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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

    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.

  4. 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

  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. 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.

  7. 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

  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. 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

  14. 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

  15. 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

  16. 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…

  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. 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...

  13. 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

  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

    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.

  1. 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

  2. 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.

  3. 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.

  4. 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…

  5. 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

  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. 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

  9. 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

  10. 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…

  11. 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.

  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. 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.))

  15. 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.))

  16. 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.

  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. 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.

  5. 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.

  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. 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...

  8. 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...

  9. 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.

  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. 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.

  12. 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)

  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. 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...

  18. 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.

  19. 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.

  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. 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.

  4. 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.

  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. 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.

  9. 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.

  10. 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.

  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. 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).

  13. 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.

  14. 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.

  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

    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

    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.

  1. 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

  2. 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

  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. 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

  8. 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.

  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. 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.

  12. 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.

  13. 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%.

  14. 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.

  15. 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.

  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. 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.

  3. 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.

  4. 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.

  5. 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

  6. 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.

  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. 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

  16. 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

  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. 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...

  5. 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

  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. 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...

  10. 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

  11. 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.

  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. 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.

  5. 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...

  6. 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.

  7. 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...

  8. 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

  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. 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.

  11. 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

  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. 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.

  14. 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.

  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. 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)

  19. 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.

  20. 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)

  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. 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

  3. 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)

  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. 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.

  7. 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.

  8. 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...

  9. 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

  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. 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.

  18. 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...

  19. 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.

  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. 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.

  8. 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

  9. 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.

  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. 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

  14. 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

  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. 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.

  1. 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.

  2. 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

  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. 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)

  8. 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.

  9. 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.

  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).

  11. Etching characteristic and mechanism of BST thin films using inductively coupled Cl2/Ar plasma with additive CF4 gas

    BST thin films were etched with inductively coupled CF4/(Cl2+Ar) plasmas. The maximum etch rate of the BST thin films was 53.6 nm/min for a 10% CF4 to the Cl2/Ar gas mixture at RF power of 700 W, DC bias of -150 V, and chamber pressure of 2 Pa. Small addition of CF4 to the Cl2/Ar mixture increased chemical effect. Consequently, the increased chemical effect caused the increase in the etch rate of the BST thin films. To clarify the etching mechanism, the surface reaction of the BST thin films was investigated by X-ray photoelectron spectroscopy

  12. Crystallization, microstructure and mechanical properties of silumins with micro-additions of Cr, Mo, W and V

    S. Pietrowski

    2010-01-01

    Full Text Available In this paper results of the crystallization, microstructure and mechanical properties studies of hypo-, hyper- and eutectic silumins with addition of: Cr, Mo, W and V in amount of about 0,05% are presented. The influence of Sb, Sr and P together with Ti + B on the silumins crystallization process has been given. Results of: the microstructure, Rm, Rp0,2, A5 and HB testing of silumins after precipitation hardening and heat treatment in temperature of 560°C/3min and water chilling are presented.

  13. The Influence of Co Addition on Phase Transformation Behavior and Mechanical Properties of TiNi Alloys

    JING Rui-rui; LIU Fu-shun

    2007-01-01

    The influences of Co-addition on phase transformation behavior and mechanical properties of TiNi alloys were investigated. Results indicate that, as a substitute for Ni, Co added to TiNi alloys can dramatically decrease the martensite transformation temperature,and R phase transformation and martensite transformation are accordingly separated. When Co-content reach 10 at.%, the martensite transformation temperature is lower than that of liquid nitrogen. During deformation at room temperature, Ti50Ni48Co2 alloy exhibits good ductility with a lower stress plateau caused by stress-induced martensite and martensite reorientation.

  14. Enhancement of the Thermal Stability and Mechanical Hardness of Zr-Al-Co Amorphous Alloys by Ag Addition

    Wang, Yongyong; Dong, Xiao; Song, Xiaohui; Wang, Jinfeng; Li, Gong; Liu, Riping

    2016-05-01

    The thermal and mechanical properties of Zr57Al15Co28- X Ag X ( X = 0 and 8) amorphous alloys were investigated using differential scanning calorimetry, in situ high-pressure angle dispersive X-ray diffraction measurements with synchrotron radiation, and nanoindentation. Results show that Ag doping improves effective activation energy, nanohardness, elastic modulus, and bulk modulus. Ag addition enhances topological and chemical short-range orderings, which can improve local packing efficiency and restrain long-range atom diffusion. This approach has implications for the design of the microstructure- and property-controllable functional materials for various applications.

  15. Theoretical study on the reaction mechanism of ozone addition to the double bonds of keto-limonene

    Lei Jiang; Yisheng Xu; Baohui Yin; Zhipeng Bai

    2012-01-01

    The reaction mechanism of ozone (O3) addition to the double bonds of gas phase keto-limonene was investigated using ab initio methods.Two different possibilities for O3 addition to the double bond were considered and two corresponding van der Waais complexes (Complex 1 and Complex 2) were found for 1-endo and 2-endo.The rate constants were calculated using the transition state theory at the CCSD(T)/6-31G(d) + CF//B3LYP/6-31G(d,p) level.The high-pressure limit of the total rate constant at 298 K was 3.51 × 10-16cm3/(molecule.sec),which was in a good agreement with the experimental data.

  16. Effect of Y2O3 and Total Oxide Addition on Mechanical Properties of Pressureless Sintered β-SiC

    2003-01-01

    The effect of Y2O3 and the total oxide volume fraction (Y2O3+Al2O3) on density and mechanical properties of lowtemperature (1770~1940℃) pressureless sintered β-SiC ceramics were presented. The optimum temperature forpressureless sintering of β-SiC was found to be ~1850℃ and the optimum content of Y2O3 in the oxides was foundto be between 40 and 57 wt pct. The highest sintered density was achieved by adding oxides at 14 vol. pct. Both ofthe highest strength and fracture toughness were achieved at ~14 vol. pct oxide addition and yttria concentrationsbetween 40 and 57 wt pct in the oxides. Hardness, on the other hand, was found to be the highest for samples with14 vol. pct oxide addition and ~64 wt pct Y2O3 in oxides.

  17. A Critical Review of Screening and Diagnostic Instruments for Autism Spectrum Disorders in People with Sensory Impairments in Addition to Intellectual Disabilities

    de Vaan, Gitta; Vervloed, Mathijs P. J.; Hoevenaars-van den Boom, Marella; Antonissen, Anneke; Knoors, Harry; Verhoeven, Ludo

    2016-01-01

    Instruments that are used for diagnosing of, or screening for, autism spectrum disorder (ASD) may not be applicable to people with sensory disabilities in addition to intellectual disabilities. First, because they do not account for equifinality, the possibility that different conditions may lead to the same outcome. Second, because they do not…

  18. Low temperature impact toughness and fracture mechanism of cast QT400-18L ductile iron with different Ni additions

    Zhang Xinning

    2013-09-01

    Full Text Available Different contents of Ni (0.3wt.% to 1.2wt.% were added to the QT400-18L ductile iron to investigate the effect of Ni addition on the impact toughness of cast ductile irons at low temperatures. The impact toughnesses of the samples at room and low temperatures were tested. The microstructures and fractographs were observed. Results show that with the increase of Ni addition there is a general trend of refinement of the ferrite matrix while the nodule density shows no obvious change. When the Ni content is 0.7wt.%, the matrix structure is the refined ferrite with a very small fraction (about 2% of pearlite near the eutectic cell boundaries. When the Ni content is further increased, the fraction of pearlite increases significantly and reaches more than 5% when 1.2wt.% Ni is added. The impact toughness at room temperature increases as the content of Ni increases from 0.3 wt.% to 0.7 wt.%, but decreases as the Ni content further increases to 1.2wt.% due to the increase of pearlite fraction. The maximum value of the impact work is 18.5 J at room temperature with 0.7wt.% Ni addition. The average value of the impact work is still more than 13 J even at -30 ℃. In addition, the fracture mechanism changes from ductile manner to brittleness as the testing temperature decreases from 20 ℃ to -60 ℃.

  19. Effects of Ce addition on microstructure, mechanical properties and corrosion resistance of as-cast AZ80 magnesium alloy

    Wang Wei

    2014-05-01

    Full Text Available In this study, Ce was introduced into the AZ80 alloy and the effects of Ce addition on the microstructure, mechanical properties and corrosion resistance of the as-cast AZ80 magnesium alloy were investigated. The results show that the addition of Ce into the AZ80 alloy can not only refine the microstructure, but also result in the formation of the needle-like Al4Ce phase. These tiny Al4Ce phases are homogeneously distributed at grain boundaries and within grains. An appropriate Ce addition can also change the β-Mg17Al12 phase at the grain boundaries from continuous network to small island-like. At the same time, with the increase of Ce content from 0 to 2.0wt.%, the macro-hardness of the as-cast alloy is enhanced linearly, while impact toughness, tensile strength and elongation all firstly increase and then decrease. The AZ80 alloy containing 1.0wt.% Ce exhibits the optimal properties. Its macro-hardness, impact toughness, tensile strength and elongation are 61.90 HB, 15.50 J·cm-2, 171.80 MPa and 3.35%, increase by 9.95%, 63%, 13.3% and 36.7%, respectively compared with the base alloy. In addition, Ce can enhance the corrosion resistance of the AZ80 magnesium alloy.

  20. Influencing mechanism of Zn interlayer addition on hook defects of friction stir spot welded Mg–Al–Zn alloy joints

    Highlights: • Mg–Al–Zn sheets were friction stir spot welded (FSSW) with addition of Zn interlayer. • Complex alloying reactions occurred between Mg sheets and Zn interlayer during FSSW. • Alloying reactions increased the area of bonded zone and eliminated the hook defects. • Tensile–shear load of FSSW joints increased from 2.4 to 4 kN by adding Zn interlayer. - Abstract: 2.4 mm thick Mg–Al–Zn alloy sheets were friction stir spot welded (FSSW) without and with the addition of 0.1 mm thick Zn interlayer. The influence of interlayer addition on the microstructural features and mechanical properties of FSSW joints was investigated by optical microscope, scanning electron microscope, transmission electron microscope, X-ray diffraction and tensile testing. The results show that the addition of Zn interlayer resulted in complex alloying reactions between Mg substrate and Zn interlayer, forming a bonded zone composed of α-Mg, (α-Mg + MgZn) eutectoid structure and a mixture of Mg4Zn7 and unreacted Zn, thereby increasing the area of bonded zone and reducing the hook defects. This results in a significant increase in tensile–shear load from 2.4 kN to about 4 kN

  1. Effect of Grain and Calcinations Kaolin Additives on Some Mechanical and Physical properties on Low DensityPolyethylene Composites

    Zanaib Y. Shnean

    2008-01-01

    Full Text Available In this work, a composite material was prepared from Low-density polyethylene (LDPE with different weight percent of grain and calcinations kaolin at temperature of (850oC using single screw extruder and a mixing machine operated at a temperature between (190-200oC. Some of mechanical and physical properties such as tensile strength, tensile strength at break, Young modulus, and elongation at break, shore hardness and water absorption were determined at different weight fraction of filler (0, 2, 7, 10 and 15%. It was found that the addition of filler increases the modulus of elasticity, elongation at break, shore hardness and impact strength; on other hand, it decreases the tensile strength and tensile strength at a break. Absorption test was carried out in water at different immersion times and different composite .The results of absorption show that it obeys Fick’s law and after the addition of kaolin the amount of absorption decrease. Calcinations kaolin filler produces better mechanical properties , than grain kaolin fillers.

  2. Effect of boron addition on microstructure and mechanical properties of TiC/Ti6Al4V composites

    Highlights: ► TiC/Ti6Al4V composites were fabricated by using the in situ melting–casting process. ► The microstructure and mechanical properties of the composites were investigated. ► It showed the addition of boron refined the TiC dendrite and influenced the mechanical properties. ► The reasons of refinement of TiC dendrite and change of wear property were explained. -- Abstract: TiC/Ti6Al4V composites with different boron additions were successfully fabricated, and the effects of the boron content on the microstructure, mechanical properties of composites were investigated. The results show that the dendritic TiC in the composites is remarkably refined when the boron content is less than 0.06 wt.%. The average primary axial length of TiC dendrite is decreased from 150 μm to 50 μm according to the increasing of the boron content from 0.01 wt.% to 0.06 wt.%. And TiC dendrite gradually changes from the coarse dendrite to the fine dendrite or granular, but the abrasive property is obviously reduced with the increase of boron content. On the other hand, when the boron content further increases from 0.1 wt.% to 0.6 wt.%, the dendritic TiC can not be refined obviously, the fiber-shape TiB begins to appear and the abrasive property of composites is improved. The compressive strength and hardness (HRC) of composites are obviously increased in the whole addition range. The refinement mechanism of boron is attributed to the combined effects of the increase in nucleation rate at the constitutionally supercooled zone in front of the solid–liquid interface and the reduction in growth rate of TiC. The improvement of its abrasive property is mainly attributed to the existence of large size TiC and fiber-shape TiB during the abrasion.

  3. Effect of additive particles on mechanical, thermal, and cell functioning properties of poly(methyl methacrylate cement

    Khandaker M

    2014-05-01

    Full Text Available Morshed Khandaker,1 Melville B Vaughan,2 Tracy L Morris,3 Jeremiah J White,1 Zhaotong Meng1 1Department of Engineering and Physics, 2Department of Biology, 3Department of Mathematics and Statistics, University of Central Oklahoma, Edmond, OK, USA Abstract: The most common bone cement material used clinically today for orthopedic surgery is poly(methyl methacrylate (PMMA. Conventional PMMA bone cement has several mechanical, thermal, and biological disadvantages. To overcome these problems, researchers have investigated combinations of PMMA bone cement and several bioactive particles (micrometers to nanometers in size, such as magnesium oxide, hydroxyapatite, chitosan, barium sulfate, and silica. A study comparing the effect of these individual additives on the mechanical, thermal, and cell functional properties of PMMA would be important to enable selection of suitable additives and design improved PMMA cement for orthopedic applications. Therefore, the goal of this study was to determine the effect of inclusion of magnesium oxide, hydroxyapatite, chitosan, barium sulfate, and silica additives in PMMA on the mechanical, thermal, and cell functional performance of PMMA. American Society for Testing and Materials standard three-point bend flexural and fracture tests were conducted to determine the flexural strength, flexural modulus, and fracture toughness of the different PMMA samples. A custom-made temperature measurement system was used to determine maximum curing temperature and the time needed for each PMMA sample to reach its maximum curing temperature. Osteoblast adhesion and proliferation experiments were performed to determine cell viability using the different PMMA cements. We found that flexural strength and fracture toughness were significantly greater for PMMA specimens that incorporated silica than for the other specimens. All additives prolonged the time taken to reach maximum curing temperature and significantly improved cell

  4. The effect of Si additions on the sintering and sintered microstructure and mechanical properties of Ti-3Ni alloy

    Highlights: → Silicon is a potent sintering aid for Ti-Ni alloys revealed by predictions and confirmed by experiments. → The addition of Si should be limited to ≤1% to avoid coarse Ti5Si3 phase and ensure good ductility. → Liquid forms during heating at ∼988 deg. C due to reactions between Si and Ni and Ni and Ti. → Silicon can be a unique addition to PM Ti alloys for significantly improved mechanical properties. - Abstract: Thermodynamic predictions suggest that silicon has the potential to be a potent sintering aid for Ti-Ni alloys because small additions of Si lower the solidus of Ti-Ni alloys appreciably (>200 deg. C by 1 wt.% Si). A systematic study has been made of the effect of Si on the sintering of a Ti-3Ni alloy at 1300 deg. C. The sintered density increased from 91.8% theoretical density (TD) to 99.2%TD with increasing Si from 0% to 2%. Microstructural examination reveals that coarse particles and/or continuous networks of Ti5Si3 form along grain boundaries when the addition of Si exceeds 1%. The grain boundary Ti5Si3 phase leads to predominantly intergranular fracture and therefore a sharp decrease in ductility concomitant with increased tensile strengths. The optimum addition of Si is proposed to be ≤1%. Dilatometry experiments reveal different shrinkage behaviours with respect to different Si contents. Interrupted differential scanning calorimetry (DSC) experiments and corresponding X-ray diffraction (XRD) analyses clarify the sequence of phase formation during heating. The results provide a useful basis for powder metallurgy (PM) Ti alloy design with Si.

  5. Review of Mechanical Properties of Ti-6Al-4V Made by Laser-Based Additive Manufacturing Using Powder Feedstock

    Beese, Allison M.; Carroll, Beth E.

    2016-03-01

    Laser-based additive manufacturing (AM) of metals using powder feedstock can be accomplished via two broadly defined technologies: directed energy deposition (DED) and powder bed fusion (PBF). In these processes, metallic powder is delivered to a location and locally melted with a laser heat source. Upon deposition, the material undergoes a rapid cooling and solidification, and as subsequent layers are added to the component, the material within the component is subjected to rapid thermal cycles. In order to adopt AM for the building of structural components, a thorough understanding of the relationships among the complex thermal cycles seen in AM, the unique heterogeneous and anisotropic microstructure, and the mechanical properties must be developed. Researchers have fabricated components by both DED and PBF from the widely used titanium alloy Ti-6Al-4V and studied the resultant microstructure and mechanical properties. This review article discusses the progress to date on investigating the as-deposited and heat-treated microstructures and mechanical properties of Ti-6Al-4V structures made by powder-based laser AM using DED and PBF.

  6. The effect of unsaturated fatty acid and triglyceride oil addition on the mechanical and antibacterial properties of acrylic bone cements.

    Persson, Cecilia; Robert, Elise; Carlsson, Elin; Robo, Céline; López, Alejandro; Godoy-Gallardo, Maria; Ginebra, Maria-Pau; Engqvist, Håkan

    2015-09-01

    Acrylic bone cements have an elastic modulus several times higher than the surrounding trabecular bone. This has been hypothesized to contribute to certain clinical complications. There are indications that the addition of specific fatty acids and triglyceride oils may reduce the elastic modulus of these types of cements. Some of these additives also appear to have inherent antibiotic properties, although this has never been evaluated in bone cements. In this study, several types of fatty acids and triglyceride oils were evaluated for use in acrylic bone cements. Their mechanical properties were evaluated under uniaxial compression testing and selected cements were then further characterized in terms of microstructure, handling and antibacterial properties using scanning electron microscopy, polymerization temperature measurements, agar diffusion tests and bactericidal activity assays of cement extracts. It was found that any of the evaluated fatty acids or triglyceride oils could be used to tailor the stiffness of acrylic bone cements, although at varying concentrations, which also depended on the type of commercial base cement used. In particular, the addition of very small amounts of linoleic acid (agar diffusion test as well as demonstrating 100% bactericidal activity against the same strain. PMID:25876889

  7. Synthesis of nanoparticeles in ductile iron with small additions of vanadium and niobium and its mechanical properties

    E. Fraś

    2007-12-01

    Full Text Available It has been shown that the heat treatment of 1095oC/640 oC type of ferritic ductile iron with small addition of 0.08% vanadium permits to obtain of the rounded VC nanoparticles with an average size of 50 nm and 0.13 volume fraction. Results of investigations of influence of small vanadium up to 0.3%, niobium up to 0.16% and nitrogen up to 58 ppm additions and heat treatment of 1080oC-24h/640 oC and 1080oC-24h/600 oC type on structure and mechanical properties (tensile strength, yields strength and elongation of ductile iron are also presented in this work. It has been demonstrated that heat treatment and small additions of vanadium, and niobium as well as nitrogen enable to obtain material, which can be classified a EN-GJS-450-18 to EN-GJS-700-2 grade ductile iron.

  8. Duchenne型肌营养不良认知障碍机制研究进展%Mechanisms of Cognitive Impairment of Duchenne's Muscular Dystrophy (review)

    付雅; 吴士文

    2014-01-01

    Duchenne型肌营养不良是一种常见的X染色体连锁隐性遗传神经肌肉病,并常伴有认知障碍。目前关于其认知障碍机制研究较多,主要集中在抗肌萎缩蛋白亚型缺乏、中枢神经系统发育异常、突触功能改变、血脑屏障改变、大脑代谢改变及小脑功能异常等。%Duchenne's muscular dystrophy (DMD) is a common X-linked recessive neuromuscular disorder that associated with a spec-trum of genetically based cognitive and behavioral disabilities. Several mechanisms have been discussed as the cause of cognitive impair-ment in patients with DMD: absence of different dystrophin isoforms, impairments in neurogenesis, changes of synaptic plasticity, blood-brain barrier alterations, brain metabolic differences, cerebellum disfunction, etc.

  9. The Effect of the Kind of Sands and Additions on the Mechanical Behaviour of S.C.C

    Zeghichi, L.; Benghazi, Z.; Baali, L.

    The sand is an inert element essential in the composition of concrete; its use ensures granular continuity between the cement and gravel for better cohesion of concrete. This paper presents the results of a study that investigated the influence of sand quality on the properties of fresh and hardened self-compacting concrete (SCC). The dune sands are very fine materials characterized by a high intergranular porosity, high surface area and low fineness modulus; on the other hand crushed (manufactured) sand has a high rate into thin and irregular shapes which are influencing the workability of concrete. The amount of dune sand varies from (0% 50%, to 100%) by weight of fine aggregates. The effect of additions is also treated (blast furnace slag and lime stone) The results show that the rheological properties favour the use of dune sands; however the mechanical properties support the use of crushed sand.

  10. Effect of Nb addition on the microstructure and mechanical properties of an 1800 MPa ultrahigh strength steel

    Wu, Huibin [National Engineering Research Center for Advanced Rolling Technology, University of Science and Technology Beijing, Beijing 100083 (China); Ju, Biao, E-mail: jubiao@aliyun.com [National Engineering Research Center for Advanced Rolling Technology, University of Science and Technology Beijing, Beijing 100083 (China); Tang, Di; Hu, Rirong [National Engineering Research Center for Advanced Rolling Technology, University of Science and Technology Beijing, Beijing 100083 (China); Guo, Aimin [CITIC-CBMM Microalloying Technology Center (MTC), CITIC Group, Beijing 100004 (China); Kang, Qiang; Wang, Di [National Engineering Research Center for Advanced Rolling Technology, University of Science and Technology Beijing, Beijing 100083 (China)

    2015-01-12

    The microstructure–property relationship of Nb-free and Nb-bearing ultrahigh strength steels were studied in this work. Martensitic steels with 1800 MPa tensile strength were obtained by conducting reheated quenching and tempering after thermomechanical rolling. The microstructures of the steels were investigated by scanning electron microscopy, transmission electron microscopy electron backscattering diffraction technique. The results show that with the addition of Nb, the prior austenite grain growth was impeded, which leaded to the further refinement of final martensite microstructure. Randomly distributed Nb-rich (Nb,Ti)C in Nb bearing steel played an important role in the strengthening of the steel. As revealed by dilatometry and differential scanning calorimetry, with the increase of tempering temperature the decrease of mechanical properties mainly initiated by the decomposition of retained austenite during low temperature tempering, and the formation of harmful iron carbides was retarded when the steel microalloyed with 0.021% Nb.

  11. Mechanical properties of pressure-less sintered ZrB{sub 2} with molybdenum, iron and carbon additives

    Mousavi, Mahsa Jalal, E-mail: Mahsa_mousavi62@yahoo.com [Ceramic Department, Imam Khomeini International University, P. O. Box: 34149-16818, Ghazvin (Iran, Islamic Republic of); Zakeri, Mohammad; Rahimipour, Mohammadreza [Ceramic Department, Materials and Energy Research Center, Karaj (Iran, Islamic Republic of); Amini, Elham [Ceramic Department, Imam Khomeini International University, P. O. Box: 34149-16818, Ghazvin (Iran, Islamic Republic of)

    2014-09-08

    ZrB{sub 2} powder was successfully densified with Mo, Fe and carbon as sintering aid by pressure-less sintering method. Effects of the above additives were investigated on the densification, microstructure and mechanical properties (hardness, fracture toughness and compressive strength) of sintered samples. It was observed that the ZrB{sub 2} samples with 10 wt%Fe and 15 wt%Mo with 1 wt%C had the maximum density. The maximum compressive strength and fracture toughness of 425 MPa and 12.5 MPa m{sup 1/2} were obtained for ZrB{sub 2}–10 wt%Mo–1 wt%C, respectively. Fracture toughness of ZrB{sub 2}–10 wt%Fe was significantly improved at higher carbon content (2 wt%)

  12. Effects of microstructure and CaO addition on the magnetic and mechanical properties of NiCuZn ferrites

    In this study, the effects of grain size and the addition of CaCO3 on the magnetic and mechanical properties of Ni0.5Cu0.3Zn0.2Fe2O4 ceramics were investigated. The bending strength of the ferrites increased from 66 to 84 MPa as the grain size of the sintered ceramics decreased from 10.25 μm to 7.53 μm, while the change in hardness was insignificant. The addition of various amounts of CaCO3 densified the Ni0.5Cu0.3Zn0.2Fe2O4 ceramics at 1075 °C. In the pure Ni0.5Cu0.3Zn0.2Fe2O4 ceramic, second phase CuO was segregated at the grain boundaries. With the CaCO3 content ≥1.5 wt%, a small amount of discrete plate-like second phase Fe2CaO4 was observed, together with the disappearance of the second phase CuO. The grain size of the Ni0.5Cu0.3Zn0.2Fe2O4 ceramic dropped from 7.80 μm to 4.68 μm, and the grain size distribution widened as the CaCO3 content increased from 0 to 5 wt%. Initially rising to 807 after CaCO3 addition up to 2.0 wt%, due to a reduced grain size, the Vickers hardness began to drop as the CaCO3 content increased. The bending strength grew linearly with the CaCO3 content and reached twice the value for the Ni0.5Cu0.3Zn0.2Fe2O4 ceramic with an addition of 5.0 wt% CaCO3. The initial permeability of the Ni0.5Cu0.3Zn0.2Fe2O4 ceramic decreased substantially from 402 to 103 as the addition of CaCO3 in ferrite increased from 0 to 5 wt%, and the quality factor of the Ni0.5Cu0.3Zn0.2Fe2O4 ceramic was maximized at 95 for 1.0 wt% CaCO3 addition. - Highlights: • Effects of grain size and CaCO3 on the properties of NiCuZn ferrite were studied. • Bending strength increased with grain size of the ferrite but not in the hardness. • Bending strength reached a twice value for ferrite with 5.0 wt% CaCO3 addition. • Initial permeability of the ferrite decreased markedly with the addition of CaCO3. • Quality factor of the ferrite was maximized at 95 for 1.0 wt% CaCO3 addition

  13. Effects of microstructure and CaO addition on the magnetic and mechanical properties of NiCuZn ferrites

    Wang, Sea-Fue, E-mail: sfwang@ntut.edu.tw; Hsu, Yung-Fu; Liu, Yi-Xin; Hsieh, Chung-Kai

    2015-11-15

    In this study, the effects of grain size and the addition of CaCO{sub 3} on the magnetic and mechanical properties of Ni{sub 0.5}Cu{sub 0.3}Zn{sub 0.2}Fe{sub 2}O{sub 4} ceramics were investigated. The bending strength of the ferrites increased from 66 to 84 MPa as the grain size of the sintered ceramics decreased from 10.25 μm to 7.53 μm, while the change in hardness was insignificant. The addition of various amounts of CaCO{sub 3} densified the Ni{sub 0.5}Cu{sub 0.3}Zn{sub 0.2}Fe{sub 2}O{sub 4} ceramics at 1075 °C. In the pure Ni{sub 0.5}Cu{sub 0.3}Zn{sub 0.2}Fe{sub 2}O{sub 4} ceramic, second phase CuO was segregated at the grain boundaries. With the CaCO{sub 3} content ≥1.5 wt%, a small amount of discrete plate-like second phase Fe{sub 2}CaO{sub 4} was observed, together with the disappearance of the second phase CuO. The grain size of the Ni{sub 0.5}Cu{sub 0.3}Zn{sub 0.2}Fe{sub 2}O{sub 4} ceramic dropped from 7.80 μm to 4.68 μm, and the grain size distribution widened as the CaCO{sub 3} content increased from 0 to 5 wt%. Initially rising to 807 after CaCO{sub 3} addition up to 2.0 wt%, due to a reduced grain size, the Vickers hardness began to drop as the CaCO{sub 3} content increased. The bending strength grew linearly with the CaCO{sub 3} content and reached twice the value for the Ni{sub 0.5}Cu{sub 0.3}Zn{sub 0.2}Fe{sub 2}O{sub 4} ceramic with an addition of 5.0 wt% CaCO{sub 3}. The initial permeability of the Ni{sub 0.5}Cu{sub 0.3}Zn{sub 0.2}Fe{sub 2}O{sub 4} ceramic decreased substantially from 402 to 103 as the addition of CaCO{sub 3} in ferrite increased from 0 to 5 wt%, and the quality factor of the Ni{sub 0.5}Cu{sub 0.3}Zn{sub 0.2}Fe{sub 2}O{sub 4} ceramic was maximized at 95 for 1.0 wt% CaCO{sub 3} addition. - Highlights: • Effects of grain size and CaCO{sub 3} on the properties of NiCuZn ferrite were studied. • Bending strength increased with grain size of the ferrite but not in the hardness. • Bending strength reached a twice value for

  14. Effect of addition of Ag nano powder on mechanical properties of epoxy/polyaminoamide adduct coatings filled with conducting polymer

    Samad, Ubair Abdus [Department of Chemical Engineering, College of Engineering, King Saud University, P. O. Box 800, Riyadh 11421 (Saudi Arabia); Center of excellence for research in engineering materials (CEREM), Advance Manufacturing Institute, King Saud University, P. O. Box 800, Riyadh 11421 (Saudi Arabia); Khan, Rawaiz [Department of Chemical Engineering, College of Engineering, King Saud University, P. O. Box 800, Riyadh 11421 (Saudi Arabia); Alam, Mohammad Asif [Center of excellence for research in engineering materials (CEREM), Advance Manufacturing Institute, King Saud University, P. O. Box 800, Riyadh 11421 (Saudi Arabia); Al-Othman, Othman Y. [Department of Chemical Engineering, College of Engineering, King Saud University, P. O. Box 800, Riyadh 11421 (Saudi Arabia); Deanship of Graduate Studies, The Saudi Electric University, P. O. Box 93499, Riyadh 11673 (Saudi Arabia); Al-Zahrani, Saeed M. [Center of excellence for research in engineering materials (CEREM), Advance Manufacturing Institute, King Saud University, P. O. Box 800, Riyadh 11421 (Saudi Arabia); SABIC Polymer Research Center (SPRC) and department of chemical engineering, college of engineering, King Saud University, P. O. Box 800, Riyadh 11421 (Saudi Arabia)

    2015-05-22

    In this study the effect of Ag Nano powder on mechanical properties of epoxy coatings filled with optimized ratio of conducting polymers (Polyaniline and Polyppyrole) was evaluated. Bisphenol A diglycidyl ether epoxy resin (DGEBA) along with polyaminoamide adduct (ARADUR 3282-1 BD) is used as curing agent under optimized stoichiometry values. Curing is performed at room temperature with different percentages of Nano filler. Glass and steel panels were used as coating substrate. Bird applicator was used to coat the samples in order to obtain thin film with wet film thickness (WFT) of about 70-90 µm. The samples were kept in dust free environment for about 7 days at room temperature for complete curing. The coated steel panels were used to evaluate the mechanical properties of coating such as hardness, scratch and impact tests whereas coated glass panels were used for measuring pendulum hardness of the coatings. To check the dispersion and morphology of Nano filler in epoxy matrix scanning electron microscopy (SEM) was used in addition Nano indentation was also performed to observe the effect of Nano filler on modulus of elasticity and hardness at Nano scale.

  15. Mechanical behaviour of austenitic stainless steels in inert environment and in hot chloride environment: influence of molybdenum addition

    This research thesis reports the study of the influence of molybdenum addition. It is based on an experimental method which brings to the fore correlations between mechanical and electrochemical parameters of the phenomenon of stress corrosion cracking of austenitic stainless steels. After having recalled some characteristics of dry corrosion and electrochemical corrosion, presented austenitic stainless steels (mechanical properties such as elastic modulus, yield strength, tensile strength, ultimate elongation, creep behaviour, inter-crystalline and pitting corrosion, stress corrosion cracking behaviour), the author addresses the stress corrosion cracking behaviour of these steels in chloride environment (general characteristics, parameters, proposes theories to explain stress corrosion cracking), reports the study of the influence of molybdenum in these steels, notably on corrosion resistance and on stress corrosion cracking. Experimental method and results are described and discussed: tensile tests and creep tests in inert environment, stress corrosion cracking test in chloride environment with analysis based either on corrosion potential evolution or on sample elongation evolution. Results are notably discussed in terms of crack situation within metal lattice, crack growth rate, and scanning electronic microscopy observations

  16. Unraveling the Fundamental Mechanisms of Solvent-Additive-Induced Optimization of Power Conversion Efficiencies in Organic Photovoltaic Devices.

    Herath, Nuradhika; Das, Sanjib; Zhu, Jiahua; Kumar, Rajeev; Chen, Jihua; Xiao, Kai; Gu, Gong; Browning, James F; Sumpter, Bobby G; Ivanov, Ilia N; Lauter, Valeria

    2016-08-10

    The realization of controllable morphologies of bulk heterojunctions (BHJ) in organic photovoltaics (OPVs) is one of the key factors enabling high-efficiency devices. We provide new insights into the fundamental mechanisms essential for the optimization of power conversion efficiencies (PCEs) with additive processing to PBDTTT-CF:PC71BM system. We have studied the underlying mechanisms by monitoring the 3D nanostructural modifications in BHJs and correlated the modifications with the optical analysis and theoretical modeling of charge transport. Our results demonstrate profound effects of diiodooctane (DIO) on morphology and charge transport in the active layers. For small amounts of DIO (3 vol %), DIO facilitates a loosely packed mixed morphology with large clusters of PC71BM, leading to deterioration in PCE. Theoretical modeling of charge transport reveals that DIO increases the mobility of electrons and holes (the charge carriers) by affecting the energetic disorder and electric field dependence of the mobility. Our findings show the implications of phase separation and carrier transport pathways to achieve optimal device performances. PMID:27403964

  17. The association of N-palmitoylethanolamine with the FAAH inhibitor URB597 impairs melanoma growth through a supra-additive action

    The incidence of melanoma is considerably increasing worldwide. Frequent failing of classical treatments led to development of novel therapeutic strategies aiming at managing advanced forms of this skin cancer. Additionally, the implication of the endocannabinoid system in malignancy is actively investigated. We investigated the cytotoxicity of endocannabinoids and their hydrolysis inhibitors on the murine B16 melanoma cell line using a MTT test. Enzyme and receptor expression was measured by RT-PCR and enzymatic degradation of endocannabinoids using radiolabeled substrates. Cell death was assessed by Annexin-V/Propidium iodine staining. Tumors were induced in C57BL/6 mice by s.c. flank injection of B16 melanoma cells. Mice were injected i.p. for six days with vehicle or treatment, and tumor size was measured each day and weighted at the end of the treatment. Haematoxylin-Eosin staining and TUNEL assay were performed to quantify necrosis and apoptosis in the tumor and endocannabinoid levels were quantified by HPLC-MS. Tube formation assay and CD31 immunostaining were used to evaluate the antiangiogenic effects of the treatments. The N-arachidonoylethanolamine (anandamide, AEA), 2-arachidonoylglycerol and N- palmitoylethanolamine (PEA) reduced viability of B16 cells. The association of PEA with the fatty acid amide hydrolase (FAAH) inhibitor URB597 considerably reduced cell viability consequently to an inhibition of PEA hydrolysis and an increase of PEA levels. The increase of cell death observed with this combination of molecules was confirmed in vivo where only co-treatment with both PEA and URB597 led to decreased melanoma progression. The antiproliferative action of the treatment was associated with an elevation of PEA levels and larger necrotic regions in the tumor. This study suggests the interest of targeting the endocannabinoid system in the management of skin cancer and underlines the advantage of associating endocannabinoids with enzymatic hydrolysis

  18. Graded microstructure and mechanical properties of additive manufactured Ti–6Al–4V via electron beam melting

    Electron beam melting (EBM®)-built Ti–6Al–4V has increasingly shown great potential for orthopedic implant and aerospace applications in recent years. The microstructure and mechanical properties of EBM-built Ti–6Al–4V have been systematically investigated in this work. Its microstructure consists of columnar prior β grains delineated by wavy grain boundary α and transformed α/β structures with both cellular colony and basket-weave morphology as well as numerous singular α bulges within the prior β grains. The β phase is found to form as discrete flat rods embedded in continuous α phase and its volume fraction is determined to be ∼3.6%. Moreover, α′ martensite was not observed as it has decomposed into α and β phases. In particular, the α/β interface was studied in detail combined transmission electron microscopy with atom probe tomography. Of note is that graded Ti–6Al–4V microstructure i.e. both prior β grain width and β phase interspacing continuously increase with the build height, was observed, which mainly arises from the decreasing cooling rate. Furthermore, an increasingly pronounced strain hardening effect was also observed as the previously built layers undergo a longer annealing compared to the subsequent layers. As a result, graded mechanical properties of Ti–6Al–4V with degraded microhardness and tensile properties were found. A good agreement with the Hall–Petch relation indicates that the graded property takes place mainly due to the graded microstructure. In addition, this graded microstructure and mechanical properties were discussed based on a quantitative characterization

  19. Effects of Cu and B addition on microstructure and mechanical properties of high-strength bainitic steels

    Effects of Cu and B addition on microstructure and mechanical properties of high-strength bainitic steels were investigated in this study. Six kinds of steels were fabricated by controlling the amount of Cu and B addition, and their microstructures and tensile and Charpy impact properties were investigated. Their effective grain sizes were also characterized by the electron back-scatter diffraction analysis. The tensile test results indicated that the B- or Cu-containing steels had the higher yield and tensile strengths than the B- or Cu-free steels because their volume fractions of acicular ferrite and martensite were quite high. The B- or Cu-free steels had the higher upper shelf energy than the B- or Cu-containing steels because of their lower volume fraction of martensite. In the steel containing 10 ppm B without Cu, the best combination of high strengths, high upper shelf energy, and low energy transition temperature could be obtained by the decrease in effective grain size due to the presence of acicular ferrite having fine effective grain size.

