercial interfaces (block copolymer, silicone gel and silicone elestomer), under static and dynamic conditions, before and after undergoing a process of chemical aging in synthetic sweat for periods up to 90 days. Static mechanical compression tests were performed on the materials, as well as fatigue tests to assess their static and dynamic mechanical behaviors, respectively. For the second, a sinusoidal load was applied with an appropriate range of deformation for each material. Several analytical techniques were also used to characterize the materials, namely Fourier Transform Infrared Spectroscopy (FTIR), X-ray diffraction (XRD), and morphology characterization by Scanning Electron Microscopy (SEM). All the tested materials have strong viscoelastic behavior, showing a linear response for small deformations, followed by a nonlinear behavior for higher deformation. The block copolymer and the silicone gel are affected by aging in synthetic sweat in a similar way, with a significant increase of their rigidity after 30 days, followed by a progressive reduction. The silicone elastomer displays a continuous increase of rigidity along the 90 days of storage, being the most sensitive to aging affects. It also exhibits the lowest stiffness value, being suitable for uses that require maximum comfort. All materials demonstrate chemical and structural stability under service simulated conditions. PMID:25554916

  1. Mechanism Underlying the Spatial Pattern Formation of Dominant Tree Species in a Natural Secondary Forest.

    Science.gov (United States)

    Jia, Guodong; Yu, Xinxiao; Fan, Dengxing; Jia, Jianbo

    2016-01-01

    Studying the spatial pattern of plant species may provide significant insights into processes and mechanisms that maintain stand stability. To better understand the dynamics of naturally regenerated secondary forests, univariate and bivariate Ripley's L(r) functions were employed to evaluate intra-/interspecific relationships of four dominant tree species (Populus davidiana, Betula platyphylla, Larix gmelinii and Acer mono) and to distinguish the underlying mechanism of spatial distribution. The results showed that the distribution of soil, water and nutrients was not fragmented but presented clear gradients. An overall aggregated distribution existed at most distances. No correlation was found between the spatial pattern of soil conditions and that of trees. Both positive and negative intra- and interspecific relationships were found between different DBH classes at various distances. Large trees did not show systematic inhibition of the saplings. By contrast, the inhibition intensified as the height differences increased between the compared pairs. Except for Larix, universal inhibition of saplings by upper layer trees occurred among other species, and this reflected the vertical competition for light. Therefore, we believe that competition for light rather than soil nutrients underlies the mechanism driving the formation of stand spatial pattern in the rocky mountainous areas examined. PMID:27028757

  2. Music and literature: are there shared empathy and predictive mechanisms underlying their affective impact?

    Directory of Open Access Journals (Sweden)

    Diana eOmigie

    2015-08-01

    Full Text Available It has been suggested that music and language had a shared evolutionary precursor before becoming mainly responsible for the communication of emotive and referential meaning respectively. However, emphasis on potential differences between music and language may discourage a consideration of the commonalities that music and literature share. Indeed, one possibility is that common mechanisms underlie their affective impact, and the current paper carefully reviews relevant neuroscientific findings to examine such a prospect. First and foremost, it will be demonstrated that considerable evidence of a common role of empathy and predictive processes now exists for the two domains. However, it will also be noted that an important open question remains: namely, whether the mechanisms underlying the subjective experience of uncertainty differ between the two with respect to recruitment of phylogenetically ancient emotion areas. It will be concluded that a comparative approach may not only help to reveal general mechanisms underlying our responses to music and literature, but may also help us better understand any idiosyncrasies in their capacity for affective impact.

  3. Music and literature: are there shared empathy and predictive mechanisms underlying their affective impact?

    Science.gov (United States)

    Omigie, Diana

    2015-01-01

    It has been suggested that music and language had a shared evolutionary precursor before becoming mainly responsible for the communication of emotive and referential meaning respectively. However, emphasis on potential differences between music and language may discourage a consideration of the commonalities that music and literature share. Indeed, one possibility is that common mechanisms underlie their affective impact, and the current paper carefully reviews relevant neuroscientific findings to examine such a prospect. First and foremost, it will be demonstrated that considerable evidence of a common role of empathy and predictive processes now exists for the two domains. However, it will also be noted that an important open question remains: namely, whether the mechanisms underlying the subjective experience of uncertainty differ between the two domains with respect to recruitment of phylogenetically ancient emotion areas. It will be concluded that a comparative approach may not only help to reveal general mechanisms underlying our responses to music and literature, but may also help us better understand any idiosyncrasies in their capacity for affective impact. PMID:26379583

  4. Handedness is related to neural mechanisms underlying hemispheric lateralization of face processing

    Science.gov (United States)

    Frässle, Stefan; Krach, Sören; Paulus, Frieder Michel; Jansen, Andreas

    2016-01-01

    While the right-hemispheric lateralization of the face perception network is well established, recent evidence suggests that handedness affects the cerebral lateralization of face processing at the hierarchical level of the fusiform face area (FFA). However, the neural mechanisms underlying differential hemispheric lateralization of face perception in right- and left-handers are largely unknown. Using dynamic causal modeling (DCM) for fMRI, we aimed to unravel the putative processes that mediate handedness-related differences by investigating the effective connectivity in the bilateral core face perception network. Our results reveal an enhanced recruitment of the left FFA in left-handers compared to right-handers, as evidenced by more pronounced face-specific modulatory influences on both intra- and interhemispheric connections. As structural and physiological correlates of handedness-related differences in face processing, right- and left-handers varied with regard to their gray matter volume in the left fusiform gyrus and their pupil responses to face stimuli. Overall, these results describe how handedness is related to the lateralization of the core face perception network, and point to different neural mechanisms underlying face processing in right- and left-handers. In a wider context, this demonstrates the entanglement of structurally and functionally remote brain networks, suggesting a broader underlying process regulating brain lateralization. PMID:27250879

  5. Mechanisms underlying feed intolerance in the critically ill: Implications for treatment

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Malnutrition is associated with poor outcomes in critically ill patients. Although nutritional support is yet to be proven to improve mortality in non-malnourished critically ill patients, early enteral feeding is considered best practice. However, enteral feeding is often limited by delayed gastric emptying. The best method to clinically identify delayed gastric emptying and feed intolerance is unclear. Gastric residual volume (GRV)measured at the bedside is widely used as a surrogate marker for gastric emptying, but the value of GRV measurement has recently been disputed. While the mechanisms underlying delayed gastric emptying require further investigation, recent research has given a better appreciation of the pathophysiology. A number of pharmacological strategies are available to improve the success of feeding. Recent data suggest a combination of intravenous metoclopramide and erythromycin to be the most successful treatment, but novel drug therapies should be explored. Simpler methods to access the duodenum and more distal small bowel for feed delivery are also under investigation. This review summarises current understanding of the factors responsible for, and mechanisms underlying feed intolerance in critical illness,together with the evidence for current practices. Areas requiring further research are also highlighted.

  6. Advances in fracture mechanics analyses of primary system performance under operating and accident conditions

    International Nuclear Information System (INIS)

    Safety research sponsored by the Nuclear Regulatory Commission, Division of Reactor Safety Research, has resulted in notable advances in several areas of importance in the safety evaluation of reactor primary systems under normal operations and accident situations. First, the methods of linear elastic fracture mechanics and of elastic plastic fracture mechanics have been validated for prediction of pressure vessel performance by the Intermediate Vessel Test program results at the Oak Ridge National Laboratory. The ability confidently to predict vessel performance under realistic service conditions has permitted development of the computer program OCTAVIA which computes failure curves for a range of flaw sizes in terms of pressure and temperature for specified presure vessel material at specific neutron fluence levels. It then considers the probability of occurrence of flaw sizes and magnitude of pressure during an operational, overpressurization transient and determines the probability of failure, for both individual flaw sizes and for the full spectrum. This advance has been verified by the confirmatory results of testing small thick-walled cylinders under thermal shock conditions in the Heavy Section Steel Technology program, and of warm prestressing tests at the US Navel Research Laboratory. Thirdly, the technology of crack arrest has reached a level wherein standardization of test specimens and testing methods is now possible and, indeed, is underway. (Auth.)

  7. Handedness is related to neural mechanisms underlying hemispheric lateralization of face processing

    Science.gov (United States)

    Frässle, Stefan; Krach, Sören; Paulus, Frieder Michel; Jansen, Andreas

    2016-06-01

    While the right-hemispheric lateralization of the face perception network is well established, recent evidence suggests that handedness affects the cerebral lateralization of face processing at the hierarchical level of the fusiform face area (FFA). However, the neural mechanisms underlying differential hemispheric lateralization of face perception in right- and left-handers are largely unknown. Using dynamic causal modeling (DCM) for fMRI, we aimed to unravel the putative processes that mediate handedness-related differences by investigating the effective connectivity in the bilateral core face perception network. Our results reveal an enhanced recruitment of the left FFA in left-handers compared to right-handers, as evidenced by more pronounced face-specific modulatory influences on both intra- and interhemispheric connections. As structural and physiological correlates of handedness-related differences in face processing, right- and left-handers varied with regard to their gray matter volume in the left fusiform gyrus and their pupil responses to face stimuli. Overall, these results describe how handedness is related to the lateralization of the core face perception network, and point to different neural mechanisms underlying face processing in right- and left-handers. In a wider context, this demonstrates the entanglement of structurally and functionally remote brain networks, suggesting a broader underlying process regulating brain lateralization.

  8. Fatigue behaviour of the austenitic steel 1.4550 under mechanical and thermal cyclic loading

    Energy Technology Data Exchange (ETDEWEB)

    Siegele, D.; Fingerhuth, J.; Varfolomeev, I.; Moroz, S. [Fraunhofer Institute for Mechanics of Materials (IWM), Freiburg (Germany)

    2014-07-01

    Fatigue behaviour of the austenitic steel 1.4550 (X6CrNiNb18-10) under low-cycle fatigue and high-cycle thermal fatigue was investigated with in two research projects supported by the Federal Ministry of Economic Affairs and Energy and the Ministry of Education and Research. The objectives of the projects were the gain of deep understanding of the damage mechanisms under mechanical and thermal cyclic loading and the development of material models and simulation procedures for an improved lifetime assessment. In comparison to the advanced mechanism based material models engineering computational procedures were proven with respect to their applicability and conservatisms. For thermal cyclic loading, test equipment and technique were developed which allow for cyclic thermal loading with temperature ranges between 1 00 C and 300 C and frequencies between 0.1 and 1 Hz. As a result, tests with a temperature range of 150 C and lower showed no crack formation up to 300,000 cycles. For temperature ranges of 200 C and higher multiple crack patterns were observed with the deepest crack of about 1.3 mm after 1,000,000 cycles, whereas the difference in crack depth between 300,000 and 1,000,000 cycles was negligibly small. To model the fatigue lifetime, the D{sub TMF} damage parameter was applied to the low-cycle fatigue and the thermal, high frequent fatigue tests. For thermal fatigue, the analyses predicted in agreement with the tests crack initiation followed by crack propagation, subsequent retardation and arrest. This behaviour can be explained qualitatively and quantitatively using the methods of linear-elastic fracture mechanics, whereas the consideration of the interaction of multiple cracks is essential to describe the experimentally observed crack retardation. The results for thermal fatigue are in the scatterband of the mechanical p and thermo-mechanical fatigue results and the cycles to failure are 10 times higher than those estimated according to the KTA fatigue

  9. Kidney branching morphogenesis under the control of a ligand–receptor-based Turing mechanism

    International Nuclear Information System (INIS)

    The main signalling proteins that control early kidney branching have been defined. Yet the underlying mechanism is still elusive. We have previously shown that a Schnakenberg-type Turing mechanism can recapitulate the branching and protein expression patterns in wild-type and mutant lungs, but it is unclear whether this mechanism would extend to other branched organs that are regulated by other proteins. Here, we show that the glial cell line-derived neurotrophic factor–RET regulatory interaction gives rise to a Schnakenberg-type Turing model that reproduces the observed budding of the ureteric bud from the Wolffian duct, its invasion into the mesenchyme and the observed branching pattern. The model also recapitulates all relevant protein expression patterns in wild-type and mutant mice. The lung and kidney models are both based on a particular receptor–ligand interaction and require (1) cooperative binding of ligand and receptor, (2) a lower diffusion coefficient for the receptor than for the ligand and (3) an increase in the receptor concentration in response to receptor–ligand binding (by enhanced transcription, more recycling or similar). These conditions are met also by other receptor–ligand systems. We propose that ligand–receptor-based Turing patterns represent a general mechanism to control branching morphogenesis and other developmental processes. (paper)

  10. Peripheral afferent mechanisms underlying acupuncture inhibition of cocaine behavioral effects in rats.

    Directory of Open Access Journals (Sweden)

    Seol Ah Kim

    Full Text Available Administration of cocaine increases locomotor activity by enhancing dopamine transmission. To explore the peripheral mechanisms underlying acupuncture treatment for drug addiction, we developed a novel mechanical acupuncture instrument (MAI for objective mechanical stimulation. The aim of this study was to evaluate whether acupuncture inhibition of cocaine-induced locomotor activity is mediated through specific peripheral nerves, the afferents from superficial or deep tissues, or specific groups of nerve fibers. Mechanical stimulation of acupuncture point HT7 with MAI suppressed cocaine-induced locomotor activity in a stimulus time-dependent manner, which was blocked by severing the ulnar nerve or by local anesthesia. Suppression of cocaine-induced locomotor activity was elicited after HT7 stimulation at frequencies of either 50 (for Meissner corpuscles or 200 (for Pacinian corpuscles Hz and was not affected by block of C/Aδ-fibers in the ulnar nerve with resiniferatoxin, nor generated by direct stimulation of C/Aδ-fiber afferents with capsaicin. These findings suggest that HT7 inhibition of cocaine-induced locomotor activity is mediated by A-fiber activation of ulnar nerve that originates in superficial and deep tissue.

  11. The Dynamic Evolution of Firms’ Pollution Control Strategy under Graded Reward-Penalty Mechanism

    Directory of Open Access Journals (Sweden)

    Li Ming Chen

    2016-01-01

    Full Text Available The externality of pollution problem makes firms lack enough incentive to reduce pollution emission. Therefore, it is necessary to design a reasonable environmental regulation mechanism so as to effectively urge firms to control pollution. In order to inspire firms to control pollution, we divide firms into different grades according to their pollution level and construct an evolutionary game model to analyze the interaction between government’s regulation and firms’ pollution control under graded reward-penalty mechanism. Then, we discuss stability of firms’ pollution control strategy and derive the condition of inspiring firms to control pollution. Our findings indicate that firms tend to control pollution after long-term repeated games if government’s excitation level and monitoring frequency meet some conditions. Otherwise, firms tend to discharge pollution that exceeds the stipulated standards. As a result, in order to effectively control pollution, a government should adjust its excitation level and monitoring frequency reasonably.

  12. Tracking Control of the Flexible SLIDER-CRANK Mechanism System Under Impact

    Science.gov (United States)

    FUNG, R.-F.; SUN, J.-H.; WU, J.-W.

    2002-08-01

    The variable structure control (VSC) and the stabilizer design by using pole placement technique are applied to the tracking control of the flexible slider-crank mechanism under impact. The VSC strategy is employed to track the crank angular position and speed, while the stabilizer design is involved to suppress the flexible vibrations simultaneously. From the theoretical impact consideration, three approaches including the generalized momentum balance (GMB), the continuous force model (CFM), and the CFM associated with the effective mass compensation EMC are adopted, and are derived on the basis of the energy and impulse-momentum conservations. Simulation results are provided to demonstrate the performance of the motor-controller flexible slider-crank mechanism not only accomplishing good tracking trajectory of the crank angle, but also eliminating vibrations of the flexible connecting rod.

  13. The Potential Mechanisms Underlying Aspirin-induced Inhibition of Ovarian Tumor Cell Growth

    Institute of Scientific and Technical Information of China (English)

    Yu LIU; Jin KE; Shi-Quan LIU; Fu-Xiang ZHOU; Cong-Hua XIE; Yun-Feng ZHOU

    2005-01-01

    @@ 1 Introduction Ovarian cancer remains the most lethal disease of the gynecological cancers. Owing to the lack of an effective screening approach combined with inadequate therapeutic approach for advanced disease, fewer than 25% of ovarian cancers are identified at an early curable stage. Thus these make ovarian cancer a strong candidate for chemoprevention. In 2001, Akhmedkhanov et al. demonstrated a 2-3 folds decrease in epithelial ovarian cancer associated with Aspirin use. These epidemiological observations suggest that an improved understanding of the mechanisms by which NSAID may decrease the development of ovarian cancer could lead to improved approaches for chemoprevention of this deadly disease. In this research, we explored the potential mechanism underlying epidemiological observations that ovarian cancer occurs at a lower frequency in women exposed to Aspirin(ASP).

  14. Atrial Arrhythmias in Obstructive Sleep Apnea: Underlying Mechanisms and Implications in the Clinical Setting

    Directory of Open Access Journals (Sweden)

    David Filgueiras-Rama

    2013-01-01

    Full Text Available Obstructive sleep apnea (OSA is a common disorder characterized by repetitive interruption of ventilation during sleep caused by recurrent upper airway collapse, which leads to intermittent hypoxia. The disorder is commonly undiagnosed despite its relationship with substantial cardiovascular morbidity and mortality. Moreover, the effects of the disorder appear to be particularly dangerous in young subjects. In the last decade, substantial clinical evidence has identified OSA as independent risk factor for both bradyarrhythmias and tachyarrhythmias. To date the mechanisms leading to such arrhythmias have not been completely understood. However, recent data from animal models and new molecular analyses have increased our knowledge of the field, which might lead to future improvement in current therapeutic strategies mainly based on continuous positive airway pressure. This paper aims at providing readers a brief and specific revision of current knowledge about the mechanisms underlying atrial arrhythmias in OSA and their clinical and therapeutic implications.

  15. Three dimensional damage mechanics analysis of real life reactor piping components under various loading conditions

    Energy Technology Data Exchange (ETDEWEB)

    Durgaprasad, P.V.; Sahu, M.K.; Dutta, B.K. (Reactor Safety Division, Bhabha Atomic Research Centre Trombay, Mumbai (India)), e-mail: pvdp@barc.gov.in

    2009-07-01

    In this work, the Gurson-Tvergaard-Needleman (GTN) damage mechanics model is used for the crack growth analysis of real life reactor piping components. The paper also addresses the challenges involved in such analyses. As a part of component integrity testing, a comprehensive experimental program has been pursued to generate the fracture behavior of reactor piping components. Several real life pipes and elbows with various flaw sizes have been tested under different loading conditions like temperature, pressure, bending etc. In the present work, some of the selected components have been analyzed numerically by using parallel in-house finite element code 'MADAM' with GTN constitutive model. The strength of the micro mechanical models has been demonstrated by comparing the numerical results like load v/s. load-line displacements, J-R curves with the experimental data

  16. Fundamental mechanism underlying subwavelength optics of metamaterials: Charge oscillation-induced light emission and interference

    CERN Document Server

    Huang, X R; Wang, Mu

    2009-01-01

    Interactions between light and conducting nanostructures can result in a variety of novel and fascinating phenomena. These properties may have wide applications, but their underlying mechanisms have not been completely understood. From calculations of surface charge density waves on conducting gratings and by comparing them with classical surface plasmons, we revealed a general yet concrete picture about coupling of light to free electron oscillation on structured conducting surfaces that can lead to oscillating subwavelength charge patterns (i.e., spoof surface plasmons but without the dispersion property of classical surface plasmons). New wavelets emitted from these light sources then destructively interfere to form evanescent waves. This principle, usually combined with other mechanisms (e.g. resonance), is mainly a geometrical effect that can be universally involved in light scattering from all periodic and nonperiodic structures containing free electrons, including perfect conductors. The spoof surface ...

  17. Modeling stresses in piezoelectric smart structures under combined thermal and mechanical excitations

    Science.gov (United States)

    Koko, Tamunoiyala S.; Smith, Malcolm J.; Orisamolu, Irewole R.

    1999-06-01

    In this paper, the integrated finite element methodology developed in our earlier work for designing active vibration control strategies in smart structures, is extended to compute the stresses and strains in the structure, due to combined thermal, mechanical and electrical excitations. A layered composite brick elements with linear strain-displacement and linear thermopiezoelectric constitutive relations is used to model the structure. The method, which has been encoded into a software called SMARTCOM provides a design and analysis capability that simultaneously accounts for the coupled thermopiezoelectric and control capabilities of the smart structural systems. Numerical examples are provided for structures with surface bonded piezoelectric sensors and actuators, under various types of mechanical, thermal and electrical load. Comparisons are made to other available solutions to verify the accuracy of the SMARTCOM simulations. The method provides accurate results and is seen as a valuable tool for the design and analysis of these smart structures.

