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Sample records for additive mechanisms impair

  1. Two additive mechanisms impair the differentiation of 'substrate-selective' p38 inhibitors from classical p38 inhibitors in vitro

    Seidl Kelly M

    2010-03-01

    Full Text Available Abstract Background The success of anti-TNF biologics for the treatment of rheumatoid arthritis has highlighted the importance of understanding the intracellular pathways that regulate TNF production in the quest for an orally-available small molecule inhibitor. p38 is known to strongly regulate TNF production via MK2. The failure of several p38 inhibitors in the clinic suggests the importance of other downstream pathways in normal cell function. Recent work has described a 'substrate-selective' p38 inhibitor that is able to preferentially block the activity of p38 against one substrate (MK2 versus another (ATF2. Using a combined experimental and computational approach, we have examined this mechanism in greater detail for two p38 substrates, MK2 and ATF2. Results We found that in a dual (MK2 and ATF2 substrate assay, MK2-p38 interaction reduced the activity of p38 against ATF2. We further constructed a detailed kinetic mechanistic model of p38 phosphorylation in the presence of multiple substrates and successfully predicted the performance of classical and so-called 'substrate-selective' p38 inhibitors in the dual substrate assay. Importantly, it was found that excess MK2 results in a stoichiometric effect in which the formation of p38-MK2-inhibitor complex prevents the phosphorylation of ATF2, despite the preference of the compound for the p38-MK2 complex over the p38-ATF2 complex. MK2 and p38 protein expression levels were quantified in U937, Thp-1 and PBMCs and found that [MK2] > [p38]. Conclusion Our integrated mechanistic modeling and experimental validation provides an example of how systems biology approaches can be applied to drug discovery and provide a basis for decision-making with limited chemical matter. We find that, given our current understanding, it is unlikely that 'substrate-selective' inhibitors of p38 will work as originally intended when placed in the context of more complex cellular environments, largely due to a

  2. Identification of Additional Learning Difficulties in Hearing-Impaired Children.

    Alpin, D. Yvonne

    Of particular concern to educational psychologists when assessing hearing-impaired children is the identification of learning difficulties in addition to deafness which might hinder progress with language development. This study sought to replicate research which showed that some deaf children who have difficulty with fine motor movements and body…

  3. Primary circuit iodine model addition to IMPAIR-3

    As part of a continuing effort to provide the U.S. Department of Energy (DOE) Advanced Reactor Severe Accident Program (ARSAP) with complete iodine analysis capability, a task was undertaken to expand the modeling of IMPAIR-3, an iodine chemistry code. The expanded code will enable the DOE to include detailed iodine behavior in the assessment of severe accident source terms used in the licensing of U.S. Advanced Light Water Reactors (ALWRs). IMPAIR-3 was developed at the Paul Scherrer Institute (PSI), Switzerland, and has been used by ARSAP for the past two years to analyze containment iodine chemistry for ALWR source term analyses. IMPAIR-3 is primarily a containment code but the iodine chemistry inside the primary circuit (the Reactor Coolant System or RCS) may influence the iodine species released into the the containment; therefore, a RCS iodine chemistry model must be implemented in IMPAIR-3 to ensure thorough source term analysis. The ARSAP source term team and the PSI IMPAIR-3 developers are working together to accomplish this task. This cooperation is divided into two phases. Phase I, taking place in 1996, involves developing a stand-alone RCS iodine chemistry program called IMPRCS (IMPAIR -Reactor Coolant System). This program models a number of the chemical and physical processes of iodine that are thought to be important at conditions of high temperature and pressure in the RCS. In Phase II, which is tentatively scheduled for 1997, IMPRCS will be implemented as a subroutine in IMPAIR-3. To ensure an efficient calculation, an interface/tracking system will be developed to control the use of the RCS model from the containment model. These two models will be interfaced in such a way that once the iodine is released from the RCS, it will no longer be tracked by the RCS model but will be tracked by the containment model. All RCS thermal-hydraulic parameters will be provided by other codes. (author) figs., tabs., refs

  4. Primary circuit iodine model addition to IMPAIR-3

    Osetek, D.J.; Louie, D.L.Y. [Los Alamos Technical Associates, Inc., Albuquerque, NM (United States); Guntay, S.; Cripps, R. [Paul Scherrer Inst. (PSI), Villigen (Switzerland)

    1996-12-01

    As part of a continuing effort to provide the U.S. Department of Energy (DOE) Advanced Reactor Severe Accident Program (ARSAP) with complete iodine analysis capability, a task was undertaken to expand the modeling of IMPAIR-3, an iodine chemistry code. The expanded code will enable the DOE to include detailed iodine behavior in the assessment of severe accident source terms used in the licensing of U.S. Advanced Light Water Reactors (ALWRs). IMPAIR-3 was developed at the Paul Scherrer Institute (PSI), Switzerland, and has been used by ARSAP for the past two years to analyze containment iodine chemistry for ALWR source term analyses. IMPAIR-3 is primarily a containment code but the iodine chemistry inside the primary circuit (the Reactor Coolant System or RCS) may influence the iodine species released into the the containment; therefore, a RCS iodine chemistry model must be implemented in IMPAIR-3 to ensure thorough source term analysis. The ARSAP source term team and the PSI IMPAIR-3 developers are working together to accomplish this task. This cooperation is divided into two phases. Phase I, taking place in 1996, involves developing a stand-alone RCS iodine chemistry program called IMPRCS (IMPAIR -Reactor Coolant System). This program models a number of the chemical and physical processes of iodine that are thought to be important at conditions of high temperature and pressure in the RCS. In Phase II, which is tentatively scheduled for 1997, IMPRCS will be implemented as a subroutine in IMPAIR-3. To ensure an efficient calculation, an interface/tracking system will be developed to control the use of the RCS model from the containment model. These two models will be interfaced in such a way that once the iodine is released from the RCS, it will no longer be tracked by the RCS model but will be tracked by the containment model. All RCS thermal-hydraulic parameters will be provided by other codes. (author) figs., tabs., refs.

  5. Type 2 diabetes and cognitive impairment: linking mechanisms

    Luchsinger, José A.

    2012-01-01

    This manuscript provides a brief review of current concepts in the mechanisms potentially linking type-2-diabetes (T2D) with cognitive impairment. Existing epidemiologic studies, imaging studies, autopsy studies and clinical trials provide insights into the mechanisms linking T2D and cognitive impairment. There seems to be little dispute that T2D can cause cerebrovascular disease and thus cause vascular cognitive impairment (VCI). Whether T2D can cause late onset Alzheimer’s disease (LOAD) re...

  6. The Impaired Physician: Some Coping Mechanisms

    Nicholson, J. F.

    1980-01-01

    Doctoring is a stressful way of life. Both normal and neurotic needs can increase the complexity of the family physician's life. Certain vulnerable doctors seek easement in tranquilizers, sedatives or alcohol, and can become addicted. Impairment may be episodic or steady, leading to deterioration in personality and ability

  7. Mechanical Properties of Additively Manufactured Thick Honeycombs

    Reza Hedayati

    2016-07-01

    Full Text Available Honeycombs resemble the structure of a number of natural and biological materials such as cancellous bone, wood, and cork. Thick honeycomb could be also used for energy absorption applications. Moreover, studying the mechanical behavior of honeycombs under in-plane loading could help understanding the mechanical behavior of more complex 3D tessellated structures such as porous biomaterials. In this paper, we study the mechanical behavior of thick honeycombs made using additive manufacturing techniques that allow for fabrication of honeycombs with arbitrary and precisely controlled thickness. Thick honeycombs with different wall thicknesses were produced from polylactic acid (PLA using fused deposition modelling, i.e., an additive manufacturing technique. The samples were mechanically tested in-plane under compression to determine their mechanical properties. We also obtained exact analytical solutions for the stiffness matrix of thick hexagonal honeycombs using both Euler-Bernoulli and Timoshenko beam theories. The stiffness matrix was then used to derive analytical relationships that describe the elastic modulus, yield stress, and Poisson’s ratio of thick honeycombs. Finite element models were also built for computational analysis of the mechanical behavior of thick honeycombs under compression. The mechanical properties obtained using our analytical relationships were compared with experimental observations and computational results as well as with analytical solutions available in the literature. It was found that the analytical solutions presented here are in good agreement with experimental and computational results even for very thick honeycombs, whereas the analytical solutions available in the literature show a large deviation from experimental observation, computational results, and our analytical solutions.

  8. Mechanical properties of additively manufactured octagonal honeycombs.

    Hedayati, R; Sadighi, M; Mohammadi-Aghdam, M; Zadpoor, A A

    2016-12-01

    Honeycomb structures have found numerous applications as structural and biomedical materials due to their favourable properties such as low weight, high stiffness, and porosity. Application of additive manufacturing and 3D printing techniques allows for manufacturing of honeycombs with arbitrary shape and wall thickness, opening the way for optimizing the mechanical and physical properties for specific applications. In this study, the mechanical properties of honeycomb structures with a new geometry, called octagonal honeycomb, were investigated using analytical, numerical, and experimental approaches. An additive manufacturing technique, namely fused deposition modelling, was used to fabricate the honeycomb from polylactic acid (PLA). The honeycombs structures were then mechanically tested under compression and the mechanical properties of the structures were determined. In addition, the Euler-Bernoulli and Timoshenko beam theories were used for deriving analytical relationships for elastic modulus, yield stress, Poisson's ratio, and buckling stress of this new design of honeycomb structures. Finite element models were also created to analyse the mechanical behaviour of the honeycombs computationally. The analytical solutions obtained using Timoshenko beam theory were close to computational results in terms of elastic modulus, Poisson's ratio and yield stress, especially for relative densities smaller than 25%. The analytical solutions based on the Timoshenko analytical solution and the computational results were in good agreement with experimental observations. Finally, the elastic properties of the proposed honeycomb structure were compared to those of other honeycomb structures such as square, triangular, hexagonal, mixed, diamond, and Kagome. The octagonal honeycomb showed yield stress and elastic modulus values very close to those of regular hexagonal honeycombs and lower than the other considered honeycombs. PMID:27612831

  9. UV radiation impairs the body's defence mechanism

    Ultraviolet (UV) radiation is usually divided into three wavelength ranges, which differ considerably from each other with respect to their effect on human health. UV-B radiation, in particular, weakens the body's resistance against cancer cells and thus increases cancer risk. Although virtually all UV-B radiation stops at the surface layer of skin, the whole body suffers from its adverse effects. UV radiation affects the body's defence mechanism relatively quickly. A reduction in the body's capacity to defend itself against alien substances can already be detected within a couple of days after the body has been exposed to a small amount of UV radiation. The risk of cancer increases slowly over the years. The skin cancers that are treated in hospitals today have their origin in the ways of life pursued in the 1960's and 70's. Factors affecting the amounts of UV doses received by Finns include trips to the South, solarium treatments and, to some extent, thinning of the ozone layer. (orig.) (4 figs.)

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

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

    2008-01-01

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

  11. Additive strengthening mechanisms in dispersion hardened polycrystals

    Hansen, Niels; Ralph, B.

    1986-01-01

    the addition of strength components from various elements of the microstructure and substructure might explain this behaviour are investigated. It is shown that a linear combination of a matrix friction stress, an Orowan bowing stress, a matrix mean stress from the particles and a combined dislocation...... the dislocation density contributions from each of these three sources. The type of additivity suggested here not only gives very good agreement with the stress-strain data but it also uses and is in accord with the experimental measurements of dislocation densities made using transmission electron...

  12. Designing Location-Based Learning Experiences for People with Intellectual Disabilities and Additional Sensory Impairments

    Brown, David J.; McHugh, David; Standen, Penny; Evett, Lindsay; Shopland, Nick; Battersby, Steven

    2011-01-01

    The research reported here is part of a larger project which seeks to combine serious games (or games-based learning) with location-based services to help people with intellectual disabilities and additional sensory impairments to develop work based skills. Specifically this paper reports on where these approaches are combined to scaffold the…

  13. Does visual impairment lead to additional disability in adults with intellectual disabilities?

    Sjoukes, L.; Koot, H. M.; Kooijman, A. C.; Evenhuis, H.

    2009-01-01

    This study addresses the question to what extent visual impairment leads to additional disability in adults with intellectual disabilities (ID). In a multi-centre cross-sectional study of 269 adults with mild to profound ID, social and behavioural functioning was assessed with observant-based questi

  14. Does Visual Impairment Lead to Additional Disability in Adults with Intellectual Disabilities?

    Evenhuis, Heleen M.; Sjoukes, L.; Koot, H. M.; Kooijman, A. C.

    2009-01-01

    Background: This study addresses the question to what extent visual impairment leads to additional disability in adults with intellectual disabilities (ID). Method: In a multi-centre cross-sectional study of 269 adults with mild to profound ID, social and behavioural functioning was assessed with observant-based questionnaires, prior to expert…

  15. Rehabilitation of stroke patients with apraxia: the role of additional cognitive and motor impairments.

    Heugten, C.M. van; Dekker, J.; Deelman, B.G.; Stehmann-Saris, J.C.; Kinebanian, A.

    2000-01-01

    PURPOSE: The present study investigated which additional cognitive and motor impairments were present in stroke patients with apraxia and which of these factors influenced the effects of treatment. METHOD: A group of 33 patients with apraxia were treated according to the guidelines of a therapy prog

  16. Rehabilitation of stroke patients with apraxia : the role of additional cognitive and motor impairments

    van Heugten, CM; Dekker, J; Deelman, BG; Stehmann-Saris, JC; Kinebanian, A

    2000-01-01

    Purpose : The present study investigated which additional cognitive and motor impairments were present in stroke patients with apraxia and which of these factors influenced the effects of treatment. Method: A group of 33 patients with apraxia were treated according to the guidelines of a therapy pro

  17. Rehabilitation of stroke patients with apraxia: the role of additional cognitive and motor impairments.

    van Heugten, C.M.; Dekker, J; Deelman, B.G.; Stehmann-Saris, J.C.; Kinebanian, A.

    2000-01-01

    PURPOSE: The present study investigated which additional cognitive and motor impairments were present in stroke patients with apraxia and which of these factors influenced the effects of treatment. METHOD: A group of 33 patients with apraxia were treated according to the guidelines of a therapy programme based on teaching patients strategies to compensate for the presence of apraxia. Patients were treated at occupational therapy departments in general hospitals, rehabilitation centres and nur...

  18. Additively homomorphic encryption with a double decryption mechanism, revisited

    Peter, A.; Kronberg, M.; Trei, W.; Katzenbeisser, S.

    2012-01-01

    We revisit the notion of additively homomorphic encryption with a double decryption mechanism (DD-PKE), which allows for additions in the encrypted domain while having a master decryption procedure that can decrypt all properly formed ciphertexts by using a special master secret. This type of encryp

  19. Mechanical Properties of Iron Alumininides Intermetallic Alloy with Molybdenum Addition

    In this work, FeAl-based alloys with and without molybdenum addition were fabricated by sintering of mechanically alloyed powders in order to investigate the effect of molybdenum on iron aluminide mechanical properties. Bulk samples were prepared by mechanical alloying for 4 hours, pressing at 360 MPa and sintering at 1000 deg. C for 2 hours. The specimens were tested in compression at room temperature using Instron machine. The phase identification and microstructure of the consolidated material was examined by x-ray diffraction and scanning electron microscope correspondingly. Results show that 2.5 wt%Mo addition significantly increased the ultimate stress and ultimate strain in compressive mode due to solid solution hardening. However, the addition of Mo more than 2.5 wt% was accompanied by a reduction in both properties caused by the presence of Mo-rich precipitate particles.

  20. Cognitive Control of Emotional Information in Schizophrenia: Understanding the Mechanisms of Social Functioning Impairments

    Tully, Laura Magdalen

    2013-01-01

    Social functioning impairments are a core, debilitating, and treatment refractory feature of schizophrenia. The mechanisms contributing to these impairments are unknown. Cognitive control mechanisms, mediated by the lateral prefrontal cortex (LPFC), are known to influence response to interpersonal stressors in healthy individuals, thus impairments in these processes may contribute to social deficits. Deficits in cognitive control and lateral prefrontal abnormalities are well-documented in sch...

  1. Metal Additive Manufacturing: A Review of Mechanical Properties

    Lewandowski, John J.; Seifi, Mohsen

    2016-07-01

    This article reviews published data on the mechanical properties of additively manufactured metallic materials. The additive manufacturing techniques utilized to generate samples covered in this review include powder bed fusion (e.g., EBM, SLM, DMLS) and directed energy deposition (e.g., LENS, EBF3). Although only a limited number of metallic alloy systems are currently available for additive manufacturing (e.g., Ti-6Al-4V, TiAl, stainless steel, Inconel 625/718, and Al-Si-10Mg), the bulk of the published mechanical properties information has been generated on Ti-6Al-4V. However, summary tables for published mechanical properties and/or key figures are included for each of the alloys listed above, grouped by the additive technique used to generate the data. Published values for mechanical properties obtained from hardness, tension/compression, fracture toughness, fatigue crack growth, and high cycle fatigue are included for as-built, heat-treated, and/or HIP conditions, when available. The effects of test orientation/build direction on properties, when available, are also provided, along with discussion of the potential source(s) (e.g., texture, microstructure changes, defects) of anisotropy in properties. Recommendations for additional work are also provided.

  2. Mechanical Properties of Austenitic Stainless Steel Made by Additive Manufacturing.

    Luecke, William E; Slotwinski, John A

    2014-01-01

    Using uniaxial tensile and hardness testing, we evaluated the variability and anisotropy of the mechanical properties of an austenitic stainless steel, UNS S17400, manufactured by an additive process, selective laser melting. Like wrought materials, the mechanical properties depend on the orientation introduced by the processing. The recommended stress-relief heat treatment increases the tensile strength, reduces the yield strength, and decreases the extent of the discontinuous yielding. The mechanical properties, assessed by hardness, are very uniform across the build plate, but the stress-relief heat treatment introduced a small non-uniformity that had no correlation to position on the build plate. Analysis of the mechanical property behavior resulted in four conclusions. (1) The within-build and build-to-build tensile properties of the UNS S17400 stainless steel are less repeatable than mature engineering structural alloys, but similar to other structural alloys made by additive manufacturing. (2) The anisotropy of the mechanical properties of the UNS S17400 material of this study is larger than that of mature structural alloys, but is similar to other structural alloys made by additive manufacturing. (3) The tensile mechanical properties of the UNS S17400 material fabricated by selective laser melting are very different from those of wrought, heat-treated 17-4PH stainless steel. (4) The large discontinuous yielding strain in all tests resulted from the formation and propagation of Lüders bands. PMID:26601037

  3. Angiography for renal artery stenosis: no additional impairment of renal function by angioplasty

    Lufft, Volkmar; Fels, Lueder M.; Egbeyong-Baiyee, Daniel; Olbricht, Christoph J. [Abteilung Nephrologie, Medizinische Hochschule Hannover (Germany); Hoogestraat-Lufft, Linda; Galanski, Michael [Abteilung Diagnostische Radiologie, Medizinische Hochschule Hannover (Germany)

    2002-04-01

    The aim of this study was to compare renal function between patients with renal angiography and patients with renal angiography and angioplasty (AP) for renal artery stenosis (RAS). Forty-seven patients with suspected RAS were prospectively investigated by digital subtraction angiography (DSA) using non-ionic low osmolar contrast media (CM). In 22 patients RAS was detected and in 16 cases an angioplasty was performed in the same session. The following parameters were determined 1 day prior to and after the DSA, respectively: serum creatinine (S-Crea, {mu}mol/l) and single-shot inulin clearance (In-Cl, ml/min) for the evaluation of renal function; and urine alpha 1-microglobuline (AMG, {mu}g/g Crea) and beta-N-acetyl-glucoseaminidase (beta-NAG, U/g Crea) as markers of tubular toxicity. Serum creatinine was measured additionally 2 days after CM had been injected. In both groups with and without AP 174{+-}65 and 104{+-}56 ml of CM (p<0.0005) were used, respectively. There were no differences with regard to renal function or risk factors for CM nephrotoxicity between both groups. In the group with AP S-Crea and In-Cl (each: mean{+-}SD) did not change significantly (before DSA: 171{+-}158 and 61{+-}24, after DSA: 189{+-}177 and 61{+-}25, respectively), beta-NAG (median) rose from 4 to 14 (p<0.05) and AMG from 8 to 55 (n.s., because of high SD). In the group without AP S-Crea increased from 134{+-}109 to 141{+-}113 (p<0.01), In-Cl dropped from 65{+-}26 to 62{+-}26 (p<0,01), beta NAG (median) rose from 4 to 8 (p=0.01), and AMG from 7 to 10 (n.s.). A rise in baseline S-Crea by more than 25% or 44 {mu}mol/l occurred in 4 and 2 patients in the group with and without AP, respectively. Creatinine increase was reversible in all cases within 7 days. In this study using sensitive methods to detect changes of renal function and tubular toxicity no additional renal function impairment in DSA with angioplasty for RAS compared with DSA alone could be demonstrated. Our data suggest

  4. 78 FR 35929 - Proposed Listing of Additional Waters To Be Included on Indiana's 2010 List of Impaired Waters...

    2013-06-14

    ... waterbodies and associated metal pollutants (e.g. aluminum, iron, copper, lead, and zinc) to be added to... the additional waterbodies and pollutants identified for inclusion on Indiana's final 2010 303(d) list... associated metal impairments set out for inclusion on Indiana's 2010 Section 303(d) list (Table 12...

  5. Additive effect of anemia and renal impairment on long-term outcome after percutaneous coronary intervention.

    Thomas Pilgrim

    Full Text Available Anemia and renal impairment are important co-morbidities among patients with coronary artery disease undergoing Percutaneous Coronary Intervention (PCI. Disease progression to eventual death can be understood as the combined effect of baseline characteristics and intermediate outcomes.Using data from a prospective cohort study, we investigated clinical pathways reflecting the transitions from PCI through intermediate ischemic or hemorrhagic events to all-cause mortality in a multi-state analysis as a function of anemia (hemoglobin concentration <120 g/l and <130 g/l, for women and men, respectively and renal impairment (creatinine clearance <60 ml/min at baseline.Among 6029 patients undergoing PCI, anemia and renal impairment were observed isolated or in combination in 990 (16.4%, 384 (6.4%, and 309 (5.1% patients, respectively. The most frequent transition was from PCI to death (6.7%, 95% CI 6.1-7.3, followed by ischemic events (4.8%, 95 CI 4.3-5.4 and bleeding (3.4%, 95% CI 3.0-3.9. Among patients with both anemia and renal impairment, the risk of death was increased 4-fold as compared to the reference group (HR 3.9, 95% CI 2.9-5.4 and roughly doubled as compared to patients with either anemia (HR 1.7, 95% CI 1.3-2.2 or renal impairment (HR 2.1, 95% CI 1.5-2.9 alone. Hazard ratios indicated an increased risk of bleeding in all three groups compared to patients with neither anemia nor renal impairment.Applying a multi-state model we found evidence for a gradient of risk for the composite of bleeding, ischemic events, or death as a function of hemoglobin value and estimated glomerular filtration rate at baseline.

  6. Mechanical ventilation and sepsis impair protein metabolism in the diaphragm of neonatal pigs

    Mechanical ventilation (MV) impairs diaphragmatic function and diminishes the ability to wean from ventilatory support in adult humans. In normal neonatal pigs, animals that are highly anabolic, endotoxin (LPS) infusion induces sepsis, reduces peripheral skeletal muscle protein synthesis rates, but ...

  7. Examining the mechanisms of overgeneral autobiographical memory: capture and rumination, and impaired executive control.

    Sumner, Jennifer A; Griffith, James W; Mineka, Susan

    2011-02-01

    Overgeneral autobiographical memory (OGM) is an important cognitive phenomenon in depression, but questions remain regarding the underlying mechanisms. The CaR-FA-X model (Williams et al., 2007) proposes three mechanisms that may contribute to OGM, but little work has examined the possible additive and/or interactive effects among them. We examined two mechanisms of CaR-FA-X: capture and rumination, and impaired executive control. We analysed data from undergraduates (N=109) scoring high or low on rumination who were presented with cues of high and low self-relevance on the Autobiographical Memory Test (AMT). Executive control was operationalised as performance on both the Stroop Colour-Word Task and the Controlled Oral Word Association Test (COWAT). Hierarchical generalised linear modelling was used to predict whether participants would generate a specific memory on a trial of the AMT. Higher COWAT scores, lower rumination, and greater cue self-relevance predicted a higher probability of a specific memory. There was also a rumination×cue self-relevance interaction: Higher (vs lower) rumination was associated with a lower probability of a specific memory primarily for low self-relevant cues. We found no evidence of interactions between these mechanisms. Findings are interpreted with respect to current autobiographical memory models. Future directions for OGM mechanism research are discussed. PMID:21294036

  8. Impaired folding and subunit assembly as disease mechanism

    Bross, P; Andresen, B S; Gregersen, N

    1998-01-01

    Rapid progress in DNA technology has entailed the possibility of readily detecting mutations in disease genes. In contrast to this, techniques to characterize the effects of mutations are still very time consuming. It has turned out that many of the mutations detected in disease genes are missense...... mutations. Characterization of the effect of these mutations is particularly important in order to establish that they are disease causing and to estimate their severity. We use the experiences with investigation of medium-chain acyl-CoA dehydrogenase deficiency as an example to illustrate that (i) impaired...... folding is a common effect of missense mutations occurring in genetic diseases, (ii) increasing the level of available chaperones may augment the level of functional mutant protein in vivo, and (iii) one mutation may have multiple effects. The interplay between the chaperones assisting folding and...

  9. Additional mechanisms conferring genetic susceptibility to Alzheimer's disease

    Miguel Calero

    2015-04-01

    Full Text Available Familial Alzheimer's disease (AD, mostly associated with early onset, is caused by mutations in three genes (APP, PSEN1 and PSEN2 involved in the production of the amyloid  peptide. In contrast, the molecular mechanisms that trigger the most common late onset sporadic AD remain largely unknown. With the implementation of an increasing number of case-control studies and the upcoming of large-scale genome-wide association studies (GWAS there is a mounting list of genetic risk factors associated to common genetic variants that have been associated to sporadic AD. Besides APOE, that presents a strong association with the disease (OR~4, the rest of these genes have moderate or low degrees of association, with OR ranging from 0.88 to 1.23. Taking together, these genes may account only for a fraction of the attributable AD risk and therefore, rare variants and epistastic gene interactions should be taken into account in order to get the full picture of the genetic risks associated to AD. Here, we review recent whole-exome studies looking for rare variants, somatic brain mutations with a strong association to the disease, and several studies dealing with epistasis as additional mechanisms conferring genetic susceptibility to AD. Altogether, recent evidence underlines the importance of defining molecular and genetic pathways and networks rather than the contribution of specific genes.

  10. Toxicity mechanisms of arsenic that are shared with neurodegenerative diseases and cognitive impairment: Role of oxidative stress and inflammatory responses.

    Escudero-Lourdes, Claudia

    2016-03-01

    Arsenic (As) is a worldwide naturally occurring metalloid. Human chronic exposure to inorganic As compounds (iAs), which are at the top of hazardous substances (ATSDR, 2013), is associated with different diseases including cancer and non- cancerous diseases. The neurotoxic effects of iAs and its methylated metabolites have been demonstrated in exposed populations and experimental models. Impaired cognitive abilities have been described in children and adults chronically exposed to iAs through drinking water. Even though different association studies failed to demonstrate that As causes neurodegenerative diseases, several toxicity mechanisms of iAs parallel those mechanisms associated with neurodegeneration, including oxidative stress and inflammation, impaired protein degradation, autophagy, and intracellular accumulation, endoplasmic reticulum stress, and mitochondrial dysfunction. Additionally, different reports have shown that specifically in brain tissue, iAs and its metabolites induce hyper-phosphorylation of the tau protein and over-regulation of the amyloid precursor protein, impaired neurotransmitters synthesis and synaptic transmission, increased glutamate receptors activation, and decreased glutamate transporters expression. Interestingly, increased and sustained pro-inflammatory responses mediated by cytokines and related factors, seems to be the triggering factor for all of such cellular pathological effects. Therefore, this review proposes that iAs-associated cognitive impairment could be the result of the activation of pro-inflammatory responses in the brain tissue, which also may favor neurodegeneration or increase the risk for neurodegenerative diseases in exposed human populations. PMID:26868456

  11. Impaired mechanical stability, migration and contractile capacity in vimentin-deficient fibroblasts

    Eckes, B.; Dogic, D.; Colucci-Guyon, E.; Wang, N.; Maniotis, A.; Ingber, D.; Merckling, A.; Langa, F.; Aumailley, M.; Delouvee, A.; Koteliansky, V.; Babinet, C.; Krieg, T.

    1998-01-01

    Loss of a vimentin network due to gene disruption created viable mice that did not differ overtly from wild-type littermates. Here, primary fibroblasts derived from vimentin-deficient (-/-) and wild-type (+/+) mouse embryos were cultured, and biological functions were studied in in vitro systems resembling stress situations. Stiffness of -/- fibroblasts was reduced by 40% in comparison to wild-type cells. Vimentin-deficient cells also displayed reduced mechanical stability, motility and directional migration towards different chemo-attractive stimuli. Reorganization of collagen fibrils and contraction of collagen lattices were severely impaired. The spatial organization of focal contact proteins, as well as actin microfilament organization was disturbed. Thus, absence of a vimentin filament network does not impair basic cellular functions needed for growth in culture, but cells are mechanically less stable, and we propose that therefore they are impaired in all functions depending upon mechanical stability.

  12. Green certificates - additional instruments at Kyoto Protocol's flexible mechanisms

    The paper presents four mechanisms, designed to realize certain objectives - to stimulate the use of electricity produced from renewable energy sources and to mitigate greenhouse gas emissions. The operation mode of these mechanisms is analyzed and their common characteristics are determined, as well as the possibility to interact each other. The systems analysed are Tradable Green Certificates and Flexible Mechanisms of Kyoto Protocol. The Green Certificates System is explained more thoroughly because the Romanian Government chose them to promote electricity from renewable energy sources on the internal electricity market. The main characteristic of these systems, which combine elements of centralization with the use of market mechanisms are outlined

  13. Molecular mechanisms regulating impaired neurogenesis of fragile X syndrome human embryonic stem cells.

    Telias, Michael; Mayshar, Yoav; Amit, Ami; Ben-Yosef, Dalit

    2015-10-15

    Fragile X syndrome (FXS) is the most common form of inherited cognitive impairment. It is caused by developmental inactivation of the FMR1 gene and the absence of its encoded protein FMRP, which plays pivotal roles in brain development and function. In FXS embryos with full FMR1 mutation, FMRP is expressed during early embryogenesis and is gradually downregulated at the third trimester of pregnancy. FX-human embryonic stem cells (FX-hESCs), derived from FX human blastocysts, demonstrate the same pattern of developmentally regulated FMR1 inactivation when subjected to in vitro neural differentiation (IVND). In this study, we used this in vitro human platform to explore the molecular mechanisms downstream to FMRP in the context of early human embryonic neurogenesis. Our results show a novel role for the SOX superfamily of transcription factors, specifically for SOX2 and SOX9, which could explain the reduced and delayed neurogenesis observed in FX cells. In addition, we assess in this study the "GSK3β theory of FXS" for the first time in a human-based model. We found no evidence for a pathological increase in GSK3β protein levels upon cellular loss of FMRP, in contrast to what was found in the brain of Fmr1 knockout mice. Our study adds novel data on potential downstream targets of FMRP and highlights the importance of the FX-hESC IVND system. PMID:26393806

  14. Impaired Functional Connectivity in the Prefrontal Cortex: A Mechanism for Chronic Stress-Induced Neuropsychiatric Disorders

    Ignacio Negrón-Oyarzo

    2016-01-01

    Full Text Available Chronic stress-related psychiatric diseases, such as major depression, posttraumatic stress disorder, and schizophrenia, are characterized by a maladaptive organization of behavioral responses that strongly affect the well-being of patients. Current evidence suggests that a functional impairment of the prefrontal cortex (PFC is implicated in the pathophysiology of these diseases. Therefore, chronic stress may impair PFC functions required for the adaptive orchestration of behavioral responses. In the present review, we integrate evidence obtained from cognitive neuroscience with neurophysiological research with animal models, to put forward a hypothesis that addresses stress-induced behavioral dysfunctions observed in stress-related neuropsychiatric disorders. We propose that chronic stress impairs mechanisms involved in neuronal functional connectivity in the PFC that are required for the formation of adaptive representations for the execution of adaptive behavioral responses. These considerations could be particularly relevant for understanding the pathophysiology of chronic stress-related neuropsychiatric disorders.

  15. Recent additions to fundament aspects of quantum mechanics

    Problems like those of Schroedinger's can comprise quantum systems as classical systems, the measurement process and reality. After a reviewing the history of interpretation of quantum mechanics it is shown how a generalized algebraic quantum theory (e.g. G.G. Emch 1986) can tackle these problems and paradoxes. This theory treats systems with infinite degrees of freedom and open systems. It is applicable both to quantum as to classical systems and thus to the measurement process with its irreversibility. The usual linear Schroedinger equation is replaced by a non-linear one where the nonlinear terms reflect the interaction of the system with its environment or with the measuring apparatus. (Quittner) To appear also in 'Naturwissenschaft und Weltbild', 1992

  16. Targeting Anabolic Impairment in Response to Resistance Exercise in Older Adults with Mobility Impairments: Potential Mechanisms and Rehabilitation Approaches

    Micah J. Drummond

    2012-01-01

    Full Text Available Muscle atrophy is associated with healthy aging (i.e., sarcopenia and may be compounded by comorbidities, injury, surgery, illness, and physical inactivity. While a bout of resistance exercise increases protein synthesis rates in healthy young skeletal muscle, the effectiveness of resistance exercise to mount a protein synthetic response is less pronounced in older adults. Improving anabolic sensitivity to resistance exercise, thereby enhancing physical function, is most critical in needy older adults with clinical conditions that render them “low responders”. In this paper, we discuss potential mechanisms contributing to anabolic impairment to resistance exercise and highlight the need to improve anabolic responsiveness in low responders. This is followed with evidence suggesting that the recovery period of resistance exercise provides an opportunity to amplify the exercise-induced anabolic response using protein/essential amino acid ingestion. This anabolic strategy, if repeated chronically, may improve lean muscle gains, decrease time to recovery of function during periods of rehabilitation, and overall, maintain/improve physical independence and reduce mortality rates in older adults.