  20. Effect of alloying additions to Ag on thermal conductivity, electrical and mechanical properties of Ag-sheathed Bi-2223 tapes

    Ag-sheathed Bi-2223 tapes were fabricated by a powder-in-tube technique with different configurations of the inner and outer sheath materials: Ag, Ag-Mg-Ni, Ag-Sb and Ag-Au. Characterization of thermal conductivity at 4.2 K to 100 K showed that the addition of Au decreased the thermal conductivity remarkably. The value at 40 K was 53.8 W/(m K) for AgAu-AgAu tape, five times lower than that of Ag-AgMgNi tape. The addition of Sb reduced AC losses much more than other alloyed element, partly due to its high electrical resistivity at 77 K. The measurement results of the normalized I c dependence on magnetic field of the tapes indicated, however, no conclusive correlation between alloy type and I c performance in field was highlighted. The mechanical property of alloy-sheathed tape was also evaluated. The sequence of the tapes' tensile strength from highest to lowest was: Ag-Mg-Ni, Ag-Sb, Ag-Au, Ag

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

    Jodi A. Carlson Scholz

    2012-12-01

    Full Text Available 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 or vehicle for four weeks. Both femurs from each rat were analyzed by X-ray and pQCT, then analyzed either by microCT, histology or biomechanical testing. Marrow ablation alone induced transient bone formation of low abundance that persisted over four weeks, while marrow ablation followed by PTH induced bone formation of high abundance that also persisted over four weeks. Our data confirms that the osteo-inducive effect of marrow ablation and the additive effect of marrow ablation, followed by PTH, occurs in aged rats. Our observations open new avenues of investigations in the field of tissue regeneration. Local marrow ablation, in conjunction with an anabolic agent, might provide a new platform for rapid site-directed bone growth in areas of high bone loss, such as in the hip and wrist, which are subject to fracture.

  2. Effect of boron addition on the microstructures and mechanical properties of thermomechanically processed and tempered low carbon bainitic steels

    Liangyun LAN; Chunlin QIU; Ping ZHOU; Dewen ZHAO; Canming LI; Xiuhua GAO; Linxiu DU

    2011-01-01

    Thermomechanical process and tempering heat treatment were employed to produce the experimental steel plates.The effect of boron addition on the microstructure and mechanical properties of low carbon bainitic steels was studied in this paper.Microstructure observation and crystallographic features were conducted by using optical microscopy,SEM,TEM and electron back scattering diffraction (EBSD) analysis.The results showed that under the same rolling processes and heat treatment conditions,a substantial increase in strength is obtained by addition of boron into steel,but accompanied by an obvious drop in toughness.New martensite phase forms along the grain boundaries on tempering at 650 ℃ mainly due to boron segregation,which can further deteriorate impact toughness of the boron bearing steel.The EBSD analysis showed that high angle grain boundary,is not responsible for the deteriorated toughness of the boron bearing steel because it has relatively higher percentage of high angle grain boundary than the boron free steel.The low toughness of the boron bearing steel is mainly attributed to the coarse boride precipitated particles according to the results of fractograph observation.

  3. Variation of mechanical properties with addition of Al in low activity ferritic/martensitic heat resistant steels

    The effect of aluminum on mechanical properties in low activation martensitic steel has been studied. Impact test and tensile test were performed at high temperature. Aluminum is in solid solution state after normalizing so the grain size of prior austenite was not changed. AlN was precipitated during tempering treatment. The size of Cr2N precipitates were decreased due to the precipitation of AlN in 0.10wt.%N steel. But the precipitation of nitride such as V(C,N) and Cr2N was suppressed by the formation of AlN in 0.08wt.%N steel. The addition of aluminum have little effect on the impact properties such as DBTT and upper shelf energy. The increase of tensile strength and yield strength by addition of aluminum appeared in 0.10wt.%N steel, but not in 0.08wt.%N steel. But the tensile and yield strength of aluminum added 0.10wt.%N steel is not higher than that of 0.08wt.%N steel

  4. Physiological, molecular, and cellular mechanisms of impaired seawater tolerance following exposure of Atlantic salmon, Salmo salar, smolts to acid and aluminum

    Monette, M.Y.; Yada, T.; Matey, V.; McCormick, S.D.

    2010-01-01

    We examined the physiological, molecular, and cellular mechanisms of impaired ion regulation in Atlantic salmon, Salmo salar, smolts following acute acid and aluminum (Al) exposure. Smolts were exposed to: control (pH 6.5, 3.4??gl-1 Al), acid and low Al (LAl: pH 5.4, 11??gl-1 Al), acid and moderate Al (MAl: pH 5.3, 42??gl-1 Al), and acid and high Al (HAl: pH 5.4, 56??gl-1 Al) for two and six days. At each time-point, smolts were sampled directly from freshwater treatment tanks and after a 24h seawater challenge. Exposure to acid/MAl and acid/HAl led to accumulation of gill Al, substantial alterations in gill morphology, reduced gill Na+/K+-ATPase (NKA) activity, and impaired ion regulation in both freshwater and seawater. Exposure to acid/MAl for six days also led to a decrease in gill mRNA expression of the apical Cl- channel (cystic fibrosis transmembrane conductance regulator I), increased apoptosis upon seawater exposure, an increase in the surface expression of mitochondria-rich cells (MRCs) within the filament epithelium of the gill, but reduced abundance of gill NKA-positive MRCs. By contrast, smolts exposed to acid and the lowest Al concentration exhibited minor gill Al accumulation, slight morphological modifications in the gill, and impaired seawater tolerance in the absence of a detectable effect on freshwater ion regulation. These impacts were accompanied by decreased cell proliferation, a slight increase in the surface expression of MRCs within the filament epithelium, but no impact on gill apoptosis or total MRC abundance was observed. However, MRCs in the gills of smolts exposed to acid/LAl exhibited morphological alterations including decreased size, staining intensity, and shape factor. We demonstrate that the seawater tolerance of Atlantic salmon smolts is extremely sensitive to acute exposure to acid and low levels of Al, and that the mechanisms underlying this depend on the time-course and severity of Al exposure. We propose that when smolts are

  5. Effects of Sc and Zr microalloying additions on the recrystallization texture and mechanism of Al–Zn–Mg alloys

    Highlights: •Investigate texture evolution of Al–Zn–Mg/Al–Zn–Mg–Sc–Zr alloys during annealing. •Discuss the recrystallization mechanisms of Al–Zn–Mg/Al–Zn–Mg–Sc–Zr alloys. •Establish a recrystallization nucleation model. •Calculate orientation-dependent stored energies. -- Abstract: Effects of Sc and Zr microalloying additions on the recrystallization texture and mechanism during annealing were investigated in detail by the methods of X-ray diffraction macrotexture measurements and electron backscattering diffraction local orientation observations in three kinds of Al–Zn–Mg cold rolled sheets (Al–Zn–Mg, Al–Zn–Mg–0.10 wt.%Sc–0.10 wt.%Zr and Al–Zn–Mg–0.25 wt.%Sc–0.10 wt.%Zr). The results show that the texture of the three cold rolled alloys all consists of cube and rolling orientations. During recrystallization annealing in the conventional Al–Zn–Mg alloy, rolling texture gradually weakens and finally disappears and cube texture is the dominant recrystallization texture. The nucleation mechanism of the Al–Zn–Mg alloy is cube nucleation. For Al–Zn–Mg–Sc–Zr alloys, with the increase of Sc and Zr contents and annealing temperatures, the intensity of rolling texture β-fiber increases. Rolling texture is dominant in the recrystallized Al–Zn–Mg–Sc–Zr alloy. The main microstructural features of the Al–Zn–Mg–Sc–Zr alloy during annealing are that lots of disperse, coherent and nano-scaled Al3(Sc, Zr) particles strongly pin dislocations and grain/sub-grain boundaries, inhibiting the occurrence of recovery and recrystallization. The microstructural observation results show that S and Brass orientations are the preferred nucleation orientations in the Al–Zn–Mg–Sc–Zr alloy. To calculate the orientation-dependent stored energies, a recrystallization nucleation model was established, based on a standard Read–Schockley equation. The calculated results show that S and Brass orientations

  6. Effects of Sc and Zr microalloying additions on the recrystallization texture and mechanism of Al–Zn–Mg alloys

    Deng, Ying, E-mail: csudengying@163.com; Xu, Guofu, E-mail: csuxgf66@mail.csu.edu.cn; Yin, Zhimin; Lei, Xuefeng; Huang, Jiwu

    2013-12-15

    Highlights: •Investigate texture evolution of Al–Zn–Mg/Al–Zn–Mg–Sc–Zr alloys during annealing. •Discuss the recrystallization mechanisms of Al–Zn–Mg/Al–Zn–Mg–Sc–Zr alloys. •Establish a recrystallization nucleation model. •Calculate orientation-dependent stored energies. -- Abstract: Effects of Sc and Zr microalloying additions on the recrystallization texture and mechanism during annealing were investigated in detail by the methods of X-ray diffraction macrotexture measurements and electron backscattering diffraction local orientation observations in three kinds of Al–Zn–Mg cold rolled sheets (Al–Zn–Mg, Al–Zn–Mg–0.10 wt.%Sc–0.10 wt.%Zr and Al–Zn–Mg–0.25 wt.%Sc–0.10 wt.%Zr). The results show that the texture of the three cold rolled alloys all consists of cube and rolling orientations. During recrystallization annealing in the conventional Al–Zn–Mg alloy, rolling texture gradually weakens and finally disappears and cube texture is the dominant recrystallization texture. The nucleation mechanism of the Al–Zn–Mg alloy is cube nucleation. For Al–Zn–Mg–Sc–Zr alloys, with the increase of Sc and Zr contents and annealing temperatures, the intensity of rolling texture β-fiber increases. Rolling texture is dominant in the recrystallized Al–Zn–Mg–Sc–Zr alloy. The main microstructural features of the Al–Zn–Mg–Sc–Zr alloy during annealing are that lots of disperse, coherent and nano-scaled Al{sub 3}(Sc, Zr) particles strongly pin dislocations and grain/sub-grain boundaries, inhibiting the occurrence of recovery and recrystallization. The microstructural observation results show that S and Brass orientations are the preferred nucleation orientations in the Al–Zn–Mg–Sc–Zr alloy. To calculate the orientation-dependent stored energies, a recrystallization nucleation model was established, based on a standard Read–Schockley equation. The calculated results show that S and Brass

  7. Delayed onset of tricuspid valve flow in repaired tetralogy of Fallot: an additional mechanism of diastolic dysfunction and interventricular dyssynchrony

    Benson Lee N

    2011-08-01

    Full Text Available Abstract Background Diastolic dysfunction of the right ventricle (RV is common after repair of tetralogy of Fallot. While restrictive physiology in late diastole has been well known, dysfunction in early diastole has not been described. The present study sought to assess the prevalence and mechanism of early diastolic dysfunction of the RV defined as delayed onset of the tricuspid valve (TV flow after TOF repair. Methods The study population consisted of 31 children with repaired TOF (mean age ± SD, 12.3 ± 4.1 years who underwent postoperative cardiovascular magnetic resonance (CMR. The CMR protocol included simultaneous phase-contrast velocity mapping of the atrioventricular valves, which enabled direct comparison of the timing and patterns of tricuspid (TV and mitral (MV valve flow. The TV flow was defined to have delayed onset when its onset was > 20 ms later than the onset of the MV flow. The TV and MV flow from 14 normal children was used for comparison. The CMR results were correlated with the findings on echocardiography and electrocardiography. Result Delayed onset of the TV flow was observed in 16/31 patients and in none of the controls. The mean delay time was 64.81 ± 27.07 ms (8.7 ± 3.2% of R-R interval. The delay time correlated with the differences in duration of the TV and MV flow (55.94 ± 32.88 ms (r = 0.90, p Conclusions Early diastolic dysfunction with delayed onset of TV flow is common after TOF repair, and is associated with reduced RV ejection fraction. It is a further manifestation of interventricular dyssynchrony and represent an additional mechanism of ventricular diastolic dysfunction.

  8. The effect of Sn addition on aging behavior and mechanical properties of wrought AZ80 magnesium alloy

    Highlights: • Thermodynamic and precipitation kinetics calculation was used to analyze aging hardening after addition of Sn. • Precipitation sequences were determined by the content of Sn element. • The microstructure of Mg17Al12 discontinuous precipitates were influenced by Mg2Sn precipitates. - Abstract: The microstructure and mechanical properties of AZ80 wrought magnesium alloys with varying Sn contents (0, 1, 2 and 4 wt.%) have been studied by thermodynamic and precipitation kinetics calculation and examined using scanning electron microscopy (SEM), transmission electron microscopy (TEM), hardness test and uniaxial tensile test at room temperature in this paper. The results of thermodynamic and precipitation kinetics calculation showed that the precipitation sequences were determined by the content of Sn element. It was found that in the aging treatment of this work, Mg17Al12 phase precipitated sooner than Mg2Sn phase in the alloys with less than 1.72 wt.% Sn and there was a contrary precipitation sequence of these two phases in the alloys with more than 1.72 wt.% Sn. Experimental results were in agreement with those of calculation. According to SEM and TEM observation, Sn promoted precipitation of Mg17Al12 on aging temperature, however the preferential Mg2Sn phase suppressed discontinuous Mg17Al12 precipitates by hindering the growth of these in their growth direction. AZ80 with 1–2 wt.% Sn as-aged alloys exhibited outstanding mechanical property that UTS, YS and EL were ∼420 MPa, ∼290 MPa and ∼5%, respectively

  9. Casein Films: The Effects of Formulation, Environmental Conditions and the Addition of Citric Pectin on the Structure and Mechanical Properties

    Laetitia M. Bonnaillie

    2014-07-01

    Full Text Available Thin casein films for food packaging applications reportedly possess good strength and low oxygen permeability, but low elasticity and high sensitivity to moisture. Modifying the films to target specific behaviors depending on environmental conditions can enable a variety of commercial applications for casein-based films. The mechanical properties of solvent-cast (15% solids calcium-caseinate/glycerol films (CaCas:Gly ratio of 3:1 were characterized as a function of processing and environmental conditions, including film thickness, solution formulation and ambient humidity (from 22% to 70% relative humidity (RH at ~20 °C. At constant RH, the elongation at break (EAB had a strong positive dependence on the film thickness. When RH increased, the tensile strength (TS and modulus (E decreased approximately linearly, while EAB increased. From 0.05% to 1% (w/w of citric pectin (CP was then incorporated into CaCas/Gly films following seven different formulations (mixing sequences, to alter the protein network and to evaluate the effects of CP on the tensile properties of CaCas/Gly/CP films. At constant film thickness and ~60% RH, the addition of 0.1% or 1.0% CP to the films considerably increased or decreased EAB, TS and E in different directions and to different extents, depending on the formulation, while optical micrographs also showed vastly differing network configurations, suggesting complex formulation- and stoichiometry-dependent casein-pectin interactions within the dried films. Depending on the desired film properties and utilization conditions, pectin may be a useful addition to casein film formulations for food packaging applications.

  10. Hemolysate-mediated platelet aggregation: an additional risk mechanism contributing to thrombosis of continuous flow ventricular assist devices.

    Tran, Phat L; Pietropaolo, Maria-Grazia; Valerio, Lorenzo; Brengle, William; Wong, Raymond K; Kazui, Toshinobu; Khalpey, Zain I; Redaelli, Alberto; Sheriff, Jawaad; Bluestein, Danny; Slepian, Marvin J

    2016-07-01

    Despite the clinical success and growth in the utilization of continuous flow ventricular assist devices (cfVADs) for the treatment of advanced heart failure, hemolysis and thrombosis remain major limitations. Inadequate and/or ineffective anticoagulation regimens, combined with high pump speed and non-physiological flow patterns, can result in hemolysis which often is accompanied by pump thrombosis. An unexpected increase in cfVADs thrombosis was reported by multiple major VAD implanting centers in 2014, highlighting the association of hemolysis and a rise in lactate dehydrogenase (LDH) presaging thrombotic events. It is well established that thrombotic complications arise from the abnormal shear stresses generated by cfVADs. What remains unknown is the link between cfVAD-associated hemolysis and pump thrombosis. Can hemolysis of red blood cells (RBCs) contribute to platelet aggregation, thereby, facilitating prothrombotic complications in cfVADs? Herein, we examine the effect of RBC-hemolysate and selected major constituents, i.e., lactate dehydrogenase (LDH) and plasma free hemoglobin (pHb) on platelet aggregation, utilizing electrical resistance aggregometry. Our hypothesis is that elements of RBCs, released as a result of shear-mediated hemolysis, will contribute to platelet aggregation. We show that RBC hemolysate and pHb, but not LDH, are direct contributors to platelet aggregation, posing an additional risk mechanism for cfVAD thrombosis. PMID:26590166

  11. Enhancement mechanism of the additional absorbent on the absorption of the absorbing composite using a type-based mixing rule

    Xu, Yonggang; Yuan, Liming; Zhang, Deyuan

    2016-04-01

    A silicone rubber composite filled with carbonyl iron particles and four different carbonous materials (carbon black, graphite, carbon fiber or multi-walled carbon nanotubes) was prepared using a two-roller mixture. The complex permittivity and permeability were measured using a vector network analyzer at the frequency of 2-18 GHz. Then a type-based mixing rule based on the dielectric absorbent and magnetic absorbent was proposed to reveal the enhancing mechanism on the permittivity and permeability. The enforcement effect lies in the decreased percolation threshold and the changing pending parameter as the carbonous materials were added. The reflection loss (RL) result showed the added carbonous materials enhanced the absorption in the lower frequency range, the RL decrement value being about 2 dB at 4-5 GHz with a thickness of 1 mm. All the added carbonous materials reinforced the shielding effectiveness (SE) of the composites. The maximum increment value of the SE was about 3.23 dB at 0.5 mm and 4.65 dB at 1 mm, respectively. The added carbonous materials could be effective additives for enforcing the absorption and shielding property of the absorbers.

  12. Influence of granular strontium chloride as additives on some electrical and mechanical properties for pure polyvinyl alcohol

    A B Elaydy; M Hafez

    2010-04-01

    A matrix composed of polyvinyl-alcohol (PVA) mixed with different concentration ratios of the granular strontium chloride (SrCl2.6H2O) were prepared by casting technique method at room temperature (about 30°C). The electric and dielectric properties such as a.c. electrical conductivity by a conventional method, using Keithly 616 digital electrometer, dielectric constant, and dielectric loss were measured. Calculated equilibrium properties such as lattice constant, bulk modulus and elastic constants are in good agreement with experimental results. The calculated activation energy values agree well with experiment only when the SrCO2 molecules are allowed to displace under strain, indicating the importance of inner strain relaxation. From the elastic constants, theoretical values of the Young’s modulus, shear modulus, Poisson’s ratio, of SrCl2 are obtained. In addition mechanical properties such as Young’s modulus, creep relaxation, and energy stored properties for these samples were also determined at room temperature.

  13. The effect of density and feature size on mechanical properties of isostructural metallic foams produced by additive manufacturing

    Simple models describing the relationship between basic mechanical properties and the relative density of various types of porous metals (such as foams, sponges and lattice structures) are well established. Carefully evaluating these relationships experimentally is challenging, however, because of the stochastic structure of foams and the fact that it is difficult to systematically isolate density changes from variations in other factors, such as pore size and pore distribution. Here a new method for producing systematic sets of stochastic foams is employed based on electron beam melting (EBM) additive manufacturing (AM). To create idealised structures, structural blueprints were reverse-engineered by inverting X-ray computed tomographs of a randomly packed bed of glass beads. This three-dimensional structure was then modified by computer to create five foams of different relative density ρr, but otherwise consistent structure. Yield strength and Young’s modulus have been evaluated in compression tests and compared to existing models for foams. A power of 3 rather than a squared dependence of stiffness on relative density is found, which agrees with a recent model derived for replicated foams. A similar power of 3 relation was found for yield strength. Further analysis of the strength of nominally fully dense rods of different diameters built by EBM AM suggest that surface defects mean that the minimum size of features that can be created by EBM with similar strengths to machined samples is ∼1 mm

  14. Impairments of spatial learning and memory following intrahippocampal injection in rats of 3-mercaptopropionic acid-modified CdTe quantum dots and molecular mechanisms.

    Wu, Tianshu; He, Keyu; Ang, Shengjun; Ying, Jiali; Zhang, Shihan; Zhang, Ting; Xue, Yuying; Tang, Meng

    2016-01-01

    With the rapid development of nanotechnology, quantum dots (QDs) as advanced nanotechnology products have been widely used in neuroscience, including basic neurological studies and diagnosis or therapy for neurological disorders, due to their superior optical properties. In recent years, there has been intense concern regarding the toxicity of QDs, with a growing number of studies. However, knowledge of neurotoxic consequences of QDs applied in living organisms is lagging behind their development, even if several studies have attempted to evaluate the toxicity of QDs on neural cells. The aim of this study was to evaluate the adverse effects of intrahippocampal injection in rats of 3-mercaptopropionic acid (MPA)-modified CdTe QDs and underlying mechanisms. First of all, we observed impairments in learning efficiency and spatial memory in the MPA-modified CdTe QD-treated rats by using open-field and Y-maze tests, which could be attributed to pathological changes and disruption of ultrastructure of neurons and synapses in the hippocampus. In order to find the mechanisms causing these effects, transcriptome sequencing (RNA-seq), an advanced technology, was used to gain the potentially molecular targets of MPA-modified CdTe QDs. According to ample data from RNA-seq, we chose the signaling pathways of PI3K-Akt and MPAK-ERK to do a thorough investigation, because they play important roles in synaptic plasticity, long-term potentiation, and spatial memory. The data demonstrated that phosphorylated Akt (p-Akt), p-ERK1/2, and c-FOS signal transductions in the hippocampus of rats were involved in the mechanism underlying spatial learning and memory impairments caused by 3.5 nm MPA-modified CdTe QDs. PMID:27358562

  15. Impairments of spatial learning and memory following intrahippocampal injection in rats of 3-mercaptopropionic acid-modified CdTe quantum dots and molecular mechanisms

    Wu, Tianshu; He, Keyu; Ang, Shengjun; Ying, Jiali; Zhang, Shihan; Zhang, Ting; Xue, Yuying; Tang, Meng

    2016-01-01

    With the rapid development of nanotechnology, quantum dots (QDs) as advanced nanotechnology products have been widely used in neuroscience, including basic neurological studies and diagnosis or therapy for neurological disorders, due to their superior optical properties. In recent years, there has been intense concern regarding the toxicity of QDs, with a growing number of studies. However, knowledge of neurotoxic consequences of QDs applied in living organisms is lagging behind their development, even if several studies have attempted to evaluate the toxicity of QDs on neural cells. The aim of this study was to evaluate the adverse effects of intrahippocampal injection in rats of 3-mercaptopropionic acid (MPA)-modified CdTe QDs and underlying mechanisms. First of all, we observed impairments in learning efficiency and spatial memory in the MPA-modified CdTe QD-treated rats by using open-field and Y-maze tests, which could be attributed to pathological changes and disruption of ultrastructure of neurons and synapses in the hippocampus. In order to find the mechanisms causing these effects, transcriptome sequencing (RNA-seq), an advanced technology, was used to gain the potentially molecular targets of MPA-modified CdTe QDs. According to ample data from RNA-seq, we chose the signaling pathways of PI3K–Akt and MPAK–ERK to do a thorough investigation, because they play important roles in synaptic plasticity, long-term potentiation, and spatial memory. The data demonstrated that phosphorylated Akt (p-Akt), p-ERK1/2, and c-FOS signal transductions in the hippocampus of rats were involved in the mechanism underlying spatial learning and memory impairments caused by 3.5 nm MPA-modified CdTe QDs. PMID:27358562

  16. Molecular mechanism of endocrine system impairment by 17α-methyltestosterone in gynogenic Pengze crucian carp offspring.

    Zheng, Yao; Chen, Jiazhang; Liu, Yan; Gao, Jiancao; Yang, Yanping; Zhang, Yingying; Bing, Xuwen; Gao, Zexia; Liang, Hongwei; Wang, Zaizhao

    2016-06-01

    The effects of synthetic androgen 17α-methyltestosterone (MT) on endocrine impairment were examined in crucian carp. Immature 7-month old mono-female Pengze crucian carp (Pcc) F2 offspring were exposed to 50 and 100 μg/L of MT (week 2, 4, and 8). Gonadosomatic index, hepatosomatic index and intestine weight altered considerably and oocyte development was repressed. In the treatment groups, ovarian 11-ketotestosterone decreased, whereas 17β-estradiol and testosterone increased, and ovarian aromatase activities increased at week 4. However, in the brain tissue, those values significantly decreased. Quantitative RT-PCR analysis demonstrated changes in steroid receptor genes and upregulation of steroidogenic genes (Pcc-3bhsd, Pcc-11bhsd2 Pcc-cyp11a1), while the other three steroidogenic genes (Pcc-cyp17a1, Pcc-cyp19a1a and Pcc-star) decreased from week 4 to week 8. Ovarian, hepatic Pcc-vtg B and vitellogenin concentration increased in both 50 and 100 μg/L of MT exposure groups. This study adds further information regarding the effects of androgens on the development of previtellogenic oocytes, which suggests that MT could directly target estrogen signaling pathway, or indirectly affect steroidogenesis and vitellogenesis. PMID:26938152

  17. Impairments in testicular function indices in male wistar rats: a possible mechanism for infertility induction by Xylopia aethiopica fruit extract

    Ologhaguo Macstephen Adienbo

    2015-02-01

    Full Text Available Background: The accumulating evidence about alterations in male fertility necessitates the need to screen more medicinal plants for their effect on male reproductive functions. This study is aimed at evaluating the effects of fruit extract of Xylopia aethiopica on testicular functions in males using wistar rats as models. Methods: Forty eight adult male rats, randomly divided into four groups of 12 each, were used for the study. Group 1 (control, while groups 2, 3 and 4 (test groups. Daily oral doses of 0.5, 2.0 and 10.0 mg/kg b.w. of hydro-methanol extract were given to the test groups for 30 days followed by 30 days withdrawal. From each group, 6 animals were sacrificed on days 31 and 61 of the study and samples collected: Testes and epididymis were each weighed; blood was assayed for serum testosterone; testes processed for tissue biochemical studies. Results: Results show significant (P <0.05 reductions in the weight of reproductive organs, serum testosterone; testicular glycogen, cholesterol, protein and malondialdehyde; while testicular superoxide dismutaase increased. Conclusions: It was concluded that Xylopia aethiopica impairs testicular functions in rats and therefore fertility in males. [Int J Reprod Contracept Obstet Gynecol 2015; 4(1.000: 71-75

  18. CRM1 inhibition induces tumor cell cytotoxicity and impairs osteoclastogenesis in multiple myeloma: molecular mechanisms and therapeutic implications

    Tai, Y-T; Landesman, Y; Acharya, C; Calle, Y; Zhong, MY; Cea, M; Tannenbaum, D; Cagnetta, A; Reagan, M; Munshi, AA; Senapedis, W; Saint-Martin, J-R; Kashyap, T; Shacham, S; Kauffman, M; Gu, Y; Wu, L; Ghobrial, I; Zhan, F; Kung, AL; Schey, SA; Richardson, P; Munshi, NC; Anderson, KC

    2013-01-01

    The key nuclear export protein CRM1/XPO1 may represent a promising novel therapeutic target in human multiple myeloma (MM). Here we showed that chromosome region maintenance 1 (CRM1) is highly expressed in patients with MM, plasma cell leukemia cells and increased in patient cells resistant to bortezomib treatment. CRM1 expression also correlates with increased lytic bone and shorter survival. Importantly, CRM1 knockdown inhibits MM cell viability. Novel, oral, irreversible selective inhibitors of nuclear export (SINEs) targeting CRM1 (KPT-185, KPT-330) induce cytotoxicity against MM cells (ED50<200 nM), alone and cocultured with bone marrow stromal cells (BMSCs) or osteoclasts (OC). SINEs trigger nuclear accumulation of multiple CRM1 cargo tumor suppressor proteins followed by growth arrest and apoptosis in MM cells. They further block c-myc, Mcl-1, and nuclear factor κB (NF-κB) activity. SINEs induce proteasome-dependent CRM1 protein degradation; concurrently, they upregulate CRM1, p53-targeted, apoptosis-related, anti-inflammatory and stress-related gene transcripts in MM cells. In SCID mice with diffuse human MM bone lesions, SINEs show strong anti-MM activity, inhibit MM-induced bone lysis and prolong survival. Moreover, SINEs directly impair osteoclastogenesis and bone resorption via blockade of RANKL-induced NF-κB and NFATc1, with minimal impact on osteoblasts and BMSCs. These results support clinical development of SINE CRM1 antagonists to improve patient outcome in MM. PMID:23588715

  19. Antagonizing the αv β3 integrin inhibits angiogenesis and impairs woven but not lamellar bone formation induced by mechanical loading.

    Tomlinson, Ryan E; Schmieder, Anne H; Quirk, James D; Lanza, Gregory M; Silva, Matthew J

    2014-09-01

    Angiogenesis and osteogenesis are critically linked, although the role of angiogenesis is not well understood in osteogenic mechanical loading. In this study, either damaging or non-damaging cyclic axial compression was used to generate woven bone formation (WBF) or lamellar bone formation (LBF), respectively, at the mid-diaphysis of the adult rat forelimb. αv β3 integrin-targeted nanoparticles or vehicle was injected intravenously after mechanical loading. β3 integrin subunit expression on vasculature was maximal 7 days after damaging mechanical loading, but was still robustly expressed 14 days after loading. Accordingly, targeted nanoparticle delivery in WBF-loaded limbs was increased compared with non-loaded limbs. Vascularity was dramatically increased after WBF loading (+700% on day 14) and modestly increased after LBF loading (+50% on day 14). This increase in vascularity was inhibited by nanoparticle treatment in both WBF- and LBF-loaded limbs at days 7 and 14 after loading. Decreased vascularity led to diminished woven, but not lamellar, bone formation. Decreased woven bone formation resulted in impaired structural properties of the skeletal repair, particularly in post-yield behavior. These results demonstrate that αv β3 integrin-mediated angiogenesis is critical for recovering fracture resistance after bone injury but is not required for bone modeling after modest mechanical strain. © 2014 American Society for Bone and Mineral Research. PMID:24644077

  20. Effect of Nb additions on the microstructure, thermal stability and mechanical behavior of high pressure Zr phases under ambient conditions

    Research highlights: → We analyze the influence of Nb additions on the shear-induced α → ω → β phase transformations in pure Zr by high pressure torsion (HPT). → Nb reduces the transition pressures and increases the transformation kinetics. → High pressure phases are retained under ambient conditions due to the presence of an internal stress. → Post-HPT annealing allows to fabricate bimodal/biphase nanostructures with enhanced mechanical behavior. - Abstract: This paper analyzes the influence of Nb on the shear-induced α → ω → β transformation taking place when processing Zr by high pressure torsion (HPT) under suitable conditions of pressure and shear. With that purpose, pure Zr and Zr-2.5%Nb were processed by HPT at room temperature and at pressures ranging from 0.25 to 6 GPa using 5 anvil turns. Nb causes a further reduction of the transition pressures, which are already lower when applying shear besides pressure. Thus, the transition pressure to the β phase is reduced at least 100 times in the Zr-Nb alloy. Alloying with Nb decreases the grain size of the transformed phases, significantly enhances their thermal stability and increases their UTS and elongation to failure. Selected post-HPT annealing treatments lead to the development of very tough, multiphase Zr and Zr-Nb with bimodal grain size distributions. The retention of the high pressure phases under ambient conditions is explained by the development of a high internal stress during processing. This stress is measured by synchrotron radiation diffraction at HZB-BESSY II. It is proposed that the presence of Nb reduces the internal stress level required for the retention of the high pressure phases.

  1. Neural Mechanism of Cognitive Control Impairment in Patients with Hepatic Cirrhosis: A Functional Magnetic Resonance Imaging Study

    Long Jiang Zhang; Guifen Yang; Jianzhong Yin; Yawu Liu; Ji Qi [Dept. of Radiology, Tianjin First Central Hospital of Tianjin Medical Univ, Tianjin (China)

    2007-07-15

    Background: Many studies have claimed the existence of attention alterations in cirrhotic patients without overt hepatic encephalopathy (HE). No functional magnetic resonance imaging (fMRI) study in this respect has been published. Purpose: To investigate the neural basis of cognitive control deficiency in cirrhotic patients using fMRI. Material and Methods: 14 patients with hepatic cirrhosis and 14 healthy volunteers were included in the study. A modified Stroop task with Chinese characters was used as the target stimulus, and block-design fMRI was used to acquire resource data, including four stimulus blocks and five control blocks, each presented alternatively. Image analysis was performed using statistical parametric mapping 99. After fMRI examinations were complete, behavior tests of Stroop interference were performed for all subjects. Overall reaction time and error numbers were recorded. Results: Both healthy volunteers and patients with hepatic cirrhosis had Stroop interference effects. Patients with hepatic cirrhosis had more errors and longer reaction time in performing an incongruous color-naming task than healthy volunteers (P<0.001); there was no significant difference in performing an incongruous word-reading task (P 0.066). Compared with controls, patients with hepatic cirrhosis had greater activation of the bilateral prefrontal cortex and parietal cortex when performing the incongruous word-reading task. With increased conflict, activation of the anterior cingulate cortex (ACC), bilateral prefrontal cortex (PFC), parietal lobe, and temporal fusiform gyrus (TFG) was decreased when patients with hepatic cirrhosis performed the incongruous color-naming task. Conclusion: This study demonstrates that patients with hepatic cirrhostic have cognitive control deficiency. The abnormal brain network of the ACC-PFC-parietal lobe-TFG is the neural basis of cognitive control impairment in cirrhotic patients.