  18. DAMAGE MECHANISM ANALYSIS OF 2D 1 × 1 BRAIDED COMPOSITES UNDER UNIDIRECTIONAL TENSION

    Institute of Scientific and Technical Information of China (English)

    张超; 许希武; 陈康

    2013-01-01

    Coupling with the periodical displacement boundary condition ,a representative volume element (RVE) model is established to simulate the progressive damage behavior of 2D 1 × 1 braided composites under unidirection-al tension by using the nonlinear finite element method .Tsai-Wu failure criterion with various damage modes and Mises criterion are considered for predicting damage initiation and progression of yarns and matrix .The anisotropic damage model for yarns and the isotropic damage model for matrix are used to simulate the microscopic damage propagation of 2D 1 × 1 braided composites .Murakami′s damage tensor is adopted to characterize each damage mode .In the simulation process ,the damage mechanisms are revealed and the tensile strength of 2D 1 × 1 braided composites is predicted from the calculated average stress-average strain curve . Numerical results show good agreement with experimental data ,thus the proposed simulation method is verified for damage mechanism analysis of 2D braided composites .

  19. A hypothesis regarding the molecular mechanism underlying dietary soy-induced effects on seizure propensity.

    Directory of Open Access Journals (Sweden)

    Cara Jean Westmark

    2014-09-01

    Full Text Available Numerous neurological disorders including fragile X syndrome, Down syndrome, autism and Alzheimer’s disease are comorbid with epilepsy. We have observed elevated seizure propensity in mouse models of these disorders dependent on diet. Specifically, soy-based diets exacerbate audiogenic-induced seizures in juvenile mice. We have also found potential associations between the consumption of soy-based infant formula and seizure incidence, epilepsy comorbidity and autism diagnostic scores in autistic children by retrospective analyses of medical record data. In total, these data suggest that consumption of high levels of soy protein during postnatal development may affect neuronal excitability. Herein, we present our theory regarding the molecular mechanism underlying soy-induced effects on seizure propensity. We hypothesize that soy phytoestrogens interfere with metabotropic glutamate receptor signaling through an estrogen receptor-dependent mechanism, which results in elevated production of key synaptic proteins and decreased seizure threshold.

  20. Neuro-cognitive mechanisms underlying the emotional modulation of word reading

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    A novel neural model for emotional modulation of word reading is proposed. This model has four principal hypotheses: the dominant activation region hypothesis, the emotional modulation hypothesis, the attentional level hypothesis, and the interaction hypothesis. Four lines of research were reviewed to provide evidence for these hypotheses: (1) neuro-cognitive studies on the mechanisms of word reading (i.e., neural networks for reading); (2) studies on the influence of words' emotional valence on word reading; (3) studies of the effect of attention on word reading; and (4) studies on emotional modulation of word reading under different attentional levels.

  1. Influence of Pseudoelasticity on Mechanical Behavior of TiNi Alloy under Dynamic Impact Loading

    Institute of Scientific and Technical Information of China (English)

    Xu Renbo; Cui Lishan; Zheng Yanjun; Chen Hongling

    2007-01-01

    The mechanical behavior of TiNi alloy and Cr12MoV alloy under dynamic impact loading was investigated with a self-made impact testing system. The real-time contact force was measured with a piezoelectric force sensor and digital signal processing system during impact. Equations for predicting instantaneous velocity and displacement were presented. The results showed that the TiNi alloy exhibited a plateau of maximum contact force with increasing impact height. At the plateau stage,TiNi alloy in the parent phase can absorb impact energy and keep the maximum contact force nearly identical due to its pseudoelasticity.

  2. Reliability Analysis of Piezoelectric Truss Structures Under Joint Action of Electric and Mechanical Loading

    Institute of Scientific and Technical Information of China (English)

    YANG Duo-he; AN Wei-guang; ZHU Rong-rong; MIAO Han

    2006-01-01

    Based on the finite element method(FEM) for the dynamical analysis of piezoelectric truss structures, the expressions of safety margins of strength fracture and damage electric field in the structure element are given considering electromechanical coupling effect under the joint action of electric and mechanical load. By importing the stochastic FEM,reliability of piezoelectric truss structures is analyzed by solving for partial derivative in the process of solving dynamical response of structure system with mode-superposition method. The influence of electromechanical coupling effect to reliability index is then analyzed through an example.

  3. Morphofunctional changes and mechanisms of their realization in developing lungs under influence of paracetamol and nimesulid

    Directory of Open Access Journals (Sweden)

    Kharchenko S.V.

    2012-01-01

    Full Text Available Actuality of organs and tissues normality development studying is conditioned on continuous growth of conge-nital abnormalies оn the base of greater drugs distribution. The anomalie s of lungs development unde r influence of paraceta-mol and nimesulide are examined and the possible mechanisms of their appearance are analysed. It is determined that lungs develop more slowly under action of paracetamol than in norm and paracetamol lead to development of bronchial asthma during postnatal period of life. Small in numbers researches of nimesulide influen ce demonstrate changes of lungs histogene-sis, which show up in thei r development deceleration.

  4. A SIMPLE CONSTITUTIVE MODEL FOR FERROELECTRIC CERAMICS UNDER ELECTRICAL/MECHANICAL LOADING

    Institute of Scientific and Technical Information of China (English)

    Yu Li; Yu Shouwen; Feng Xiqiao

    2007-01-01

    A simple phenomenological model is developed for describing the macroscopic constitutive response of ferroelectric materials based on consideration of the fact that domain switching is a progressive evolution process with loading. The volume fraction of domain switching is taken as an internal variable, which is derived from the domain nucleation theory. The proposed theory can simulate the dielectric hysteresis, reversed butterfly hysteresis, nonlinear strain-stress hysteresis, as well as electric displacement-stress relation of ferroelectric materials. Its comparison with experimental results and two other theoretical models reveals that the model presented can well predict the nonlinear hysteresis of ferroelectrics under electrical or mechanical loading.

  5. Finite element simulation for mechanical response of surface mounted solder joints under different temperature cycling

    Institute of Scientific and Technical Information of China (English)

    马鑫; 钱乙余

    2001-01-01

    Nonlinear finite element simulation for mechanical response of surface mounted solder joint under different temperature cycling was carried out. Seven sets of parameters were used in order to evaluate the influence of temperature cycling profile parameters. The results show that temperature cycling history has significant effect on the stress response of the solder joint. Based on the concept of relative damage stress proposed by the authors, it is found that enough high temperature holding time is necessary for designing the temperature cycling profile in accelerated thermal fatigue test.

  6. Acoustic and Vibration Control for an Underwater Structure under Mechanical Excitation

    Directory of Open Access Journals (Sweden)

    Shi-Jian Zhu

    2014-01-01

    Full Text Available Acoustic and vibration control for an underwater structure under mechanical excitation has been investigated by using negative feedback control algorithm. The underwater structure is modeled with cylindrical shells, conical shells, and circular bulkheads, of which the motion equations are built with the variational approach, respectively. Acoustic property is analyzed by the Helmholtz integration formulation with boundary element method. Based on negative feedback control algorithm, a control loop with a coupling use of piezoelectric sensor and actuator is built, and accordingly some numerical examples are carried out on active control of structural vibration and acoustic response. Effects of geometrical and material parameters on acoustic and vibration properties are investigated and discussed.

  7. New onset seizures in the elderly: aetiology and prognosis.

    LENUS (Irish Health Repository)

    Timmons, S

    2012-02-03

    Late onset epilepsy is increasing in incidence. These patients often have significant underlying morbidity. This retrospective study in a tertiary referral centre identified 68 patients aged 65 years or older, with new onset seizures over a four-year period. 81% of patients (n = 55) were followed up at an average of 2.7 years post diagnosis. 38% of patients had evidence of cerebrovascular disease (CT visualised focal infarction, haemorrhage or small vessel ischaemia in 32%, clinical diagnosis with normal CT brain in 6%). No patient was found to have a space-occupying lesion. Of the 55 patients followed up, 45% of these had died at a mean age of 82 years old and 1.9 years post diagnosis (range 12 hours to 5 years). Three patients died as a direct result of seizures (trauma and sepsis). 14 patients died of clearly unrelated causes. Eight patients died from underlying vascular disease or Alzheimer\\'s dementia. Patients who died during follow-up were on average 3.4 years older at the time of diagnosis than survivors (p< 0.05). Patients with atrial fibrillation at the time of diagnosis, had increased mortality (relative risk 2.53; 95% C.I. 1.19 - 5.36), but they were older than those without atrial fibrillation. At the time of follow up, 92% of those taking anti-convulsants were maintained seizure free on anticonvulsant monotherapy.

  8. Computational modeling of dynamic mechanical properties of pure polycrystalline magnesium under high loading strain rates

    Directory of Open Access Journals (Sweden)

    Li Qizhen

    2015-01-01

    Full Text Available Computational simulations were performed to investigate the dynamic mechanical behavior of pure polycrystalline magnesium under different high loading strain rates with the values of 800, 1000, 2000, and 3600 s−1. The Johnson-Cook model was utilized in the simulations based on finite element modeling. The results showed that the simulations provided well-matched predictions of the material behavior such as the strain rate-time history, the stress-strain curve, and the temperature increase. Under high loading strain rates, the tested material experienced linear strain hardening at the early stage of plastic deformation, increased strain hardening at the intermediate plastic deformation region, and decreased strain hardening at the region before fracture. The strain hardening rates for the studied high loading strain rate cases do not vary much with the change of strain rates.

  9. Computational modeling of dynamic mechanical properties of pure polycrystalline magnesium under high loading strain rates

    Science.gov (United States)

    Li, Qizhen

    2015-09-01

    Computational simulations were performed to investigate the dynamic mechanical behavior of pure polycrystalline magnesium under different high loading strain rates with the values of 800, 1000, 2000, and 3600 s-1. The Johnson-Cook model was utilized in the simulations based on finite element modeling. The results showed that the simulations provided well-matched predictions of the material behavior such as the strain rate-time history, the stress-strain curve, and the temperature increase. Under high loading strain rates, the tested material experienced linear strain hardening at the early stage of plastic deformation, increased strain hardening at the intermediate plastic deformation region, and decreased strain hardening at the region before fracture. The strain hardening rates for the studied high loading strain rate cases do not vary much with the change of strain rates.

  10. Reaction Mechanism of Thiophene on Vanadium Oxides under FCC Operating Conditions

    Institute of Scientific and Technical Information of China (English)

    Wang Peng; Zheng Aiguo; Tian Huiping; Long Jun

    2004-01-01

    The reaction mechanism of thiophene on vanadium oxides under FCC operating conditions had been preliminary studied using in-situ FT-IR analysis of thiophene and atmospheric pressure continuous fixed-bed reaction, followed by characterization via pyridine adsorption-temperature programmed desorption method, and FT-IR and XPS spectra. The research had discovered that, under 500C thiophene could undergo the redox reaction with V2O5, while being converted into CO, CO2 as well as SO2 with its conversion rate reaching 41.2%. At the same time the oxidation number of vanadium decreased. The existence of a few Bronsted acid centers on V2O5 could lead to an increase of H2S yield among the products derived from the reaction with thiophene.

  11. A numerical study of crack interactions under thermo-mechanical load using EFGM

    International Nuclear Information System (INIS)

    In this work, element free Galerkin method (EFGM) has been used to obtain the solution of various edge crack problems under thermo-mechanical loads as it provides a versatile technique to model stationary as well as moving crack problems without re-meshing. Standard diffraction criterion has been modified with multiple crack weight technique to characterize the presence of various cracks in the domain of influence of a particular node. The effect of crack inclination has been studied for single as well as two edge cracks, whereas the cracks interaction has been studied for two edge cracks lying on same as well as opposite edges under plane stress conditions. The values of mode-I and mode-II stress intensity factors have been evaluated by the interaction integral approach

  12. Expression and subcellular localization of mechano-growth factor in osteoblasts under mechanical stretch

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    Mechano-growth factor (MGF) is a stretch sensitive factor in myocytes, and it might also be produced by other mechanocytes under mechanical stimulation. In this study, both the mRNA and protein expression of MGF were detected in stretched osteoblasts. Quantitative analysis showed that a cyclic stretching stimulation caused a quick and sharp increase of MGF mRNA and protein expression from a low basal level under no stretch; the mRNA and protein levels respectively peaked in 6 and 12 h to 5 and 5.2 fold over the basal level and returned to normal by 24 h. The subcellular distribution of MGF protein was revealed by immunofluorescence analysis to be restricted to the nucleus. We concluded that cyclic stretching stimulation could induce MGF expression in osteoblasts in a pulsing fashion; and the nuclear distribution of MGF suggested that MGF might act in mechanocytes as an autocrine growth factor.

  13. Numerical Analysis on Failure Modes and Mechanisms of Mine Pillars under Shear Loading

    Directory of Open Access Journals (Sweden)

    Tianhui Ma

    2016-01-01

    Full Text Available Severe damage occurs frequently in mine pillars subjected to shear stresses. The empirical design charts or formulas for mine pillars are not applicable to orebodies under shear. In this paper, the failure process of pillars under shear stresses was investigated by numerical simulations using the rock failure process analysis (RFPA 2D software. The numerical simulation results indicate that the strength of mine pillars and the corresponding failure mode vary with different width-to-height ratios and dip angles. With increasing dip angle, stress concentration first occurs at the intersection between the pillar and the roof, leading to formation of microcracks. Damage gradually develops from the surface to the core of the pillar. The damage process is tracked with acoustic emission monitoring. The study in this paper can provide an effective means for understanding the failure mechanism, planning, and design of mine pillars.

  14. Laws and mechanisms of slope movement due to shallowly buried coal seam mining under ground gully

    Institute of Scientific and Technical Information of China (English)

    FAN Gang-wei; ZHANG Dong-sheng; ZHAI De-yuan; WANG Xu-feng; LU Xin

    2009-01-01

    Based on the results of similar material simulation, the laws of slope movement due to mining under a gully were analyzed. Selected a slope rock as objective, the mechanisms of slope movement influence upon underground mining were proposed, and respective structural models were built by means of numerical modeling and physical simulation. It holds the point that the influence of slope movement on underground mining could be controlled to some extent by appropriate measures. The results indicate that, for gully-ward mining, which mines toward a gully, the slope rock slides horizontally and rotates in layers; for gully-away mining, which mines away from the gully, the slope rock rotates in a reversed polygon. The slope movement associated with mining under a gully is attributed to pre-existing free faces in the ground gully and underground mining-induced free faces.

  15. Mechanism Underlying the Onset of Internal Blue Discoloration in Japanese Radish (Raphanus sativus) Roots.

    Science.gov (United States)

    Teranishi, Katsunori; Masayasu, Nagata; Masuda, Daisuke

    2016-09-01

    The internal blue discoloration observed in Japanese radish (Raphanus sativus L.) roots is a physiological phenomenon caused by storage following harvest at approximately 20 °C and poses a serious problem for farmers. Here, we describe the mechanism underlying the onset of internal blue discoloration of three cultivars: Hukuhomare, SC8-260, and Yuto. Each cultivar was maintained under the same conditions. Additionally, Hukuhomare radish roots were maintained at three different cultivation conditions in a related experiment. The blue discoloration in radish roots was caused by the oxidation of 4-hydroxyglucobrassicin as a result of an increase in oxidative stress involving peroxidase. Thus, the extent of blue discoloration was influenced by the chemical balance involving 4-hydroxyglucobrassicin content, antioxidant capacity, and oxidation activity. PMID:27530819

  16. Plastic mechanism analysis of T-joints in RHS under concentrated force

    Science.gov (United States)

    Zhao, Xiao-Ling; Hancock, Gregory J.

    1991-11-01

    A new plastic mechanism is developed for T-joints in rectangular hollow sections (RHS) under concentrated loads. This model includes the plastic hinges in the web, the membrane force in the flange and the strain hardening of the material. It can predict the yield load, the post-yield response, and the ultimate load of a T-joint under concentrated force. The model developed is compared with the CIDECT model, the Kato model, and the modified Kato model. The yield load, the post-yield response, and the ultimate load determined from the present model are compared with 6 T-joint tests performed by Zhao and Hancock (1991) and 20 T-joint tests performed by Kato and Nishiyama (1979). The ratio (beta) of the T-joints tested varied from 0.291 to 0.890.

  17. Optimal Contract Design for Cooperative Relay Incentive Mechanism under Moral Hazard

    Directory of Open Access Journals (Sweden)

    Nan Zhao

    2015-01-01

    Full Text Available Cooperative relay can effectively improve spectrum efficiency by exploiting the spatial diversity in the wireless networks. However, wireless nodes may acquire different network information with various users’ location and mobility, channels’ conditions, and other factors, which results in asymmetric information between the source and the relay nodes (RNs. In this paper, the relay incentive mechanism between relay nodes and the source is investigated under the asymmetric information. By modelling multiuser cooperative relay as a labour market, a contract model with moral hazard for relay incentive is proposed. To effectively incentivize the potential RNs to participate in cooperative relay, the optimization problems are formulated to maximize the source’s utility while meeting the feasible conditions under both symmetric and asymmetric information scenarios. Numerical simulation results demonstrate the effectiveness of the proposed contract design scheme for cooperative relay.

  18. Experimental Investigation of Mechanical Properties of PVC Polymer under Different Heating and Cooling Conditions

    Directory of Open Access Journals (Sweden)

    Sarkawt Rostam

    2016-01-01

    Full Text Available Due to a widely increasing usage of polymers in various industrial applications, there should be a continuous need in doing research investigations for better understanding of their properties. These applications require the usage of the polymer in different working environments subjecting the material to various temperature ranges. In this paper, an experimental investigation of mechanical properties of polyvinyl chloride (PVC polymer under heating and cooling conditions is presented. For this purpose standard samples are prepared and tested in laboratory using universal material testing apparatus. The samples are tested under different conditions including the room temperature environment, cooling in a refrigerator, and heating at different heating temperatures. It is observed that the strength of the tested samples decreases with the increasing of heating temperature and accordingly the material becomes softer. Meanwhile the cooling environments give a clear increasing to the strength of the material.

  19. Facial Erythema of Rosacea - Aetiology, Different Pathophysiologies and Treatment Options.

    Science.gov (United States)

    Steinhoff, Martin; Schmelz, Martin; Schauber, Jürgen

    2016-06-15

    Rosacea is a common chronic skin condition that displays a broad diversity of clinical manifestations. Although the pathophysiological mechanisms of the four subtypes are not completely elucidated, the key elements often present are augmented immune responses of the innate and adaptive immune system, and neurovascular dysregulation. The most common primary feature of all cutaneous subtypes of rosacea is transient or persistent facial erythema. Perilesional erythema of papules or pustules is based on the sustained vasodilation and plasma extravasation induced by the inflammatory infiltrates. In contrast, transient erythema has rapid kinetics induced by trigger factors independent of papules or pustules. Amongst the current treatments for facial erythema of rosacea, only the selective α2-adrenergic receptor agonist brimonidine 0.33% topical gel (Mirvaso®) is approved. This review aims to discuss the potential causes, different pathophysiologies and current treatment options to address the unmet medical needs of patients with facial erythema of rosacea. PMID:26714888

  20. Size-dependent crystalline fluctuation and growth mechanism of bismuth nanoparticles under electron beam irradiation

    Science.gov (United States)

    Wu, Sujuan; Jiang, Yi; Hu, Lijun; Sun, Jianguo; Wan, Piaopiao; Sun, Lidong

    2016-06-01

    Advanced nanofabrication requires accurate tailoring of various nanostructures with the assistance of electron or ion beam irradiation. However, evolution of the nanostructures under the beam irradiation significantly affects the fabrication process. It is thus of paramount importance to study the evolution behaviors and growth mechanism of the nanostructures. In this study, bismuth nanoparticles were selected to investigate crystalline fluctuation under electron beam irradiation via transmission electron microscopy. The results disclose size-dependent crystalline fluctuation of the nanoparticles. The particles exhibit crystalline and non-crystalline features for sizes of above 15 and below 4 nm, respectively, while a mixture of the two states is observed with sizes in between. The crystalline fluctuation facilitates the growth process of the particles when a crystalline particle is in contact with another non-crystalline one. This is promising for applications in nanofabrication where high quality interfaces are desired between two joining parts.Advanced nanofabrication requires accurate tailoring of various nanostructures with the assistance of electron or ion beam irradiation. However, evolution of the nanostructures under the beam irradiation significantly affects the fabrication process. It is thus of paramount importance to study the evolution behaviors and growth mechanism of the nanostructures. In this study, bismuth nanoparticles were selected to investigate crystalline fluctuation under electron beam irradiation via transmission electron microscopy. The results disclose size-dependent crystalline fluctuation of the nanoparticles. The particles exhibit crystalline and non-crystalline features for sizes of above 15 and below 4 nm, respectively, while a mixture of the two states is observed with sizes in between. The crystalline fluctuation facilitates the growth process of the particles when a crystalline particle is in contact with another non

  1. On the mechanism of gene amplification induced under stress in Escherichia coli.

    Directory of Open Access Journals (Sweden)

    2006-04-01

    Full Text Available Gene amplification is a collection of processes whereby a DNA segment is reiterated to multiple copies per genome. It is important in carcinogenesis and resistance to chemotherapeutic agents, and can underlie adaptive evolution via increased expression of an amplified gene, evolution of new gene functions, and genome evolution. Though first described in the model organism Escherichia coli in the early 1960s, only scant information on the mechanism(s of amplification in this system has been obtained, and many models for mechanism(s were possible. More recently, some gene amplifications in E. coli were shown to be stress-inducible and to confer a selective advantage to cells under stress (adaptive amplifications, potentially accelerating evolution specifically when cells are poorly adapted to their environment. We focus on stress-induced amplification in E. coli and report several findings that indicate a novel molecular mechanism, and we suggest that most amplifications might be stress-induced, not spontaneous. First, as often hypothesized, but not shown previously, certain proteins used for DNA double-strand-break repair and homologous recombination are required for amplification. Second, in contrast with previous models in which homologous recombination between repeated sequences caused duplications that lead to amplification, the amplified DNAs are present in situ as tandem, direct repeats of 7-32 kilobases bordered by only 4 to 15 base pairs of G-rich homology, indicating an initial non-homologous recombination event. Sequences at the rearrangement junctions suggest nonhomologous recombination mechanisms that occur via template switching during DNA replication, but unlike previously described template switching events, these must occur over long distances. Third, we provide evidence that 3'-single-strand DNA ends are intermediates in the process, supporting a template-switching mechanism. Fourth, we provide evidence that lagging

  2. On the tension necking of copper single crystal specimen under slip deformation mechanism

    Institute of Scientific and Technical Information of China (English)

    ZHANG KeShi; GENG XiaoLiang; LI JinShan; HU Rui

    2007-01-01

    The tension necking of FCC copper single crystal specimen with a square cross section was analyzed under the slip deformation mechanism. The actual clamp manner of the specimen was modeled by setting correlative boundary condition,and the small angle deflection between tension loading axis and crystallography axis [100] was taken into account. The finite deformation numerical analysis of three-dimensional necking deformation for the specimen was performed by applying crystal plasticity theory associated with a numerical algorithm suggested by the first author. According to the comparison with experimental observation, the fact was confirmed that the numerical results could describe the loading elongation curve of the copper single crystal specimen under large strain tension reasonably,and the method could be used to investigate the necking characteristic in neck shape and the effect due to the small angle deflection. Further, the investigation into the influence of specimen cross-section shape on necking was also performed;the results on mechanical response and neck profile evolution obtained through modeling of cylindrical specimen were compared with those obtained with square cross-section specimen.