  17. Obstructive Sleep Apnea is Linked to Depression and Cognitive Impairment: Evidence and Potential Mechanisms.

    Kerner, Nancy A; Roose, Steven P

    2016-06-01

    Obstructive sleep apnea (OSA) is highly prevalent but very frequently undiagnosed. OSA is an independent risk factor for depression and cognitive impairment/dementia. Herein the authors review studies in the literature pertinent to the effects of OSA on the cerebral microvascular and neurovascular systems and present a model to describe the key pathophysiologic mechanisms that may underlie the associations, including hypoperfusion, endothelial dysfunction, and neuroinflammation. Intermittent hypoxia plays a critical role in initiating and amplifying these pathologic processes. Hypoperfusion and impaired cerebral vasomotor reactivity lead to the development or progression of cerebral small vessel disease (C-SVD). Hypoxemia exacerbates these processes, resulting in white matter lesions, white matter integrity abnormalities, and gray matter loss. Blood-brain barrier (BBB) hyperpermeability and neuroinflammation lead to altered synaptic plasticity, neuronal damage, and worsening C-SVD. Thus, OSA may initiate or amplify the pathologic processes of C-SVD and BBB dysfunction, resulting in the development or exacerbation of depressive symptoms and cognitive deficits. Given the evidence that adequate treatment of OSA with continuous positive airway pressure improves depression and neurocognitive functions, it is important to identify OSA when assessing patients with depression or cognitive impairment. Whether treatment of OSA changes the deteriorating trajectory of elderly patients with already-diagnosed vascular depression and cognitive impairment/dementia remains to be determined in randomized controlled trials. PMID:27139243

  18. A new look at gamma? High- (>60 Hz) γ-band activity in cortical networks: function, mechanisms and impairment.

    Uhlhaas, Peter J; Pipa, Gordon; Neuenschwander, Sergio; Wibral, Michael; Singer, Wolf

    2011-03-01

    γ-band oscillations are thought to play a crucial role in information processing in cortical networks. In addition to oscillatory activity between 30 and 60 Hz, current evidence from electro- and magnetoencephalography (EEG/MEG) and local-field potentials (LFPs) has consistently shown oscillations >60 Hz (high γ-band) whose function and generating mechanisms are unclear. In the present paper, we summarize data that highlights the importance of high γ-band activity for cortical computations through establishing correlations between the modulation of oscillations in the 60-200 Hz frequency and specific cognitive functions. Moreover, we will suggest that high γ-band activity is impaired in neuropsychiatric disorders, such as schizophrenia and epilepsy. In the final part of the paper, we will review physiological mechanisms underlying the generation of high γ-band oscillations and discuss the functional implications of low vs. high γ-band activity patterns in cortical networks. PMID:21034768

  19. Mechanical ventilation alone, and in the presence of sepsis, impair protein metabolism in the diaphragm of neonatal pigs

    Mechanical ventilation (MV) impairs diaphragmatic function and diminishes the ability to wean from ventilatory support in adult humans. In normal neonatal pigs, animals that are highly anabolic, endotoxin (LPS) infusion induces sepsis, reduces peripheral skeletal muscle protein synthesis rates, but ...

  20. Testosterone and attention deficits as possible mechanisms underlying impaired emotion recognition in intimate partner violence perpetrators

    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.

  1. Cognitive aspects of frailty: mechanisms behind the link between frailty and cognitive impairment.

    Halil, M; Cemal Kizilarslanoglu, M; Emin Kuyumcu, M; Yesil, Y; Cruz Jentoft, A J

    2015-03-01

    Whereas physical impairment is the main hallmark of frailty, evidence suggests that other dimensions, such as psychological, cognitive and social factors also contribute to this multidimensional condition. Cognition is now considered a relevant domain of frailty. Cognitive and physical frailty interact: cognitive problems and dementia are more prevalent in physically frail individuals, and those with cognitive impairment are more prone to become frail. Disentangling the relationship between cognition and frailty may lead to new intervention strategies for the prevention and treatment of both conditions. Both frailty and cognitive decline share common potential mechanisms. This review examines the relationship between frailty and cognitive decline and explores the role of vascular changes, hormones, vitamin D, inflammation, insulin resistance, and nutrition in the development of physical frailty and cognitive problems, as potential underlying mechanisms behind this link. Dual tasking studies may be a useful way to explore and understand the relation between cognitive and physical frailty. Further studies are needed to elucidate this complex relation to improve the outcomes of frailty. PMID:25732212

  2. Postnatal overnutrition in mice leads to impaired pulmonary mechanics in response to salbutamol.

    Teixeira, Vanessa P; Cervilha, Daniela A B; Cabral, Layla D M; Oliveira, Luiz M; Incerpi, Erika K; Novaes, Rômulo D; Ionta, Marisa; Soncini, Roseli

    2016-05-01

    Obesity increases the risk of respiratory disease, which is associated with airway hyperresponsiveness. Although the molecular underpinnings of this phenomenon are not well established, lung remodeling is known as an important factor in this process and could potentially explain compromised lung functions. In the present study, the obesity was induced by postnatal overnutrition in Swiss mice and we investigated the pulmonary mechanics after aerosolization of saline, methacholine, and salbutamol. The lungs were prepared for morphometric analysis. Obese animals showed bronchoconstriction in response to methacholine, as evidenced by airway and tissue resistance, tissue elastance, and hysteresivity. Salbutamol was effective at recovering the response only for airway resistance but not for tissue mechanics. We suggest that this impaired response in obese mice is related to collapsed alveolar, to inflammatory cells, and to elevated deposition collagen fibers in parenchymal tissue. PMID:26497334

  3. Influence of Polymer Addition on Performance and Mechanical Properties of Lightweight Aggregate Concrete

    Jiang Cong-sheng; Wang Tao; Ding Qing-jun; Huang Shao-long; Wang Fa-zhou; Geng Jian; Hu Shu-guang

    2004-01-01

    The influence of polymer addition on microstructure, performance and mechanical properties of lightweight aggregate concrete was investigated. It was found that the addition of polymer improved the performance and mechanical properties of lightweight aggregate concrete. It was asccrtaincd thai the modification of microstructural uniformity and dcnsification with the addition of polymer is responsible for the enhancement of mechanical properties.With respect to compressive strength and bending strcngth, the lightweight aggregate concrete added with 13% ethylene-acetate ethylene interpolymer (EVA) exhibits preferred mechanical properties.

  4. Evidence-Based Communication Practices for Children with Visual Impairments and Additional Disabilities: An Examination of Single-Subject Design Studies

    Parker, Amy T.; Grimmett, Eric S.; Summers, Sharon

    2008-01-01

    This review examines practices for building effective communication strategies for children with visual impairments, including those with additional disabilities, that have been tested by single-subject design methodology. The authors found 30 studies that met the search criteria and grouped intervention strategies to align any evidence of the…

  5. Influence of boron addition on the grain refinement and mechanical properties of AZ91 Mg alloy

    This article reports the effect of boron addition on the grain refinement efficiency and mechanical properties of AZ91 magnesium alloy. The results show that the addition of boron in the form of Al-4B master alloy, significantly refines the grain size of AZ91 alloy. This refinement is due to the presence of AlB2 particles, which act as potential nucleants for Mg grains. Improved mechanical properties are obtained with the addition of boron due to the finer grains.

  6. Thermosensing mechanisms and their impairment by high-fat diet in orexin neurons.

    Belanger-Willoughby, N; Linehan, V; Hirasawa, M

    2016-06-01

    In homeotherms, the hypothalamus controls thermoregulatory and adaptive mechanisms in energy balance, sleep-wake and locomotor activity to maintain optimal body temperature. Orexin neurons may be involved in these functions as they promote thermogenesis, food intake and behavioral arousal, and are sensitive to temperature and metabolic status. How thermal and energy balance signals are integrated in these neurons is unknown. Thus, we investigated the cellular mechanisms of thermosensing in orexin neurons and their response to a change in energy status using whole-cell patch clamp on rat brain slices. We found that warming induced an increase in miniature excitatory postsynaptic current (EPSC) frequency, which was blocked by the transient receptor potential vanilloid-1 (TRPV1) receptor antagonist AMG9810 and mimicked by its agonist capsaicin, suggesting that the synaptic effect is mediated by heat-sensitive TRPV1 channels. Furthermore, warming inhibits orexin neurons by activating ATP-sensitive potassium (KATP) channels, an effect regulated by uncoupling protein 2 (UCP2), as the UCP2 inhibitor genipin abolished this response. These properties are unique to orexin neurons in the lateral hypothalamus, as neighboring melanin-concentrating hormone neurons showed no response to warming within the physiological temperature range. Interestingly, in rats fed with western diet for 1 or 11weeks, orexin neurons had impaired synaptic and KATP response to warming. In summary, this study reveals several mechanisms underlying thermosensing in orexin neurons and their attenuation by western diet. Overeating induced by western diet may in part be due to impaired orexin thermosensing, as post-prandial thermogenesis may promote satiety and lethargy by inhibiting orexin neurons. PMID:26964685

  7. Language Abilities in Children with Autism and Language Impairment: Using Narrative as a Additional Source of Clinical Information

    Manolitsi, Maria; Botting, Nicola

    2011-01-01

    Autistic Spectrum Disorder (ASD) and Specific Language Impairment (SLI) are disorders of communication that are sometimes thought to show similar structural language difficulties. Recent research has even suggested that they might be aetiologically related. However, it may be that standardized language tasks are not sensitive enough to detect…

  8. Action mechanism of antioxidation and anticorrosion and molecular design for perfluoropolyether fluid additives (I) --Action mechanism of additive and property of donating-accepting electron

    2001-01-01

    The combination energy and chemical adsorption energy of N-substituted perfluoropoly- alkyletherphenylamide (PFPEA) additive to perfluoropolyalkylether oxygen radical (RfO.) and to Fe atom have been calculated by quantum chemical methods. Structural characteristics, action mechanism, property of donating-accepting electron and substituent effect for antioxidant and anticorrosive additive are investigated. It is found that HOMO of the additives is a p-molecular orbital with lone pair electron of heteroatom. The HOMO of PFPEA additive reacts with LUMO of Fe atom to result in chemical adsorption. The LUMO of additive can interact with the SOMO of RfO. and accept electron of RfO. to form stable addition product. The additives have the property of donating-accepting electron. The electron-releasing group, particularly, the phenyl group, introduced to N atom of phenylamide can increase the combination energy and chemical adsorption energy, and enhance the antioxidant and anticorrosive efficiency. The research achievements can provide useful information for the designing of new antioxidant and anticorrosive additive. Based on the calculated results, antioxidant and anticorrosive efficiency can be predicted roughly as the following order: compounds III>II>I>IV>V.

  9. Mechanisms underlying impaired GLUT-4 translocation in glycogen-supercompensated muscles of exercised rats.

    Kawanaka, K; Nolte, L A; Han, D H; Hansen, P A; Holloszy, J O

    2000-12-01

    Exercise training induces an increase in GLUT-4 in muscle. We previously found that feeding rats a high-carbohydrate diet after exercise, with muscle glycogen supercompensation, results in a decrease in insulin responsiveness so severe that it masks the effect of a training-induced twofold increase in GLUT-4 on insulin-stimulated muscle glucose transport. One purpose of this study was to determine whether insulin signaling is impaired. Maximally insulin-stimulated phosphatidylinositol (PI) 3-kinase activity was not significantly reduced, whereas protein kinase B (PKB) phosphorylation was approximately 50% lower (P supercompensated muscles of trained rats. The contraction-stimulated increase in AMP kinase activity, which has been implicated in the activation of glucose transport by contractions, was approximately 80% lower in the muscles of the fed compared with the fasted rats 18 h after exercise. These results show that both the insulin- and contraction-stimulated pathways for muscle glucose transport activation are impaired in glycogen-supercompensated muscles and provide insight regarding possible mechanisms. PMID:11093919

  10. Insulin resistance, dyslipidemia, and apolipoprotein E interactions as mechanisms in cognitive impairment and Alzheimer's disease.

    Salameh, Therese S; Rhea, Elizabeth M; Banks, William A; Hanson, Angela J

    2016-09-01

    An increased risk for Alzheimer's disease is associated with dyslipidemia and insulin resistance. A separate literature shows the genetic risk for developing Alzheimer's disease is strongly correlated to the presence of the E4 isoform of the apolipoprotein E carrier protein. Understanding how apolipoprotein E carrier protein, lipids, amyloid β peptides, glucose, central nervous system insulin, and peripheral insulin interact with one another in Alzheimer's disease is an area of increasing interest. Here, we will review the evidence relating apolipoprotein E carrier protein, lipids, and insulin action to Alzheimer's disease and Aβ peptides and then propose mechanisms as to how these factors might interact with one another to impair cognition and promote Alzheimer's disease. PMID:27470930

  11. Bipolar Depression and Cognitive Impairment: Shared Mechanisms and New Treatment Avenues.

    Depp, Colin A; Dev, Sheena; Eyler, Lisa T

    2016-03-01

    Depression and cognitive impairment are pervasive and highly disabling aspects of bipolar disorder. Although cognitive impairment is partially independent from mood episodes, depressive symptoms may increase the risk of cognitive impairment in bipolar disorder through inflammatory processes as well as health risks such as obesity and sedentary behavior. Novel treatment avenues at the intersection of bipolar depression and cognitive impairment target inflammation directly or indirectly health behaviors such as diet, physical activity, and sleep hygiene. PMID:26876321

  12. Bone's responses to mechanical loading are impaired in type 1 diabetes.

    Parajuli, Ashutosh; Liu, Chao; Li, Wen; Gu, Xiaoyu; Lai, Xiaohan; Pei, Shaopeng; Price, Christopher; You, Lidan; Lu, X Lucas; Wang, Liyun

    2015-12-01

    Diabetes adversely impacts many organ systems including the skeleton. Clinical trials have revealed a startling elevation in fracture risk in diabetic patients. Bone fractures can be life threatening: nearly 1 in 6 hip fracture patients die within one year. Because physical exercise is proven to improve bone properties and reduce fracture risk in non-diabetic subjects, we tested its efficacy in type 1 diabetes. We hypothesized that diabetic bone's response to anabolic mechanical loading would be attenuated, partially due to impaired mechanosensing of osteocytes under hyperglycemia. Heterozygous C57BL/6-Ins2(Akita)/J (Akita) male and female diabetic mice and their age- and gender-matched wild-type (WT) C57BL/6J controls (7-month-old, N=5-7 mice/group) were subjected to unilateral axial ulnar loading with a peak strain of 3500 με at 2 Hz and 3 min/day for 5 days. The Akita female mice, which exhibited a relatively normal body weight and a mild 40% elevation of blood glucose level, responded with increased bone formation (+6.5% in Ct.B.Ar, and 4 to 36-fold increase in Ec.BFR/BS and Ps.BFR/BS), and the loading effects, in terms of changes of static and dynamic indices, did not differ between Akita and WT females (p ≥ 0.1). However, loading-induced anabolic effects were greatly diminished in Akita males, which exhibited reduced body weight, severe hyperglycemia (+230%), diminished bone formation (ΔCt.B.Ar: 0.003 vs. 0.030 mm(2), p=0.005), and suppressed periosteal bone appositions (ΔPs.BFR/BS, p=0.02). Hyperglycemia (25 mM glucose) was further found to impair the flow-induced intracellular calcium signaling in MLO-Y4 osteocytes, and significantly inhibited the flow-induced downstream responses including reduction in apoptosis and sRANKL secretion and PGE2 release. These results, along with previous findings showing adverse effects of hyperglycemia on osteoblasts and mesenchymal stem cells, suggest that failure to maintain normal glucose levels may impair bone

  13. Language abilities in children with autism and language impairment: using narrative as a additional source of clinical information

    Manolitsi, M.; Botting, N

    2011-01-01

    Autistic Spectrum Disorder (ASD) and Specific Language Impairment (SLI) are disorders of communication that are sometimes thought to show similar structural language difficulties. Recent research has even suggested that they might be aetiologically related. However, it may be that standardized language tasks are not sensitive enough to detect similarities and differences accurately. This study involved 26 Greek children with either ASD or SLI and compared them on standardized measures of stru...

  14. Influence of Molybdenum Addition on Mechanical Properties of Low Carbon HSLA-100 Steel

    Bogucki R.; Pytel S.M.

    2014-01-01

    The results of mechanical properties and microstructure observation of low carbon copper bearing steel with high addition of molybdenum are presented in this paper. This steels were characterized by contents of molybdenum in the range from 1% to 3% wt. After the thermo -mechanical processing the steels were subsequently quenched and tempered at different temperatures (500-800 °C) for 1h. The changes of mechanical properties as function of tempering temperature were typical for the steel with ...

  15. Effect of small additions of vanadium and niobium on structure and mechanical properties of ductile iron

    Fraś E.; Górny M.; Kawalec M.

    2007-01-01

    Results of investigations of influence of small additions of vanadium (up to 0,15 % V) and niobium (up to 0,04% Nb) on structure of ductile iron is presented in this work. Effect of these additions on distribution of graphite nodule diameter, nodule count, fraction and carbide count have been determined. Investigations of effect of small additions of vanadium and niobium on mechanical properties taking into account tensile strength, yield strength and elongation have also been made.

  16. Progression from impaired fasting glucose and impaired glucose tolerance to diabetes in a high-risk screening programme in general practice: the ADDITION Study, Denmark

    Rasmussen, Signe Sætre; Glümer, Charlotte; Sandbæk, Annelli;

    2007-01-01

    AIMS/HYPOTHESIS: To estimate the 1-year progression rates from both IFG and IGT to diabetes in individuals identified in a pragmatic diabetes screening programme in general practice (the ADDITION Study, Denmark [Anglo-Danish-Dutch Study of Intensive Treatment in People with Screen-Detected Diabetes......-examination after 1 year. Glucose tolerance classification was based on the 1999 WHO definition. At follow-up, diabetes was based on one diabetic glucose value of fasting blood glucose or 2-h blood glucose. RESULTS: At baseline, 308 persons had IFG and 503 had IGT. The incidence of diabetes was 17.6 and 18.8 per...

  17. Enhancement of mechanical strength in Y-Ba-Cu-O bulk superconductor through liquid binder addition

    We studied the effects of the binder addition on the green compacts. We studied the superconducting properties of bulk Y-Ba-Cu-O superconductors. The mechanical properties of the green compacts with binder addition were characterized with the compression tests. We could produce bulk Y-Ba-Cu-O superconductors with binder additions. We have studied the effects of the liquid binder (polyvinyl alcohol) addition (0-10 wt%) on the mechanical properties of the green compacts and also on the superconducting properties of bulk Y-Ba-Cu-O superconductors of 20 mm diameter produced with the top-seeded melt growth (TSMG) process. The mechanical properties of the green compacts with binder addition were characterized with the compression tests, which revealed that mechanical strength increased dramatically with increasing the amount of the binder addition. The binder-added green compacts were then subjected to the TSMG process and oxygen annealing. The trapped field measurements showed that we could produce single-grain bulk Y-Ba-Cu-O samples with binder additions up to 8 wt% without any deterioration in the superconducting properties.

  18. Striatal disorders dissociate mechanisms of enhanced and impaired response selection — Evidence from cognitive neurophysiology and computational modelling

    Christian Beste

    2014-01-01

    Full Text Available Paradoxically enhanced cognitive processes in neurological disorders provide vital clues to understanding neural function. However, what determines whether the neurological damage is impairing or enhancing is unclear. Here we use the performance of patients with two disorders of the striatum to dissociate mechanisms underlying cognitive enhancement and impairment resulting from damage to the same system. In a two-choice decision task, Huntington's disease patients were faster and less error prone than controls, yet a patient with the rare condition of benign hereditary chorea (BHC was both slower and more error prone. EEG recordings confirmed significant differences in neural processing between the groups. Analysis of a computational model revealed that the common loss of connectivity between striatal neurons in BHC and Huntington's disease impairs response selection, but the increased sensitivity of NMDA receptors in Huntington's disease potentially enhances response selection. Crucially the model shows that there is a critical threshold for increased sensitivity: below that threshold, impaired response selection results. Our data and model thus predict that specific striatal malfunctions can contribute to either impaired or enhanced selection, and provide clues to solving the paradox of how Huntington's disease can lead to both impaired and enhanced cognitive processes.

  19. Molecular and Cellular Mechanisms Elucidating Neurocognitive Basis of Functional Impairments Associated with Intellectual Disability in Down Syndrome

    Rachidi, Mohammed; Lopes, Carmela

    2010-01-01

    Down syndrome, the most common genetic cause of intellectual disability, is associated with brain disorders due to chromosome 21 gene overdosage. Molecular and cellular mechanisms involved in the neuromorphological alterations and cognitive impairments are reported herein in a global model. Recent advances in Down syndrome research have lead to…

  20. Influence of niobium addition on the high temperature mechanical properties of a centrifugally cast HP alloy

    The influence of niobium addition on the mechanical properties at high temperature of HP alloy has been investigated. Two HP alloys were centrifugally cast with a similar chemical composition differing only in the niobium content. Low strain rate high temperature tensile tests and creep-rupture tests were performed in the range of 900–1100 °C, and the results compared between the alloys. According to the results, the high temperature mechanical behavior of both alloys is controlled by several factors like solid solution, network of eutectic carbides, intradendritic precipitation and dendrite spacing. A significant increase in the mechanical properties for the HP alloy with niobium addition was found within the temperature range of 900–1050 °C. Beyond this temperature the mechanical behavior of both alloys is basically the same

  1. Influence of niobium addition on the high temperature mechanical properties of a centrifugally cast HP alloy

    Andrade, A.R., E-mail: arandrade@gmail.com [Department of Materials Engineering, Federal University of São Carlos, Rod. Washington Luiz, km 235, São Carlos, SP (Brazil); Department of Research and Development, ENGEMASA – Engineering and Materials Ltda., Rua Ernesto Cadinalli, 303, São Carlos, SP (Brazil); Bolfarini, C. [Department of Materials Engineering, Federal University of São Carlos, Rod. Washington Luiz, km 235, São Carlos, SP (Brazil); Ferreira, L.A.M.; Vilar, A.A.A. [Department of Research and Development, ENGEMASA – Engineering and Materials Ltda., Rua Ernesto Cadinalli, 303, São Carlos, SP (Brazil); Souza Filho, C.D.; Bonazzi, L.H.C. [Department of Research and Development, ENGEMASA – Engineering and Materials Ltda., Rua Ernesto Cadinalli, 303, São Carlos, SP (Brazil); Department of Materials, Aeronautical and Automotive Engineering, University of São Paulo, Av. Trabalhador Sancarlense, 400, São Carlos, SP (Brazil)

    2015-03-25

    The influence of niobium addition on the mechanical properties at high temperature of HP alloy has been investigated. Two HP alloys were centrifugally cast with a similar chemical composition differing only in the niobium content. Low strain rate high temperature tensile tests and creep-rupture tests were performed in the range of 900–1100 °C, and the results compared between the alloys. According to the results, the high temperature mechanical behavior of both alloys is controlled by several factors like solid solution, network of eutectic carbides, intradendritic precipitation and dendrite spacing. A significant increase in the mechanical properties for the HP alloy with niobium addition was found within the temperature range of 900–1050 °C. Beyond this temperature the mechanical behavior of both alloys is basically the same.

  2. Narrative competence and underlying mechanisms in children with pragmatic language impairment

    M.P. Ketelaars; K. Jansonius; J. Cuperus; L. Verhoeven

    2012-01-01

    This study investigated narrative competence in children with pragmatic language impairment (PLI) and the extent to which it is related to impairments in theory of mind and executive functioning (EF). Narrative competence was assessed using a retelling design in a group of 77 children with PLI and a

  3. Patterns of Impairments in AOS and Mechanisms of Interaction between Phonological and Phonetic Encoding

    Laganaro, Marina

    2012-01-01

    Purpose: One reason why the diagnosis of apraxia of speech (AOS) and its underlying impairment are often debated may lie in the fact that most patients do not display pure patterns of AOS. Mixed patterns are clearly acknowledged at other levels of impairment (e.g., lexical-semantic and lexical-phonological), and they have contributed to debate…

  4. Effect of Zn addition on microstructure and mechanical properties of an Al–Mg–Si alloy

    Lizhen Yan

    2014-04-01

    Full Text Available In the present work, an Al–0.66Mg–0.85Si–0.2Cu alloy with Zn addition was investigated by electron back scattering diffraction (EBSD, high resolution electron microscopy (HREM, tensile and Erichsen tests. The mechanical properties of the alloy after pre-aging met the standards of sheet forming. After paint baking, the yield strength of the alloy was improved apparently. GP(II zones and ηʹ phases were formed during aging process due to Zn addition. With the precipitation of GP zones, β″ phases, GP(II zones and ηʹ phases, the alloys displayed excellent mechanical properties.

  5. Effect of Zn addition on microstructure and mechanical properties of an Al-Mg-Si alloy

    Lizhen Yan; Yongan Zhang; Xiwu Li; Zhihui Li; Feng Wang; Hongwei Liu; Baiqing Xiong

    2014-01-01

    In the present work, an Al-0.66Mg-0.85Si-0.2Cu alloy with Zn addition was investigated by electron back scattering diffraction (EBSD), high resolution electron microscopy (HREM), tensile and Erichsen tests. The mechanical properties of the alloy after pre-aging met the standards of sheet forming. After paint baking, the yield strength of the alloy was improved apparently. GP(II) zones andηʹphases were formed during aging process due to Zn addition. With the precipitation of GP zones,β″phases, GP(II) zones andηʹphases, the alloys displayed excellent mechanical properties.

  6. Evaluation of the mechanical properties of acetic-cure silicone with the addition of magnesium silicate

    Ronald Vargas Orellana; Neide Pena Coto; Igor Studart Medeiros; Reinaldo Brito Dias

    2015-01-01

    Current study evaluates the mechanical properties (tensile and tear strength) of an acetic-cure silicone with the addition of 10 or 20% vol. magnesium silicate. Magnesium silicate was added to the silicone at concentrations of 10 (MS-10) and 20% (MS-20) volume, followed by the analysis of tensile strength, maximal elongation during tensile and tear strength. Results were compared to control group of silicone without additives (CG). Mean rates were determined and compared by analysis of v...

  7. Molecular mechanisms of diabetic coronary dysfunction due to large conductance Ca2+-activated K+ channel impairment

    WANG Ru-xing; ZHENG Jie; GUO Su-xia; LI Xiao-rong; LU Tong; SHI Hai-feng; CHAI Qiang; WU Ying; SUN Wei; JI Yuan; YAO Yong; LI Ku-lin; ZHANG Chang-ying

    2012-01-01

    Background Diabetes mellitus is associated with coronary dysfunction,contributing to a 2- to 4-fold increase in the risk of coronary heart diseases.The mechanisms by which diabetes induces vasculopathy involve endothelial-dependent and -independent vascular dysfunction in both type 1 and type 2 diabetes mellitus.The purpose of this study is to determine the role of vascular large conductance Ca2+-activated K+ (BK) channel activities in coronary dysfunction in streptozotocin-induced diabetic rats.Methods Using videomicroscopy,immunoblotting,fluorescent assay and patch clamp techniques,we investigated the coronary BK channel activities and BK channel-mediated coronary vasoreactivity in streptozotocin-induced diabetic rats.Results BK currents (defined as the iberiotoxin-sensitive K+ component) contribute (65±4)% of the total K+ currents in freshly isolated coronary smooth muscle cells and >50% of the contraction of the inner diameter of coronary arteries from normal rats.However,BK current density is remarkably reduced in coronary smooth muscle cells of streptozotocin-induced diabetic rats,leading to an increase in coronary artery tension.BK channel activity in response to free Ca2+ is impaired in diabetic rats.Moreover,cytoplasmic application of DHS-1 (a specific BK channel β1 subunit activator) robustly enhanced the open probability of BK channels in coronary smooth muscle cells of normal rats.In diabetic rats,the DHS-1 effect was diminished in the presence of 200 nmol/L Ca2+ and was significantly attenuated in the presence of high free calcium concentration,i.e.,1 μmol/L Ca2+.Immunoblotting experiments confirmed that there was a 2-fold decrease in BK-β1 protein expression in diabetic vessels,without altering the BK channel α-subunit expression.Although the cytosolic Ca2+ concentration of coronary arterial smooth muscle cells was increased from (103±23)nmol/L (n=5) of control rats to (193±22) nmol/L (n=6,P<0.05) of STZ-induced diabetic rats,reduced BK

  8. Mechanical behavior of polymer-matrix biocomposites modified by nano/micro additives

    Suchý, Tomáš; Balík, Karel; Sucharda, Zbyněk; Černý, Martin; Sochor, M.

    -, 77-78 (2008), s. 8-10. ISSN 1429-7248. [Conference Biomaterials in Medicine and Veterinary Medicine /18./. Rytro, 13.11.2008-16.11.2008] R&D Projects: GA ČR(CZ) GA106/06/1576 Institutional research plan: CEZ:AV0Z30460519 Keywords : additives * calcium phosphates * mechanical properties Subject RIV: JI - Composite Materials

  9. Fluid mechanics of additive manufacturing of metal objects by accretion of droplets – a survey

    Tesař, Václav

    Liberec: Polypress s.r.o, 2015 - (Dančová, P.; Veselý, M.), s. 800-808 [Experimental Fluid Mechanics 2015. Praha (CZ), 17.11.2015-20.11.2015] R&D Projects: GA ČR GA13-23046S Institutional support: RVO:61388998 Keywords : additive manufacturing * molten metal droplets * power beams Subject RIV: BK - Fluid Dynamics

  10. Mechanisms of Mn(OAc)3-based oxidative free-radical additions and cyclizations

    Snider, Barry B.

    2009-01-01

    The mechanistic details of Mn(OAc)3-based oxidative free-radical additions and cyclizations are reviewed. The mechanisms of electron transfer to generate radicals, electron transfer to convert the radicals to oxidized products, and further oxidation of the products are covered.

  11. Improving Student Understanding of Addition of Angular Momentum in Quantum Mechanics

    Zhu, Guangtian; Singh, Chandralekha

    2013-01-01

    We describe the difficulties advanced undergraduate and graduate students have with concepts related to addition of angular momentum in quantum mechanics. We also describe the development and implementation of a research-based learning tool, Quantum Interactive Learning Tutorial (QuILT), to reduce these difficulties. The preliminary evaluation…

  12. Impaired Driving

    ... help prevent injuries and deaths from alcohol-impaired driving. The Problem Risk Factors BAC Effects Prevention Additional Resources How big is the problem? In 2014, 9,967 people were killed in alcohol-impaired driving crashes, accounting for nearly one-third (31%) of ...

  13. Effect of carbon nanofibre addition on the mechanical properties of different f carbon-epoxy composites

    I Srikanth; Suresh Kumar; Vajinder Singh; B Rangababu; Partha Ghosal; Ch Subrahmanyam

    2015-04-01

    Carbon-epoxy (C-epoxy) laminated composites having different fibre volume fractions (40, 50, 60 and 70) were fabricated with and without the addition of aminofunctionalized carbon nanofibres (A-CNF). Flexural strength, interlaminar shear strength (ILSS) and tensile strength of the composite laminates were determined. It was observed that, the ability of A-CNF to enhance the mechanical properties of C-epoxy diminished significantly as the fibre volume fraction (f) of the C-epoxy increased from 40 to 60. At 70f, the mechanical properties of the A-CNF reinforced C-epoxy were found to be lower compared to the C-epoxy composite made without the addition of A-CNF. In this paper suitable mechanisms for the observed trends are proposed on the basis of the fracture modes of the composite.

  14. Influence of Molybdenum Addition on Mechanical Properties of Low Carbon HSLA-100 Steel

    Bogucki R.

    2014-10-01

    Full Text Available The results of mechanical properties and microstructure observation of low carbon copper bearing steel with high addition of molybdenum are presented in this paper. This steels were characterized by contents of molybdenum in the range from 1% to 3% wt. After the thermo -mechanical processing the steels were subsequently quenched and tempered at different temperatures (500-800 °C for 1h. The changes of mechanical properties as function of tempering temperature were typical for the steel with the copper addition. The sudden drop of impact resistance after tempering from 575 °C to 600 °C was caused probably by precipitates of Laves phase of type Fe2Mo.

  15. Effects of recrystallization and Nb additions on texture and mechanical anisotropy of Zircaloy

    Murty, K.L. (North Carolina State University, Raleigh, NC 27695-7909 (United States)); Jallepalli, Ravi (North Carolina State University, Raleigh, NC 27695-7909 (United States)); Mahmood, S.T. (North Carolina State University, Raleigh, NC 27695-7909 (United States))

    1994-06-01

    The effect of recrystallization on the crystallographic textures and anisotropic mechanical properties of Zircaloy-4 sheets was investigated. In addition, the influence of niobium additions on these properties was studied using three different alloys. The mechanical anisotropy parameters were determined by mechanical testing of gridded tensile samples. The textures were characterized by X-ray pole figure measurements and crystallite orientation distribution functions (CODFs). The CODFs were combined with a crystal plasticity model to predict the anisotropy parameters based on the dominance individually of basal, prism and pyramidal slip systems. Good agreement was noted between the experimental results and model predictions based on prism slip for the recrystallized materials, while the results on cold-worked sheets differed from model predictions for all the three slip systems. ((orig.))

  16. Effects of recrystallization and Nb additions on texture and mechanical anisotropy of Zircaloy

    The effect of recrystallization on the crystallographic textures and anisotropic mechanical properties of Zircaloy-4 sheets was investigated. In addition, the influence of niobium additions on these properties was studied using three different alloys. The mechanical anisotropy parameters were determined by mechanical testing of gridded tensile samples. The textures were characterized by X-ray pole figure measurements and crystallite orientation distribution functions (CODFs). The CODFs were combined with a crystal plasticity model to predict the anisotropy parameters based on the dominance individually of basal, prism and pyramidal slip systems. Good agreement was noted between the experimental results and model predictions based on prism slip for the recrystallized materials, while the results on cold-worked sheets differed from model predictions for all the three slip systems. ((orig.))