  2. Neural Mechanism of Cognitive Control Impairment in Patients with Hepatic Cirrhosis: A Functional Magnetic Resonance Imaging Study

    Background: Many studies have claimed the existence of attention alterations in cirrhotic patients without overt hepatic encephalopathy (HE). No functional magnetic resonance imaging (fMRI) study in this respect has been published. Purpose: To investigate the neural basis of cognitive control deficiency in cirrhotic patients using fMRI. Material and Methods: 14 patients with hepatic cirrhosis and 14 healthy volunteers were included in the study. A modified Stroop task with Chinese characters was used as the target stimulus, and block-design fMRI was used to acquire resource data, including four stimulus blocks and five control blocks, each presented alternatively. Image analysis was performed using statistical parametric mapping 99. After fMRI examinations were complete, behavior tests of Stroop interference were performed for all subjects. Overall reaction time and error numbers were recorded. Results: Both healthy volunteers and patients with hepatic cirrhosis had Stroop interference effects. Patients with hepatic cirrhosis had more errors and longer reaction time in performing an incongruous color-naming task than healthy volunteers (P<0.001); there was no significant difference in performing an incongruous word-reading task (P 0.066). Compared with controls, patients with hepatic cirrhosis had greater activation of the bilateral prefrontal cortex and parietal cortex when performing the incongruous word-reading task. With increased conflict, activation of the anterior cingulate cortex (ACC), bilateral prefrontal cortex (PFC), parietal lobe, and temporal fusiform gyrus (TFG) was decreased when patients with hepatic cirrhosis performed the incongruous color-naming task. Conclusion: This study demonstrates that patients with hepatic cirrhostic have cognitive control deficiency. The abnormal brain network of the ACC-PFC-parietal lobe-TFG is the neural basis of cognitive control impairment in cirrhotic patients

  3. Effect of Fe addition on microstructure and mechanical properties of Ti-25V-15Cr-2Al-0.2C alloy

    雷力明; 黄旭; 孙福生; 吴学仁; 曹春晓

    2003-01-01

    The effect of 2% Fe addition on the microstructure and mechanical properties of Ti-25V-15Cr-2Al-0.2C alloy(mass fraction)was studied.It is found that the addition of 2% Fe seems to have no obvious effect on the microstructure of the alloy,but results in a significant change in mechanical properties.Compared with the alloy without Fe addition,the alloy with 2% Fe addition exhibits remarkable higher tensile strength and creep resistance,whereas the ductility is relatively lower at room temperature.The significant changes in mechanical properties can be rationalized by the decrease of stacking fault energy caused by the addition of 2% Fe.

  4. Targeted impairment of thymidine kinase 2 expression in cells induces mitochondrial DNA depletion and reveals molecular mechanisms of compensation of mitochondrial respiratory activity

    Highlights: → We impaired TK2 expression in Ost TK1- cells via siRNA-mediated interference (TK2-). → TK2 impairment caused severe mitochondrial DNA (mtDNA) depletion in quiescent cells. → Despite mtDNA depletion, TK2- cells show high cytochrome oxidase activity. → Depletion of mtDNA occurs without imbalance in the mitochondrial dNTP pool. → Nuclear-encoded ENT1, DNA-pol γ, TFAM and TP gene expression is lowered in TK2- cells. -- Abstract: The mitochondrial DNA (mtDNA) depletion syndrome comprises a clinically heterogeneous group of diseases characterized by reductions of the mtDNA abundance, without associated point mutations or rearrangements. We have developed the first in vitro model to study of mtDNA depletion due to reduced mitochondrial thymidine kinase 2 gene (TK2) expression in order to understand the molecular mechanisms involved in mtDNA depletion syndrome due to TK2 mutations. Small interfering RNA targeting TK2 mRNA was used to decrease TK2 expression in Ost TK1- cells, a cell line devoid of endogenous thymidine kinase 1 (TK1). Stable TK2-deficient cell lines showed a reduction of TK2 levels close to 80%. In quiescent conditions, TK2-deficient cells showed severe mtDNA depletion, also close to 80% the control levels. However, TK2-deficient clones showed increased cytochrome c oxidase activity, higher cytochrome c oxidase subunit I transcript levels and higher subunit II protein expression respect to control cells. No alterations of the deoxynucleotide pools were found, whereas a reduction in the expression of genes involved in nucleoside/nucleotide homeostasis (human equilibrative nucleoside transporter 1, thymidine phosphorylase) and mtDNA maintenance (DNA-polymerase γ, mitochondrial transcription factor A) was observed. Our findings highlight the importance of cellular compensatory mechanisms that enhance the expression of respiratory components to ensure respiratory activity despite profound depletion in mtDNA levels.

  5. Examination of Microstructural Characteristics and Mechanical Properties of MgO-MgAl2O4 Composite Refractories with the Addition of Hercynite

    AKSOY, Tuba; AKSEL, Cemil; Kavas, Taner

    2014-01-01

    The incorporation of spinel particles (MgAl2O4) into MgO improves thermal shock resistance and thereby service life of refractories. In this work, hercynite (FeAl2O4) additions at different ratios has been examined to improve mechanical properties of MgO-spinel composites at different spinel ratios. The relationships between mechanical properties and microstructural variables have been investigated in detail. The important parameters improving the mechanical properties of MgO-Spinel-Hercynite...

  6. Phthalates Impair Germ Cell Number in the Mouse Fetal Testis by an Androgen- and Estrogen-Independent Mechanism

    Lehraiki, Abdelali; Racine, Chrystèle; Krust, Andrée; Habert, René; Levacher, Christine

    2009-01-01

    Data from experiments conducted almost exclusively in the rat have established that some phthalates have deleterious effects on the fetal testis probably due to their antiandrogenic and/or estrogenic effects, but their mechanisms of action remain unknown. A recent study reported that phthalates also have deleterious effects on human fetal testis with germ cell number, but not steroidogenesis altered. Therefore, we used organ culture of fetal testes at different stages of development to analyz...

  7. Mechanisms of CFTR functional variants that impair regulated bicarbonate permeation and increase risk for pancreatitis but not for cystic fibrosis.

    Jessica LaRusch; Jinsei Jung; General, Ignacio J.; Lewis, Michele D; Hyun Woo Park; Brand, Randall E.; Andres Gelrud; Anderson, Michelle A.; Banks, Peter A; Darwin Conwell; Christopher Lawrence; Joseph Romagnuolo; John Baillie; Samer Alkaade; Gregory Cote

    2014-01-01

    CFTR is a dynamically regulated anion channel. Intracellular WNK1-SPAK activation causes CFTR to change permeability and conductance characteristics from a chloride-preferring to bicarbonate-preferring channel through unknown mechanisms. Two severe CFTR mutations (CFTRsev ) cause complete loss of CFTR function and result in cystic fibrosis (CF), a severe genetic disorder affecting sweat glands, nasal sinuses, lungs, pancreas, liver, intestines, and male reproductive system. We hypothesize tha...

  8. Mammary gene expression profiles during an intramammary challenge reveal potential mechanisms linking negative energy balance with impaired immune response

    Moyes, Kasey M.; Drackley, James K.; Dawn E. Morin; Rodriguez-Zas, Sandra L.; Everts, Robin E; Harris A Lewin; Loor, Juan J.

    2010-01-01

    Our objective was to compare mammary tissue gene expression profiles during a Streptococcus uberis (S. uberis) mastitis challenge between lactating cows subjected to dietary-induced negative energy balance (NEB; n = 5) and cows fed ad libitum to maintain positive energy balance (PEB; n = 5) to better understand the mechanisms associated with NEB and risk of mastitis during the transition period. The NEB cows were feed-restricted to 60% of calculated net energy for lactation requirements for 7...

  9. A key role for an impaired detoxification mechanism in the etiology and severity of autism spectrum disorders

    Alabdali, Altaf; AL-Ayadhi, Laila; El-Ansary, Afaf

    2014-01-01

    Background Autism Spectrum Disorders (ASD) is a syndrome with a number of etiologies and different mechanisms that lead to abnormal development. The identification of autism biomarkers in patients with different degrees of clinical presentation (i.e., mild, moderate and severe) will give greater insight into the pathogenesis of this disease and will enable effective early diagnostic strategies and treatments for this disorder. Methods In this study, the concentration of two toxic heavy metals...

  10. STUDY OF THE IMPACT OF PHOSPHOGYPSUM ADDITIVE AND FERROUS SULPHATE SOLUTION ON THE MECHANISM OF THE MAGNESIA-BISHOFIT COMPOSITION

    DEREVIANKO V. N.

    2015-11-01

    Full Text Available Problem statement. Phosphogypsum is a very pure raw material [16] with a negative, from a technical point of view, elongated shape of calcium dihydrate crystals (due to the formation conditions, which remains the same after both dehydration in dry air and grinding, this makes technical difficulties relating to further processing of the product into a binder, consequently, water resistance and plasticity of magnesium solutions can be improved by adding primary and secondary phosphates without strength reduction. Famous experts on phosphogypsum Yu. P. Meshcheryakov and N. A. Kolev [8] found, that when adding phosphogypsum instead of natural gypsum during grinding of Portland cement, which is intended to control the setting time of the mixture, there occurred reduction in the initial setting time from 1 h 55 min up to 1 h 36 min (when adding 4 % agent, and the final setting time was decreased from 6 h 15 min up to 6 min. After grinding of phosphogypsum, there appeared a fresh surface, on which the electron emission phenomenon occurs, however, not the entire surface emits, but only the active centres, where field strength reaches 108 V/cm. The positively charged active centres have low CaSO4 2H2O concentration on their surface. Purpose. Specifying the optimal amount of phosphogypsum and ferrous sulphate solution added, studying their impact on the curing mechanism of the magnesia-bishofit composition. Conclusion. To increase the sulphate compound, required for the crystallinity [10] reduction and magnesia stone sealing [4], the ferrous sulphate solution have been added to the composition formulation, ferrous sulphate anions immediately polarize free calcium ions with the formation of CaSO4∙2H2O. P. P. Budkov's experiments [8] prove that the larger the magnesia cement-to-sulphate stone ratio, the lower the setting time of the composition, and the higher the tensile strength of the stone. Moreover, V. V. Shchelyaghin [15] recommended adding ferrous

  11. Physiological, molecular, and cellular mechanisms of impaired seawater tolerance following exposure of Atlantic salmon, Salmo salar, smolts to acid and aluminum

    Monette, Michelle Y., E-mail: michelle.monette@yale.edu [Organismic and Evolutionary Biology Program, University of Massachusetts, Amherst, MA 01003 (United States); USGS, Conte Anadromous Fish Research Center, Turners Falls, MA 01376 (United States); Yada, Takashi [Freshwater Fisheries Research Department, National Research Institute of Fisheries Science, Nikko (Japan); Matey, Victoria [Department of Biology, San Diego State University, San Diego, CA 92182 (United States); McCormick, Stephen D. [Organismic and Evolutionary Biology Program, University of Massachusetts, Amherst, MA 01003 (United States); USGS, Conte Anadromous Fish Research Center, Turners Falls, MA 01376 (United States)

    2010-08-01

    We examined the physiological, molecular, and cellular mechanisms of impaired ion regulation in Atlantic salmon, Salmo salar, smolts following acute acid and aluminum (Al) exposure. Smolts were exposed to: control (pH 6.5, 3.4 {mu}g l{sup -1} Al), acid and low Al (LAl: pH 5.4, 11 {mu}g l{sup -1} Al), acid and moderate Al (MAl: pH 5.3, 42 {mu}g l{sup -1} Al), and acid and high Al (HAl: pH 5.4, 56 {mu}g l{sup -1} Al) for two and six days. At each time-point, smolts were sampled directly from freshwater treatment tanks and after a 24 h seawater challenge. Exposure to acid/MAl and acid/HAl led to accumulation of gill Al, substantial alterations in gill morphology, reduced gill Na{sup +}/K{sup +}-ATPase (NKA) activity, and impaired ion regulation in both freshwater and seawater. Exposure to acid/MAl for six days also led to a decrease in gill mRNA expression of the apical Cl{sup -} channel (cystic fibrosis transmembrane conductance regulator I), increased apoptosis upon seawater exposure, an increase in the surface expression of mitochondria-rich cells (MRCs) within the filament epithelium of the gill, but reduced abundance of gill NKA-positive MRCs. By contrast, smolts exposed to acid and the lowest Al concentration exhibited minor gill Al accumulation, slight morphological modifications in the gill, and impaired seawater tolerance in the absence of a detectable effect on freshwater ion regulation. These impacts were accompanied by decreased cell proliferation, a slight increase in the surface expression of MRCs within the filament epithelium, but no impact on gill apoptosis or total MRC abundance was observed. However, MRCs in the gills of smolts exposed to acid/LAl exhibited morphological alterations including decreased size, staining intensity, and shape factor. We demonstrate that the seawater tolerance of Atlantic salmon smolts is extremely sensitive to acute exposure to acid and low levels of Al, and that the mechanisms underlying this depend on the time

  12. Folic acid deficiency induces premature hearing loss through mechanisms involving cochlear oxidative stress and impairment of homocysteine metabolism

    Martínez-Vega, Raquel; Garrido, Francisco; Partearroyo, Teresa; Cediel, Rafael; Varela, Gregorio; Varela-Nieto, Isabel; Pajares, María A.

    2015-01-01

    Nutritional imbalance is emerging as a causative factor of hearing loss. Epidemiologic studies have linked hearing loss to elevated plasma total homocysteine (tHcy) and folate deficiency, and have shown that folate supplementation lowers tHcy levels potentially ameliorating age-related hearing loss. The purpose of this study was to address the impact of folate deficiency on hearing loss and to examine the underlying mechanisms. For this purpose, 2-mo-old C57BL/6J mice (Animalia Chordata Mus m...

  13. Visual Impairment

    ... poorly lit spaces, and colors that seem faded. Diabetic retinopathy (pronounced: reh-ton-AH-pa-thee) occurs when ... that is likely to cause visual impairment, many treatments are available. Options may include eyeglasses, contact lenses, ...

  14. Embedded Glove’ To Aid The Visually Impaired

    Sankar Kumar S, Abarna J, Lavanya G, Nithya Lakshmi S

    2013-03-01

    Full Text Available This paper presents a model of ‘Embedded Glove’, a hand mounted tactile (vibration mechanism feedback Sound Navigation And Ranging (SONAR obstacle avoidance system, by warning through vibration motors for visually impaired to whom traveling in indoor/outdoor environments is really a difficult task. This system acts as an Electronic Travelling Aid (ETA providing independent mobility of the visually impaired. This model comprises of a glove strapped to the wrist, embedded with ultrasonic sensors, battery, microcontroller and vibrator motors. Along with being completely reliable, this system also provides to be a cost-effective guidance mechanism for the visually impaired. The system is designed to scan a wide area with a set of ultrasonic sensors which also provides a good range and speed in the detection of the obstacle. The detected obstacle is immediately notified to the possessor thereby the presence of obstacle along with its direction is conveyed to the visually impaired person by means of a tactile system. The energy consumption for the whole system is controlled by a Photovoltaic (PV panel, making it more efficient. The analysis described in this paper helps to estimate the distance at which the obstacle is present based on the reliability of measurement performed with ultrasonic sensors. It is also possible to detect the speed of moving objects in addition to direction with increased accuracy, with the enhanced response timings and varying intensities in the vibration mechanism.

  15. Addition of Oils to Polylactide Casting Solutions as a Tool to Tune Film Morphology and Mechanical Properties

    Sawalha, H.I.M.; Schroën, C.G.P.H.; Boom, R.M.

    2010-01-01

    Poly(L-lactide) (PLLA) films exhibit toughening by the addition of oils to the polymer casting. This was investigated by casting films from solution and evaporation in air; the investigated oils were linear alkanes, cyclic alkanes, and two terpenes (limonene and eugenol). The addition of the oils gr

  16. Effect of Ce-rich misch metal addition on squeeze cast microstructure and mechanical properties of AZ81 alloy

    2008-01-01

    The effect of cerium-rich misch metal addition on the microstructure and properties of squeeze cast magnesium alloys AZ81 was empirically investigated. The results indicate that the addition of cerium-rich misch metal modifies the microstructure gradually. With the increase of the RE addition, the amount of Mg17Al12 decreases while that of Al11(RE)3 increases, accompanied by grain refinement. When the addition reaches 1.5%, the grain refinement becomes obvious. However, when the addition exceeds 2.0%,Al11(RE)3 phase coarsens into rod shape and the grain size increases. The tensile properties of the AZ81 at both room temperature and 150℃ increase with the addition, and reach their optimal values with the addition of 1.5%. Further increase of the addition to above 2.0% decreases the tensile properties considerably. The tensile fracture of the alloy is characterized by the cleavage of the brittle second phases and ductile dimples of the matrix.

  17. Mechanisms of CFTR functional variants that impair regulated bicarbonate permeation and increase risk for pancreatitis but not for cystic fibrosis.

    Jessica LaRusch

    2014-07-01

    Full Text Available CFTR is a dynamically regulated anion channel. Intracellular WNK1-SPAK activation causes CFTR to change permeability and conductance characteristics from a chloride-preferring to bicarbonate-preferring channel through unknown mechanisms. Two severe CFTR mutations (CFTRsev cause complete loss of CFTR function and result in cystic fibrosis (CF, a severe genetic disorder affecting sweat glands, nasal sinuses, lungs, pancreas, liver, intestines, and male reproductive system. We hypothesize that those CFTR mutations that disrupt the WNK1-SPAK activation mechanisms cause a selective, bicarbonate defect in channel function (CFTRBD affecting organs that utilize CFTR for bicarbonate secretion (e.g. the pancreas, nasal sinus, vas deferens but do not cause typical CF. To understand the structural and functional requirements of the CFTR bicarbonate-preferring channel, we (a screened 984 well-phenotyped pancreatitis cases for candidate CFTRBD mutations from among 81 previously described CFTR variants; (b conducted electrophysiology studies on clones of variants found in pancreatitis but not CF; (c computationally constructed a new, complete structural model of CFTR for molecular dynamics simulation of wild-type and mutant variants; and (d tested the newly defined CFTRBD variants for disease in non-pancreas organs utilizing CFTR for bicarbonate secretion. Nine variants (CFTR R74Q, R75Q, R117H, R170H, L967S, L997F, D1152H, S1235R, and D1270N not associated with typical CF were associated with pancreatitis (OR 1.5, p = 0.002. Clones expressed in HEK 293T cells had normal chloride but not bicarbonate permeability and conductance with WNK1-SPAK activation. Molecular dynamics simulations suggest physical restriction of the CFTR channel and altered dynamic channel regulation. Comparing pancreatitis patients and controls, CFTRBD increased risk for rhinosinusitis (OR 2.3, p<0.005 and male infertility (OR 395, p<<0.0001. WNK1-SPAK pathway-activated increases in

  18. Impairment of interrelated iron- and copper homeostatic mechanisms in brain contributes to the pathogenesis of neurodegenerative disorders

    Skjørringe, Tina; Møller, Lisbeth Birk; Moos, Torben

    2012-01-01

    (DMT1) is involved in the uptake of both iron and copper. Furthermore, copper is an essential co-factor in numerous proteins that are vital for iron homeostasis and affects the binding of iron-response proteins to iron-response elements in the mRNA of the transferrin receptor, DMT1, and ferroportin......Iron and copper are important co-factors for a number of enzymes in the brain, including enzymes involved in neurotransmitter synthesis and myelin formation. Both shortage and an excess of iron or copper will affect the brain. The transport of iron and copper into the brain from the circulation is...... strictly regulated, and concordantly protective barriers, i.e., the blood-brain barrier (BBB) and the blood-cerebrospinal fluid (CSF) barrier (BCB) have evolved to separate the brain environment from the circulation. The uptake mechanisms of the two metals interact. Both iron deficiency and overload lead...

  19. Mammary gene expression profiles during an intramammary challenge reveal potential mechanisms linking negative energy balance with impaired immune response

    Moyes, Kasey; Drackley, J K; Morin, D E;

    2010-01-01

    order to better understand the mechanisms associated with NEB and risk of mastitis during the transition period. The NEB cows were feed-restricted to 60% of calculated net energy for lactation requirements for 7 d, and cows assigned to PEB were fed the same diet for ad libitum intake. Five days after...... 0.05), with 86 DEG up-regulated and 201 DEG down-regulated. Canonical pathways most affected by NEB were IL-8 Signaling (10 genes), Glucocorticoid Receptor Signaling (13), and NRF2-mediated Oxidative Stress Response (10). Among genes differentially expressed by NEB, Cell Growth and Proliferation (48......) and Cellular Development (36) were the most enriched functions. Regarding immune response, HLA-A was up-regulated due to NEB, whereas the majority of genes involved in immune response were down-regulated (e.g., AKT1, IRAK1, MAPK9, and TRAF6). This study provided new avenues for investigation into the...

  20. A high-fat diet impairs cooling-evoked brown adipose tissue activation via a vagal afferent mechanism.

    Madden, Christopher J; Morrison, Shaun F

    2016-08-01

    In dramatic contrast to rats on a control diet, rats maintained on a high-fat diet (HFD) failed to activate brown adipose tissue (BAT) during cooling despite robust increases in their BAT activity following direct activation of their BAT sympathetic premotor neurons in the raphe pallidus. Cervical vagotomy or blockade of glutamate receptors in the nucleus of the tractus solitarii (NTS) reversed the HFD-induced inhibition of cold-evoked BAT activity. Thus, a HFD does not prevent rats from mounting a robust, centrally driven BAT thermogenesis; however, a HFD does alter a vagal afferent input to NTS neurons, thereby preventing the normal activation of BAT thermogenesis to cooling. These results, paralleling the absence of cooling-evoked glucose uptake in the BAT of obese humans, reveal a neural mechanism through which consumption of a HFD contributes to reduced energy expenditure and thus to weight gain. PMID:27354235

  1. Impairments of spatial learning and memory following intrahippocampal injection in rats of 3-mercaptopropionic acid-modified CdTe quantum dots and molecular mechanisms

    Wu T

    2016-06-01

    Full Text Available Tianshu Wu,1,2 Keyu He,1,2 Shengjun Ang,1,2 Jiali Ying,1,2 Shihan Zhang,1,2 Ting Zhang,1,2 Yuying Xue,1,2 Meng Tang1,2 1Key Laboratory of Environmental Medicine and Engineering, Ministry of Education, School of Public Health, Collaborative Innovation Center of Suzhou Nano Science and Technology, 2Jiangsu Key Laboratory for Biomaterials and Devices, Southeast University, Nanjing, People’s Republic of China Abstract: With the rapid development of nanotechnology, quantum dots (QDs as advanced nanotechnology products have been widely used in neuroscience, including basic neurological studies and diagnosis or therapy for neurological disorders, due to their superior optical properties. In recent years, there has been intense concern regarding the toxicity of QDs, with a growing number of studies. However, knowledge of neurotoxic consequences of QDs applied in living organisms is lagging behind their development, even if several studies have attempted to evaluate the toxicity of QDs on neural cells. The aim of this study was to evaluate the adverse effects of intrahippocampal injection in rats of 3-mercaptopropionic acid (MPA-modified CdTe QDs and underlying mechanisms. First of all, we observed impairments in learning efficiency and spatial memory in the MPA-modified CdTe QD-treated rats by using open-field and Y-maze tests, which could be attributed to pathological changes and disruption of ultrastructure of neurons and synapses in the hippocampus. In order to find the mechanisms causing these effects, transcriptome sequencing (RNA-seq, an advanced technology, was used to gain the potentially molecular targets of MPA-modified CdTe QDs. According to ample data from RNA-seq, we chose the signaling pathways of PI3K–Akt and MPAK–ERK to do a thorough investigation, because they play important roles in synaptic plasticity, long-term potentiation, and spatial memory. The data demonstrated that phosphorylated Akt (p-Akt, p-ERK1/2, and c-FOS signal

  2. Effects of nano TiN addition on the microstructure and mechanical properties of TiC based steel bonded carbides

    WANG Zhi'an; DAI Haiyang; ZOU Yu

    2008-01-01

    TiC based steel bonded carbides with the addition of nano TiN were prepared by vicuum sintering techniques.The microstructure was investigated using scanning electron microscopy(SEM)and transmission electron microscopy (TEM),and the mechanical properties,such as bending strength,impact toughness,hardness,and density,were measured.The results indicate that the grain size becomes small and there is uniformity in the steel bonded carbide with nano addition;several smaller carbide particles are also found to be inlaid in the rim of the larger carbide grains and prevent the coalescence of TiC grains.The smaller and larger carbide grains joint firmly,and then the reduction of the average size of the grains leads to the increase in the mechanical properties of the steel bonded carbides with nano addition.But the mechanical properties do not increase monotonously with an increase in nano addition.When the nano TiN addition accounts for 6-8 wt.% of the amount of steel bonded carbides.the mechanical properties reach the maximum values and then decrease with further increase in nano TiN addition.

  3. Stimulators of mineralization limit the invasive phenotype of human osteosarcoma cells by a mechanism involving impaired invadopodia formation.

    Anna Cmoch

    Full Text Available BACKGROUND: Osteosarcoma (OS is a highly aggressive bone cancer affecting children and young adults. Growing evidence connects the invasive potential of OS cells with their ability to form invadopodia (structures specialized in extracellular matrix proteolysis. RESULTS: In this study, we tested the hypothesis that commonly used in vitro stimulators of mineralization limit the invadopodia formation in OS cells. Here we examined the invasive potential of human osteoblast-like cells (Saos-2 and osteolytic-like (143B OS cells treated with the stimulators of mineralization (ascorbic acid and B-glycerophosphate and observed a significant difference in response of the tested cells to the treatment. In contrast to 143B cells, osteoblast-like cells developed a mineralization phenotype that was accompanied by a decreased proliferation rate, prolongation of the cell cycle progression and apoptosis. On the other hand, stimulators of mineralization limited osteolytic-like OS cell invasiveness into collagen matrix. We are the first to evidence the ability of 143B cells to degrade extracellular matrix to be driven by invadopodia. Herein, we show that this ability of osteolytic-like cells in vitro is limited by stimulators of mineralization. CONCLUSIONS: Our study demonstrates that mineralization competency determines the invasive potential of cancer cells. A better understanding of the molecular mechanisms by which stimulators of mineralization regulate and execute invadopodia formation would reveal novel clinical targets for treating osteosarcoma.

  4. The role of Hf and TiC additions in the mechanical properties and microstructure of NbAlV alloys

    The microstructures and mechanical properties of Nb-12Al-20V (at.%) containing Hf or TiC have been investigated. The microstructures were characterised using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The NbAlV alloy is single B2 phase, the 5% Hf added completely dissolving into the matrix. The addition of 5% Hf and 5% TiC resulted in the formation of MC-type Hf-rich carbide. Compression testing has been carried out at room temperature, 1273 and 1473 K. The alloys show good compression ductility at room temperature. Hf addition gave a slight increase in strength at both room temperature and high temperature. The addition of both Hf and TiC significantly improves the strength. The room temperature strength of these alloys could be well described by solid solution strengthening and a load transfer mechanism. The alloys deform primarily via dislocation slip, with some mechanical twinning.

  5. Diastereoselective Addition of α-Metalated Sulfoxides to Imines Revisited: Mechanism, Computational Studies, and the Effect of External Chiral Ligands

    Pedersen, Brian; Rein, Tobias; Søtofte, Inger;

    2003-01-01

    six-membered "flat chair") was probed by quantum mechanical calculations, which underpinned the idea of using external chiral ligands to enhance the diastereoselectivity of otherwise moderately selective reactions. In this way, the diastereomeric ratio of the product 3a could be raised from (84 : 16...

  6. Comprehensive study on mechanical properties of lime-based pastes with additions of metakaolin and brick dust

    Nežerka, V.; Slížková, Zuzana; Tesárek, P.; Plachý, T.; Frankeová, Dita; Petráňová, Veronika

    2014-01-01

    Roč. 64, October (2014), s. 17-29. ISSN 0008-8846 R&D Projects: GA MK(CZ) DF11P01OVV008 Keywords : microstructure * mechanical properties * CaO * metakaolin * brick dust Subject RIV: AL - Art, Architecture, Cultural Heritage Impact factor: 2.864, year: 2014 http://www.sciencedirect.com/science/article/pii/S0008884614001239

  7. Effects of rare earth Er additions on microstructure development and mechanical properties of die-cast ADC12 aluminum alloy

    Highlights: ► The α-Al dendrite and the eutectic Si were significantly refined by adding Er. ► The Hv of alloys first increased with increasing Er content, then decreases. ► The UTS of alloys increased with addition of Er, but the EL decreased. - Abstract: The effects of rare earth erbium (Er) additions (0, 0.3, 0.6 and 0.9 wt.%) on the microstructure development and tensile properties of die-cast ADC12 aluminum alloy have been investigated in the present work. The microstructures and fracture surfaces of die-cast samples were examined by optical microscopy and scanning electron microscopy (SEM). It was found that the secondary dendrite arm spacing (SDAS) will decrease with increasing Er content, as the Er content increases to 0.6%, the lowest SDAS was obtained. In addition, the Er modified the eutectic silicon from a coarse plate-like and acicular structure to a fine branched and fibrous one. The microhardness of die-casted alloys were measured, the microhardness corresponding to the die-casted samples with 0, 0.3, 0.6 and 0.9 wt.% Er additions are 100.6, 107.1, 113.6 and 108.5 Hv, respectively. The tensile properties were improved by the addition of Er, and a good ultimate tensile strength (269 MPa) but poor elongation (2%) were obtained when the Er addition was 0.6 wt.%. Furthermore, fractographic examinations revealed that refined pore and spheroidized α-Al dendrite were responsible for the high ultimate tensile strength.

  8. Low temperature impact toughness and fracture mechanism of cast QT400-18L ductile iron with different Ni additions

    Zhang Xinning; Qu Yingdong; Yang Hongwang

    2013-01-01

    Different contents of Ni (0.3wt.% to 1.2wt.%) were added to the QT400-18L ductile iron to investigate the effect of Ni addition on the impact toughness of cast ductile irons at low temperatures. The impact toughnesses of the samples at room and low temperatures were tested. The microstructures and fractographs were observed. Results show that with the increase of Ni addition there is a general trend of refinement of the ferrite matrix while the nodule density shows no obvious change. When the...

  9. Investigation of microstructure and mechanical properties of aluminum hybrid nano-composites with the additions of solid lubricant

    Highlights: • Aluminium hybrid nano-composite was made by mechanical alloying successfully. • High energy ball milling resulted in homogeneous distribution of reinforcements. • MA combined with pressing allowed to produce nano-crystalline matrix composites. • Hybrid nano-composites exhibited the best mechanical properties. • Wear resistance of the aluminum hybrid nano-composites found increased with increased filler content. - Abstract: In this experimental study, the tribological behavior of Al 2024–5 wt.% SiC–X wt.% graphite (X = 5 and 10) hybrid nano-composites was produced using powder metallurgy (P/M) technique. All specimens were prepared by mechanical milling of Al 2024 and SiC–Gr nano-composite powders, followed by a blend–press–sinter methodology. Pin on disc type apparatus has been used for determining the wear loss. The sintered samples have been characterized by XRD. Wear mechanisms are discussed based on scanning electron microscopy observations of worn surface and wear debris morphology. The hardness and wear resistance of the hybrid nano-composites were increased considerably by increasing the reinforcement content. The nano-composite with 5 wt.% SiC and 10 wt.% Gr showed the greatest improvement in tribological performance. Primary wear mechanisms for hybrid nano-composites were determined to be formation of lubricating layer on the surface of samples. The overall results revealed that hybrid aluminium nano-composites can be considered as an outstanding material where high strength and wear-resistant components are of major importance, particularly structural applications in the aerospace, automotive and military industries

  10. Targeted impairment of thymidine kinase 2 expression in cells induces mitochondrial DNA depletion and reveals molecular mechanisms of compensation of mitochondrial respiratory activity

    Villarroya, Joan, E-mail: joanvillarroya@gmail.com [Institut de Recerca, Hospital Universitari de la Vall d' Hebron, Barcelona (Spain); Institut de Recerca l' Hospital de la Santa Creu i Sant Pau, Barcelona (Spain); Lara, Mari-Carmen [Institut de Recerca, Hospital Universitari de la Vall d' Hebron, Barcelona (Spain); Department of Neurology, Columbia University Medical Center, New York, NY (United States); Centro de Investigacion Biomedica en Red de Enfermedades Raras (CIBERER), ISCIII (Spain); Dorado, Beatriz [Department of Neurology, Columbia University Medical Center, New York, NY (United States); Garrido, Marta [Unitat de Biologia Cel.lular i Molecular, IMIM-Hospital del Mar, Barcelona (Spain); Garcia-Arumi, Elena [Institut de Recerca, Hospital Universitari de la Vall d' Hebron, Barcelona (Spain); Centro de Investigacion Biomedica en Red de Enfermedades Raras (CIBERER), ISCIII (Spain); Meseguer, Anna [Institut de Recerca, Hospital Universitari de la Vall d' Hebron, Barcelona (Spain); Hirano, Michio [Department of Neurology, Columbia University Medical Center, New York, NY (United States); Vila, Maya R. [Institut de Recerca, Hospital Universitari de la Vall d' Hebron, Barcelona (Spain)

    2011-04-08

    Highlights: {yields} We impaired TK2 expression in Ost TK1{sup -} cells via siRNA-mediated interference (TK2{sup -}). {yields} TK2 impairment caused severe mitochondrial DNA (mtDNA) depletion in quiescent cells. {yields} Despite mtDNA depletion, TK2{sup -} cells show high cytochrome oxidase activity. {yields} Depletion of mtDNA occurs without imbalance in the mitochondrial dNTP pool. {yields} Nuclear-encoded ENT1, DNA-pol {gamma}, TFAM and TP gene expression is lowered in TK2{sup -} cells. -- Abstract: The mitochondrial DNA (mtDNA) depletion syndrome comprises a clinically heterogeneous group of diseases characterized by reductions of the mtDNA abundance, without associated point mutations or rearrangements. We have developed the first in vitro model to study of mtDNA depletion due to reduced mitochondrial thymidine kinase 2 gene (TK2) expression in order to understand the molecular mechanisms involved in mtDNA depletion syndrome due to TK2 mutations. Small interfering RNA targeting TK2 mRNA was used to decrease TK2 expression in Ost TK1{sup -} cells, a cell line devoid of endogenous thymidine kinase 1 (TK1). Stable TK2-deficient cell lines showed a reduction of TK2 levels close to 80%. In quiescent conditions, TK2-deficient cells showed severe mtDNA depletion, also close to 80% the control levels. However, TK2-deficient clones showed increased cytochrome c oxidase activity, higher cytochrome c oxidase subunit I transcript levels and higher subunit II protein expression respect to control cells. No alterations of the deoxynucleotide pools were found, whereas a reduction in the expression of genes involved in nucleoside/nucleotide homeostasis (human equilibrative nucleoside transporter 1, thymidine phosphorylase) and mtDNA maintenance (DNA-polymerase {gamma}, mitochondrial transcription factor A) was observed. Our findings highlight the importance of cellular compensatory mechanisms that enhance the expression of respiratory components to ensure respiratory activity

  11. The mechanism of deceleration of nucleation and crystal growth by the small addition of transition metals to lithium disilicate glasses.

    Thieme, Katrin; Avramov, Isak; Rüssel, Christian

    2016-01-01

    The addition of small amounts of niobium or tantalum oxide to lithium disilicate glass provokes a drastic decrease of the steady-state nucleation rates and the crystal growth velocities. The viscosity of the residual glassy matrix is considered as a function of the crystallization degree in the course of a non-isothermal crystallization. For simplification, a homogeneous distribution of the added oxides in the glass matrix is assumed. While the viscosity initially decreases, it significantly increases again for higher crystallization degrees hindering crystal growth. However, it was shown that the additives are enriched at the crystal interface. Several possible reasons for the inhibition of nucleation and growth kinetics such as viscosity, interfacial energy crystal/glassy phase, thermodynamic driving force or impingement rate are discussed. Since the crystallization front is blocked by the additives the impingement rate is decreased with increasing additive concentration. Since small concentrations of Nb2O5 and Ta2O5 have a drastic effect on the nucleation, these components should be enriched at the interface crystal/glass. This will only take place, if it leads to a decrease in the interfacial energy. Since this effect alone should result in an increase of the nucleation rate, it must be overcompensated by kinetic effects. PMID:27150844

  12. Densification of Reaction Bonded Silicon Nitride with the Addition of Fine Si Powder Effects on the Sinterability and Mechanical Properties

    Lee, Sea-Hoon [Korea Institute of Materials Science; Cho, Chun-Rae [Korea Institute of Materials Science; Park, Young-Jo [Korea Institute of Materials Science; Ko, Jae-Woong [Korea Institute of Materials Science; Kim, Hai-Doo [Korea Institute of Materials Science; Lin, Hua-Tay [ORNL; Becher, Paul F [ORNL

    2013-01-01

    The densification behavior and strength of sintered reaction bonded silicon nitrides (SRBSN) that contain Lu2O3-SiO2 additives were improved by the addition of fine Si powder. Dense specimens (relative density: 99.5%) were obtained by gas-pressure sintering (GPS) at 1850oC through the addition of fine Si. In contrast, the densification of conventional specimens did not complete at 1950oC. The fine Si decreased the onset temperature of shrinkage and increased the shrinkage rate because the additive helped the compaction of green bodies and induced the formation of fine Si3N4 particles after nitridation and sintering at and above 1600oC. The amount of residual SiO2 within the specimens was not strongly affected by adding fine Si powder because most of the SiO2 layer that had formed on the fine Si particles decomposed during nitridation. The maximum strength and fracture toughness of the specimens were 991 MPa and 8.0 MPa m1/2, respectively.