  3. On the tension necking of copper single crystal specimen under slip deformation mechanism

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The tension necking of FCC copper single crystal specimen with a square cross section was analyzed under the slip deformation mechanism. The actual clamp manner of the specimen was modeled by setting correlative boundary condition,and the small angle deflection between tension loading axis and crystallography axis [100] was taken into account. The finite deformation numerical analysis of three-dimensional necking deformation for the specimen was performed by apply-ing crystal plasticity theory associated with a numerical algorithm suggested by the first author. According to the comparison with experimental observation,the fact was confirmed that the numerical results could describe the loading elongation curve of the copper single crystal specimen under large strain tension reasonably,and the method could be used to investigate the necking characteristic in neck shape and the effect due to the small angle deflection. Further,the investigation into the influence of specimen cross-section shape on necking was also performed;the results on mechanical response and neck profile evolution obtained through modeling of cylindrical specimen were compared with those obtained with square cross-section specimen.

  4. Mechanical, piezoelectric and some thermal properties of (B3) BP under pressure

    Institute of Scientific and Technical Information of China (English)

    S.DAOUD; N.BIOUD; N.LEBGAA

    2014-01-01

    Some compounds of group III-V semiconductor materials exhibit very good piezoelectric, mechanical, and thermal properties and their use in surface acoustic wave (SAW) devices operating specially at GHz frequencies. These materials have been appreciated for a long time due to their high acoustic velocities, which are important parameters for active microelectromechanical systems (MEMS) devices. For this object, first-principles calculations of the anisotropy and the hydrostatic pressure effect on the mechanical, piezoelectric and some thermal properties of the (B3) boron phosphide are presented, using the density functional perturbation theory (DFPT). The independent elastic and compliance constants, the Reuss modulus, Voigt modulus, and the shear modulus, the Kleinman parameter, the Cauchy and Born coefficients, the elastic modulus, and the Poisson ratio for directions within the important crystallographic planes of this compound under pressure are obtained. The direct and converse piezoelectric coefficients, the longitudinal, transverse, and average sound velocity, the Debye temperature, and the Debye frequency of (B3) boron phosphide under pressure are also presented and compared with available experimental and theoretical data of the literature.

  5. Separation Mechanism of Primary Silicon from Hypereutectic Al-Si Melts Under Alternating Electromagnetic Fields

    Science.gov (United States)

    Xue, Haiyang; Lv, Guoqiang; Ma, Wenhui; Chen, Daotong; Yu, Jie

    2015-07-01

    Solar grade silicon (SOG-Si) and hypereutectic Al-Si alloys with low silicon (silicon composition below 25 pct) can be successfully obtained by separation of hypereutectic Al-Si alloy with high silicon (silicon composition above 30 pct) under an alternating electromagnetic field after post-processing. To explore the separation mechanism in detail, experiments were conducted in this study using a high-frequency induction furnace with different pulling conditions of the crucible which is loaded with Al-45 wt pct Si melt. Results demonstrate that the separation of hypereutectic Al-Si alloy is feasible through either a pull-up or drop-down process. The height of each separation interface between the compact and sparse parts of the primary silicon decrease as the pull-up distance rose. When the pulling rate is very low, resultant morphologies of compact primary silicon are rounded and polygonal, allowing for more effective separation of the primary silicon. A novel physical model is presented here based on the experimental results and simulation. The model can be used to effectively describe the separation mechanism of primary silicon from hypereutectic Al-Si melts under alternating electromagnetic fields.

  6. Using technology to explore social networks and mechanisms underlying peer effects in classrooms.

    Science.gov (United States)

    Guryan, Jonathan; Jacob, Brian; Klopfer, Eric; Groff, Jennifer

    2008-03-01

    Peer interactions among children have long interested social scientists. Identifying causal peer effects is difficult, and a number of studies have used random assignment to produce evidence that peers affect each other's outcomes. This focus by sociologists and economists on whether peers affect each other has not been matched by direct evidence on how these effects operate. The authors argue that one reason for the small number of studies in sociology and economics on the mechanisms underlying peer effects is the difficulty of collecting data on microinteractions. They argue technology reduces data collection costs relative to direct observation and allows for realistic school activities with randomly assigned peers. The authors describe a novel strategy for collecting data on peer interactions and discuss how this approach might shed light on mechanisms underlying peer influence. The centerpiece of this strategy is the use of handheld computers by middle and high school students as part of interactive math and science lessons called the Discussion Game. The handhelds collect data on interactions between students and track how students' answers evolve as they interact with different peers.

  7. Phosphoproteomics-based modeling defines the regulatory mechanism underlying aberrant EGFR signaling.

    Directory of Open Access Journals (Sweden)

    Shinya Tasaki

    Full Text Available BACKGROUND: Mutation of the epidermal growth factor receptor (EGFR results in a discordant cell signaling, leading to the development of various diseases. However, the mechanism underlying the alteration of downstream signaling due to such mutation has not yet been completely understood at the system level. Here, we report a phosphoproteomics-based methodology for characterizing the regulatory mechanism underlying aberrant EGFR signaling using computational network modeling. METHODOLOGY/PRINCIPAL FINDINGS: Our phosphoproteomic analysis of the mutation at tyrosine 992 (Y992, one of the multifunctional docking sites of EGFR, revealed network-wide effects of the mutation on EGF signaling in a time-resolved manner. Computational modeling based on the temporal activation profiles enabled us to not only rediscover already-known protein interactions with Y992 and internalization property of mutated EGFR but also further gain model-driven insights into the effect of cellular content and the regulation of EGFR degradation. Our kinetic model also suggested critical reactions facilitating the reconstruction of the diverse effects of the mutation on phosphoproteome dynamics. CONCLUSIONS/SIGNIFICANCE: Our integrative approach provided a mechanistic description of the disorders of mutated EGFR signaling networks, which could facilitate the development of a systematic strategy toward controlling disease-related cell signaling.

  8. Prolonged secretion of cortisol as a possible mechanism underlying stress and depressive behaviour.

    Science.gov (United States)

    Qin, Dong-Dong; Rizak, Joshua; Feng, Xiao-Li; Yang, Shang-Chuan; Lü, Long-Bao; Pan, Lei; Yin, Yong; Hu, Xin-Tian

    2016-01-01

    Stress is associated with the onset of depressive episodes, and cortisol hypersecretion is considered a biological risk factor of depression. However, the possible mechanisms underlying stress, cortisol and depressive behaviours are inconsistent in the literature. This study examined the interrelationships among stress, cortisol and observed depressive behaviours in female rhesus macaques for the first time and explored the possible mechanism underlying stress and depressive behaviour. Female monkeys were video-recorded, and the frequencies of life events and the duration of huddling were analysed to measure stress and depressive behaviour. Hair samples were used to measure chronic cortisol levels, and the interactions between stress and cortisol in the development of depressive behaviour were further evaluated. Significant correlations were found between stress and depressive behaviour measures and between cortisol levels and depressive behaviour. Stress was positively correlated with cortisol levels, and these two factors interacted with each other to predict the monkeys' depressive behaviours. This finding extends the current understanding of stress/cortisol interactions in depression, especially pertaining to females. PMID:27443987

  9. Looking back: developments in our understanding of the occurrence, aetiology and prognosis of chronic pain 1954-2004.

    Science.gov (United States)

    Macfarlane, G J

    2005-12-01

    This article summarizes the work of the Arthritis Research Campaign Epidemiology Unit in the field of pain and soft tissue rheumatism during the 50 years 1954-2004. It reviews the information gathered on the occurrence of symptoms and its causes, which began with Kellgren and Lawrence's pioneering work during the 1950s in the coal fields and general population of Leigh, Greater Manchester. They studied the roles of posture, mechanical load and the physical environment (dampness) on back pain. This was followed by the Calderdale study in the 1980s examining the prevalence of disability and its causes in the population, which demonstrated the important role of regional pain in causing disability. More recent studies in the 1990s and at the beginning of the 21st century have allowed us to define the relative roles of mechanical (load) factors, individual (psychological) factors and the social environment, and the biological mechanisms by which they may result in symptoms. The further challenge over the coming decade is to use our knowledge of the aetiology and influences on outcome to design management strategies which demonstrate improved outcomes for patients.

  10. The aetiology of vaginal symptoms in rural Haiti.

    Science.gov (United States)

    Bristow, Claire C; Desgrottes, Tania; Cutler, Lauren; Cutler, David; Devarajan, Karthika; Ocheretina, Oksana; Pape, Jean William; Klausner, Jeffrey D

    2014-08-01

    Vaginal symptoms are a common chief complaint amongst women visiting outpatient clinics in rural Haiti. A systematic sample of 206 consecutive women over age 18 with gynaecological symptoms underwent gynaecologic examination and laboratory testing for chlamydia, gonorrhoea, syphilis, HIV infection, trichomoniasis, candidiasis, and bacterial vaginosis. Among 206 women, 174 (84%) presented with vaginal discharge, 165 (80%) with vaginal itching, 123 (60%) with vaginal pain or dysuria, and 18 (9%) with non-traumatic vaginal sores or boils. Laboratory results were positive forChlamydia trachomatisin 5.4% (11/203), syphilis in 3.5% (7/202), HIV in 1.0% (2/200), andNeisseria gonorrhoeaein 1.0% (2/203). Among those that had microscopy, hyphae suggestive of candidiasis were visualized in 2.2% (1/45) and no cases of trichomoniasis were diagnosed 0% (0/45). Bacterial vaginosis was diagnosed in 28.3% (13/46). The prevalence of chlamydia was 4.9 (95% CI: 1.3-17.7) times greater among those 25 years of age and under (10.8%) than those older (2.3%). Chlamydia and bacterial vaginosis were the most common sexually transmitted infection and vaginal condition, respectively, in this study of rural Haitian adult women. The higher risk of chlamydia in younger women suggests education and screening programmes in young women should be considered. PMID:24352116

  11. Sleep disturbances in menopausal women: Aetiology and practical aspects.

    Science.gov (United States)

    Bruyneel, Marie

    2015-07-01

    Sleep deteriorates with age. The menopause is often a turning point for women's sleep, as complaints of insomnia increase significantly thereafter. Insomnia can occur as a secondary disorder to hot flashes, mood disorders, medical conditions, psychosocial factors, underlying intrinsic sleep disorders, such as obstructive sleep apnoea (OSA) or restless legs syndrome (RLS), or it can be a primary disorder. Since unrecognized OSA can have dramatic health-related consequences, menopausal women complaining of persisting sleep disturbances suggesting primary insomnia or intrinsic sleep disorders should be referred to a sleep specialist for a comprehensive sleep assessment. Patients suffering from primary insomnia will be preferentially treated with non-benzodiazepine hypnotics or melatonin, or with cognitive behavioural therapy. Insomnia related to vasomotor symptoms can be improved with hormone replacement therapy. Gabapentin and isoflavones have also shown efficacy in small series but their precise role has yet to be established. In patients suffering from OSA, non-pharmacological therapy will be applied: continuous positive airway pressure or an oral appliance, according to the severity of the disorder. In the case of RLS, triggering factors must be avoided; dopaminergic agonists are the first-line treatment for moderate to severe disease. In conclusion, persisting sleep complaints should be addressed in menopausal women, in order to correctly diagnose the specific causal disorder and to prescribe treatments that have been shown to improve sleep quality, quality of life and long-term health status. PMID:26002789

  12. INFECTIVE ENDOCARDITIS: AETIOLOGY, CLINICAL FEATURES, PRINCIPLES OF TREATMENT AND PREVENTION

    Directory of Open Access Journals (Sweden)

    Coralia Bleotu

    2012-03-01

    Full Text Available Infective endocarditis (IE is characterized by pathogen colonization and endocardium invasion, causing the formation of vegetations - amorphous aggregates, composed of platelets, fibrin, microorganisms and inflammatory cells. IE microbiological aspects are variable from country to country, reason for which, the purpose of this review was to integrate some original data concerning the etiology and antimicrobial resistance markers in microbial strains isolated from infections occurred in patients with underlying cardiovascular diseases in the general microbiological picture IE (i.e. diagnosis, etiology and treatment. In our hospital, the etiology of positive blood cultures and prosthetic devices associated infections occurred in patients with cardiovascular diseases is dominated by Gram-positive cocci, especially S. aureus and coagulase-negative staphylococci (CNS, followed by Gram-negative fermentative and non-fermentative bacilli. The major concerns regarding the resistance markers of the isolated strains are the methicillin and macrolides lincosamides streptogramines resistance exceeding 50%, both in S. aureus and CNS and the aminoglycosides high level resistance (30% in E. faecium strains.

  13. The aetiology of vaginal symptoms in rural Haiti.

    Science.gov (United States)

    Bristow, Claire C; Desgrottes, Tania; Cutler, Lauren; Cutler, David; Devarajan, Karthika; Ocheretina, Oksana; Pape, Jean William; Klausner, Jeffrey D

    2014-08-01

    Vaginal symptoms are a common chief complaint amongst women visiting outpatient clinics in rural Haiti. A systematic sample of 206 consecutive women over age 18 with gynaecological symptoms underwent gynaecologic examination and laboratory testing for chlamydia, gonorrhoea, syphilis, HIV infection, trichomoniasis, candidiasis, and bacterial vaginosis. Among 206 women, 174 (84%) presented with vaginal discharge, 165 (80%) with vaginal itching, 123 (60%) with vaginal pain or dysuria, and 18 (9%) with non-traumatic vaginal sores or boils. Laboratory results were positive forChlamydia trachomatisin 5.4% (11/203), syphilis in 3.5% (7/202), HIV in 1.0% (2/200), andNeisseria gonorrhoeaein 1.0% (2/203). Among those that had microscopy, hyphae suggestive of candidiasis were visualized in 2.2% (1/45) and no cases of trichomoniasis were diagnosed 0% (0/45). Bacterial vaginosis was diagnosed in 28.3% (13/46). The prevalence of chlamydia was 4.9 (95% CI: 1.3-17.7) times greater among those 25 years of age and under (10.8%) than those older (2.3%). Chlamydia and bacterial vaginosis were the most common sexually transmitted infection and vaginal condition, respectively, in this study of rural Haitian adult women. The higher risk of chlamydia in younger women suggests education and screening programmes in young women should be considered.

  14. Effects of strain rates on mechanical properties of limestone under high temperature

    Institute of Scientific and Technical Information of China (English)

    Tang Furong; Mao Xianbiao; Zhang Lianying; Yin Huiguang; Li Yan

    2011-01-01

    The experimental tests for limestone specimens at 700 ℃ in uniaxial compression were carried out to investigate the mechanical effects of loading rates on limestone by using a MTS810 rock mechanics servocontrolled testing system considering the loading rate as a variable.The mechanical properties of limestone such as the stress-strain curve,variable characteristics of peak strength and the modulus of elasticity of limestone were studied under the strain rates ranging from 1.1 × 10-s to 1.1 × 10-1 s-1.(1) Sharp decreases were shown for the peak strength and elastic modulus of limestone from 1.1 × 10-5 to 1.1 × 10 4 s-1 at 700 C as well as a downward trend was shown from 1.1 × 10 4 to 1.1 × 10-1 s-1with the rise of the strain rate.(2) The peak strain increased from 1.1 × 10-5 to 1.1 × 10-4 s-1,however,there was no obvious changes shown for the peak strain of limestone from 1.1 × 10-4 to 1.1 × 10-1 s-1.These results can nrovide valuable references for the rock blasting effect and design of mine.

  15. Change of plans: an evaluation of the effectiveness and underlying mechanisms of successful talent transfer.

    Science.gov (United States)

    Collins, Rosie; Collins, Dave; MacNamara, Aine; Jones, Martin Ian

    2014-01-01

    Talent transfer (TT) is a recently formalised process used to identify and develop talented athletes by selecting individuals who have already succeeded in one sport and transferring them to another. Despite the increasing popularity of TT amongst national organisations and sport governing body professionals, however, there is little empirical evidence as to its efficacy or how it may be most efficiently employed. Accordingly, this investigation was designed to gain a deeper understanding of the effectiveness and underlying mechanisms of TT, achieved through a two-part study. Stage 1 provided a quantitative analysis of the incidence and distribution or, in this respect, epidemiology of TT, finding the most popular transfer to be sprinting to bobsleigh, with an average transfer age of 19 years. Stage 2 scrutinised the TT process and explored the specific cases revealed in stage 1 by examining the perceptions of four sport science support specialists who had worked in TT settings, finding several emergent themes which, they felt, could explain the TT processes. The most prominent theme was the psychosocial mechanism of TT, an aspect currently missing from TT initiatives, suggesting that current TT systems are poorly structured and should redress their approach to develop a more integrated scheme that encompasses all potential mechanisms of transfer. PMID:24814474

  16. Nuclear power for greenhouse gas mitigation under the Kyoto protocol: The Clean Development Mechanism (CDM)

    International Nuclear Information System (INIS)

    At the 43rd regular session of the IAEA General Conference, Member States requested the IAEA to help countries in assessing nuclear power's role in light of global environmental challenges and energy needs. Such assistance should include support for implementing national case studies, and facilitating access to relevant information about nuclear power's role in achieving sustainable development in developing countries and in mitigating GHG emissions. The dissemination of information on CDM is of particular importance to developing countries, so as to enable Member States interested in the mechanism to take an active and informed role in the debate regarding the Kyoto Protocol and eligible CDM technologies. Therefore, the Secretariat organized a series of information seminars, workshops and training courses for Member States on the Kyoto Protocol, the Clean Development Mechanism, Joint Implementation and Emissions Trading with particular emphasis on the potential role of nuclear power for GHG mitigation. On request, the Secretariat also provided training and assistance to several Member States in the preparation of national case studies that explore the potential role of nuclear power as a CDM technology. These case studies will be presented by the respective national study teams during this side event at the 44th IAEA General Conference. Within the general criteria included in the Kyoto Protocol, the decision on which technologies are eligible for GHG mitigation under the flexibility mechanisms is a sovereign decision of each country

  17. Axial level-dependent molecular and cellular mechanisms underlying the genesis of the embryonic neural plate.

    Science.gov (United States)

    Kondoh, Hisato; Takada, Shinji; Takemoto, Tatsuya

    2016-06-01

    The transcription factor gene Sox2, centrally involved in neural primordial regulation, is activated by many enhancers. During the early stages of embryonic development, Sox2 is regulated by the enhancers N2 and N1 in the anterior neural plate (ANP) and posterior neural plate (PNP), respectively. This differential use of the enhancers reflects distinct regulatory mechanisms underlying the genesis of ANP and PNP. The ANP develops directly from the epiblast, triggered by nodal signal inhibition, and via the combined action of TFs SOX2, OTX2, POU3F1, and ZIC2, which promotes the the ANP development and inhibits other cell lineages. In contrast, the PNP is derived from neuromesodermal bipotential axial stem cells that develop into the neural plate when Sox2 is activated by the N1 enhancer, whereas they develop into the paraxial mesoderm when the N1 enhancer is repressed by the action of TBX6. The axial stem cells are maintained by the activity of WNT3a and T (Brachyury). However, at axial levels more anterior to the 8th somites (cervical levels), the development of both the neural plate and somite proceeds in the absence of WNT3a, T, or TBX6. These observations indicate that distinct molecular and cellular mechanisms determine neural plate genesis based on the axial level, and contradict the classical concept of the term "neural induction," which assumes a pan-neural plate mechanism. PMID:27279156

  18. Axial level-dependent molecular and cellular mechanisms underlying the genesis of the embryonic neural plate.

    Science.gov (United States)

    Kondoh, Hisato; Takada, Shinji; Takemoto, Tatsuya

    2016-06-01

    The transcription factor gene Sox2, centrally involved in neural primordial regulation, is activated by many enhancers. During the early stages of embryonic development, Sox2 is regulated by the enhancers N2 and N1 in the anterior neural plate (ANP) and posterior neural plate (PNP), respectively. This differential use of the enhancers reflects distinct regulatory mechanisms underlying the genesis of ANP and PNP. The ANP develops directly from the epiblast, triggered by nodal signal inhibition, and via the combined action of TFs SOX2, OTX2, POU3F1, and ZIC2, which promotes the the ANP development and inhibits other cell lineages. In contrast, the PNP is derived from neuromesodermal bipotential axial stem cells that develop into the neural plate when Sox2 is activated by the N1 enhancer, whereas they develop into the paraxial mesoderm when the N1 enhancer is repressed by the action of TBX6. The axial stem cells are maintained by the activity of WNT3a and T (Brachyury). However, at axial levels more anterior to the 8th somites (cervical levels), the development of both the neural plate and somite proceeds in the absence of WNT3a, T, or TBX6. These observations indicate that distinct molecular and cellular mechanisms determine neural plate genesis based on the axial level, and contradict the classical concept of the term "neural induction," which assumes a pan-neural plate mechanism.