  17. PAH growth initiated by propargyl addition: Mechanism development and computational kinetics

    Raj, Abhijeet Dhayal

    2014-04-24

    Polycyclic aromatic hydrocarbon (PAH) growth is known to be the principal pathway to soot formation during fuel combustion, as such, a physical understanding of the PAH growth mechanism is needed to effectively assess, predict, and control soot formation in flames. Although the hydrogen abstraction C2H2 addition (HACA) mechanism is believed to be the main contributor to PAH growth, it has been shown to under-predict some of the experimental data on PAHs and soot concentrations in flames. This article presents a submechanism of PAH growth that is initiated by propargyl (C 3H3) addition onto naphthalene (A2) and the naphthyl radical. C3H3 has been chosen since it is known to be a precursor of benzene in combustion and has appreciable concentrations in flames. This mechanism has been developed up to the formation of pyrene (A4), and the temperature-dependent kinetics of each elementary reaction has been determined using density functional theory (DFT) computations at the B3LYP/6-311++G(d,p) level of theory and transition state theory (TST). H-abstraction, H-addition, H-migration, β-scission, and intramolecular addition reactions have been taken into account. The energy barriers of the two main pathways (H-abstraction and H-addition) were found to be relatively small if not negative, whereas the energy barriers of the other pathways were in the range of (6-89 kcal·mol-1). The rates reported in this study may be extrapolated to larger PAH molecules that have a zigzag site similar to that in naphthalene, and the mechanism presented herein may be used as a complement to the HACA mechanism to improve prediction of PAH and soot formation. © 2014 American Chemical Society.

  18. Impaired Functional Connectivity in the Prefrontal Cortex: A Mechanism for Chronic Stress-Induced Neuropsychiatric Disorders

    Ignacio Negrón-Oyarzo; Francisco Aboitiz; Pablo Fuentealba

    2016-01-01

    Chronic stress-related psychiatric diseases, such as major depression, posttraumatic stress disorder, and schizophrenia, are characterized by a maladaptive organization of behavioral responses that strongly affect the well-being of patients. Current evidence suggests that a functional impairment of the prefrontal cortex (PFC) is implicated in the pathophysiology of these diseases. Therefore, chronic stress may impair PFC functions required for the adaptive orchestration of behavioral response...

  19. EFFECT OF MONTMORILLONITE ADDITION ON MECHANICAL CHARACTERIZATIONS OF POLYIMIDE NANOCOMPOSITE FILMS

    Wang Xishu; Zhang Yihe; Fu Shaoyun; Feng Xiqiao

    2005-01-01

    Tensile deformation and fracture characteristics of polyimide/montmorillonite nanocomposite films are investigated to enhance the particular mechanical properties and understand the effective factors in dominating the mechanical properties of nanocomposites, such as the nanolayer, matrix and nanolayer/matrix interface. How to contribute to the mechanical properties of nanocomposite film is a very complex problem. In this paper, these factors are analyzed based on the addition amount and fracture mechanics. The results indicate that the specimen at 20 wt% MMT breaks prematurely with a fracture strength (σb=78 MPa) much lower than that (σb = 128 MPa) at the 1wt% MMT. However, the Young's modulus (3.2 GPa) of the former is higher than that (1.9 GPa) of the latter. Fractography also indicates that the brittle cracking formed in high content addition is the main cause of failure but microscopically ductile fracture morphology still exists locally. And for the trace element addition, the smaller threading slipping veins are evenly distributed on the entire fracture section of these films. Therefore, these characteristics would presumably be associated with both the concentration effects of size of nanocomposite sheets and the increasing deformation harmony in nanolayers.

  20. Influence of cementitious additions on rheological and mechanical properties of reactive powder concretes

    Zenati, A.; Arroudj, K.; Lanez, M.; Oudjit, M. N.

    2009-11-01

    Following needs of concrete market and the economic and ecological needs, several researchers, all over the world, studied the beneficial effect which the incorporation of the mineral additions in Portland cement industry can bring. It was shown that the incorporation of local mineral additions can decrease the consumption of crushing energy of cements, and reduce the CO2 emission. Siliceous additions, moreover their physical role of filling, play a chemical role pozzolanic. They contribute to improving concrete performances and thus their durability. The abundance of dunes sand and blast furnace slag in Algeria led us to study their effect like cementitious additions. The objective of this paper is to study the effect of the incorporation of dunes sand and slag, finely ground on rheological and mechanical properties of reactive powder concretes containing ternary binders.

  1. Mechanism for the addition of carbenoid CH2ClLi to formaldehyde

    2000-01-01

    Ab initio HF/6-31G* calculations have been performed for the addition mechanism of carbenoid CH2ClLi with formaldehyde in tetrahydrofuran. An early complex of formaldehyde with CH2ClLi is first formed with quite exothermic effect. Only a little activation energy of 14.6 kJ/mol is needed for the complex developing into the product through a transition state with coplanar bicyclic structure. In this process, the eletrophilic attack of carbonyl carbon of formaldehyde is more active than the nucleophilic attack of carbon of carbenoid. The exothermal effect of this addition process is up to 216.5 kJ/mol.

  2. Mechanism for the addition of carbenoid CH2ClLi to formaldehyde

    李吉海[1; 孙昌俊[2; 刘少杰[3; 冯圣玉[4; 冯大诚[5

    2000-01-01

    Ab initlo HF/6-31G* calculations have been performed for the addition mechanism of carbenoid CH2CILi with formaldehyde in tetrahydrofuran. An early complex of formaldehyde with CH2CILi is first formed with quite exothermic effect. Only a little activation energy of 14.6 kJ/mol is needed for the complex developing into the product through a transition state with coplanar bicyclic structure. In this process, the eletrophilic attack of carbonyl carbon of formaldehyde is more active than the nucleophilic attack of carbon of carbenoid. The exothermal effect of this addition process is up to 216.5 kJ/mol.

  3. The role of additives in the recombination luminescence mechanism of irradiated 2-methyltetrahydrofuran glasses

    The radiothermoluminescence (RTL) of γ-irradiated pure glassy 2-methyltetrahydrofuran (2-MTHF) and of 2-MTHF glasses containing additives was measured. For pure 2-MTHF a very weak luminescence peak at 93 K (heating rate 0,05 K/s) was found which in the presence of certain additives was enhanced by several orders of magnitude. Using data of radiothermoluminescence, absorption and phosphorescence measurements and bleaching experiments an attempt was made to derive a reaction mechanism. It was found to exist different possibilities for activation the ionic species to give recombination luminescence. (author)

  4. Mechanical Effects of Hafnium and Boron Addition to Aluminum Alloy Films for Submicrometer LSI Interconnects

    Onoda, Hiroshi; Takahashi, Eishi; Kawai, Yasuaki; Madokoro, Shoji; Fukuyo, Hideaki; Sawada, Susumu

    1993-11-01

    This is the first report on the mechanical properties of hafnium- and boron-added Al-Si-Cu alloy film for LSI interconnects. Two to three hundred ppm of hafnium and boron addition into Al-Si-Cu alloy film does not influence the Al alloy properties for metal lines as LSI interconnects, such as its low resistivity, low ohmic contact resistance with Si, and fine-line patterning feasibility. The mechanical properties of the Al alloy film, however, change greatly. Vertical hillock and lateral hillock formation is considerably suppressed during heat treatments used in LSI fabrication processes. Stress-induced void formation is also reduced during aging test at 125°C. These effects due to hafnium and boron addition are considered to be an impurity precipitation effect ihat was confirmed by X-ray diffraction analysis and electron probe microanalysis.

  5. Cytomixis impairs meiosis and influences reproductive success in Chlorophytum comosum (Thunb) Jacq. – an additional strategy and possible implications

    S K Lattoo; S Khan; S Bamotra; A K Dhar

    2006-12-01

    Spontaneous intercellular chromatin migration/cytomixis was observed to occur in the pollen mother cells (PMCs) of the Chlorophytum comosum for the first time. The migration through cytomictic channels was more pronounced in meiosis-I and very rare in meiosis-II. The process was associated with erratic meiosis, which was characterized by defects in chromosome organization and segregation. Cytomixis was more intense in the month of April than in July and consequently the frequency of meiotic irregularities was much more pronounced during the month of April. As a consequence of abnormal meiosis, fertility was drastically reduced resulting in meager seed efficiency of 17% only. Recombination system also does not guarantee the release of sufficient variability. We view the phenomenon of cytomixis as genetically controlled mechanism involving meiotic genes and operating through signal transduction pathway triggered by the environmental stimuli. The evolutionary significance and tenable hypothesis in the backdrop of existing literature is also proposed.

  6. Microstructure and mechanical properties of the Al-Ti alloy with calcium addition

    L.A. Dobrzański; K. Labisz; Olsen, A

    2008-01-01

    Purpose: In this paper there are presented the investigation results of mechanical properties and microstructure with intermetallic phases of the aluminium – titanium alloy with a defined content of Ca addition. The purpose of this work was also to determine the heat treatment conditions for solution heat treatment of the investigation alloys.Design/methodology/approach: The reason of this work was to determine the heat treatment influence, particularly solution heat treatment time to the cha...

  7. EFFECTS OF PHENOL RESIN ADDITIVE ON DYNAMIC MECHANICAL PROPERTIES OF ACRYLATE RUBBER AND ITS BLENDS

    Chi-fei Wu

    2003-01-01

    The dynamic mechanical properties of a new blend system consisting of phenol resin and polar polymer (acrylate rubber and/or chlorinated polypropylene) were investigated. It was found that the addition of phenol resin to acrylate rubber and its incompatible blend can cause a remarkable improvement in the temperature dependence of the loss tangent. As a result, the present blends are very good damping materials.

  8. Additive manufacture of an aluminium alloy: processing, microstructure, and mechanical properties

    Aboulkhair, Nesma T.

    2016-01-01

    Additive manufacturing of aluminium alloys using selective laser melting (SLM) is of research interest nowadays because of its potential benefits in industry sectors such as aerospace and automotive. However, in order to demonstrate the credibility of aluminium SLM for industrial needs, a comprehensive understanding of the interrelation between the process parameters, produced microstructure, and mechanical behaviour is still needed. This thesis aims at contributing to developing this compreh...

  9. Fluid mechanics of additive manufacturing of metal objects by accretion of droplets – a survey

    Tesař Václav

    2016-01-01

    Paper presents a survey of principles of additive manufacturing of metal objects by accretion of molten metal droplets, focusing on fluid-mechanical problems that deserve being investigated. The main problem is slowness of manufacturing due to necessarily small size of added droplets. Increase of droplet repetition rate calls for basic research of the phenomena that take place inside and around the droplets: ballistics of their flight, internal flowfield with heat and mass transfer, oscillati...

  10. Effect of reinforcement nanoparticles addition on mechanical properties of SBS/curaua fiber composites

    Borba, Patricia M. [Servico Nacional de Aprendizagem Industrial (CETEPO/SENAI/RS), Sao Leopoldo, RS (Brazil). Centro Tecnologico de Polimeros; Tedesco, Adriana [Braskem S. A., III Polo Petroquimico, Triunfo, RS (Brazil); Lenz, Denise M., E-mail: denise.lenz@gmail.com [Universidade Luterana do Brasil (ULBRA), Canoas, RS (Brazil). Programa de Pos-graduacao em Engenharia de Materiais e Processos Sustentaveis

    2014-03-15

    Composites of styrene-butadiene-styrene triblock copolymer (SBS) matrix with curauá fiber and/or a nanoparticulated mineral (montmorillonite clay - MMT) used as reinforcing agents were prepared by melt-mixing. The influence of clay addition on properties like tensile and tear strength, rebound resilience, flex fatigue life, abrasion loss, hardness and water absorption of composites with 5, 10 and 20 wt% of curauá fiber was evaluated in presence of maleic anhydride grafted styrene-(ethylene-co-butylene)-styrene triblock copolymer (MA-g-SEBS) coupling agent. Furthermore, the effect of mineral plasticizer loading on tensile strength of selected composites was investigated. The hybrid SBS composite that showed the best overall mechanical performance was composed by 2 wt% of MMT and 5 wt% of curauá fiber. Increasing fiber content up to 20 wt% resulted in a general decrease in all mechanical properties as well as incorporation of 5 wt% MMT caused a decrease in the tensile strength in all fiber contents. The hybrid composites showed clay agglomerates (tactoids) poorly dispersed that could explain the poor mechanical performance of composites at higher concentrations of curauá fiber and MMT nanoparticles. The addition of plasticizer further decreased the tensile strength while the addition of MMT nanoparticles decreased water absorption for all SBS composites. (author)

  11. Effect of reinforcement nanoparticles addition on mechanical properties of SBS/curaua fiber composites

    Composites of styrene-butadiene-styrene triblock copolymer (SBS) matrix with curauá fiber and/or a nanoparticulated mineral (montmorillonite clay - MMT) used as reinforcing agents were prepared by melt-mixing. The influence of clay addition on properties like tensile and tear strength, rebound resilience, flex fatigue life, abrasion loss, hardness and water absorption of composites with 5, 10 and 20 wt% of curauá fiber was evaluated in presence of maleic anhydride grafted styrene-(ethylene-co-butylene)-styrene triblock copolymer (MA-g-SEBS) coupling agent. Furthermore, the effect of mineral plasticizer loading on tensile strength of selected composites was investigated. The hybrid SBS composite that showed the best overall mechanical performance was composed by 2 wt% of MMT and 5 wt% of curauá fiber. Increasing fiber content up to 20 wt% resulted in a general decrease in all mechanical properties as well as incorporation of 5 wt% MMT caused a decrease in the tensile strength in all fiber contents. The hybrid composites showed clay agglomerates (tactoids) poorly dispersed that could explain the poor mechanical performance of composites at higher concentrations of curauá fiber and MMT nanoparticles. The addition of plasticizer further decreased the tensile strength while the addition of MMT nanoparticles decreased water absorption for all SBS composites. (author)

  12. Increased Mechanical Properties Through the Addition of Zr to GRCop-84

    Ellis, David L.; Lerch, Bradley A.

    2011-01-01

    GRCop-84 (Cu-8 at.% Cr-4 at.% Nb) has shown exceptional mechanical properties above 932 F (773 K). However, its properties below 932 F (773 K) are inferior to precipitation strengthened alloys such as Cu-Cr, Cu-Zr and Cu-Cr-Zr when they are in the fully aged, hard-drawn condition. It has been noted that the addition of small amounts of Zr, typically 0.1 wt.% to 0.5 wt.%, can greatly enhance the mechanical properties of copper-based alloys. Limited testing was conducted upon GRCop-84 with an addition of 0.4 wt.% Zr to determine its tensile, creep and low cycle fatigue (LCF) properties. Very large increases in strength (up to 68%) and ductility (up to 123%) were observed at both room temperature and 932 F (773 K). Creep properties at 932 F (773 K) demonstrated more than an order of magnitude decrease in the creep rate relative to unmodified GRCop-84 with a corresponding order of magnitude increase in creep life. Limited LCF testing showed that the modified alloy had a comparable LCF life at room temperature, but it was capable of sustaining a much higher load. While more testing and composition optimization are required, the addition of Zr to GRCop-84 has shown clear benefits to mechanical properties.

  13. Structural, mechanical and tribological characterization of Zn25Al alloys with Si and Sr addition

    Highlights: • Influence of the strontium (Sr) addition on the Zn25Al–Si alloys were investigated. • The microstructure was improved upon the addition of strontium. • The hardness and compressive yield stress did not change significantly. • The wear resistance was improved, and coefficient of friction was slightly increased. • The increase in wt.% Sr showed an effect of a double-nature on the wear resistance. - Abstract: The ZA-27 alloy is a zinc–aluminium casting alloy that has been frequently used as the material for sleeves of plain bearings. It has good physical, mechanical and tribological properties. However, one of the major disadvantages is its dimensional instability over a period of time (ageing). To overcome this, copper in the alloy may be replaced with silicon. Coarsening of silicon particles can be controlled by a suitable addition of strontium. In this paper, the commercial ZA-27 alloy and six different Zn25Al alloys (with 1 and 3 wt.% silicon; and with 0, 0.03 and 0.05 wt.% strontium) were obtained by casting in the preheated steel mould. Casting of the alloys was carried out at a laboratory level. In the alloys containing silicon, a finer dendritic structure was noticed compared to the structure of the commercial ZA-27 alloy. The addition of strontium influenced the size and distribution of primary silicon particles. Needle-like particles of eutectic silicon were changed into the fibrous ones. The presence of silicon and strontium did not significantly affect mechanical properties of the obtained Zn25Al alloys compared to mechanical properties of the commercial ZA-27 alloy. Wear rate of the alloys containing silicon was lower than that of the ZA-27 alloy. The addition of strontium further lowers the wear rate and slightly increases the coefficient of friction

  14. Stabilisation of mechanical properties in silver alloys by addition of lanthanides

    W. Głuchowski

    2008-10-01

    Full Text Available Purpose: Silver alloys intended for industrial application should characterise by high electrical conductivity (as pure silver as well as high mechanical and functional properties, stable also at elevated temperature. The objective of this work was to investigate the mechanical properties stability of Ag-La (0.5% and Ag-mishmetal (1 and 4% alloys caused by severe plastic deformation compared to the Ag+(7.5 wt %Cu alloy and pure Ag materials.Design/methodology/approach: Tests were made with the samples obtained by casting and further plastic working included KOBO® extrusion process and drawing. Wires were annealed in temperature range 50 - 500°C. The mechanical properties (at room temperature, elevated temperature and after annealing and microstructure were examined. The values of yield strength obtained in a tension tests have been compared to the values calculated theoretically.Findings: Additive of rare earth metals contributed to fine structure obtaining, particles formed in grain boundaries stabilized microstructure at elevated temperature. Increase of mechanical properties of investigated alloys was connected with presence of fine precipitations in silver matrix, which confirmed susceptibility to precipitation hardening of silver – mishmetal alloys.Research limitations/implications: Ability of new alloys to precipitation hardening should be confirmed by further investigations, including solution heat treatment and ageing, also for materials prepared in vacuum furnace.Practical implications: Stability of mechanical properties at elevated temperature, gives possibility to use of new silver allays for producing elements designed to operate at elevated temperatures or exposed to rapid temperature changes. Increased mechanical properties and good tarnish resistance indicates possibility of new applications of investigated alloys in jewellery and medicine, after additional and essential investigations.Originality/value: The wire made from

  15. Mechanism of strengthening of cube texture for high purity aluminum foils by additional-annealing

    张新明; 刘胜胆; 唐建国; 周卓平

    2003-01-01

    The mechanism of strengthening of cube texture ({001}〈100〉) by additional-annealing of high purity aluminum foils was investigated by using orientation distribution functions (ODFs) and electron back scattered diffraction (EBSD). The results of ODFs and fiber show that the orientation densities of the S {123}〈634〉 and Cu {112}〈111〉 components increase in both the additional-annealed samples and the 0.11 mm final cold-rolled foils. And the EBSD results demonstrate that cube nuclei can be identified in the deformed matrix of those additional-annealed samples. It is suggested that the strengthening of cube texture can be brought out by the increasing of components of S and Cu and the formation of cube nuclei caused by additional-annealing. Moreover, it is found that the cube texture increases first and then decreases with increasing additional-annealing temperature, and it is the strongest at 180 ℃.The strengthening of cube texture by additional-annealing is proposed as the result of oriented growth of cube subgrains.

  16. Influence of niobium additions on mechanical properties and corrosion of INCOLOY 800 H

    The studies were carried out with six model alloys of the type INCOLOY alloy 800 H (32 Ni/20 Cr), obtained by variation of the niobium additions with up to 1.55 wt. p.c. of Nb. The mechanical properties and structural characteristics of these samples are listed after treatments as follows: - Aging at 650, 800, and 9000C (Notch bending tests and tensile tests at room temperature). - Carbonisation at 800 and 9000C in PNP standard helium (C-analysis, long-term creep tests at 9000C). Alloys with Nb additions showed constant good strength and ductility after aging, values being better than those for material without Nb additions. The creep tests showed that tensile strengths is improved with increasing niobium content; carbonisation is less than in alloys without Nb. (orig./IHOE)

  17. Mechanisms and modeling of the effects of additives on the nitrogen oxides emission

    Kundu, Krishna P.; Nguyen, Hung Lee; Kang, M. Paul

    1991-01-01

    A theoretical study on the emission of the oxides of nitrogen in the combustion of hydrocarbons is presented. The current understanding of the mechanisms and the rate parameters for gas phase reactions were used to calculate the NO(x) emission. The possible effects of different chemical species on thermal NO(x), on a long time scale were discussed. The mixing of these additives at various stages of combustion were considered and NO(x) concentrations were calculated; effects of temperatures were also considered. The chemicals such as hydrocarbons, H2, CH3OH, NH3, and other nitrogen species were chosen as additives in this discussion. Results of these calculations can be used to evaluate the effects of these additives on the NO(x) emission in the industrial combustion system.

  18. Synthesis of Porous and Mechanically Compliant Carbon Aerogels Using Conductive and Structural Additives

    Carlos Macias

    2016-01-01

    Full Text Available We report the synthesis of conductive and mechanically compliant monolithic carbon aerogels prepared by sol-gel polycondensation of melamine-resorcinol-formaldehyde (MRF mixtures by incorporating diatomite and carbon black additives. The resulting aerogels composites displayed a well-developed porous structure, confirming that the polymerization of the precursors is not impeded in the presence of either additive. The aerogels retained the porous structure after etching off the siliceous additive, indicating adequate cross-linking of the MRF reactants. However, the presence of diatomite caused a significant fall in the pore volumes, accompanied by coarsening of the average pore size (predominance of large mesopores and macropores. The diatomite also prevented structural shrinkage and deformation of the as-prepared monoliths upon densification by carbonization, even after removal of the siliceous framework. The rigid pristine aerogels became more flexible upon incorporation of the diatomite, favoring implementation of binderless monolithic aerogel electrodes.

  19. Additional degrees of freedom associated with position measurements in non-commutative quantum mechanics

    Rohwer, CM

    2012-01-01

    In this thesis we shall demonstrate that a measurement of position alone in non-commutative space cannot yield complete information about the quantum state of a particle. Indeed, the formalism used entails a description that is non-local in that it requires all orders of positional derivatives through the star product that is used ubiquitously to map operator multiplication onto function multiplication in non-commutative systems. It will be shown that there exist several equivalent local descriptions, which are arrived at via the introduction of additional degrees of freedom. Consequently non-commutative quantum mechanical position measurements necessarily confront us with some additional structure which is necessary to specify quantum states completely. The remainder of the thesis, will involve investigations into the physical interpretation of these additional degrees of freedom. For one particular local formulation, the corresponding classical theory will be used to demonstrate that the concept of extended...

  20. Mechanical properties of open-cell metallic biomaterials manufactured using additive manufacturing

    Highlights: ► Finite element (FE) models were used to predict the mechanical properties of porous biomaterials. ► Porous materials were produced using additive manufacturing techniques. ► Manufacturing irregularities need to be implemented in FE models. ► FE models are more accurate than analytical models in predicting mechanical properties. - Abstract: An important practical problem in application of open-cell porous biomaterials is the prediction of the mechanical properties of the material given its micro-architecture and the properties of its matrix material. Although analytical methods can be used for this purpose, these models are often based on several simplifying assumptions with respect to the complex architecture and cannot provide accurate prediction results. The aim of the current study is to present finite element (FE) models that can predict the mechanical properties of porous titanium produced using selective laser melting or selective electron beam melting. The irregularities caused by the manufacturing process including structural variations of the architecture are implemented in the FE models using statistical models. The predictions of FE models are compared with those of analytical models and are tested against experimental data. It is shown that, as opposed to analytical models, the predictions of FE models are in agreement with experimental observations. It is concluded that manufacturing irregularities significantly affect the mechanical properties of porous biomaterials

  1. Physical and mechanical characterization of Portland cement mortars made with expanded polystyrene particles addition (EPS

    Ferrándiz-Mas, V.

    2012-12-01

    Full Text Available On this work the influence of the addition of different types (commercial and recycled and contents of expanded polystyrene on the physical and mechanical properties of Portland cement mortars has been studied. Variables studied are: workability, air content, bulk density, mechanical strength, porosity, water absorption and sound absorption. Mixtures have been also characterized by scanning electron microscopy. Air-entraining agents, water retainer and superplasticizer additives have been used in order to improve the workability of mortars. The results show that the workability and mechanical strength decreases with increasing content of expanded polystyrene. Additives improve the workability and porosity, allowing manufacture mortars with high levels of recycled material that show mechanical properties suitable for use as masonry mortars, stucco and plaster.

    El objetivo de este estudio es evaluar la influencia de la adición de distintos tipos y dosificaciones de poliestireno expandido, tanto comerciales como procedentes de reciclado, sobre las características físicas y mecánicas de morteros de cemento portland. Las variables estudiadas fueron: consistencia, aire ocluido, densidad aparente, resistencias mecánicas, porosidad, absorción de agua y absorción acústica. Los morteros también se han caracterizado por microscopia electrónica de barrido. Con objeto de mejorar la trabajabilidad de los morteros se ha empleado aditivos aireante, retenedor de agua y fluidificante. Los resultados muestran que al aumentar la cantidad de poliestireno expandido la trabajabilidad y las resistencias mecánicas disminuyen. El empleo de aditivos mejora la trabajabilidad y la porosidad, permitiendo fabricar morteros con altos contenidos de residuo, con propiedades mecánicas adecuadas para su empleo como morteros de albañilería, revoco y enlucido.

  2. Influence of silicon addition on the mechanical properties and corrosion resistance of low-alloy steel

    M Hebda; H Dębecka; J Kazior

    2015-12-01

    The addition of silicon to low-alloy steel allows to modify the materials' microstructure and thus to improve their corrosion resistance and mechanical properties. The influence of adding different amounts of silicon on the properties (density, transverse rupture strength, microhardness and corrosion resistance) and microstructure of low-alloy steel was investigated. Samples were prepared via the mechanical alloying process, which is the most useful method to homogeneously introduce silicon to low-alloy steel. Sintering was performed by using the spark plasma sintering (SPS) technique. After the SPS process, half of each of the obtained samples was heat-treated in a vacuum furnace. The results show that high-density materials were achieved, and a homogeneous and fine microstructure was obtained. The investigated compositions containing 1 wt% of silicon had better corrosion resistance than samples with 3 wt% of silicon addition. Furthermore, corrosion resistance as well as the mechanical and plastic properties of the samples with 1 wt% of silicon can be further improved by applying heat treatment.

  3. Effect of carbon nanofiber addition in the mechanical properties and durability of cementitious materials

    Galao, O.

    2012-09-01

    Full Text Available This paper reports on recent work that is directed at studying the changes in the mechanical properties of Portland cement based mortars due to the addition of carbon nanofiber (CNF. Both flexural and compression strength has been determined and related to the CNF addition to the mix, to the curing time and to the porosity and density of the matrix. Also, corrosion of embedded steel rebars in CNF cement pastes exposed to carbonation and chloride attacks has been investigated. The increase in CNF addition implies higher corrosion intensity and higher levels of mechanical properties.En este artículo se han estudiado los cambios en las propiedades mecánicas de los morteros de cemento Portland debido a la adición de nanofibras de carbono (NFC. Se han determinado las resistencias a flexotracción y a compresión de los morteros en relación a la cantidad de NFC añadidas a la mezcla, al tiempo de curado y a la porosidad y densidad de los mismos. Además se han investigado los niveles de corrosión de barras de acero embebidas en pastas de cemento con NFC expuestos al ataque por carbonatación y por ingreso de cloruros. El aumento en el porcentaje de NFC añadido se traduce en un aumento la intensidad de corrosión registrada y una mejora de las propiedades mecánicas.

  4. Effects of Mo and Al addition on the Mechanical Properties of 15Cr ODS steel

    Shim, Jaewon; Noh, Sanghoon; Kang, Sukhoon; Chun, Youngbum; Choi, Byoungkwon; Han, Changhee; Kim, Taekyu [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2013-05-15

    Oxide particle controls the strength of the ODS steel and the addition of Mo, W, and Al, which changes the microstructures and remarkably influences the strength of ODS steel. In this study, Fe-based ODS alloys with Mo, W, and Al additions were fabricated by HIP and hot rolling processes, and their microstructures and mechanical properties were investigated. Some Fe-based ODS alloys were fabricated by a HIP process, and their microstructures and mechanical properties were investigated. Mo, W, and Al are considered to be very effective alloying elements for high strength and formability in Fe-based ODS alloys. As a result of a microstructure observation, grain refinement occurred in the case of the addition of W and Mo. However, the grain size and oxide particles of Fe-15Cr-ODS alloy Al added became coarse. Therefore, the hardness and tensile strength were decreased. On the other hand, the elongation was increased owing to the coarser grain. These preliminary results will be useful for developing advanced Fe-15Cr ODS alloy. The structural components for nuclear systems need to have formability as well as strength.

  5. Mechanical and Thermal Properties of Glass/Polyester Composite with Glycerol as Additive

    K.S.Siddharthan

    2014-01-01

    Full Text Available There has been an increasing interest to improve the mechanical properties of the polymer based laminated composites. In this paper, glycerol is used as a solvent to improve the mechanical properties of glass/polyester laminated composites. Polyester resin is modified with 0, 5 and 10 wt% of glycerol. Glycerol and polyester resin are synthesized by hand stirrer. Hand layup method is used to manufacture the laminate made of bi-directional glass woven roving mat and modified polyester. The effect of glycerol is validated by subjecting all samples to the laminate mechanical testing. Results revealed improvement in the mechanical properties of the composites subjected to direct tension and compression test at ambient temperature (27oC. Impact toughness is evaluated under both ambient and low temperature (-10oC conditions, as polyester resin is more brittle at low temperatures. Thermo gravimetric analysis results showed minor weight loss due to decrease in the cross-linking density of polyester with the addition of glycerol. It leads to the result that we can use this composite with glycerol as advanced material for wind turbine blade.

  6. Failure mechanisms of additively manufactured porous biomaterials: Effects of porosity and type of unit cell.

    Kadkhodapour, J; Montazerian, H; Darabi, A Ch; Anaraki, A P; Ahmadi, S M; Zadpoor, A A; Schmauder, S

    2015-10-01

    Since the advent of additive manufacturing techniques, regular porous biomaterials have emerged as promising candidates for tissue engineering scaffolds owing to their controllable pore architecture and feasibility in producing scaffolds from a variety of biomaterials. The architecture of scaffolds could be designed to achieve similar mechanical properties as in the host bone tissue, thereby avoiding issues such as stress shielding in bone replacement procedure. In this paper, the deformation and failure mechanisms of porous titanium (Ti6Al4V) biomaterials manufactured by selective laser melting from two different types of repeating unit cells, namely cubic and diamond lattice structures, with four different porosities are studied. The mechanical behavior of the above-mentioned porous biomaterials was studied using finite element models. The computational results were compared with the experimental findings from a previous study of ours. The Johnson-Cook plasticity and damage model was implemented in the finite element models to simulate the failure of the additively manufactured scaffolds under compression. The computationally predicted stress-strain curves were compared with the experimental ones. The computational models incorporating the Johnson-Cook damage model could predict the plateau stress and maximum stress at the first peak with less than 18% error. Moreover, the computationally predicted deformation modes were in good agreement with the results of scaling law analysis. A layer-by-layer failure mechanism was found for the stretch-dominated structures, i.e. structures made from the cubic unit cell, while the failure of the bending-dominated structures, i.e. structures made from the diamond unit cells, was accompanied by the shearing bands of 45°. PMID:26143351

  7. Fluid mechanics of additive manufacturing of metal objects by accretion of droplets – a survey

    Tesař Václav

    2016-01-01

    Full Text Available Paper presents a survey of principles of additive manufacturing of metal objects by accretion of molten metal droplets, focusing on fluid-mechanical problems that deserve being investigated. The main problem is slowness of manufacturing due to necessarily small size of added droplets. Increase of droplet repetition rate calls for basic research of the phenomena that take place inside and around the droplets: ballistics of their flight, internal flowfield with heat and mass transfer, oscillation of surfaces, and the ways to elimination of satellite droplets.

  8. Effects of Additive on the Mechanical Properties of Bamboo/pbs Composites

    Lee, Yeon-Hee; Yoon, Han-Ki; Takagi, Hitoshi; Ohkita, Kazuya

    Compared with general composites which are produced from fossil fuel, biodegradable resins have received considerable attention as an environment-friendly material. Bamboo fiber has relatively high strength compared with other natural fibers. Therefore, the focus of this study is to produce bamboo fiber reinforced Poly butylene succinate (PBS) composites by injection molding and to study the effects of additive on mechanical properties of this bamboo/PBS composite. The injection-molding is a highly productive fabrication technique. Bamboo/PBS composites were examined by flexural test and Vickers hardness. Also we examined fracture surface and microstructure of the bamboo/PBS composites by microscope.

  9. Fluid mechanics of additive manufacturing of metal objects by accretion of droplets - a survey

    Tesař, Václav

    2016-03-01

    Paper presents a survey of principles of additive manufacturing of metal objects by accretion of molten metal droplets, focusing on fluid-mechanical problems that deserve being investigated. The main problem is slowness of manufacturing due to necessarily small size of added droplets. Increase of droplet repetition rate calls for basic research of the phenomena that take place inside and around the droplets: ballistics of their flight, internal flowfield with heat and mass transfer, oscillation of surfaces, and the ways to elimination of satellite droplets.

  10. On Self-Recovery Mechanism and Additional Maneuverability of a Mini Mobile Robot

    1999-01-01

    Ordinary mobile robots have some kind of moving mechanisms attached to one rigid body. When working on rough terrain or in other hazard environments, there existed some possibilities that the robot will be turned up side down, thus causing losses to the robot's expedition. Multi-bodied mobile robots provide a solution to that problem. Using active joints between bodies, the robot can recover from turnover situation by itself. In this paper, the authors discuss the joint arrangements and the additional maneuverability resulted from joints between body segments.

  11. Exploring the mechanical strength of additively manufactured metal structures with embedded electrical materials

    Ultrasonic Additive Manufacturing (UAM) enables the integration of a wide variety of components into solid metal matrices due to the process induced high degree of metal matrix plastic flow at low bulk temperatures. Exploitation of this phenomenon allows the fabrication of previously unobtainable novel engineered metal matrix components. The feasibility of directly embedding electrical materials within UAM metal matrices was investigated in this work. Three different dielectric materials were embedded into UAM fabricated aluminium metal-matrices with, research derived, optimal processing parameters. The effect of the dielectric material hardness on the final metal matrix mechanical strength after UAM processing was investigated systematically via mechanical peel testing and microscopy. It was found that when the Knoop hardness of the dielectric film was increased from 12.1 HK/0.01 kg to 27.3 HK/0.01 kg, the mechanical peel testing and linear weld density of the bond interface were enhanced by 15% and 16%, respectively, at UAM parameters of 1600 N weld force, 25 µm sonotrode amplitude, and 20 mm/s welding speed. This work uniquely identified that the mechanical strength of dielectric containing UAM metal matrices improved with increasing dielectric material hardness. It was therefore concluded that any UAM metal matrix mechanical strength degradation due to dielectric embedding could be restricted by employing a dielectric material with a suitable hardness (larger than 20 HK/0.01 kg). This result is of great interest and a vital step for realising electronic containing multifunctional smart metal composites for future industrial applications

  12. A theoretical study of the mechanism of the addition reaction between carbene and azacyclopropane

    XIAOJUN TAN

    2010-05-01

    Full Text Available The mechanism of the addition reaction between carbene and azacyclopropane was investigated using the second-order Moller–Plesset perturbation theory (MP2. By using the 6-311+G* basis set, geometry optimization, vibrational analysis and the energy properties of the involved stationary points on the potential energy surface were calculated. From the surface energy profile, it can be predicted that there are two reaction mechanisms. The first one (1 is carbene attack at the N atom of azacyclopropane to form an intermediate, 1a (IM1a, which is a barrier-free exothermic reaction. Then, IM1a can isomerize to IM1b via a transition state 1a (TS1a, in which the potential barrier is 30.0 kJ/mol. Subsequently, IM1b isomerizes to a product (Pro1 via TS1b with a potential barrier of 39.3 kJ/mol. The other one (2 is carbene attack at the C atom of azacyclopropane, firstly to form IM2 via TS2a, the potential barrier is 35.4 kJ/mol. Then IM2 isomerizes to a product (Pro2 via TS2b with a potential barrier of 35.1 kJ/mol. Correspondingly, the reaction energy for the reactions (1 and (2 is –478.3 and –509.9 kJ/mol, respectively. Additionally, the orbital interactions are also discussed for the leading intermediate.