  13. On crystallochemical mechanism of small alloying addition effect on dissolution process of corrosion-resistant steels in active state

    Regularities of component dissolution and the changes of the surface layer composition of the Fe-Cr and Fe-Cr-Mo steels are studied. The investigations have been carried out taking as an example high-purity ferrite steels of the FeCr18 and FeCr26 type with Mo content from O to 1.7 and from 0 to 1.2 at. % in 1n H2SO4 respectively at room temperature. The notions of dissolution character of energetically heterogeneous alloy surface are developed. A conclusion is made on the mechanism of inhibitting effect of molybdenum on the anode process of steel dissolution in the active state and on the mechanism of its effect on steel passivation capacity

  14. Delayed onset of tricuspid valve flow in repaired tetralogy of Fallot: an additional mechanism of diastolic dysfunction and interventricular dyssynchrony

    Benson Lee N; Redington Andrew N; Bronzetti Gabriele; Cheung Michael; AlHabshan Fahad; Sun Ai-Min; Macgowan Christopher; Yoo Shi-Joon

    2011-01-01

    Abstract Background Diastolic dysfunction of the right ventricle (RV) is common after repair of tetralogy of Fallot. While restrictive physiology in late diastole has been well known, dysfunction in early diastole has not been described. The present study sought to assess the prevalence and mechanism of early diastolic dysfunction of the RV defined as delayed onset of the tricuspid valve (TV) flow after TOF repair. Methods The study population consisted of 31 children with repaired TOF (mean ...

  15. Investigation of Mechanical Properties of Fe3Al-Based Alloys with Vanadium and Carbon Additions by Small Punch Test

    Dobeš, Ferdinand; Dymáček, Petr; Kratochvíl, P.; Král, R.; Çelikyürek, I.; Torun, O.

    Ostrava : Ocelot s.r.o, 2014 - (Matocha, K.; Hurst, R.; Sun, W.), s. 159-163 ISBN 978-80-260-6722-1. [SSTT 2014 - International Conference Determination of Mechanical Properties of Materials by Small Punch and Other Miniature Testing Techniques /3./. Seggau (AT), 23.09.2014-25.09.2014] R&D Projects: GA ČR(CZ) GAP108/12/1452 Institutional support: RVO:68081723 Keywords : small punch * yield stress * ultimate tensile strength Subject RIV: JG - Metallurgy

  16. The heterogeneity of verbal short-term memory impairment in aphasia.

    Majerus, Steve; Attout, Lucie; Artielle, Marie-Amélie; Van der Kaa, Marie-Anne

    2015-10-01

    Verbal short-term memory (STM) impairment represents a frequent and long-lasting deficit in aphasia, and it will prevent patients from recovering fully functional language abilities. The aim of this study was to obtain a more precise understanding of the nature of verbal STM impairment in aphasia, by determining whether verbal STM impairment is merely a consequence of underlying language impairment, as suggested by linguistic accounts of verbal STM, or whether verbal STM impairment reflects an additional, specific deficit. We investigated this question by contrasting item-based STM measures, supposed to depend strongly upon language activation, and order-based STM measures, supposed to reflect the operation of specific, serial order maintenance mechanisms, in a sample of patients with single-word processing deficits at the phonological and/or lexical level. A group-level analysis showed robust impairment for both item and serial order STM aspects in the aphasic group relative to an age-matched control group. An analysis of individual profiles revealed an important heterogeneity of verbal STM profiles, with patients presenting either selective item STM deficits, selective order STM deficits, generalized item and serial order STM deficits or no significant STM impairment. Item but not serial order STM impairment correlated with the severity of phonological impairment. These results disconfirm a strong version of the linguistic account of verbal STM impairment in aphasia, by showing variable impairment to both item and serial order processing aspects of verbal STM. PMID:26275964

  17. Processing, Mechanical and Optical Properties of Additive-Free ZrC Ceramics Prepared by Spark Plasma Sintering

    Clara Musa

    2016-06-01

    Full Text Available In the present study, nearly fully dense monolithic ZrC samples are produced and broadly characterized from microstructural, mechanical and optical points of view. Specifically, 98% dense products are obtained by Spark Plasma Sintering (SPS after 20 min dwell time at 1850 °C starting from powders preliminarily prepared by Self-propagating High-temperature Synthesis (SHS followed by 20 min ball milling. A prolonged mechanical treatment up to 2 h of SHS powders does not lead to appreciable benefits. Vickers hardness of the resulting samples (17.5 ± 0.4 GPa is reasonably good for monolithic ceramics, but the mechanical strength (about 250 MPa up to 1000 °C could be further improved by suitable optimization of the starting powder characteristics. The very smoothly polished ZrC specimen subjected to optical measurements displays high absorption in the visible-near infrared region and low thermal emittance at longer wavelengths. Moreover, the sample exhibits goodspectral selectivity (2.1–2.4 in the 1000–1400 K temperature range. These preliminary results suggest that ZrC ceramics produced through the two-step SHS/SPS processing route can be considered as attractive reference materials for the development of innovative solar energy absorbers.

  18. Effect of carbon nanotube and aluminum oxide addition on plasma-sprayed hydroxyapatite coating's mechanical properties and biocompatibility

    This study reports on the synthesis of novel bioceramic composite coating of hydroxyapatite (HA) reinforced with carbon nanotubes (CNTs) and aluminum oxide (Al2O3) using plasma spray technique. Fracture toughness of HA-20 wt.% Al2O3 improved by 158% as compared to HA coating whereas HA-18.4 wt.% Al2O3-1.6 wt.% CNT showed an improvement of 300%. Carbon nanotubes provided reinforcement via rebar mechanism. Human fiber osteoblast cell-growth studies showed that biocompatibility of the coating remained unaltered, as Al2O3 retained its bio-inertness and CNT, its bioactivity, within the composite coatings. Composite coating showed lower attachment, but higher proliferation rate, for the osteoblast cells, which has been attributed to the surface roughness. An optimized relation between coating composition, its biocompatibility and mechanical properties was established to predict the most suited coating material for orthopedic implants. HA-Al2O3-CNT composite coating displayed most improved mechanical properties while retaining its biocompatibility.

  19. Effect of additional element and heat treating temperature on micro-structure and mechanical behavior of Ag alloy thin film

    JU Dong-ying; ISHIGURO S; ARIZONO T; HASEGAWA K

    2006-01-01

    For Ag alloy film used for the storage media,it is required to have heat-resistance,anti-constant temperature and anti-constant humidity characteristics,corrosion resistance,while high reflectivity over Al is maintained. An Ag alloy thin film (additive element Pd,Cu,P) was created on glass substrates,and various heat treatment was conducted. Then,fine structure was observed on this thin film using AFM,and fine structure evaluation of the inside was carried out by the in-plane diffractometry and X-ray diffractometry,and in addition,residual stress analysis was carried out. These results were compared and were examined,and fine structure and physical property in a metallic thin film were evaluated,and usefulness of evaluation method was verified.

  20. Additive manufacturing of Ti-6Al-4V components by shaped metal deposition: Microstructure and mechanical properties

    Shaped metal deposition (SMD) is a relatively new technology of additive manufacturing, which creates near-net shaped components by additive manufacture utilizing tungsten inert gas welding. Especially for Ti alloys, which are difficult to shape by traditional methods and for which the loss of material during machining is also very costly, SMD has great advantages. In the case of Ti-6Al-4V the dense SMD components exhibit large, columnar prior β grains, with a Widmanstaetten α/β microstructure. These prior β grains are slightly tilted in a direction following the temperature field resulting from the moving welding torch. The ultimate tensile strength is between 929 and 1014 MPa, depending on orientation and location of the tensile specimens. Tensile testing vertically to the deposition layers exhibits a strain at failure of 16 ± 3%, while testing parallel to the layers gives a lower value of about 9%.

  1. Ostwald ripening of Pb nanocrystalline phase in mechanically milled Al-Pb alloys and the influence of Cu additive

    The coarsening behavior of nanosized Pb phase in both Al-10%Pb and Al-10%Pb-4.5%Cu alloys has been studied by X-ray diffraction and transmission electron microscopy analysis. The coarsening of Pb nanophase in Al-Pb alloys still follows the classical ripening theory (the LSW theory) and the addition of Cu decreases the coarsening rate of Pb nanophase

  2. The effect of the addition of ground olive stones on the physical and mechanical properties of clay bricks

    Arezki, S.; Chelouah, N.; Tahakourt, A.

    2016-01-01

    This study deals with the effect of ground olive stones (GOS) on the performance of fired clay bricks. Seven different clay-GOS mixes with 0, 1, 2, 3, 4, 5 and 10 wt % of GOS respectively were used for making fired brick samples. All samples were fired at 900 °C. The technological properties of the resultant material were then determined, including shrinkage, apparent density, pore size distribution, thermal conductivity, water absorption, and compressive and flexural strength. The addition o...

  3. Thermo-mechanic and sensory properties of wheat and rye breads produced with varying concentration of the additive

    Demin Mirjana A.; Popov-Raljić Jovanka V.; Laličić-Petronijević Jovanka G.; Rabrenović Biljana B.; Filipčev Bojana V.; Šimurina Olivera D.

    2013-01-01

    The effects of different concentrations of the complex additive containing emulsifiers, oxido-reductive substances and enzymes, on the rheological conditions of dough, and on the sensory properties of three groups of bread were investigated. The best initial quality and the lowest degree of protein network weakening had the dough obtained from mixed wheat and rye flours. The best expected baking properties were shown by the white wheat flour due to the least damage of its starch. The us...

  4. Improvement of mechanical and biological properties of TiNi alloys by addition of Cu and Co to orthodontic archwires.

    Phukaoluan, Aphinan; Khantachawana, Anak; Kaewtatip, Pongpan; Dechkunakorn, Surachai; Kajornchaiyakul, Julathep

    2016-09-01

    The purpose of this study was to investigate improved performances of TiNi in order to promote tooth movement. Special attention was paid to the effect on the clinical properties of TiNi of adding Cu and Co to this alloy. Ti49.4Ni50.6, Ti49Ni46Cu5 and Ti50Ni47Co3 (at %) alloys were prepared. Specimens were cold-rolled at 30% reduction and heat-treated at 400°C for 60min. Then, the test results were compared with two types of commercial archwires. The findings showed that superelasticity properties were confirmed in the manufactured commercial alloys at mouth temperature. The difference of stress plateau in TiNi, TiNiCo and commercial wires B at 25°C changed significantly at various testing temperatures due to the combination of martensite and austenite phases. At certain temperatures the alloys exhibited zero recovery stress at 2% strain and consequently produced zero activation force for moving teeth. The corrosion test showed that the addition of Cu and Co to TiNi alloys generates an increase in corrosion potential (Ecorr) and corrosion current densities (Icorr). Finally, we observed that addition of Cu and Co improved cell viability. We conclude that addition of an appropriate amount of a third alloying element can help enhance the performances of TiNi orthodontic archwires. PMID:27520713

  5. The Effect and Mechanism of Nano-Cu Lubricating Additives on the Electroless Deposited Ni-W-P Coating

    CHEN Min; JIANG Xiaomin; ZHAO Zuxin; HUANG Xiaobo

    2012-01-01

    The coating and deposition process with excellent anti wear and suitable for industrial application were developed,and the optimum bath composition and process were obtained by studying the influence of the bath composition,temperature and pH value on the deposition rate and the plating solution stability.Moreover,the tribological properties of nano-Cu lubricating additives and electroless deposited Ni-W-P coating as well as their synergistic effect are researched using ring-block abrasion testing machine and energy dispersive spectrometer.Research results show that Ni-W-P alloy coating and nano-Cu lubricating additive have excellent synergistic effect,e g,the wear resistance of Ni-W-P alloy coating (with heat treatment and the oil with nano-Cu additives) has increased hundreds times than 45 steel as the metal substrate with the basic oil,and zero wear is achieved,which breaks through the bottleneck of previous separate research of the above-mentioned two aspects.

  6. Thermo-mechanic and sensory properties of wheat and rye breads produced with varying concentration of the additive

    Demin Mirjana A.

    2013-01-01

    Full Text Available The effects of different concentrations of the complex additive containing emulsifiers, oxido-reductive substances and enzymes, on the rheological conditions of dough, and on the sensory properties of three groups of bread were investigated. The best initial quality and the lowest degree of protein network weakening had the dough obtained from mixed wheat and rye flours. The best expected baking properties were shown by the white wheat flour due to the least damage of its starch. The use of the additive has an effect on the absorption of water and on the majority of C-values of all sorts of flour. The amount of additive had a significant effect on the sensory properties of wheat bread crumb texture. Also, storage duration significantly affected (p <0.01 the sensory properties of integral wheat bread aroma-taste and the weighted mean score. The interaction of these two factors had no significant effect on any of sensory properties of the investigated groups of bread.

  7. Male and Couple Fertility Impairment due to HPV-DNA Sperm Infection: Update on Molecular Mechanism and Clinical Impact—Systematic Review

    Salvatore Gizzo

    2014-01-01

    Full Text Available Recent evidences identify Human Papillomavirus (HPV sperm infection as a possible cause of male and couple infertility. It acts through different mechanisms at various steps of human conception and early gestational development. We performed a systematic review to assess the role of HPV semen infection on male and couple infertility. Analysis of available and eligible data does not permit us to fund clear evidences about clinical impact of HPV infection on fertility, although sperm parameters impairment is the most widely recognized effect. Regarding biomolecular implications, the available data are often conflicting. More studies are required to define the role of HPV sperm infection in clinical practice. The great majority of evidences are obtained by in vitro studies and this fact represents a limitation for the clinical management of HPVDNA sperm infection. Understanding the biological significance of HPV-DNA semen infection could permit us to explain most of the idiopathic male and couple infertility, leading to a better management of infertile men and a better timing for sperm banking storage before ART cycles.

  8. Mechanism of protection of bystander cells by exogenous carbon monoxide: Impaired response to damage signal of radiation-induced bystander effect

    Han, W. [Department of Physics and Materials Science, City University of Hong Kong, 83 Tat Chee Avenue, Kowloon Tong, Kowloon (Hong Kong); Center of Medical Physics and Technology, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei 230031 (China); Yu, K.N., E-mail: peter.yu@cityu.edu.hk [Department of Physics and Materials Science, City University of Hong Kong, 83 Tat Chee Avenue, Kowloon Tong, Kowloon (Hong Kong); Wu, L.J. [Center of Medical Physics and Technology, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei 230031 (China); Wu, Y.C. [Center of Medical Physics and Technology, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei 230031 (China); School of Nuclear Science and Technology, University of Science and Technology of China, Hefei 230029 (China); Wang, H.Z. [Center of Medical Physics and Technology, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei 230031 (China)

    2011-05-10

    A protective effect of exogenous carbon monoxide (CO), generated by CO releasing molecule ticarbonyldichlororuthenium (II) dimer (CORM-2), on the bystander cells from the toxicity of radiation-induced bystander effect (RIBE) was revealed in our previous study. In the present work, a possible mechanism of this CO effect was investigated. The results from medium transfer experiments showed that {alpha}-particle irradiated Chinese hamster ovary (CHO) cells would release nitric oxide (NO), which was detected with specific NO fluorescence probe, to induce p53 binding protein 1 (BP1) formation in the cell population receiving the medium, and the release peak was found to be at 1 h post irradiation. Treating the irradiated or bystander cells separately with CO (CORM-2) demonstrated that CO was effective in the bystander cells but not the irradiated cells. Measurements of NO production and release with a specific NO fluorescence probe also showed that CO treatment did not affect the production and release of NO by irradiated cells. Protection of CO on cells to peroxynitrite, an oxidizing free radical from NO, suggested that CO might protect bystander cells via impaired response of bystander cells to NO, a RIBE signal in our research system.

  9. Mechanism of protection of bystander cells by exogenous carbon monoxide: Impaired response to damage signal of radiation-induced bystander effect

    A protective effect of exogenous carbon monoxide (CO), generated by CO releasing molecule ticarbonyldichlororuthenium (II) dimer (CORM-2), on the bystander cells from the toxicity of radiation-induced bystander effect (RIBE) was revealed in our previous study. In the present work, a possible mechanism of this CO effect was investigated. The results from medium transfer experiments showed that α-particle irradiated Chinese hamster ovary (CHO) cells would release nitric oxide (NO), which was detected with specific NO fluorescence probe, to induce p53 binding protein 1 (BP1) formation in the cell population receiving the medium, and the release peak was found to be at 1 h post irradiation. Treating the irradiated or bystander cells separately with CO (CORM-2) demonstrated that CO was effective in the bystander cells but not the irradiated cells. Measurements of NO production and release with a specific NO fluorescence probe also showed that CO treatment did not affect the production and release of NO by irradiated cells. Protection of CO on cells to peroxynitrite, an oxidizing free radical from NO, suggested that CO might protect bystander cells via impaired response of bystander cells to NO, a RIBE signal in our research system.

  10. Ornithine and Homocitrulline Impair Mitochondrial Function, Decrease Antioxidant Defenses and Induce Cell Death in Menadione-Stressed Rat Cortical Astrocytes: Potential Mechanisms of Neurological Dysfunction in HHH Syndrome.

    Zanatta, Ângela; Rodrigues, Marília Danyelle Nunes; Amaral, Alexandre Umpierrez; Souza, Débora Guerini; Quincozes-Santos, André; Wajner, Moacir

    2016-09-01

    Hyperornithinemia-hyperammonemia-homocitrullinuria (HHH) syndrome is caused by deficiency of ornithine translocase leading to predominant tissue accumulation and high urinary excretion of ornithine (Orn), homocitrulline (Hcit) and ammonia. Although affected patients commonly present neurological dysfunction manifested by cognitive deficit, spastic paraplegia, pyramidal and extrapyramidal signs, stroke-like episodes, hypotonia and ataxia, its pathogenesis is still poorly known. Although astrocytes are necessary for neuronal protection. Therefore, in the present study we investigated the effects of Orn and Hcit on cell viability (propidium iodide incorporation), mitochondrial function (thiazolyl blue tetrazolium bromide-MTT-reduction and mitochondrial membrane potential-ΔΨm), antioxidant defenses (GSH) and pro-inflammatory response (NFkB, IL-1β, IL-6 and TNF-α) in unstimulated and menadione-stressed cortical astrocytes that were previously shown to be susceptible to damage by neurotoxins. We first observed that Orn decreased MTT reduction, whereas both amino acids decreased GSH levels, without altering cell viability and the pro-inflammatory factors in unstimulated astrocytes. Furthermore, Orn and Hcit decreased cell viability and ΔΨm in menadione-treated astrocytes. The present data indicate that the major compounds accumulating in HHH syndrome impair mitochondrial function and reduce cell viability and the antioxidant defenses in cultured astrocytes especially when stressed by menadione. It is presumed that these mechanisms may be involved in the neuropathology of this disease. PMID:27161368

  11. Hearing Impairment

    ... hearing loss is present at birth. Acquired hearing loss happens later in life — during childhood, the teen years, or in adulthood — ... for your ears to avoid a permanent hearing loss. See your doctor right away ... basis. What's Life Like for People Who Are Hearing Impaired? For ...

  12. MICROSTRUCTURE AND MECHANICAL PROPERTIES OF ULTRAFINE WC/Co CEMENTED CARBIDES WITH CUBIC BORON NITRIDE AND Cr₃C₂ ADDITIONS

    Genrong Zhang; Haiyan Chen; Dong Lihua; Yin,; Li Kun

    2016-01-01

    This study investigates the microstructure and mechanical properties of ultrafine tungsten carbide and cobalt (WC/Co) cemented carbides with cubic boron nitride (CBN) and chromium carbide (Cr₃C₂) fabricated by a hot pressing sintering process. This study uses samples with 8 wt% Co content and 7.5 vol% CBN content, and with different Cr₃C₂ content ranging from 0 to 0.30 wt%. Based on the experimental results, Cr₃C₂ content has a significant influence on inhibiting abnormal grain growth and dec...

  13. MICROSTRUCTURE AND MECHANICAL PROPERTIES OF ULTRAFINE WC/Co CEMENTED CARBIDES WITH CUBIC BORON NITRIDE AND Cr₃C₂ ADDITIONS

    Genrong Zhang

    2016-03-01

    Full Text Available This study investigates the microstructure and mechanical properties of ultrafine tungsten carbide and cobalt (WC/Co cemented carbides with cubic boron nitride (CBN and chromium carbide (Cr₃C₂ fabricated by a hot pressing sintering process. This study uses samples with 8 wt% Co content and 7.5 vol% CBN content, and with different Cr₃C₂ content ranging from 0 to 0.30 wt%. Based on the experimental results, Cr₃C₂ content has a significant influence on inhibiting abnormal grain growth and decreasing grain size in cemented carbides. Near-full densification is possible when CBN-WC/Co with 0.25 wt% Cr₃C₂ is sintered at 1350°C and 20 MPa; the resulting material possesses optimal mechanical properties and density, with an acceptable Vickers hardness of 19.20 GPa, fracture toughness of 8.47 MPa.m1/2 and flexural strength of 564 MPa.u̇ Å k⃗

  14. Response of Mg Addition on the Dendritic Structures and Mechanical Properties of Hypoeutectic Al-10Si (Wt Pct) Alloys

    Karaköse, Ercan; Yildiz, Mehmet; Keskin, Mustafa

    2016-08-01

    Rapidly solidified hypoeutectic Al-10Si- xMg ( x = 0, 5, 10 wt pct) alloys were produced by the melt-spinning method. The phase composition was identified by X-ray diffractometry, and the microstructures of the alloys were characterized by scanning electron microscopy. The melting characteristics were studied by differential scanning calorimetry and differential thermal analysis under an Ar atmosphere. The mechanical properties of the melt-spun and conventionally solidified alloys were tested by tensile-strength and Vickers microhardness tests. The results illustrate that the cooling rate and solidification time of 89 μm thick melt-spun ribbon were estimated to be 2.97 × 107 K s-1 and 9.31 × 10-6 s, respectively. Nanoscale Si spot particles were observed growing on the surface of the dendritic α-Al matrix and the average sizes of these spots ranged from 10 to 50 nm. The improvement in the tensile properties and microhardness was related to structural refinement and the supersaturated α-Al solid solution; the nanoscale-dispersed Si spot particles made a significant improvement to the mechanical properties of the melt-spun ribbon. Detailed electrical resistivity tests of the ribbons were carried out at temperatures of 300 K to 800 K (27 °C to 527 °C).

  15. Vascular cognitive impairment

    N.V. Vakhnina

    2014-05-01

    Full Text Available Vascular pathology of the brain is the second most common cause of cognitive impairment after Alzheimer's disease. The article describes the modern concepts of etiology, pathogenetic mechanisms, clinical features and approaches to diagnosis and therapy of vascular cognitive impairment (VCI. Cerebrovascular accident, chronic cerebral circulatory insufficiency and their combination, sometimes in combination with a concomitant neurodegenerative process, are shown to be the major types of brain lesions leading to VCI. The clinical presentation of VCI is characterized by the neuropsychological status dominated by impairment of the executive frontal functions (planning, control, attention in combination with focal neurological symptoms. The diagnosis is based on comparing of the revealed neuropsychological and neurological features with neuroimaging data. Neurometabolic, acetylcholinergic, glutamatergic, and other vasoactive drugs and non-pharmacological methods are widely used to treat VCI. 

  16. Disruption of nuclear factor (erythroid-derived-2)-like 2 antioxidant signaling: a mechanism for impaired activation of stem cells and delayed regeneration of skeletal muscle.

    Shelar, Sandeep Balu; Narasimhan, Madhusudhanan; Shanmugam, Gobinath; Litovsky, Silvio Hector; Gounder, Sellamuthu S; Karan, Goutam; Arulvasu, Cinnasamy; Kensler, Thomas W; Hoidal, John R; Darley-Usmar, Victor M; Rajasekaran, Namakkal S

    2016-05-01

    Recently we have reported that age-dependent decline in antioxidant levels accelerated apoptosis and skeletal muscle degeneration. Here, we demonstrate genetic ablation of the master cytoprotective transcription factor, nuclear factor (erythroid-derived-2)-like 2 (Nrf2), aggravates cardiotoxin (CTX)-induced tibialis anterior (TA) muscle damage. Disruption of Nrf2 signaling sustained the CTX-induced burden of reactive oxygen species together with compromised expression of antioxidant genes and proteins. Transcript/protein expression of phenotypic markers of muscle differentiation, namely paired box 7 (satellite cell) and early myogenic differentiation and terminal differentiation (myogenin and myosin heavy chain 2) were increased on d 2 and 4 postinjury but later returned to baseline levels on d 8 and 15 in wild-type (WT) mice. In contrast, these responses were persistently augmented in Nrf2-null mice suggesting that regulation of the regeneration-related signaling mechanisms require Nrf2 for normal functioning. Furthermore, Nrf2-null mice displayed slower regeneration marked by dysregulation of embryonic myosin heavy chain temporal expression. Histologic observations illustrated that Nrf2-null mice displayed smaller, immature TA muscle fibers compared with WT counterparts on d 15 after CTX injury. Improvement in TA muscle morphology and gain in muscle mass evident in the WT mice was not noticeable in the Nrf2-null animals. Taken together these data show that the satellite cell activation, proliferation, and differentiation requires a functional Nrf2 system for effective healing following injury.-Shelar, S. B., Narasimhan, M., Shanmugam, G., Litovsky, S. H., Gounder, S. S., Karan, G., Arulvasu, C., Kensler, T. W., Hoidal, J. R., Darley-Usmar, V. M., Rajasekaran, N. S. Disruption of nuclear factor (erythroid-derived-2)-like 2 antioxidant signaling: a mechanism for impaired activation of stem cells and delayed regeneration of skeletal muscle. PMID:26839378

  17. The mechanism of alkene addition to a nickel bis(dithiolene) complex: the role of the reduced metal complex.

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

    2012-03-14

    The binding of an alkene by Ni(tfd)(2) [tfd = S(2)C(2)(CF(3))(2)] is one of the most intriguing ligand-based reactions. In the presence of the anionic, reduced metal complex, the primary product is an interligand adduct, while in the absence of the anion, dihydrodithiins and metal complex decomposition products are preferred. New kinetic (global analysis) and computational (DFT) data explain the crucial role of the anion in suppressing decomposition and catalyzing the formation of the interligand product through a dimetallic complex that appears to catalyze alkene addition across the Ni-S bond, leading to a lower barrier for the interligand adduct. PMID:22364208

  18. Microstructure, Texture and Mechanical Property Evolution during Additive Manufacturing of Ti6Al4V Alloy for Aerospace Applications

    Antonysamy, Alphons Anandaraj

    2012-01-01

    Additive Manufacturing (AM) is an innovative manufacturing process which offers near-net shape fabrication of complex components, directly from CAD models, without dies or substantial machining, resulting in a reduction in lead-time, waste, and cost. For example, the buy-to-fly ratio for a titanium component machined from forged billet is typically 10-20:1 compared to 5-7:1 when manufactured by AM. However, the production rates for most AM processes are relatively slow and AM is consequently ...

  19. The improved mechanical properties of β-CaSiO3 bioceramics with Si3N4 addition.

    Pan, Ying; Zuo, Kaihui; Yao, Dongxu; Yin, Jinwei; Xin, Yunchuan; Xia, Yongfeng; Liang, Hanqin; Zeng, Yuping

    2015-03-01

    The motivation of this study is to investigate the effect of Si3N4 addition on the sinterability of β-CaSiO3 ceramics. β-CaSiO3 ceramics with different content of Si3N4 were prepared at the sintering temperature ranging from 1000°C to 1150°C. The results showed that Si3N4 can be successfully used as sintering additive by being oxidized to form SiO2. The β-CaSiO3 ceramics with 3wt% Si3N4 sintered at 1100°C revealed flexural strength, hardness and fracture toughness of 157.2MPa, 4.4GPa and 2.3MPam(1/2) respectively, which was much higher than that of pure β-CaSiO3 ceramics (41.1MPa, 1.0GPa, 1.1MPam(1/2)). XRD analysis and SEM observation indicated that the main phase maintained to be β-phase after sintering. PMID:26580024

  20. Ptp1b deletion in pro-opiomelanocortin neurons increases energy expenditure and impairs endothelial function via TNF-α dependent mechanisms.

    Bruder-Nascimento, Thiago; Kennard, Simone; Antonova, Galina; Mintz, James D; Bence, Kendra K; Belin de Chantemèle, Eric J

    2016-06-01

    Protein tyrosine phosphatase 1b (Ptp1b) is a negative regulator of leptin and insulin-signalling pathways. Its targeted deletion in proopiomelanocortin (POMC) neurons protects mice from obesity and diabetes by increasing energy expenditure. Inflammation accompanies increased energy expenditure. Therefore, the present study aimed to determine whether POMC-Ptp1b deletion increases energy expenditure via an inflammatory process, which would impair endothelial function. We characterized the metabolic and cardiovascular phenotypes of Ptp1b+/+ and POMC-Ptp1b-/- mice. Clamp studies revealed that POMC-Ptp1b deletion reduced body fat and increased energy expenditure as evidenced by a decrease in feed efficiency and an increase in oxygen consumption and respiratory exchange ratio. POMC-Ptp1b deletion induced a 2.5-fold increase in plasma tumour necrosis factor α (TNF-α) levels and elevated body temperature. Vascular studies revealed an endothelial dysfunction in POMC-Ptp1b-/- mice. Nitric oxide synthase inhibition [N-nitro-L-arginine methyl ester (L-NAME)] reduced relaxation to a similar extent in Ptp1b+/+ and POMC-Ptp1b-/- mice. POMC-Ptp1b deletion decreased ROS-scavenging enzymes [superoxide dismutases (SODs)] whereas it increased ROS-generating enzymes [NADPH oxidases (NOXs)] and cyclooxygenase-2 (COX-1) expression, in aorta. ROS scavenging or NADPH oxidase inhibition only partially improved relaxation whereas COX-2 inhibition and thromboxane-A2 (TXA2) antagonism fully restored relaxation in POMC-Ptp1b-/- mice Chronic treatment with the soluble TNF-α receptor etanercept decreased body temperature, restored endothelial function and reestablished aortic COX-2, NOXs and SOD expression to their baseline levels in POMC-Ptp1b-/- mice. However, etanercept promoted body weight gain and decreased energy expenditure in POMC-Ptp1b-/- mice. POMC-Ptp1b deletion increases plasma TNF-α levels, which contribute to body weight regulation via increased energy expenditure and impair

  1. Influence of Tin Additions on the Phase-Transformation Characteristics of Mechanical Alloyed Cu-Al-Ni Shape-Memory Alloy

    Saud, Safaa N.; Hamzah, E.; Abubakar, T.; Bakhsheshi-Rad, H. R.; Mohammed, M. N.

    2016-07-01

    The influence of the addition of Sn to Cu-Al-Ni alloy as a fourth element with different percentages of 0.5, 1.0, and 1.5 wt pct on the microstructure, phase-transformation temperatures, mechanical properties, and corrosion behaviors was investigated. The modified and unmodified alloys were fabricated by mechanical alloying followed by microwave sintering. The sintered and homogenized alloys of Cu-Al-Ni-xSn shape-memory alloys had a refined particle structure with an average particle size of 40 to 50 µm associated with an improvement in the mechanical properties and corrosion resistance. With the addition of Sn, the porosity density tends to decrease, which can also lead to improvements in the properties of the modified alloys. The minimum porosity percentage was observed in the Cu-Al-Ni-1.0 wt pct Sn alloy, which resulted in enhancing the ductility, strain recovery, and corrosion resistance. Further increasing the Sn addition to 1.5 wt pct, the strength of the alloy increased because the highest volume fraction of precipitates was formed. Regarding the corrosion behavior, addition of Sn up to 1 wt pct increased the corrosion resistance of the base SMA from 2.97 to 19.20 kΩ cm2 because of formation of a protective film that contains hydrated tin oxyhydroxide, aluminum dihydroxychloride, and copper chloride on the alloy. However, further addition of Sn reduced the corrosion resistance.

  2. Emotional impairment in Parkinson's disease

    CHEN Hai-bo

    2013-08-01

    Full Text Available Emotional impairment is the common complication of Parkinson's disease (PD. Depression, anxiety and apathy affect the quality of life and the prognosis of PD patients. Neuropsychological and neuroimaging studies of emotional impairment in PD patients suggest abnormalities involving mesolimbic and mesocortical dopaminergic pathways, but the specific mechanism needs further study. In this review we discuss the clinical manifestation, possible pathological mechanism, diagnosis and treatment in PD patients.

  3. Bioinformatics and Microarray Analysis of miRNAs in Aged Female Mice Model Implied New Molecular Mechanisms for Impaired Fracture Healing

    He, Bing; Zhang, Zong-Kang; Liu, Jin; He, Yi-Xin; Tang, Tao; Li, Jie; Guo, Bao-Sheng; Lu, Ai-Ping; Zhang, Bao-Ting; Zhang, Ge

    2016-01-01

    Impaired fracture healing in aged females is still a challenge in clinics. MicroRNAs (miRNAs) play important roles in fracture healing. This study aims to identify the miRNAs that potentially contribute to the impaired fracture healing in aged females. Transverse femoral shaft fractures were created in adult and aged female mice. At post-fracture 0-, 2- and 4-week, the fracture sites were scanned by micro computed tomography to confirm that the fracture healing was impaired in aged female mice and the fracture calluses were collected for miRNA microarray analysis. A total of 53 significantly differentially expressed miRNAs and 5438 miRNA-target gene interactions involved in bone fracture healing were identified. A novel scoring system was designed to analyze the miRNA contribution to impaired fracture healing (RCIFH). Using this method, 11 novel miRNAs were identified to impair fracture healing at 2- or 4-week post-fracture. Thereafter, function analysis of target genes was performed for miRNAs with high RCIFH values. The results showed that high RCIFH miRNAs in aged female mice might impair fracture healing not only by down-regulating angiogenesis-, chondrogenesis-, and osteogenesis-related pathways, but also by up-regulating osteoclastogenesis-related pathway, which implied the essential roles of these high RCIFH miRNAs in impaired fracture healing in aged females, and might promote the discovery of novel therapeutic strategies. PMID:27527150

  4. Mechanical Properties of DS NiAl/Cr(Mo) Alloys with Low Addition of Hf for High-temperature Applications

    Xinghao DU; Jianting GUO

    2005-01-01

    A multiphase NiAl-28Cr-5.85Mo-0.15Hf alloy, which was directionally solidified (DS) in an Al2O3-SiO2 mold by standard Bridgman method and then underwent prolonged solution and aging treatment was prepared. The microstructure, tensile properties as well as tensile creep of the heat-treated alloy at different temperatures were studied. The alloy was composed of NiAl, Cr(Mo) and Hf-rich phase and small amount of fine Heusler phase (Ni2AlHf). Although the present alloy exhibited high tensile strength at Iow temperature, it was weaker than that of system with high content Hf but still stronger than that of many NiAl-based alloys at high temperatures. The fracture toughness is lower than that of DS NiAl-28Cr-6Mo alloy. Nevertheless, advantageous effects on the mechanical properties, i.e.the decrease in brittle-to-ductile transition temperature (BDTT) were obtained for the Iow content of Hf. The obtained creep curves exhibit conventional shape: a short primary creep and long accelerated creep stages. The rupture properties of the heat-treated alloy follow the Monkman-Grant relationship, which exhibits similar creep behavior to that of NiAl/Cr(Mo) system with high Hf content.

  5. The effect of the addition of ground olive stones on the physical and mechanical properties of clay bricks

    Arezki, S.