  19. Neural mechanisms underlying transcranial direct current stimulation in aphasia: A feasibility study.

    Directory of Open Access Journals (Sweden)

    Lena eUlm

    2015-10-01

    Full Text Available Little is known about the neural mechanisms by which transcranial direct current stimulation (tDCS impacts on language processing in post-stroke aphasia. This was addressed in a proof-of-principle study that explored the effects of tDCS application in aphasia during simultaneous functional magnetic resonance imaging (fMRI. We employed a single subject, cross-over, sham-tDCS controlled design and the stimulation was administered to an individualized perilesional stimulation site that was identified by a baseline fMRI scan and a picture naming task. Peak activity during the baseline scan was located in the spared left inferior frontal gyrus (IFG and this area was stimulated during a subsequent cross-over phase. tDCS was successfully administered to the target region and anodal- vs. sham-tDCS resulted in selectively increased activity at the stimulation site. Our results thus demonstrate that it is feasible to precisely target an individualized stimulation site in aphasia patients during simultaneous fMRI which allows assessing the neural mechanisms underlying tDCS application. The functional imaging results of this case report highlight one possible mechanism that may have contributed to beneficial behavioural stimulation effects in previous clinical tDCS trials in aphasia. In the future, this approach will allow identifying distinct patterns of stimulation effects on neural processing in larger cohorts of patients. This may ultimately yield information about the variability of tDCS-effects on brain functions in aphasia.

  20. Genetic algorithm based optimal control of smart composite shell structures under mechanical loading and thermal gradient

    International Nuclear Information System (INIS)

    In the present paper an improved genetic algorithm (GA) based linear quadratic regulator (LQR) control scheme has been proposed for active vibration control of smart fiber reinforced polymer (FRP) composite shell structures under combined mechanical and thermal loading. A layered shell finite element formulation has been done to obtain the electro-thermo-mechanical response of fiber reinforced polymer (FRP) composite shell structures bonded with piezoelectric patches. Based on the responses obtained from finite element analysis, a real coded GA based improved LQR control scheme has been incorporated, which maximizes the closed loop damping while keeping the actuator voltages within limit. It has been observed that the developed FE code can be used for determination of the accurate response of smart FRP shell structures for the simulation of active vibration control of such structures. The proposed GA based LQR control scheme could control both dynamic oscillation due to mechanical load as well as the static displacement due to a thermal gradient, which was not possible with conventional LQR control scheme

  1. Mitochondrial Ca2+ overload underlies Abeta oligomers neurotoxicity providing an unexpected mechanism of neuroprotection by NSAIDs.

    Directory of Open Access Journals (Sweden)

    Sara Sanz-Blasco

    Full Text Available Dysregulation of intracellular Ca(2+ homeostasis may underlie amyloid beta peptide (Abeta toxicity in Alzheimer's Disease (AD but the mechanism is unknown. In search for this mechanism we found that Abeta(1-42 oligomers, the assembly state correlating best with cognitive decline in AD, but not Abeta fibrils, induce a massive entry of Ca(2+ in neurons and promote mitochondrial Ca(2+ overload as shown by bioluminescence imaging of targeted aequorin in individual neurons. Abeta oligomers induce also mitochondrial permeability transition, cytochrome c release, apoptosis and cell death. Mitochondrial depolarization prevents mitochondrial Ca(2+ overload, cytochrome c release and cell death. In addition, we found that a series of non-steroidal anti-inflammatory drugs (NSAIDs including salicylate, sulindac sulfide, indomethacin, ibuprofen and R-flurbiprofen depolarize mitochondria and inhibit mitochondrial Ca(2+ overload, cytochrome c release and cell death induced by Abeta oligomers. Our results indicate that i mitochondrial Ca(2+ overload underlies the neurotoxicity induced by Abeta oligomers and ii inhibition of mitochondrial Ca(2+ overload provides a novel mechanism of neuroprotection by NSAIDs against Abeta oligomers and AD.

  2. Fatigue degradation and failure of rotating composite structures - Materials characterisation and underlying mechanisms

    Energy Technology Data Exchange (ETDEWEB)

    Gamstedt, E.K.; Andersen, S.I.

    2001-03-01

    The present review concerns rotating composite structures, in which fatigue degradation is of key concern for in-service failure. Such applications are for instance rotor blades in wind turbines, helicopter rotor blades, flywheels for energy storage, marine and aeronautical propellers, and rolls for paper machines. The purpose is to identify areas where impending efforts should be made to make better use of composite materials in these applications. In order to obtain better design methodologies, which would allow more reliable and slender structures, improved test methods are necessary. Furthermore, the relation between structural, component and specimen test results should be better understood than what is presently the case. Improved predictive methods rely on a better understanding of the underlying damage mechanisms. With mechanism-based models, the component substructure or even the material microstructure could be optimised for best possible fatigue resistance. These issues are addressed in the present report, with special emphasis on test methods, and scaling from damage mechanisms to relevant material properties. (au)

  3. Investigating the time-dependent behaviour of Boom clay under thermo-mechanical loading

    CERN Document Server

    Cui, Yu-Jun; Tang, Anh-Minh; Delage, Pierre; Li, Xiang-Ling; 10.1680/geot.2009.59.4.319

    2009-01-01

    Among the various laboratory studies to investigate the Thermo-Hydro-Mechanical (THM) behaviour of Boom clay, relatively few were devoted to the time dependent behaviour, limiting any relevant analysis of the long-term behaviour of the disposal facility. The present work aims at investigating the time-dependent behaviour of Boom clay under both thermal and mechanical loading. High-pressure triaxial tests at controlled temperatures were carried out for this purpose. The tests started with constant-rate thermal and/or mechanical consolidation and ended with isobar heating and/or isothermal compression at a constant stress rate or by step loading. Significant effects of temperature as well as of compression and heating rates were observed on the volume change behaviour. After being loaded to a stress lower than the pre-consolidation pressure (5 MPa) at a low temperature of 25\\degree C and at a rate lower than 0.2 kPa/min, the sample volume changes seemed to be quite small, suggesting a full dissipation of pore w...

  4. Role of soluble guanylate cyclase in the molecular mechanism underlying the physiological effects of nitric oxide.

    Science.gov (United States)

    Severina, I S

    1998-07-01

    In this review the molecular mechanisms underlying the antihypertensive and antiaggregatory actions of nitric oxide (NO) are discussed. It has been shown that these effects are directly connected with the activation of soluble guanylate cyclase and the accumulation of cyclic 3;,5;-guanosine monophosphate (cGMP). The mechanism of guanylate cyclase activation by NO is analyzed, especially the role and biological significance of the nitrosyl--heme complex formed as a result of interaction of guanylate cyclase heme with NO and the role of sulfhydryl groups of the enzyme in this process. Using new approaches for studying the antihypertensive and antiaggregatory actions of nitric oxide in combination with the newly obtained data on the regulatory role of guanylate cyclase in the platelet aggregation process, the most important results were obtained regarding the molecular bases providing for a directed search for and creation of new effective antihypertensive and antiaggregatory preparations. In studying the molecular mechanism for directed activation of soluble guanylate cyclase by new NO donors, a series of hitherto unknown enzyme activators generating NO and involved in the regulation of hemostasis and vascular tone were revealed. PMID:9721331

  5. Neural Mechanisms Underlying Perilesional Transcranial Direct Current Stimulation in Aphasia: A Feasibility Study

    Science.gov (United States)

    Ulm, Lena; McMahon, Katie; Copland, David; de Zubicaray, Greig I.; Meinzer, Marcus

    2015-01-01

    Little is known about the neural mechanisms by which transcranial direct current stimulation (tDCS) impacts on language processing in post-stroke aphasia. This was addressed in a proof-of-principle study that explored the effects of tDCS application in aphasia during simultaneous functional magnetic resonance imaging (fMRI). We employed a single subject, cross-over, sham-tDCS controlled design, and the stimulation was administered to an individualized perilesional stimulation site that was identified by a baseline fMRI scan and a picture naming task. Peak activity during the baseline scan was located in the spared left inferior frontal gyrus and this area was stimulated during a subsequent cross-over phase. tDCS was successfully administered to the target region and anodal- vs. sham-tDCS resulted in selectively increased activity at the stimulation site. Our results thus demonstrate that it is feasible to precisely target an individualized stimulation site in aphasia patients during simultaneous fMRI, which allows assessing the neural mechanisms underlying tDCS application. The functional imaging results of this case report highlight one possible mechanism that may have contributed to beneficial behavioral stimulation effects in previous clinical tDCS trials in aphasia. In the future, this approach will allow identifying distinct patterns of stimulation effects on neural processing in larger cohorts of patients. This may ultimately yield information about the variability of tDCS effects on brain functions in aphasia. PMID:26500522

  6. A novel platform for in situ investigation of cells and tissues under mechanical strain

    Science.gov (United States)

    Ahmed, Wylie W.; Kural, Mehmet H.; Saif, Taher A.

    2010-01-01

    The mechanical micro-environment influences cellular responses such as migration, proliferation, differentiation, and apoptosis. Cells are subjected to mechanical stretching in vivo, e.g., epithelial cells during embryogenesis. Current methodologies do not allow high resolution in situ observation of cells and tissues under applied strain, which may reveal intracellular dynamics and the origin of cell mechanosensitivity. We have developed a novel polydimethylsiloxane (PDMS) substrate capable of applying tensile and compressive strain (up to 45%) to cells and tissues while allowing in situ observation with high resolution optics. The strain field of the substrate was characterized experimentally using digital image correlation (DIC) and the deformation was modeled with finite element method (FEM) using a Mooney-Rivlin hyperelastic constitutive relation. The substrate strain was found to be uniform for greater than 95% of the substrate area. As a demonstration of our system, we applied mechanical strain to single fibroblasts transfected with GFP-Actin and whole transgenic Drosophila embryos expressing GFP in all neurons during live imaging. We report three observations of biological responses due to applied strain: (1) dynamic rotation of intact actin stress fibers in fibroblasts; (2) lamellipodia activity and actin polymerization in fibroblasts; (3) active axonal contraction in Drosophila embryo motor neurons. Our novel platform may serve as an important tool in studying the mechanoresponse of cells and tissues including whole embryos. PMID:20188869

  7. Towards identifying the mechanisms underlying field-aligned edge-loss of HHFW power on NSTX

    Energy Technology Data Exchange (ETDEWEB)

    Perkins, R. J. [Princeton Plasma Physics Laboratory (PPPL); Ahn, Joonwook [ORNL; Bell, R. E. [Princeton Plasma Physics Laboratory (PPPL); Bertelli, Nicola [Princeton Plasma Physics Laboratory (PPPL); Diallo, A. [Princeton Plasma Physics Laboratory (PPPL); Gerhardt, S. [Princeton Plasma Physics Laboratory (PPPL); Gray, T. K. [Oak Ridge National Laboratory (ORNL); Green, David L [ORNL; Jaeger, E. F. [XCEL; Hosea, J. [Princeton Plasma Physics Laboratory (PPPL); Jaworski, M. A. [Princeton Plasma Physics Laboratory (PPPL); LeBlanc, B [Princeton Plasma Physics Laboratory (PPPL); Kramer, G. [Princeton Plasma Physics Laboratory (PPPL); McLean, Adam G [ORNL; Maingi, Rajesh [ORNL; Phillips, C. K. [Princeton Plasma Physics Laboratory (PPPL); Podesta, M. [Princeton Plasma Physics Laboratory (PPPL); Ryan, Philip Michael [ORNL; Sabbagh, S. A. [Columbia University; Scotti, F. [Princeton Plasma Physics Laboratory (PPPL); Taylor, G. [Princeton Plasma Physics Laboratory (PPPL); Wilson, J. R. [Princeton Plasma Physics Laboratory (PPPL)

    2013-01-01

    Fast-wave heating will be a major heating scheme on ITER, as it can heat ions directly and is relatively unaffected by the large machine size unlike neutral beams. However, fast-wave interactions with the plasma edge can lead to deleterious effects such as, in the case of the high-harmonic fast-wave (HHFW) system on NSTX, large losses of fast-wave power in the scrape off layer (SOL) under certain conditions. In such scenarios, a large fraction of the lost HHFW power is deposited on the upper and lower divertors in bright spiral shapes. The responsible mechanism(s) has not yet been identified but may include fast-wave propagation in the scrape off layer, parametric decay instability, and RF currents driven by the antenna reactive fields. Understanding and mitigating these losses is important not only for improving the heating and current-drive on NSTX-Upgrade but also for understanding fast-wave propagation across the SOL in any fast-wave system. This talk summarizes experimental results demonstrating that the flow of lost HHFW power to the divertor regions largely follows the open SOL magnetic field lines. This lost power flux is relatively large close to both the antenna and the last closed flux surface with a reduced level in between, so the loss mechanism cannot be localized to the antenna. At the same time, significant losses also occur along field lines connected to the inboard edge of the bottom antenna plate. The power lost within the spirals is roughly estimated, showing that these field-aligned losses to the divertor are significant but may not account for the total HHFW loss. To elucidate the role of the onset layer for perpendicular fast-wave propagation with regards to fast-wave propagation in the SOL, a cylindrical cold-plasma model is being developed. This model, in addition to advanced RF codes such as TORIC and AORSA, is aimed at identifying the underlying mechanism(s) behind these SOL losses, to minimize their effects in NSTX-U, and to predict

  8. Mechanical characterisation of porcine rectus sheath under uniaxial and biaxial tension.

    LENUS (Irish Health Repository)

    Lyons, Mathew

    2014-06-03

    Incisional hernia development is a significant complication after laparoscopic abdominal surgery. Intra-abdominal pressure (IAP) is known to initiate the extrusion of intestines through the abdominal wall, but there is limited data on the mechanics of IAP generation and the structural properties of rectus sheath. This paper presents an explanation of the mechanics of IAP development, a study of the uniaxial and biaxial tensile properties of porcine rectus sheath, and a simple computational investigation of the tissue. Analysis using Laplace׳s law showed a circumferential stress in the abdominal wall of approx. 1.1MPa due to an IAP of 11kPa, commonly seen during coughing. Uniaxial and biaxial tensile tests were conducted on samples of porcine rectus sheath to characterise the stress-stretch responses of the tissue. Under uniaxial tension, fibre direction samples failed on average at a stress of 4.5MPa at a stretch of 1.07 while cross-fibre samples failed at a stress of 1.6MPa under a stretch of 1.29. Under equi-biaxial tension, failure occurred at 1.6MPa with the fibre direction stretching to only 1.02 while the cross-fibre direction stretched to 1.13. Uniaxial and biaxial stress-stretch plots are presented allowing detailed modelling of the tissue either in silico or in a surrogate material. An FeBio computational model of the tissue is presented using a combination of an Ogden and an exponential power law model to represent the matrix and fibres respectively. The structural properties of porcine rectus sheath have been characterised and add to the small set of human data in the literature with which it may be possible to develop methods to reduce the incidence of incisional hernia development.

  9. Changes in Mechanical Properties of Rat Bones under Simulated Effects of Microgravity and Radiation†

    Science.gov (United States)

    Walker, Azida H.; Perkins, Otis; Mehta, Rahul; Ali, Nawab; Dobretsov, Maxim; Chowdhury, Parimal

    The aim of this study was to determine the changes in elasticity and lattice structure in leg bone of rats which were: 1) under Hind-Limb Suspension (HLS) by tail for 2 weeks and 2) exposed to a total radiation of 10 Grays in 10 days. The animals were sacrificed at the end of 2 weeks and the leg bones were surgically removed, cleaned and fixed with a buffered solution. The mechanical strength of the bone (elastic modulus) was determined from measurement of bending of a bone when under an applied force. Two methodologies were used: i) a 3-point bending technique and ii) classical bending where bending is accomplished keeping one end fixed. Three point bending method used a captive actuator controlled by a programmable IDEA drive. This allowed incremental steps of 0.047 mm for which the force is measured. The data is used to calculate the stress and the strain. In the second method a mirror attached to the free end of the bone allowed a reflected laser beam spot to be tracked. This provided the displacement measurement as stress levels changed. Analysis of stress vs. strain graph together with solution of Euler-Bernoulli equation for a cantilever beam allowed determination of the elastic modulus of the leg bone for (i) control samples, (ii) HLS samples and (iii) HLS samples with radiation effects. To ascertain changes in the bone lattice structure, the bones were cross-sectioned and imaged with a 20 keV beam of electrons in a Scanning Electron Microscope (SEM). A backscattered detector and a secondary electron detector in the SEM provided the images from well-defined parts of the leg bones. Elemental compositions in combination with mechanical properties (elastic modulus and lattice structure) changes indicated weakening of the bones under space-like conditions of microgravity and radiation.

  10. Effects of light intensity on photosynthesis and photoprotective mechanisms in apple under progressive drought

    Institute of Scientific and Technical Information of China (English)

    MA Ping; BAI Tuan-hui; WANG Xiao-qian; MA Feng-wang

    2015-01-01

    The effects of light intensity on photosynthesis and photoprotective mechanisms under progressive drought were studied on apple trees (Malus domestica Borkh.) Fuji. The potted trees were exposed to drought stress for 12 days and different light conditions (100, 60 and 25% sunlight). During the progressive drought, the relative water content (RWC) in leaf declined and was faster in full light than in 60 and 25% sunlight. However, the decrease in the net photosynthetic rate (Pn), stomatal conductance (Gs) and Rubisco activity were slower under 100% sunlight condition than other light conditions. After the 6 days of drought, the maximum PSII quantum yield (Fv/Fm), the capacity of electrons move beyond QA- (1-Vj) and electron move from intersystem to PSI acceptor side (1-VI)/(1-VJ) decreased, with greater decline extent in brighter light. While RWCs were 〉75%, the variations in different light intensities of Gs and Rubisco activity at identical RWC, suggested the direct effects of light. While the little difference in the state of photosynthetic electron transport chain among tested light intensities indicates the results of faster water loss rate of light. Our results also demonstrated that the enhancement the de-epoxidations of xanthophyll cycle, activities of ascorbate peroxidase (APX) and catalase (CAT) were directly regulated by light intensity. While the higher photorespiration rate (Pr) under stronger light condition was mainly caused by faster water loss rate of light.

  11. Multi-targeted mechanisms underlying the endothelial protective effects of the diabetic-safe sweetener erythritol.

    Directory of Open Access Journals (Sweden)

    Daniëlle M P H J Boesten

    Full Text Available Diabetes is characterized by hyperglycemia and development of vascular pathology. Endothelial cell dysfunction is a starting point for pathogenesis of vascular complications in diabetes. We previously showed the polyol erythritol to be a hydroxyl radical scavenger preventing endothelial cell dysfunction onset in diabetic rats. To unravel mechanisms, other than scavenging of radicals, by which erythritol mediates this protective effect, we evaluated effects of erythritol in endothelial cells exposed to normal (7 mM and high glucose (30 mM or diabetic stressors (e.g. SIN-1 using targeted and transcriptomic approaches. This study demonstrates that erythritol (i.e. under non-diabetic conditions has minimal effects on endothelial cells. However, under hyperglycemic conditions erythritol protected endothelial cells against cell death induced by diabetic stressors (i.e. high glucose and peroxynitrite. Also a number of harmful effects caused by high glucose, e.g. increased nitric oxide release, are reversed. Additionally, total transcriptome analysis indicated that biological processes which are differentially regulated due to high glucose are corrected by erythritol. We conclude that erythritol protects endothelial cells during high glucose conditions via effects on multiple targets. Overall, these data indicate a therapeutically important endothelial protective effect of erythritol under hyperglycemic conditions.