  13. TDDFT Study on Different Sensing Mechanisms of Similar Cyanide Sensors Based on Michael Addition Reaction

    Guang-yue Li; Ping Song; Guo-zhong He

    2011-01-01

    The solvents and substituents of two similar fluorescent sensors for cyanide, 7-diethylamino-3-formylcoumarin (sensor a) and 7-diethylamino-3-(2-nitrovinyl)coumarin (sensor b), are proposed to account for their distinct sensing mechanisms and experimental phenomena.The time-dependent density functional theory has been applied to investigate the ground states and the first singlet excited electronic states of the sensor as well as their possible Michael reaction products with cyanide, with a view to monitoring their geometries and photophysical properties. The theoretical study indicates that the protic water solvent could lead to final Michael addition product of sensor a in the ground state, while the aprotic acetonitrile solvent could lead to carbanion as the final product of sensor b. Furthermore,the Michael reaction product of sensor a has been proved to have a torsion structure in its first singlet excited state. Correspondingly, sensor b also has a torsion structure around the nitrovinyl moiety in its first singlet excited state, while not in its carbanion structure. This could explain the observed strong fluorescence for sensor a and the quenching fluorescencefor the sensor b upon the addition of the cyanide anions in the relevant sensing mechanisms.

  14. Possible Mechanism of ``Additional'' Production of H^- in a Glow Discharge

    Belostotskiy, S.; Economou, D.; Lopaev, D.; Rakhimova, T.

    2006-10-01

    Based on measurements of H^- and H densities a DC glow discharge in H2 (P=0.1-3 Torr) the rate coefficient of H^- production as a function of E/N was determined. To analyze the mechanisms of H^- production, a simple model of H2 vibrational excitation was developed. Estimations of vibrational level densities (v=3-5) obtained from VUV absorption measurements were in reasonable agreement with the calculated data. The analysis revealed that standard mechanisms of H^- production (dissociative attachment to vibrationally excited molecules H2(v) and molecules in Rydberg states H2(Ry)) were not enough to explain the experimental results. In order to describe both the shape (vs E/N) and the magnitude of the measured H^- production rate coefficient, an ``additional'' source of H^-, having a strong resonant electron attachment CS in the range of ˜5-9 eV, should be invoked. Although H2 has no resonances in the 5-9 eV range, water is known to strongly dissociatively attach in this range. Thus, even small amounts (0.1-1%) of water vapor in the apparatus can explain the origin of the ``additional'' H^- production. This result is corroborated by the work of Cadez et. al. in Proc. of XXVII ICPIG, 2005. This work was supported by the RFBR (No.05-02-17649a), Scientific School - 171113.2003.2 and NATO Collaborative Linkage Grant (No.980097).

  15. Mechanisms underlying the additive and redundant Qrr phenotypes in Vibrio harveyi and Vibrio cholerae.

    Hunter, Geoffrey A M; Keener, James P

    2014-01-01

    Vibrio harveyi and Vibrio cholerae regulate their virulence factors according to the local cell-population density in a regulatory system called quorum sensing. Their quorum sensing systems contain a small RNA (sRNA) circuit to regulate expression of a master transcriptional regulator via multiple quorum regulated RNA (Qrr) and a protein chaperon Hfq. Experiments and genetic analysis show that their respective quorum sensing networks are topologically equivalent and have homologous components, yet they respond differently to the same experimental conditions. In particular, V. harveyi Qrr are additive because all of its Qrr are required to maintain wild-type-like repression of its master transcriptional regulator. Conversely, V. cholerae Qrr are redundant because any of its Qrr is sufficient to repress its master transcriptional regulator. Given the striking similarities between their quorum sensing systems, experimentalists have been unable to identify conclusively the mechanisms behind these phenotypic differences. Nevertheless, the current hypothesis in the literature is that dosage compensation is the mechanism underlying redundancy. In this work, we identify the mechanisms underlying Qrr redundancy using a detailed mathematical model of the V. harveyi and V. cholerae sRNA circuits. We show that there are exactly two different cases underlying Qrr redundancy and that dosage compensation is unnecessary and insufficient to explain Qrr redundancy. Although V. harveyi Qrr are additive when the perturbations in Qrr are large, we predict that V. harveyi and V. cholerae Qrr are redundant when the perturbations in Qrr are small. We argue that the additive and redundant Qrr phenotypes can emerge from parametric differences in the sRNA circuit. In particular, we find that the affinity of Qrr and its expression relative to the master transcriptional regulator determine the level of redundancy in V. harveyi and V. cholerae. Furthermore, the additive and redundant Qrr

  16. Effect of additives for higher removal rate in lithium niobate chemical mechanical planarization

    High roughness and a greater number of defects were created by lithium niobate (LN; LiNbO3) processes such as traditional grinding and mechanical polishing (MP), should be decreased for manufacturing LN device. Therefore, an alternative process for gaining defect-free and smooth surface is needed. Chemical mechanical planarization (CMP) is suitable method in the LN process because it uses a combination approach consisting of chemical and mechanical effects. First of all, we investigated the LN CMP process using commercial slurry by changing various process conditions such as down pressure and relative velocity. However, the LN CMP process time using commercial slurry was long to gain a smooth surface because of lower material removal rate (MRR). So, to improve the material removal rate (MRR), the effects of additives such as oxidizer (hydrogen peroxide; H2O2) and complexing agent (citric acid; C6H8O7) in a potassium hydroxide (KOH) based slurry, were investigated. The manufactured slurry consisting of H2O2-citric acid in the KOH based slurry shows that the MRR of the H2O2 at 2 wt% and the citric acid at 0.06 M was higher than the MRR for other conditions.

  17. Design of a mechanical system in gait rehabilitation with progressive addition of weight

    Braidot, Ariel A. A.; Aleman, Guillermo L.

    2011-12-01

    In this paper we designed and developed a mechanical device for gait rehabilitation based on the application of "partial body weight reduction therapy". An evaluation of the characteristics of devices based on this therapy currently available on the market was carried out obtaining information of the different mechanisms used in it. The device was designed to adapt to different height and weight of patients and to be used with additional equipment in gait rehabilitation, for example, treadmills, elliptical trainers and vertical scalers. It was envisaged to be used by patients with asymmetry in the lower extremities capabilities. We developed a stable structure in steel ASTM A36 which does not depend on the building conditions of the installation site. RamAdvanse software was used to calculate structural stability. A winch with automatic brake mechanism was used to raise/lower the patient, who was tied to a comfortable harness which provided safety to the patient and therapist. It was possible to quantify precisely, using counterweights, the weight borne by the patient during therapy. We obtained a small-sized and ergonomic low-cost prototype, with similar features to those currently considered cutting-edge devices.

  18. Effect of alloying addition and microstructural parameters on mechanical properties of 93% tungsten heavy alloys

    Liquid phase sintering, heat treatment and swaging studies on three tungsten heavy alloys, 93W–4.9Ni–2.1Fe (wt%), 93W–4.2Ni–1.2Fe–1.6Co (wt%) and 93W–4.9Ni–1.9Fe–0.2Re (wt%) were carried out in detail with respect to microstructure, tensile and impact properties. All the alloys were sintered and swaged to 40% deformation. The results indicate that Re addition reduces the grain size of the alloy compared to W–Ni–Fe and W-Ni-Fe-Co alloys. W–Ni–Fe–Re alloy shows superior tensile properties in heat treated condition as compared to W–Ni–Fe and W–Ni–Fe–Co alloys. SEM study of fractured specimens clearly indicates that the failure in case of W–Ni–Fe–Re was due to transgranular cleavage of tungsten grains and W–W de-cohesion. W–Ni–Fe and W–Ni–Fe–Co alloys also failed by mixed mode failure. However, in these cases, ductile dimples corresponding the failure of the matrix phase was rarely seen. Thermo-mechanical processing resulted in significant changes in mechanical properties. While W–Ni–Fe–Re alloy showed the highest tensile strength (1380 MPa), W–Ni–Fe–Co exhibited the highest elongation (12%) to failure. A detailed analysis involving microstructure, mechanical properties and failure behavior was undertaken in order to understand the property trends

  19. Effect of alloying addition and microstructural parameters on mechanical properties of 93% tungsten heavy alloys

    Ravi Kiran, U., E-mail: uravikiran@gmail.com [Defence Metallurgical Research Laboratory, Kanchanbagh, Hyderabad 500 058 (India); Panchal, A.; Sankaranarayana, M. [Defence Metallurgical Research Laboratory, Kanchanbagh, Hyderabad 500 058 (India); Nageswara Rao, G.V.S. [National Institute of Technology, Warangal 506004 (India); Nandy, T.K. [Defence Metallurgical Research Laboratory, Kanchanbagh, Hyderabad 500 058 (India)

    2015-07-29

    Liquid phase sintering, heat treatment and swaging studies on three tungsten heavy alloys, 93W–4.9Ni–2.1Fe (wt%), 93W–4.2Ni–1.2Fe–1.6Co (wt%) and 93W–4.9Ni–1.9Fe–0.2Re (wt%) were carried out in detail with respect to microstructure, tensile and impact properties. All the alloys were sintered and swaged to 40% deformation. The results indicate that Re addition reduces the grain size of the alloy compared to W–Ni–Fe and W-Ni-Fe-Co alloys. W–Ni–Fe–Re alloy shows superior tensile properties in heat treated condition as compared to W–Ni–Fe and W–Ni–Fe–Co alloys. SEM study of fractured specimens clearly indicates that the failure in case of W–Ni–Fe–Re was due to transgranular cleavage of tungsten grains and W–W de-cohesion. W–Ni–Fe and W–Ni–Fe–Co alloys also failed by mixed mode failure. However, in these cases, ductile dimples corresponding the failure of the matrix phase was rarely seen. Thermo-mechanical processing resulted in significant changes in mechanical properties. While W–Ni–Fe–Re alloy showed the highest tensile strength (1380 MPa), W–Ni–Fe–Co exhibited the highest elongation (12%) to failure. A detailed analysis involving microstructure, mechanical properties and failure behavior was undertaken in order to understand the property trends.

  20. Design of a mechanical system in gait rehabilitation with progressive addition of weight

    In this paper we designed and developed a mechanical device for gait rehabilitation based on the application of partial body weight reduction therapy. An evaluation of the characteristics of devices based on this therapy currently available on the market was carried out obtaining information of the different mechanisms used in it. The device was designed to adapt to different height and weight of patients and to be used with additional equipment in gait rehabilitation, for example, treadmills, elliptical trainers and vertical scalers. It was envisaged to be used by patients with asymmetry in the lower extremities capabilities. We developed a stable structure in steel ASTM A36 which does not depend on the building conditions of the installation site. RamAdvanse software was used to calculate structural stability. A winch with automatic brake mechanism was used to raise/lower the patient, who was tied to a comfortable harness which provided safety to the patient and therapist. It was possible to quantify precisely, using counterweights, the weight borne by the patient during therapy. We obtained a small-sized and ergonomic low-cost prototype, with similar features to those currently considered cutting-edge devices.

  1. Mechanisms of fetal and neonatal renal impairment by pharmacologic inhibition of angiotensin.

    Chevalier, Robert L

    2012-01-01

    The renin-angiotensin system is highly conserved through evolutionary history, and has multiple functions in addition to maintaining cardiovascular homeostasis: these include the regulation of renal cell survival and cell death, and development of the kidney. The importance of angiotensin (ANG) in normal kidney development was first recognized in infants with renal maldevelopment born to mothers treated with angiotensin converting enzyme (ACE) inhibitors or with ANG AT1 receptor blockers. The molecular role of ANG in renal development has been elucidated using gene targeting in mice, revealing major effects in branching morphogenesis, vasculogenesis, development of the papilla and renal concentrating mechanism. Although exposure of the fetus to ANG inhibitors is potentially harmful throughout pregnancy, effects are greater in late compared to early gestation. Significant differences between humans and rodents in placental transfer of ANG and timing of renal development contributed to initial delays in recognizing the teratogenic effects of ANG inhibitors. Although administration of ACE or AT1 receptor inhibitors can slow progression of renal disease in older children, ANG inhibition in the neonatal period can aggravate renal injury due to congenital urinary tract obstruction. Neonates are also far more sensitive than older children to the hypotensive actions these agents and doses must be markedly reduced to avoid precipitating oliguria. Understanding the complex interactions of the maturing renin-angiotensin system in the perinatal period is essential in the use of ANG or renin inhibitors in women during childbearing years or in neonates with cardiovascular or renal disease. PMID:22876894

  2. Effect of boron and carbon addition on microstructure and mechanical properties of metastable beta titanium alloys

    Highlights: • Effect of boron and carbon on properties of three beta titanium alloys studied. • Ti–15V–3Cr–3Mo–3Sn, Ti–10V–2Fe–3Al, and Ti–5V–5Mo–5Al–3Cr alloys studied. • Hardness and 0.2% YS increases and elongation to failure deteriorates with the B and C addition. • Ageing in comparison to solution treatment results in increase in strength and decrease in elongation. • Low ‘n′ values and multiple slopes are observed in log–log plots of true stress–true strain curves. - Abstract: Effect of boron and carbon on microstructure and mechanical properties of β titanium alloys Ti–15V–3Cr–3Mo–3Sn, Ti–10V–2Fe–3Al, and Ti–5V–5Mo–5Al–3Cr has been studied in detail. The addition of boron and carbon results in refinement of β grain size and α-precipitates during ageing. While the hardness and tensile strength increase with the addition of boron and carbon, the elongation to failure deteriorates. The increase in strength is attributed to a synergistic effect of grain refinement and load sharing by TiB and TiC particles; whereas decrease in elongation is due to the brittleness of these hard particles. Ageing results in increase in strength and decrease in elongation as compared to solution treatment condition. In this case, the effect of boron and carbon is marginal. Further enhancement in the properties can be achieved by fine tuning heat treatment parameters. Multiple slopes are observed in log–log plots of true stress–true strain thereby implying different deformation mechanisms over a large range of plastic deformation

  3. DEHP exposure impairs mouse oocyte cyst breakdown and primordial follicle assembly through estrogen receptor-dependent and independent mechanisms

    Mu, Xinyi [Laboratory of Reproductive Biology, Chongqing Medical University, Chongqing 400016 (China); Department of Histology and Embryology, College of Basic Medicine, Chongqing Medical University, Chongqing 400016 (China); Liao, Xinggui; Chen, Xuemei; Li, Yanli; Wang, Meirong; Shen, Cha; Zhang, Xue; Wang, Yingxiong; Liu, Xueqing [Laboratory of Reproductive Biology, Chongqing Medical University, Chongqing 400016 (China); He, Junlin, E-mail: hejunlin_11@aliyun.com [Laboratory of Reproductive Biology, Chongqing Medical University, Chongqing 400016 (China)

    2015-11-15

    Highlights: • DEHP inhibits primordial folliculogenesis in vivo and in vitro. • Estrogen receptors participate in the effect of DEHP on early ovarian development. • DEHP exposure impairs the expression of Notch2 signaling components. • DEHP exposure disrupts the proliferation of pregranulosa precursor cells. - Abstract: Estrogen plays an essential role in the development of mammalian oocytes, and recent studies suggest that it also regulates primordial follicle assembly in the neonatal ovaries. During the last decade, potential exposure of humans and animals to estrogen-like endocrine disrupting chemicals has become a growing concern. In the present study, we focused on the effect of diethylhexyl phthalate (DEHP), a widespread plasticizer with estrogen-like activity, on germ-cell cyst breakdown and primordial follicle assembly in the early ovarian development of mouse. Neonatal mice injected with DEHP displayed impaired cyst breakdown. Using ovary organ cultures, we revealed that impairment was mediated through estrogen receptors (ERs), as ICI 182,780, an efficient antagonist of ER, reversed this DEHP-mediated effect. DEHP exposure reduced the expression of ERβ, progesterone receptor (PR), and Notch2 signaling components. Finally, DEHP reduced proliferation of pregranulosa precursor cells during the process of primordial folliculogenesis. Together, our results indicate that DEHP influences oocyte cyst breakdown and primordial follicle formation through several mechanisms. Therefore, exposure to estrogen-like chemicals during fetal or neonatal development may adversely influence early ovarian development.

  4. DEHP exposure impairs mouse oocyte cyst breakdown and primordial follicle assembly through estrogen receptor-dependent and independent mechanisms

    Highlights: • DEHP inhibits primordial folliculogenesis in vivo and in vitro. • Estrogen receptors participate in the effect of DEHP on early ovarian development. • DEHP exposure impairs the expression of Notch2 signaling components. • DEHP exposure disrupts the proliferation of pregranulosa precursor cells. - Abstract: Estrogen plays an essential role in the development of mammalian oocytes, and recent studies suggest that it also regulates primordial follicle assembly in the neonatal ovaries. During the last decade, potential exposure of humans and animals to estrogen-like endocrine disrupting chemicals has become a growing concern. In the present study, we focused on the effect of diethylhexyl phthalate (DEHP), a widespread plasticizer with estrogen-like activity, on germ-cell cyst breakdown and primordial follicle assembly in the early ovarian development of mouse. Neonatal mice injected with DEHP displayed impaired cyst breakdown. Using ovary organ cultures, we revealed that impairment was mediated through estrogen receptors (ERs), as ICI 182,780, an efficient antagonist of ER, reversed this DEHP-mediated effect. DEHP exposure reduced the expression of ERβ, progesterone receptor (PR), and Notch2 signaling components. Finally, DEHP reduced proliferation of pregranulosa precursor cells during the process of primordial folliculogenesis. Together, our results indicate that DEHP influences oocyte cyst breakdown and primordial follicle formation through several mechanisms. Therefore, exposure to estrogen-like chemicals during fetal or neonatal development may adversely influence early ovarian development

  5. Research on the multicast mechanism based on physical-layer-impairment awareness model for OpenFlow optical network

    Bai, Hui-feng; Zhou, Zi-guan; Song, Yan-bin

    2016-05-01

    A physical-layer-impairment (PLI)-awareness based optical multicast mechanism is proposed for OpenFlow controlled optical networks. This proposed approach takes the PLI models including linear and non-linear factors into optical multicast controlled by OpenFlow protocol. Thus, the proposed scheme is able to cover nearly all PLI factors of each optical link and to conduct optical multicast with better communication quality. Simulation results show that the proposed scheme can obtain the better performance of OpenFlow controlled optical multicast services.

  6. Mechanical forces impair alveolar ion transport processes : A putative mechanism contributing to the formation of pulmonary edema

    Fronius, Martin

    2012-01-01

    The aim of this chapter is to highlight the importance of transepithelial ion transport processes for lung function in general and to focus on the impact of mechanical forces on pulmonary ion transport in particular. Linking mechanical forces with pulmonary ion transport derives from the fact that the lung is a dynamic organ as well as from several studies providing evidence that the amount of mechanical forces as used during artificial ventilation correlates with mortality rates in patients...

  7. Mechanical properties of fine grained superalloy K4169 with addition of refiners

    HUANG Tai-wen; LIU Lin; YANG Ai-min; XIONG Yu-hua; ZHANG Rong

    2005-01-01

    Grain refinement of superalloy K4169 was achieved by adding refiners into the alloy melt and their effects on the mechanical properties were investigated. The tensile properties at room temperature and 700 ℃ and low cycle fatigue properties at room temperature were compared for both conventional and fine grained test bars.The results indicate that the rupture strength, yield strength, elongation and reduction of area for refined grains are all much superior to those for coarse ones. Whereas the elongation and reduction of area of fine grained samples decrease at 700 ℃. Low cycle fatigue properties of samples with refined grains at room temperature are improved significantly. In addition, the degree of dispersion of low cycle fatigue data of samples with refined grains is diminished.

  8. Mechanism of weld formation during very-high-power ultrasonic additive manufacturing of Al alloy 6061

    The microstructures of Al alloy 6061 subjected to very-high-power ultrasonic additive manufacturing were systematically examined to understand the underlying ultrasonic welding mechanism. The microstructure of the weld interface between the metal tapes consisted of fine, equiaxed grains resulting from recrystallization, which is driven by simple shear deformation along the ultrasonically vibrating direction of the tape surface. Void formation at the weld interface is attributed to surface asperities resulting from pressure induced by the sonotrode at the initial tape deposition. Transmission electron microscopy revealed that Al–Al metallic bonding without surface oxide layers was mainly achieved, although some oxide clusters were locally observed at the original interface. The results suggest that the oxide layers were broken up and then locally clustered on the interface by ultrasonic vibration

  9. Effects of organic additives on microstructure and mechanical properties of porous Si3N4 ceramics

    Yu Fangli; Wang Huanrui; Yang Jianfeng; Gao Jiqiang

    2010-06-01

    Green bodies of porous Si3N4 ceramics were shaped by extrusion technique using different organic additives as binder during extrusion molding. Different porosity, microstructures and mechanical properties after the extrusion, drying, debinding and sintering stages were investigated. The solid slurry content of 70–75% and extrusion pressure of 0.5–1.0 MPa had played a decisive role in the smooth realization of extrusion molding. The porous Si3N4 ceramics were obtained with excellent properties using 4% hydroxypropyl methyl cellulose (HPMC) as binder and polyethylene glycol (PEG) of molecular weight, 1000, as plasticizer with a density of 1.91 g cm-3, porosity of 41.70%, three-point bending strength of 166.53 ± 20 MPa, fracture toughness of 2.45 ± 0.2 MPa m1/2 and Weibull modulus (m) of 20.75.

  10. Mechanical Characterization of an Additively Manufactured Inconel 718 Theta-Shaped Specimen

    Cakmak, Ercan; Watkins, Thomas R.; Bunn, Jeffrey R.; Cooper, Ryan C.; Cornwell, Paris A.; Wang, Yanli; Sochalski-Kolbus, Lindsay M.; Dehoff, Ryan R.; Babu, Sudarsanam S.

    2016-02-01

    Two sets of "theta"-shaped specimens were additively manufactured with Inconel 718 powders using an electron beam melting technique with two distinct scan strategies. Light optical microscopy, mechanical testing coupled with a digital image correlation (DIC) technique, finite element modeling, and neutron diffraction with in situ loading characterizations were conducted. The cross-members of the specimens were the focus. Light optical micrographs revealed that different microstructures were formed with different scan strategies. Ex situ mechanical testing revealed each build to be stable under load until ductility was observed on the cross-members before failure. The elastic moduli were determined by forming a correlation between the elastic tensile stresses determined from FEM, and the elastic strains obtained from DIC. The lattice strains were mapped with neutron diffraction during in situ elastic loading; and a good correlation between the average axial lattice strains on the cross-member and those determined from the DIC analysis was found. The spatially resolved stresses in the elastic deformation regime are derived from the lattice strains and increased with applied load, showing a consistent distribution along the cross-member.

  11. Novel Additive Manufacturing Pneumatic Actuators and Mechanisms for Food Handling Grippers

    Carlos Blanes

    2014-07-01

    Full Text Available Conventional pneumatic grippers are widely used in industrial pick and place robot processes for rigid objects. They are simple, robust and fast, but their design, motion and features are limited, and they do not fulfil the final purpose. Food products have a wide variety of shapes and textures and are susceptible to damaged. Robot grippers for food handling should adapt to this wide range of dimensions and must be fast, cheap, reasonably reliable, and with cheap and reasonable maintenance costs. They should not damage the product and must meet hygienic conditions. The additive manufacturing (AM process is able to manufacture parts without significant restrictions, and is Polyamide approved as food contact material by FDA. This paper presents that, taking the best of plastic flexibility, AM allows the implementation of novel actuators, original compliant mechanisms and practical grippers that are cheap, light, fast, small and easily adaptable to specific food products. However, if they are not carefully designed, the results can present problems, such as permanent deformations, low deformation limits, and low operation speed. We present possible solutions for the use of AM to design proper robot grippers for food handling. Some successful results, such as AM actuators based on deformable air chambers, AM compliant mechanisms, and grippers developed in a single part will be introduced and discussed.

  12. The Effect of Structural Design on Mechanical Properties and Cellular Response of Additive Manufactured Titanium Scaffolds

    Jan Wieding

    2012-08-01

    Full Text Available Restoration of segmental defects in long bones remains a challenging task in orthopedic surgery. Although autologous bone is still the ‘Gold Standard’ because of its high biocompatibility, it has nevertheless been associated with several disadvantages. Consequently, artificial materials, such as calcium phosphate and titanium, have been considered for the treatment of bone defects. In the present study, the mechanical properties of three different scaffold designs were investigated. The scaffolds were made of titanium alloy (Ti6Al4V, fabricated by means of an additive manufacturing process with defined pore geometry and porosities of approximately 70%. Two scaffolds exhibited rectangular struts, orientated in the direction of loading. The struts for the third scaffold were orientated diagonal to the load direction, and featured a circular cross-section. Material properties were calculated from stress-strain relationships under axial compression testing. In vitro cell testing was undertaken with human osteoblasts on scaffolds fabricated using the same manufacturing process. Although the scaffolds exhibited different strut geometry, the mechanical properties of ultimate compressive strength were similar (145–164 MPa and in the range of human cortical bone. Test results for elastic modulus revealed values between 3.7 and 6.7 GPa. In vitro testing demonstrated proliferation and spreading of bone cells on the scaffold surface.

  13. Mechanically tunable aspheric lenses via additive manufacture of hanging elastomeric droplets for microscopic applications

    Fuh, Yiin-Kuen; Chen, Pin-Wen; Lai, Zheng-Hong

    2016-07-01

    Mechanically deformable lenses with dynamically tunable focal lengths have been developed in this work. The fabricated five types of aspheric polydimethylsiloxane (PDMS) lenses presented here have an initial focal length of 7.0, 7.8, 9.0, 10.0 and 10.2 mm. Incorporating two modes of operation in biconvex and concave-convex configurations, the focal lengths can be tuned dynamically as 5.2-10.2, 5.5-9.9, 6.6-11.9, 6.1-13.5 and 6.6-13.5 mm respectively. Additive manufacturing was utilized to fabricate these five types of aspheric lenses (APLs) via sequential layering of PDMS materials. Complex structures with three-dimensional features and shorter focal lengths can be successfully produced by repeatedly depositing, inverting and curing controlled PDMS volume onto previously cured PDMS droplets. From our experiments, we empirically found a direct dependence of the focal length of the lenses with the amount (volume) of deposited PDMS droplets. This new mouldless, low-cost, and flexible lens fabrication method is able to transform an ordinary commercial smartphone camera into a low-cost portable microscope. A few microscopic features can be readily visualized, such as wrinkles of ladybird pupa and printed circuit board. The fabrication technique by successively applying hanging droplet and facile mechanical focal-length-tuning set-up can be easily adopted in the development of high-performance optical lenses.

  14. Beyond Mutations: Additional Mechanisms and Implications of SWI/SNF Complex Inactivation

    Stefanie eMarquez

    2015-02-01

    Full Text Available SWI/SNF is a major regulator of gene expression. Its role is to facilitate the shifting and exposure of DNA segments within the promoter and other key domains to transcription factors and other essential cellular proteins. This complex interacts with a wide range of proteins and does not function within a single, specific pathway; thus, it is involved in a multitude of cellular processes, including DNA repair, differentiation, development, cell adhesion, and growth control. Given SWI/SNF’s prominent role in these processes, many of which are important for blocking cancer development, it is not surprising that the SWI/SNF complex is targeted during cancer initiation and progression both by mutations and by nonmutational mechanisms. Currently, the understanding of the types of alterations, their frequency, and their impact on the SWI/SNF subunits is an area of intense research that has been bolstered by a recent cadre of NextGen sequencing studies. These studies have revealed mutations in SWI/SNF subunits, indicating that this complex is thus important for cancer development. The purpose of this review is to put into perspective the role of mutations versus other mechanisms in the silencing of SWI/SNF subunits, in particular, BRG1 and BRM. In addition, this review explores the recent development of synthetic lethality and how it applies to this complex, as well as how BRM polymorphisms are becoming recognized as potential clinical biomarkers for cancer risk.

  15. Effect of addition of semi refined carrageenan on mechanical characteristics of gum arabic edible film

    Setyorini, D.; Nurcahyani, P. R.

    2016-04-01

    Currently the seaweed is processed flour and Semi Refined Carraagenan (SRC). However, total production is small, but both of these products have a high value and are used in a wide variety of products such as cosmetics, processed foods, medicines, and edible film. The aim of this study were (1) to determine the effect of SRC on mechanical characteristics of edible film, (2) to determine the best edible film which added by SRC with different concentration. The edible film added by SRC flour which divided into three concentrations of SRC. There are 1.5%; 3%; and 4.5% of SRC, then added 3% glycerol and 0.6% arabic gum. The mechanical properties of the film measured by a universal testing machine Orientec Co. Ltd., while the water vapor permeability measured by the gravimetric method dessicant modified. The experimental design used was completely randomized design with a further test of Duncan. The result show SRC concentration differences affect the elongation breaking point and tensile strength. But not significant effect on the thickness, yield strength and the modulus of elasticity. The best edible film is edible film with the addition of SRC 4.5%.

  16. Thermal degradation mechanism of addition-cure liquid silicone rubber with urea-containing silane

    Highlights: • The urea-containing silane was incorporated into addition-cure liquid silicone rubber (ALSR) via hydrosilylation reaction. • The thermal stability of the ALSR was improved by DEUPAS both in nitrogen and air • The TG–FTIR of evolved gases during degradation was performed. • The possible degradation mechanism of the ALSR samples was proposed. - Abstract: The reactive urea-containing silane, (γ-diethylureidopropyl) allyloxyethoxysilane (DEUPAS), was synthesized by the trans-etherification reaction. The chemical structure was characterized by Fourier transform infrared spectrometry (FTIR) and 1H nuclear magnetic resonance spectrometry (1H NMR). Subsequently, DEUPAS was incorporated into addition-cure liquid silicone rubber (ALSR) via hydrosilylation reaction. The thermal stability of the ALSR samples was investigated by thermogravimetry (TG) and thermogravimetry–Fourier transform infrared spectrometry (TG–FTIR). When DEUPAS was incorporated, the temperature of 10% weight loss and 20% weight loss under air atmosphere were respectively increased by 31 °C and 60 °C compared with those of the ALSR without DEUPAS. Meanwhile, the residual weight at 800 °C increased from 33.5% to 58.7%. It was found that the striking enhancement in thermal stability of the ALSR samples was likely attributed to the decomposition of the urea groups to isocyanic acid, which reacted with hydroxyl groups to inhibit the unzipping depolymerization

  17. Thermal degradation mechanism of addition-cure liquid silicone rubber with urea-containing silane

    Fang, Weizhen; Zeng, Xingrong, E-mail: psxrzeng@gmail.com; Lai, Xuejun; Li, Hongqiang; Chen, Wanjuan; Zhang, Yajun

    2015-04-10

    Highlights: • The urea-containing silane was incorporated into addition-cure liquid silicone rubber (ALSR) via hydrosilylation reaction. • The thermal stability of the ALSR was improved by DEUPAS both in nitrogen and air • The TG–FTIR of evolved gases during degradation was performed. • The possible degradation mechanism of the ALSR samples was proposed. - Abstract: The reactive urea-containing silane, (γ-diethylureidopropyl) allyloxyethoxysilane (DEUPAS), was synthesized by the trans-etherification reaction. The chemical structure was characterized by Fourier transform infrared spectrometry (FTIR) and {sup 1}H nuclear magnetic resonance spectrometry ({sup 1}H NMR). Subsequently, DEUPAS was incorporated into addition-cure liquid silicone rubber (ALSR) via hydrosilylation reaction. The thermal stability of the ALSR samples was investigated by thermogravimetry (TG) and thermogravimetry–Fourier transform infrared spectrometry (TG–FTIR). When DEUPAS was incorporated, the temperature of 10% weight loss and 20% weight loss under air atmosphere were respectively increased by 31 °C and 60 °C compared with those of the ALSR without DEUPAS. Meanwhile, the residual weight at 800 °C increased from 33.5% to 58.7%. It was found that the striking enhancement in thermal stability of the ALSR samples was likely attributed to the decomposition of the urea groups to isocyanic acid, which reacted with hydroxyl groups to inhibit the unzipping depolymerization.

  18. Addition of vasopressin synthetic analogue [V(4)Q(5)]dDAVP to standard chemotherapy enhances tumour growth inhibition and impairs metastatic spread in aggressive breast tumour models.