    2016-06-01

    Full Text Available This study deals with the effect of ground olive stones (GOS on the performance of fired clay bricks. Seven different clay-GOS mixes with 0, 1, 2, 3, 4, 5 and 10 wt % of GOS respectively were used for making fired brick samples. All samples were fired at 900 °C. The technological properties of the resultant material were then determined, including shrinkage, apparent density, pore size distribution, thermal conductivity, water absorption, and compressive and flexural strength. The addition of GOS to the mixture reduced the compressive strength of fired clay bricks. All clay brick pieces exhibited low firing shrinkage. It was apparent that as the percentage of GOS increased in the body, there was a noticeable increase in porosity. The water absorption coefficient decreased with increasing additions. The results indicated that thermal conductivity decreases with decrease in density and increase in porosity in fired clay bricks.En este trabajo se ha estudiado el efecto de la incorporación de huesos de aceituna triturados en las prestaciones de ladrillos de arcilla cocida. Se utilizaron siete proporciones de huesos de aceituna 0 %, 1 %, 2 %, 3 %, 4 %, 5 % y 10 % en peso. Todas las muestras se calcinaron a 900 °C y posteriormente se determinaron las propiedades resultantes, incluyendo la densidad aparente, retracción, distribución de tamaños de poro, conductividad térmica, absorción de agua y resistencias mecánicas. La adición de huesos de aceituna molidos a la mezcla redujo la resistencia a la compresión de los ladrillos de arcilla cocida. Además se observó que todas las piezas de ladrillo mostraron baja retracción tras exposición a altas temperaturas. Como era de esperar a medida que el porcentaje de huesos de aceituna molidos aumentó, la porosidad se incrementó de manera evidente. El coeficiente de absorción de agua disminuyó con el aumento del porcentaje de sustitución. Los resultados indicaron que la conductividad t

  6. Effect of addition of plants-derived polyamide 11 elastomer on the mechanical and tribological properties of hemp fiber reinforced polyamide 1010 composites

    Mukaida, Jun; Nishitani, Yosuke; Kitano, Takeshi

    2015-05-01

    For the purpose of developing the new engineering materials such as structural materials and tribomaterials based on all plants-derived materials, the effect of the addition of plant-derived polyamide 11 Elastomer (PA11E) on the mechanical and tribological properties of hemp fiber(HF) reinforced polyamide 1010 (HF/PA1010) composites was investigated. PA1010 and PA11E (except the polyether groups used as soft segment) were made from plant-derived castor oil. Hemp fiber was surface-treated by two types of treatment: alkali treatment by NaOH solution and surface treatment by ureido silane coupling agent. HF/PA1010/PA11E ternary composites were extruded by a twin screw extruder and injection-molded. Their mechanical properties such as tensile, bending, Izod impact and tribological properties by ring-on-plate type sliding wear testing were evaluated. The effect of the addition of PA11E on the mechanical and tribological properties of HF/PA1010 composite differed for each property. Izod impact strength and specific wear rate improved with the addition of PA11E although tensile strength, modulus, and friction coefficient decreased with PA11E. It follows from these results that it may be possible to develop the new engineering materials with sufficient balance between mechanical and tribological properties.

  7. Effect of Zr, Nb and Ti addition on injection molded 316L stainless steel for bio-applications: Mechanical, electrochemical and biocompatibility properties.

    Gulsoy, H Ozkan; Pazarlioglu, Serdar; Gulsoy, Nagihan; Gundede, Busra; Mutlu, Ozal

    2015-11-01

    The research investigated the effect of Zr, Nb and Ti additions on mechanical, electrochemical properties and biocompatibility of injection molded 316L stainless steel. Addition of elemental powder is promoted to get high performance of sintered 316L stainless steels. The amount of additive powder plays a role in determining the sintered microstructure and all properties. In this study, 316L stainless steel powders used with the elemental Zr, Nb and Ti powders. A feedstock containing 62.5 wt% powders loading was molded at different injection molded temperature. The binders were completely removed from molded components by solvent and thermal debinding at different temperatures. The debinded samples were sintered at 1350°C for 60 min. Mechanical, electrochemical property and biocompatibility of the sintered samples were performed mechanical, electrochemical, SBF immersion tests and cell culture experiments. Results of study showed that sintered 316L and 316L with additives samples exhibited high corrosion properties and biocompatibility in a physiological environment. PMID:26275484

  8. Enhancement of the Mechanical Properties of Basalt Fiber-Wood-Plastic Composites via Maleic Anhydride Grafted High-Density Polyethylene (MAPE Addition

    Yun Lu

    2013-06-01

    Full Text Available This study investigated the mechanisms, using microscopy and strength testing approaches, by which the addition of maleic anhydride grafted high-density polyethylene (MAPE enhances the mechanical properties of basalt fiber-wood-plastic composites (BF-WPCs. The maximum values of the specific tensile and flexural strengths are achieved at a MAPE content of 5%–8%. The elongation increases rapidly at first and then continues slowly. The nearly complete integration of the wood fiber with the high-density polyethylene upon MAPE addition to WPC is examined, and two models of interfacial behavior are proposed. We examined the physical significance of both interfacial models and their ability to accurately describe the effects of MAPE addition. The mechanism of formation of the Model I interface and the integrated matrix is outlined based on the chemical reactions that may occur between the various components as a result of hydrogen bond formation or based on the principle of compatibility, resulting from similar polarity. The Model I fracture occurred on the outer surface of the interfacial layer, visually demonstrating the compatibilization effect of MAPE addition.

  9. The effects of Mg addition on the microstructure and mechanical properties of thixoformed Al–5%Si–Cu alloys

    Salleh, M.S., E-mail: shukor@utem.edu.my [Department of Mechanical and Materials Engineering, Faculty of Engineering and Built Environment, Universiti Kebangsaan Malaysia, 43600 Selangor (Malaysia); Department of Manufacturing Process, Faculty of Manufacturing Engineering, Universiti Teknikal Malaysia Melaka, Hang Tuah Jaya, 76100 Durian Tunggal, Melaka (Malaysia); Omar, M.Z., E-mail: zaidi@eng.ukm.my [Department of Mechanical and Materials Engineering, Faculty of Engineering and Built Environment, Universiti Kebangsaan Malaysia, 43600 Selangor (Malaysia); Syarif, J., E-mail: syarif@eng.ukm.my [Department of Mechanical and Materials Engineering, Faculty of Engineering and Built Environment, Universiti Kebangsaan Malaysia, 43600 Selangor (Malaysia)

    2015-02-05

    Highlights: • The average globule size of α-Al decreased when Mg amount is increased. • T6 heat treatment has increased the strength of the thixoformed alloys. • The elongation after T6 heat treatment is even significantly improved. • Thixoformed alloy with high Mg content shows a brittle type fracture. • Thixoformed alloy in T6 condition shows a ductile type fracture. - Abstract: In this study, the effects of different amounts of magnesium (Mg) on the microstructures and tensile properties of thixoformed Al–5%Si–Cu alloys were investigated. Three different alloys containing various amounts of Mg (0.5, 0.8 and 1.2 wt%) were prepared through the cooling slope casting technique, before they were thixoformed using a compression press. Several of the thixoformed samples were then treated with a T6 heat treatment, that is, solution treatment at 525 °C for 8 h, quenching in warm water at 60 °C, followed by aging at 155 °C for 4 h. All of the samples were then characterised by optical microscopy (OM), scanning electron microscopy (SEM) energy dispersive X-ray (EDX) spectroscopy and X-ray diffraction (XRD) analysis as well as by tensile tests. The results revealed that magnesium was able to refine the size of α-Al globules and the eutectic silicon in the samples. It was also observed that a compact π-Al{sub 9}FeMg{sub 3}Si{sub 5} phase was formed when the magnesium content was 0.8 wt% and 1.2 wt%. The mechanical properties of the thixoformed alloys improved significantly after the T6 heat treatment. The highest attainment was recorded by the latter alloy (i.e. with 1.2 wt%Mg) with its ultimate tensile strength (UTS) as high as 306 MPa, yield strength (YS), 264 MPa, and elongation to fracture of 1.8%. The fracture of thixoformed alloy with a low Mg content (0.5 wt%) showed a combination of dimple and cleavage fracture, whereas in the alloy that contained the highest Mg content (1.2 wt%), cleavage fracture was observed.

  10. The effects of Mg addition on the microstructure and mechanical properties of thixoformed Al–5%Si–Cu alloys

    Highlights: • The average globule size of α-Al decreased when Mg amount is increased. • T6 heat treatment has increased the strength of the thixoformed alloys. • The elongation after T6 heat treatment is even significantly improved. • Thixoformed alloy with high Mg content shows a brittle type fracture. • Thixoformed alloy in T6 condition shows a ductile type fracture. - Abstract: In this study, the effects of different amounts of magnesium (Mg) on the microstructures and tensile properties of thixoformed Al–5%Si–Cu alloys were investigated. Three different alloys containing various amounts of Mg (0.5, 0.8 and 1.2 wt%) were prepared through the cooling slope casting technique, before they were thixoformed using a compression press. Several of the thixoformed samples were then treated with a T6 heat treatment, that is, solution treatment at 525 °C for 8 h, quenching in warm water at 60 °C, followed by aging at 155 °C for 4 h. All of the samples were then characterised by optical microscopy (OM), scanning electron microscopy (SEM) energy dispersive X-ray (EDX) spectroscopy and X-ray diffraction (XRD) analysis as well as by tensile tests. The results revealed that magnesium was able to refine the size of α-Al globules and the eutectic silicon in the samples. It was also observed that a compact π-Al9FeMg3Si5 phase was formed when the magnesium content was 0.8 wt% and 1.2 wt%. The mechanical properties of the thixoformed alloys improved significantly after the T6 heat treatment. The highest attainment was recorded by the latter alloy (i.e. with 1.2 wt%Mg) with its ultimate tensile strength (UTS) as high as 306 MPa, yield strength (YS), 264 MPa, and elongation to fracture of 1.8%. The fracture of thixoformed alloy with a low Mg content (0.5 wt%) showed a combination of dimple and cleavage fracture, whereas in the alloy that contained the highest Mg content (1.2 wt%), cleavage fracture was observed

  11. Are interstitial cells of Cajal involved in mechanical stress-induced gene expression and impairment of smooth muscle contractility in bowel obstruction?

    Chester C Wu

    Full Text Available BACKGROUND AND AIMS: The network of interstitial cells of Cajal (ICC is altered in obstructive bowel disorders (OBD. However, whether alteration in ICC network is a cause or consequence of OBD remains unknown. This study tested the hypothesis that mechanical dilation in obstruction disrupts the ICC network and that ICC do not mediate mechanotranscription of COX-2 and impairment of smooth muscle contractility in obstruction. METHODS: Medical-grade silicon bands were wrapped around the distal colon to induce partial obstruction in wild-type and ICC deficient (W/W(v mice. RESULTS: In wild-type mice, colon obstruction led to time-dependent alterations of the ICC network in the proximal colon segment. Although unaffected on days 1 and 3, the ICC density decreased markedly and the network was disrupted on day 7 of obstruction. COX-2 expression increased, and circular muscle contractility decreased significantly in the segment proximal to obstruction. In W/W(v control mice, COX-2 mRNA level was 4.0 (±1.1-fold higher (n=4 and circular muscle contractility was lower than in wild-type control mice. Obstruction further increased COX-2 mRNA level in W/W(v mice to 7.2 (±1.0-fold vs. W/W(v controls [28.8 (±4.1-fold vs. wild-type controls] on day 3. Obstruction further suppressed smooth muscle contractility in W/W(v mice. However, daily administration of COX-2 inhibitor NS-398 significantly improved muscle contractility in both W/W(v sham and obstruction mice. CONCLUSIONS: Lumen dilation disrupts the ICC network. ICC deficiency has limited effect on stretch-induced expression of COX-2 and suppression of smooth muscle contractility in obstruction. Rather, stretch-induced COX-2 plays a critical role in motility dysfunction in partial colon obstruction.

  12. The neuron-astrocyte-microglia triad involvement in neuroinflammaging mechanisms in the CA3 hippocampus of memory-impaired aged rats.

    Lana, Daniele; Iovino, Ludovica; Nosi, Daniele; Wenk, Gary L; Giovannini, Maria Grazia

    2016-10-01

    We examined the effects of inflammaging on memory encoding, and qualitative and quantitative modifications on proinflammatory proteins, apoptosis, neurodegeneration and morphological changes of neuron-astrocyte-microglia triads in CA3 Stratum Pyramidale (SP), Stratum Lucidum (SL) and Stratum Radiatum (SR) of young (3months) and aged rats (20months). Aged rats showed short-term memory impairments in the inhibitory avoidance task, increased expression of iNOS and activation of p38MAPK in SP, increase of apoptotic neurons in SP and of ectopic neurons in SL, and decrease of CA3 pyramidal neurons. The number of astrocytes and their branches length decreased in the three CA3 subregions of aged rats, with morphological signs of clasmatodendrosis. Total and activated microglia increased in the three CA3 subregions of aged rats. In aged rats CA3, astrocytes surrounded ectopic degenerating neurons forming "micro scars" around them. Astrocyte branches infiltrated the neuronal cell body, and, together with activated microglia formed "triads". In the triads, significantly more numerous in CA3 SL and SR of aged rats, astrocytes and microglia cooperated in fragmentation and phagocytosis of ectopic neurons. Inflammaging-induced modifications of astrocytes and microglia in CA3 of aged rats may help clearing neuronal debris derived from low-grade inflammation and apoptosis. These events might be common mechanisms underlying many neurodegenerative processes. The frequency to which they appear might depend upon, or might be the cause of, the burden and severity of neurodegeneration. Targeting the triads may represent a therapeutic strategy which may control inflammatory processes and spread of further cellular damage to neighboring cells. PMID:27466072

  13. Stress impairs the efficacy of immune stimulation by CpG-C: Potential neuroendocrine mediating mechanisms and significance to tumor metastasis and the perioperative period.

    Levi, B; Matzner, P; Goldfarb, Y; Sorski, L; Shaashua, L; Melamed, R; Rosenne, E; Page, G G; Ben-Eliyahu, S

    2016-08-01

    We recently reported that immune stimulation can be compromised if animals are simultaneously subjected to stressful conditions. To test the generalizability of these findings, and to elucidate neuroendocrine mediating mechanisms, we herein employed CpG-C, a novel TLR-9 immune-stimulating agent. Animals were subjected to ongoing stress (20-h of wet cage exposure) during CpG-C treatment, and antagonists to glucocorticoids, β-adrenoceptor, COX2, or opioids were employed (RU486, nadolol, etodolac, naltrexone). In F344 rats, marginating-pulmonary NK cell numbers and cytotoxicity were studied, and the NK-sensitive MADB106 experimental metastasis model was used. In Balb/C mice, experimental hepatic metastases of the CT-26 colon tumor were studied; and in C57BL/6J mice, survival rates following excision of B16 melanoma was assessed - both mouse tumor models involved surgical stress. The findings indicated that simultaneous blockade of glucocorticoid and β-adrenergic receptors improved CpG-C efficacy against MADB106 metastasis. In mice bearing B16 melanoma, long-term survival rate was improved by CpG-C only when employed simultaneously with blockers of glucocorticoids, catecholamines, and prostaglandins. Prolonged stress impaired CpG-C efficacy in potentiating NK activity, and in resisting MADB106 metastasis in both sexes, as also supported by in vitro studies. This latter effect was not blocked by any of the antagonists or by adrenalectomy. In the CT26 model, prolonged stress only partially reduced the efficacy of CpG-C. Overall, our findings indicate that ongoing behavioral stress and surgery can jeopardize immune-stimulatory interventions and abolish their beneficial metastasis-reducing impacts. These findings have implications for the clinical setting, which often involve psychological and physiological stress responses during immune-stimulation. PMID:26944000

  14. Cognitive Impairments Induced by Concussive Mild Traumatic Brain Injury in Mouse Are Ameliorated by Treatment with Phenserine via Multiple Non-Cholinergic and Cholinergic Mechanisms

    Li, Yazhou; Yu, Qian-sheng; Barak, Shani; Tamargo, Ian A.; Rubovitch, Vardit; Holloway, Harold W.; Lehrmann, Elin; Wood, William H.; Zhang, Yongqing; Becker, Kevin G.; Perez, Evelyn; Van Praag, Henriette; Luo, Yu; Hoffer, Barry J.; Becker, Robert E.; Pick, Chaim G.; Greig, Nigel H.

    2016-01-01

    Traumatic brain injury (TBI), often caused by a concussive impact to the head, affects an estimated 1.7 million Americans annually. With no approved drugs, its pharmacological treatment represents a significant and currently unmet medical need. In our prior development of the anti-cholinesterase compound phenserine for the treatment of neurodegenerative disorders, we recognized that it also possesses non-cholinergic actions with clinical potential. Here, we demonstrate neuroprotective actions of phenserine in neuronal cultures challenged with oxidative stress and glutamate excitotoxicity, two insults of relevance to TBI. These actions translated into amelioration of spatial and visual memory impairments in a mouse model of closed head mild TBI (mTBI) two days following cessation of clinically translatable dosing with phenserine (2.5 and 5.0 mg/kg BID x 5 days initiated post mTBI) in the absence of anti-cholinesterase activity. mTBI elevated levels of thiobarbituric acid reactive substances (TBARS), a marker of oxidative stress. Phenserine counteracted this by augmenting homeostatic mechanisms to mitigate oxidative stress, including superoxide dismutase [SOD] 1 and 2, and glutathione peroxidase [GPx], the activity and protein levels of which were measured by specific assays. Microarray analysis of hippocampal gene expression established that large numbers of genes were exclusively regulated by each individual treatment with a substantial number of them co-regulated between groups. Molecular pathways associated with lipid peroxidation were found to be regulated by mTBI, and treatment of mTBI animals with phenserine effectively reversed injury-induced regulations in the ‘Blalock Alzheimer’s Disease Up’ pathway. Together these data suggest that multiple phenserine-associated actions underpin this compound’s ability to ameliorate cognitive deficits caused by mTBI, and support the further evaluation of the compound as a therapeutic for TBI. PMID:27254111

  15. Study of a type AISI 321 austenitic stainless steel with niobium additions, submitted to thermal and mechanical treatments and to fast neutron irradiation

    The strengthening mechanisms and improved corrosion-and swelling resistance of austenitic Ni-Fe-Cr stainless steel by Nb additions are properties of interest in Nuclear Technology. In this work, Nb additions were made in type 321 stainless steel for metallography, microhardness, electrical resistivity and radiation damage studies. The samples were fabricated in induction furnace on water cooled melting-pot in argon atmosphere. This work presents the results of experimental measurements from which an attempt is made to analyse the effects of Nb additions acting as microalloying element and of thermal and mechanical process (cold work in present work) on the microstructure, micorhardness and electrical resistivity properties of the 11%Ni-70%Fe-17%Cr austenitic stainless steel. The study of this properties before, during and after irradiation with fast neutrons, showed: - for the original composition of type 321 stainless steel the radiation damage peak is around 4950C; - the radiation damage peak for the composition with 0.05Wt.% of Nb addition is around 5000C; - the radiation damage peak for the composition with 0.1Wt.% of Nb addition is around 5650C. Results of vacancies supersaturation are present in the sense to contribute to the void formation studies in metals during irradiation with high energy particles. (Author)

  16. Adsorption mechanism and dispersion efficiency of three anionic additives [poly(acrylic acid), poly(styrene sulfonate) and HEDP] on zinc oxide.

    Dange, C; Phan, T N T; André, V; Rieger, J; Persello, J; Foissy, A

    2007-11-01

    Adsorption on ZnO of sodium poly(acrylate) (PAA), sodium poly(styrene sulfonate) (PSS) and a monomer surfactant [hydroxyethylidene diphosphonate (HEDP)] was investigated in suspensions initially equilibrated at pH 7. Results demonstrate interplay in the adsorption mechanism between zinc complexation, salt precipitation, and ZnO dissolution. In the case of PAA, the adsorption isotherm exhibits a maximum attributed to the precipitation of zinc polyacrylate. PSS and HEDP formed high-affinity adsorption isotherms, but the plateau adsorption of HEDP was significantly lower than that of PSS. The adsorption isotherm of each additive is divided into two areas. At low additive concentration (high zinc/additive ratio), the total zinc concentration in the solution decreased and the pH increased upon addition. At a higher additive ratio, zinc concentration and pH increased with the organic concentration. The increase in pH is due to the displacement of hydroxyl ions from the surface and the increase in zinc concentration results from the dissolution of ZnO due to the complexation of zinc ions by the organics. The stability of the ZnO dispersions was investigated by measurement of the particle size distribution after addition of various amounts of polymers. The three additives stabilized the ZnO dispersions efficiently once full surface coverage was reached. PMID:17720181

  17. Cognitive training with and without additional physical activity in healthy older adults: cognitive effects, neurobiological mechanisms, and prediction of training success

    Julia eRahe; Jutta eBecker; Fink, Gereon R.; Josef eKessler; Juraj eKukolja; Andreas eRahn; Rosen, Jan B.; Florian eSzabados; Brunhilde eWirth; Elke eKalbe

    2015-01-01

    Data is inconsistent concerning the question whether cognitive-physical training (CPT) yields stronger cognitive gains than cognitive training (CT). Effects of additional counseling, neurobiological mechanisms, and predictors have scarcely been studied. Healthy older adults were trained with CT (n = 20), CPT (n = 25), or CPT with counseling (CPT+C; n = 23). Cognition, physical fitness, BDNF, IGF-1, and VEGF were assessed at pre- and post-test. No interaction effects were found except for one ...

  18. Impaired Consciousness in Epilepsy

    Blumenfeld, Hal

    2012-01-01

    Consciousness is essential to normal human life. In epileptic seizures consciousness is often transiently lost making it impossible for the individual to experience or respond. This has huge consequences for safety, productivity, emotional health and quality of life. To prevent impaired consciousness in epilepsy it is necessary to understand the mechanisms leading to brain dysfunction during seizures. Normally the “consciousness system”—a specialized set of cortical-subcortical structures—mai...

  19. Sleep, Torpor and Memory Impairment

    Palchykova, S.; Tobler, I.

    It is now well known that daily torpor induces a sleep deficit. Djungarian hamsters emerging from this hypometabolic state spend most of the time in sleep. This sleep is characterized by high initial values of EEG slow-wave activity (SWA) that monotonically decline during recovery sleep. These features resemble the changes seen in numerous species during recovery after prolonged wakefulness or sleep deprivation (SD). When hamsters are totally or partially sleep deprived immediately after emerging from torpor, an additional increase in SWA can be induced. It has been therefore postulated, that these slow- waves are homeostatically regulated, as predicted by the two-process model of sleep regulation, and that during daily torpor a sleep deficit is accumulated as it is during prolonged waking. The predominance of SWA in the frontal EEG observed both after SD and daily torpor provides further evidence for the similarity of these conditions. It has been shown in several animal and human studies that sleep can enhance memory consolidation, and that SD leads to memory impairment. Preliminary data obtained in the Djungarian hamster showed that both SD and daily torpor result in object recognition deficits. Thus, animals subjected to SD immediately after learning, or if they underwent an episode of daily torpor between learning and retention, displayed impaired recognition memory for complex object scenes. The investigation of daily torpor can reveal mechanisms that could have important implications for hypometabolic state induction in other mammalian species, including humans.

  20. Preparation and characterization of new dental porcelains, using K-feldspar and quartz raw materials. Effect of B2O3 additions on sintering and mechanical properties.

    Harabi, Abdelhamid; Guerfa, Fatiha; Harabi, Esma; Benhassine, Mohamed-Tayeb; Foughali, Lazhar; Zaiou, Soumia

    2016-08-01

    The aim of this work was to determine the effect of temperature and boric oxide (B2O3) addition on sintering and mechanical properties of a newly developed dental porcelain (DP) prepared from local Algerian raw materials. Based on a preliminary work, the new selected composition was 75wt.% feldspar, 20wt.% quartz and 5wt.% kaolin. It was prepared by sintering the mixture at different temperatures (1100-1250°C). The optimum sintering conditions gave a relatively higher density (2.47g/cm(3)) and excellent mechanical properties. The three point flexural strength (3PFS) and Martens micro-hardness of dental porcelains were 149MPa and 2600MPa, respectively. This obtained 3PFS value is more than four times greater than that of hydroxyapatite (HA) value (about 37MPa) sintered under the same conditions. However, the sintering temperature was lowered by about 25 and 50°C for 3 and 5wt.% B2O3 additions, respectively. But, it did not improve furthermore the samples density and their mechanical properties. It has also been found that B2O3 additions provoke a glass matrix composition variation which delays the leucite formation during sintering. PMID:27157725

  1. Numerical investigation of the mechanical properties of the additive manufactured bone scaffolds fabricated by FDM: The effect of layer penetration and post-heating.

    Naghieh, S; Karamooz Ravari, M R; Badrossamay, M; Foroozmehr, E; Kadkhodaei, M

    2016-06-01

    In recent years, thanks to additive manufacturing technology, researchers have gone towards the optimization of bone scaffolds for the bone reconstruction. Bone scaffolds should have appropriate biological as well as mechanical properties in order to play a decisive role in bone healing. Since the fabrication of scaffolds is time consuming and expensive, numerical methods are often utilized to simulate their mechanical properties in order to find a nearly optimum one. Finite element analysis is one of the most common numerical methods that is used in this regard. In this paper, a parametric finite element model is developed to assess the effects of layers penetration׳s effect on inter-layer adhesion, which is reflected on the mechanical properties of bone scaffolds. To be able to validate this model, some compression test specimens as well as bone scaffolds are fabricated with biocompatible and biodegradable poly lactic acid using fused deposition modeling. All these specimens are tested in compression and their elastic modulus is obtained. Using the material parameters of the compression test specimens, the finite element analysis of the bone scaffold is performed. The obtained elastic modulus is compared with experiment indicating a good agreement. Accordingly, the proposed finite element model is able to predict the mechanical behavior of fabricated bone scaffolds accurately. In addition, the effect of post-heating of bone scaffolds on their elastic modulus is investigated. The results demonstrate that the numerically predicted elastic modulus of scaffold is closer to experimental outcomes in comparison with as-built samples. PMID:26874065

  2. Parkinson's disease associated with impaired oxidative phosphorylation

    Parkinson's disease may be due to primary or secondary oxidative phosphorylation (OXPHOS) defects. In a 76-year-old man with Parkinson's disease since 1992, slightly but recurrently elevated creatine phosphokinase, recurrently elevated blood glucose, thickening of the left ventricular myocardium, bifascicular block and hypacusis were found. Cerebral MRI showed atrophy, periventricular demyelination, multiple, disseminated, supra- and infratentorial lacunas, and haemosiderin deposits in both posterior horns. Muscle biopsy showed typical features of an OXPHOS defect. Whether the association of Parkinson's disease and impaired OXPHOS was causative or coincidental remains unknown. Possibly, the mitochondrial defect acted as an additional risk factor for Parkinson's disease or the OXPHOS defect worsened the preexisting neurological impairments by a cumulative or synergistic mechanism. In conclusion, this case shows that Parkinson's disease may be associated with a mitochondrially or nuclearly encoded OXPHOS defect, manifesting as hypacusis, myopathy, axonal polyneuropathy, cardiomyopathy and recurrent subclinical ischaemic strokes and haemorrhages. (orig.)

  3. A Research into Cell Protection and Mechanism of Zengyetang on Acute Impairment of Yin Amimal Models%增液汤对急性伤阴动物模型的细胞保护作用及其机理探讨

    仝小林; 王君; 李宁; 王红; 曹丽英; 叶智文

    2003-01-01

    Acute Yin impairment is a frequently occurring clinic syndrome. We suggest the process of acute Yin impairment be divided into two stages, namely early impairment of lung and stomach fluid and later Yin impairment of liver and kidney. This work aims to research into the cell-protecting mechanism of Zengyetang, from the angle of protecting cells, change of inner and outer fluid ion of cells, change of enzyme of cell membrane, free radical impairment, appoptosis and gene expression. The study, taking inner and outer fluid ion of cells as objective indicators,also researches into dynamic change of inner and outer fluid of cells in the different stages of Yin impairment development on the animal models of yin impairment by fever and poison. Zengyetang is one of the typical Yin-nourishing prescriptions, gengyetang is made into injection in accordance with the rate of the original prescription. This work researches into the affects of Zengyetang on the four types of acute Yin impairment animal models, including Yin impairment model by pathogenic heat, Yin impairment model by summer heat and sweat, Yin impairment model by high-infiltration Yin impairment and Yin impairment by drugs and toxin. Main experiment results show: 1. in early stage,pathogenic heat Yin impairment impairs outer liquid of cells; 2. Zengyetang has the function of adjusting disorder of inner and outer fluid of red cells; 3. Zengyetang has the function of protecting enzyme activity of cell membrane and maintaining normal operation of red cell ion; 4. Zengyetang can protect liver cells of rabbits through resisting free radical impairment and lessen thymocyte apoptosis of young rat resulted from glucocorticoid.

  4. Effect of additive V2O5 on sintering mechanism and properties of inert anodes of NiFe2O4 spinel

    2005-01-01

    In order to improve the properties of inert anode of NiFe2O4 spinel, some additive V2O5 was added to raw materials-powders of NiO and Fe2O3. The powders of NiO, Fe2O3 were mixed with slight amount of V2O5, then they are moulded and sintered at 1200℃ for 6h. The sintering mechanism of powders of NiO and Fe2O3 with some additive V2 O5 was researched. The effect of V2O5 on density, electrical conductivity and corrosion resistance of inert anode of NiFe2O4 spinel was studied at the same time. The results show that the sintering mechanism for powders of NiO and Fe2O3 with some additive V2O5 is liquid-phase sintering. Additive V2O5 can increase the density of the samples, especially it improves the corrosion resistance of the samples remarkably. When the amount of V2 O5 is 1.5 %, the sample's corrosion rate is 1/80 of that of sample without V2 O5. But the electrical conductivity of the samples with V2O5 is lower than that of the sample without V2O5.

  5. Formation of novel flower-like silicon phases and evaluation of mechanical properties of hypereutectic melt-spun Al–20Si–5Fe alloys with addition of V

    Uzun, Orhan [Department of Metallurgical and Material Science Engineering, Bülent Ecevit University, Zonguldak (Turkey); Kilicaslan, Muhammed Fatih, E-mail: fatihkilicaslan@yahoo.com [Department of Materials and Nanotechnology Engineering, Kastamonu University, Kastamonu (Turkey); Yılmaz, Fikret [Department of Physics, Gaziosmanpaşa University, Tokat (Turkey)

    2014-06-01

    In this work, rapidly solidified hypereutectic Al–20Si–5Fe–XV (X=0, 0.5 and 1) alloys were fabricated by melt spinning under vacuum. Microstructural and spectroscopic analyses were performed using SEM, TEM, TEM-MAPing, TEM-EDS and XRD measurements. Mechanical properties of the alloys were determined using DSI measurements. Experimental results indicated that addition of 0.5 wt% V to melt-spun Al–20Si–5Fe alloys induced formation of a novel flower-like Si phase. And addition of higher amount V (1 wt%), caused formation of refined Si phases and mostly hindered formation of Fe-bearing intermetallics. Observations along with manuscript strongly indicate that V modifies the Si phases by the impurity induced twinning (IIT). Changes in the dynamic microhardness of the samples were mainly determined by the size of Si phases. Addition of vanadium led to quite lower elastic modulus in the vanadium added alloys compared to base alloy.

  6. Role of enzymatic activity in muscle damage and cytotoxicity induced by Bothrops asper Asp49 phospholipase A2 myotoxins: are there additional effector mechanisms involved?

    Diana Mora-Obando

    2014-09-01

    Full Text Available Viperid venoms often contain mixtures of Asp49 and Lys49 PLA2 myotoxin isoforms, relevant to development of myonecrosis. Given their difference in catalytic activity, mechanistic studies on each type require highly purified samples. Studies on Asp49 PLA2s have shown that enzyme inactivation using p-bromophenacyl bromide (p-BPB drastically affects toxicity. However, based on the variable levels of residual toxicity observed in some studies, it has been suggested that effector mechanisms independent of catalysis may additionally be involved in the toxicity of these enzymes, possibly resembling those of the enzymatically inactive Lys49 myotoxins. A possibility that Lys49 isoforms could be present in Asp49 PLA2 preparations exists and, if undetected in previous studies, could explain the variable residual toxicity. This question is here addressed by using an enzyme preparation ascertained to be free of Lys49 myotoxins. In agreement with previous reports, inactivation of the catalytic activity of an Asp49 myotoxin preparation led to major inhibition of toxic effects in vitro and in vivo. The very low residual levels of myotoxicity (7% and cytotoxicity (4% observed can be attributed to the low, although detectable, enzyme remaining active after p-BPB treatment (2.7%, and would be difficult to reconcile with the proposed existence of additional catalytic-independent toxic mechanisms. These findings favor the concept that the effector mechanism of toxicity of Asp49 PLA2 myotoxins from viperids fundamentally relies on their ability to hydrolyze phospholipids, arguing against the proposal that membrane disruption may also be caused by additional mechanisms that are independent of catalysis.

  7. The effect of location on the microstructure and mechanical properties of titanium aluminides produced by additive layer manufacturing using in-situ alloying and gas tungsten arc welding

    An innovative and low cost additive layer manufacturing (ALM) process is used to produce γ-TiAl based alloy wall components. Gas tungsten arc welding (GTAW) provides the heat source for this new approach, combined with in-situ alloying through separate feeding of commercially pure Ti and Al wires into the weld pool. This paper investigates the morphology, microstructure and mechanical properties of the additively manufactured TiAl material, and how these are affected by the location within the manufactured component. The typical additively layer manufactured morphology exhibits epitaxial growth of columnar grains and several layer bands. The fabricated γ-TiAl based alloy consists of comparatively large α2 grains in the near-substrate region, fully lamellar colonies with various sizes and interdendritic γ structure in the intermediate layer bands, followed by fine dendrites and interdendritic γ phases in the top region. Microhardness measurements and tensile testing results indicated relatively homogeneous mechanical characteristics throughout the deposited material. The exception to this homogeneity occurs in the near-substrate region immediately adjacent to the pure Ti substrate used in these experiments, where the alloying process is not as well controlled as in the higher regions. The tensile properties are also different for the vertical (build) direction and horizontal (travel) direction because of the differing microstructure in each direction. The microstructure variation and strengthening mechanisms resulting from the new manufacturing approach are analysed in detail. The results demonstrate the potential to produce full density titanium aluminide components directly using the new additive layer manufacturing method

  8. Effect of ZrO{sub 2} addition on the mechanical properties of porous TiO{sub 2} bone scaffolds

    Tiainen, Hanna [Department of Biomaterials, Institute for Clinical Dentistry, University of Oslo, PO Box 1109 Blindern, NO-0317 Oslo (Norway); Eder, Georg [Department of Biomaterials, Institute for Clinical Dentistry, University of Oslo, PO Box 1109 Blindern, NO-0317 Oslo (Norway); Institute of Medical and Polymer Engineering, Chair of Medical Engineering, Technische Universitaet Muenchen, Boltzmannstrasse 15, 85748 Garching (Germany); Nilsen, Ola [Department of Chemistry, University of Oslo, PO Box 1033 Blindern, NO-0315 Oslo (Norway); Haugen, Havard J., E-mail: h.j.haugen@odont.uio.no [Department of Biomaterials, Institute for Clinical Dentistry, University of Oslo, PO Box 1109 Blindern, NO-0317 Oslo (Norway)

    2012-08-01

    This study aimed at the investigation of the effect of zirconium dioxide (ZrO{sub 2}) addition on the mechanical properties of titanium dioxide (TiO{sub 2}) bone scaffolds. The highly biocompatible TiO{sub 2} has been identified as a promising material for bone scaffolds, whereas the more bioinert ZrO{sub 2} is known for its excellent mechanical properties. Ultra-porous TiO{sub 2} scaffolds (> 89% porosity) were produced using polymer sponge replication with 0-40 wt.% of the TiO{sub 2} raw material substituted with ZrO{sub 2}. 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 ZrO{sub 2} led to 16% increase in the mean compressive strength without significant changes in the pore architectural parameters of TiO{sub 2} scaffolds. Further ZrO{sub 2} additions resulted in reduction of compressive strength in comparison to containing no ZrO{sub 2}. The appearance of zirconium titanate (ZrTiO{sub 4}) 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: Black-Right-Pointing-Pointer Open porous scaffold with porosity in the range of 89.0 to 92.8% produced. Black-Right-Pointing-Pointer Adding 1 wt.% of ZrO{sub 2} led to 16% increase in strength without changing porosity. Black-Right-Pointing-Pointer Further ZrO{sub 2} additions resulted in reduced compressive strength versus no ZrO{sub 2}. Black-Right-Pointing-Pointer Presence of zirconium titanate (ZrTiO{sub 4}) phase found to hinder the densification. Black-Right-Pointing-Pointer Appearance of ZrTiO{sub 4} resulted in poor intergranular connections.