  12. Mechanical behavior and electrical property of CFRC-strengthened RC beams under fatigue and monotonic loading

    International Nuclear Information System (INIS)

    This study introduces a new CFRC-strengthened RC beam model which can both strengthen and monitor the large-scale RC element used in concrete infrastructures. An experiment of testing four-point bending beams is proceeded in order to analyze mechanical behavior and electrical property of the designed beam under monotonic loading as well as the relationship between electrical property and fatigue damage under cyclic flexural loading. The analytical results indicate that this innovative CFRC-strengthened beam has better flexural performance due to the improved cracking resistance capacity of the CFRC layer. Besides, the change in electrical resistance of the beam is detected under monotonic loading. It is found that the thicker the CFRC layer, the larger the electrical resistance increases, and while electrical resistance irreversibly increases as load cycling progresses, the greater the stress amplitude, the greater the fatigue damage, and the larger the residual resistance increases. Based on this discovery, a new technique to monitor the damage of the designed CFRC-strengthened RC beam is produced by means of resistance measurement

  13. The aetiology of acute and chronic pancreatitis over time in a hospital in Copenhagen

    DEFF Research Database (Denmark)

    Nøjgaard, Camilla; Bendtsen, Flemming; Matzen, Peter;

    2010-01-01

    INTRODUCTION: The change in aetiology over time of acute and chronic pancreatitis has been sparsely described, as has also the validity of the diagnostic codes. The aim of the study was 1) to clarify whether the aetiology of acute and chronic pancreatitis changed during the period 1983-2005, and 2......) to validate the diagnostic codes over time for acute and chronic pancreatitis registered in the Danish National Patient Registry (NPR) in the same period. MATERIAL AND METHODS: All admissions at Hvidovre Hospital coded in the NPR in 1983, 1994 and 2005 with a diagnosis of either acute or chronic......: Gallstone disease significantly (p = 0.04) increased as the cause of acute pancreatitis over the 22-year period, while alcohol remained the major cause of chronic pancreatitis. The validity of the diagnoses for patients with acute pancreatitis varied between 51% and 73%, and for chronic pancreatitis between...

  14. The aetiology of acute and chronic pancreatitis over time in a hospital in Copenhagen

    DEFF Research Database (Denmark)

    Nøjgaard, Camilla; Bendtsen, Flemming; Matzen, Peter;

    2010-01-01

    INTRODUCTION: The change in aetiology over time of acute and chronic pancreatitis has been sparsely described, as has also the validity of the diagnostic codes. The aim of the study was 1) to clarify whether the aetiology of acute and chronic pancreatitis changed during the period 1983-2005, and 2......) to validate the diagnostic codes over time for acute and chronic pancreatitis registered in the Danish National Patient Registry (NPR) in the same period. MATERIAL AND METHODS: All admissions at Hvidovre Hospital coded in the NPR in 1983, 1994 and 2005 with a diagnosis of either acute or chronic pancreatitis......: Gallstone disease significantly (p = 0.04) increased as the cause of acute pancreatitis over the 22-year period, while alcohol remained the major cause of chronic pancreatitis. The validity of the diagnoses for patients with acute pancreatitis varied between 51% and 73%, and for chronic pancreatitis between...

  15. Brain Mechanisms Underlying Urge Incontinence and its Response to Pelvic Floor Muscle Training

    Science.gov (United States)

    Griffiths, Derek; Clarkson, Becky; Tadic, Stasa D.; Resnick, Neil M.

    2016-01-01

    Purpose Urge urinary incontinence is a major problem, especially in the elderly, and to our knowledge the underlying mechanisms of disease and therapy are unknown. We used biofeedback assisted pelvic floor muscle training and functional brain imaging (functional magnetic resonance imaging) to investigate cerebral mechanisms, aiming to improve the understanding of brain-bladder control and therapy. Materials and Methods Before receiving biofeedback assisted pelvic floor muscle training functionally intact, older community dwelling women with urge urinary incontinence as well as normal controls underwent comprehensive clinical and bladder diary evaluation, urodynamic testing and brain functional magnetic resonance imaging. Evaluation was repeated after pelvic floor muscle training in those with urge urinary incontinence. Functional magnetic resonance imaging was done to determine the brain reaction to rapid bladder filling with urgency. Results Of 65 subjects with urge urinary incontinence 28 responded to biofeedback assisted pelvic floor muscle training with 50% or greater improvement of urge urinary incontinence frequency on diary. However, responders and nonresponders displayed 2 patterns of brain reaction. In pattern 1 in responders before pelvic floor muscle training the dorsal anterior cingulate cortex and the adjacent supplementary motor area were activated as well as the insula. After the training dorsal anterior cingulate cortex/supplementary motor area activation diminished and there was a trend toward medial prefrontal cortex deactivation. In pattern 2 in nonresponders before pelvic floor muscle training the medial prefrontal cortex was deactivated, which changed little after the training. Conclusions In older women with urge urinary incontinence there appears to be 2 patterns of brain reaction to bladder filling and they seem to predict the response and nonresponse to biofeedback assisted pelvic floor muscle training. Moreover, decreased cingulate

  16. Sleep duration and its role in the aetiology of cardio-metabolic health outcomes

    OpenAIRE

    Hense, Sabrina

    2011-01-01

    An adequate amount of sleep is believed to be important for optimal health and functioning throughout life and changes in sleep duration were found to be associated with several especially cardio-metabolic - health outcomes in adults as well as in children. The factors that influence sleep duration are multi-factorial and the interplay between sleep duration and other factors in the aetiology of cardio-metabolic outcomes is complex and not fully understood yet. Internationally comparable data...

  17. Development of Preventive Measures Based on the Aetiology of Dental Caries: A Review

    OpenAIRE

    Hamada, Shigeyuki; Ooshima, Takashi; Fijiwara, Taku; Minami, Takahiro; Kimura, Shigenobu

    2011-01-01

    Mutans streptococci including Streptococcus mutans and Streptococcus sobrinus are aetiologically associated with the development of dental caries in humans and experimental animals. These organisms produce glucosyltransferases (GTases), which catalyse the synthesis of adherent glucan from sucrose, promoting the adherence of the organisms to the tooth surface. In addition, they release large quantities of acids from various dietary sugars. These are the essential virulence factors of mutans st...

  18. Midbrain infarction: associations and aetiologies in the New England Medical Center Posterior Circulation Registry

    OpenAIRE

    Martin, P.; Chang, H.; Wityk, R; CAPLAN, L.

    1998-01-01

    Most reports of midbrain infarction have described clinicoanatomical correlations rather than associations and aetiologies. Thirty nine patients with midbrain infarction (9.4%) are described out of a series of 415 patients with vertebrobasilar ischaemic lesions in the New England Medical Center Posterior Circulation Registry. Patients were categorised according to the rostral-caudal extent of infarction. The "proximal" vertebrobasilar territory includes the medulla and po...

  19. Charting the landscape of priority problems in psychiatry, part 2: pathogenesis and aetiology.

    Science.gov (United States)

    Stephan, Klaas E; Binder, Elisabeth B; Breakspear, Michael; Dayan, Peter; Johnstone, Eve C; Meyer-Lindenberg, Andreas; Schnyder, Ulrich; Wang, Xiao-Jing; Bach, Dominik R; Fletcher, Paul C; Flint, Jonathan; Frank, Michael J; Heinz, Andreas; Huys, Quentin J M; Montague, P Read; Owen, Michael J; Friston, Karl J

    2016-01-01

    This is the second of two companion papers proposing priority problems for research on mental disorders. Whereas the first paper focuses on questions of nosology and diagnosis, this Personal View concerns pathogenesis and aetiology of psychiatric diseases. We hope that this (non-exhaustive and subjective) list of problems, nominated by scientists and clinicians from different fields and institutions, provides guidance and perspectives for choosing future directions in psychiatric science. PMID:26573969

  20. Aetiology of acute gastroenteritis in children in Najran region, Saudi Arabia

    OpenAIRE

    Mohamed Saeed Zayed AlAyed; Ahmed Morad Asaad; Abdulrab Ahmed Mahdi; Mohamed Ansar Qureshi

    2013-01-01

    Objectives: Gastroenteritis is a leading cause of childhood morbidity and mortality in developing countries. Our aim was to determine the prevalence of bacterial, viral and parasitic aetiology of gastroenteritis in children aged < 5 years in the Najran region, south-western Saudi Arabia, to determine the contribution of these enteropathogens in childhood diarrhoeal diseases and to put forward effective preventive measures for controlling the disease in the future. Design and Setting: A d...

  1. Comparison of the aetiology of stillbirth over five decades in a single centre: a retrospective study

    Science.gov (United States)

    Wou, Karen; Ouellet, Marie-Pier; Chen, Moy-Fong; Brown, Richard N

    2014-01-01

    Objective To compare the rates and aetiologies of stillbirth over the past 50 years. Study design We reviewed all autopsy reports for stillbirths occurring between 1989 and 2009 at the McGill University Health Centre to determine the pathological aetiology of stillbirths. We also reviewed maternal characteristics. We compared our results with a previous study published in 1992 on aetiologies of stillbirth from 1961 to 1988 at the same institution. Results From among the 79 410 births between 1989 and 2009, 217 stillbirths were included in our study. The mean maternal age was 31.05 (±5.8) years. In 28.1% of cases, there was a history of subfertility. The mean gestational age at diagnosis was 32.69 (±5.58) weeks, with a birthweight of 1888 (±1084) g. The main causes of stillbirth were unknown (26.7%), placental factors (19.8%) and abruptio placentae (12.9%). Other causes included haematogenous or ascending infection (10.6%), fetal malformations (8.3%), maternal hypertension (3.2%), intrauterine growth restriction (2.8%), diabetes (1.8%) and intrapartum asphyxia (1.4%). Other fetal causes were found in 12.4% of cases. Conclusions Owing to detailed pathological examination of most stillbirth cases over the past five decades at our tertiary obstetrical centre, we could study the trends in the aetiology of stillbirths in a cohort of more than 150 000 births. In 50 years, the rate of stillbirth has decreased from 115 to 32 cases/10 000 births from the 1960s to 2000s, which represents a reduction of 72%. Stillbirth from unknown cause remains the most common contributor, with 40% of these cases occurring in late pregnancy. PMID:24902725

  2. Relationship between aetiology and left ventricular systolic dysfunction in hypertrophic cardiomyopathy

    OpenAIRE

    Rosmini, Stefania

    2015-01-01

    Background: Hypertrophic cardiomyopathy (HCM) is a common cardiac disease caused by a range of genetic and acquired disorders. The most common cause is genetic variation in sarcomeric proteins genes. Current ESC guidelines suggest that particular clinical features (‘red flags’) assist in differential diagnosis. Aims: To test the hypothesis that left ventricular (LV) systolic dysfunction in the presence of increased wall thickness is an age-specific ‘red flag’ for aetiological diagnosis an...

  3. The definition, aetiology, presentation, diagnosis and management of previous caesarean scar defects.

    Science.gov (United States)

    Allornuvor, G F N; Xue, M; Zhu, X; Xu, D

    2013-11-01

    Caesarean sections are the most commonly performed surgical procedures involving the uterus in fertile women. Typically, this surgery involves a transverse incision in the anterior lower uterine segment. The incidence of caesarean sections is on the increase worldwide, and consequently, the complications associated with them are becoming more common. One such complication that is gaining more attention is previous lower uterine segment caesarean scar defect (PCSD). In this review, we sought to explore the definition, aetiology, presentation, diagnosis and management of PCSD.

  4. Coral bleaching under thermal stress: putative involvement of host/symbiont recognition mechanisms

    Directory of Open Access Journals (Sweden)

    Tambutte Sylvie

    2009-08-01

    Full Text Available Abstract Background Coral bleaching can be defined as the loss of symbiotic zooxanthellae and/or their photosynthetic pigments from their cnidarian host. This major disturbance of reef ecosystems is principally induced by increases in water temperature. Since the beginning of the 1980s and the onset of global climate change, this phenomenon has been occurring at increasing rates and scales, and with increasing severity. Several studies have been undertaken in the last few years to better understand the cellular and molecular mechanisms of coral bleaching but the jigsaw puzzle is far from being complete, especially concerning the early events leading to symbiosis breakdown. The aim of the present study was to find molecular actors involved early in the mechanism leading to symbiosis collapse. Results In our experimental procedure, one set of Pocillopora damicornis nubbins was subjected to a gradual increase of water temperature from 28°C to 32°C over 15 days. A second control set kept at constant temperature (28°C. The differentially expressed mRNA between the stressed states (sampled just before the onset of bleaching and the non stressed states (control were isolated by Suppression Subtractive Hybridization. Transcription rates of the most interesting genes (considering their putative function were quantified by Q-RT-PCR, which revealed a significant decrease in transcription of two candidates six days before bleaching. RACE-PCR experiments showed that one of them (PdC-Lectin contained a C-Type-Lectin domain specific for mannose. Immunolocalisation demonstrated that this host gene mediates molecular interactions between the host and the symbionts suggesting a putative role in zooxanthellae acquisition and/or sequestration. The second gene corresponds to a gene putatively involved in calcification processes (Pdcyst-rich. Its down-regulation could reflect a trade-off mechanism leading to the arrest of the mineralization process under stress

  5. Hydrocarbon activation under sulfate-reducing and methanogenic conditions proceeds by different mechanisms.

    Science.gov (United States)

    Head, Ian; Gray, Neil; Aitken, Caroline; Sherry, Angela; Jones, Martin; Larter, Stephen

    2010-05-01

    Microbial degradation of alkanes typically involves their conversion to fatty acids which are then catabolised by beta-oxidation. The critical step in this process is activation of the hydrocarbon. Under oxic conditions this is catalyzed by monooxygenase enzymes with the formation of long chain alcohols. In the absence of oxygen alternative alkane activation mechanisms have been observed or proposed. Fumarate addition to alkanes to form alkyl succinates is considered a central process in anaerobic hydrocarbon degradation. Comparative studies of crude oil degradation under sulphate-reducing and methanogenic conditions revealed distinctive patterns of compound class removal and metabolite formation. Alkyl succinates derived from C7 to C26 n-alkanes and branched chain alkanes were found in abundance in sulfate-reducing systems but these were not detected during methanogenic crude oil degradation. Only one other mechanism of alkane activation has been elucidated to date. This involves addition of carbon derived from bicarbonate/CO2 to C-3 of an alkane chain to form a 2-ethylalkane with subsequent removal of the ethyl group leading to the formation of a fatty acid 1 carbon shorter than the original alkane. 2-ethylalkanes have never been detected as metabolites of anaerobic alkane degradation and were not detected in crude oil-degrading methanogenic systems. Due to the range of alkanes present in crude oil it was not possible to infer the generation of C-odd acids from C-even alkanes which is characteristic of the C-3 carboxylation mechanism. Furthermore genes homologous to alkysuccinate synthetases were not detected in the methanogenic hydrocarbon degrading community by pyrosequencing of total DNA extracted from methanogenic enrichments cultures. beta-oxidation genes were detected and intriguingly, alcohol and aldehyde dehydrogenase genes were present. This offers the possibility that alkane activation in the methanogenic system does not proceed via acid metabolites

  6. Contraction and relaxation of isolated cardiac myocytes of the frog under varying mechanical loads.

    Science.gov (United States)

    Parikh, S S; Zou, S Z; Tung, L

    1993-02-01

    The mechanics of cardiac systole and relaxation have been studied primarily at the level of the whole heart or intact muscle. End-systolic pressure-volume relations of frog hearts have been found to be load dependent, whereas those of the mammal are relatively load independent. On the other hand, myocardial relaxation as studied at the muscle level is load independent in the frog but markedly load dependent in the mammal. Interpretation of these studies is complicated because of the unknown contribution of extracellular connective tissue, neurohumoral factors, and, in the case of the heart, the complex chamber geometry. Therefore, it is valuable to study cardiac mechanics at the level of the basic unit of contractile activity--the isolated myocyte. The goal of this study was to subject isolated frog cardiomyocytes to mechanical loading paradigms that mimic those presented to the cells within the heart. In the first part of this study, the afterload and preload of contracting cells were varied to study their effects on the end-systolic force-length relation, which was consistently found to be load independent over the range of isotonic shortening tested (typically 5%). We also investigated the force-length-time response of the cells to test the concept of the heart behaving as a time-varying elastance. Our results suggest that in this regard the frog myocyte behaves like mammalian muscle, and they are consistent with the presence of a small viscosity within the cell. We conclude that the tissue structure of the frog heart may contribute to disparity in mechanical behavior at the different structural levels. In the second part of this study, we subjected isolated frog cardiomyocytes to four different loading paradigms to test the hypothesis that myocardial relaxation in the frog is independent of load. These sequences consisted of afterloaded contractions followed by conventional isotonic-isometric relaxation (ACCR) or afterloaded contractions followed by

  7. Proteome Analysis of Response Mechanism in Different Growing Stages of Soybean under Flooding

    Institute of Scientific and Technical Information of China (English)

    Amana Khatoon; Shafiq Rehman; Muhammad Jamil; Iftekhar Ahmad; Setsuko Komatsu

    2012-01-01

    Flooding is one of the severe environmental factors which impair growth and yield in soybean plant.To investigate the response mechanism in different growing stages of soybean under flooding stress,changes in protein expression were analyzed using a proteomics approach.Two-day-old soybeans were subjected to flooding for 2 and 5 days.Proteins were extracted from root and cotyledon of soybean with 2 days of flooding stress,and from root,hypocotyl and leaf of soybean with 5 day of flooding stress.Proteins were separated by two-dimensional polyacrylamide gel electrophoresis and were identified using MS.In root and cotyledon,57 and 20 proteins were significantly changed under flooding stress of 2 days.In root,hypocotyl and leaf,51,66 and 51 proteins were significantly changed under flooding stress of 5 days.Heat shock 70 kDa protein was changed commonly in root and cotyledon of soybean with 2 days of flooding stress; while,isoflavone reductase was commonly changed in root,hypocotyl and leaf of soybean with 5 day of flooding stress.Biophoton emission was increased from all the organs of soybean with 2 and 5 days of flooding stress.The changes in Heat shock 70 kDa protein and isoflavone reductase indicated that flooding stress affected the stress responsive proteins which might lead to increased biophoton emission.These results suggest that imbalance in expression of Heat shock 70 kDa protein and isoflavone reductase along with other disease/defense and metabolism related proteins can impair the growth of root,cotyledon,hypocotyl and leaf of soybean seedlings under flooding stress.

  8. Microstructure and mechanical properties of an Al–Mg alloy solidified under high pressures

    International Nuclear Information System (INIS)

    Highlights: •Al–42.2Mg alloy was solidified under pressures of 1, 2, and 3 GPa and the microstructure analyzed. •A thermodynamic calculation of the Al–Mg phase diagram at high pressures was performed. •The phase content changes from predominantly γ-Al12Mg17 at 1 GPa to FCC solid solution at 3 GPa. •The β-Al3Mg2 is predicted to remain stable at low temperatures but is not observed. •The alloy solidified at high pressure has remarkably enhanced ultimate tensile strength. -- Abstract: Phase formation, the microstructure and its evolution, and the mechanical properties of an Al–42.2 at.% Mg alloy solidified under high pressures were investigated. After solidification at pressures of 1 GPa and 2 GPa, the main phase is the γ phase, richer in Al than in equilibrium condition. When the pressure is further increased to 3 GPa, the main phase is the supersaturated Al(Mg) solid solution with Mg solubility up to 41.6 at.%. Unlike in similar alloys solidified at ambient pressure, the β phase does not appear. Calculated high-pressure phase diagrams of the Al–Mg system show that although the stability range of the β phase is diminished with pressure, it is still thermodynamically stable at room temperature. Hence, the disappearance of the β phase is interpreted as kinetic suppression, due to the slow diffusion rate at high pressures, which inhibits solid–solid reactions. The Al–42.2 at.% Mg alloy solidified under 3 GPa has remarkably enhanced ultimate tensile strength compared to the alloy solidified under normal atmospheric pressure

  9. Comparative Mechanisms of Photosynthetic Carbon Acquisitionin Hizikiafusiforme Under Submersed and Emersed Conditions

    Institute of Scientific and Technical Information of China (English)

    ZOUDing-Hui; GAOKun-Shan

    2004-01-01

    The economic seaweed Hizikia fusiforme (Harv.) Okamura (Sargassaceae, Phaeophyta) usually experiences periodical exposures to air at low tide. Photosynthetic carbon acquisition mechanisms were comparatively studied under submersed and emersed conditions in order to establish a general understanding of its photosynthetic characteristics associated with tidal cycles. When submersed in seawater, H.fusiforme was capable of acquiring HCO3- as a source of inorganic carbon (Ci) to drive photosynthesis, while emersed and exposed to air, it used atmospheric 002 for photosynthesis. The pH changes surroundingthe H.fusiforme fronds had less influence on the photosynthetic rates under emersed condition than under submersed condition. When the pH was as high as 10.0, emersed H.fusiforme could photosynthesize efficiently, but the submersed alga exhibited very poor photosynthesis. Extracellular carbonic anhydrase (CA) played an important role in the photosynthetic acquisitions of exogenous Ci in water as well as in air. Both the concentrations of dissolved inorganic carbon in general seawater and CO2 in air were demonstrated to limit the photosynthesis of H.fusiforme, which was sensitive to O2. It appeared that the exogenous carbon acquisition system, being dependent of external CA activity, operates in a way not enough to raise intracellular CO2 level to prevent photorespiration. The inability of H.fusiforme to achieve its maximum photosynthetic rate at the current ambient Ci levels under both submersed and emersed conditions suggested that the yield of aquaculture for this economic species would respond profitably to future increases in CO2 concentration in the sea and air.