    Garona, Juan; Pifano, Marina; Pastrian, Maria B; Gomez, Daniel E; Ripoll, Giselle V; Alonso, Daniel F

    2016-08-01

    [V(4)Q(5)]dDAVP is a novel 2nd generation vasopressin analogue with robust antitumour activity against metastatic breast cancer. We recently reported that, by acting on vasopressin V2r membrane receptor present in tumour cells and microvascular endothelium, [V(4)Q(5)]dDAVP inhibits angiogenesis and metastatic progression of the disease without overt toxicity. Despite chemotherapy remaining as a primary therapeutic option for aggressive breast cancer, its use is limited by low selectivity and associated adverse effects. In this regard, we evaluated potential combinational benefits by adding [V(4)Q(5)]dDAVP to standard-of-care chemotherapy. In vitro, combination of [V(4)Q(5)]dDAVP with sub-IC50 concentrations of paclitaxel or carmustine resulted in a cooperative inhibition of breast cancer cell growth in comparison to single-agent therapy. In vivo antitumour efficacy of [V(4)Q(5)]dDAVP addition to chemotherapy was first evaluated using the triple-negative MDA-MB-231 breast cancer xenograft model. Tumour-bearing mice were treated with i.v. injections of [V(4)Q(5)]dDAVP (0.3 μg/kg, thrice weekly) in combination with weekly cycles of paclitaxel (10 mg/kg i.p.). After 6 weeks of treatment, combination regimen resulted in greater tumour growth inhibition compared to monotherapy. [V(4)Q(5)]dDAVP addition was also associated with reduction of local aggressiveness, and impairment of tumour invasion and infiltration of the skin. Benefits of combined therapy were confirmed in the hormone-independent and metastatic F3II breast cancer model by combining [V(4)Q(5)]dDAVP with carmustine (25 mg/kg i.p.). Interestingly, [V(4)Q(5)]dDAVP plus cytotoxic agents severely impaired colony forming ability of tumour cells and inhibited breast cancer metastasis to lung. The present study shows that [V(4)Q(5)]dDAVP may complement conventional chemotherapy by modulating metastatic progression and early stages of microtumour establishment, and thus supports further preclinical testing of

  19. The Possible Mechanisms of the Impaired Insulin Secretion in Hypothyroid Rats.

    Aliashraf Godini

    Full Text Available Although the insulin secretion deficit in hypothyroid male rats has been documented, the underling mechanisms of the effect of hypothyroidism on insulin secretion are not clear. Isolated islets of the PTU-induced hypothyroid and control rats were exposed to glibenclamide, acetylcholine, and nifedipine in the presence of glucose concentrations of 2.8 or 8.3 and 16.7 mmol/L. Glucokinase and hexokinase specific activity, glucokinase content, and glucose transporter 2 protein expression were also determined in the isolated islets. Isolated islets from the hypothyroid rats showed a defect in insulin secretion in response to high glucose. In the presence of glibenclamide or acetylcholine, the isolated islets from the hypothyroid and control rats stimulated by glucose concentration of 16.7 mmol/L secreted similar amounts of insulin. In the presence of glucose concentrations of 8.3 mmol/L and 16.7 mmol/L, nifedipine was able to diminish insulin secretion from isolated islets of both groups, indicating that probably the defect may not arise from L type calcium channels or the steps beyond depolarization or the elements involved in the acetylcoline signaling pathway. Glucokinase content and hexokinase specific activity were also the same in the control and hypothyroid groups. On the other hand, glucokinase specific activity and glucose transporter 2 protein expression were significantly (p<0.001 and p<0.01 respectively lower in the islets isolated from the hypothyroid rats (6.50 ± 0.46 mU/min/mg protein and 0.55 ± 0.09 arbitrary unit compared to the controls (10.93 ± 0.83 mU/min/mg protein and 0.98 ± 0.07 arbitrary unit respectively. In conclusion, the results of this study indicated that hypothyroidism reduced insulin secretion from isolated pancreatic islets, which confirms the finding of the previous studies; in addition, the insulin secretion deficit observed in hypothyroid rats may arise from the abnormalities in some parts of the glucose sensor

  20. Increased Oxidation as an Additional Mechanism Underlying Reduced Clot Permeability and Impaired Fibrinolysis in Type 2 Diabetes

    Anna Lados-Krupa

    2015-01-01

    Full Text Available Aims. We sought to investigate whether enhanced oxidation contributes to unfavorable fibrin clot properties in patients with diabetes. Methods. We assessed plasma fibrin clot permeation (Ks, a measure of the pore size in fibrin networks and clot lysis time induced by recombinant tissue plasminogen activator (CLT in 163 consecutive type 2 diabetic patients (92 men and 71 women aged 65 ± 8.8 years with a mean glycated hemoglobin (HbA1c of 6.8%. We also measured oxidative stress markers, including nitrotyrosine, the soluble form of receptor for advanced glycation end products (sRAGE, 8-iso-prostaglandin F2α (8-iso-PGF2α, oxidized low-density lipoprotein (oxLDL, and advanced glycation end products (AGE. Results. There were inverse correlations between Ks and nitrotyrosine, sRAGE, 8-iso-PGF2α, and oxLDL. CLT showed a positive correlation with oxLDL and nitrotyrosine but not with other oxidation markers. All these associations remained significant for Ks after adjustment for fibrinogen, disease duration, and HbA1c (all P<0.05, while oxLDL was the only independent predictor of CLT. Conclusions. Our study shows that enhanced oxidative stress adversely affects plasma fibrin clot properties in type 2 diabetic patients, regardless of disease duration and glycemia control.

  1. Nearest-neighbor non-additivity versus long-range non-additivity in TATA-box structure and its implications for TBP-binding mechanism

    Faiger, Hana; Ivanchenko, Marina; Haran, Tali E.

    2007-01-01

    TBP recognizes its target sites, TATA boxes, by recognizing their sequence-dependent structure and flexibility. Studying this mode of TATA-box recognition, termed ‘indirect readout’, is important for elucidating the binding mechanism in this system, as well as for developing methods to locate new binding sites in genomic DNA. We determined the binding stability and TBP-induced TATA-box bending for consensus-like TATA boxes. In addition, we calculated the individual information score of all st...

  2. Ti-6Al-4V Additively Manufactured by Selective Laser Melting with Superior Mechanical Properties

    Xu, W.; Sun, S.; Elambasseril, J.; Liu, Q.; Brandt, M.; Qian, M.

    2015-03-01

    The Achilles' heel of additively manufactured Ti-6Al-4V by selective laser melting (SLM) is its inferior mechanical properties compared with its wrought (forged) counterparts. Acicular α' martensite resulted from rapid cooling by SLM is primarily responsible for high strength but inadequate tensile ductility achieved in the as-fabricated state. This study presents a solution to eliminating the adverse effect of the nonequilibrium α' martensite. This is achieved by enabling in situ martensite decomposition into a novel ultrafine (200-300 nm) lamellar ( α + β) microstructure via the selection of an array of processing variables including the layer thickness, energy density, and focal offset distance. The resulting tensile elongation reached 11.4% while the yield strength was kept above 1100 MPa. These properties compare favorably with those of mill-annealed Ti-6Al-4V consisting of globular α and β. The fatigue life of SLM-fabricated Ti-6Al-4V with an ultrafine lamellar ( α + β) structure has approached that of the mill-annealed counterparts and is much superior to that of SLM-fabricated Ti-6Al-4V with α' martensite.

  3. Effect of sulfur aggregates on mechanical resistance and durability for SFRHPC with the addition of slag

    Boutiba Aldjia

    2014-04-01

    Full Text Available The transformation of sulfides present in the aggregate to sulfates causes internal sulfate attack (ISA by formation of secondary ettringite in the hardened concrete. This pathological ettringite crystallizes, the generated pressure is greater than the tensile strength of the concrete. It generates internal swelling and causes disorders that can severely damage the structures. Favors to their structural and economic performance, high performance concrete steel fiber (SFRHPC are increasingly used in construction. Increase productivity and reduce construction time on site. They provide substantial weight savings, therefore it is possible to build with less formwork, less concrete to set up and fewer reinforcement than ordinary concrete. The purpose of this study is to determine the effect of sulfur present in the hornfels crushed aggregates, on the mechanical strength, durability, and the microstructure of SFRHPC with the addition of blast furnace slag. In ordinary concrete, the pyrite aggregates cause cracking by expansion when they are in wet land. In high performance concretes this phenomenon is greatly reduced or absent. This is the result of a very low porosity, reduced flow of moisture that cannot propagate to aggregate. And sulfide is stable and cannot be transformed into aggressive sulfate.

  4. Modification mechanism of hypereutectic Al-Si alloy with P-Na addition

    吴树森; 涂小林; 福田葉椰; 菅野利猛; 中江秀雄

    2003-01-01

    Effect of P-Na united modification on Al-22%Si-1.0%Cu-0.5%Mg-0.5%Mn alloy was studied.The results show that the refining effect of P-Na addition on primary silicon is superior to that of P and the former could modify eutectic silicon at the same time.Effects of P-Na modification on crystallization and microstructure of hypereutectic Al-Si alloys were studied with Electron-Scanning Microscope,Electron-Probe and X-ray diffractometer.The modification mechanism represents that on one hand,the primary silicon is refined by AlP as heterogeneous nucleus;on the other hand,when Na is added at the same time,P atoms are difficult to diffuse in the melt,and then enrichs on the growing faces of silicon phase.Moreover,a SiP compound was also discovered in Si crystals,which prevents the growth of silicon phase and refines the primary silicon.

  5. Additional funding mechanisms for Public Hospitals in Greece: the case of Chania Mental Health Hospital

    Golna Christina

    2010-11-01

    Full Text Available Abstract Objectives To investigate whether the long term lease of public hospital owned land could be an additional financing mechanism for Greek public (mental health hospitals. Methods We performed a financial analysis of the official 2008 data of a case - study hospital (Mental Health Hospital of Chania. We used a capital budgeting approach to investigate whether value is created for the public hospital by engaging its assets in a project for the development of a private renal dialysis Unit. Results The development of the private unit in hospital owned land is a good investment decision, as it generates high project Net Present Value and Internal Rate of Return. When the project commences generating operating cash flows, nearly €400.000 will be paid annually to the Mental Health Hospital of Chania as rent, thereby gradually decreasing the annual deficit of the hospital. Conclusions Revenue generated from the long term lease of public hospital land is crucial to gradually eliminate hospital deficit. The Ministry of Health should encourage similar forms of Public Private Partnerships in order to ensure the sustainability of public (mental hospitals.

  6. Gamma ray attenuation studies of interception from Sitka spruce: some evidence for an additional transport mechanism

    Various forest canopy characteristics of stands of Sitka spruce (Picea sitchensis (Bong.) Carr.), including canopy density, the aerodynamic resistance to the transfer of water vapor, and the rates of change of drainage and evaporation of water with respect to canopy storage, were investigated using direct measurements of canopy mass and water storage. The measurements, made at sites located in Wales and Scotland, utilized the attenuation of a horizontal beam of gamma rays which was arranged to scan through the canopy at different levels. The aerodynamic resistance to the transport of water vapor from the canopy to a reference level 5 m above mean tree height was found to be consistent with the value of 3.5 s m−1, determined from earlier modeling studies (I. R. Calder, 1977). This value is, however, lower and shows less wind speed dependence than would be expected from conventional formulae which are based on eddy diffusion theory and tree height. The possibility of explaining these discrepancies in terms of an additional transport mechanism involving large-scale eddies is discussed

  7. Scanning patterns of faces do not explain impaired emotion recognition in Huntington Disease: Evidence for a high level mechanism

    Mariekevan Asselen

    2012-02-01

    Full Text Available Previous studies in patients with amygdala lesions suggested that deficits in emotion recognition might be mediated by impaired scanning patterns of faces. Here we investigated whether scanning patterns also contribute to the selective impairment in recognition of disgust in Huntington disease (HD. To achieve this goal, we recorded eye movements during a two-alternative forced choice emotion recognition task. HD patients in presymptomatic (n=16 and symptomatic (n=9 disease stages were tested and their performance was compared to a control group (n=22. In our emotion recognition task, participants had to indicate whether a face reflected one of six basic emotions. In addition, and in order to define whether emotion recognition was altered when the participants were forced to look at a specific component of the face, we used a second task where only limited facial information was provided (eyes/mouth in partially masked faces. Behavioural results showed no differences in the ability to recognize emotions between presymptomatic gene carriers and controls. However, an emotion recognition deficit was found for all 6 basic emotion categories in early stage HD. Analysis of eye movement patterns showed that patient and controls used similar scanning strategies. Patterns of deficits were similar regardless of whether parts of the faces were masked or not, thereby confirming that selective attention to particular face parts is not underlying the deficits. These results suggest that the emotion recognition deficits in symptomatic HD patients cannot be explained by impaired scanning patterns of faces. Furthermore, no selective deficit for recognition of disgust was found in presymptomatic HD patients.

  8. Influence of Zr and nano-Y2O3 additions on thermal stability and improved hardness in mechanically alloyed Fe base ferritic alloys

    The motivation of this work was driven to improve the thermal stability in systems where polymorphic transformations can result in an additional driving force, upsetting the expected thermodynamic stability. In this study, Fe92Ni8 alloys with Zr and nano-Y2O3 additions were produced by ball milling and then annealed at high temperatures. Emphasis was placed on understanding the effects of dispersed nano-Y2O3 particle additions and their effect on microstructural stability at and above the bcc-to-fcc transformation occurring at 700 °C in Fe–Ni systems. Results reveal that microstructural stability and hardness can be promoted by a combination of Zr and Y2O3 additions, that being mostly effective for stability before and after phase transition, respectively. The mechanical strength of these alloys is achieved by a unique microstructure comprised a ultra-fine grain Fe base matrix, which contains dispersions of both nano-scale in-situ formed Zr base intermetallics and ex-situ added Y2O3 secondary oxide phases. Both of these were found to be essential for a combination of high thermal stability and high mechanical strength properties. - Highlights: • Polymorphic transformations can limit the processing of nanostructured powders. • It causes a rapid grain growth and impairs the improved mechanical properties. • We aim to improve the hardness and thermal stability above the phase transformation. • Thermal stability is achieved by a combination of Zr and Y2O3 additions. • Hardness is promoted by in-situ formed and ex-situ added secondary nano phases

  9. Microstructure and mechanical properties of the Al-Ti alloy with cerium addition

    L.A. Dobrzański

    2009-12-01

    Full Text Available Purpose: In this work there are presented the investigation results of mechanical properties and microstructure concerning mainly intermetallic phases of the aluminium – titanium alloy with a defined content of 2 and 4 % of cerium addition. The purpose of this work was also to determine the heat treatment conditions for solution heat treatment of the investigation alloys.Design/methodology/approach: The reason of this work was to determine the heat treatment influence, particularly solution heat treatment time to the changes of the microstructure, as well to determine which intermetallic phases occur after the heat treatment performed, and how is the morphology of these particles.Findings: After solution heat treatment for 4 hours the structure changes. The grains are larger and no more uniform as showed before. The most stable intermetallic in the Al-Ti system is the Al3Ti phase. The solution heat treatment time should be greater than 4 hours to ensure a proper solution of titanium and cerium in the Al-α solid solution.Research limitations/implications: The investigated aluminium samples were examined metallographically using optical microscope with different image techniques, scanning electron microscope and also analyzed using a Vickers micro-hardness tester, also EDS microanalysis was made.Practical implications: As an implication for the practice a new alloy can be developed, some other investigation should be performed in the future, but the knowledge found in this research shows an interesting investigation direction.Originality/value: The combination of light weight and high strength Ti-based alloys is very attractive for aerospace and automotive industries. Furthermore, the presence of calcium cerium into existence new unknown phases as well can enhance the thermal stability of ternary Al-Ti-Ce alloy because of its higher melting point then Al-Ti.

  10. Effect of mechanical alloying and Ti addition on solution and ageing treatment of an AA7050 aluminium alloy

    Kátia Regina Cardoso; Dilermando Nagle Travessa; Asunción García Escorial; Marcela Lieblich

    2007-01-01

    In this work, solution heat treatments at different temperatures were performed in a commercial based AA7050 aluminium alloy, with and without titanium addition, produced by mechanical alloying and hot extrusion with the aim to investigate the effect of titanium addition and mechanical alloying in the precipitates stability. The same heat treatment conditions were used in a reference sample obtained from a commercial AA7050 alloy. Solution heat treated samples were characterised by differenti...

  11. Aging impairs the recovery in mechanical muscle function following 4 days of disuse

    Hvid, Lars Grøndahl; Suetta, C; Nielsen, Jacob; Jensen, Majbrit M; Frandsen, U; Ørtenblad, N; Kjaer, M; Aagaard, P

    2014-01-01

    decrements observed in moderate dynamic strength and rapid muscle force capacity in old individuals. While 7 days of recovery - including free ambulation, one test session and a single session of strength training - was sufficient to restore mechanical muscle function in young individuals, old individuals...... the effect of 4 days of lower limb disuse followed by 7 days of active recovery on mechanical muscle function of the knee extensors in young (24.3±0.9 years, n=11) and old (67.2±1.0 years, n=11) recreationally active healthy males. Slow and moderate dynamic muscle strength were assessed using...... isokinetic dynamometry (60 and 180° s(-1), respectively) along with isometric muscle strength and rapid muscle force capacity examined as contractile rate of force development (RFD), Impulse, and relative RFD (rRFD) during the initial phase of contraction (100 ms time interval relative to onset of...

  12. The Possible Mechanisms of the Impaired Insulin Secretion in Hypothyroid Rats

    Aliashraf Godini; Asghar Ghasemi; Saleh Zahediasl

    2015-01-01

    Although the insulin secretion deficit in hypothyroid male rats has been documented, the underling mechanisms of the effect of hypothyroidism on insulin secretion are not clear. Isolated islets of the PTU-induced hypothyroid and control rats were exposed to glibenclamide, acetylcholine, and nifedipine in the presence of glucose concentrations of 2.8 or 8.3 and 16.7 mmol/L. Glucokinase and hexokinase specific activity, glucokinase content, and glucose transporter 2 protein expression were also...

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

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

    2012-01-01

    The prevalence of cardiovascular disease (CVD) increases with advancing age. While the long-term exposure to cardiovascular risk factors plays a major role in the etiopathogenesis of CVD, intrinsic cardiac aging enhances the susceptibility to developing heart pathologies in late life. The progressive decline of cardiomyocyte mitochondrial function is considered to be a major mechanism underlying heart senescence. Damaged mitochondria not only produce less ATP, but also generate increased amou...

  14. Impairment of pre-mRNA splicing in liver disease: Mechanisms and consequences

    Carmen; Berasain; Saioa; Gońi; Josefa; Castillo; Maria; Ujue; Latasa; Jesús; Prieto; Matias; A; Avila

    2010-01-01

    Pre-mRNA splicing is an essential step in the process of gene expression in eukaryotes and consists of the removal ofintrons and the linking of exons to generate mature mRNAs. This is a highly regulated mechanism that allows the alternative usage of exons, the retention ofintronic sequences and the generation of exonic sequences of variable length. Most human genes undergo splicing events, and disruptions of this process have been associated with a variety of diseases, including cancer. Hepatocellular carci...

  15. Early Impairment of Lung Mechanics in a Murine Model of Marfan Syndrome

    Uriarte, Juan J.; Meirelles, Thayna; Gorbenko del Blanco, Darya; Nonaka, Paula N.; Campillo, Noelia; Sarri, Elisabet; Navajas, Daniel; Egea, Gustavo; Farré, Ramon

    2016-01-01

    Early morbidity and mortality in patients with Marfan syndrome (MFS) -a connective tissue disease caused by mutations in fibrillin-1 gene- are mainly caused by aorta aneurysm and rupture. However, the increase in the life expectancy of MFS patients recently achieved by reparatory surgery promotes clinical manifestations in other organs. Although some studies have reported respiratory alterations in MFS, our knowledge of how this connective tissue disease modifies lung mechanics is scarce. Hence, we assessed whether the stiffness of the whole lung and of its extracellular matrix (ECM) is affected in a well-characterized MFS mouse model (FBN1C1039G/+). The stiffness of the whole lung and of its ECM were measured by conventional mechanical ventilation and atomic force microscopy, respectively. We studied 5-week and 9-month old mice, whose ages are representative of early and late stages of the disease. At both ages, the lungs of MFS mice were significantly more compliant than in wild type (WT) mice. By contrast, no significant differences were found in local lung ECM stiffness. Moreover, histopathological lung evaluation showed a clear emphysematous-like pattern in MFS mice since alveolar space enlargement was significantly increased compared with WT mice. These data suggest that the mechanism explaining the increased lung compliance in MFS is not a direct consequence of reduced ECM stiffness, but an emphysema-like alteration in the 3D structural organization of the lung. Since lung alterations in MFS are almost fully manifested at an early age, it is suggested that respiratory monitoring could provide early biomarkers for diagnosis and/or follow-up of patients with the Marfan syndrome. PMID:27003297

  16. Tobacco extract but not nicotine impairs the mechanical strength of fracture healing in rats.

    Skott, Martin; Andreassen, Troels T; Ulrich-Vinther, Michael; Chen, X; Keyler, Dan E; LeSage, Mark G; Pentel, Paul R; Bechtold, Joan E; Soballe, Kjeld

    2006-07-01

    The influence of nicotine and tobacco extract (without nicotine) alone and in combination on and mechanical strength of closed femoral fractures in rats was investigated. One hundred four male Sprague-Dawley rats were divided into four groups receiving: nicotine, tobacco extract, tobacco extract plus nicotine, and saline. One week prior to fracture, osmotic pumps were implanted subcutaneously in all animals to administer nicotine equivalent to the serum level of nicotine observed in a smoker consuming one to two packs of cigarettes daily. An equivalent volume of saline was administered to the control animals. Tobacco extract was administered orally. A closed transverse femoral diaphysial fracture was performed, and stabilized with an intramedullary pin. The fractures were mechanically tested after 21 days of healing. Tobacco extract alone decreased the mechanical strength. Ultimate torque and torque at yield point of the tobacco extract group were decreased by 21% (p=0.010) and 23% (p=0.056), respectively, compared with the vehicle (saline) group, and by 20% (p=0.023) and 26% (p=0.004), respectively, compared with the nicotine group. No difference was found between the tobacco extract and tobacco extract plus nicotine groups. An 18% (p=0.013) reduction in torque at yield point was observed in the tobacco extract plus nicotine group compared with the nicotine group. No differences in ultimate stiffness, energy absorption, and callus bone mineral content at the fracture line were found between any of the groups. Serum levels of nicotine were between 40-50 ng/mL in the group given nicotine alone and the group given tobacco extract plus nicotine (equivalent to serum levels observed in persons smoking one to two packs of cigarettes per day). PMID:16705735

  17. Microstructure and Mechanical Properties of WE43 Alloy Produced Via Additive Friction Stir Technology

    Calvert, Jacob Rollie

    2015-01-01

    In an effort to save weight, transportation and aerospace industries have increasing investigated magnesium alloys because of their high strength-to-weight ratio. Further efforts to save on material use and machining time have focused on the use of additive manufacturing. However, anisotropic properties can be caused by both the HCP structure of magnesium alloys as well as by layered effects left by typical additive manufacturing processes. Additive Friction Stir (AFS) is a relatively new add...

  18. Effect of La addition on glass-forming ability and stability of mechanically alloyed Zr-Ni amorphous alloys

    Research highlights: → The minor large atom La addition can improve the glass forming ability of Zr-Ni-La and enhance the stability of the amorphous phase against the mechanically induced crystallization. → The stability of the Zr-Ni-La amorphous phase decreases with increasing La content. → The effect of La addition in contrast with the small atomic size C addition plays a significant role in promoting the stability of the amorphous phase. → We try to systematically discuss the reasons of La addition effect on GFA and stability of the amorphous phase from three factor of negative heat of mixing, distance between neighboring atoms and atomic size mismatch, respectively. - Abstract: In this study, the role of La in the microstructural evolution of Zr66.7-xNi33.3Lax (x = 1, 3, 5 at.%) alloys during mechanical alloying has been investigated using X-ray diffraction (XRD), transmission electron microscopy (TEM) and differential scanning calorimetry (DSC). The results show that the single amorphous phase of Zr-Ni-La can be obtained through mechanical alloying. The minor La addition can improve the glass forming ability of Zr-Ni-La, enhance the mechanical stability of the amorphous phase against the mechanically induced crystallization and lead to an altered crystallization mode of Zr-Ni alloy. Moreover, the stability of the Zr-Ni-La amorphous phase decreases with further increasing La content. The best effect is obtained for the Zr65.7Ni33.3La1 alloy. Additionally, the effect of La addition in contrast with the small atomic size C addition plays a more significant role in promoting the stability of the amorphous phase. In addition, the reasons of La addition effect on GFA and stability have also been discussed from three factors of negative heat of mixing, distance between neighboring atoms and atomic size mismatch, respectively.

  19. Transient cerebral hypoperfusion and hypertensive events during atrial fibrillation: a plausible mechanism for cognitive impairment

    Anselmino, Matteo; Saglietto, Andrea; Gaita, Fiorenzo; Ridolfi, Luca

    2016-01-01

    Atrial fibrillation (AF) is associated with an increased risk of dementia and cognitive decline, independent of strokes. Several mechanisms have been proposed to explain this association, but altered cerebral blood flow dynamics during AF has been poorly investigated: in particular, it is unknown how AF influences hemodynamic parameters of the distal cerebral circulation, at the arteriolar and capillary level. Two coupled lumped-parameter models (systemic and cerebrovascular circulations, respectively) were here used to simulate sinus rhythm (SR) and AF. For each simulation 5000 cardiac cycles were analyzed and cerebral hemodynamic parameters were calculated. With respect to SR, AF triggered a higher variability of the cerebral hemodynamic variables which increases proceeding towards the distal circulation, reaching the maximum extent at the arteriolar and capillary levels. This variability led to critical cerebral hemodynamic events of excessive pressure or reduced blood flow: 303 hypoperfusions occurred at ...

  20. Lack of neural compensatory mechanisms of BDNF val66met met carriers and APOE E4 carriers in healthy aging, mild cognitive impairment, and Alzheimer's disease.

    Gomar, Jesus J; Conejero-Goldberg, Concepcion; Huey, Edward D; Davies, Peter; Goldberg, Terry E

    2016-03-01

    Compromises in compensatory neurobiologic mechanisms due to aging and/or genetic factors (i.e., APOE gene) may influence brain-derived neurotrophic factor (BDNF) val66met polymorphism effects on temporal lobe morphometry and memory performance. We studied 2 cohorts from Alzheimer's Disease Neuroimaging Initiative: 175 healthy subjects and 222 with prodromal and established Alzheimer's disease. Yearly structural magnetic resonance imaging and cognitive performance assessments were carried out over 3 years of follow-up. Both cohorts had similar BDNF Val/Val and Met allele carriers' (including both Val/Met and Met/Met individuals) distribution. In healthy subjects, a significant trend for thinner posterior cingulate and precuneus cortices was detected in Met carriers compared to Val homozygotes in APOE E4 carriers, with large and medium effect sizes, respectively. The mild cognitive impairment/Alzheimer's disease cohort showed a longitudinal decline in entorhinal thickness in BDNF Met carriers compared to Val/Val in APOE E4 carriers, with effect sizes ranging from medium to large. In addition, an effect of BDNF genotype was found in APOE E4 carriers for episodic memory (logical memory and ADAS-Cog) and semantic fluency measures, with Met carriers performing worse in all cases. These findings suggest a lack of compensatory mechanisms in BDNF Met carriers and APOE E4 carriers in healthy and pathological aging. PMID:26923413

  1. Moisture permeability mechanisms of some aqueous-based tablet film coatings containing soluble additives.

    Okhamafe, A O; Iwebor, H U

    1987-09-01

    Moisture permeation parameters--diffusion, solubility and permeation coefficients--for hydroxypropyl methylcellulose (HPMC) and partially hydrolyzed polyvinyl alcohol (PVA) films containing either of two water-soluble additives (citric acid and urea) have been evaluated from transmission and time lag data. Contrary to expectations, the moisture diffusivities of the films were markedly lowered by the presence of these additives. However, the solubility coefficients increased while the permeability coefficients were largely unchanged up to 10 wt% of the additives. A complex phenomenon involving an extensive interlacing network of mainly hydrogen bond interactions between additive and films former was believed to influence the permeation properties of the films. The estimated limits of compatibility of the additives with the film-former were in the range of 5-10 wt%. PMID:3432347

  2. Home blood sodium monitoring, sliding-scale fluid prescription and subcutaneous DDAVP for infantile diabetes insipidus with impaired thirst mechanism

    Hameed Shihab

    2012-06-01

    Full Text Available Abstract Background/Aims Infants with diabetes insipidus (DI, especially those with impaired thirst mechanism or hypothalamic hyperphagia, are prone to severe sodium fluctuations, often requiring hospitalization. We aimed to avoid dangerous fluctuations in serum sodium and improve parental independence. Methods A 16-month old girl with central DI, absent thirst mechanism and hyperphagia following surgery for hypothalamic astrocytoma had erratic absorption of oral DDAVP during chemotherapy cycles. She required prolonged hospitalizations for hypernatremia and hyponatremic seizure. Intensive monitoring of fluid balance, weight and clinical assessment of hydration were not helpful in predicting serum sodium. Discharge home was deemed unsafe. Oral DDAVP was switched to subcutaneous (twice-daily injections, starting with 0.01mcg/dose, increasing to 0.024mcg/dose. The parents adjusted daily fluid allocation by sliding-scale, according to the blood sodium level (measured by handheld i-STAT analyser, Abbott. We adjusted the DDAVP dose if fluid allocation differed from maintenance requirements for 3 consecutive days. Results After 2.5 months, sodium was better controlled, with 84% of levels within reference range (135-145 mmol/L vs. only 51% on the old regimen (p = 0.0001. The sodium ranged from 132-154 mmol/L, compared to 120–156 on the old regimen. She was discharged home. Conclusion This practical regimen improved sodium control, parental independence, and allowed discharge home.

  3. Effect of Flyash Addition on Mechanical and Gamma Radiation Shielding Properties of Concrete

    Kanwaldeep Singh

    2014-01-01

    Full Text Available Six concrete mixtures were prepared with 0%, 20%, 30%, 40%, 50%, and 60% of flyash replacing the cement content and having constant water to cement ratio. The testing specimens were casted and their mechanical parameters were tested experimentally in accordance with the Indian standards. Results of mechanical parameters show their improvement with age of the specimens and results of radiation parameters show no significant effect of flyash substitution on mass attenuation coefficient.

  4. Mechanical properties of 3D auxetic structures produced by additive manufacturing

    Jiroušek, O.; Koudelka_ml., Petr; Fíla, Tomáš

    Prague: Institute of theoretical and applied mechanics, Academy of Sciences of the Czech Republic, v. v. i., 2015 - (Náprstek, J.; Fischer, C.), s. 124-125 ISBN 978-80-86246-42-0. ISSN 1805-8248. [Engineering mechanics 2015 /21./. Svratka (CZ), 11.05.2015-14.05.2015] Institutional support: RVO:68378297 Keywords : auxetic structure * direct 3D printing * finite element method * digital image correlation Subject RIV: JJ - Other Materials

  5. Effect of Clay Addition on Mechanical Properties of Unsaturated Polyester/Glass Fiber Composites

    Kusmono; Zainal Arifin Mohd Ishak

    2013-01-01

    Unsaturated polyester (UP)/glass fiber/clay composites were prepared by hand layup method. The effect of clay loading on the morphological and mechanical properties of UP/glass fiber composites was investigated in this study. X-ray diffraction (XRD) was used to characterize the structure of the composites. The mechanical properties of the composites were determined by tensile, flexural, unnotched Charpy impact and fracture toughness tests. XRD results indicated that the exfoliated structure w...

  6. Herbal Medicine Goshajinkigan Prevents Paclitaxel-Induced Mechanical Allodynia without Impairing Antitumor Activity of Paclitaxel

    Muh. Akbar Bahar

    2013-01-01

    Full Text Available Chemotherapy-induced peripheral neuropathy is a major dose-limiting side effect of commonly used chemotherapeutic agents. However, there are no effective strategies to treat the neuropathy. We examined whether Goshajinkigan, a herbal medicine, would prevent paclitaxel-induced allodynia without affecting the anticancer action in mice. Murine breast cancer 4T1 cells were inoculated into the mammary fat pad. Paclitaxel (10 and 20 mg/kg, intraperitoneal, alternate day from day 7 postinoculation inhibited the tumor growth, and Goshajinkigan (1 g/kg, oral, daily from day 2 postinoculation did not affect the antitumor action of paclitaxel. Mechanical allodynia developed in the inoculated region due to tumor growth and in the hind paw due to paclitaxel-induced neuropathy. Paclitaxel-induced allodynia was markedly prevented by Goshajinkigan, although tumor-associated allodynia was not inhibited by Goshajinkigan. These results suggest that Goshajinkigan prevents paclitaxel-induced peripheral neuropathy without interfering with the anti-cancer action of paclitaxel.

  7. Morin reverses neuropathological and cognitive impairments in APPswe/PS1dE9 mice by targeting multiple pathogenic mechanisms.

    Du, Ying; Qu, Jie; Zhang, Wei; Bai, Miao; Zhou, Qiong; Zhang, Zhuo; Li, Zhuyi; Miao, Jianting

    2016-09-01

    Alzheimer's disease (AD) is the most common form of dementia worldwide, characterized by progressive cognitive impairment and multiple distinct neuropathological features. Currently, there are no available therapies to delay or block the disease progression. Thus, the disease-modifying therapies are urgent for this devastating disorder by simultaneously targeting multiple distinct pathological processes. Morin, a natural bioflavonoid, have been shown to be strongly neuroprotective in vitro and in vivo. In this study, we first investigated the disease-modifying effects of chronic morin administration on the neuropathological and cognitive impairments in APPswe/PS1dE9 double transgenic mice. Our results showed that chronic morin administration prevented spatial learning and memory deficits in the APPswe/PS1dE9 mice. Morin treatment in the APPswe/PS1dE9 mice markedly reduced cerebral Aβ production and Aβ plaque burden via promoting non-amyloidogenic APP processing pathway by increasing ADAM10 expression, inhibiting amyloidogenic APP processing pathway by decreased BACE1 and PS1 expression, and facilitating Aβ degradation by enhancing Aβ-degrading enzyme expression. In addition, we also found that morin treatment in the APPswe/PS1dE9 mice markedly decreased tau hyperphosphorylation via its inhibitory effect on CDK5 signal pathway. Furthermore, morin treatment in the APPswe/PS1dE9 mice markedly reduced the activated glial cells and increased the expression of synaptic markers. Collectively, our findings demonstrate that chronic morin treatment restores cognitive functions and reverses multiple distinct neuropathological AD-like hallmarks in the APPswe/PS1dE9 mice. This study provides novel insights into the neuroprotective actions and neurobiological mechanisms of morin against AD, suggesting that morin is a potently promising disease-modifying agent for treatment of AD. PMID:27067919

  8. Stressors impair odor recognition memory via an olfactory bulb-dependent noradrenergic mechanism

    Laura C Manella

    2013-12-01

    Full Text Available Non-associative habituation and odor recognition tasks have been widely used to probe questions social recognition, odor memory duration, and odor memory specificity. Among others, these paradigms have provided valuable insight into how neuromodulation, and specifically norepinephrine/noradrenaline (NE influences odor memory. In general, NE levels are modulated by arousal, stress, and behavioral state, and there is sparse evidence of a direct relationship between NE and odor memory in adult rodents. The present study uses simple mild psychological stressors (bright light and sound, to modulate NE levels physiologically in order to probe its effect on olfactory memory. In rats with bilateral bulbar cannulations, we show that these stressors modulate olfactory memory and that this effect is at least partially mediated by olfactory bulb. Specifically, we show that the presence of stressors during the acquisition of odor memory suppresses memory for an odor when tested 30 minutes after the acquisition. This suppression is blocked by infusing NE antagonists into the olfactory bulb prior to odor acquisition. Additionally, we find that infusion of bulbar NE is sufficient to suppress odor memory in a manner mimicking that of our stressors. These effects are unlikely to be solely mediated by locomotor/exploratory changes produced by stressors, although these stressors influence certain behaviors not directly related to odor investigation. This study provides important information about how behaviorally relevant changes in NE can influence top-down sensory processing and odor memory.