  9. Investigating the addition of SiO₂-CaO-ZnO-Na₂O-TiO₂ bioactive glass to hydroxyapatite: Characterization, mechanical properties and bioactivity.

    Yatongchai, Chokchai; Placek, Lana M; Curran, Declan J; Towler, Mark R; Wren, Anthony W

    2015-11-01

    Hydroxyapatite (Ca10(PO4)6(OH)2) is widely investigated as an implantable material for hard tissue restoration due to its osteoconductive properties. However, hydroxyapatite in bulk form is limited as its mechanical properties are insufficient for load-bearing orthopedic applications. Attempts have been made to improve the mechanical properties of hydroxyapatite, by incorporating ceramic fillers, but the resultant composite materials require high sintering temperatures to facilitate densification, leading to the decomposition of hydroxyapatite into tricalcium phosphate, tetra-calcium phosphate and CaO phases. One method of improving the properties of hydroxyapatite is to incorporate bioactive glass particles as a second phase. These typically have lower softening points which could possibly facilitate sintering at lower temperatures. In this work, a bioactive glass (SiO2-CaO-ZnO-Na2O-TiO2) is incorporated (10, 20 and 30 wt%) into hydroxyapatite as a reinforcing phase. X-ray diffraction confirmed that no additional phases (other than hydroxyapatite) were formed at a sintering temperature of 560 ℃ with up to 30 wt% glass addition. The addition of the glass phase increased the % crystallinity and the relative density of the composites. The biaxial flexural strength increased to 36 MPa with glass addition, and there was no significant change in hardness as a function of maturation. The pH of the incubation media increased to pH 10 or 11 through glass addition, and ion release profiles determined that Si, Na and P were released from the composites. Calcium phosphate precipitation was encouraged in simulated body fluid with the incorporation of the bioactive glass phase, and cell culture testing in MC-3T3 osteoblasts determined that the composite materials did not significantly reduce cell viability. PMID:26116020

  10. A study on the effects of aging treatment and W addition on the mechanical properties and sensitization behaviors of Fe-Cr-Mn stainless steels

    The characteristics of the mechanical properties and sensitization behaviors in Fe-Cr-Mn stainless steels by W addition and aging treatment were studied. Yield strength, tensile strength, elongation and impact energy were decreased, and hardness was slightly increased by aging treatment. W-containing alloys showed especially a larger degree of brittle characteristics due to the hard chi(χ) phase formed from the decomposition of ferrite. Carbides precipitated in grain boundary had a bad effect on impact energy rather than strength and hardness. Ni addition suppressed the formation of ferrite and resulted in the some improvement of mechanical properties. Anodic polarization tests showed that the corrosion resistance of aged alloys was decreased by the formation of carbides and secondary austenites. It was observed that W addition made no improvement of the pitting potential and passive current density of aged alloys in the HCl solution. But Ni and W decreased critical current density in the sulfuric acid and made easier formation of passive film, contributing to corrosion resistance. From the results of EPR (Electrochemical Potentiokinetic Reactivation), DOS (Degree of Sensitization) was increased with aging time and carbides and ferrite was preferentially attacked. It was observed that Ni delayed the sensitization. It can be concluded from the previous results that the selective dissolution of ferrite is due to the ferrite decomposition to chi (χ) phase and secondary austenites. In the secondary austenite Cr and W which are known to improve the corrosion resistance were depleted. Therefore, it seems that ferrite phase became sensitive to corrosion

  11. Effects of Aging and W Addition on the Corrosion Resistance and Mechanical Properties of Fe-Cr-Mn-N Stainless Steels

    The characteristics of the mechanical properties and sensitization behaviors in Fe-Cr-Mn stainless steels by W addition and aging treatment were studied. Yield strength, tensile strength, elongation and impact energy decreased, and hardness increased slightly by aging treatment. W-containing alloys showed especially a larger degree of brittle characteristics due to the hard chi(χ) phase formed from the decomposition of ferrite. Carbides precipitated in grain boundary had a bad effect on impact energy rather than on strength and hardness. Ni addition suppressed the formation of ferrite and resulted in some improvement of mechanical properties. Anodic polarization tests showed that the corrosion resistance of aged alloys decreased by the formation of carbides and secondary austenite. It was observed that W addition made no improvement of the pitting potential and passive current density of aged alloys in the HCI solution. But Ni and W decreased critical current density in the sulfuric acid and made easier formation of passive film, contributing to corrosion resistance. From the results of EPR (Electrochemical Potentiokinetic Reactivation). DOS (Degree of Sensitization) increased with aging time and carbides and ferrite were preferentially attacked. It was observed that Ni delayed the sensitization. It can be concluded from the previous results that the selective dissolution of ferrite is due to the ferrite decomposition to chi (χ) phase and secondary austenite. In the secondary austenite. Cr and W which are known to improve the corrosion resistance were depleted. Therefore, it seems that ferrite phase became sensitive to corrosion

  12. Systems analysis of human brain gene expression: mechanisms for HIV-associated neurocognitive impairment and common pathways with Alzheimer’s disease

    Levine, Andrew J.; Miller, Jeremy A.; Shapshak, Paul; Gelman, Benjamin; Singer, Elyse J.; Hinkin, Charles H.; Commins, Deborah; Morgello, Susan; Grant, Igor; Horvath, Steve

    2013-01-01

    Abstract Background Human Immunodeficiency Virus-1 (HIV) infection frequently results in neurocognitive impairment. While the cause remains unclear, recent gene expression studies have identified genes whose transcription is dysregulated in individuals with HIV-association neurocognitive disorder (HAND). However, the methods for interpretation of such data have lagged behind the technical advances allowing the decoding genetic material. Here,...

  13. The effects of small titanium additions on the mechanical properties and the microstructures of controlled rolled niobium-bearing HSLA plate steels

    He Kejian (Univ. of Strathclyde, Glasgow (United Kingdom)); Baker, T.N. (Univ. of Strathclyde, Glasgow (United Kingdom))

    1993-09-15

    Effects of small Ti additions (0.010, 0.022%) on mechanical properties and microstructures of Nb-bearing HSLA plate steels under two different rolling schedules were investigated. For comparison, a Ti-free steel was controlled rolled to 814 C. A side effect of the Ti additions was observed on strength of Nb-bearing steels. The lower yield stress values and hardness levels for all Ti-Nb steels were reduced both in as-rolled and normalized conditions, depending on Ti/N ratio and details of thermomechanical process. However, the Ti-Nb steels with a lower finish rolling temperature (FRT), 800 C, showed better toughness than the Ti-free control steel. For Ti-Nb steels, toughness was improved significantly by lowering the FRT from 940 to 800 C, owing mainly to considerable refinement of ferrite grain sizes and fewer fine carbides available for dispersion hardening. No advantages were observed for over-stoichiometric Ti addition (Ti/N=4.4). The steel with under-stoichiometric Ti addition (Ti/N = 2) and a lower FRT (800 C) showed best overall mechanical and toughness properties among all processed Ti-Nb steels. Precipitation of Nb nitrides and carbides in the Nb steels was changed by Ti additions which led to formation of complex Ti-Nb nitrides and carbonitrides, i.e. Ti-rich plates and cuboids. Moreover, these plates and cuboids acted as nucleating cores on which pure carbides formed, i.e. Nb carbide in 0.01%Ti steels whereas Nb-rich Ti-Nb carbide in 0.022%Ti steels. In as-rolled samples, no Al was found in the complex particles or as individual AlN while in the normalized condition, fine AlN precipitates were detected frequently with understoichiometric titanium addition (0.01%Ti), whereas formation of AlN was suppressed by the over-stoichiometric Ti addition (in 0.022%Ti). The Ti/N ratio, therefore, has a strong influence on type of precipitation and size.

  14. Effect of Addition of Plants-Derived Polyamide 11 Elastomer on the Mechanical and Tribological Properties of Hemp Fiber Reinforced Polyamide 1010 Composites

    Mukaida, Jun; Nishitani, Yosuke; Kitano, Takeshi

    2015-01-01

    For the purpose of developing the new engineering materials such as structural materials and tribomaterials based on all plants-derived materials, the effect of the addition of plant-derived polyamide 11 Elastomer (PA11E) on the mechanical and tribological properties of hemp fiber(HF) reinforced polyamide 1010 (HF/PA1010) composites was investigated. PA1010 and PA11E (except the polyether groups used as soft segment) were made from plant-derived castor oil. Hemp fiber was surface-treated by t...

  15. Effect of electron beam irradiation and poly(vinylpyrrolidone addition on mechanical properties of polycaprolactone with empty fruit bunch fibre (OPEFB composite

    2009-04-01

    Full Text Available Biodegradable composites or green composites were prepared by melt blending technique using polycaprolactone and oil palm empty fruit bunch fibre (OPEFB. Since OPEFB is not compatible with PCL a binder, poly(vinyl pyrrolidone, (PVP was used to improve the interaction between PCL and OPEFB. The composites produced were irradiated using electron beam to improve the mechanical properties. The tensile, flexural and impact strengths of PCL/OPEFB composites were improved by addition of 1% by weight of PVP and irradiated with 10 kGy of electron beam. The FTIR spectra indicate a slight increase of frequencies at C=O peaks from 1730 to 1732 cm–1 after irradiation indicates some interaction between C=O and O–H. The surface morphology of the facture surface obtained from tensile test shows no fibre pull out indicating good adhesion between the OPEFB and PCL after addition of PVP.

  16. The mechanism by which P250L mutation impairs flavivirus-NS1 dimerization: an investigation based on molecular dynamics simulations.

    Oliveira, Edson R A; de Alencastro, Ricardo B; Horta, Bruno A C

    2016-09-01

    The flavivirus non-structural protein 1 (NS1) is a conserved glycoprotein with as yet undefined biological function. This protein dimerizes when inside infected cells or associated to cell membranes but also forms lipid-associated hexamers when secreted to the extracellular space. A single amino acid substitution (P250L) is capable of preventing the dimerization of NS1 resulting in lower virulence and slower virus replication. In this work, based on molecular dynamics simulations of the dengue-2 virus NS1 [Formula: see text]-ladder monomer as a core model, we found that this mutation can induce several conformational changes that importantly affect critical monomer-monomer interactions. Based on additional simulations, we suggest a mechanism by which a highly orchestrated sequence of events propagate the local perturbations around the mutation site towards the dimer interface. The elucidation of such a mechanism could potentially support new strategies for rational production of live-attenuated vaccines and highlights a step forward in the development of novel anti-flavivirus measures. PMID:27324799

  17. Mechanisms of Vanadium Recovery from Stone Coal by Novel BaCO3/CaO Composite Additive Roasting and Acid Leaching Technology

    Zhenlei Cai

    2016-03-01

    Full Text Available In this report, the vanadium recovery mechanisms by novel BaCO3/CaO composite additive roasting and acid leaching technology, including the phase transformations and the vanadium leaching kinetics, were studied. The purpose of this manuscript is to realize and improve the vanadium recovery from stone coal using BaCO3/CaO as the composite additive. The results indicated that during the composite additive BaCO3/CaO roasting process, the monoclinic crystalline structure of muscovite (K(Al,V2[Si3AlO10](OH2 was converted into the hexagonal crystalline structure of BaSi4O9 and the tetragonal crystalline structure of Gehlenite (Ca2Al2SiO7, which could, therefore, facilitate the release and extraction of vanadium. Vanadium in leaching residue was probably in the form of vanadate or pyrovanadate of barium and calcium, which were hardly extracted during the sulfuric acid leaching process. The vanadium leaching kinetic analysis indicated that the leaching process was controlled by the diffusion through a product layer. The apparent activation energy could be achieved as 46.51 kJ/mol. The reaction order with respect to the sulfuric acid concentration was 1.1059. The kinetic model of vanadium recovery from stone coal using novel composite additive BaCO3/CaO could be finally established.

  18. Effects of Ti and B Addition on Microstructures and Mechanical Properties of Hot-Rolled High-Strength Nb-Containing Steels

    Meng, Xianna; Li, Cong; Chen, Wanglin

    2016-06-01

    Four microalloyed samples were designed to study the effects of Ti and B additions on microstructures and mechanical properties. Experimental results show that the samples without B addition mainly contain well-developed pearlite and polygonal ferrite, whereas the B-containing samples consist of degenerated pearlite, polygonal ferrite, and Widmanstätten ferrite (WF). The B addition promotes the precipitation of the complex (Ti,Al,Nb)N and (Ti,Al,Nb)2CS phases during the hot-rolling process. Grain sizes are significantly refined by the combinations of undissolved (Ti,Al)N, (Ti,Al,Nb)N complex, (Ti,Al,Nb)2CS, and fine inclusions, which act as the nucleation sites of intragranular ferrite. The core of complex (Ti,Al,Nb)N precipitate is undissolved Ti-N-rich (Ti,Al)N phase, and the cap is Nb-N-rich (Nb,Ti)N phase. The property measurements show that the B addition enhances comprehensive properties of tensile strength and elongation, but decreases fracture toughness due to higher contents of the WF and subgrains.

  19. Multi-walled carbon nanotube filled polypropylene nanocomposites based on masterbatch route: Improvement of dispersion and mechanical properties through PP-g-MA addition

    2008-10-01

    Full Text Available Multi-wall carbon nanotubes (MWNTs filled polypropylene (PP nanocomposites were prepared through diluting a PP/MWNT masterbatch in a PP matrix by melt compounding with a twin screw extruder. Polypropylene grafted maleic anhydride (PP-g-MA was used to promote the carbon nanotubes dispersion. The effect of PP-g-MA addition on the rheological, mechanical and morphological properties of the nanocomposites was assessed for different MWNTs loadings. Scanning electron microscopy (SEM has shown that nanotubes are distributed reasonably uniformly. A better dispersion and good adhesion between the nanotubes and the PP matrix is caused by wrapping of PP-g-MA on MWNTs. When PP-g-MA is added, dynamic moduli and viscosity further increases compared to PP/MWNT nanocomposites. The rheological percolation threshold drops significantly. Tensile and flexural moduli and Charpy impact resistance of the nanocomposites also increases by the addition of PP-g-MA. The present study confirms that PP-g-MA is efficient to promote the dispersion of MWNTs in PP matrix and serves as an adhesive to increase their interfacial strength, hence greatly improving the rheological percolation threshold and mechanical properties of PP/MWNT nanocomposites.

  20. Influence of Ti addition and sintering method on microstructure and mechanical behavior of a medium-entropy Al0.6CoNiFe alloy

    The influence of Ti addition and sintering method on the microstructure and mechanical behavior of a medium-entropy alloy, Al0.6CoNiFe alloy, was studied in detail. Alloying behavior, microstructure, phase evolution and mechanical properties of Al0.6CoNiFe and Ti0.4Al0.6CoNiFe alloys were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM), as well as by mechanical testing. During the mechanical alloying (MA) process, a supersaturated solid solution consisting of both BCC and FCC phases was formed in the Al0.6CoNiFe alloy. With Ti addition, the Ti0.4Al0.6CoNiFe alloy exhibited a supersaturated solid solution with a single FCC phase. Following hot pressing (HP), the HP sintered (HP’ed) Al0.6CoNiFe bulk alloy was composed of a major BCC phase and a minor FCC phase. The HP’ed Ti0.4Al0.6CoNiFe alloy exhibited a FCC phase, two BCC phases and a trace unidentified phase. Nanoscale twins were present in the HP’ed Ti0.4Al0.6CoNiFe alloy, where deformation twins were observed in the FCC phase. Our results suggest that the addition of Ti facilitated the formation of nanoscale twins. The compressive strength and Vickers hardness of HP’ed Ti0.4Al0.6CoNiFe alloy were slightly lower than the corresponding values of the HP’ed Al0.6CoNiFe alloy. In contrast with HP’ed Al0.6CoNiFe alloy, spark plasma sintered (SPS’ed) Al0.6CoNiFe alloy exhibited a major FCC phase and a minor BCC phase. Moreover, the SPS’ed Al0.6CoNiFe alloy exhibited a lower compressive strength and Vickers hardness, but singificantly higher plasticity, as compared to those of the HP’ed counterpart material

  1. Influence of Silver nanoparticles addition on the phase transformation, mechanical properties and corrosion behaviour of Cu–Al–Ni shape memory alloys

    Highlights: • Thermal analysis showed four different phase β, α, NiAl and γ2 during solidification. • The martensite appeared in the microstructure as a plate and needle like shape. • Shape recovery ratio of 80% was obtained after Ag nanoparticles addition. • Effect of Ag nanoparticles on the corrosion behaviour of Cu–Al–Ni SMA was investigated. - Abstract: Incorporation of silver nanoparticles into Cu-based shape memory alloys is recommended to enhance their phase transformation behaviour. However, this incorporation can affect their transformation temperatures, mechanical, microstructural and corrosion characteristics. Four different phase reactions β, α, NiAl and γ2 were detected on a derivative curve during the solidification by-computer-aided cooling curve thermal analysis. The highest fraction solid (82%) was calculated for the parent phase (β) based on the Newtonian baseline method. The microstructural changes and mechanical properties were investigated using field emission scanning electron microscopy, X-ray diffraction tensile test and shape memory effect test. It was found that the addition of Ag can control the phase morphology and orientations along with the formation of the Ag-rich precipitates, and thus the tensile strength, elongation, fracture stress–strain, yield strength and shape memory effect are improved. Remarkably, the shape recovery ratio reached approximately 80% of the original shape. The corrosion behaviour of the Cu–Al–Ni shape memory alloy were investigated using electrochemical tests in NaCl solution and their results showed that the corrosion potential (Ecorr) of Cu–Al–Ni SMA is shifted towards the nobler direction from −307.4 to −277.1 m VSCE with the addition of 0.25 wt.% Ag

  2. Effects of thermo-mechanical processing and trace amount of carbon addition on tensile properties of Cu-2.5Fe-0.1P alloys

    The effects of thermo-mechanical processing, including intermediate aging treatment and/or solution heat treatment, and a trace amount of carbon (C) addition were studied on tensile behavior of Cu-2.5Fe-0.1P alloys. In this study, Cu-2.5Fe-0.1P alloy sheets without and with a carbon content of 0.05 wt.% were cast and subsequently rolled and thermo-mechanically treated following various processing routes. The introduction of intermediate aging treatment between cold rolling improved the tensile strength of Cu-2.5Fe-0.1P alloys. Solution heat treatment prior to aging was proved to be detrimental on the tensile strength, probably due to recovery and recrystallization causing the complete loss of work hardening during previous cold rolling. The present study also suggested that two-step aging is more effective in improving the strength of Cu-2.5Fe-0.1P alloys than one-step aging. The effect of C addition on improving the tensile strength of Cu-2.5Fe-0.1P alloys was real but marginal, probably due to the limited solubility of C in Cu-2.5Fe matrix. The effects of intermediate heat treatments between cold-rolling processes on tensile properties of Cu-2.5Fe-0.1P specimens with and without C addition are discussed based on optical, scanning electron microscope (SEM) and transmission electron microscope (TEM) micrographs, and SEM fractographs.

  3. Effect of minor addition of vanadium on mechanical properties and microstructures of as-extruded near eutectic Al–Si–Mg alloy

    Wu, Yuna; Liao, Hengcheng, E-mail: hengchengliao@seu.edu.cn; Zhou, Kexin

    2014-04-01

    Mechanical properties of near eutectic Al–12.5 wt%Si–0.6 wt%Mg alloys with and without addition of V were tested. Results show that addition of 0.1 wt% V only has a minor influence on the tensile properties of near eutectic Al–Si–Mg alloy in as-cast and as-homogenized conditions. However, it can significantly improve the tensile properties in as-extruded condition. The YS is enhanced nearly 50% and the elongation can reach 14%. Three factors that may contribute to the enhancement of YS were analyzed by EBSD, XRD and TEM investigation, i.e. Δσ{sub gb} (the strengthening from (sub-) grain boundaries), M (Taylor factor) and τ{sub tot} (critical resolved shear stress). Results show that the higher τ{sub tot} in the alloy with V addition is the main contributor to the higher YS. According to the TEM observation and EDX analysis, the fine precipitates contributed to the higher τ{sub tot} in 4{sup #} alloy are quaternary AlFeVSi phases.

  4. Effect of minor addition of vanadium on mechanical properties and microstructures of as-extruded near eutectic Al–Si–Mg alloy

    Mechanical properties of near eutectic Al–12.5 wt%Si–0.6 wt%Mg alloys with and without addition of V were tested. Results show that addition of 0.1 wt% V only has a minor influence on the tensile properties of near eutectic Al–Si–Mg alloy in as-cast and as-homogenized conditions. However, it can significantly improve the tensile properties in as-extruded condition. The YS is enhanced nearly 50% and the elongation can reach 14%. Three factors that may contribute to the enhancement of YS were analyzed by EBSD, XRD and TEM investigation, i.e. Δσgb (the strengthening from (sub-) grain boundaries), M (Taylor factor) and τtot (critical resolved shear stress). Results show that the higher τtot in the alloy with V addition is the main contributor to the higher YS. According to the TEM observation and EDX analysis, the fine precipitates contributed to the higher τtot in 4# alloy are quaternary AlFeVSi phases

  5. Achieving high superplasticity of a traditional thermal–mechanical processed non-superplastic Al–Zn–Mg alloy sheet by low Sc additions

    Duan, Yulu [School of Materials Science and Engineering, Central South University, Changsha 410083 (China); Xu, GuoFu, E-mail: csuxgf66@csu.edu.cn [School of Materials Science and Engineering, Central South University, Changsha 410083 (China); Key Laboratory of Nonferrous Materials Science and Engineering of Ministry of Education, Central South University, Changsha 410083 (China); Zhou, Liqi; Xiao, Dan [School of Materials Science and Engineering, Central South University, Changsha 410083 (China); Deng, Ying, E-mail: csudengying@163.com [School of Materials Science and Engineering, Central South University, Changsha 410083 (China); School of Metallurgy and Environment, Central South University, Changsha 410083 (China); Yin, Zhimin [School of Materials Science and Engineering, Central South University, Changsha 410083 (China); Peng, Bing [School of Metallurgy and Environment, Central South University, Changsha 410083 (China); Pan, Qinglin [School of Materials Science and Engineering, Central South University, Changsha 410083 (China); Wang, Yingjun; Lu, Liying [Northeast Light Alloy Co. Ltd, Harbin 150060 (China)

    2015-07-25

    Highlights: • The superplastic of the Al–Zn–Mg–Sc–Zr alloy subjected to a traditional thermal–mechanical processing was investigated. • The boundary characteristics and thermal stability of the Al–Zn–Mg–Sc–Zr alloy were examined. • The deformation mechanism for Al–Zn–Mg–Sc–Zr alloy was analyzed. - Abstract: The non-superplastic Al–Zn–Mg alloy sheet produced by a simple traditional thermal–mechanical processing can achieve high superplasticity at the temperatures ranging from 450 to 500 °C and the strain rates ranging from 1 × 10{sup −3} to 1 × 10{sup −2} s{sup −1} by low scandium additions in the presence of 0.10% Sc (wt.%). An elongation of 1050% is obtained at 500 °C and 5 × 10{sup −3} s{sup −1}. Analyses on the superplastic data reveal that the average values of the strain rate sensitivity and the activation energy of the Al–Zn–Mg–Sc–Zr alloy are about 0.5 and 85 kJ/mol{sup −1}, respectively. The microstructural results show that the studied alloy consists of 3.14 μm grains characterized by a high fraction of low angle grain boundaries and strong β-fiber rolling textures. During superplastic deformation, low angle grain boundaries gradually transfer into high angle grain boundaries to sustain grain boundary sliding, and the texture intensity diminishes. Besides, β-fiber rolling textures weaken and cube and random textures are dominant in the superplastic deformed alloy. Superior superplastic ductility of the Al–Zn–Mg–Sc–Zr alloy is ascribed to the coherent 10–20 nm Al{sub 3}Sc{sub x}Zr{sub 1−x} particles that strongly retard recrystallization grain growth. Analyses of the superplastic data indicate that grain boundary sliding is the predominant deformation mechanism.

  6. [Drug-induced Cognitive Impairment].

    Shinohara, Moeko; Yamada, Masahito

    2016-04-01

    Elderly people are more likely than young people to develop cognitive impairments associated with medication use. One of the reasons for this is that renal and liver functions are often impaired in elderly people. Dementia and delirium (an acute confused state) are known to be associated with drug toxicity. Anticholinergic medications are common causes of both acute and chronic cognitive impairment. Psychoactive drugs, antidepressants and anticonvulsants can cause dementia and delirium. In addition, non-psychoactive drugs such as histamine H2 receptor antagonists, corticosteroids, NSAIDs (nonsteroidal anti-inflammatory agent), and cardiac medications, may cause acute or chronic cognitive impairment. Early diagnosis and withdrawal of the offending agent are essential for the prevention of drug-induced dementia and delirium. PMID:27056860

  7. UO2-7%Gd2O3 fuel process development by mechanical blending with reprocessing of waste products and usage of densification additive

    In the nuclear fuel cycle, reprocessing and storage of 'burned' fuels, either temporary or permanent, demand high investments and, in addition, can potentially generate environmental problems. A strategy to decrease these problems is to adopt measures to reduce the amount of waste generated. The usage of integrated burnable poison based on gadolinium is a measure that contributes to achieve this goal. The reason to use burnable poison is to control the neutron population in the reactor during the early life of the fresh reactor core or the beginning of each recharging fuel cycle, extending its cycle duration. Another advantage of using burnable poison is to be able to operate the reactor with higher burning rate, optimizing the usage of the fuel. The process of manufacturing UO2-Gd2O3 integrated burnable fuel poison generates waste that, as much as possible, needs to be recycled. Blending of Gd2O3 in UO2 powder requires the usage of a special additive to achieve the final fuel pellet specified density. The objective of this work is to develop the process of obtaining UO2 - 7% Gd2O3 integrated burnable poison using densification additives, aluminum hydroxide (Al(OH)3), and reprocessing manufacturing waste products by mechanical blending. The content of 7%- Gd2O3 is based on commercial PWR reactor fuels - Type Angra 2. The results show that the usage of Al(OH)3 as an additive is a very effective choice that promotes the densification of fuel pellets with recycle up to 10%. Concentrations of 0,20 % of Al(OH)3 were found to be the indicated amount on an industrial scale, specially when the recycled products come from U3O8 obtained by calcination of sintered pellets. This is particularly interesting because it is following the steps of sintering and rectifying of the pellets, which is generating the largest amounts of recycled material. (author)

  8. UO2-7%Gd2O3 fuel process development by mechanical blending with reprocessing of waste products and usage of densification additive

    In the nuclear fuel cycle, reprocessing and storage of 'burned' fuels, either temporary or permanent, demand high investments and, in addition, can potentially generate environmental problems. A strategy to decrease these problems is to adopt measures to reduce the amount of waste generated. The usage of integrated burnable poison based on gadolinium is a measure that contributes to achieve this goal. The reason to use burnable poison is to control the neutron population in the reactor during the early life of the fresh reactor core or the beginning of each recharging fuel cycle, extending its cycle duration. Another advantage of using burnable poison is to be able to operate the reactor with higher burning rate, optimizing the usage of the fuel. The process of manufacturing UO2-Gd2O3 integrated burnable fuel poison generates waste that, as much as possible, needs to be recycled. Blending of Gd2O3 in UO2 powder requires the usage of a special additive to achieve the final fuel pellet specified density. The objective of this work is to develop the process of obtaining UO2 - 7% Gd2O3 integrated burnable poison using densification additives, aluminum hydroxide (Al(OH)3), and reprocessing manufacturing waste products by mechanical blending. The content of 7%- Gd2O3 is based on commercial PWR reactor fuels - Type Angra 2. The results show that the usage of Al(OH)3 as an additive is a very effective choice that promotes the densification of fuel pellets with recycle up to 10%. Concentrations of 0,20 % of Al(OH)3 were found to be the indicated amount on an 7 industrial scale, specially when the recycled products come from U3O8 obtained by calcination of sintered pellets. This is particularly interesting because it is following the steps of sintering and rectifying of the pellets, which is generating the largest amounts of recycled material. (author)

  9. Effects of SnO2, WO3, and ZrO2 addition on the magnetic and mechanical properties of NiCuZn ferrites

    In this study, the effects of SnO2, WO3 and ZrO2 addition at levels up to 5 wt% on the magnetic and mechanical properties of Ni0.5Cu0.3Zn0.2Fe2O4 ceramics were investigated. Only Ni0.5Cu0.3Zn0.2Fe2O4 ceramic with a SnO2 addition of ≥3.5 wt% required a densification temperature of 1150 °C, while the others reached maximum densification at 1075 °C. All samples revealed a pure spinel phase and a uniform microstructure, except for the Ni0.5Cu0.3Zn0.2Fe2O4 ceramic with the WO3 addition, which showed an exaggerated grain growth accompanied with a small amount of needle-shaped Cu0.85Zn0.15WO4 second phase. The fracture mode in the pure Ni0.5Cu0.3Zn0.2Fe2O4 ceramic revealed a transgranular phase, as the CuO second phase increased the grain boundary strength; the Ni0.5Cu0.3Zn0.2Fe2O4 ceramics sintered with 5 wt% additives showed an intergranular phase. The Vickers hardness and the bending strength of the Ni0.5Cu0.3Zn0.2Fe2O4 ceramic were 733.6 and 62.0 MPa, respectively. The Vickers hardness of the ferrite with added SnO2 or ZrO2 showed only a slight improvement, while an apparent change (832.7) was observed with the addition of 5.0 wt% WO3. The bending strength of the ferrite was optimized at 75.7 MPa with 2.0 wt% SnO2 and at 90.5 MPa with 3.5 wt% ZrO2, while that of the ferrite sintered with WO3 added dropped gradually from 62.0 to 47.7 MPa as the amount of WO3 was increased from 0 to 5.0 wt% due to the non-uniform microstructure. The pure Ni0.5Cu0.3Zn0.2Fe2O4 ceramic sintered at 1075 °C had an initial permeability of 356.9 and a quality factor of 71.2. The addition of ZrO2 led to a significant increase in the initial permeability (588.4 at 5.0 wt% ZrO2), but a slight decline in the quality factor (56.6 at 5.0 wt% ZrO2). - Highlights: • Effects of additives on the physical properties of NiCuZn ceramics were studied. • NiCuZn with WO3 addition showed an abnormal grain growth and Cu0.85Zn0.15WO4 phase. • Ferrite with 5.0 wt% WO3 addition showed nearly 15

  10. Organocatalytic conjugate-addition polymerization of linear and cyclic acrylic monomers by N-heterocyclic carbenes: Mechanisms of chain initiation, propagation, and termination

    Zhang, Yuetao

    2013-11-27

    This contribution presents a full account of experimental and theoretical/computational investigations into the mechanisms of chain initiation, propagation, and termination of the recently discovered N-heterocyclic carbene (NHC)-mediated organocatalytic conjugate-addition polymerization of acrylic monomers. The current study specifically focuses on three commonly used NHCs of vastly different nucleophilicity, 1,3-di-tert-butylimidazolin-2-ylidene (ItBu), 1,3- dimesitylimidazolin-2-ylidene (IMes), and 1,3,4-triphenyl-4,5-dihydro-1H-1,2,4- triazol-5-ylidene (TPT), and two representative acrylic monomers, the linear methyl methacrylate (MMA) and its cyclic analog, biomass-derived renewable γ-methyl-α-methylene-γ-butyrolactone (MMBL). For MMA, there exhibits an exquisite selectivity of the NHC structure for the three types of reactions it promotes: enamine formation (single-monomer addition) by IMes, dimerization (tail-to-tail) by TPT, and polymerization by ItBu. For MMBL, all three NHCs promote no dimerization but polymerization, with the polymerization activity being highly sensitive to the NHC structure and the solvent polarity. Thus, ItBu is the most active catalyst of the series and converts quantitatively 1000-3000 equiv of MMBL in 1 min or 10 000 equiv in 5 min at room temperature to MMBL-based bioplastics with a narrow range of molecular weights of Mn = 70-85 kg/mol, regardless of the [MMBL]/[ItBu] ratio employed. The ItBu-catalyzed MMBL polymerization reaches an exceptionally high turnover frequency up to 122 s -1 and a high initiator efficiency value up to 1600%. Unique chain-termination mechanisms have been revealed, accounting for the production of relative high-molecular-weight linear polymers and the catalytic nature of this NHC-mediated conjugate-addition polymerization. Computational studies have provided mechanistic insights into reactivity and selectivity between two competing pathways for each NHC-monomer zwitterionic adduct, namely enamine

  11. Variation in mechanical behavior due to different build directions of Titanium6Aluminum4Vanadium fabricated by electron beam additive manufacturing technology

    Roy, Lalit

    Titanium has always been a metal of great interest since its discovery especially for critical applications because of its excellent mechanical properties such as light weight (almost half of that of the steel), low density (4.4 gm/cc) and high strength (almost similar to steel). It creates a stable and adherent oxide layer on its surface upon exposure to air or water which gives it a great resistance to corrosion and has made it a great choice for structures in severe corrosive environment and sea water. Its non-allergic property has made it suitable for biomedical application for manufacturing implants. Having a very high melting temperature, it has a very good potential for high temperature applications. But high production and processing cost has limited its application. Ti6Al4V is the most used titanium alloy for which it has acquired the title as `workhouse' of the Ti family. Additive layer Manufacturing (ALM) has brought revolution in manufacturing industries. Today, this additive manufacturing has developed into several methods and formed a family. This method fabricates a product by adding layer after layer as per the geometry given as input into the system. Though the conception was developed to fabricate prototypes and making tools initially, but its highly economic aspect i.e., very little waste material for less machining and comparatively lower production lead time, obviation of machine tools have drawn attention for its further development towards mass production. Electron Beam Melting (EBM) is the latest addition to ALM family developed by Arcam, ABRTM located in Sweden. The electron beam that is used as heat source melts metal powder to form layers. For this thesis work, three different types of specimens have been fabricated using EBM system. These specimens differ in regard of direction of layer addition. Mechanical properties such as ultimate tensile strength, elastic modulus and yield strength, have been measured and compared with standard data

  12. Anti-oxidant activity of 6-gingerol as a hydroxyl radical scavenger by hydrogen atom transfer, radical addition and electron transfer mechanisms

    MANISH K TIWARI; P C MISHRA

    2016-08-01

    Mechanisms of anti-oxidant action of 6-gingerol as a hydroxyl radical scavenger have been investigated using the transition state theory within the framework of density functional theory. Hydrogen abstraction by a hydroxyl radical from the different sites of 6-gingerol and addition of the former to the different sites ofthe latter were studied. Electron transfer from 6-gingerol to a hydroxyl radical was also studied. Solvent effect in aqueous media was treated using the integral equation formalism of the polarizable continuum model (IEFPCM). Reaction rate constants in aqueous media were generally found to be larger than those in gas phase. The tunneling contributions to rate constants were found to be appreciable. Our results show that 6-gingerol is an excellent anti-oxidant and would scavenge hydroxyl radicals efficiently.