  10. Aetiology and presentation of ankylosis of the temporomandibular joint: report of 23 cases from Abuja, Nigeria.

    Science.gov (United States)

    Bello, Seidu Adebayo; Aluko Olokun, Bayo; Olaitan, Abayomi Ademola; Ajike, Sunday O

    2012-01-01

    Several studies have reviewed the management of ankylosis of the temporomandibular joint (TMJ), but only a few focused on the aetiology and clinical features. We retrospectively studied the aetiology and clinical features of patients with ankylosis of the TMJ who presented to the Maxillofacial Unit, National Hospital, Abuja, Nigeria, between 2004 and 2009. There were 13 male and 10 female patients, M:F ratio 1.3:1, age range 6-62, mean (SD) 20 (13) years. The aetiological factors were trauma (n=11) that comprised falls (n=6), untreated fractures of the zygomatic arch (n=4) and myositis ossificans (n=1); infection (n=9), that comprised cancrum oris (n=3) and ear infection (n=6); congenital or unknown (n=2), and coronoid hyperplasia (n=1). The maximum interincisal distance at presentation ranged from 0 to 25 mm (mean (SD) 6.7 (7.2) mm). Seventeen had facial deformities. The diagnoses recorded were as follows: left extracapsular ankylosis, (n=8); right intracapsular bony ankylosis, (n=6); left intracapsular bony ankylosis, (n=4); bilateral intracapsular bony ankylosis, (n=4), and bilateral intracapsular fibrous ankylosis (n=1). Extreme poverty was the main predisposing factor. There is a need for a concerted effort among healthcare providers, policy makers, and the world in general to eradicate poverty and improve healthcare to limit the incidence of ankylosis of the TMJ.

  11. A STUDY ON CLINICAL AND AETIOLOGICAL PROFILE OF HYPOKALAEMIC PARALYSIS IN A TERTIARY CARE HOSPITAL

    Directory of Open Access Journals (Sweden)

    Kekathi Vidyasagar

    2016-08-01

    Full Text Available BACKGROUND Hypokalaemic periodic paralysis is a rare disorder characterised by transient attacks of flaccid paralysis of varying intensity and frequency. Although mostly familial in aetiology, several sporadic cases with different causes have been reported. There are two groups of disorders predominantly that causes hypokalaemic paralysis. One group is due to transcellular shift of potassium and other is due to loss of potassium from body either through GI tract or through renal system. MATERIAL AND METHODS Here we report a study on the clinical and aetiological profile of 30 cases of hypokalaemic paralysis admitted in our institution between January 2014 to January 2016. RESULTS The aetiological workup of all the patients was done which revealed thyrotoxic periodic paralysis as the major cause in 12 of 30 patients. Three rare causes of hypokalaemia have been diagnosed which included Bartter’s syndrome, Mixed Connective tissue disorder, Sjogren’s syndrome. Vomiting and diarrhoea was seen in 12 of 30 patients. CONCLUSION Hypokalaemic periodic paralysis is a heterogenous group of disorder. A significant number of patients had thyroid disorders mostly in the form of thyrotoxicosis, non-renal and renal loss of potassium like diarrhoea and vomiting. Early recognition and prompt management of these conditions is essential to prevent residual deformity and further attacks in future.

  12. Transthoracic lung aspiration for the aetiological diagnosis of pneumonia: 25 years of experience from The Gambia.

    Science.gov (United States)

    Ideh, R C; Howie, S R C; Ebruke, B; Secka, O; Greenwood, B M; Adegbola, R A; Corrah, T

    2011-06-01

    Pneumonia remains the leading cause of death in young children worldwide. Global pneumonia control depends on a good understanding of the aetiology of pneumonia. Percutaneous transthoracic aspiration culture is much more sensitive than blood culture in identifying the aetiological agents of pneumonia. However, the procedure is not widely practised because of lack of familiarity with it and concerns about potential adverse events. We review the diagnostic usefulness and safety of this procedure over 25 years of its use in research and routine practice at the UK Medical Research Council (MRC), The Gambia, and give a detailed description of the procedure itself. Published materials were identified from the MRC's publication database and systematic searches using the PubMed/Medline and Google search engines. Data from a current pneumonia aetiology study in the unit are included together with clinical experience of staff practising at the unit over the period covered in this review. A minimum of 500 lung aspirates were performed over the period of review. Lung aspiration produces a greater yield of diagnostic bacterial isolates than blood culture. It is especially valuable clinically when pathogens not covered by standard empirical antibiotic treatment, such as Mycobacterium tuberculosis and Staphylococcus aureus, are identified. There have been no deaths following the procedure in our setting and a low rate of other complications, all transient. Lung aspiration is currently the most sensitive method for diagnosing pneumonia in children. With appropriate training and precautions it can be safely used for routine diagnosis in suitable referral hospitals. PMID:21477423

  13. An investigation into febrile illnesses of unknown aetiology in Wipim, Papua New Guinea.

    Science.gov (United States)

    Bande, Grace; Hetzel, Manuel W; Iga, Jonah; Barnadas, Celine; Mueller, Ivo; Siba, Peter M; Horwood, Paul F

    2014-01-01

    In Papua New Guinea the aetiology of febrile illnesses remains poorly characterized, mostly due to poor diagnostic facilities and the inaccessibility of much of the rural areas of the country. We investigated the aetiological agents of febrile illnesses for 136 people presenting to Wipim Health Centre in Western Province, Papua New Guinea. Arboviral and rickettsial real-time polymerase chain reaction (PCR) assays, malaria blood smears and a malaria PCR test were used to identify pathogens associated with a history of fever. In 13% (n = 18) of cases an aetiological agent was identified. Dengue virus type 1 was detected in 11% (n = 15) of the samples tested and malaria in 2% (n = 3). None of the other arboviral or rickettsial pathogens tested for were detected in any of the samples. Although dengue viruses have been identified in Papua New Guinea using serological methods, this study represents the first direct detection of dengue in the country. The detection of malaria, on the other hand, was surprisingly low considering the previous notion that this was a hyperendemic region of Papua New Guinea. PMID:26930888

  14. AETIOLOGICAL PROFILE AND OUTCOME IN PATIENTS WITH ACUTE KIDNEY INJURY (AKI ADMITTED TO VIMS, BELLARY

    Directory of Open Access Journals (Sweden)

    Ramamurthy

    2014-10-01

    Full Text Available BACKGROUND AND OBJECTIVES: This was a study about the various causes of ARF, in our hospital (VIMS, Bellary during a specified period, and to find out the incidence of Pre-renal, Renal and Post-renal causes by using renal failure indices and to analyze outcome of ARF pertaining to the aetiology. MATERIALS AND METHODS: 70 cases admitted at VIMS, Bellary during the period January 2012 to june 2013, with clinical evidence of acute renal failure were included in the study. They were evaluated for various etiological, prognostic factors and its outcome. RESULTS: Among the various aetiologies in our study, snake bite (28.6%, ADD (27.1%, RPGN (7.1% were the most common. Most common type of renal failure was prerenal (50%, among them ADD was the predominant cause followed by intrinsic failure (47%, among them snake bite was leading cause. Patients presenting with Anuria, late presentation to hospital, blood pressure 3mg had poor outcome. CONCLUSION: Amongst the etiological factors snake bite and ADD ranked first. Prognosis was determined by age, aetiology of renal failure, initial creatinine value, blood pressure, time of presentation to. Even though both snake bite and ADD are equally common causes, morbidity is more in snake bite and cost of treatment also more in snake bite as many of them require dialysis.

  15. Aetiology of maxillofacial fractures: a review of published studies during the last 30 years.

    Science.gov (United States)

    Boffano, Paolo; Kommers, Sofie C; Karagozoglu, K Hakki; Forouzanfar, Tymour

    2014-12-01

    The epidemiology of facial trauma may vary widely across countries (and even within the same country), and is dependent on several cultural and socioeconomic factors. We know of few reviews of published reports that have considered the sex distribution and aetiology of maxillofacial trauma throughout the world. The aim of this review was to discuss these aspects as they have been presented in papers published during the last 30 years. We made a systematic review of papers about the epidemiology of maxillofacial trauma that were published between January 1980 and December 2013 and identified 69 studies from Africa (n=9), North America and Brazil (n=6), Asia (n=36), Europe (n=16), and Oceania (n=2). In all the studies men outnumbered women, the ratio usually being more than 2:1. In American, African, and Asian studies road traffic crashes were the predominant cause. In European studies the aetiology varied, with assaults and road traffic crashes being the most important factors. In Oceania assaults were the most important. A comparison of the incidence of maxillofacial trauma of different countries together with a knowledge of different laws (seat belts for drivers, helmets for motocyclists, speed limits, and protection worn during sports and at work) is crucial to allow for improvement in several countries. To our knowledge this paper is the first attempt to study and compare the aetiologies of maxillofacial trauma. PMID:25218316

  16. Mechanisms underlying the associations of maternal age with adverse perinatal outcomes

    DEFF Research Database (Denmark)

    Lawlor, Debbie A; Mortensen, Laust; Andersen, Anne-Marie Nybo

    2011-01-01

    The mechanisms underlying the association between maternal age (both young and older maternal age) and adverse perinatal outcomes are unclear. Methods We examined the association of maternal age at first birth with preterm birth (..., such as childhood socio-economic characteristics—a confounder we hypothesized would exaggerate the young maternal age–adverse outcomes association but mask the older maternal age–adverse outcome association. Results There was a U-shaped association of maternal age with risk of preterm birth (lowest risk age 24......–30 years) and SGA (lowest risk age 26–30 years) in cohort analyses. In analyses with sister control, there was a J-shaped association of maternal age with preterm birth, with a monotonic increase in risk across the maternal age range from 24 years of maternal age. For SGA, risk increased across the age...

  17. The Mechanisms of Corporate Meetings under the Companies and Allied Matters Act (CAMA 1990

    Directory of Open Access Journals (Sweden)

    Aderibigbe, O. I.

    2011-04-01

    Full Text Available The purpose of this study was to assess the mechanism of corporate meetings under the Companies and Allied Matters Act (CAMA 1990. This review revealed two major types of meetings, public meetings convened by individuals or bodies to which there is an open invitation extended to any member of the public, and meetings of bodies of which the members are limited and known. However, the study was preoccupied with the second category. Therefore, there is the need for the various Legislatures of countries to work towards enacting effective and efficient company legislation to that effect. It is recommended among others that in Nigeria that the fine of N50 for every day of default to hold a statutory meeting should be reviewed to be punitive.

  18. Influence of plasma on the densification mechanism of SPS under multi-field effect

    Institute of Scientific and Technical Information of China (English)

    Yu-hong Chang; Di Huang; Cheng-chang Jia; Zhao-wen Cui; Cong-cong Wang; Dong Liang

    2014-01-01

    The densification mechanism of an Fe-based alloy powder containing tiny oxide particles under the synergic multi-field effect of spark plasma sintering (SPS) was investigated. Metallographic microscopy and scanning electron microscopy were used to observe the mor-phology of samples sintered at different temperatures, and the temperature distribution in an individual spherical powder particle during sin-tering was calculated in consideration of the influence of plasma, which was qualified and quantified through the analysis of the U-I curve. The plasma was observed to play a substantial role in activating and heating the samples at the very early stage of sintering, whereas the joule-heat effect played a dominant role during sintering. Moreover, the plasma also facilitated the diffusion and migration of materials for neck formation.

  19. The effects of stoichiometry on the mechanical properties of icosahedral boron carbide under loading.

    Science.gov (United States)

    Taylor, DeCarlos E; McCauley, James W; Wright, T W

    2012-12-19

    The effects of stoichiometry on the atomic structure and the related mechanical properties of boron carbide (B(4)C) have been studied using density functional theory and quantum molecular dynamics simulations. Computational cells of boron carbide containing up to 960 atoms and spanning compositions ranging from 6.7% to 26.7% carbon were used to determine the effects of stoichiometry on the atomic structure, elastic properties, and stress-strain response as a function of hydrostatic, uniaxial, and shear loading paths. It was found that different stoichiometries, as well as variable atomic arrangements within a fixed stoichiometry, can have a significant impact on the yield stress of boron carbide when compressed uniaxially (by as much as 70% in some cases); the significantly reduced strength of boron carbide under shear loading is also demonstrated.

  20. Keep your eyes on development - The behavioural and neurophysiological development of visual mechanisms underlying form processing

    Directory of Open Access Journals (Sweden)

    Carlijn eVan Den Boomen

    2012-03-01

    Full Text Available Visual form perception is essential for correct interpretation of, and interaction with, our environment. Form perception depends on visual acuity and processing of specific form characteristics, such as luminance contrast, spatial frequency, colour, orientation, depth and even motion information. As other cognitive processes, form perception matures with age. This paper aims at providing a concise overview of our current understanding of the typical development, from birth to adulthood, of form-characteristic processing, as measured both behaviourally and neurophysiologically. Two main conclusions can be drawn. First, the current literature conveys that for most reviewed characteristics a developmental pattern is apparent. These trajectories are discussed in relation to the organisation of the visual system. The second conclusion is that significant gaps in the literature exist for several age-ranges. To complete our understanding of the typical and, by consequence, atypical development of visual mechanisms underlying form processing, future research should uncover these missing segments.

  1. Mechanism underlying Kármán vortex street breakdown preceding secondary vortex street formation

    Science.gov (United States)

    Dynnikova, G. Ya.; Dynnikov, Ya. A.; Guvernyuk, S. V.

    2016-05-01

    The Kármán street that develops behind a bluff body transforms in the far wake into a secondary vortex street of lower frequency and stronger vortices. Before this transformation, the primary street decays. This interesting phenomenon was investigated in a number of experimental and theoretical studies. Much of that work is devoted to studying the reasons for the formation of the secondary street and its frequency characteristics. Reasons for the decay of the primary street are not well understood. In this work, the mechanism underlying the breaking of the primary vortex street is studied. A qualitative explanation of this process is presented wherein a region of heightened density of the dipole moment forms. This region moves relative to the Kármán vortices so that its distance from the body remains constant. In this region, the Kármán vortex street collapses.

  2. Adaptive Response in Animals Exposed to Non-Ionizing Radiofrequency Fields: Some Underlying Mechanisms

    Directory of Open Access Journals (Sweden)

    Yi Cao

    2014-04-01

    Full Text Available During the last few years, our research group has been investigating the phenomenon of adaptive response in animals exposed to non-ionizing radiofrequency fields. The results from several separate studies indicated a significant increase in survival, decreases in genetic damage as well as oxidative damage and, alterations in several cellular processes in mice pre-exposed to radiofrequency fields and subsequently subjected to sub-lethal or lethal doses of γ-radiation or injected with bleomycin, a radiomimetic chemical mutagen. These observations indicated the induction of adaptive response providing the animals the ability to resist subsequent damage. Similar studies conducted by independent researchers in mice and rats have supported our observation on increased survival. In this paper, we have presented a brief review of all of our own and other independent investigations on radiofrequency fields-induced adaptive response and some underlying mechanisms discussed.

  3. Dust generation mechanisms under powerful plasma impacts to the tungsten surfaces in ITER ELM simulation experiments

    International Nuclear Information System (INIS)

    In recent tokamak simulation experiments with the QSPA Kh-50 facility several mechanisms of dust generation from tungsten surfaces under ITER ELM-like energy loads have been identified. Here cracking and melting are reported. The brittle destruction dominates after a few transient impacts when a network of major cracks forms on the surface. Bifurcation of major cracks results in ejection of dust particles with sizes up to ∼30 μm. Dust generation occurs also after surface melting and following resolidification when fine crack networks along the grain boundaries develop. In this process the destruction is accompanied by bridge formation due to capillary tension across the fine cracks. Next impacts (even weak melt-free ones) can destroy those bridges, which produces considerable amounts of dust particles of nm-size dust. Surface modification after the repetitive plasma pulses also results in creation of nm-size dust

  4. Fatigue mechanisms in an austenitic steel under cyclic loading: Experiments and atomistic simulations

    International Nuclear Information System (INIS)

    Experimental investigations on the austenitic stainless steel X6CrNiNb18-10 (AISI – 347) and concomitant atomistic simulations of a FeNi nanocrystalline model system have been performed in order to understand the basic mechanisms of fatigue damage under cyclic loading. Using electron backscatter diffraction (EBSD) the influence of deformation induced martensitic transformation and NbC size distribution on the fatigue crack formation has been demonstrated. The martensite nucleates prevalently at grain boundaries, triple points and at the specimen free surface and forms small (∼1 µm sized) differently oriented grains. The atomistic simulations show the role of regions of a high density of stacking faults for the martensitic transformation

  5. Study on osteogenesis promoted by low sound pressure level infrasound in vivo and some underlying mechanisms.

    Science.gov (United States)

    Long, Hua; Zheng, Liheng; Gomes, Fernando Cardoso; Zhang, Jinhui; Mou, Xiang; Yuan, Hua

    2013-09-01

    To clarify the effects of low sound pressure level (LSPL) infrasound on local bone turnover and explore its underlying mechanisms, femoral defected rats were stabilized with a single-side external fixator. After exposure to LSPL infrasound for 30min twice everyday for 6 weeks, the pertinent features of bone healing were assessed by radiography, peripheral quantitative computerized tomography (pQCT), histology and immunofluorescence assay. Infrasound group showed a more consecutive and smoother process of fracture healing and modeling in radiographs and histomorphology. It also showed significantly higher average bone mineral content (BMC) and bone mineral density (BMD). Immunofluorescence showed increased expression of calcitonin gene related peptide (CGRP) and decreased Neuropeptide Y (NPY) innervation in microenvironment. The results suggested the osteogenesis promotion effects of LSPL infrasound in vivo. Neuro-osteogenic network in local microenvironment was probably one target mediating infrasonic osteogenesis, which might provide new strategy to accelerate bone healing and remodeling. PMID:23770453

  6. The mechanisms of cracks formation of silver-based contact materials under arc and making pressure

    Institute of Scientific and Technical Information of China (English)

    GUO Feng-yi(郭凤仪); CHEN Zhong-hua(陈忠华); ZHANG Ling-ling(张玲玲); ZHANG Ji-hua(张继华); FW Leuschner

    2004-01-01

    The arc erosion experiments on five kinds of silver-based contact materials, AgZnO (10), AgSnO2 (8.5) In2O3 (4), AgCdO (12), AgNi(10), AgWC(12)C(3) were carried out according to different breaking times, breaking currents, and making pressures. Then based on the theoretical analysis and the photographs taken by scanning electronic microscope with EDAX analyzer, the crack morphology was studied scientifically. Three types of cracks, which are cavity cracks, grain boundaries (or phase boundaries) slipping cracks, and thermal stress cracks, were put forward under arc and making pressure through establishing their physical models and discussing their formation mechanisms.

  7. Examination of Mechanisms Underlying Enhanced Memory Performance in Action Video Game Players: A Pilot Study

    Directory of Open Access Journals (Sweden)

    Xianchun eLi

    2015-06-01

    Full Text Available Previous studies have shown enhanced memory performance resulting from extensive action video game playing. The mechanisms underlying the cognitive benefit were investigated in the current study. We presented two types of retro-cues, with variable intervals to memory array (Task 1 or test array (Task 2, during the retention interval in a change detection task. In Task 1, action video game players (AVGPs demonstrated steady performance while non-action video game players (NVGPs showed decreased performance as cues occurred later, indicating their performance difference increased as the cue-to-memory-array intervals became longer. In Task 2, both participant groups increased their performance at similar rates as cues presented later, implying the performance difference in two groups were irrespective of the test-array-to-cue intervals. These findings suggested that memory benefit from game plays is not attributable to the higher ability of overcoming interference from the following stimuli. Implications for the future studies were discussed.

  8. Structure and mechanism of turbulence under dynamical restriction in plane Poiseuille flow

    CERN Document Server

    Farrell, Brian F; Jiménez, Javier; Constantinou, Navid C; Lozano-Duran, Adrián; Nikolaidis, Marios-Andreas

    2015-01-01

    The perspective of statistical state dynamics (SSD) has been applied to the study of mechanisms underlying turbulence in various physical systems. An example application of SSD is that of the second order closure, referred to as stochastic structural stability theory (S3T), which has provided insight into the dynamics of wall turbulence and the emergence and maintenance of the roll/streak structure. This closure eliminates nonlinear interactions among the perturbations restricting nonlinearity to that of the mean equation and interaction between the mean and perturbations. Simulations at modest $Re$ reveal that the essential features of wall-turbulence dynamics are retained with the dynamics restricted in this manner. Here this restriction of the dynamics is used to obtain a closely related dynamical system, referred to as the restricted non-linear (RNL) system, which is used to study the structure and dynamics of turbulence in plane Poiseuille flow at moderately high $Re$. Remarkably, the RNL system spontane...