  9. Influence of niobium addition on microstructure, mechanical properties and oxidation resistance of ZrN coatings

    In this study, Zr-Nb-N coatings with 0–3.8 at.% Nb addition were deposited by magnetron co-sputtering deposition. The results reveal that Nb atoms substitute Zr atoms in Zr-N lattice, forming the solid solution structure. All the Zr-Nb-N coatings illustrate a dense columnar structure with the preferred orientation of (200), showing independent of Nb addition. Nanoindentation result reveals a promoted hardness of the Zr-Nb-N coatings from 23.9 ± 0.7 GPa to 28.4 ± 0.5 GPa with enhanced Nb content from 0 to 2.8 at.% due to both the solid solution strengthening and Hall–Petch effect. Scratch tests show that adhesion between substrates and coatings can be improved by Nb addition. After oxidation in air at 600 °C for 2 h, microstructural studies indicate the oxide scales consist of monoclinic-ZrO2 outer layer and tetragonal-ZrO2 inner layer. Moreover, ZrO2 can be stabilized in the tetragonal phase by Nb doping. The Zr-Nb-N coating with 1.3 at.% Nb addition exhibits superior oxidation resistance, while excess Nb addition produces detrimental effects on oxidation resistance. - Highlights: • Moderate Nb addition improves the hardness and adhesion of Zr-Nb-N coatings. • Significant improvement of oxidation resistance is obtained by Nb addition. • GAXRD and TEM microstructural studies of the Zr-Nb-N coatings. • Phase stabilization of tetragonal-ZrO2 is achieved by Nb addition

  10. Influence of niobium addition on microstructure, mechanical properties and oxidation resistance of ZrN coatings

    Wu, Z.T. [College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005 (China); Qi, Z.B. [School of Materials Science and Engineering, Xiamen University of Technology, Xiamen 361005 (China); Jiang, W.F. [College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005 (China); Wang, Z.C., E-mail: zcwang@xmu.edu.cn [College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005 (China); Liu, B. [Xiamen Annaiwy New Material CO., LTD, Xiamen 361005 (China)

    2014-11-03

    In this study, Zr-Nb-N coatings with 0–3.8 at.% Nb addition were deposited by magnetron co-sputtering deposition. The results reveal that Nb atoms substitute Zr atoms in Zr-N lattice, forming the solid solution structure. All the Zr-Nb-N coatings illustrate a dense columnar structure with the preferred orientation of (200), showing independent of Nb addition. Nanoindentation result reveals a promoted hardness of the Zr-Nb-N coatings from 23.9 ± 0.7 GPa to 28.4 ± 0.5 GPa with enhanced Nb content from 0 to 2.8 at.% due to both the solid solution strengthening and Hall–Petch effect. Scratch tests show that adhesion between substrates and coatings can be improved by Nb addition. After oxidation in air at 600 °C for 2 h, microstructural studies indicate the oxide scales consist of monoclinic-ZrO{sub 2} outer layer and tetragonal-ZrO{sub 2} inner layer. Moreover, ZrO{sub 2} can be stabilized in the tetragonal phase by Nb doping. The Zr-Nb-N coating with 1.3 at.% Nb addition exhibits superior oxidation resistance, while excess Nb addition produces detrimental effects on oxidation resistance. - Highlights: • Moderate Nb addition improves the hardness and adhesion of Zr-Nb-N coatings. • Significant improvement of oxidation resistance is obtained by Nb addition. • GAXRD and TEM microstructural studies of the Zr-Nb-N coatings. • Phase stabilization of tetragonal-ZrO2 is achieved by Nb addition.

  11. Thermo-mechanical analysis of wire and arc additive manufacturing process

    Ding, J

    2012-01-01

    Conventional manufacturing processes often require a large amount of machining and cannot satisfy the continuously increasing requirements of a sustainable, low cost, and environmentally friendly modern industry. Thus, Additive Manufacturing (AM) has become an important industrial process for the manufacture of custom-made metal workpieces. Among the different AM processes, Wire and Arc Additive Manufacture (WAAM) has the ability to manufacture large, low volume metal work-p...

  12. Effect of Cu addition on microstructure and mechanical properties of 15%Cr super martensitic stainless steel

    Highlights: ► Cu contributes to refine the grains. ► Cu solutes in matrix under quenching and precipitates as ε-Cu during tempering. ► Cu promotes the kinetics of reversed austenite formation. ► Mechanical properties are significantly influenced by austenite amount. ► Cu alloyed super martensitic stainless steel exhibits greatly improved mechanical properties. -- Abstract: The effect of adding different content of Cu (0 wt.%, 1.5 wt.% and 3 wt.%) to the 15%Cr super martensitic stainless steel (SMSS) was investigated using optical microscope, scanning electron microscope (SEM), transmission electron microscope (TEM) and X-ray diffraction (XRD). Its consequence on mechanical properties was examined to clarify the role of Cu in the tested steels. The experimental results indicate that the microstructures of three tested steels are tempered martensite, retained austenite and reversed austenite; two kinds of austenites are dispersedly distributed among martensite matrix. Cu can solute in matrix under quenching condition and can precipitate as Cu-rich nanometer phase (ε-Cu) during tempering. Cu is helpful for the grain refinement and to promote the formation of reversed austenite during tempering. The maximum volume fraction of austenite is 55.9% in the steel with 3 wt.% Cu, which is responsible for the improvement of ductility. The results of the mechanical properties tests reveal that the mechanical properties are significantly influenced by the volume fraction of austenite. Cu can cause solid solution strengthening, precipitation strengthening and grain refinement strengthening in SMSS. Cu alloyed super martensitic stainless steel exhibits greatly improved mechanical properties.

  13. Effect of Ce addition on the mechanical and electrochemical properties of a lithium battery shell alloy

    Zhang, Junchao [School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240 (China); Ding, Dongyan, E-mail: dyding@sjtu.edu.cn [School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240 (China); Xu, Xinglong [School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240 (China); Gao, Yongjin; Chen, Guozhen; Chen, Weigao; You, Xiaohua [Huafon NLM Al Co., Ltd, Shanghai 201506 (China); Huang, Yuanwei; Tang, Jinsong [Shanghai Huafon Materials Technology Institute, Shanghai 201203 (China)

    2014-12-25

    Highlights: • Fabrication of Ce-free and Ce-containing Al–Cu–Mn–Fe–Mg alloy. • TEM, tensile and electrochemical characterization of the alloys. • Ce element greatly affects the precipitation of the alloy. • Ce element had great impact on the tensile strength and corrosion potential of the alloys. - Abstract: Due to severe application environment lithium battery shell of new-energy automotives requires increasing demands for using high performance aluminum alloys. In the present work, effect of Ce addition on the microstructure, tensile and electrochemical properties of an Al–Cu–Mn–Mg–Fe alloy were investigated through using X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), tensile tests and electrochemical tests. The experimental results indicated that the addition of Ce element could promote the precipitation of second phases. With addition of 0.36% Ce, high melting point Al{sub 8}Cu{sub 4}Ce phase and many Al{sub 20}Cu{sub 2}Mn{sub 3} particles could be found. In addition, the precipitation of conventionally dominant phase of Al{sub 2}Cu could be suppressed in alloy. The Ce addition was found to result in enhanced tensile strength and improved corrosion resistance.

  14. Effect of Ce addition on the mechanical and electrochemical properties of a lithium battery shell alloy

    Highlights: • Fabrication of Ce-free and Ce-containing Al–Cu–Mn–Fe–Mg alloy. • TEM, tensile and electrochemical characterization of the alloys. • Ce element greatly affects the precipitation of the alloy. • Ce element had great impact on the tensile strength and corrosion potential of the alloys. - Abstract: Due to severe application environment lithium battery shell of new-energy automotives requires increasing demands for using high performance aluminum alloys. In the present work, effect of Ce addition on the microstructure, tensile and electrochemical properties of an Al–Cu–Mn–Mg–Fe alloy were investigated through using X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), tensile tests and electrochemical tests. The experimental results indicated that the addition of Ce element could promote the precipitation of second phases. With addition of 0.36% Ce, high melting point Al8Cu4Ce phase and many Al20Cu2Mn3 particles could be found. In addition, the precipitation of conventionally dominant phase of Al2Cu could be suppressed in alloy. The Ce addition was found to result in enhanced tensile strength and improved corrosion resistance

  15. Mechanism of unusual polymorph transformations in calcium carbonate: Dissolution-recrystallization vs additive-mediated nucleation

    Arpita Sarkar; Samiran Mahapatra

    2012-11-01

    Unusual transformation of one CaCO3 phase to another has been reported by the process of dissolution-recrystallization and under the influence of additive. In one case, while metastable vaterite transforms to another metastable phase aragonite by simple refluxing in distilled water, it instead transforms thermodynamically stable phase calcite upon refluxing in its `mother-liquor’. This is explained by the process of dissolution-recrystallization. In another case, aragonite is preferentially synthesized over calcite in the presence of molten lauric acid as an additive.

  16. Antiwear performance and mechanism of an oil-miscible ionic liquid as a lubricant additive.

    Qu, Jun; Bansal, Dinesh G; Yu, Bo; Howe, Jane Y; Luo, Huimin; Dai, Sheng; Li, Huaqing; Blau, Peter J; Bunting, Bruce G; Mordukhovich, Gregory; Smolenski, Donald J

    2012-02-01

    An ionic liquid (IL) trihexyltetradecylphosphonium bis(2-ethylhexyl) phosphate has been investigated as a potential antiwear lubricant additive. Unlike most other ILs that have very low solubility in nonpolar fluids, this IL is fully miscible with various hydrocarbon oils. In addition, it is thermally stable up to 347 °C, showed no corrosive attack to cast iron in an ambient environment, and has excellent wettability on solid surfaces (e.g., contact angle on cast iron lubricating oils. For example, a 5 wt % addition into a synthetic base oil eliminated the scuffing failure experienced in neat oil and, as a result, reduced the friction coefficient by 60% and the wear rate by 3 orders of magnitude. A synergistic effect on wear protection was observed with the current antiwear additive when added into a fully formulated engine oil. Nanostructure examination and composition analysis revealed a tribo-boundary film and subsurface plastic deformation zone for the metallic surface lubricated by the IL-containing lubricants. This protective boundary film is believed to be responsible for the IL's antiscuffing and antiwear functionality. PMID:22248297

  17. Effects of trace addition of vanadium and depression amount on recrystallization temperature and mechanical performance of 5182 belts

    GAO Jia-cheng; CHEN Zhi-qiang; MING Wen-liang; WANG Yong; CUI Xian-you; YUAN Li-jun

    2006-01-01

    Because the mechanical performances of 5182 belts used for carbonated drinks cover decrease after baking, the effects of trace addition of V and depression amount in last step on microstructure and properties of 5182 belts were investigated. The microstructure, mechanical performances and recrystallization temperature of 5182 belts and 5182V belts in different steps were analyzed comparatively with metallographic microscope, micro-hardness tester, electron universal materials test machine and differential thermal analyzer. The results show that the mechanical performances of the belts are remarkably improved by the trace addition of V and the reduction of depression amount in last step. In addition, the recrystallization temperature of the belts is also increased but not obviously. As the precipitation of V is not full, there are not enough disseminatedly distributed particles, and the recrystallization temperature increases little. However the solution strengthening and the fine grain strengthening are enough to improve the mechanical performances to satisfy customer requirements. The effects of reduction of depression amount in last step on mechanical performance were explained in view of energy. Moreover, the strengthening mechanism of V-compound interlocking grain boundary was also discussed.

  18. Effect of sulfonation and diethanolamine addition on the mechanical and physicochemical properties of SEPS copolymer

    Patiño, D.; Correa, E.; Acevedo-Morantes, M.

    2016-02-01

    Modification techniques have been developed to achieve changes in the processing of polymers, and modification of their mechanical, thermal and morphological properties, as well as their hydrophobicity and conductivity. Sulfonation improves ion conductivity, antistatic behaviour, hydrophilicity and solubility of the polymers. These characteristics are related to the presence of sulfonic groups in the polymer matrix. This research project focuses on the evaluation of mechanical, physical and chemical properties of membranes that are based on a sulfonated Styrene-Ethylene-Propylene-Styrene (SEPS) copolymer. The membranes were functionalized with diethanolamine at 5, 15 and 30% w/w, to separate carbon dioxide. FTIR and XRD analyses were used to characterize the membranes. The sulfonated-loaded membrane with 15% of diethanolamine showed the best results in each characterization.

  19. Research on toughening mechanisms of alumina matrix ceramic composite materials improved by rare earth additive

    ZHANG Xihua; LIU Changxia; LI Musen; ZHANG Jianhua

    2008-01-01

    Mixed rare earth elements were incorporated into alumina ceramic materials. Hot-pressing was used to fabricate alumina matrix composites in nitrogen atmosphere protection. Microstructures and mechanical properties of the composites were tested. It was indicated that the bending strength and fracture toughness of alumina matrix ceramic composites sintered at 1550℃ and 28 Mpa for 30 min were improved evidently. Besides mixed rare earth elements acting as a toughening phase, AlTiC master alloys were also added in as sintering assistants, which could prompt the formation of transient liquid phase, and thus nitrides of rare earth elements were produced. All of the above were beneficial for improving the mechanical properties of alumina matrix ceramic composites.

  20. Physico-mechanical and dissolution behaviours of ibuprofen crystals crystallized in the presence of various additives

    Nokhodchi, A.; Amire, O.; Jelvehgari, M.

    2010-01-01

    "n  "n Background and the purpose of the study: The success of any direct-tableting procedure is strongly affected by the quality of the crystals used in the process. Ibuprofen is a poorly compactible drug with a high tendency for capping. In order to use ibuprofen in direct compression formulations, physico-mechanical properties of ibuprofen should be improved considerably. The aim of the present investigation was to employ crystallization techniques in order to i...

  1. Energy model of projected transfer with additional mechanical force in the welding process

    2000-01-01

    Based on the theory of electrodynamics and other relational subjects,through introducing "Surface Evolver" as the means of FEM analysis, by computing and describing the energy (electromagnetic, gravity, and so on) in the droplet transfer system, an energy model was accomplished for studying the mechanism of projected transfer mode.Furthermore, the behavior of droplet transfer was studied by analyzing its menisci with FEM, and the theoretical results coincide well with the experiment results.

  2. EFFECT OF COPPER ADDITION ON MECHANICAL PROPERTIES OF 4Cr16Mo

    H.M. Geng; X.C. Wu; Y.A. Min; H.B. Wang; H.K. Zhang

    2008-01-01

    Experiments conducted to determine the effect of copper addition on the machinability of plastic mold steel, 4Cr16Mo, were presented. The machinability of mold steel 4Cr16Mo was visibly improved by adding Cu. The top wear of 4Cr16Mo with copper was less than that without copper. The Cu-rich phase had the effect of a lubricant and the heat conductivity, which reduced cutting-tool wear, improved machinability, and increased the service life of the cutting-tool. Increasing of copper addition decreased the hot-working character of 4Cr16Mo. The optimal hot-working parameters for 4Cr16Mo with copper were determined by the tensile test and the compression test. The rate of deformation should be adopted as 0.6 s-1. The heating-up temperature, initial forging temperature, and terminal forging temperature were 1200℃, 1150℃, and 950℃, respectively.

  3. PVC mixtures’ mechanical properties with the addition of modified calcite as filler

    Vučinić Dušica R.

    2012-01-01

    Full Text Available In this study mechanical properties of PVC mixtures (PVC, stabilizer, lubricant, filler such as tensile strength, tensile elongation, breaking strength, and breaking elongation were investigated. Unmodified calcite, as well as calcite modified by stearic acid, were used as fillers in wet and dry processes. The PVC mixtures containing the calcite modified by wet procedure have better mechanical properties compared to those with the calcite modified by the dry process. Tensile and breaking strength of the PVC mixture containing the calcite modified with 1.5% stearic acid using wet process, are higher for 2.8% and 5.2%, respectively, compared to the PVC mixture containing the calcite modified with the same amount of acid used in the dry process. The tensile strength difference between the mixtures increases with the increase of the concentration of used stearic acid up to 3%. The strength of PVC mixture with the calcite modified by wet process is 3.1% higher compared to the mixture containing calcite modified by dry process. The results showed that the bonding strength between calcite and the adsorbed organic component affected tensile strength, tensile elongation and breaking strength of the PVC mixtures. The best filler was obtained by wet modification using 1.5% stearic acid solution that provided the formation of a stearate monolayer chemisorbed on calcite. The PVC mixtures containing the calcite modified by wet process using 1.5% stearic acid solution exhibited the best mechanical properties. This calcite was completely hydrophobic with dominant chemically adsorbed surfactant, which means that stearate chemisorbed on calcite provided stronger interaction in the calcite-stearic acid-PVC system.

  4. Lipid Oxidation in Mechanically Deboned Chicken Meat: Effect of the Addition of Different Agents

    Alexandre da Trindade Alfaro; Cleusa Inês Weber; Juliana Bigolin

    2013-01-01

    The study evaluated the effect of sodium chloride (1.5%), sodium erythorbate (0.5% and 1.0%) and ascorbic acid (0.1% and 0.2%) on inhibiting lipid oxidation in mechanically deboned chicken meat (MDCM). The peroxide, acidity, pH, color and odor values of the samples were determined on the 1st, 3rd and 5th days. Treatments with sodium erythorbate and ascorbic acid had significant influence (p ≤ 0.05) on the peroxide, acidity and pH values. Ascorbic acid and erythorbate sodium were especially ef...

  5. Influence of nickel addition on magnetic and electro-mechanical behaviour of permalloys

    Kiran Gupta; K K Raina; S K Sinha

    2006-08-01

    Magnetic and electro-mechanical investigations have been carried out in two Ni–Fe permalloys under hydrogen atmosphere by varying annealing temperature. These alloys have been characterized for various magnetic parameters like peak permeability, coercivity and core loss under changed annealing profile conditions. The magnetic properties of Ni-rich (Ni ∼ 82%) alloy at 100 Hz were found to be better than the low Ni (Ni ∼ 47%) alloy. The alloys were tested for watch movement and found that the battery life of the watch movement improved by 38% using Ni-rich permalloy.

  6. Altered intestinal microbial flora and impaired epithelial barrier structure and function in CKD: the nature, mechanisms, consequences and potential treatment.

    Vaziri, Nosratola D; Zhao, Ying-Yong; Pahl, Madeleine V

    2016-05-01

    Chronic kidney disease (CKD) results in systemic inflammation and oxidative stress which play a central role in CKD progression and its adverse consequences. Although many of the causes and consequences of oxidative stress and inflammation in CKD have been extensively explored, little attention had been paid to the intestine and its microbial flora as a potential source of these problems. Our recent studies have revealed significant disruption of the colonic, ileal, jejunal and gastric epithelial tight junction in different models of CKD in rats. Moreover, the disruption of the epithelial barrier structure and function found in uremic animals was replicated in cultured human colonocytes exposed to uremic human plasma in vitro We have further found significant changes in the composition and function of colonic bacterial flora in humans and animals with advanced CKD. Together, uremia-induced impairment of the intestinal epithelial barrier structure and function and changes in composition of the gut microbiome contribute to the systemic inflammation and uremic toxicity by accommodating the translocation of endotoxin, microbial fragments and other noxious luminal products in the circulation. In addition, colonic bacteria are the main source of several well-known pro-inflammatory uremic toxins such as indoxyl sulfate, p-cresol sulfate, trimethylamine-N-oxide and many as-yet unidentified retained compounds in end-stage renal disease patients. This review is intended to provide an overview of the effects of CKD on the gut microbiome and intestinal epithelial barrier structure and their role in the pathogenesis of systemic inflammation and uremic toxicity. In addition, potential interventions aimed at mitigating these abnormalities are briefly discussed. PMID:25883197

  7. Influence of additives on microstructures, mechanical properties and shock-induced reaction characteristics of Al/Ni composites

    Granular composites containing aluminum (Al) and nickel (Ni) are typical structural energetic materials, which possess ideal combination of both mechanical properties and energy release capability. The influence of two additives, namely Teflon (PTFE) and copper (Cu), on mechanical properties and shock-induced chemical reaction (SICR) characteristics of Al/Ni material system has been investigated. Three composites, namely Al/Ni, Al/Ni/PTFE and Al/Ni/Cu with same volumetric ratio of Al powder to Ni powder, were processed by means of static pressing. Scanning electron microscopy was used to study the microstructure of the mentioned three composites. Quasi static compression tests were also conducted to determine the mechanical properties and fracture behavior of the mentioned three composites. It was shown that the additives affected both compressive strength and fracture mode of the three composites. Impact initiation experiments on the mentioned three composites were performed to determine their shock-induced chemical reaction characteristics by considering pressure histories measured in the test chamber. The experimental results showed that the additives had significant effects on critical initiation velocity, reaction rate, reaction efficiency and post-reaction behavior. - Highlights: • .Al/Ni, Al/Ni/PTFE and Al/Ni/Cu were processed by means of static pressing. • .Microstructures, mechanical properties and shock-induced reactions were studied. • .Microstructures affect both compressive strength and fracture mode. • .Impact velocity is an important factor in shock-induced chemical characteristics. • .Each additive has significant effects on energy release behavior

  8. Influence of silver additions to type 316 stainless steels on bacterial inhibition, mechanical properties, and corrosion resistance

    Chiang, Wen-Chi; Tseng, I-Sheng; Møller, Per;

    2010-01-01

    techniques. The microstructure of these 316 stainless steels was examined, and the influences of silver additions to 316 stainless steels on bacterial inhibition, mechanical properties, and corrosion resistance were investigated. This study suggested that silver-bearing 316 stainless steels could be used in...

  9. Influence of additives on microstructures, mechanical properties and shock-induced reaction characteristics of Al/Ni composites

    Xiong, Wei; Zhang, Xianfeng, E-mail: lynx@mail.njust.edu.cn; Wu, Yang; He, Yong; Wang, Chuanting; Guo, Lei

    2015-11-05

    Granular composites containing aluminum (Al) and nickel (Ni) are typical structural energetic materials, which possess ideal combination of both mechanical properties and energy release capability. The influence of two additives, namely Teflon (PTFE) and copper (Cu), on mechanical properties and shock-induced chemical reaction (SICR) characteristics of Al/Ni material system has been investigated. Three composites, namely Al/Ni, Al/Ni/PTFE and Al/Ni/Cu with same volumetric ratio of Al powder to Ni powder, were processed by means of static pressing. Scanning electron microscopy was used to study the microstructure of the mentioned three composites. Quasi static compression tests were also conducted to determine the mechanical properties and fracture behavior of the mentioned three composites. It was shown that the additives affected both compressive strength and fracture mode of the three composites. Impact initiation experiments on the mentioned three composites were performed to determine their shock-induced chemical reaction characteristics by considering pressure histories measured in the test chamber. The experimental results showed that the additives had significant effects on critical initiation velocity, reaction rate, reaction efficiency and post-reaction behavior. - Highlights: • .Al/Ni, Al/Ni/PTFE and Al/Ni/Cu were processed by means of static pressing. • .Microstructures, mechanical properties and shock-induced reactions were studied. • .Microstructures affect both compressive strength and fracture mode. • .Impact velocity is an important factor in shock-induced chemical characteristics. • .Each additive has significant effects on energy release behavior.

  10. Effect of Clay Addition on Mechanical Properties of Unsaturated Polyester/Glass Fiber Composites

    Kusmono

    2013-01-01

    Full Text Available Unsaturated polyester (UP/glass fiber/clay composites were prepared by hand layup method. The effect of clay loading on the morphological and mechanical properties of UP/glass fiber composites was investigated in this study. X-ray diffraction (XRD was used to characterize the structure of the composites. The mechanical properties of the composites were determined by tensile, flexural, unnotched Charpy impact and fracture toughness tests. XRD results indicated that the exfoliated structure was found in the composite containing 2 wt% of clay while the intercalated structure was obtained in the composite with 6 wt% of clay. The tensile strength, flexural strength, and flexural modulus of the composites were increased in the presence of clay. The optimum loading of clay in the UP/glass fiber composites was attained at 2 wt%, where the improvement in in tensile strength, flexural strength, and flexural modulus was approximately 13, 21, and 11%, respectively. On the other hand, the highest values in impact toughness and fracture toughness were observed in the composites with 4 wt% of clay.

  11. Mechanism of hydrofluoric acid formation in ethylene carbonate electrolytes with fluorine salt additives

    Tebbe, Jonathon L.; Fuerst, Thomas F.; Musgrave, Charles B.

    2015-11-01

    We utilized density functional theory to examine HF generation in lithium-ion battery electrolytes from reactions between H2O and the decomposition products of three electrolyte additives: LiPF6, LiPOF4, and LiAsF6. Decomposition of these additives produces PF5, AsF5, and POF3 along with LiF precipitates. We found PF5 and AsF5 react with H2O in two sequential steps to form two HF molecules and POF3 and AsOF3, respectively. PF5 (or AsF5) complexes with H2O and undergoes ligand exchange to form HF and PF4OH (AsF4OH) with an activation barrier of 114.2 (30.5) kJ mol-1 and reaction enthalpy of 14.6 (-11.3) kJ mol-1. The ethylene carbonate (EC) electrolyte forms a Lewis acid-base complex with the PF4OH (AsF4OH) product, reducing the barrier to HF formation. Reactions of POF3 were examined and are not characterized by complexation of POF3 with H2O or EC, while PF5 and AsF5 complex favorably with H2O and EC. HF formation from POF3 occurs with a reaction enthalpy of -3.8 kJ mol-1 and a 157.7 kJ mol-1 barrier, 43.5 kJ mol-1 higher than forming HF from PF5. HF generation in electrolytes employing LiPOF4 should be significantly lower than those using LiPF6 or LiAsF6 and LiPOF4 should be further investigated as an alternative electrolyte additive.

  12. Stability of amorphous pharmaceutical solids: crystal growth mechanisms and effect of polymer additives.

    Sun, Ye; Zhu, Lei; Wu, Tian; Cai, Ting; Gunn, Erica M; Yu, Lian

    2012-09-01

    We review recent progress toward understanding and enhancing the stability of amorphous pharmaceutical solids against crystallization. As organic liquids are cooled to become glasses, fast modes of crystal growth can emerge. One such growth mode, the glass-to-crystal or GC mode, occurs in the bulk, and another exists at the free surface, both leading to crystal growth much faster than predicted by theories that assume diffusion defines the kinetic barrier of crystallization. These phenomena have received different explanations, and we propose that GC growth is a solid-state transformation enabled by local mobility in glasses and that fast surface crystal growth is facilitated by surface molecular mobility. In the second part, we review recent findings concerning the effect of polymer additives on crystallization in organic glasses. Low-concentration polymer additives can strongly inhibit crystal growth in the bulk of organic glasses, while having weaker effect on surface crystal growth. Ultra-thin polymer coatings can inhibit surface crystallization. Recent work has shown the importance of molecular weight for crystallization inhibitors of organic glasses, besides "direct intermolecular interactions" such as hydrogen bonding. Relative to polyvinylpyrrolidone, the VP dimer is far less effective in inhibiting crystal growth in amorphous nifedipine. Further work is suggested for better understanding of crystallization of amorphous organic solids and the prediction of their stability. PMID:22434258

  13. Effect of Y addition on the interfacial microstructures and mechanical properties of C{sub f}/Mg composites

    Zhang, Shaofeng; Chen, Guoqin; Pei, Risheng; Li, Daguang; Wang, Pingping [School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001 (China); Wu, Gaohui, E-mail: wugh@hit.edu.cn [School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001 (China); Welding Production Technology National Key Laboratory, Harbin Institute of Technology, Harbin 150001 (China)

    2014-09-08

    Magnesium (Mg) alloy containing 1 wt% Yttrium (Y) reinforced with 60 vol% carbon fiber (C{sub f}) composites was fabricated by the pressure infiltration method. The morphological study with Y addition in the composite revealed that the Y element was prone to segregate on the surface of the carbon fiber during the fabrication process, forming plate-like intermetallic compound Mg{sub 2}Y. The mechanical properties of the composite were investigated by a flexure test and a short-beam shear test. The results showed that the addition of Y element to the composite improved the bending strength and interlaminar shear strength greatly. A study of the fracture mechanism uncovered the important role of Y addition on the interface bonding strength of the C{sub f}/Mg composite.

  14. Mechanical alloying process of vanadium powder with 1.7 wt.%Y addition

    Alloying process of vanadium-yttrium powders using mechanical alloying (MA) method was studied. Vanadium powder was compressed after 10 h MA, while yttrium powder was comminuted into small particles. Although yttrium powder was broken into small particles, yttrium scarcely dissolves into vanadium powder. Alloying of yttrium started after 20 h MA and finished after 40 h MA. Molybdenum particle, which came from milling vessels and balls, mixed into vanadium powder after 40 h MA and molybdenum started to dissolve into vanadium powder after 60 h MA. After 80 h MA, Y2O3 particles formed in vanadium powder. Oxygen required for the formation of Y2O3 particles was probably discharged from the vessel wall and balls after flaking of those surface layers. Since prolonged MA caused powder contamination, optimum MA time for making V-1.7Y alloy was 40 h.

  15. Structure and mechanical properties of Ti-5Cr based alloy with Mo addition

    The effects of molybdenum (Mo) on the structure and mechanical properties of a Ti-5Cr-based alloy were studied with an emphasis on improving its strength/modulus ratio. Commercially pure titanium (c.p. Ti) was used as a control. As-cast Ti-5Cr and a series of Ti-5Cr-xMo (x = 1, 3, 5, 7, 9 and 11 wt.%) alloys were prepared by using a commercial arc-melting vacuum-pressure casting system, and investigated with X-ray diffraction (XRD) for phase analysis. Three-point bending tests were performed to evaluate the mechanical properties of all specimens and their fractured surfaces were observed by using scanning electron microscopy (SEM). The experimental results indicated that Ti-5Cr-7Mo, Ti-5Cr-9Mo and Ti-5Cr-11Mo alloys exhibited ductile properties, and the β-phase Ti-5Cr-9Mo alloy exhibited the lowest bending modulus. However, the Ti-5Cr-3Mo and Ti-5Cr-5Mo alloys had much higher bending moduli due to the formation of the ω phase during quenching. It is noteworthy that the Ti-5Cr-9Mo alloy exhibited the highest bending strength/modulus ratios at 26.0, which is significantly higher than those of c.p. Ti (8.5) and Ti-5Cr (13.3). Furthermore, the elastically recoverable angle of the Ti-5Cr-9Mo alloy (30o) was greater than that of c.p. Ti (2.7o). The reasonably high strength (or high strength/modulus ratio) β-phase Ti-5Cr-9Mo alloy exhibited a low modulus, ductile property, and excellent elastic recovery capability, which qualifies it as a novel implant materials.

  16. Physical-mechanical properties of Bis-EMA based root canal sealer with different fillers addition

    Marcela Oliveira de Souza

    2015-01-01

    Full Text Available Aim: To evaluate influence of three different filler particles on an experimental Bisphenol A ethoxylated dimethacrylate (Bis-EMA based root filling material. Materials and Methods: Resin-based endodontic sealers were produced using Bis-EMA, camphorquinone, ethyl 4-dimethylaminobenzoate (EDAB, N, N-dihydroxyethyl-p-toluidine (DHEPT, butylated hydroxytoluene (BHT, and benzoyl peroxide. The experimental groups were formulated adding 10, 20, 30, 40, and 50% of calcium tungstate (CaWO 4 , ytterbium trifluoride(YbF 3 , and tantalum oxide(Ta 2 O 5 . Flow, thickness, and radiopacity tests were conducted in accordance with ISO 6876. Sorption and solubility (SL tests were conducted in accordance with ISO 4049, pH was measured with a pH meter, and degree of conversion (DC was evaluated with Fourier transform infrared spectroscopy (FTIR. For radiopacity, two-way analysis of variance (ANOVA and Tukey′s multiple comparison test was performed. For DC analysis, one-way ANOVA and Tukey′s multiple comparison test was performed. All statistical analyses were performed with a significance level of 5%. Results: All groups showed lower flow with increased filler concentration. All groups showed film thickness values lower than 50μm, as ISO recommends, except CaWO 4 50% group (76.7μm. pH values varied from 5.95 (± 0.07 in YbF 3 40% group to 6.90 (± 0.07 in Ta 2 O 5 40% group. In the radiopacity test, YbF 3 30%, Ta 2 O 5 40%, and Ta 2 O 5 50% groups showed no statistical significant difference to 3mmAl. Ta 2 O 5 and YbF 3 groups in 10, 20, and 30% concentrations presented sorption and SL values as ISOrecommendation. Addition ofTa 2 O 5 and CaWO 4 decreased DC after 14 days. YbF 3 addition showed no difference in DC from control group. Conclusion: YbF 3 filler addition promoted higher properties compared to CaWO 4 and Ta 2 O 5 on Bis-EMA based root canal sealer.

  17. Metal and pharmaceutical mixtures: Is ion loss the mechanism underlying acute toxicity and widespread additive toxicity in zebrafish?