  13. Effects of rare earth addition on microstructure and mechanical properties of a Fe–15Mn–1.5Al–0.6C TWIP steel

    The microstructure and mechanical properties of a Fe–15Mn–1.5Al–0.6C TWIP steel with and without rare earth (RE) addition were investigated. The RE-alloyed steel showed both improved tensile strength and total elongation (TEL). Optical microscopy and electron back-scattered diffraction (EBSD) characterizations showed that the RE-alloyed steel possessed a more homogeneous microstructure and a larger fraction of high-angle grain boundaries, which increased the TEL. Meanwhile, EBSD and transmission electron microscope (TEM) analyses indicated that the RE-alloyed steel exhibited more uniform distributed annealing twins and secondary annealing twins with a thickness of 10–20 nm appeared in some grains, which resulted in the higher tensile strength

  14. Enhanced high temperature cycling performance of LiMn2O4/graphite cells with methylene methanedisulfonate (MMDS) as electrolyte additive and its acting mechanism

    Fengju Bian; Zhongru Zhang; Yong Yang

    2014-01-01

    The effects of methylene methanedisulfonate (MMDS) on the high-temperature (∼50◦C) cycle performance of LiMn2O4/graphite cells are investigated. By addition of 2 wt%MMDS into a routine electrolyte, the high-temperature cycling performance of LiMn2O4/graphite cells can be significantly improved. The analysis of differential capacity curves and energy-dispersive X-ray spectrometry (EDX) indicates that MMDS decomposed on both cathode and anode. The three-electrode system of pouch cell is used to reveal the capacity loss mechanism in the cells. It is shown that the capacity fading of cells without MMDS in the electrolytes is due to irreversible lithium consumption during cycling and irreversible damage of LiMn2O4 material, while the capacity fading of cell with 2 wt%MMDS in electrolytes mainly originated from irreversible lithium consumption during cycling.

  15. Insights into mechanisms governing forest carbon response to nitrogen deposition: a model–data comparison using observed responses to nitrogen addition

    R. Q. Thomas

    2013-06-01

    Full Text Available In many forest ecosystems, nitrogen (N deposition enhances plant uptake of carbon dioxide, thus reducing climate warming from fossil fuel emissions. Therefore, accurately modeling how forest carbon (C sequestration responds to N deposition is critical for understanding how future changes in N availability will influence climate. Here, we use observations of forest C response to N inputs along N deposition gradients and at five temperate forest sites with fertilization experiments to test and improve a global biogeochemical model (CLM-CN 4.0. We show that the CLM-CN plant C growth response to N deposition was smaller than observed and the modeled response to N fertilization was larger than observed. A set of modifications to the CLM-CN improved the correspondence between model predictions and observational data (1 by increasing the aboveground C storage in response to historical N deposition (1850–2004 from 14 to 34 kg C per additional kg N added through deposition and (2 by decreasing the aboveground net primary productivity response to N fertilization experiments from 91 to 57 g C m−2 yr−1. Modeled growth response to N deposition was most sensitive to altering the processes that control plant N uptake and the pathways of N loss. The response to N deposition also increased with a more closed N cycle (reduced N fixation and N gas loss and decreased when prioritizing microbial over plant uptake of soil inorganic N. The net effect of all the modifications to the CLM-CN resulted in greater retention of N deposition and a greater role of synergy between N deposition and rising atmospheric CO2 as a mechanism governing increases in temperate forest primary production over the 20th century. Overall, testing models with both the response to gradual increases in N inputs over decades (N deposition and N pulse additions of N over multiple years (N fertilization allows for greater understanding of the mechanisms governing C–N coupling.

  16. Zymosan-mediated inflammation impairs in vivo reverse cholesterol transport.

    Malik, Priya; Berisha, Stela Z; Santore, Jennifer; Agatisa-Boyle, Colin; Brubaker, Gregory; Smith, Jonathan D

    2011-05-01

    Inflammation has been proposed to impair HDL function and reverse cholesterol transport (RCT). We investigated the effects of inflammation mediated by zymosan, a yeast glucan, on multiple steps along the RCT pathway in vivo and ex vivo. Acute inflammation with 70 mg/kg zymosan impaired RCT to plasma, liver, and feces similarly by 17-22% (P < 0.05), with no additional block at the liver. Hepatic gene expression further demonstrated no change in ABCG5, ABCB4, and ABCB11 expression but a decline in ABCG8 mRNA (32% P < 0.05). Plasma from zymosan-treated mice had a 21% decrease in cholesterol acceptor ability (P < 0.01) and a 35% decrease in ABCA1-specific efflux capacity (P < 0.01) in vitro. Zymosan treatment also decreased HDL levels and led to HDL remodeling with increased incorporation of serum amyloid A. In addition, cholesterol efflux from cultured macrophages declined with zymosan treatment in a dose dependent manner. Taken together, our results suggest that zymosan impairs in vivo RCT primarily by decreasing macrophage-derived cholesterol entering the plasma, with minimal additional blocks downstream. Our study supports the notion that RCT impairment is one of the mechanisms for the increased atherosclerotic burden observed in inflammatory conditions. PMID:21335620

  17. Effect of nano-ZrO2 addition on microstructure, mechanical property and thermal shock behaviour of dense chromic oxide refractory material

    To obtain a good performance hot-face lining material in gasifier, nano-ZrO2, up to 5 wt %, was added into chromic oxide powder with 3 wt % TiO2 followed by sintering at 1500°C for 2.5 h. The effect of nano-ZrO2 addition on microstructure, mechanical property and thermal shock behaviour was studied. ZrO2 promoted densification at contents higher than 1 wt %. Microcracks and phase transformation toughened the dense chromic oxide refractory material. The main reason for decrease of strength was the existence microcracks in specimens and weakening of intergranular fracture. Dense chromic oxide refractory material with 2∼3 wt % nano-ZrO2 possessed good densification, uniform microstructure, normal mechanical property and proper thermal shock resistance. The rupture strength retention ratio was nearly twice than that of chromic oxide material without ZrO2 after three cycles of quenching test from 950°C to cold water. (author)

  18. Effect of Ni and Pd Addition on Mechanical, Thermodynamic, and Electronic Properties of AuSn4-Based Intermetallics: A Density Functional Investigation

    Tian, Yali; Zhou, Wei; Wu, Ping

    2016-05-01

    The effects of Ni and Pd addition on the mechanical, thermodynamic, and electronic properties of AuSn4-based intermetallic compounds (IMCs) have been investigated by first-principles calculations to reveal the essence of Au embrittlement. Three kinds of doped (namely Ni-doped, Pd-doped, and Ni/Pd-codoped) IMCs are considered in this work. The polycrystalline elastic properties are deduced from single-crystal elastic constants. It is found that the doped systems together with nondoped AuSn4 are all ductile phases. For Ni-doped AuSn4, the modulus, hardness, brittleness, Debye temperature, and minimum thermal conductivity increase with the Ni fraction, but this is not the case for the Pd-doped material, since Au0.75Pd0.25Sn4 is the more brittle phase. For Au0.5Pd0.25Ni0.25Sn4, the mechanical, thermodynamic, and electronic properties are similar to those of Au0.5Pd0.5Sn4.

  19. Effects of rare earth elements and Ca additions on high temperature mechanical properties of AZ31 magnesium alloy processed by ECAP

    High temperature mechanical properties of equal channel angularly pressed (ECAPed) AZ31 magnesium alloy with 0.6%RE, 0.6%Ca and 0.3%RE-0.3%Ca additions were investigated. After extruding, the materials were ECAPed for 4 passes using route BC. Due to the textural effects induced by ECAP, the flow stress of the ECAPed AZ31 was lower than that of the extruded alloy at 523 K while tensile ductility was not changed. Thermal stability of the grain structure was achieved by RE-and Ca-containing particles, mainly due to the suppression of grain growth. Addition of the RE elements and calcium increased tensile strength mainly by dispersive strengthening effects of particles. The improved tensile ductility of the extruded material, however, was achieved by the presence of stable fine grains. Among all tested materials, AZ31-0.6%RE showed the maximum ductility of 198% at 523 K and a strain rate of 10-4 s-1.

  20. Food additives

    ... this page: //medlineplus.gov/ency/article/002435.htm Food additives To use the sharing features on this page, please enable JavaScript. Food additives are substances that become part of a food ...

  1. Length-scale dependent microalloying effects on precipitation behaviors and mechanical properties of Al–Cu alloys with minor Sc addition

    Jiang, L.; Li, J.K. [State Key Laboratory for Mechanical Behavior of Materials, Xi' an Jiaotong University, Xi' an 710049 (China); Liu, G., E-mail: lgsammer@mail.xjtu.edu.cn [State Key Laboratory for Mechanical Behavior of Materials, Xi' an Jiaotong University, Xi' an 710049 (China); Wang, R.H. [School of Materials Science and Engineering, Xi' an University of Technology, Xi' an 710048 (China); Chen, B.A.; Zhang, J.Y. [State Key Laboratory for Mechanical Behavior of Materials, Xi' an Jiaotong University, Xi' an 710049 (China); Sun, J., E-mail: junsun@mail.xjtu.edu.cn [State Key Laboratory for Mechanical Behavior of Materials, Xi' an Jiaotong University, Xi' an 710049 (China); Yang, M.X.; Yang, G. [Central Iron and Steel Research Institute, Beijing 100081 (China); Yang, J.; Cao, X.Z. [Key Laboratory of Nuclear Radiation and Nuclear Energy Technology, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049 (China)

    2015-06-18

    Heat-treatable Al alloys containing Al–2.5 wt% Cu (Al–Cu) and Al–2.5 wt% Cu–0.3 wt% Sc (Al–Cu–Sc) with different grain length scales, i.e., average grain size >10 μm ( defined coarse grained, CG), 1–2 μm (fine grained, FG), and <1 μm (ultrafine grained, UFG), were prepared by equal-channel angular pressing (ECAP). The length scale and Sc microalloying effects and their interplay on the precipitation behavior and mechanical properties of the Al–Cu alloys were systematically investigated. In the Al–Cu alloys, intergranular θ-Al{sub 2}Cu precipitation gradually dominated by sacrificing the intragranular θ′-Al{sub 2}Cu precipitation with reducing the length scale. Especially in the UFG regime, only intergranular θ-Al{sub 2}Cu particles were precipitated and intragranular θ′-Al{sub 2}Cu precipitation was completely disappeared. This led to a remarkable reduction in yield strength and ductility due to insufficient dislocation storage capacity. The minor Sc addition resulted in a microalloying effect in the Al–Cu alloy, which, however, is strongly dependent on the length scale. The smaller is the grain size, the more active is the microalloying effect that promotes the intragranular precipitation while reduces the intergranular precipitation. Correspondingly, compared with their Sc-free counterparts, the yield strength of post-aged CG, FG, and UFG Al–Cu alloys with Sc addition increased by ~36 MPa, ~56 MPa, and ~150 MPa, simultaneously in tensile elongation by ~20%, ~30%, and 280%, respectively. The grain size-induced evolutions in vacancy concentration/distribution and number density of vacancy-solute/solute–solute clusters and their influences on precipitation nucleation and kinetics have been comprehensively considered to rationalize the length scale-dependent Sc microalloying mechanisms using positron annihilation lifetime spectrum and three dimension atom probe. The increase in ductility was analyzed in the light of Sc microalloying

  2. Mechanical and Combustion Performance of Multi-Walled Carbon Nanotubes as an Additive to Paraffin-Based Solid Fuels for Hybrid Rockets

    Larson, Daniel B.; Boyer, Eric; Wachs, Trevor; Kuo, Kenneth, K.; Koo, Joseph H.; Story, George

    2012-01-01

    Paraffin-based solid fuels for hybrid rocket motor applications are recognized as a fastburning alternative to other fuel binders such as HTPB, but efforts to further improve the burning rate and mechanical properties of paraffin are still necessary. One approach that is considered in this study is to use multi-walled carbon nanotubes (MWNT) as an additive to paraffin wax. Carbon nanotubes provide increased electrical and thermal conductivity to the solid-fuel grains to which they are added, which can improve the mass burning rate. Furthermore, the addition of ultra-fine aluminum particles to the paraffin/MWNT fuel grains can enhance regression rate of the solid fuel and the density impulse of the hybrid rocket. The multi-walled carbon nanotubes also present the possibility of greatly improving the mechanical properties (e.g., tensile strength) of the paraffin-based solid-fuel grains. For casting these solid-fuel grains, various percentages of MWNT and aluminum particles will be added to the paraffin wax. Previous work has been published about the dispersion and mixing of carbon nanotubes.1 Another manufacturing method has been used for mixing the MWNT with a phenolic resin for ablative applications, and the manufacturing and mixing processes are well-documented in the literature.2 The cost of MWNT is a small fraction of single-walled nanotubes. This is a scale-up advantage as future applications and projects will require low cost additives to maintain cost effectiveness. Testing of the solid-fuel grains will be conducted in several steps. Dog bone samples will be cast and prepared for tensile testing. The fuel samples will also be analyzed using thermogravimetric analysis and a high-resolution scanning electron microscope (SEM). The SEM will allow for examination of the solid fuel grain for uniformity and consistency. The paraffin-based fuel grains will also be tested using two hybrid rocket test motors located at the Pennsylvania State University s High Pressure

  3. Vision impairment in Liverpool: prevalence and morbidity.

    Rogers, M.

    1996-01-01

    A database related to the activities of the Liverpool vision assessment team was used to identify all children with vision impairment aged 0-16 years, resident in Liverpool, UK, on 1 April 1995. Prevalence rates were calculated for all children with vision impairment, and separately for two groups: those with uncomplicated vision impairment, and those with additional pathology. Visual tract pathologies were tabulated and compared. Associated handicapping conditions were defined and the extent...

  4. Mechanics

    Chester, W

    1979-01-01

    When I began to write this book, I originally had in mind the needs of university students in their first year. May aim was to keep the mathematics simple. No advanced techniques are used and there are no complicated applications. The emphasis is on an understanding of the basic ideas and problems which require expertise but do not contribute to this understanding are not discussed. How­ ever, the presentation is more sophisticated than might be considered appropri­ ate for someone with no previous knowledge of the subject so that, although it is developed from the beginning, some previous acquaintance with the elements of the subject would be an advantage. In addition, some familiarity with element­ ary calculus is assumed but not with the elementary theory of differential equations, although knowledge of the latter would again be an advantage. It is my opinion that mechanics is best introduced through the motion of a particle, with rigid body problems left until the subject is more fully developed. Howev...

  5. The Effects of Al and Ti Additions on the Structural Stability, Mechanical and Electronic Properties of D8m-Structured Ta5Si3

    Linlin Liu

    2016-05-01

    Full Text Available In the present study, the influence of substitutional elements (Ti and Al on the structural stability, mechanical properties, electronic properties and Debye temperature of Ta5Si3 with a D8m structure were investigated by first principle calculations. The Ta5Si3 alloyed with Ti and Al shows negative values of formation enthalpies, indicating that these compounds are energetically stable. Based on the values of formation enthalpies, Ti exhibits a preferential occupying the Ta4b site and Al has a strong site preference for the Si8h site. From the values of the bulk modulus (B, shear modulus (G and Young’s modulus (E, we determined that both Ti and Al additions decrease both the shear deformation resistance and the elastic stiffness of D8m structured Ta5Si3. Using the shear modulus/bulk modulus ratio (G/B, Poisson’s ratio (υ and Cauchy’s pressure, the effect of Ti and Al additions on the ductility of D8m-structured Ta5Si3 are explored. The results show that Ti and Al additions reduce the hardness, resulting in solid solution softening, but improve the ductility of D8m-structured Ta5Si3. The electronic calculations reveal that Ti and Al additions change hybridization between Ta-Si and Si-Si atoms for the binary D8m-structured Ta5Si3. The new Ta-Al bond is weaker than the Ta-Si covalent bonds, reducing the covalent property of bonding in D8m-structured Ta5Si3, while the new strong Ti4b-Ti4b anti-bonding enhances the metallic behavior of the binary D8m-structured Ta5Si3. The change in the nature of bonding can well explain the improved ductility of D8m-structured Ta5Si3 doped by Ti and Al. Moreover, the Debye temperatures, ΘD, of D8m-structured Ta5Si3 alloying with Ti and Al are decreased as compared to the binary Ta5Si3.

  6. The GABAA antagonist bicuculline attenuates progesterone-induced memory impairments in middle-aged ovariectomized rats

    B. Blair Braden

    2015-08-01

    Full Text Available In women, high levels of natural progesterone have been associated with detrimental cognitive effects via the “maternal amnesia” phenomenon as well as in controlled experiments. In aged ovariectomized (Ovx rats, progesterone has been shown to impair cognition and impact the GABAergic system in cognitive brain regions. Here, we tested whether the GABAergic system is a mechanism of progesterone’s detrimental cognitive effects in the Ovx rat by attempting to reverse progesterone-induced impairments via concomitant treatment with GABAA antagonist, bicuculline. Thirteen month old rats received Ovx plus daily vehicle, progesterone, bicuculline, or progesterone+bicuculline injections beginning two weeks prior to testing. The water radial-arm maze was used to evaluate spatial working and reference memory. During learning, rats administered progesterone made more working memory errors than those administered vehicle, and this impairment was reversed by the addition of bicuculline. The progesterone impairment was transient and all animals performed similarly by the end of regular testing. On the last day of testing, a six-hour delay was administered to evaluate memory retention. Progesterone-treated rats were the only group to increase working memory errors with the delay; the addition of bicuculline prevented the progesterone-induced impairment. The vehicle, bicuculline, and progesterone+bicuculline groups were not impaired by the delay. The current rodent findings corroborate prior research reporting progesterone-induced detriments on cognition in women and in the aging Ovx rat. Moreover, the data suggest that progesterone-induced cognitive impairment is, in part, related to the GABAergic system. Given that progesterone is included in numerous clinically-prescribed hormone therapies and contraceptives (e.g. micronized, and as synthetic analogs, further research is warranted to better understand the parameters and mechanism(s of progesterone

  7. Effect of addition of organo clay on mechanical properties and dynamic-mechanical based TPV; Preparacao de termoplasticos vulcanizados dinamicamente (TPV) de NBR/PP com nanocargas de argila

    Honorato, Luciana R.; Silva, Adriana A.; Soares, Bluma G. [Universidade Federal do Rio de Janeiro - UFRJ, Instituto de Macromoleculas Professora Eloisa Mano, Rio de Janeiro, RJ (Brazil); Soares, Ketly P. [Centro Universitario do Leste de Minas Gerais (UNILESTEMG) - Coronel Fabriciano, MG (Brazil)

    2011-07-01

    The effect of organophilic clay on the mechanical and dynamical-mechanical properties of thermoplastic elastomers based on polypropylene (PP) and nitrile rubber (NBR) was investigated. The addition of clay was performed from a master batch prepared by a solution intercalation of NBR inside the clay galleries. Since the PP/NBR blend is highly incompatible, PP functionalized with maleic anhydride (PP-g-MA) and carboxylated NBR (XNBR) were employed as compatibilizing system together with triethylene-tetramine (TETA) used as coupling agent. The addition of Clay inside the elastomeric phase of the TPV resulted in a significant decrease of the elongation at break without changes on the tensile strength. The presence of clay also promoted a slight increase of the storage modulus and the glass transition temperature. The small angle X ray scattering confirmed the high dispersion of clay inside the TPV. Analysis of light scattering small angle (SAXS) confirmed the high dispersion of clay in the matrix of the TPV. (author)

  8. Epigenetic Treatments for Cognitive Impairments

    Day, Jeremy J.; Sweatt, J. David

    2011-01-01

    Epigenetic mechanisms integrate signals from diverse intracellular transduction cascades and in turn regulate genetic readout. Accumulating evidence has revealed that these mechanisms are critical components of ongoing physiology and function in the adult nervous system, and are essential for many cognitive processes, including learning and memory. Moreover, a number of psychiatric disorders and syndromes that involve cognitive impairments are associated with altered epigenetic function. In t...

  9. Insights into mechanisms governing forest carbon response to nitrogen deposition: a model-data comparison using observed responses to nitrogen addition

    R. Q. Thomas

    2013-01-01

    Full Text Available In many forest ecosystems, nitrogen (N deposition enhances plant uptake of carbon dioxide, thus reducing climate warming from fossil fuel emissions. Therefore, accurately modeling how forest carbon (C sequestration responds to N deposition is critical for understanding how future changes in N availability will influence climate. Here, we use observations of forest C response to N inputs along N deposition gradients and at five temperate forest sites with fertilization experiments to test and improve a~global biogeochemical model (CLM-CN 4.0. We show that the CLM-CN plant C growth response to N deposition was smaller than observed and the modeled response to N fertilization was larger than observed. A set of modifications to the CLM-CN improved the correspondence between model predictions and observational data (1 by increasing the aboveground C storage in response to historical N deposition (1850–2004 from 14 to 34 kg C per additional kg N added through deposition and (2 by decreasing the aboveground net primary productivity response to N fertilization experiments from 91 to 57 g C m−2 yr−1. Modeled growth response to N deposition was most sensitive to altering the processes that control plant N uptake and the pathways of N loss. The response to N deposition also increased with a more closed N cycle (reduced N fixation and N gas loss and decreased when prioritizing microbial over plant uptake of soil inorganic N. The net effect of all the modifications to the CLM-CN resulted in greater retention of N deposition and a greater role of synergy between N deposition and rising atmospheric CO2 as a mechanism governing increases in temperate forest primary production over the 20th century. Overall, testing models with both the response to gradual increases in N inputs over decades (N deposition and N pulse additions of N over multiple years (N fertilization allows for greater understanding of the mechanisms

  10. Effect of boron additions and processing on microstructure and mechanical properties of a titanium alloy Ti–6.5Al–3.3Mo–0.3Si

    The effects of boron additions in an amount of 0.1–2 wt%, thermomechanical processing and heat treatment on microstructure and mechanical properties of a two-phase titanium alloy Ti–6.5Al–3.3Mo–0.3Si alloy have been investigated. Depending on the boron amount, the materials under study were divided into two groups: (1) boron modified alloys containing ~0.1 wt% of boron and (2) discontinuously reinforced metal matrix Ti–TiB based composites containing 1.5–2 wt% of boron. Boron additions led to formation of TiB whiskers, which were predominantly located along boundaries of prior β-grains and α-colonies resulting in refined as-cast microstructure. Multiple 3D forging at T=650–700 °C applied for the boron modified alloys resulted in formation of ultrafine-grained microstructure and intensive breaking of TiB whiskers. Tensile properties of the Ti–6.5Al–3.3Mo–0.3Si–0.2 wt% B alloy after multiple 3D forging followed by β-heat treatment were found to be appreciably higher than those of the alloy free of boron after the same processing route that was ascribed to better controlling the β-grain size during β heat treatment. The composite materials were subjected to multiple isothermal 2D forging at T=950 °C that provided effective alignment of TiB whiskers while retaining their high aspect ratio. The hot forged composites demonstrated appreciably higher strength, creep resistance in comparison with those of the base alloy without drastic reduction in ductility. The effect of TiB whiskers orientation and morphology on the tensile properties of the composite materials is discussed

  11. Influence of fluoride additions on biological and mechanical properties of Na2O–CaO–SiO2–P2O5 glass–ceramics

    Two series of Na2O–CaO–SiO2–P2O5 glass–ceramics doped with NH4HF2 (G-NH4HF2) or CaF2 (G-CaF2) have been prepared by sol–gel method. The glass–ceramic phase composition and morphology were characterized by X-ray diffraction (XRD) and scanning electron microscopy coupled with energy dispersive spectroscopy (SEM-EDS). The mechanical properties and thermal expansion coefficient were measured by a microhardness tester, an electronic tensile machine and a thermal expansion coefficient tester. The structure difference between these two glass–ceramics was investigated by Fourier transform infrared spectroscopy (FTIR), and the in vitro bioactivity of the glass–ceramics was determined by in vitro simulated body fluid (SBF) immersion test. The hemolysis test, in vitro cytotoxicity test, systemic toxicity test and the implanted experiment in animals were used to evaluate the biocompatibility of the glass–ceramics. The mechanical properties of sample G-NH4HF2 are lower than that of sample G-CaF2, and the bioactivity of sample G-NH4HF2 is better than that of sample G-CaF2. The thermal expansion coefficients of these two glass–ceramics are all closer to that of Ti6Al4V. After 7 days of SBF immersion, apatites were induced on glass–ceramic surface, indicating that the glass–ceramics have bioactivity. The hemolysis test, in vitro cytotoxicity test and systemic toxicity test demonstrate that the glass–ceramics do not cause hemolysis reaction, and have no toxicity to cell and living animal. The implanted experiment in animals shows that bone tissue can form a good osseointegration with the implant after implantation for two months, indicating that the glass–ceramics are safe to serve as implants. - Highlights: • The variations of additions account for the differences in internal structure. • The intensity ratio of Si-O-NBO/Si-O (s,sym) of G-NH4HF2 is higher than that of G-CaF2. • The bioactivity of G-NH4HF2 is better than that of G-CaF2. • The

  12. Survivable Impairment-Aware Traffic Grooming

    Beshir, A.; Nuijts, R.; Malhotra, R.; Kuipers, F.

    2011-01-01

    Traffic grooming allows efficient utilization of network capacity by aggregating several independent traffic streams into a wavelength. In addition, survivability and impairment-awareness (i.e., taking into account the effect of physical impairments) are two important issues that have gained a lot o

  13. Effects of B and Cu Addition and Cooling Rate on Microstructure and Mechanical Properties in Low-Carbon, High-Strength Bainitic Steels

    Sung, Hyo Kyung; Shin, Sang Yong; Hwang, Byoungchul; Lee, Chang Gil; Lee, Sunghak

    2012-10-01

    The effects of B and Cu addition and cooling rate on microstructure and mechanical properties of low-carbon, high-strength bainitic steels were investigated in this study. The steel specimens were composed mostly of bainitic ferrite, together with small amounts of acicular ferrite, granular bainite, and martensite. The yield and tensile strengths of all the specimens were higher than 1000 MPa and 1150 MPa, respectively, whereas the upper shelf energy was higher than 160 J and energy transition temperature was lower than 208 K (-65 °C) in most specimens. The slow-cooled specimens tended to have the lower strengths, higher elongation, and lower energy transition temperature than the fast-cooled specimens. The Charpy notch toughness was improved with increasing volume fraction of acicular ferrite because acicular ferrites favorably worked for Charpy notch toughness even when other low-toughness microstructures such as bainitic ferrite and martensite were mixed together. To develop high-strength bainitic steels with an excellent combination of strength and toughness, the formation of bainitic microstructures mixed with acicular ferrite was needed, and the formation of granular bainite was prevented.

  14. Effect of burnable poison addition on the thermo-mechanical properties of UO2-5wt5CeO2 pellets

    The microstructural characteristics and the thermo-mechanical properties of the pellets were evaluated and compared for UO2 and UO2-5wt%CeO2 pellets doped with burnable poisons (5wt% and 10wt% of Gd2O3, Sm2O3 and Dy2O3), sintered in reducing atmosphere for 4h. The sintered density and the grain size of UO2 and UO2-5wt%CeO2 pellets decreased by adding Gd2O3, Sm2O3 and Dy2O3 and the Vickers handness (Hv) of these pellets were found not affected with density and grain size variations. The fracture toughness (KIC) of the UO2 pellets increased with Gd2O3 and Dy2O3 adding and decreased with 10wt% Sm2O3 but that of UO2-5wt%CeO2 pellets were not changed. The fracture strength (of) of UO2 and UO2-5wt%CeO2 pellets were not affected by addition of burnable poison material and the critical thermal shock temperature difference (ΔTc) of the pellets increased for UO2 pellets doped with Gd2O3. Sm2O3 and Dy2O3 in the low temperature range (80 ∼ 200 .deg. C)

  15. Effect of Nb2O5 Addition on The Microstructure and Mechanical Properties of The Al2O3-ZrO2 Ceramics

    Production of Al2O3-ZrO2 ceramics added with Nb2O5 at relatively low sintering temperature (1480oC) has been done. The aim of the research is to know the effect of Nb2O5 additive on the microstructure and mechanical properties of the Al2O3-ZrO2 ceramics. The research was conducted by sintering Al2O3-ZrO2 added with 0-1 % mole Nb2O5 at 1480oC in air for 1 hour and measuring the density of the sintered pellets, and analyzing the sintered pellets using optical microscope, electron microscope (SEM) and X-ray diffractometer, and determining the hardness and fracture toughness. The result of the density measurement showed that the density of the sintered pellets increased with increasing of Nb2O5 concentration.The metallographic analysis showed that the grain size of the Al2O3-ZrO2 sintered pellets increased with increasing of Nb2O5 concentration. Meanwhile, the X-ray diffraction analysis showed that the Al2O3-ZrO2 sintered pellets contained Nb2Zr6O17 second phase. The result of the hardness and fracture toughness test showed that the hardness and the fracture toughness increased with increasing of Nb2O5. (author)

  16. Effects of Al and Fe additions on microstructure and mechanical properties of SnAgCu eutectic lead-free solders

    Kantarcıoğlu, A.; Kalay, Y.E., E-mail: ekalay@metu.edu.tr

    2014-01-21

    In this study, Sn–3.5Ag–0.9Cu (wt%) lead-free solder was modified with minor additions of Al and Fe. The thermal, microstructural and mechanical behaviors after and before compositional modifications were investigated by a combined study of differential scanning calorimetry (DSC), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and shear strength measurements. EDS results and Darken–Gurry predictions indicated a high concentration of Fe substitution within the Cu{sub 6}Sn{sub 5} at the solder/copper interface which induced desirable effects on undercooling and microstructure evolution. Eutectic SAC and SAC+0.05 wt% Al solder joints exhibit considerable number of brittle proeutectic phases (i.e., Ag{sub 3}Sn). Proeutectic Ag{sub 3}Sn formation was found to be suppressed after Fe modification. A new type of Al–Sn–Cu intermetallic compound was detected for Al added specimens. The rod-like morphology of this IMC appears to cause a sharp decrease in the shear strength of Al modified solder joints. The shear strength values for Fe modified solder joints were found to be higher in a wider composition range (0.01–0.1 wt% Fe) as compared to eutectic SAC and SAC+0.05 wt% Al.

  17. Effects of Al and Fe additions on microstructure and mechanical properties of SnAgCu eutectic lead-free solders

    In this study, Sn–3.5Ag–0.9Cu (wt%) lead-free solder was modified with minor additions of Al and Fe. The thermal, microstructural and mechanical behaviors after and before compositional modifications were investigated by a combined study of differential scanning calorimetry (DSC), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and shear strength measurements. EDS results and Darken–Gurry predictions indicated a high concentration of Fe substitution within the Cu6Sn5 at the solder/copper interface which induced desirable effects on undercooling and microstructure evolution. Eutectic SAC and SAC+0.05 wt% Al solder joints exhibit considerable number of brittle proeutectic phases (i.e., Ag3Sn). Proeutectic Ag3Sn formation was found to be suppressed after Fe modification. A new type of Al–Sn–Cu intermetallic compound was detected for Al added specimens. The rod-like morphology of this IMC appears to cause a sharp decrease in the shear strength of Al modified solder joints. The shear strength values for Fe modified solder joints were found to be higher in a wider composition range (0.01–0.1 wt% Fe) as compared to eutectic SAC and SAC+0.05 wt% Al

  18. The Influence of As-Built Surface Conditions on Mechanical Properties of Ti-6Al-4V Additively Manufactured by Selective Electron Beam Melting

    Sun, Y. Y.; Gulizia, S.; Oh, C. H.; Fraser, D.; Leary, M.; Yang, Y. F.; Qian, M.

    2016-03-01

    Achieving a high surface finish is a major challenge for most current metal additive manufacturing processes. We report the first quantitative study of the influence of as-built surface conditions on the tensile properties of Ti-6Al-4V produced by selective electron beam melting (SEBM) in order to better understand the SEBM process. Tensile ductility was doubled along with noticeable improvements in tensile strengths after surface modification of the SEBM-fabricated Ti-6Al-4V by chemical etching. The fracture surfaces of tensile specimens with different surface conditions were characterised and correlated with the tensile properties obtained. The removal of a 650- μm-thick surface layer by chemical etching was shown to be necessary to eliminate the detrimental influence of surface defects on mechanical properties. The experimental results and analyses underline the necessity to modify the surfaces of SEBM-fabricated components for structural applications, particularly for those components which contain complex internal concave and convex surfaces and channels.

  19. Driver Compensation: Impairment or Improvement?

    Young, Richard A

    2015-12-01

    Strayer et al.'s conclusion that their "cognitive distraction scale" for auditory-vocal tasks indicates "significant impairments to driving" is not supported by their data. Additional analysis demonstrates that slower brake reaction times during auditory-vocal tasks were fully compensated for by longer following distances to the lead car. Naturalistic driving data demonstrate that cellular conversation decreases crash risk, the opposite of the article's assumption. Hence, the scale's internal and external validities for indicating driving impairment are highly questionable. PMID:26534851

  20. All Vision Impairment

    ... Cases of Vision Impairment (in thousands) by Age, Gender, and Race/Ethnicity Table for 2010 U.S. Prevalent ... Cases of Vision Impairment (in thousands) by Age, Gender, and Race/Ethnicity Table for 2000 U.S. Prevalent ...

  1. Speech impairment (adult)

    ... impairment; Impairment of speech; Inability to speak; Aphasia; Dysarthria; Slurred speech; Dysphonia voice disorders ... in others the condition does not get better. DYSARTHRIA With dysarthria, the person has ongoing difficulty expressing ...

  2. Mild Cognitive Impairment

    ... Research Portfolio (IADRP) AMP-AD Detecting Cognitive Impairment Database ... Mild cognitive impairment (MCI) is a condition in which people have more memory or other thinking problems than normal for their ...

  3. Additivity dominance

    Paul Rozin

    2009-10-01

    Full Text Available Judgments of naturalness of foods tend to be more influenced by the process history of a food, rather than its actual constituents. Two types of processing of a ``natural'' food are to add something or to remove something. We report in this study, based on a large random sample of individuals from six countries (France, Germany, Italy, Switzerland, UK and USA that additives are considered defining features of what makes a food not natural, whereas ``subtractives'' are almost never mentioned. In support of this, skim milk (with major subtraction of fat is rated as more natural than whole milk with a small amount of natural vitamin D added. It is also noted that ``additives'' is a common word, with a synonym reported by a native speaker in 17 of 18 languages, whereas ``subtractive'' is lexicalized in only 1 of the 18 languages. We consider reasons for additivity dominance, relating it to omission bias, feature positive bias, and notions of purity.

  4. Influence of additive system (Al2O3-RE2O3 , RE = Y, La, Nd, Dy, Yb) on microstructure and mechanical properties of silicon nitride-based ceramics

    Juliana Marchi; Cecilia Chaves Guedes e Silva; Bruno Batista Silva; José Carlos Bressiani; Ana Helena de Almeida Bressiani

    2009-01-01

    Silicon nitride based ceramics have been widely used as structural ceramics, due mainly to their thermo-mechanical properties such as high density, high thermal shock resistance, corrosion resistance and chemical stability. The aim of this study was to determine the influence of rare earth and aluminum oxide additions as sintering aids on densification, microstructure and mechanical properties of silicon nitride. Silicon nitride mixtures with 91 wt. (%) Si3N4 and 9% wt. (%) additives were pre...