  9. Evolution of microstructure and mechanical properties of VVER-1000 RPV steels under re-irradiation

    Science.gov (United States)

    Gurovich, B.; Kuleshova, E.; Shtrombakh, Ya.; Fedotova, S.; Erak, D.; Zhurko, D.

    2015-01-01

    This is a comprehensive study of microstructure and mechanical properties evolution at re-irradiation after recovery annealing of VVER-1000 RPV weld and base metals as well as the effect of annealing on the microstructure and properties of base metal in the zone of the temperature gradient that is implemented during annealing using special heating device. It is shown that the level of radiation-induced microstructural changes under accelerated re-irradiation of weld and base metal is not higher than for the primary irradiation. Thus, we can predict that re-embrittlement of VVER-1000 RPV materials considering the flux effect will not exceed the typical embrittlement rate for the primary irradiation.

  10. Proteomics approach reveals mechanism underlying susceptibility of loquat fruit to sunburn during color changing period.

    Science.gov (United States)

    Jiang, Ji-Mou; Lin, Yong-Xiang; Chen, Yi-Yong; Deng, Chao-Jun; Gong, Hui-Wen; Xu, Qi-Zhi; Zheng, Shao-Quan; Chen, Wei

    2015-06-01

    The objective of this work was to investigate why loquat fruit peels are more sensitive to high temperature and strong sunlight, making them highly susceptible to sunburn, during the color changing period (CCP). Two dimensional gel electrophoresis (2-DE) of the fruit peel proteins was performed over three developmental periods, namely green fruit period (GFP), color changing period and yellow ripening period (YRP). Fifty-five protein spots with at least 2-fold differences in abundance were successfully identified by MALDI-TOF-TOF/MS. The identified proteins were divided into categories related to heat-shock response, stress response and defense, energy metabolism, photosynthesis and protein biosynthesis. The results showed that expression of proteins related to anaerobic respiration and photorespiration were increased while the proteins related to ROS scavenging, polyamine biosynthesis, defense pathogens and photosynthesis were decreased during CCP under heat stress. Our findings provide new insights into the molecular mechanism of loquat fruit susceptible to sunburn during CCP. PMID:25624247

  11. Fatigue mechanisms in an austenitic steel under cyclic loading: Experiments and atomistic simulations

    Energy Technology Data Exchange (ETDEWEB)

    Soppa, E.A., E-mail: ewa.soppa@mpa.uni-stuttgart.de; Kohler, C., E-mail: christopher.kohler@mpa.uni-stuttgart.de; Roos, E., E-mail: eberhard.roos@mpa.uni-stuttgart.de

    2014-03-01

    Experimental investigations on the austenitic stainless steel X6CrNiNb18-10 (AISI – 347) and concomitant atomistic simulations of a FeNi nanocrystalline model system have been performed in order to understand the basic mechanisms of fatigue damage under cyclic loading. Using electron backscatter diffraction (EBSD) the influence of deformation induced martensitic transformation and NbC size distribution on the fatigue crack formation has been demonstrated. The martensite nucleates prevalently at grain boundaries, triple points and at the specimen free surface and forms small (∼1 µm sized) differently oriented grains. The atomistic simulations show the role of regions of a high density of stacking faults for the martensitic transformation.

  12. Study of Acoustic Emission and Mechanical Characteristics of Coal Samples under Different Loading Rates

    Directory of Open Access Journals (Sweden)

    Huamin Li

    2015-01-01

    Full Text Available To study the effect of loading rate on mechanical properties and acoustic emission characteristics of coal samples, collected from Sanjiaohe Colliery, the uniaxial compression tests are carried out under various levels of loading rates, including 0.001 mm/s, 0.002 mm/s, and 0.005 mm/s, respectively, using AE-win E1.86 acoustic emission instrument and RMT-150C rock mechanics test system. The results indicate that the loading rate has a strong impact on peak stress and peak strain of coal samples, but the effect of loading rate on elasticity modulus of coal samples is relatively small. When the loading rate increases from 0.001 mm/s to 0.002 mm/s, the peak stress increases from 22.67 MPa to 24.99 MPa, the incremental percentage is 10.23%, and under the same condition the peak strain increases from 0.006191 to 0.007411 and the incremental percentage is 19.71%. Similarly, when the loading rate increases from 0.002 mm/s to 0.005 mm/s, the peak stress increases from 24.99 MPa to 28.01 MPa, the incremental percentage is 12.08%, the peak strain increases from 0.007411 to 0.008203, and the incremental percentage is 10.69%. The relationship between acoustic emission and loading rate presents a positive correlation, and the negative correlation relation has been determined between acoustic emission cumulative counts and loading rate during the rupture process of coal samples.

  13. Pollination ecology of two species of Elleanthus (Orchidaceae): novel mechanisms and underlying adaptations to hummingbird pollination.

    Science.gov (United States)

    Nunes, C E P; Amorim, F W; Mayer, J L S; Sazima, M

    2016-01-01

    Relationships among floral biology, floral micromorphology and pollinator behaviour in bird-pollinated orchids are important issues to understand the evolution of the huge flower diversity within Orchidaceae. We aimed to investigate floral mechanisms underlying the interaction with pollinators in two hummingbird-pollinated orchids occurring in the Atlantic forest. We assessed floral biology, nectar traits, nectary and column micromorphologies, breeding systems and pollinators. In both species, nectar is secreted by lip calli through spaces between the medial lamellar surfaces of epidermal cells. Such a form of floral nectar secretion has not been previously described. Both species present functional protandry and are self-compatible yet pollinator-dependent. Fruit set in hand-pollination experiments was more than twice that under natural conditions, evidencing pollen limitation. The absence of fruit set in interspecific crosses suggests the existence of post-pollination barriers between these sympatric co-flowering species. In Elleanthus brasiliensis, fruits resulting from cross-pollination and natural conditions were heavier than those resulting from self-pollination, suggesting advantages to cross-pollination. Hummingbirds pollinated both species, which share at least one pollinator species. Species differences in floral morphologies led to distinct pollination mechanisms. In E. brasiliensis, attachment of pollinarium to the hummingbird bill occurs through a lever apparatus formed by an appendage in the column, another novelty to our knowledge of orchid pollination. In E. crinipes, pollinarium attachment occurs by simple contact with the bill during insertion into the flower tube, which fits tightly around it. The novelties described here illustrate the overlooked richness in ecology and morphophysiology in Orchidaceae. PMID:25678071

  14. A role for PERK in the mechanism underlying fluoride-induced bone turnover

    International Nuclear Information System (INIS)

    While it has been well-documented that excessive fluoride exposure caused the skeletal disease and osteoblasts played a critical role in the advanced skeletal fluorosis, the underlying mechanism that mediated these effects remain poorly understood. The present study was undertaken to examine the effect of fluoride on bone of rats and MC3T3-E1 cells in vitro. Herein we found pathological features of high bone turnover in fluoride-treated rats, which was supported by an increase of osteogenic and osteoclastogenic genes expression in different stages of fluoride exposure. The skeletal toxicity of fluoride was accompanied by activation of endoplasmic reticulum (ER) stress and subsequent unfolded protein response (UPR). A novel finding of this study was that expression of PKR-like endoplasmic reticulum kinase (PERK) was the same trend with receptor activator for nuclear factor-κ B ligand (RANKL), and NF-E2 p45-related factor 2 (Nrf2) was the same trend with Runt-related transcription factor 2 (Runx2) in bones of rats exposed to varied fluoride condition. Based on these data, we hypothesized that up-regulation of PERK probably played a role in mediating bone turnover induced by fluoride. Action of fluoride on MC3T3-E1 cells differentiation was demonstrated through analysis of alkaline phosphatase (ALP) activity and mineralized nodules formation. Meantime, an increase of binding immunoglobulin protein (BiP) expression indicated the active ER stress in cells exposed to various dose of fluoride. Blocking PERK expression using siRNA showed the obvious decrease of osteogenic and osteoclastogenic factors expression in MC3T3-E1 cells exposed to certain dose of fluoride that could positively stimulate osteoblastic viability. In conclusion these findings underscore the importance of PERK in modulating fluoride induced bone formation and bone resorption. Understanding the link between PERK and bone turnover could probe into the mechanism underlying different bone lesion of

  15. Pollination ecology of two species of Elleanthus (Orchidaceae): novel mechanisms and underlying adaptations to hummingbird pollination.

    Science.gov (United States)

    Nunes, C E P; Amorim, F W; Mayer, J L S; Sazima, M

    2016-01-01

    Relationships among floral biology, floral micromorphology and pollinator behaviour in bird-pollinated orchids are important issues to understand the evolution of the huge flower diversity within Orchidaceae. We aimed to investigate floral mechanisms underlying the interaction with pollinators in two hummingbird-pollinated orchids occurring in the Atlantic forest. We assessed floral biology, nectar traits, nectary and column micromorphologies, breeding systems and pollinators. In both species, nectar is secreted by lip calli through spaces between the medial lamellar surfaces of epidermal cells. Such a form of floral nectar secretion has not been previously described. Both species present functional protandry and are self-compatible yet pollinator-dependent. Fruit set in hand-pollination experiments was more than twice that under natural conditions, evidencing pollen limitation. The absence of fruit set in interspecific crosses suggests the existence of post-pollination barriers between these sympatric co-flowering species. In Elleanthus brasiliensis, fruits resulting from cross-pollination and natural conditions were heavier than those resulting from self-pollination, suggesting advantages to cross-pollination. Hummingbirds pollinated both species, which share at least one pollinator species. Species differences in floral morphologies led to distinct pollination mechanisms. In E. brasiliensis, attachment of pollinarium to the hummingbird bill occurs through a lever apparatus formed by an appendage in the column, another novelty to our knowledge of orchid pollination. In E. crinipes, pollinarium attachment occurs by simple contact with the bill during insertion into the flower tube, which fits tightly around it. The novelties described here illustrate the overlooked richness in ecology and morphophysiology in Orchidaceae.

  16. Deformation and damage modes of deep argillaceous rocks under hydro-mechanical stresses

    International Nuclear Information System (INIS)

    An experimental identification of the hydro-mechanical behaviour of an argillite rock is proposed within a multi-scale approach. In particular, interest is focused on the spatial and temporal localization of strain and damage in a specimen during hydro-mechanical loading. Firstly, we describe the techniques used to follow the rock evolutions under loading, and in particular Digital Images Correlation (DIC), Acoustic Emission, microscopy and mercury intrusion porosimetry. Measurement errors and device limitations are discussed. The studied material is the Callovo-Oxfordian indurated argillaceous rock (or argillite) of the Bure site where ANDRA has built an underground research laboratory to study the radioactive waste storage. Petrophysical characterizations and microstructural observations by optical and scanning electron microscopy provide an identification of the constitutive phase and a characterization of their spatial distribution and typical sizes. Argillite can be described as a composite structure with a continuous clay matrix and embedded mineral particles, essentially quartz and carbonates. The typical size of these particles ranges from a few micrometers to a few hundreds micrometers, with an average close to 50 μ.m. The general experimental procedure combines two steps: in a fist time, imposed suctions bring samples to a given degree of water saturation, and, in a second time, uniaxial mechanical compression tests are performed. To understand the evolutions of the material under hydric and mechanical loading, samples are instrumented with standard measurement techniques, but also with Digital Image Correlation, at both the global scale of the sample and the local scale of the composite microstructure, and with Acoustic Emissions recording. Moisture transfers are imposed by controlled suctions on the range of 150 to 2.8 MPa, corresponding to the relative humidity range of 32 to 98%RH. During pure hydric solicitation, the changes in physical parameters

  17. Dynamic mechanical response of magnesium single crystal under compression loading: Experiments, model, and simulations

    Science.gov (United States)

    Li, Qizhen

    2011-05-01

    Magnesium single crystal samples are compressed at room temperature under quasistatic (˜0.001 s-1) loading in a universal testing machine and dynamic (430, 1000, and 1200 s-1) loading in a split Hopkinson pressure bar system. Stress-strain curves show that (a) the fracture strain slightly increases with the strain rate; and (b) the maximum strength and strain hardening rate increase significantly when the testing changes from quasistatic to dynamic, although they do not vary much when the strain rate for dynamic testing varies in the range of 430-1200 s-1. The operation of the secondary pyramidal slip system is the dominating deformation mechanism, which leads to a fracture surface with an angle of ˜42° with respect to the loading axial direction. A theoretical material model based on Johnson-Cook law is also derived. The model includes the strain hardening and strain rate hardening terms, and provides the stress-strain relations matching with the experimental results. Finite element simulations for the strain rates used in the experiments predict the mechanical responses of the material that agree well with the experimental data.

  18. Remodeling of Rural Public Service Supply Mechanism under the Background of New Village Construction

    Institute of Scientific and Technical Information of China (English)

    2011-01-01

    Under the background of new village construction, the necessity of remodeling the supply mechanism of rural public service is expounded. It is conducive to improving the capability of public service to satisfy farmers’ demand; to constructing a rural diversified public service system and improving the supply efficiency of rural public goods; to realizing the equalization of urban-rural public services to coordinate urban-rural development. Problems in the supply of Chinese rural public services are analyzed:the demand of rural public goods is enormous, governmental fiscal expenditure is insufficient; social organization is imperfect and public service capability is weak; urban-rural gap is large and the supply of pubic service is unequal; the system of rural public service is single and the functions are imperfect; the market degree of rural public service is low and the efficiency needs improving. In view of these problems, the strategies for remodeling the supply mechanism of rural public service are put forward, covering intensifying the input intensity of the government, expanding the coverage of public services; vigorously supporting the development of social organization and improving its capability of public goods; breaking through dual system and realizing the equalization of urban-rural public service; perfecting rural diversified public services and perfecting its public service functions; promoting the market progress of rural public services and improving the efficiency of public service.

  19. Testosterone and attention deficits as possible mechanisms underlying impaired emotion recognition in intimate partner violence perpetrators

    Directory of Open Access Journals (Sweden)

    Ángel Romero-Martínez

    2016-07-01

    Full Text Available Several studies have reported impairments in decoding emotional facial expressions in intimate partner violence (IPV perpetrators. However, the mechanisms that underlie these impaired skills are not well known. Given this gap in the literature, we aimed to establish whether IPV perpetrators (n = 18 differ in their emotion decoding process, attentional skills, and testosterone (T, cortisol (C levels and T/C ratio in comparison with controls (n = 20, and also to examine the moderating role of the group and hormonal parameters in the relationship between attention skills and the emotion decoding process. Our results demonstrated that IPV perpetrators showed poorer emotion recognition and higher attention switching costs than controls. Nonetheless,they did not differ in attention to detail and hormonal parameters. Finally, the slope predicting emotion recognition from deficits in attention switching became steeper as T levels increased, especially in IPV perpetrators, although the basal C and T/C ratios were unrelated to emotion recognition and attention deficits for both groups. These findings contribute to a better understanding of the mechanisms underlying emotion recognition deficits. These factors therefore constitute the target for future interventions.

  20. Temperature-dependent dynamic mechanical properties of magnetorheological elastomers under magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Ju, Benxiang, E-mail: jubenxiang@qq.com [National Instrument Functional Materials Engineering Technology Research Center, Chongqing 400707 (China); Tang, Rui; Zhang, Dengyou; Yang, Bailian [National Instrument Functional Materials Engineering Technology Research Center, Chongqing 400707 (China); Yu, Miao; Liao, Changrong [College of Optoelectronic Engineering, Chongqing University, Chongqing 400044 (China)

    2015-01-15

    Both anisotropic and isotropic magnetorheological elastomer (MRE) samples were fabricated by using as-prepared polyurethane (PU) matrix and carbonyl iron particles. Temperature-dependent dynamic mechanical properties of MRE were investigated and analyzed. Due to the unique structural features of as-prepared matrix, temperature has a greater impact on the properties of as-prepared MRE, especially isotropic MRE. With increasing of temperature and magnetic field, MR effect of isotropic MRE can reach up to as high as 4176.5% at temperature of 80 °C, and the mechanism of the temperature-dependent in presence of magnetic field was discussed. These results indicated that MRE is a kind of temperature-dependent material, and can be cycled between MRE and MR plastomer (MRP) by varying temperature. - Highlights: • Both anisotropic and isotropic MRE were fabricated by using as-prepared matrix. • Temperature-dependent properties of MRE under magnetic field were investigated. • As-prepared MRE can transform MRE to MRP by adjusting temperature.

  1. An overview of Italian participation in afforestation and reforestation projects under the Clean Development Mechanism

    Directory of Open Access Journals (Sweden)

    Corradini G

    2016-05-01

    Full Text Available In order to meet its Kyoto Protocol commitment targets, the Italian Government has made relevant investments in forest projects in developing countries through the Clean Development Mechanism. This paper investigates the Italian participated afforestation/reforestation (A/R projects under the Clean Development Mechanism of the Kyoto Protocol, by considering the countries hosting forestry projects, the project areas, the estimated emission reductions, the use of tree species (native/non-native, the issuance of Carbon credits, and the projects’ contribution to sustainable development and technology transfer in general, as stated by the “Project Design Document” of each project. This study utilizes the “Project Design Documents” and “Monitoring Reports” of the registered projects in the United Nations Convention on Climate Change database and data from the BioCarbon Fund database. Results show that, in terms of number of projects, the A/R sector is a prominent component of the Italian CDM portfolio. The financing of the 16 projects by the Italian government, with a total of about 65 k ha planted and an estimated emission reductions of about 556 k tCO2 eq per year, are based on criteria that differ substantially from the ongoing policy adopted for domestic forest interventions.

  2. The neuronal mechanisms underlying improvement of impulsivity in ADHD by theta/beta neurofeedback

    Science.gov (United States)

    Bluschke, Annet; Broschwitz, Felicia; Kohl, Simon; Roessner, Veit; Beste, Christian

    2016-01-01

    Neurofeedback is increasingly recognized as an intervention to treat core symptoms of attention deficit hyperactivity disorder (ADHD). Despite the large number of studies having been carried out to evaluate its effectiveness, it is widely elusive what neuronal mechanisms related to the core symptoms of ADHD are modulated by neurofeedback. 19 children with ADHD undergoing 8 weeks of theta/beta neurofeedback and 17 waiting list controls performed a Go/Nogo task in a pre-post design. We used neurophysiological measures combining high-density EEG recording with source localization analyses using sLORETA. Compared to the waiting list ADHD control group, impulsive behaviour measured was reduced after neurofeedback treatment. The effects of neurofeedback were very specific for situations requiring inhibitory control over responses. The neurophysiological data shows that processes of perceptual gating, attentional selection and resource allocation processes were not affected by neurofeedback. Rather, neurofeedback effects seem to be based on the modulation of response inhibition processes in medial frontal cortices. The study shows that specific neuronal mechanisms underlying impulsivity are modulated by theta/beta neurofeedback in ADHD. The applied neurofeedback protocol could be particularly suitable to address inhibitory control. The study validates assumed functional neuroanatomical target regions of an established neurofeedback protocol on a neurophysiological level. PMID:27514985

  3. Potent Activities of Roemerine against Candida albicans and the Underlying Mechanisms

    Directory of Open Access Journals (Sweden)

    Chaoyu Ma

    2015-09-01

    Full Text Available Roemerine (RM is an aporphine alkaloid isolated from the fresh rattan stem of Fibraurea recisa, and it has been demonstrated to have certain antifungal activity. This study aimed to investigate the antifungal activity of RM and the underlying mechanisms in Candida albicans (C. albicans. The in vitro antifungal activity of RM was evaluated by a series of experiments, including the XTT reduction assay, confocal laser scanning microscopy assay, scanning electron microscope assay. Results showed that 1 μg/mL RM inhibited biofilm formation significantly (p < 0.01 both in Spider medium and Lee’s medium. In addition, RM could inhibit yeast-to-hyphae transition of C. albicans in a dose-dependent manner. The biofilm-specific and hypha-specific genes such as YWP1, SAP5, SAP6, HWP1, ECE1 were up-regulated and EFG1 was down-regulated after 8 μg/mL RM treatment. Furthermore, the toxicity of RM was investigated using C. elegans worms, three cancer cells and one normal cell. The date showed that RM had no significant toxicity. In conclusion, RM could inhibited the formation of C. albicans biofilm in vitro, but it had no fungicidal effect on planktonic C. albicans cells, and the anti-biofilm mechanism may be related to the cAMP pathway.