    Highlights: •Zebrafish larvae were used to test the acute toxicity of contaminant mixtures. •Interactions were observed between metals, ammonia and pharmaceuticals. •Larval Na+ loss was observed with exposure to all acutely toxic contaminants tested. •Water quality criteria should recognize the toxic interactions between contaminants. -- Abstract: The acute toxicities and mechanisms of action of a variety of environmental contaminants were examined using zebrafish larvae (Danio rerio; 4–8 days post fertilization). Toxic interactions were observed between metals. For example, the addition of a sublethal level of nickel (15% of the LC50, one third of the LC01) to all copper treatments decreased the copper 96 h LC50 by 58%, while sublethal copper exposure (6% of the copper LC50, 13% of the LC01) decreased the cadmium 96 h LC50 by 47%. Two predictive models were assessed, the concentration addition (CA) model, which assumes similar mechanisms of action, and the independent action (IA) model, which assumes different mechanisms of action. Quantitative comparisons indicated the CA model performed better than the IA model; the latter tended to underestimate combined toxicity to a greater extent. The effects of mixtures with nickel or ammonia were typically additive, while mixtures with copper or cadmium were typically greater than additive. Larvae exposed to cadmium, copper or nickel experienced whole body ion loss. Decreases were greatest for Na+ followed by K+ (as high as 19% and 9%, respectively, in 24 h). Additive toxicity between copper and other pharmaceutical compounds such as fluoxetine (Prozac™), β-naphthoflavone, estrogen and 17α-ethinylestradiol were also observed. Similar to metals, acutely toxic concentrations of fluoxetine, β-naphthoflavone and ammonia all decreased whole body Na+ and K+. Overall, whole body Na+ loss showed the greatest correlation with mortality across a variety of toxicants. We theorize that a disruption of ion homeostasis

  18. Nano-tribological properties and mechanisms of the liquid crystal as an additive

    2001-01-01

    Under conditions of low speed, small viscosity and molecularly smooth tribo-surfaces, the behavior of lubricant film in the nano scale is different from that in elasto-hydrodynamic lubrication (EHL) and boundary lubrication (BL). Due to the size effect, long-range ordered structure of liquid crystal (LC) has great effects on the tribological prop-erties and film-forming mechanism of thin film in the nano scale. The technique of relative optical interference intensity (ROII) was used to investigate nano-tribological properties when cholesteryl LCs are added to hexadecane. The results indicate that the practical film thickness of hexadecane with liquid crystal is 3-5 times as large as that expected from EHL theory in the low speed region. The film thickness in-creases with the enhancement in polarity and concentration of LC in hexadecane, and external DC voltage. The effective viscosity of lubricant is related to the film thickness and the voltage and it varies from bulk viscosity to several times or tens of times of bulk viscosity with reducing film thickness, and slowly rises with increasing external DC voltage and then trends to a constant. The higher ordered degree of mo-lecules close to solid surfaces gives rise to a thicker film.

  19. Influence of the montmorillonite clay addition on the mechanical properties and crystallinity of polyamide 6

    Polyamide 6 (PA6) and montmorillonite clay nano composites were prepared by twin-screw extruder using three different screw speeds: 150, 250 and 350 rpm. The processed samples were submitted to the characterization by x-ray diffraction (XRD) through thin films to analyze the clay dispersion in PA6. Despite the 250 rpm processed sample present better dispersion, the result could not be significant compared to the others. The 250 rpm processed sample were characterized by mechanical tests which presented increase of the apparent elastic modulus and tensile resistance while there was the decrease of the elongation at break and the impact resistance of the nanocomposite compared to the pure PA6. The evaluation of the crystallinity of nanocomposites was performed by XRD in the longitudinal and transversal direction to the flow injection of impact samples and shows that montmorillonite acts as nucleating agent and promotes an increase of crystallinity of PA6. The crystallinity obtained in the longitudinal direction of injection flow was higher due to the orientation of the chains imposed by the injection flow. (author)

  20. Precipitation strengthening and mechanical properties of ultra low carbon bainitic steel with Cu addition

    Effect of ageing parameters on tensile properties and impact energy of ultra low carbon bainitic steel (ULCB) was established. The investigated HN3MCu1.5 steel belongs to a new group of structural steels, which are going to be applied for constructions working at low temperatures.. The chemical composition of the steel is given. The microstructure of the steel after ageing at temperature 640oC during to 100 hours was observed by optical and electron microscopy. Special attention was paid to study primary austenite grain size, which determines the average diameter of bainite-martensite packet size and thus the impact transition temperature according to empirical equations. Then the quantitative determination of the average diameter of precipitates and the interparticle spacing was studied to calculate the precipitation strengthening effect on yield strength. The empirical equation, which relates effect of ageing time to the yield strength was determined. It was established that the optimum mechanical properties of HN3MCu1.5 steel aged at 649oC are achieved for ageing time in the range of 1 - 10 hours. For the above ageing parameters the investigated steels had: YS = 700-661 MPa, TS = 814-741 MPa and impact energy KCV = 150-170 J determined on Charpy V specimens at temperature -80oC. (author)

  1. Energy efficient reduced graphene oxide additives: Mechanism of effective lubrication and antiwear properties

    Gupta, Bhavana; Kumar, N.; Panda, Kalpataru; Dash, S.; Tyagi, A. K.

    2016-01-01

    Optimized concentration of reduced graphene oxide (rGO) in the lube is one of the important factors for effective lubrication of solid body contacts. At sufficiently lower concentration, the lubrication is ineffective and friction/wear is dominated by base oil. In contrast, at sufficiently higher concentration, the rGO sheets aggregates in the oil and weak interlayer sliding characteristic of graphene sheets is no more active for providing lubrication. However, at optimized concentration, friction coefficient and wear is remarkably reduced to 70% and 50%, respectively, as compared to neat oil. Traditionally, such lubrication is described by graphene/graphite particle deposited in contact surfaces that provides lower shear strength of boundary tribofilm. In the present investigation, graphene/graphite tribofilm was absent and existing traditional lubrication mechanism for the reduction of friction and wear is ruled out. It is demonstrated that effective lubrication is possible, if rGO is chemically linked with PEG molecules through hydrogen bonding and PEG intercalated graphene sheets provide sufficiently lower shear strength of freely suspended composite tribofilm under the contact pressure. The work revealed that physical deposition and adsorption of the graphene sheets in the metallic contacts is not necessary for the lubrication.

  2. In situ polymerized wood polymer composite: effect of additives and nanoclay on the thermal, mechanical properties

    Devi, Rashmi R; Maji, Tarun K., E-mail: tkm@tezu.ernet.in [Department of Chemical Sciences, Tezpur University, Assam, (India)

    2013-11-01

    This study concerns the preparation and characterization of wood polymer nanocomposites based on impregnation of styrene acrylonitrile co-polymer-nanoclay intercalating system in presence of glycidyl methacrylate (GMA), a cross linking agent, and vinyl trichloro silane (VTCS) as additives into Simul (Bombex ceiba, L.), a soft wood. The effect of nanoclay and VTCS on the properties of the resultant wood polymer nanocomposites (WPNC) has been evaluated. FTIR spectroscopy shows the interaction among wood, polymers, GMA, nanoclay and VTCS. The penetration of polymer and nanoclay into the wood cell wall is supported by SEM study. The distribution of nanoclay in the SAN polymer matrix present within the wood cell wall has been evidenced by TEM study. TGA results show an improvement in the thermostability of the resultant composites. The inclusion of VTCS enhances the self extinguishing behaviour of the WPNC as revealed by limiting oxygen index (LOI) test. Due to treatment, the resultant WPNC exhibits an improvement in all the properties like water repellency, dimensional stability, hardness, flexural, tensile and thermal stability compared to untreated wood. (author)

  3. Effect of vanadium addition on the microstructure and mechanical properties of the ODS ferritic steels

    In this work, the effects of vanadium addition in the range of 0.3–3% (in weight percent) for an oxide dispersion strengthened reduced activation ferritic (ODS RAF) steel were investigated. Samples of the V-modified steel have been prepared using elemental (Fe, Cr, W, Ti) and Y2O3 powders with the nominal composition of Fe–14Cr–2W–0.3Ti–0.3Y2O3. Consolidated and heat treated samples were investigated using Scanning Electron Microscopy and Scanning Transmission Electron Microscopy equipped with Electron Energy Loss Spectroscopy detector. Hardness and Charpy impact tests (KLST specimens) were also performed. The microstructure investigations revealed numerous particles of the size up to 0.5 μm. They are primarily Ti–Cr–V oxides located at the grain boundaries and inside the grains. These particles increase hardness and significantly reduce fracture resistance of the ODS RAF alloys developed here. However, it should be noted that the 0.3% V-ODS steel has unexpectedly the lowest transition temperature of about 282 K and that the 1–3% V-ODS steels, in spite of the transition temperature about 373 K, exhibit almost two times higher the lower shelf energy values in comparison with the 0.3% V-ODS and 0% V-ODS steels

  4. Effects of Zn addition on the glass forming ability and mechanical properties of Mg–Cu–Gd bulk metallic glasses

    Highlights: • Mg-Zn-Cu-Gd BMGs with 2 mm diameter are fabricated by copper mold casting method. • The σf and Hv of the Mg60Zn5Cu25Gd10 reach up to 754 MPa and 286 Hv, respectively. • The Mg60Zn5Cu25Gd10 alloy exhibits plastic deformation characteristic at micro-level. -- Abstract: The effects of Zn addition on the glass forming ability (GFA) and mechanical properties are investigated in Mg65−xZnxCu25Gd10 (x = 0, 3, 5, 8 at.%) alloys by X-ray diffractometer (XRD), differential scanning calorimeter (DSC) and mechanical property tests. Thermal analysis shows that with the increasing of Zn content from 0 to 8 at.%, the supercooled liquid regions of Mg65−xZnxCu25Gd10 alloys decrease from 68 K to 31 K, indicating the obvious deterioration in their GFA. On the other hand, however, the mechanical property tests demonstrate that the appropriate addition of Zn (5 at.%) in Mg65−xZnxCu25Gd10 alloys greatly improves the mechanical strength, increases their compressive fracture strength and Vickers hardness from 648 MPa and 257 Hv to 754 MPa and 286 Hv, respectively. In addition, the fracture surface morphologies have been characterized by scanning electron microscopy (SEM) and the dominant fracture behaviors of the as-cast alloys have been explained as well

  5. Effects of rare earth Er addition on microstructure and mechanical properties of hypereutectic Al–20% Si alloy

    Li, Qinglin [School of Materials Science and Engineering, Lanzhou University of Technology, Lanzhou 730050 (China); State Key Laboratory of Gansu Advanced Non-ferrous Metal Materials, Lanzhou University of Technology, Lanzhou 730050 (China); Xia, Tiandong, E-mail: liql301@mail.nwpu.edu.cn [School of Materials Science and Engineering, Lanzhou University of Technology, Lanzhou 730050 (China); State Key Laboratory of Gansu Advanced Non-ferrous Metal Materials, Lanzhou University of Technology, Lanzhou 730050 (China); Lan, Yefeng [School of Materials Science and Engineering, Lanzhou University of Technology, Lanzhou 730050 (China); State Key Laboratory of Gansu Advanced Non-ferrous Metal Materials, Lanzhou University of Technology, Lanzhou 730050 (China); Li, Pengfei; Fan, Lu [School of Materials Science and Engineering, Lanzhou University of Technology, Lanzhou 730050 (China)

    2013-12-20

    The microstructure evolution and mechanical properties of hypereutectic Al–20%Si alloy with Er addition were investigated in the article. The as-cast samples were characterized by optical microscopy (OM), scanning electron microscopy (SEM) and electron probe microanalysis (EPMA). Microstructural analyses demonstrated that primary Si was significantly refined from coarse polygonal, platelet-like and star-like shape to fine blocky shape, and eutectic Si structure was modified from coarse platelet-like/needle-like structure to fine coral-like fibrous structure as the addition contents of Er is 0.5%. However, the primary and eutectic Si phases became coarser when the level of rare earth Er was up to 0.8%. The mechanical properties were investigated by tensile test with various concentration of Er. It was found that the ultimate tensile strength (UTS) and elongation (El) increased by 72.5% and 72%, respectively, due to decreasing of the size and changing of morphology on primary and eutectic Si crystals, and the change of mechanical properties corresponds to the evolution of microstructure. In addition, the modification mechanism of Er on Al–20%Si alloy was also discussed.

  6. Social-cognitive, physiological, and neural mechanisms underlying emotion regulation impairments: Understanding anxiety in autism spectrum disorder

    White, Susan W.; Mazefsky, Carla A.; Gabriel S Dichter; Chiu, Pearl H; Richey, John A.; Ollendick, Thomas H.

    2014-01-01

    Anxiety is one of the most common clinical problems among children, adolescents, and adults with autism spectrum disorder (ASD), yet we know little about its etiology in the context of ASD. We posit that emotion regulation (ER) impairments are a risk factor for anxiety in ASD. Specifically, we propose that one reason why anxiety disorders are so frequently comorbid with ASD is because ER impairments are ubiquitous to ASD, stemming from socio-cognitive, physiological, and neurological processe...

  7. Effects of Sn addition on the microstructure, mechanical properties and corrosion behavior of Ti–Nb–Sn alloys

    Moraes, Paulo E.L., E-mail: pauloeduardo.leitedemoraes@gmail.com [University of Campinas, School of Mechanical Engineering, Rua Mendeleiev, 200, Campinas, SP 13083-860 (Brazil); Contieri, Rodrigo J., E-mail: contieri@fem.unicamp.br [University of Campinas, School of Mechanical Engineering, Rua Mendeleiev, 200, Campinas, SP 13083-860 (Brazil); Lopes, Eder S.N., E-mail: ederlopes@fem.unicamp.br [University of Campinas, School of Mechanical Engineering, Rua Mendeleiev, 200, Campinas, SP 13083-860 (Brazil); Robin, Alain, E-mail: alain@demar.eel.usp.br [University of São Paulo, School of Engineering of Lorena, Polo Urbo-Industrial Gleba AI-6, Lorena, SP 12600-00 (Brazil); Caram, Rubens, E-mail: caram@fem.unicamp.br [University of Campinas, School of Mechanical Engineering, Rua Mendeleiev, 200, Campinas, SP 13083-860 (Brazil)

    2014-10-15

    Ti and Ti alloys are widely used in restorative surgery because of their good biocompatibility, enhanced mechanical behavior and high corrosion resistance in physiological media. The corrosion resistance of Ti-based materials is due to the spontaneous formation of the TiO{sub 2} oxide film on their surface, which exhibits elevated stability in biological fluids. Ti–Nb alloys, depending on the composition and the processing routes to which the alloys are subjected, have high mechanical strength combined with low elastic modulus. The addition of Sn to Ti–Nb alloys allows the phase transformations to be controlled, particularly the precipitation of ω phase. The aim of this study is to discuss the microstructure, mechanical properties and corrosion behavior of cast Ti–Nb alloys to which Sn has been added. Samples were centrifugally cast in a copper mold, and the microstructure was characterized using optical microscopy, scanning electron microscopy and X-ray diffractometry. Mechanical behavior evaluation was performed using Berkovich nanoindentation, Vickers hardness and compression tests. The corrosion behavior was evaluated in Ringer's solution at room temperature using electrochemical techniques. The results obtained suggested that the physical, mechanical and chemical behaviors of the Ti–Nb–Sn alloys are directly dependent on the Sn content. - Graphical abstract: Effects of Sn addition to the Ti–30Nb alloy on the elastic modulus. - Highlights: • Sn addition causes reduction of the ω phase precipitation. • Minimum Vickers hardness and elastic modulus occurred for 6 wt.% Sn content. • Addition of 6 wt.% Sn resulted in maximum ductility and minimum compression strength. • All Ti–30Nb–XSn (X = 0, 2, 4, 6, 8 and 10%) alloys are passive in Ringer's solution. • Highest corrosion resistance was observed for 6 wt.% Sn content.

  8. Polychlorinated biphenyls PCB 153 and PCB 126 impair the glutamate-nitric oxide-cGMP pathway in cerebellar neurons in culture by different mechanisms.

    Llansola, Marta; Piedrafita, Blanca; Rodrigo, Regina; Montoliu, Carmina; Felipo, Vicente

    2009-08-01

    Polychlorinated biphenyls (PCBs) are persistent organic pollutants present in human blood and milk. Exposure to PCBs during pregnancy and lactation leads to cognitive impairment in children. Perinatal exposure to PCB 153 or PCB 126 impairs the glutamate-nitric oxide-cGMP pathway in cerebellum in vivo and learning ability in adult rats. The aims of this work were: (1) to assess whether long-term exposure of primary cultures of cerebellar neurons to PCB 153 or PCB 126 reproduces the impairment in the function of the glutamate-nitric oxide-cGMP pathway found in rat cerebellum in vivo; (2) to provide some insight on the steps of the pathway affected by these PCBs; (3) to assess whether the mechanisms of interference of the pathway are different for PCB 126 and PCB 153. Both PCB 153 and PCB 126 increase basal levels of cGMP by different mechanisms. PCB 126 increases the amount of soluble guanylate cyclase while PCB 153 does not. PCB 153 reduces the amount of calmodulin while PCB 126 does not. Also both PCBs impair the function of the glutamate-nitric oxide-cGMP pathway by different mechanisms, PCB 153 impairs nitric oxide-induced activation of soluble guanylate cyclase and increase in cGMP while PCB 126 does not. PCB 126 reduces NMDA-induced increase in calcium while PCB 153 does not. When PCB 153 and PCB 126 exhibit the same effect, PCB 126 was more potent than PCB 153, as occurs in vivo. PMID:19526286

  9. Mechanism and Optimal Application of Chemical Additives for Accelerating Early Strength of Lime-flyash Stabilized Soils

    JIANG Zengguo; ZHAO Yuan

    2005-01-01

    To accelerate the early strength of lime-flyash stabilized soil for extending its further uses in highway and shortening highway construction time, five kinds of chemical additives were chosen on the basis of mechanism analysis of accelerating early strength in highway as a semi-rigid base material, and a series of experiments about the effect of different kinds of additives and quantity on the early strength of the stabilized soil were tested. The results show that chemical additives can efficiently improve the early strength of lime-flyash stabilized soil both the 7 d and 28d, and the optimum quantity for above chemical additive is 1.5%-2.5% approximately.Some suggestions for the practical construction were also proposed.

  10. Effect of molybdenum addition on the mechanical properties of sinter-forged Fe–Cu–C alloys

    Rathore, Sanjay S., E-mail: rathore.sanjaysingh@gmail.com; Salve, Milind M., E-mail: milindrowling@gmail.com; Dabhade, Vikram V., E-mail: vvdabfmt@iitr.ac.in

    2015-11-15

    Molybdenum provides solid solution strengthening, enhances hardenability and has thus been used to improve mechanical properties of ferrous alloys significantly. The present study reports the effect of molybdenum addition on the properties of sinter-forged Fe–Cu–C alloys prepared using elemental powders under various heat treatment conditions. The elemental powder mixtures were compacted at a pressure of 500 MPa followed by sintering at 1120 °C in N{sub 2}–20%H{sub 2} atmosphere. Further, the sintered compacts were immediately forged at the sintering temperature in a closed die. The sinter-forged compacts were further homogenized and then heat treated under different cooling rates. Enhancement of the mechanical properties (hardness and tensile strength) were observed with Mo addition and increase in severity of quench. Hardness of air cooled samples was slightly lower than that of the water quenched samples but comparable with oil quenched samples. However, no significant increase in hardness was observed beyond 1.5 wt% Mo addition for all cooling conditions. At higher molybdenum content ductility was retained due to stabilization of ferrite phase by molybdenum. The microstructural study showed mostly ferrite–pearlite structure in furnace cooled condition whereas a complex microstructure was observed in the faster cooling conditions. Grain refinement was also observed with molybdenum addition. - Highlights: • Mo (0.25–4.0 wt%) addition in sinter-forged Fe–2Cu–0.65C alloys was investigated. • Effect of heat treatment on mechanical properties and microstructure was discussed. • Hardness and strength increased with Mo addition at the expense of ductility. • Hardness in air cooled condition was comparable with oil/water cooled conditions.

  11. Effect of molybdenum addition on the mechanical properties of sinter-forged Fe–Cu–C alloys

    Molybdenum provides solid solution strengthening, enhances hardenability and has thus been used to improve mechanical properties of ferrous alloys significantly. The present study reports the effect of molybdenum addition on the properties of sinter-forged Fe–Cu–C alloys prepared using elemental powders under various heat treatment conditions. The elemental powder mixtures were compacted at a pressure of 500 MPa followed by sintering at 1120 °C in N2–20%H2 atmosphere. Further, the sintered compacts were immediately forged at the sintering temperature in a closed die. The sinter-forged compacts were further homogenized and then heat treated under different cooling rates. Enhancement of the mechanical properties (hardness and tensile strength) were observed with Mo addition and increase in severity of quench. Hardness of air cooled samples was slightly lower than that of the water quenched samples but comparable with oil quenched samples. However, no significant increase in hardness was observed beyond 1.5 wt% Mo addition for all cooling conditions. At higher molybdenum content ductility was retained due to stabilization of ferrite phase by molybdenum. The microstructural study showed mostly ferrite–pearlite structure in furnace cooled condition whereas a complex microstructure was observed in the faster cooling conditions. Grain refinement was also observed with molybdenum addition. - Highlights: • Mo (0.25–4.0 wt%) addition in sinter-forged Fe–2Cu–0.65C alloys was investigated. • Effect of heat treatment on mechanical properties and microstructure was discussed. • Hardness and strength increased with Mo addition at the expense of ductility. • Hardness in air cooled condition was comparable with oil/water cooled conditions

  12. The Influence of Nickel and Tin Additives on the Microstructural and Mechanical Properties of Al-Zn-Mg-Cu Alloys

    Naeem, Haider T.; Mohammed, Kahtan S.; Ahmad, Khairel R.; Azmi Rahmat

    2014-01-01

    The effects of nickel and nickel combined tin additions on mechanical properties and microstructural evolutions of aluminum-zinc-magnesium-copper alloys were investigated. Aluminum alloys containing Ni and Sn additives were homogenized at different temperatures conditions and then aged at 120°C for 24 h (T6) and retrogressed at 180°C for 30 min and then reaged at 120°C for 24 h (RRA). Comparison of the ultimate tensile strength (UTS) of as-quenched Al-Zn-Mg-Cu-Ni and Al-Zn-Mg-Cu-Ni-Sn alloys ...

  13. Effect of nitrogen on structure and mechanical properties of ductile iron with small additions vanadium and niobium

    Fraś E.

    2007-01-01

    Full Text Available Results of investigations of influence of small additions of vanadium (about 0,08 and 0,12 % V and niobium (about 0,05 and 0,16% Nb as well as nitrogen (32 - 58 ppm. on mechanical properties and structure of ductile iron is presented. Effect of these additions on graphite diameter distribution, nodule count, and ferrite fraction is determined. It has been also shown that vanadium and niobium lead to formation of their complex carbides, while nitrogen – complex carbide-nitrides containing magnesium and silicon.

  14. Effect of nitrogen on structure and mechanical properties of ductile iron with small additions vanadium and niobium

    Fraś E.; Górny M.; Kawalec M.

    2007-01-01

    Results of investigations of influence of small additions of vanadium (about 0,08 and 0,12 % V) and niobium (about 0,05 and 0,16% Nb) as well as nitrogen (32 - 58 ppm.) on mechanical properties and structure of ductile iron is presented. Effect of these additions on graphite diameter distribution, nodule count, and ferrite fraction is determined. It has been also shown that vanadium and niobium lead to formation of their complex carbides, while nitrogen – complex carbide-nitrides containing m...

  15. Polychlorinated biphenyls PCB 52, PCB 180, and PCB 138 impair the glutamate-nitric oxide-cGMP pathway in cerebellar neurons in culture by different mechanisms.

    Llansola, Marta; Montoliu, Carmina; Boix, Jordi; Felipo, Vicente

    2010-04-19

    Polychlorinated biphenyls (PCBs) are persistent organic pollutants that accumulate in the food chain and are present in human blood and milk. Children born to mothers exposed to PCBs show cognitive deficits, which are reproduced in rats perinatally exposed to PCBs. It has been proposed that PCB-induced cognitive impairment is due to impairment of the glutamate-nitric oxide (NO)-cGMP pathway. The aim of the present work was to assess whether chronic exposure to the nondioxin-like PCB52, PCB138, or PCB180 alters the function of this pathway in primary cultures of rat cerebellar neurons and to assess whether different PCBs have similar or different mechanisms of action. PCB180 and PCB138 impair the function of the glutamate-NO-cGMP pathway at nanomolar concentrations, and PCB52 impairs the function of the glutamate-NO-cGMP pathway at micromolar concentrations. The mechanisms by which different PCBs impair the function of the glutamate-NO-cGMP pathway are different. Each PCB affects the pathway at more than one step but with different potency and, for some steps, in opposite ways. Exposure to the PCBs alters the basal concentrations of intracellular calcium, NO, and cGMP. The three PCBs increase NO; however, PCB52 and PCB138 increase basal cGMP, while PCB180 decreases it. PCB52 and PCB138 decrease the activation of soluble guanylate cyclase by NO, and PCB180 increases it. Long-term exposure to PCB52, PCB180, or PCB138 reduces the activation of NO synthase and the whole glutamate-NO-cGMP pathway in response to activation of N-methyl-d-aspartate receptors. The EC(50) was 300 nM for PCB52 and 2 nM for PCB138 or PCB180. These results show that chronic exposure to nondioxin like PCBs impairs the function of the glutamate-NO-cGMP pathway in cerebellar neurons by different mechanisms and with different potencies. Impaired function of this pathway would contribute to the cognitive alterations induced by perinatal exposure to PCBs in humans. PMID:20297801

  16. Additive manufacturing and mechanical characterization of graded porosity scaffolds designed based on triply periodic minimal surface architectures.

    Afshar, M; Anaraki, A Pourkamali; Montazerian, H; Kadkhodapour, J

    2016-09-01

    Since the advent of additive manufacturing techniques, triply periodic minimal surfaces have emerged as a novel tool for designing porous scaffolds. Whereas scaffolds are expected to provide multifunctional performance, spatially changing pore patterns have been a promising approach to integrate mechanical characteristics of different architectures into a unique scaffold. Smooth morphological variations are also frequently seen in nature particularly in bone and cartilage structures and can be inspiring for designing of artificial tissues. In this study, we carried out experimental and numerical procedures to uncover the mechanical properties and deformation mechanisms of linearly graded porosity scaffolds for two different mathematically defined pore structures. Among TPMS-based scaffolds, P and D surfaces were subjected to gradient modeling to explore the mechanical responses for stretching and bending dominated deformations, respectively. Moreover, the results were compared to their corresponding uniform porosity structures. Mechanical properties were found to be by far greater for the stretching dominated structure (P-Surface). For bending dominated architecture (D-Surface), although there was no global fracture for uniform structures, graded structure showed a brittle fracture at 0.08 strain. A layer by layer deformation mechanism for stretching dominated structure was observed. For bending dominated scaffolds, deformation was accompanied by development of 45° shearing bands. Finite element simulations were also performed and the results showed a good agreement with the experimental observations. PMID:27281165

  17. Additive Effects of Mechanical Marrow Ablation and PTH Treatment on de Novo Bone Formation in Mature Adult Rats

    Jodi A. Carlson Scholz; Agnès Vignery; James Gilligan; Nozer Mehta; Xiaoqing Xu; Christopher Miller; Jesse Bible; Jiliang Li; Qing Zhang,

    2012-01-01

    Mechanical ablation of bone marrow in young rats induces rapid but transient bone growth, which can be enhanced and maintained for three weeks by the administration of parathyroid hormone (PTH). Additionally, marrow ablation, followed by PTH treatment for three months leads to increased cortical thickness. In this study, we sought to determine whether PTH enhances bone formation after marrow ablation in aged rats. Aged rats underwent unilateral femoral marrow ablation and treatment with PTH o...

  18. Effect of pMDI isocyanate additive on mechanical and thermal properties of Kenaf fibre reinforced thermoplastic polyurethane composites

    Y A El-Shekeil; S M Sapuan; K Abdan; E S Zainudin; O M Al-Shuja’a

    2012-12-01

    The effect of polymeric methylene diphenyl diisocyanate (pMDI) on mechanical and thermal properties of Kenaf fibre (KF) reinforced thermoplastic polyurethane (TPU) composites was studied. Various percentages viz. 2%, 4% and 6%, were studied. The composites were characterized by using tensile testing, thermogravimetric analysis (TG), differential scanning calorimetry (DSC) and fourier transform infrared spectroscopy (FTIR). It was noticed that the addition of pMDI 2%, 4%and 6% did not induce a better tensile nor thermal properties.

  19. Effect of additives on mechanical and electrical properties of semi organic non linear material-γ-glycine

    Ravishankar, M. N.; Chandramani, R.; Prakash, A. P. Gnana

    2012-06-01

    The semi-organic non-linear optical (NLO) crystals of γ-Glycine (G), with additives like Ammonium Oxalate (AO), Barium Nitrate (BN) and Potassium Nitrate (PN) were grown by aqueous solution method. The mechanical properties, dielectric constant, dielectric loss, AC conductivity of the grown crystals were studied. Studies confirm that the grown NLO crystals retain the merits of organic (SHG response and flexibility) and inorganic (good hardness) properties.

  20. Thermo-mechanical analysis of Wire and Arc Additive Layer Manufacturing process on large multi-layer parts

    Ding, J.; Colegrove, Paul A.; Mehnen, Jorn; Ganguly, Supriyo; Sequeira Almeida, P. M.; Wang, F.; Williams, Stewart W.

    2011-01-01

    Wire and Arc Additive Layer Manufacturing (WAALM) is gaining increasing popularity as the process allows the production of large custom-made metal workpieces with high deposition rates. The high power input of the welding process, causes significant residual stress and distortion of the workpiece. This paper describes the thermo-mechanical behaviour of the multi-layer wall structure made by the WAALM process. A 3D thermo-elastic–plastic transient model and a model based on a...

  1. Effects of Ti addition and reheating quenching on grain refinement and mechanical properties in low carbon medium manganese martensitic steel

    Highlights: → TiC precipitation can induce the grain refinement after reheating-quenching process. → EGS refinement is more effective to explain the improvement of toughness. → The experimental results of precipitation agree with the theoretical calculations. → Excellent mechanical properties with high strength and high toughness can be gained. -- Abstract: The grain refinement and mechanical properties improvement resulted from Ti addition and reheating quenching were demonstrated in this study. The direct quenched medium manganese steel with low carbon content (0.05C) was treated by reheating quenching process. The yield strength and Charpy impact energy were measured. The microstructures and the second precipitated particles were examined by optical microscopy (OM), scanning electron microscopy (SEM), electron back-scattered diffraction (EBSD), transmission electron microscopy (TEM), X-rays diffraction and phase analysis method. It was found that reheating quenching at 900-1000 oC resulted in significant grain refinement, especially the refinement of effective grain size (EGS), which was attributed to the large amount nano-sized precipitation of TiC. In addition, high elastic modulus was also obtained from the large amount TiC precipitated from the matrix. It is concluded that reheating quenching process is a useful method to refine the grain size and improve the combined mechanical properties of the martensitic steel through Ti addition.

  2. Effect of ZrO2 addition on the mechanical properties of porous TiO2 bone scaffolds.

    Tiainen, Hanna; Eder, Georg; Nilsen, Ola; Haugen, Håvard J

    2012-08-01

    This study aimed at the investigation of the effect of zirconium dioxide (ZrO2) addition on the mechanical properties of titanium dioxide (TiO2) bone scaffolds. The highly biocompatible TiO2 has been identified as a promising material for bone scaffolds, whereas the more bioinert ZrO2 is known for its excellent mechanical properties. Ultra-porous TiO2 scaffolds (>89% porosity) were produced using polymer sponge replication with 0-40 wt.% of the TiO2 raw material substituted with ZrO2. Microstructure, chemical composition, and pore architectural features of the prepared ceramic foams were characterised and related to their mechanical strength. Addition of 1 wt.% of ZrO2 led to 16% increase in the mean compressive strength without significant changes in the pore architectural parameters of TiO2 scaffolds. Further ZrO2 additions resulted in reduction of compressive strength in comparison to containing no ZrO2. The appearance of zirconium titanate (ZrTiO4) phase was found to hinder the densification of the ceramic material during sintering resulting in poor intergranular connections and thus significantly reducing the compressive strength of the highly porous ceramic foam scaffolds. PMID:24364936

  3. Influence of Al-Ti-B addition on the microstructure and mechanical properties of A356 alloys

    ZHU Man; YANG Gencang; YAO Lijuan; CHENG Suling; ZHOU Yaohe

    2009-01-01

    The mechanical properties (σb, σ0.2, and δ) and fracture behavior of tensile specimens of the refined A356 alloys were investigated as a func-tion of the addition level of Al-Ti-B master alloy under both as-cast and T6 hot-treated conditions. The results show that as the addition level of Al-5Ti- 1B master alloy increases from 0.1 wt.% to 5.0 wt.%, the mechanical properties of refined A356 alloys improve steadily and then decrease slightly under both as-cast and T6 heat-treated conditions. Also, they display excellent mechanical properties with σb = 231.30-258.30 Mpa, σ0.2 = 134.00-155.50 Mpa, and δ= 8.5%-11.75% at T6 heat-treated state. The excellent mechanical properties of refined A356 alloys are ascribed to the formation of a-Al equiaxed dendrites, the improvement of eutectic structure from needle/plate-like to short-lathy/block-shaped, and the Mg2Si aging precipitation phase after T6 heat treatment. The fracture surface examined by SEM exhibits a mixed fracture mode of refined A356 alloys at as-cast state, while it reveals a ductile fracture mode after T6 heat treatment.

  4. Influence of additional coupling agent on the mechanical properties of polyester-agave cantala roxb based composites

    Ubaidillah, Raharjo, Wijang W.; Wibowo, A.; Harjana, Mazlan, S. A.

    2016-03-01

    The mechanical and morphological properties of the unsaturated polyester resins (UPRs)-agave cantala roxb based composite are investigated in this paper. The cantala fiber woven in 3D angle interlock was utilized as the composite reinforcement. Surface grafting of the cantala fiber through chemical treatment was performed by introducing silane coupling agent to improving the compatibility with the polymer matrix. The fabrication of the composite specimens was conducted using vacuum bagging technique. The effect of additional coupling agent to the morphological appearance of surface fracture was observed using scanning electron microscopy. Meanwhile, the influence of additional silane to the mechanical properties was examined using tensile, bending and impact test. The photograph of surface fracture on the treated specimens showed the residual matrix left on the fibers in which the phenomenon was not found in the untreated specimens. Based on mechanical tests, the treated specimens were successfully increased their mechanical properties by 55%, 9.67%, and 92.4% for tensile strength, flexural strength, and impact strength, respectively, at 1.5% silane coupling agent.

  5. The effect of TiO2/aluminosilicate nanocomposite additives on the mechanical and thermal properties of polyacrylic coatings

    Nosrati, Rahimeh; Olad, Ali

    2015-12-01

    The commercial grade polyacrylic latex was modified in order to prepare a mechanical and thermal improved coating. TiO2/Ag-exchanged-aluminosilicate nanocomposites with montmorillonite, zeolite-A and clinoptilolite aluminosilicates were prepared and used as additive in the matrix of polyacrylic latex to achieve a coating with proper mechanical and thermal properties. X-ray diffraction patterns and FESEM were used to characterize the composition, structure, and morphology of the nanocomposite additives. Polyacrylic coatings modified by TiO2/Ag-exchanged-aluminosilicate nanocomposite additives showed higher adhesion strength and hardness compared to unmodified commercial grade polyacrylic coatings. Differential Scanning Calorimetry (DSC) analysis showed lower glass transition temperature for modified polyacrylic coatings than that of unmodified polyacrylic coatings. The tensile tests were also carried out for unmodified and modified polyacrylic coatings. According to the results, the modified polyacrylic based coating with TiO2/Ag-exchanged-clinoptilolite nanocomposite additive was the best coating considering most of useful properties.