  4. On the Nuclear Mechanisms Underlying the Heat Production by the E-Cat

    CERN Document Server

    Cook, Norman D

    2015-01-01

    We discuss the isotopic abundances found in the E-Cat reactor with regard to the nuclear mechanisms responsible for excess heat. We argue that a major source of energy is a reaction between the first excited-state of 7Li4 and a proton, followed by the breakdown of 8Be4 into two alphas with high kinetic energy, but without gamma radiation. The unusual property of the 7Li4 isotope that allows this reaction is similar to the property that underlies the Mossbauer effect: the presence of unusually low-lying excited states in stable, odd-Z and/or odd-N nuclei. We use the lattice version of the independent-particle model (IPM) of nuclear theory to show how the geometrical structure of isotopes indicate nuclear reactions that are not predicted in the conventional version of the IPM. Finally, we speculate on similar mechanisms that may be involved in other low-energy nuclear reactions (LENR).

  5. Mechanisms of the rapid dissolution of plutonium dioxide in acidic media under oxidizing or reducing conditions

    International Nuclear Information System (INIS)

    Until recently plutonium dioxide was known to be among the metallic oxides most difficult to dissolve. This property is understandable given the free energy of the dissolution reaction (ΔG0) in acidic noncomplexing media (ΔG0 = 32.04 kJ/mol). Thermodynamic calculations predict that PuO2 will dissolve under oxidizing or reducing conditions. The oxidizing dissolution, leading to Pu(VI) ion in solution, is easy to perform with a strong oxidant like Ag(II). The mechanism of the oxidizing dissolution of PuO2 was investigated by using carbon paste electrochemistry (CPE) and 18 O labeling. PuO2 can also be dissolved in acidic solution if the redox potential of the mixture is low (e.g., Cr2+, V2+, or U3+ as reducing agents). The kinetics of the heterogeneous reducing dissolution of PuO2 with Cr2+ were investigated and the reaction mechanism was determined by 18 O labeling. All the results will be presented and discussed in the context of minimizing the amount of plutonium-contaminated solid wastes in the nuclear fuel cycle. 9 figs., 17 refs

  6. Stress State Analysis and Failure Mechanisms of Masonry Columns Reinforced with FRP under Concentric Compressive Load

    Directory of Open Access Journals (Sweden)

    Jiří Witzany

    2016-04-01

    Full Text Available The strengthening and stabilization of damaged compressed masonry columns with composites based on fabrics of high-strength fibers and epoxy resin, or polymer-modified cement mixtures, belongs to novel, partially non-invasive and reversible progressive methods. The stabilizing and reinforcing effect of these fabrics significantly applies to masonry structures under concentric compressive loading whose failure mechanism is characterized by the appearance and development of vertical tensile cracks accompanied by an increase in horizontal masonry strain. During the appearance of micro and hairline cracks (10−3 to 10−1 mm, the effect of non-pre-stressed wrapping composite is very small. The favorable effect of passive wrapping is only intensively manifested after the appearance of cracks (10−1 mm and bigger at higher loading levels. In the case of “optimum” reinforcement of a masonry column, the experimental research showed an increase in vertical displacements δy (up to 247%, horizontal displacements δx (up to 742% and ultimate load-bearing capacity (up to 136% compared to the values reached in unreinforced masonry columns. In the case of masonry structures in which no intensive “bed joint filler–masonry unit” interaction occurs, e.g., in regular coursed masonry with little differences in the mechanical characteristics of masonry units and the binder, the reinforcing effect of the fabric applies only partially.

  7. Adverse effects from clenbuterol and ractopamine on nematode Caenorhabditis elegans and the underlying mechanism.

    Directory of Open Access Journals (Sweden)

    Ziheng Zhuang

    Full Text Available In the present study, we used Caenorhabditis elegans assay system to investigate in vivo toxicity from clentuberol and ractopamine and the possible underlying mechanism. Both acute and prolonged exposures to clentuberol or ractopamine decreased brood size and locomotion behavior, and induced intestinal autofluorescence and reactive oxygen species (ROS production. Although acute exposure to the examined concentrations of clentuberol or ractopamine did not induce lethality, prolonged exposure to 10 µg/L of clentuberol and ractopamine reduced lifespan. At relatively high concentrations, ractopamine exhibited more severe toxicity than clentuberol on nematodes. Overexpression of sod-2 gene encoding a Mn-SOD to prevent induction of oxidative stress effectively inhibited toxicity from clentuberol or ractopamine. Besides oxidative stress, we found that clentuberol might reduce lifespan through influencing insulin/IGF signaling pathway; however, ractopamine might reduce lifespan through affecting both insulin/IGF signaling pathway and TOR signaling pathway. Ractopamine more severely decreased expression levels of daf-16, sgk-1, skn-1, and aak-2 genes than clentuberol, and increased expression levels of daf-2 and age-1 genes at the examined concentration. Therefore, the C. elegans assay system may be useful for assessing the possible toxicity from weight loss agents, and clentuberol and ractopamine may induce toxicity through different molecular mechanisms.

  8. Distinct Subthreshold Mechanisms Underlying Rate-Coding Principles in Primate Auditory Cortex.

    Science.gov (United States)

    Gao, Lixia; Kostlan, Kevin; Wang, Yunyan; Wang, Xiaoqin

    2016-08-17

    A key computational principle for encoding time-varying signals in auditory and somatosensory cortices of monkeys is the opponent model of rate coding by two distinct populations of neurons. However, the subthreshold mechanisms that give rise to this computation have not been revealed. Because the rate-coding neurons are only observed in awake conditions, it is especially challenging to probe their underlying cellular mechanisms. Using a novel intracellular recording technique that we developed in awake marmosets, we found that the two types of rate-coding neurons in auditory cortex exhibited distinct subthreshold responses. While the positive-monotonic neurons (monotonically increasing firing rate with increasing stimulus repetition frequency) displayed sustained depolarization at high repetition frequency, the negative-monotonic neurons (opposite trend) instead exhibited hyperpolarization at high repetition frequency but sustained depolarization at low repetition frequency. The combination of excitatory and inhibitory subthreshold events allows the cortex to represent time-varying signals through these two opponent neuronal populations. PMID:27478016

  9. STUDIES ON THE PORE FORMATION MECHANISM OF β-CRYSTALLINE POLYPROPYLENE UNDER STRETCHING

    Institute of Scientific and Technical Information of China (English)

    Shao-feng Ran; Mao Xu

    2004-01-01

    The pore formation mechanism of β-crystalline polypropylene under stretching was investigated. The porosity of the samples increases rapidly with stretching, having a maximum at draw ratios around 2 and then decreases monotonically.An abrupt formation process of initial micropores at very low draw ratios was evidenced by in situ SAXS measurements. At the same time the phase transition from β-crystal to a-crystal proceeds slowly in the whole deformation process up to large draw ratios around 5. Comparative studies of a- and β-crystalline polypropylene samples before stretching indicate that in addition to difference in crystal forms the a- and β-crystalline polypropylene samples exhibit quite different morphological features. There are a lot of interfaces in β-crystalline polypropylene samples, which may have a lower density value and can be easily etched by argon ions and penetrated by small molecules. It was concluded from these experimental facts that the pore formation and crystal transition are two independent phenomena during the deformation of β-crystalline polypropylene samples, and phase transition from β-crystal to a-crystal could hardly be the origin of pore formation. A defect initiation mechanism was proposed to understand the pore formation behavior of β-crystalline polypropylenes.

  10. A connectionist modeling study of the neural mechanisms underlying pain's ability to reorient attention.

    Science.gov (United States)

    Dowman, Robert; Ritz, Benjamin; Fowler, Kathleen

    2016-08-01

    Connectionist modeling was used to investigate the brain mechanisms responsible for pain's ability to shift attention away from another stimulus modality and toward itself. Different connectionist model architectures were used to simulate the different possible brain mechanisms underlying this attentional bias, where nodes in the model simulated the brain areas thought to mediate the attentional bias, and the connections between the nodes simulated the interactions between the brain areas. Mathematical optimization techniques were used to find the model parameters, such as connection strengths, that produced the best quantitative fits of reaction time and event-related potential data obtained in our previous work. Of the several architectures tested, two produced excellent quantitative fits of the experimental data. One involved an unexpected pain stimulus activating somatic threat detectors in the dorsal posterior insula. This threat detector activity was monitored by the medial prefrontal cortex, which in turn evoked a phasic response in the locus coeruleus. The locus coeruleus phasic response resulted in a facilitation of the cortical areas involved in decision and response processes time-locked to the painful stimulus. The second architecture involved the presence of pain causing an increase in general arousal. The increase in arousal was mediated by locus coeruleus tonic activity, which facilitated responses in the cortical areas mediating the sensory, decision, and response processes involved in the task. These two neural network architectures generated competing predictions that can be tested in future studies. PMID:27112345

  11. The neuronal mechanisms underlying improvement of impulsivity in ADHD by theta/beta neurofeedback.

    Science.gov (United States)

    Bluschke, Annet; Broschwitz, Felicia; Kohl, Simon; Roessner, Veit; Beste, Christian

    2016-01-01

    Neurofeedback is increasingly recognized as an intervention to treat core symptoms of attention deficit hyperactivity disorder (ADHD). Despite the large number of studies having been carried out to evaluate its effectiveness, it is widely elusive what neuronal mechanisms related to the core symptoms of ADHD are modulated by neurofeedback. 19 children with ADHD undergoing 8 weeks of theta/beta neurofeedback and 17 waiting list controls performed a Go/Nogo task in a pre-post design. We used neurophysiological measures combining high-density EEG recording with source localization analyses using sLORETA. Compared to the waiting list ADHD control group, impulsive behaviour measured was reduced after neurofeedback treatment. The effects of neurofeedback were very specific for situations requiring inhibitory control over responses. The neurophysiological data shows that processes of perceptual gating, attentional selection and resource allocation processes were not affected by neurofeedback. Rather, neurofeedback effects seem to be based on the modulation of response inhibition processes in medial frontal cortices. The study shows that specific neuronal mechanisms underlying impulsivity are modulated by theta/beta neurofeedback in ADHD. The applied neurofeedback protocol could be particularly suitable to address inhibitory control. The study validates assumed functional neuroanatomical target regions of an established neurofeedback protocol on a neurophysiological level. PMID:27514985

  12. Mechanism Underlying Protective Effect of Danbiqing Granule on Experimental Acute Bacterial Cholangitis in Rabbits

    Institute of Scientific and Technical Information of China (English)

    LINXiu-zhen; GONGYan-ling; WANGHong-bo

    2003-01-01

    Aim To study the mechanism of protective effects of Danbiqing granule (DBQ) on experimental acute bacterial cholangitis in rabbits. Methods The acute bacterial cholangitis was induced by injecting 1 mL of 1 × l03 cuf·mL-1 Escherchia coli suspension into common bile duit. The serum nitrous oxide (NO) levels were measured using nitric acid reductase kit. Phospholipase A2 (PLA2) activity was assayed by a method of acid titration (microassay). Serum tumor necrosis factor-α (TNF-α), inferleukin-6 (IL-6) and plasma thromboxane B2 ( TXB2 ), 6-keto-platelet growth factor 1(PGF1α) were determined by radioimmunoassay. Results Compared with control group, serum NO, PLA2, TNF-α, IL-6 and plasma TXB2 levels increased significantly in model group ( P < 0.01) while those of DBQ groutm decreased significantly( P < 0.01). Conclusion DBQ dramatically inhibits the overproduction of pro-inflammatory factor PLA2 and inflammatory cytokine. Hence, the mechanism of DBQ underlying anti-inflammatory and protective effect against acute bacterial cholangitis in rabbits has been revealed.

  13. Mechanical behaviors and damage constitutive model of ceramics under shock compression

    Institute of Scientific and Technical Information of China (English)

    Jianguo Ning; Huilan Ren; Ping Li

    2008-01-01

    One-stage light gas gun was utilized to study the dynamic mechanical properties of AD90 alumina subjected to the shock loading. Manganin gauges were adopted to obtain the stress-time histories. The velocity interferometer system for any reflector (VISAR) was used to obtain the free surface velocity profile and determine the Hugoniot elastic limit. The Hugoniot curves were fitted with the experimental data. From Hugoniot curves the compressive behaviors of AD90 alumina were found to change typically from elastic to "plastic". The dynamic mechanical behaviors for alumina under impact loadings were analyzed by using the path line principle of Lagrange analysis, including the nonlinear characteristics, the strain rate dependence, the dispersion and declination of shock wave in the material. A damage model applicable to ceramics subjected to dynamic compressive loading has been developed. The model was based on the damage micromechanics and wing crack nucleation and growth. The effects of parameters of both the micro-cracks nucleation and the initial crack size on the dynamic fracture strength were discussed. The results of the dynamic damage evolution model were compared with the experimental results and a good agreement was found.

  14. Reaction Mechanism Underlying Atomic Layer Deposition of Antimony Telluride Thin Films.

    Science.gov (United States)

    Han, Byeol; Kim, Yu-Jin; Park, Jae-Min; Yusup, Luchana L; Ishii, Hana; Lansalot-Matras, Clement; Lee, Won-Jun

    2016-05-01

    The mechanism underlying the deposition of SbTe films by alternating exposures to Sb(NMe2)3 and Te(GeMe3)2 was investigated. Sb(NMe2)3 and Te(GeMe3)2 were selected because they have very high vapor pressure and are free of Si, Cl, and O atoms in the molecules. The mechanism of deposition was proposed by density functional theory (DFT) calculation and was verified by in-situ quartz crystal microbalance (QCM) analysis. DFT calculation expected the ligand-exchange reactions between the Sb and Te precursors to form Me2NGeMe3 as the byproduct. QCM analysis indicated that a single -NMe2 group in Sb(NMe2)3 reacts with -TeGeMe3 on the surface to form an Sb2Te3 film, and that a small fraction of Sb is incorporated into the film by the thermal decomposition of Sb(NMe2)3. The Te(GeMe3)2 molecules were thermally stable up to 120 degrees C, while the Sb(NMe2)3 molecules decomposed at temperatures of 60 degrees C and higher. Sb-rich SbTe films with different Sb contents were prepared by controlling the partial decomposition of Sb(NMe2)3 molecules, which was enhanced by increasing the pulse time of the precursor. PMID:27483847

  15. Laboratory and 3-D-distinct element analysis of failure mechanism of slope under external surcharge

    Directory of Open Access Journals (Sweden)

    N. Li

    2014-09-01

    Full Text Available Landslide is a major disaster resulting in considerable loss of human lives and property damages in hilly terrain in Hong Kong, China and many other countries. The factor of safety and the critical slip surface for slope stabilization are the main considerations for slope stability analysis in the past, while the detailed post-failure conditions of the slopes have not been considered in sufficient details. There are however increasing interest on the consequences after the initiation of failure which includes the development and propagation of the failure surfaces, the amount of failed mass and runoff and the affected region. To assess the development of slope failure in more details and to consider the potential danger of slopes after failure has initiated, the slope stability problem under external surcharge is analyzed by the distinct element method (DEM and laboratory model test in the present research. A more refined study about the development of failure, microcosmic failure mechanism and the post-failure mechanism of slope will be carried out. The numerical modeling method and the various findings from the present work can provide an alternate method of analysis of slope failure which can give additional information not available from the classical methods of analysis.

  16. Potent Activities of Roemerine against Candida albicans and the Underlying Mechanisms.

    Science.gov (United States)

    Ma, Chaoyu; Du, Faya; Yan, Lan; He, Gonghao; He, Jianchang; Wang, Chengying; Rao, Gaoxiong; Jiang, Yuanying; Xu, Guili

    2015-01-01

    Roemerine (RM) is an aporphine alkaloid isolated from the fresh rattan stem of Fibraurea recisa, and it has been demonstrated to have certain antifungal activity. This study aimed to investigate the antifungal activity of RM and the underlying mechanisms in Candida albicans (C. albicans). The in vitro antifungal activity of RM was evaluated by a series of experiments, including the XTT reduction assay, confocal laser scanning microscopy assay, scanning electron microscope assay. Results showed that 1 μg/mL RM inhibited biofilm formation significantly (p albicans in a dose-dependent manner. The biofilm-specific and hypha-specific genes such as YWP1, SAP5, SAP6, HWP1, ECE1 were up-regulated and EFG1 was down-regulated after 8 μg/mL RM treatment. Furthermore, the toxicity of RM was investigated using C. elegans worms, three cancer cells and one normal cell. The date showed that RM had no significant toxicity. In conclusion, RM could inhibited the formation of C. albicans biofilm in vitro, but it had no fungicidal effect on planktonic C. albicans cells, and the anti-biofilm mechanism may be related to the cAMP pathway.

  17. Investigating mechanisms underlying neurodevelopmental phenotypes of autistic and intellectual disability disorders: a perspective

    Directory of Open Access Journals (Sweden)

    Tim eKroon

    2013-10-01

    Full Text Available Brain function and behaviour undergo significant plasticity and refinement, particularly during specific critical and sensitive periods. In autistic and intellectual disability neurodevelopmental disorders (NDDs and their corresponding genetic mouse models, impairments in many neuronal and behavioural phenotypes are temporally regulated and in some cases, transient. However, the links between neurobiological mechanisms governing typically normal brain and behavioural development (referred to also as ‘neurotypical’ development and timing of NDD impairments are not fully investigated.This perspective highlights temporal patterns of synaptic and neuronal impairment, with a restricted focus on autism and intellectual disability types of NDDs. Given the varying known genetic and environmental causes for NDDs, this perspective proposes two strategies for investigation: (1 a focus on neurobiological mechanisms underlying known critical periods in the (typically normal-developing brain (2 investigation of spatio-temporal expression profiles of genes implicated in monogenic syndromes throughout affected brain regions.This approach may help explain why many NDDs with differing genetic causes can result in overlapping phenotypes at similar developmental stages and better predict vulnerable periods within these disorders, with implications for both therapeutic rescue and ultimately, prevention.

  18. Mechanisms of the rapid dissolution of plutonium dioxide in acidic media under oxidizing or reducing conditions

    International Nuclear Information System (INIS)

    Until recently plutonium dioxide was known to be among the metallic oxides most difficult to dissolve. This property is understandable given the free energy of the dissolution reaction (ΔG0) in acidic noncomplexing media (ΔG0 = 32.04 kJ/mol). Thermodynamic calculations predict that PuO2 will dissolve under oxidizing or reducing conditions. The oxidizing dissolution, leading to Pu(VI) ion in solution, is easy to perform with a strong oxidant like Ag(II). The mechanism of the oxidizing dissolution of PuO2 was investigated by using carbon paste electrochemistry (CPE) and 18O labeling. PuO2 can also be dissolved in acidic solution if the redox potential of the mixture is low (e.g., Cr2+, V2+, or U3+ as reducing agents). The kinetics of the heterogeneous reducing dissolution of PuO2 with Cr2+ were investigated and the reaction mechanism was determined by 18O labeling. In this paper all the results are presented and discussed in the context of minimizing the amount of plutonium-contaminated solid wastes in the nuclear fuel cycle

  19. Effects of fatigue on microstructure and mechanical properties of bone organic matrix under compression

    International Nuclear Information System (INIS)

    The aim of the study was to investigate whether a fatigue induced weakening of cortical bone was revealed in microstructure and mechanical competence of demineralized bone matrix. Two types of cortical bone samples (plexiform and Haversian) were use. Bone slabs from the midshaft of bovine femora were subjected to cyclical bending. Fatigued and adjacent control samples were cut into cubes and demineralized in ethylenediaminetetraacetic acid. Demineralized samples were either subjected to microscopic quantitative image analysis, or compressed to failure (in longitudinal or transverse direction) with a simultaneous analysis of acoustic emission (AE). In fatigued samples porosity of organic matrix and average area of pores have risen, along with a change in the pores shape. The effect of fatigue depended on the type of the bone, being more pronounced in the plexiform than in Haversian tissue. Demineralized bone matrix was anisotropic under compressive loads in both types of cortical structure. The main result of fatigue pretreatment on mechanical parameters was a significant decrease of ultimate strain in the transverse direction in plexiform samples. The decrease of strain in this group was accompanied by a considerable increase of the fraction of large pores and a significant change in AE energy.

  20. Mechanisms underlying syntactic comprehension deficits in vascular aphasia: new evidence from self-paced listening.

    Science.gov (United States)

    Caplan, David; Michaud, Jennifer; Hufford, Rebecca

    2015-01-01

    Sixty-one people with aphasia (pwa) and 41 matched controls were tested for the ability to understand sentences that required the ability to process particular syntactic elements and assign particular syntactic structures. Participants paced themselves word-by-word through 20 examples of 11 spoken sentence types and indicated which of two pictures corresponded to the meaning of each sentence. Sentences were developed in pairs such that comprehension of the experimental version of a pair required an aspect of syntactic processing not required in the corresponding baseline sentence. The need for the syntactic operations required only in the experimental version was triggered at a "critical word" in the experimental sentence. Listening times for critical words in experimental sentences were compared to those for corresponding words in the corresponding baseline sentences. The results were consistent with several models of syntactic comprehension deficits in pwa: resource reduction, slowed lexical and/or syntactic processing, abnormal susceptibility to interference from thematic roles generated non-syntactically. They suggest that a previously unidentified disturbance limiting the duration of parsing and interpretation may lead to these deficits, and that this mechanism may lead to structure-specific deficits in pwa. The results thus point to more than one mechanism underlying syntactic comprehension disorders both across and within pwa. PMID:26165856