  6. Effect of Cd and Sn Addition on the Microstructure and Mechanical Properties of Al-Si-Cu-Mg Cast Alloy

    LI Rong-de; LI Run-xia; YU Li; HU Zhuang-qi

    2004-01-01

    The present work has investigated the effect of trace elements Cd and Sn on the microstructure and mechanical properties of Al-Si-Cu-Mg cast alloy. With the increase of Cd addition the strength of alloy rises at first and then drops. The optimal amount of Cd and Sn addition for Al-Si-Cu-Mg alloy is about 0.27% and 0.1% respectively. Due to the formation of some coarse Cd-rich phases and pure Cd particles the mechanical properties of alloy decrease when Cd amount exceeds0.27%. When more than 0.1% Sn added, some Sn atoms form low-melting eutectic compound at grain boundary, and then cause over-burning in alloy when solution treated, which may deteriorate properties of alloy, especially ductility of alloy.On the other hand, the addition of Cd and Sn remarkably increases the peak hardness and reduces the time to reach aging peak in Al-Si-Cu-Mg alloy. The action of Cd/Sn in quaternary Al-Si-Cu-Mg alloy is effectively the same as that occur in binary Al-Cu alloy that the enhanced hardening associated with Cd / Sn addition is due to the promotion of the θ' phase.

  7. Role of quaternary additions on dislocated martensite, retain austenite and mechanical properties of Fe/Cr/C structural steels

    The influence of quaternary alloy additions of Mn and Ni to Fe/Cr/C steels which have been designed to provide superior mechanical properties has been investigated. Transmission electron microscopy and x-ray analysis revealed increasing amounts of retained austenite with Mn up to 2 w/o and with 5 w/o Ni additions after quenching from 11000C. This is accompanied by a corresponding improvement in toughness properties of the quaternary alloys. In addition, the generally attractive combinations of strength and toughness in these quaternary alloys is attributed to the production of dislocated lath martensite from a homogeneous austenite phase free from undissolved alloy carbides. Grain-refining resulted in a further increase in the amount of retained austenite

  8. Role of quaternary additions on dislocated martensite, retain austenite and mechanical properties of Fe/Cr/C structural steels

    Rao, B.V.N.

    1978-02-01

    The influence of quaternary alloy additions of Mn and Ni to Fe/Cr/C steels which have been designed to provide superior mechanical properties has been investigated. Transmission electron microscopy and x-ray analysis revealed increasing amounts of retained austenite with Mn up to 2 w/o and with 5 w/o Ni additions after quenching from 1100/sup 0/C. This is accompanied by a corresponding improvement in toughness properties of the quaternary alloys. In addition, the generally attractive combinations of strength and toughness in these quaternary alloys is attributed to the production of dislocated lath martensite from a homogeneous austenite phase free from undissolved alloy carbides. Grain-refining resulted in a further increase in the amount of retained austenite.

  9. Influence of strontium addition on the mechanical properties of gravity cast Mg-3Al-3Sn alloy

    Germen, Gülşah, E-mail: gulsahgermen@hotmail.com; Şevik, Hüseyin, E-mail: gulsahgermen@hotmail.com [Mersin University, Faculty of Engineering, Department of Metallurgical and Materials Engineering, Mersin, 33343 (Turkey); Kurnaz, S. Can [Sakarya University, Faculty of Engineering, Department of Metallurgical and Materials Engineering, Adapazarý, 54187 (Turkey)

    2013-12-16

    In this study, the effect of strontium (0.01, 0.1, 0.5, 1 wt%) addition on the microstructure and mechanical properties of the gravity cast Mg-3Al-3Sn alloy were investigated. X-ray diffractometry revealed that the main phases are α−Mg, β−Mg{sub 17}Al{sub 12} and Mg{sub 2}Sn in the Mg-3Al-3Sn alloy. With addition The tensile testing results showed that the yield and ultimate tensile strength and elongation of Mg-3Al-3Sn alloy increased by adding Sr up to 0.1 wt.% and then is gradually decreased with the addition of more alloying element.

  10. Influence of strontium addition on the mechanical properties of gravity cast Mg-3Al-3Sn alloy

    In this study, the effect of strontium (0.01, 0.1, 0.5, 1 wt%) addition on the microstructure and mechanical properties of the gravity cast Mg-3Al-3Sn alloy were investigated. X-ray diffractometry revealed that the main phases are α−Mg, β−Mg17Al12 and Mg2Sn in the Mg-3Al-3Sn alloy. With addition The tensile testing results showed that the yield and ultimate tensile strength and elongation of Mg-3Al-3Sn alloy increased by adding Sr up to 0.1 wt.% and then is gradually decreased with the addition of more alloying element

  11. Additive effect of BLA GABAA receptor mechanism and (+)-MK-801 on memory retention deficit, an isobologram analysis.

    Khakpoor, Mitra; Nasehi, Mohammad; Vahdati, Akbar; Hoseyni, Seyed-Ebrahim; Zarrindast, Mohammad-Reza

    2016-04-01

    There is a near correlation between N-methyl-d-aspartate (NMDA) and γ-aminobutyric acid (GABA) receptors in the modulation of learning and memory in the basolateral amygdala (BLA). In this study, we investigated the involvement of GABAA receptors in the BLA in amnesia induced by (+)-MK-801, a noncompetitive antagonist of NMDA receptors, in male Wistar rats. After guide cannulae were bilaterally placed in the BLA, animals were trained in a step-through type passive avoidance task and then tested 24h after training to measure memory retrieval and locomotor activity. Post-training intra-BLA microinjection of (+)-MK-801 (0.5μg/rat) and GABAA receptor agonists (muscimol at doses 0.05 and 0.1μg/rat) or antagonist (bicuculline at doses 0.05 and 0.1μg/rat) decreased step-through latency during retrieval but did not alter locomotor activity. Results also showed that a subthreshold dose of muscimol (0.025μg/rat) potentiated impairment induced by (+)-MK-801, whereas bicuculline (0.025μg/rat) restored it. Furthermore, the highest dose of muscimol (0.5μg/rat) increased locomotor activity induced by (+)-MK-801. Isobologram analysis showed that there was an additive but not synergistic effect between muscimol and (+)-MK-801 on memory retention deficits in the BLA. In conclusion, muscimol and bicuculline decreased retention of memory formation in the BLA, and GABAA receptors in the BLA may be involved in the additive effect on (+)-MK-801-induced memory retention deficits. PMID:26853734

  12. PARAMETER DETERMINATION FOR ADDITIONAL OPERATING FORCE MECHANISM IN DEVICE FOR PNEUMO-CENTRIFUGAL MACHINING OF BALL-SHAPED WORKPIECES

    A. A. Sukhotsky

    2015-01-01

    Full Text Available The paper describes development of the methodology for optimization of parameters for an additional operating force mechanism in a device for pneumo-centrifugal machining of glass balls. Specific feature in manufacturing glass balls for micro-optics in accordance with technological process for obtaining ball-shaped workpieces is grinding and polishing of spherical surface in a free state. In this case component billets of future balls are made in the form of cubes and the billets are given preliminary a form of ball with the help of rough grinding. An advanced method for obtaining ball-shaped work-pieces from brittle materials is a pneumocentrifugal machining. This method presupposes an application of two conic rings with abrasive working surfaces which are set coaxially with large diameters to each other and the billets are rolled along these rings. Rotation of the billets is conveyed by means of pressure medium.The present devices for pneumo-centrifugal machining are suitable for obtaining balls up to 6 mm. Machining of the work-pieces with full spherical surfaces and large diameter is non-productive due to impossibility to ensure a sufficient force on the billet in the working zone. For this reason the paper proposes a modified device where an additional force on the machined billet is created by upper working disc that is making a reciprocating motion along an axis of abrasive conic rings. The motion is realized with the help of a cylindrical camshaft mechanism in the form of a ring with a profile working end face and the purpose of present paper is to optimize parameters of the proposed device.The paper presents expressions for calculation of constitutive parameters of the additional operating force mechanism including parameters of loading element motion, main dimensions of the additional operating force mechanism and parameters of a profile element in the additional operating force mechanism.Investigation method is a mathematical

  13. Apparent anti-Woodward-Hoffmann addition to a nickel bis(dithiolene) complex: the reaction mechanism involves reduced, dimetallic intermediates.

    Dang, Li; Shibl, Mohamed F; Yang, Xinzheng; Harrison, Daniel J; Alak, Aiman; Lough, Alan J; Fekl, Ulrich; Brothers, Edward N; Hall, Michael B

    2013-04-01

    Nickel dithiolene complexes have been proposed as electrocatalysts for alkene purification. Recent studies of the ligand-based reactions of Ni(tfd)2 (tfd = S2C2(CF3)2) and its anion [Ni(tfd)2](-) with alkenes (ethylene and 1-hexene) showed that in the absence of the anion, the reaction proceeds most rapidly to form the intraligand adduct, which decomposes by releasing a substituted dihydrodithiin. However, the presence of the anion increases the rate of formation of the stable cis-interligand adduct, and decreases the rate of dihydrodithiin formation and decomposition. In spite of both computational and experimental studies, the mechanism, especially the role of the anion, remained somewhat elusive. We are now providing a combined experimental and computational study that addresses the mechanism and explains the role of the anion. A kinetic study (global analysis) for the reaction of 1-hexene is reported, which supports the following mechanism: (1) reversible intraligand addition, (2) oxidation of the intraligand addition product prior to decomposition, and (3) interligand adduct formation catalyzed by Ni(tfd)2(-). Density functional theory (DFT) calculations were performed on the Ni(tfd)2/Ni(tfd)2(-)/ethylene system to shed light on the selectivity of adduct formation in the absence of anion and on the mechanism in which Ni(tfd)2(-) shifts the reaction from intraligand addition to interligand addition. Computational results show that in the neutral system the free energy of activation for intraligand addition is lower than that for interligand addition, in agreement with the experimental results. The computations predict that the anion enhances the rate of the cis-interligand adduct formation by forming a dimetallic complex with the neutral complex. The [(Ni(tfd)2)2](-) dimetallic complex then coordinates ethylene and isomerizes to form a Ni,S-bound ethylene complex, which then rapidly isomerizes to the stable interligand adduct but not to the intraligand adduct

  14. Metal and pharmaceutical mixtures: Is ion loss the mechanism underlying acute toxicity and widespread additive toxicity in zebrafish?

    Alsop, Derek, E-mail: alsopde@mcmaster.ca; Wood, Chris M.

    2013-09-15

    Highlights: •Zebrafish larvae were used to test the acute toxicity of contaminant mixtures. •Interactions were observed between metals, ammonia and pharmaceuticals. •Larval Na{sup +} loss was observed with exposure to all acutely toxic contaminants tested. •Water quality criteria should recognize the toxic interactions between contaminants. -- Abstract: The acute toxicities and mechanisms of action of a variety of environmental contaminants were examined using zebrafish larvae (Danio rerio; 4–8 days post fertilization). Toxic interactions were observed between metals. For example, the addition of a sublethal level of nickel (15% of the LC{sub 50}, one third of the LC{sub 01}) to all copper treatments decreased the copper 96 h LC{sub 50} by 58%, while sublethal copper exposure (6% of the copper LC{sub 50}, 13% of the LC{sub 01}) decreased the cadmium 96 h LC{sub 50} by 47%. Two predictive models were assessed, the concentration addition (CA) model, which assumes similar mechanisms of action, and the independent action (IA) model, which assumes different mechanisms of action. Quantitative comparisons indicated the CA model performed better than the IA model; the latter tended to underestimate combined toxicity to a greater extent. The effects of mixtures with nickel or ammonia were typically additive, while mixtures with copper or cadmium were typically greater than additive. Larvae exposed to cadmium, copper or nickel experienced whole body ion loss. Decreases were greatest for Na{sup +} followed by K{sup +} (as high as 19% and 9%, respectively, in 24 h). Additive toxicity between copper and other pharmaceutical compounds such as fluoxetine (Prozac™), β-naphthoflavone, estrogen and 17α-ethinylestradiol were also observed. Similar to metals, acutely toxic concentrations of fluoxetine, β-naphthoflavone and ammonia all decreased whole body Na{sup +} and K{sup +}. Overall, whole body Na{sup +} loss showed the greatest correlation with mortality across a

  15. Effects of Mn addition on microstructures and mechanical properties of 10Cr ODS ferritic/martensitic steels

    Jin, Hyun Ju; Kim, Tae Kyu [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2014-10-15

    Ferritic/martensitic (FM) steels are very attractive for the structural materials of fast fission reactors such as a sodium cooled fast reactor (SFR) owing to their excellent irradiation resistance to a void swelling, but are known to reveal an abrupt loss of their creep and tensile strengths at temperatures above 600 .deg. C. Accordingly, high temperature strength should be considerably improved for an application of the FM steel to the structural materials of SFR. Oxide dispersion strengthened (ODS) FM steels are considered to be promising candidate materials for high- temperature components operating in severe environments such as nuclear fusion and fission systems due to their excellent high temperature strength and radiation resistance stemming from the addition of extremely thermally stable oxide particles dispersed in the ferritic/martensitic matrix.. To develop an advanced ODS steel for core structural materials for next generation nuclear reactor system applications, it is important to optimize its compositions to improve the high temperature strength and radiation resistance. This study investigates effects of Mn addition on microstructures and mechanical properties of 10Cr ODS FM steel. For this, two 10 Cr ODS FM steels were prepared by mechanical alloying (MA), hot isostatic pressing (HIP), and hot rolling process. Tensile tests were carried out at room temperature and 700 .deg. C to evaluate the influences of the Mn element on the mechanical properties. The microstructures were observed using SEM, electron back-scatter diffraction (EBSD) and transmission electron microscopy (TEM) with energy dispersive spectroscopy (EDS). In the present study, the effects of Mn addition on the microstructure and mechanical properties of ODS FM steels were investigated. The ODS FM steels were manufactured by the MA, HIP and hot-rolling processes.

  16. Effect of ZrO2 addition on the mechanical properties of porous TiO2 bone scaffolds

    This study aimed at the investigation of the effect of zirconium dioxide (ZrO2) addition on the mechanical properties of titanium dioxide (TiO2) bone scaffolds. The highly biocompatible TiO2 has been identified as a promising material for bone scaffolds, whereas the more bioinert ZrO2 is known for its excellent mechanical properties. Ultra-porous TiO2 scaffolds (> 89% porosity) were produced using polymer sponge replication with 0–40 wt.% of the TiO2 raw material substituted with ZrO2. Microstructure, chemical composition, and pore architectural features of the prepared ceramic foams were characterised and related to their mechanical strength. Addition of 1 wt.% of ZrO2 led to 16% increase in the mean compressive strength without significant changes in the pore architectural parameters of TiO2 scaffolds. Further ZrO2 additions resulted in reduction of compressive strength in comparison to containing no ZrO2. The appearance of zirconium titanate (ZrTiO4) phase was found to hinder the densification of the ceramic material during sintering resulting in poor intergranular connections and thus significantly reducing the compressive strength of the highly porous ceramic foam scaffolds. - Highlights: ► Open porous scaffold with porosity in the range of 89.0 to 92.8% produced. ► Adding 1 wt.% of ZrO2 led to 16% increase in strength without changing porosity. ► Further ZrO2 additions resulted in reduced compressive strength versus no ZrO2. ► Presence of zirconium titanate (ZrTiO4) phase found to hinder the densification. ► Appearance of ZrTiO4 resulted in poor intergranular connections.

  17. Synthesis and mechanical characterization of PZT/Sr based composite ceramics with addition of Si3N4

    In the Underwater Acoustics field, piezoelectric ceramics are the most usually employed materials for the conversion of mechanical energy (acoustic signal) into electric energy (electric signal) and vice-versa, in sensors (hydrophones) or hydroacoustic projectors. In the development of new compositions for these applications, piezoelectric performance is generally prioritized, to the expense of its mechanical properties. With this in mind, the object of this work was to study the effects of the addition of Si3N4 in the mechanical properties of PZT-Sr based electronic ceramics. Thus, a novel piezoelectric ceramic with the addition of small percentages in weight (0;0.1;1;3 and 5) of the structural ceramic Si3N4 was successfully processed by the oxide mixing route ; the compounds were sintered in a conventional at 1200 deg C for 2h. The densities of the compounds thus obtained for the different percentages of Si3N4 ranged from 55 to 97% and decreased with the increase of the content of Si3N4. Presence of equiaxial grains with normal growth was observed in all samples. MEV/EDS analysis of the micro-structures of the compositions detected the presence of a second phase rich in Zr, confirmed by DRX, which is a result of large quantities of volatilized PbO; the sintered pieces had their mechanical properties investigated by ultra-sonic inspection. It was observed that, among the sintered compositions, the PZT-Sr ceramic with 0.1% Si3N4 presented the smallest value for Young's Modulus E and Shear Modulus G, 75 Gpa and 28 Gpa, respectively. The Poisson's Coefficients ν tended to decrease with the increase of Si3N4 added to the PZT-Sr ceramic, indicating, thus, that the added compound may be used to adjust the mechanical properties of the material. (author)

  18. Effect of silver addition on the mechanical and field trapping properties of Gd-Ba-Cu-O bulk superconductors

    Nariki, S; Matsui, M; Murakami, M

    2002-01-01

    The effect of Ag addition on the microstructure and the mechanical and field trapping properties of Gd-Ba-Cu-O bulk superconductor has been investigated. The single grain Gd-Ba-Cu-O bulk superconductors 32 mm in diameter were fabricated with 0-30 mass%Ag/sub 2/O additions by the melt growth method under controlled oxygen partial pressure of 1.0%. From microscopic observations, it was found that the macro- cracks in the a-b plane decreased with Ag addition. The three-point bending test showed that the average strength of Ag-free bulk was 69 MPa at room temperature, while the strength was dramatically improved to 110-115 MPa with 10-30 mass%Ag/sub 2/O additions. The trapped magnetic field of Ag-free bulk sample was 1.3 T at 77 K. The trapped field of bulk Gd-Ba-Cu-O samples with 10-20 mass%Ag/sub 2/O exhibited high values of 1.8-2.0 T at 77 K. However, the trapped field of the sample with 30 mass%Ag/sub 2/O addition was lowered to 1.1 T with decreasing the critical current density. The trapped field of Ag- adde...

  19. Design rules for rational control of polymer glass formation behavior and mechanical properties with small molecular additives

    Mangalara, Jayachandra Hari; Simmons, David

    Small molecule additives have long been employed to tune polymers' glass formation, mechanical and transport properties. For example, plasticizers are commonly employed to suppress polymer Tg and soften the glassy state, while antiplasticizers, which stiffen the glassy state of a polymer while suppressing its Tg, are employed to enhance protein and tissue preservation in sugar glasses. Recent literature indicates that additives can have a wide range of possible effects, but all of these have not been clearly understood and well appreciated. Here we employ molecular dynamics simulations to establish design rules for the selection of small molecule additives with size, molecular stiffness, and interaction energy chosen to achieve targeted effects on polymer properties. We furthermore find that a given additive's effect on a polymer's Tg can be predicted from its Debye-Waller factor via a function previously found to describe nanoconfinement effects on the glass transition. These results emphasize the potential for a new generation of targeted molecular additives to contribute to more targeted rational design of polymers. We acknowledge the Keck Foundation and the Ohio Supercomputing Center for financial and computational support of this effort, respectively.

  20. In situ morphology studies of the mechanism for solution additive effects on the formation of bulk heterojunction films

    Richter, Lee J.

    2014-09-29

    The most successful active film morphology in organic photovoltaics is the bulk heterojunction (BHJ). The performance of a BHJ arises from a complex interplay of the spatial organization of the segregated donor and acceptor phases and the local order/quality of the respective phases. These critical morphological features develop dynamically during film formation, and it has become common practice to control them by the introduction of processing additives. Here, in situ grazing incidence X-ray diffraction (GIXD) and grazing incidence small angle X-ray scattering (GISAXS) studies of the development of order in BHJ films formed from the donor polymer poly(3-hexylthiophene) and acceptor phenyl-C61-butyric acid methyl ester under the influence of two common additives, 1,8-octanedithiol and 1-chloronaphthalene, are reported. By comparing optical aggregation to crystallization and using GISAXS to determine the number and nature of phases present during drying, two common mechanisms by which the additives increase P3HT crystallinity are identified. Additives accelerate the appearance of pre-crystalline nuclei by controlling solvent quality and allow for extended crystal growth by delaying the onset of PCBM-induced vitrification. The glass transition effects vary system-to-system and may be correlated to the number and composition of phases present during drying. Synchrotron X-ray scattering measurements of nanoscale structure evolution during the drying of polymer-fullerene photovoltaic films are described. Changes in the number and nature of phases, as well as the order within them, reveals the mechanisms by which formulation additives promote structural characteristics leading to higher power conversion efficiencies.

  1. Effect of samarium (Sm) addition on the microstructures and mechanical properties of Al–7Si–0.7Mg alloys

    Highlights: •Sm affected the secondary dendrite arm spacing of Al–7Si–0.7Mg alloy. •The coarse plate-like eutectic silicon was fully modified into a fine branched and particle structure when 0.6 wt.% Sm added. •The tensile properties were enhanced by the addition of Sm. •Sm has marked effects on eutectic temperature and the latent heat ΔHR on remelting behavior. •The morphology and chemical composition of Sm-rich intermetallics were studied. -- Abstract: The effects of samarium (Sm) additions (0–0.9 wt.%) on the microstructures and mechanical properties of Al–7Si–0.7Mg alloys have been studied in this article. The microstructures of the as-cast samples were examined by optical microscopy (OM) and scanning electron microscopy (SEM). The experimental results indicated that the rare earth Sm affected the secondary dendrite arm spacing (SDAS) of Al–7Si–0.7Mg alloy. And it was found that Sm had great modification effects on the microstructures of eutectic silicon. When 0.6 wt.% Sm was added to the alloy, the coarse plate-like eutectic silicon was fully modified into a fine fibrous structure; the dendrites of Al–7Si–0.7Mg alloy was best refined. The mechanical properties were investigated by tensile test. The findings indicate that the tensile properties and elongation were improved by the addition of Sm. And a good combination of ultimate tensile strength (215 MPa) and elongation (3.3%) was obtained when the Sm addition was up to 0.6 wt.%. Furthermore the results of thermal analysis reveal that Sm addition had marked effects on eutectic temperature and the latent heat ΔHR on remelting behavior

  2. Spark plasma sintered tantalum carbide: Effect of pressure and nano-boron carbide addition on microstructure and mechanical properties

    Research highlights: → Spark plasma sintering was used to synthesize 100% dense TaC and TaC-1 wt.% nano-size B4C. → Addition of B4C aided densification and inhibited grain coarsening. → High resolution TEM utilized to elucidate the sintering mechanism in TaC-nano B4C. → Improvement in the mechanical properties was observed by B4C addition. - Abstract: TaC and TaC-1 wt.% B4C powders were consolidated using spark plasma sintering (SPS) at 1850 deg. C and varying pressure of 100, 255 and 363 MPa. The effect of pressure on the densification and grain size is evaluated. The role of nano-sized B4C as sintering aid and grain growth inhibitor is studied by means of XRD, SEM and high resolution TEM. Fully dense TaC samples were produced at a pressure of 255 MPa and higher at 1850 deg. C. The increasing pressure also resulted in an increase in TaC grain size. Addition of B4C leads to an increase in the density of 100 MPa sample from 89% to 97%. B4C nano-powder resists grain growth even at high pressure of 363 MPa. The formation of TaB2/Carbon at TaC grain boundaries helps in pinning the grain boundary and inhibiting grain growth. The effect of B4C addition on hardness and elastic modulus measured by nanoindentation and the indentation fracture toughness has been studied. Relative fracture toughness increased by up to 93% on B4C addition.

  3. The effect of aluminum additions on the thermal, microstructural, and mechanical behavior of NiTiHf shape memory alloys

    Highlights: • We investigate the effect of aluminum on the thermomechanical properties of NiTiHf alloys. • The nanoscale structure of the alloys are investigated by advanced analytical techniques. • The Al solubility limit in NiTiHf was near 3 at.%. • Precipitation of both Heusler and Han phases are identified. • Al additions significantly affect transformation temperatures. - Abstract: Ni50Ti30−XHf20AlX (X = 0, 1, 2, 3, 4, 5 at.%) alloys were investigated using thermal, microstructural, and mechanical analysis. It was found that Al additions to this system decreased the transformation temperatures and thermal cyclic stability of the quaternary alloys. Also, the lenticular Han phase was observed in the aged 3–5% Al alloys in accordance with previous studies in literature performed at a similar aging temperature. Though no transformation was detected after DSC cycling down to −60 °C for the aged 4% and 5% Al alloys, mechanical testing confirmed pseudoelasticity. Additionally, TEM and atom probe analysis confirmed that aging at 600 °C resulted in precipitation of the Ni2TiAl Heusler phase and determined the Al solubility limit in the matrix as near 3 at.%. Lastly, precipitation strengthening by the Heusler phase was observed when comparing the solution-treated and aged 4% and 5% Al alloys. Microstructural evolution was further characterized using XRD, SEM and compression testing

  4. The effect of aluminum additions on the thermal, microstructural, and mechanical behavior of NiTiHf shape memory alloys

    Hsu, Derek Hsen Dai [Department of Materials Science and Engineering, University of Florida, 152 Rhines Hall, P.O. Box 116400, Gainesville, FL 32611 (United States); Hornbuckle, Billy Chad [Department of Metallurgical and Materials Engineering, The University of Alabama, Tuscaloosa, AL 35487 (United States); Valderrama, Billy; Barrie, Fatmata; Henderson, Hunter B. [Department of Materials Science and Engineering, University of Florida, 152 Rhines Hall, P.O. Box 116400, Gainesville, FL 32611 (United States); Thompson, Gregory B. [Department of Metallurgical and Materials Engineering, The University of Alabama, Tuscaloosa, AL 35487 (United States); Manuel, Michele V., E-mail: mmanuel@mse.ufl.edu [Department of Materials Science and Engineering, University of Florida, 152 Rhines Hall, P.O. Box 116400, Gainesville, FL 32611 (United States)

    2015-07-25

    Highlights: • We investigate the effect of aluminum on the thermomechanical properties of NiTiHf alloys. • The nanoscale structure of the alloys are investigated by advanced analytical techniques. • The Al solubility limit in NiTiHf was near 3 at.%. • Precipitation of both Heusler and Han phases are identified. • Al additions significantly affect transformation temperatures. - Abstract: Ni{sub 50}Ti{sub 30−X}Hf{sub 20}Al{sub X} (X = 0, 1, 2, 3, 4, 5 at.%) alloys were investigated using thermal, microstructural, and mechanical analysis. It was found that Al additions to this system decreased the transformation temperatures and thermal cyclic stability of the quaternary alloys. Also, the lenticular Han phase was observed in the aged 3–5% Al alloys in accordance with previous studies in literature performed at a similar aging temperature. Though no transformation was detected after DSC cycling down to −60 °C for the aged 4% and 5% Al alloys, mechanical testing confirmed pseudoelasticity. Additionally, TEM and atom probe analysis confirmed that aging at 600 °C resulted in precipitation of the Ni{sub 2}TiAl Heusler phase and determined the Al solubility limit in the matrix as near 3 at.%. Lastly, precipitation strengthening by the Heusler phase was observed when comparing the solution-treated and aged 4% and 5% Al alloys. Microstructural evolution was further characterized using XRD, SEM and compression testing.

  5. Plasma BDNF Is Reduced among Middle-Aged and Elderly Women with Impaired Insulin Function: Evidence of a Compensatory Mechanism

    Arentoft, Alyssa; Sweat, Victoria; Starr, Vanessa; Oliver, Stephen; Hassenstab, Jason; Bruehl, Hannah; Tirsi, Aziz; Javier, Elizabeth; McHugh, Pauline F.; Convit, Antonio

    2009-01-01

    Brain-derived neurotrophic factor (BDNF) plays a regulatory role in neuronal differentiation and synaptic plasticity and has been linked to glucose regulation and cognition. Associations among plasma BDNF, cognition, and insulin function were explored. Forty-one participants with impaired insulin function (IIF), ranging from insulin resistance to…

  6. A Paradigm for Investigating Executive Control Mechanisms in Word Retrieval in Language-Impaired and Neurotypical Speakers

    Erica L. Middleton

    2014-04-01

    Full Text Available An unresolved question in research on executive control in language production is whether the processes responsible for inhibiting a dominant, prepotent response in order to comply with task goals is the same or different from control processes that bias intrinsic competition during lexical selection. Heretofore, these processes have been studied with different paradigms, such as the Stroop task and semantic blocking paradigm [1], respectively. The present study introduces a new paradigm to study both mechanisms as they impact word retrieval in neuropsychological and neurotypical populations. The task included several blocks of trials, where within a block two pictures were named repeatedly in random order. Two manipulated factors were: (1 relatedness of the pair of names, which bore either a semantic (duck/pig or phonological relationship (ball/bag; or were unrelated (map/gun; (2 canonicity, where participants named each picture either with the canonical name (e.g., say “pig” for pig, “duck” for duck or reversed the labels (e.g., say “duck” for pig, “pig” for duck. The names were closely matched for length, frequency, and other variables. Crossing the factors created six conditions (semantic-canonical, semantic-reverse, phonological-canonical, phonological-reverse, unrelated-canonical, unrelated-reverse, with each condition administered in one block of 16 trials (8 trials per picture. The task was administered to 12 participants with aphasia (PWA with mild to severe naming impairment and 25 neurotypical controls. The dependent variables were naming latency (calculated for correct naming trials only and naming accuracy, defined as a binary variable (correct versus error, which were analyzed with mixed linear and logistic regression analysis, respectively. For each dependent variable in each participant group, contrasting each related condition with the unrelated condition permitted measurement of three effects--a main effect of

  7. Rapid and reversible impairments of short- and long-term social recognition memory are caused by acute isolation of adult rats via distinct mechanisms.

    Hadar Shahar-Gold

    Full Text Available Mammalian social organizations require the ability to recognize and remember individual conspecifics. This social recognition memory (SRM can be examined in rodents using their innate tendency to investigate novel conspecifics more persistently than familiar ones. Here we used the SRM paradigm to examine the influence of housing conditions on the social memory of adult rats. We found that acute social isolation caused within few days a significant impairment in acquisition of short-term SRM of male and female rats. Moreover, SRM consolidation into long-term memory was blocked following only one day of social isolation. Both impairments were reversible, but with different time courses. Furthermore, only the impairment in SRM consolidation was reversed by systemic administration of arginine-vasopressin (AVP. In contrast to SRM, object recognition memory was not affected by social isolation. We conclude that acute social isolation rapidly induces reversible changes in the brain neuronal and molecular mechanisms underlying SRM, which hamper its acquisition and completely block its consolidation. These changes occur via distinct, AVP sensitive and insensitive mechanisms. Thus, acute social isolation of rats swiftly causes changes in their brain and interferes with their normal social behavior.

  8. Effect of the Addition MgO Nano Particle to Mechanical Properties and Microstructure of ZTA Ceramic Composite

    The mechanical properties and microstructure of zirconia-toughened alumina ceramic composite doped with nano particle of MgO is investigated. The nano-MgO weight percent was varied from 0 wt% to 1.3 wt%. Each batch of composition was mixed using ultrasonic cleaning and mechanical stirrer, uniaxially pressed and sintered at 1600 degree Celsius for 4 h in pressureless conditions. Analysis of bulk density, Vickers hardness, fracture toughness and microstructural observation has been carried out. Results of Vickers hardness increased linearly with addition of more nano-MgO until a certain composition. Maximum Vickers hardness obtained was 1740HV with 1.1 wt % MgO. (author)

  9. Mechanical degradation under hydrogen of yttrium doped barium zirconate electrolyte material prepared with NiO additive

    Ciria, D.; Ben Hassine, M.; Jiménez-Melendo, M.; Iakovleva, A.; Haghi-Ashtiani, P.; Aubin, V.; Dezanneau, G.

    2016-07-01

    Recently, a novel process was presented to fabricate dense yttrium-doped barium zirconate electrolytes with high proton conductivity. This process was based on the use of a NiO additive during reactive sintering. We show here that materials made from this process present a fast degradation of mechanical properties when put in hydrogen-rich conditions, while material made from conventional sintering without NiO aid remains intact in the same conditions. The fast degradation of samples made from reactive sintering, leading to sample failure under highly compressive conditions, is due to the reduction of NiO nanoparticles at grain boundaries as shown from structural and chemical analyses using Transmission Electron Microscopy. By the present study, we alert about the potential risk of cell failure due to this mechanical degradation.

  10. Effect of Si addition on glass-forming ability and mechanical properties of Cu-Zr-Al bulk metallic glass

    Research highlights: The Cu50Zr43Al7 alloy has a surprising GFA, and the glassy rods with diameter of 10 mm have been produced in this research. It has not been reported that the Cu-based glassy rods (Cu ≥ 50 at.%) to be produced with the critical diameter greater than 10 mm. The novelty of this research is that the glass formation has been improved and the critical diameter increased to 12 mm for the alloy having x = 1 with the addition of Si. Different criteria are used to evaluate the influence of Si content on the GFA, and the possible mechanisms involved in the achievement of this GFA are also discussed. - Abstract: The effect of Si addition on the glass-forming ability (GFA) and mechanical properties of (Cu50Zr43Al7)100-xSix (x = 0, 0.5, 1, 1.5 and 2 at.%) alloys were investigated. The GFA of Cu50Zr43Al7 alloy is improved by addition of a small amount of Si, and the critical diameter for glass formation increases from 10 mm for the alloy with x = 0-12 mm for the alloy with x = 1 when prepared using copper mold casting. Different criteria are used to evaluate the influence of Si content on the GFA, and the possible mechanisms involved in the achievement of this GFA are also discussed. In the uniaxial compression, the bulk glassy alloys exhibit a limited plastic strain of less than 1%, but the compressive fracture strength and Young's modulus were obtained in high values of 1969-2129 MPa and 101-144 GPa, respectively. Fracture surface and shear bands of samples were studied by using scanning electron microscopy (SEM).