  5. A window of vulnerability: impaired fear extinction in adolescence.

    Baker, Kathryn D; Den, Miriam L; Graham, Bronwyn M; Richardson, Rick

    2014-09-01

    There have been significant advances made towards understanding the processes mediating extinction of learned fear. However, despite being of clear theoretical and clinical significance, very few studies have examined fear extinction in adolescence, which is often described as a developmental window of vulnerability to psychological disorders. This paper reviews the relatively small body of research examining fear extinction in adolescence. A prominent finding of this work is that adolescents, both humans and rodents, exhibit a marked impairment in extinction relative to both younger (e.g., juvenile) and older (e.g., adult) groups. We then review some potential mechanisms that could produce the striking extinction deficit observed in adolescence. For example, one neurobiological candidate mechanism for impaired extinction in adolescence involves changes in the functional connectivity within the fear extinction circuit, particularly between prefrontal cortical regions and the amygdala. In addition, we review research on emotion regulation and attention processes that suggests that developmental changes in attention bias to threatening cues may be a cognitive mechanism that mediates age-related differences in extinction learning. We also examine how a differential reaction to chronic stress in adolescence impacts upon extinction retention during adolescence as well as in later life. Finally, we consider the findings of several studies illustrating promising approaches that overcome the typically-observed extinction impairments in adolescent rodents and that could be translated to human adolescents. PMID:24513634

  6. 轻度认知障碍患者简单加法计算的事件相关电位早成分%Early components of event-related potentials of single-unit number addition to mild cognitive impairment patients

    张媛媛; 李秀艳; 李密; 孟庆慧

    2011-01-01

    Objective To study mental calculation efficiency and early components changes of event-related potentials (ERP) on single-unit number addition to mild cognitive impairment (MCI) patients.Methods 16 healthy old men and 16 MCI patients were selected as subjects in experiment Behavior data and mean amplitude and potential of early components of ERP ( N1, P1, N170, P2) were compared.Results The reaction time of MCI group ( 1 691.03 ±94.59) ms was significantly longer than that of control group [( 1 539.55 ± 27.76) ms, P <0.01]The correct rate of MCI group (94.63 ±4.19)% was significantly lower than that of control group [(97.76 ± 2.15)%, P <0.01].The temporal-occipital N170 and central-frontal P2 of MCI group appeared later than that of control group, and the amplitude were larger.Compared with N170 in control group, N170 was significantly lower at left temporal-occipital region and higher at right temporal-occipital region in MCI group.Conclusions Patients with MCI have the deficit in single-unit number addition.The early arithmetic calculation processing mechanism of MCI patients may be different from normal people.%目的 研究轻度认知障碍(MCI)患者简单加法计算的心算效率及事件相关电位(ERP)早成分改变.方法 被试者分为正常老年(对照)组和MCI组,每组16名,均为右利手.使用ERP技术,采集简单计算过程的脑电信号,比较两组行为数据和算式早成分(N1,P1,N170,P2)的波幅和潜伏期的差异.结果 MCI组的反应时长于对照组,差异具有显著性(P<0.01);MCI组的正确率低于对照组,差异具有显著性(P<0.01);MCI组与对照组比较,颞枕区N170以及额中央区P2潜伏期延长(P<0.01),波幅增大(P<0.05);MCI组左侧颞枕区N170波幅低于对照组,差异具有显著性(P<0.01);MCI组右侧颞枕区N170波幅高于对照组,差异具有显著性(P<0.01).结论 MCI患者简单加法计算的心算效率降低,计算的正确率降低,同时提示大脑在算

  7. Additivity dominance

    Paul Rozin; Claude Fischler; Christy Shields-Argeles

    2009-01-01

    Judgments of naturalness of foods tend to be more influenced by the process history of a food, rather than its actual constituents. Two types of processing of a ``natural'' food are to add something or to remove something. We report in this study, based on a large random sample of individuals from six countries (France, Germany, Italy, Switzerland, UK and USA) that additives are considered defining features of what makes a food not natural, whereas ``subtractives'' are almost never mentioned....

  8. Effect of texture evolution on mechanical properties of near eutectic Al–Si–Mg alloy with minor addition of Zr/V during hot extrusion

    Highlights: • Minor addition of V has great effect on texture evolution of as-extruded Al-Si-Mg alloy. • As-extruded Al-Si-Mg alloy with V addition has excellent properties of UTS, YS and elongation. • Impact of Zr addition is not as considerable as that of V addition. - Abstract: Texture evolution of as-extruded near eutectic Al–Si–Mg alloy with minor addition of Zr or V was studied by electron backscatter diffraction (EBSD), and the tensile properties were tested. To some extent, addition of 0.1% Zr could impede the recrystallization operation of near eutectic Al–Si–Mg alloy during hot extrusion. Addition of 0.1% V exhibits very strong inhibitory effect on recrystallization, that the texture of 4# alloy is mainly composed of deformation texture component of Brass {1 1 0}〈112〉, which may contribute to the excellent combined properties of ultimate strength (UTS), yield strength (YS) and elongation. The impact of Zr addition on the tensile properties is not as considerable as that of V addition

  9. Visual impairment in the hearing impaired students

    Gogate Parikshit

    2009-01-01

    Full Text Available Background : Ocular problems are more common in children with hearing problems than in normal children. Neglected visual impairment could aggravate educational and social disability. Aim : To detect and treat visual impairment, if any, in hearing-impaired children. Setting and Design : Observational, clinical case series of hearing-impaired children in schools providing special education. Materials and Methods : Hearing-impaired children in selected schools underwent detailed visual acuity testing, refraction, external ocular examination and fundoscopy. Ocular motility testing was also performed. Teachers were sensitized and trained to help in the assessment of visual acuity using Snellen′s E charts. Refractive errors and squint were treated as per standard practice. Statistical Analysis : Excel software was used for data entry and SSPS for analysis. Results : The study involved 901 hearing-impaired students between four and 21 years of age, from 14 special education schools. A quarter of them (216/901, 24% had ocular problems. Refractive errors were the most common morbidity 167(18.5%, but only 10 children were using appropriate spectacle correction at presentation. Fifty children had visual acuity less than 20/80 at presentation; after providing refractive correction, this number reduced to three children, all of whom were provided low-vision aids. Other common conditions included strabismus in 12 (1.3% children, and retinal pigmentary dystrophy in five (0.6% children. Conclusion : Ocular problems are common in hearing-impaired children. Screening for ocular problems should be made mandatory in hearing-impaired children, as they use their visual sense to compensate for the poor auditory sense.

  10. Impaired sleep and allostatic load

    Clark, Alice Jessie; Dich, Nadya; Lange, Theis;

    2014-01-01

    Objective: Understanding the mechanisms linking sleep impairment to morbidity and mortality is important for future prevention, but these mechanisms are far from elucidated. We aimed to determine the relation between impaired sleep, both in terms of duration and disturbed sleep, and allostatic load...... Biobank with comprehensive information on sleep duration, disturbed sleep, objective measures of an extensive range of biological risk markers, and physical conditions. Results: Long sleep (mean difference 0.23; 95% confidence interval, 0.13, 0.32) and disturbed sleep (0.14; 0.06, 0.22) were associated...... with higher AL as well as with high-risk levels of risk markers from the anthropometric, metabolic, and immune system. Sub-analyses suggested that the association between disturbed sleep and AL might be explained by underlying disorders. Whereas there was no association between short sleep and AL, the...

  11. The influence of different cross-linking reactions and glycerol addition on thermal and mechanical properties of biodegradable gliadin-based film

    Soares, Rosane M.D.; Soldi, Valdir, E-mail: vsoldi@qmc.ufsc.br

    2010-06-15

    In this study gliadin solutions previously cross-linked by 1-(3-dimethylaminopropyl)-3-1-ethylcarbodiimide hydrochloride/N-hydroxysuccinimide (EDC/NHS) and L-cysteine were prepared with different plasticizer concentrations. The obtained films were investigated through mechanical behavior (Young's modulus and elongation at break), thermal characteristics (differential scanning calorimetry and thermogravimetric analysis), swelling and water solubility, FTIR measurements and scanning electron microscopy. The relationships between the gliadin structure and the mechanical, thermal and morphological properties were affected by protein conformational changes during the cross-linking reaction. On the other hand, the reaction mechanism was strongly dependent on the glycerol content.

  12. Mechanics

    Hartog, J P Den

    1961-01-01

    First published over 40 years ago, this work has achieved the status of a classic among introductory texts on mechanics. Den Hartog is known for his lively, discursive and often witty presentations of all the fundamental material of both statics and dynamics (and considerable more advanced material) in new, original ways that provide students with insights into mechanical relationships that other books do not always succeed in conveying. On the other hand, the work is so replete with engineering applications and actual design problems that it is as valuable as a reference to the practicing e

  13. Anti-MuSK-Positive Myasthenia Gravis in a Patient with Parkinsonism and Cognitive Impairment

    S. Lanfranconi

    2011-01-01

    Full Text Available Muscle-specific tyrosine kinase- (MuSK- antibodies-positive Myasthenia Gravis accounts for about one third of Seronegative Myasthenia Gravis and is clinically characterized by early onset of prominent bulbar, neck, shoulder girdle, and respiratory weakness. The response to medical therapy is generally poor. Here we report a case of late-onset MuSK-antibodies-positive Myasthenia Gravis presenting with signs of cognitive impairment and parkinsonism in addition to bulbar involvement and external ophthalmoplegia. The pattern of involvement of both peripheral and central nervous system dysfunction might suggest a common pathogenic mechanism, involving impaired cholinergic transmission.

  14. Impaired Leydig cell function in infertile men

    Andersson, A-M; Jørgensen, N; Frydelund-Larsen, L; Rajpert-De Meyts, E; Skakkebaek, N E

    2004-01-01

    To investigate whether an impaired Leydig cell function is present in severely oligospermic men, serum testosterone (T), LH, estradiol (E(2)), and SHBG levels in 357 idiopathic infertile men were compared with levels in 318 proven fertile men. In addition, the T/LH ratio, E(2)/T ratio, and...... fertile levels.Thus, the group of infertile men showed significant signs of impaired Leydig cell function in parallel to their impaired spermatogenesis. The association of decreased spermatogenesis and impaired Leydig cell function might reflect a disturbed paracrine communication between the seminiferous...... epithelium and the Leydig cells, triggered by distorted function of the seminiferous epithelium. On the other hand, the parallel impairment of spermatogenesis and Leydig cells may reflect a congenital dysfunction of both compartments caused by a testicular dysgenesis during fetal/infant development....

  15. Mechanisms Involved in the Improvement of Lipotoxicity and Impaired Lipid Metabolism by Dietary α-Linolenic Acid Rich Salvia hispanica L (Salba) Seed in the Heart of Dyslipemic Insulin-Resistant Rats

    Creus, Agustina; Ferreira, María R.; Oliva, María E.; Lombardo, Yolanda B.

    2016-01-01

    This study explores the mechanisms underlying the altered lipid metabolism in the heart of dyslipemic insulin-resistant (IR) rats fed a sucrose-rich diet (SRD) and investigates if chia seeds (rich in α-linolenic acid 18:3, n-3 ALA) improve/reverse cardiac lipotoxicity. Wistar rats received an SRD-diet for three months. Half of the animals continued with the SRD up to month 6. The other half was fed an SRD in which the fat source, corn oil (CO), was replaced by chia seeds from month 3 to 6 (SRD+chia). A reference group consumed a control diet (CD) all the time. Triglyceride, long-chain acyl CoA (LC ACoA) and diacylglycerol (DAG) contents, pyruvate dehydrogenase complex (PDHc) and muscle-type carnitine palmitoyltransferase 1 (M-CPT1) activities and protein mass levels of M-CPT1, membrane fatty acid transporter (FAT/CD36), peroxisome proliferator activated receptor α (PPARα) and uncoupling protein 2 (UCP2) were analyzed. Results show that: (a) the hearts of SRD-fed rats display lipotoxicity suggesting impaired myocardial lipid utilization; (b) Compared with the SRD group, dietary chia normalizes blood pressure; reverses/improves heart lipotoxicity, glucose oxidation, the increased protein mass level of FAT/CD36, and the impaired insulin stimulated FAT/CD36 translocation to the plasma membrane. The enhanced M-CPT1 activity is markedly reduced without similar changes in protein mass. PPARα slightly decreases, while the UCP2 protein level remains unchanged in all groups. Normalization of dyslipidemia and IR by chia reduces plasma fatty acids (FAs) availability, suggesting that a different milieu prevents the robust translocation of FAT/CD36. This could reduce the influx of FAs, decreasing the elevated M-CPT1 activity and lipid storage and improving glucose oxidation in cardiac muscles of SRD-fed rats. PMID:26828527

  16. Mechanisms Involved in the Improvement of Lipotoxicity and Impaired Lipid Metabolism by Dietary α-Linolenic Acid Rich Salvia hispanica L (Salba Seed in the Heart of Dyslipemic Insulin-Resistant Rats

    Agustina Creus

    2016-01-01

    Full Text Available This study explores the mechanisms underlying the altered lipid metabolism in the heart of dyslipemic insulin-resistant (IR rats fed a sucrose-rich diet (SRD and investigates if chia seeds (rich in α-linolenic acid 18:3, n-3 ALA improve/reverse cardiac lipotoxicity. Wistar rats received an SRD-diet for three months. Half of the animals continued with the SRD up to month 6. The other half was fed an SRD in which the fat source, corn oil (CO, was replaced by chia seeds from month 3 to 6 (SRD+chia. A reference group consumed a control diet (CD all the time. Triglyceride, long-chain acyl CoA (LC ACoA and diacylglycerol (DAG contents, pyruvate dehydrogenase complex (PDHc and muscle-type carnitine palmitoyltransferase 1 (M-CPT1 activities and protein mass levels of M-CPT1, membrane fatty acid transporter (FAT/CD36, peroxisome proliferator activated receptor α (PPARα and uncoupling protein 2 (UCP2 were analyzed. Results show that: (a the hearts of SRD-fed rats display lipotoxicity suggesting impaired myocardial lipid utilization; (b Compared with the SRD group, dietary chia normalizes blood pressure; reverses/improves heart lipotoxicity, glucose oxidation, the increased protein mass level of FAT/CD36, and the impaired insulin stimulated FAT/CD36 translocation to the plasma membrane. The enhanced M-CPT1 activity is markedly reduced without similar changes in protein mass. PPARα slightly decreases, while the UCP2 protein level remains unchanged in all groups. Normalization of dyslipidemia and IR by chia reduces plasma fatty acids (FAs availability, suggesting that a different milieu prevents the robust translocation of FAT/CD36. This could reduce the influx of FAs, decreasing the elevated M-CPT1 activity and lipid storage and improving glucose oxidation in cardiac muscles of SRD-fed rats.

  17. Mechanisms Involved in the Improvement of Lipotoxicity and Impaired Lipid Metabolism by Dietary α-Linolenic Acid Rich Salvia hispanica L (Salba) Seed in the Heart of Dyslipemic Insulin-Resistant Rats.

    Creus, Agustina; Ferreira, María R; Oliva, María E; Lombardo, Yolanda B

    2016-01-01

    This study explores the mechanisms underlying the altered lipid metabolism in the heart of dyslipemic insulin-resistant (IR) rats fed a sucrose-rich diet (SRD) and investigates if chia seeds (rich in α-linolenic acid 18:3, n-3 ALA) improve/reverse cardiac lipotoxicity. Wistar rats received an SRD-diet for three months. Half of the animals continued with the SRD up to month 6. The other half was fed an SRD in which the fat source, corn oil (CO), was replaced by chia seeds from month 3 to 6 (SRD+chia). A reference group consumed a control diet (CD) all the time. Triglyceride, long-chain acyl CoA (LC ACoA) and diacylglycerol (DAG) contents, pyruvate dehydrogenase complex (PDHc) and muscle-type carnitine palmitoyltransferase 1 (M-CPT1) activities and protein mass levels of M-CPT1, membrane fatty acid transporter (FAT/CD36), peroxisome proliferator activated receptor α (PPARα) and uncoupling protein 2 (UCP2) were analyzed. Results show that: (a) the hearts of SRD-fed rats display lipotoxicity suggesting impaired myocardial lipid utilization; (b) Compared with the SRD group, dietary chia normalizes blood pressure; reverses/improves heart lipotoxicity, glucose oxidation, the increased protein mass level of FAT/CD36, and the impaired insulin stimulated FAT/CD36 translocation to the plasma membrane. The enhanced M-CPT1 activity is markedly reduced without similar changes in protein mass. PPARα slightly decreases, while the UCP2 protein level remains unchanged in all groups. Normalization of dyslipidemia and IR by chia reduces plasma fatty acids (FAs) availability, suggesting that a different milieu prevents the robust translocation of FAT/CD36. This could reduce the influx of FAs, decreasing the elevated M-CPT1 activity and lipid storage and improving glucose oxidation in cardiac muscles of SRD-fed rats. PMID:26828527

  18. Endocrine Risk Factors for Cognitive Impairment.

    Moon, Jae Hoon

    2016-06-01

    Cognitive impairment, including Alzheimer's disease and other kinds of dementia, is a major health problem in older adults worldwide. Although numerous investigators have attempted to develop effective treatment modalities or drugs, there is no reasonably efficacious strategy for preventing or recovering from cognitive impairment. Therefore, modifiable risk factors for cognitive impairment have received attention, and the growing literature of metabolic risk factors for cognitive impairment has expanded from epidemiology to molecular pathogenesis and therapeutic management. This review focuses on the epidemiological evidence for the association between cognitive impairment and several endocrine risk factors, including insulin resistance, dyslipidemia, thyroid dysfunction, vitamin D deficiency, and subclinical atherosclerosis. Researches suggesting possible mechanisms for this association are reviewed. The research investigating modifiable endocrine risk factors for cognitive impairment provides clues for understanding the pathogenesis of cognitive impairment and developing novel treatment modalities. However, so far, interventional studies investigating the beneficial effect of the "modification" of these "modifiable risk factors" on cognitive impairment have reported variable results. Therefore, well-designed, randomized prospective interventional studies are needed. PMID:27118278

  19. Hypertension and cognitive impairment

    Su-hang SHANG

    2015-08-01

    Full Text Available As a leading risk factor for stroke, hypertension is also an important risk factor for cognitive impairment. Midlife hypertension doubles the risk of dementia later in life and accelerates the progression of dementia, but the correlation between late-life blood pressure and cognitive impairment is still unclear. Beside blood pressure, the effect of pulse pressure, blood pressure variability and circadian rhythm of blood pressure on cognition is currently attracting more and more attention. Hypertension induces alterations in cerebrovascular structure and functions, which lead to brain lesions including cerebral atrophy, stroke, lacunar infarcts, diffuse white matter damage, microinfarct and microhemorrhage, resuling in cognitive impairment. Hypertension also impairs the metabolism and transfer of amyloid-β protein (Aβ, thus accelerates cognitive impairment. Individualized therapy, focusing on characteristics of hypertensive patients, may be a good choice for prevention and treatment of cognitive impairment. DOI: 10.3969/j.issn.1672-6731.2015.08.004

  20. Obesity and Hypertriglyceridemia Produce Cognitive Impairment

    Farr, Susan A.; Yamada, Kelvin A.; Butterfield, D. Allan; Abdul, H. Mohammad; Xu, Lin; Miller, Nicole E.; Banks, William A.; Morley, John E.

    2008-01-01

    Obesity is associated with cognitive impairments. Long-term mechanisms for this association include consequences of hyperglycemia, dyslipidemia, or other factors comprising metabolic syndrome X. We found that hypertriglyceridemia, the main dyslipidemia of metabolic syndrome X, is in part responsible for the leptin resistance seen in obesity. Here we determined whether triglycerides have an immediate and direct effect on cognition. Obese mice showed impaired acquisition in three different cogn...

  1. 9Cr-1Mo martensitic alloys: effects of the nitrogen, niobium and vanadium additions on the microstructure, phase transformations and mechanical properties. Pt. 1 and 2

    9Cr - 1Mo martensitic steels are leading candidate materials for fast reactor sub-assembly wrapper applications. The microstructure, phase transformations and mechanical properties of five 9Cr1Mo alloys containing N, Nb and/or V have been studied by dilatometry, optical and electron transmission microscopy and microanalysis

  2. Mechanical Properties Evaluation of Zr Addition in L12-Al3(Sc1- x Zr x ) Using First-Principles Calculation

    Qian, Yi; Xue, Jilai; Wang, Zengjie; Yang, Zhenhai; Qian, Ping

    2016-05-01

    L12-Al3(Sc1- x Zr x ) can be used as a grain refiner and recrystallization inhibitor in forming and heat-treatment of wrought aluminum alloy. In this work, the mechanical properties of L12-Al3(Sc1- x Zr x ) (0 process optimization for Al alloys in forming and heat treatment.

  3. Triazolines--XXVII. delta2-1,2,3-triazoline anticonvulsants: novel 'built-in' heterocyclic prodrugs with a unique 'dual-action' mechanism for impairing excitatory amino acid L-glutamate neurotransmission.

    Kadaba, P K; Stevenson, P J; P-Nnane, I; Damani, L A

    1996-02-01

    The delta2-1,2,3-triazoline anticonvulsants (1) may be considered as representing a unique class of 'built-in' heterocyclic prodrugs where the active 'structure element' is an integral part of the ring system and can be identified only by a knowledge of their chemical reactivity and metabolism. Investigations on the metabolism and pharmacology of a lead triazoline, ADD17014 (1a), suggest that the triazolines function as 'prodrugs' and exert their anticonvulsant activity by impairing excitatory amino acid (EAA) L-glutamate (L-Glu) neurotransmission via a unique 'dual-action' mechanism. While an active beta-amino alcohol metabolite, 2a, from the parent prodrug acts as an N-methyl-D-aspartate (NMDA)/MK-801 receptor antagonist, the parent triazoline impairs the presynaptic release of L-Glu. Various pieces of theoretical reasoning and experimental evidence led to the elucidation of the dual-action mechanism. Based on the unique chemistry of the triazolines, the potential metabolic pathways and biotransformation products of 1a were predicted to be the beta-amino alcohols 2a and 2a', the alpha-amino acid 3a, the triazole 4a, the aziridine 5a, and the ketimine 6a. In vivo and in vitro pharmacological studies of 1a and potential metabolities, along with a full quantitative urinary metabolic profiling of 1a, indicated the beta-amino alcohol 2a as the active species. It was the only compound that inhibited the specific binding of [3H]MK-801 to the MK-801 site, 56% at 10 microM drug concentration, but itself had no anticonvulsant activity, suggesting 1a acted as a prodrug. Three metabolites were identified; 2a was the most predominant, with lesser amounts of 2a', and very minor amounts of aziridine 5a. Since only 5a can yield 2a', its formation indicated that the biotransformation of 1a occurred, at least in part, through 5a. No amino acid metabolite 3a was detected, which implied that no in vivo oxidation of 2a or oxidative biotransformation of 1a or 5a by hydroxylation at

  4. Influencing the arc and the mechanical properties of the weld metal in GMA-welding processes by additive elements on the wire electrode surface

    Wesling, V.; Schram, A.; Müller, T.; Treutler, K.

    2016-03-01

    Under the premise of an increasing scarcity of raw materials and increasing demands on construction materials, the mechanical properties of steels and its joints are gaining highly important. In particular high- and highest-strength steels are getting in the focus of the research and the manufacturing industry. To the same extent, the requirements for filler metals are increasing as well. At present, these low-alloy materials are protected by a copper coating (film coatings on solid wire electrodes for Gas Metal Arc welding. The influences are regarding the stability of the arc, the properties of the weld metal in terms of geometric expression, chemical composition and mechanical properties, the composition of the arc-plasma and the dynamics of the molten metal.

  5. Effect of Minor Zn Additions on the Mechanical and Corrosion Properties of Solution-Treated AM60-2%RE Magnesium Alloy

    Liu, Z. L.; Liu, Y.; Liu, X. Q.; Wang, M. M.

    2016-07-01

    The microstructure, mechanical properties, and corrosion behaviors of solution-treated AM60-2%RE magnesium alloy containing 0.2-0.8% wt.% Zn were investigated. With the increase of Zn, the volume fraction of dispersed rod-like Al4RE and granular-like Al11RE3 phases of solution-treated AM60-2%RE + x%Zn increased, which improved the mechanical properties by dispersion strengthening. With increasing Zn content, the corrosion current density decreased, and the corrosion potential and electrochemical impedance of the alloys increased, and the corrosion resistance of solution-treated AM60-2%RE + x%Zn was improved. With the increase of Zn content, the leaf-like corrosion products of the alloy became smaller and more compact, and the content of Zn, Al, Ce, and La in corrosion products increased, which was beneficial to inhibit the corrosion progress.

  6. Including Additional Land Use, Land Use Change and Forestry-activities under the Clean Development Mechanism : Discussions in the United Nations Climate Negotiations

    Lindgren, Lina

    2011-01-01

      Land use, land use change and forestry activities (LULUCF) can help mitigate climate change by creating a terrestrial carbon sink, removing carbon dioxide from the atmosphere, while at the same time help increasing adaptive capacity and reduce poverty. Still, carbon stored in biomass or soils are only stored temporary since natural or human induced disturbances can cause a total or partial loss of stored carbon. LULUCF-activities under the clean development mechanism (CDM),  one of the flex...

  7. The use of bone cement for the localized, controlled release of the antibiotics vancomycin, linezolid, or fusidic acid: effect of additives on drug release rates and mechanical strength.

    Jackson, John; Leung, Fay; Duncan, Clive; Mugabe, Clement; Burt, Helen

    2011-04-01

    Bone cement containing antibiotics is commonly used to treat orthopedic related infections. However, effective treatment (especially of resistant bacteria, methacillin-resistant Staphylococcus aureus (MRSA)) is compromised by very low levels of drug release so that typically less than 10% of loaded drug is released over a 6-week period. The objective of this study was to investigate the effect of incorporation of water soluble excipients (polyethylene glycol, sodium chloride, or dextran) into antibiotic-loaded cement on mechanical strength and drug release properties. Poly(methyl methylacrylate) cement implants containing various amounts of drug (vancomycin, linezolid or fusidic acid (all MRSA active)) and excipients were cast in the form of beads or films and characterized using differential scanning calorimetry. Mechanical strength as assessed by Young's modulus was determined by thermo-mechanical analysis. Drug release was measured by incubation in phosphate buffered saline with analysis by HPLC methods. The inclusion of sodium chloride up to 20% w/w caused only minor reductions in Young's modulus. Vancomycin and linezolid released very slowly from unmodified bone cement beads (less than 3% released by 4 weeks) whereas fusidic acid released more quickly (approximately 8% released by 4 weeks). The inclusion of sodium chloride or dextran in bone cement resulted in major increases in the release rate of vancomycin, linezolid and fusidic acid. These studies support the inclusion of sodium chloride and dextran in bone cement to increase the release rate of vancomycin, linezolid, or fusidic acid without compromising the mechanical strength of the composite material. PMID:25788111

  8. Effect of HfC addition on mechanical properties of Nb-5Mo-2W-18Si in-situ composites

    Nb base in-situ composites with the base composition of Nb-5Mo-2W-18Si were prepared by conventional arc-melting and induction heating floating zone melting followed by directional solidification. To investigate the effect of HfC addition, Nb was replaced with 0, 1 and 2 mol% HfC. The in-situ composites predominantly have an eutectic microstructure consisting of Nb solid solution (NbSS) and (Nb,Mo,W)5Si3 (5-3 silicide). The strength at 1470 K and 1670 K increases without fracture toughness decreasing, with increasing the HfC content. Directional solidification also improves the strength at the high temperature. The slip band under the shearing stress occurs in the NbSS during plastic deformation, which contributes to suppress microcrack propagation. It seems that HfC addition reinforces the bonding strength at grain boundary or NbSS/5-3 silicide interface. (orig.)

  9. Lubrication performance and mechanisms of Mg/Al-, Zn/Al-, and Zn/Mg/Al-layered double hydroxide nanoparticles as lubricant additives

    Li, Shuo; Bhushan, Bharat

    2016-08-01

    Solid lubricant particles are commonly used as oil additives for low friction and wear. Mg/Al-, Zn/Al-, and Zn/Mg/Al-layered double hydroxides (LDH) were synthesized by coprecipitation method. The benefits of LDH nanoparticles are that they can be synthesized using chemical methods where size and shape can be controlled, and can be modified organically to allow dispersal in fluids. The LDH nanoparticles were characterized by X-ray diffraction, scanning electron microscope, thermogravimetry, and differential scanning calorimetry. A pin-on-disk friction and wear tester was used for evaluating the friction and wear properties of LDH nanoparticles as lubricant additives. LDH nanoparticles have friction-reducing and anti-wear properties compared to oil without LDHs. Mg/Al-LDH has the best lubrication, possibly due to better thermal stability in severe conditions.

  10. Mechanisms of radical formation in beef and chicken meat during high pressure processing evaluated by electron spin resonance detection and the addition of antioxidants.

    Bolumar, Tomas; Andersen, Mogens L; Orlien, Vibeke

    2014-05-01

    The generation of radicals during high pressure (HP) processing of beef loin and chicken breast was studied by spin trapping and electron spin resonance detection. The pressurization resulted in a higher level of spin adducts in the beef loin than in the chicken breast. It was shown that radicals were formed in the sarcoplasmic and myofibrillar fractions as well as in the non-soluble protein fraction due to the HP treatment, indicating that other radicals than iron-derived radicals were formed, and most likely protein-derived radicals. The addition of iron as well as the natural antioxidants caffeic acid, rosemary extract, and ascorbic acid resulted in an increased formation of radicals during the HP treatment, whereas addition of ethylendiamintetraacetic acid (EDTA) reduced the radical formation. This suggests that iron-species (protein-bound or free) catalyses the formation of radicals when meat systems are submitted to HP. PMID:24360471

  11. The effect of nickel addition on antimicrobial, physical, and mechanical properties of copper-nickel alloy against suspensions of Escherichia coli

    Nurhayani, Dinni; Korda, Akhmad A.

    2015-09-01

    Escherichia coli (E. coli) infection can cause serious illness. Humans can be infected by E. coli via contact with the contaminated food and water. Copper and copper alloys were known for their antimicrobial properties and were applied in several healthcare setting as antimicrobial material. However, the people preference in the appearance of stainless steel and aluminum contribute to the low application of copper and its alloy. In this study, the mechanical, physical, and antibacterial properties of copper and copper-nickel alloy compared with stainless steel 304 were tested. The antibacterial activity of stainless steel, copper, and copper-nickel alloy was evaluated by inoculating 7.5 × 106 - 2.5 × 107 CFU/ml suspensions of E. coli. The bacterial colonies were investigated after 0-4 hour incubation at 37°C. The result showed that on the observation time, copper and copper-nickel (Cu-Ni) alloys have antibacterial activity while the bacteria in stainless steel remain existed. The appearance (color / shade) of Cu-Ni alloys in some composition is silvery which is stainless steel-like. For the mechanical properties, copper-nickel alloys have lower hardness than stainless steel (SS 304). This research proved that copper-nickel alloys have the ability to reduce the amount of E. col colonies. The copper content may affect the antibacterial activity but not directly linked. Cu-Ni alloys also have the appearance and mechanical properties that quite similar compared to SS304. Therefore, Cu-Ni alloys have the potential to be applied as substitution or complementary material of SS304 in various applications for preventing the bacterial contamination especially E. coli.

  12. Effect of Zr and Si addition on high temperature mechanical properties of near-α Ti–Al–Zr–Sn based alloys

    Jayaprakash, M., E-mail: MURUGESAN.Jayaprakash@nims.go.jp; Ping, D.H.; Yamabe-Mitarai, Y.

    2014-08-26

    The mechanical properties and microstructural evolution of Ti–Al–Zr–Sn based near α-Ti alloys with various amounts of Zr and Si have been systematically investigated. The compression test results reveal that higher contents of Zr and Si can improve the yielding strength both at room temperature and high temperature (650 °C). The enhanced yield strength was found to be contributed mainly by fine silicide precipitates (Ti{sub 5}Si{sub 3}). Zr was enriched in the silicide formed at α-lath boundaries. The microstructural characterization of the alloys with various alloying elements has been studied using transmission electron microscopy (TEM)

  13. Scale dynamical origin of modification or addition of potential in mechanics. A possible framework for the MOND theory and the dark matter

    Pierret, Frédéric

    2016-01-01

    Using our mathematical framework developed in \\cite{cresson-pierret_scale} called \\emph{scale dynamics}, we propose in this paper a new way of interpreting the problem of adding or modifying potentials in mechanics and specifically in galactic dynamics. An application is done for the two-body problem with a Keplerian potential showing that the velocity of the orbiting body is constant. This would explain the observed phenomenon in the flat rotation curves of galaxies without adding \\emph{dark matter} or modifying Newton's law of dynamics.

  14. Effect of Zr and Si addition on high temperature mechanical properties of near-α Ti–Al–Zr–Sn based alloys

    The mechanical properties and microstructural evolution of Ti–Al–Zr–Sn based near α-Ti alloys with various amounts of Zr and Si have been systematically investigated. The compression test results reveal that higher contents of Zr and Si can improve the yielding strength both at room temperature and high temperature (650 °C). The enhanced yield strength was found to be contributed mainly by fine silicide precipitates (Ti5Si3). Zr was enriched in the silicide formed at α-lath boundaries. The microstructural characterization of the alloys with various alloying elements has been studied using transmission electron microscopy (TEM)

  15. Persistent increase in oxygen consumption and impaired neurovascular coupling after spreading depression in rat neocortex

    Hansen, Henning Piilgaard; Lauritzen, Martin

    2009-01-01

    Cortical spreading depression (CSD) is associated with a dramatic failure of brain ion homeostasis and increased energy metabolism. There is strong clinical and experimental evidence to suggest that CSD is the mechanism of migraine, and involved in progressive neuronal injury in stroke and head...... trauma. Here we tested the hypothesis that single episodes of CSD induced acute hypoxia, and prolonged impairment of neurovascular and neurometabolic coupling. Cortical spreading depression was induced in rat frontal cortex, whereas cortical electrical activity and local field potentials (LFPs) were...... following 2 h, basal tpO(2) and CBF were reduced whereas basal CMRO(2) was persistently elevated by 8.1%+/-2.9%. In addition, within first hour after CSD we found impaired neurovascular coupling (LFP versus CBF), whereas neurometabolic coupling (LFP versus CMRO(2)) remained unaffected. Impaired...

  16. Effect of Addition of Boric Acid and Borax on Fire-Retardant and Mechanical Properties of Urea Formaldehyde Saw Dust Composites

    Zenat A. Nagieb

    2011-01-01

    Full Text Available Properties of the flame retardant urea formaldehyde (UF board made from saw dust fibers were investigated. Flame retardant chemicals that were evaluated include boric acid (BA and borax (BX which were incorporated with saw dust fibers to manufacture experimental panels. Three concentration levels, (0.5, 1, and 5% of fire retardants and 10% urea formaldehyde resin based on oven dry fiber weight were used to manufacture experimental panels. Physical and mechanical properties including water absorption, modulus of rupture (MOR, and modulus of elasticity (MOE were determined. The results showed that water absorption and bending strength decreased as the flame retardant increased. The highest concentration of (BA + BX enhanced the fire retardant more than the lower ones. Scanning electron microscope and FTIR of composite panels were studied.

  17. Neuroscience education in addition to trigger point dry needling for the management of patients with mechanical chronic low back pain: A preliminary clinical trial.

    Téllez-García, Mario; de-la-Llave-Rincón, Ana I; Salom-Moreno, Jaime; Palacios-Ceña, Maria; Ortega-Santiago, Ricardo; Fernández-de-Las-Peñas, César

    2015-07-01

    The objective of the current study was to determine the short-term effects of trigger point dry needling (TrP-DN) alone or combined with neuroscience education on pain, disability, kinesiophobia and widespread pressure sensitivity in patients with mechanical low back pain (LBP). Twelve patients with LBP were randomly assigned to receive either TrP-DN (TrP-DN) or TrP-DN plus neuroscience education (TrP-DN + EDU). Pain intensity (Numerical Pain Rating Scale, 0-10), disability (Roland-Morris Disability Questionnaire-RMQ-, Oswestry Low Back Pain Disability Index-ODI), kinesiophobia (Tampa Scale of Kinesiophobia-TSK), and pressure pain thresholds (PPT) over the C5-C6 zygapophyseal joint, transverse process of L3 vertebra, second metacarpal, and tibialis anterior muscle were collected at baseline and 1-week after the intervention. Patients treated with TrP-DN + EDU experienced a significantly greater reduction of kinesiophobia (P = 0.008) and greater increases in PPT over the transverse process of L3 (P = 0.049) than those patients treated only with TrP-DN. Both groups experienced similar decreases in pain, ODI and RMQ, and similar increases in PPT over the C5/C6 joint, second metacarpal, and tibialis anterior after the intervention (all, P > 0.05). The results suggest that TrP-DN was effective for improving pain, disability, kinesiophobia and widespread pressure sensitivity in patients with mechanical LBP at short-term. The inclusion of a neuroscience educational program resulted in a greater improvement in kinesiophobia. PMID:26118519

  18. Classification of zygomatic fractures based on operation art type and an experimental study on the mechanical stability of additional Kirschner wire fixation

    Contemporary treatment of the zygoma includes an open reduction and internal fixation of at least three articulations, frontozygomatic suture, infraorbital rim, and zygomaticomaxillary buttress. But the authors believe many of the fractures could adequately be stabilized with only an intraoral approach and a single plate at the zygomaticomaxillary buttress. CT scans now identify the exact fracture pattern in a specific area. Some zygoma fractures demonstrate little or no displacement. They are incomplete through at least one articulation, with stability provided by the incomplete fracture. Frequently, the incomplete (greenstick) fracture is at the frontozygomatic suture and/or the zygomatic arch. Minor degrees of displacement do not justify a standard operation. In isolated fractures of the zygomatic arch, miniplate fixation at one site of the zygoma alone cannot provide adequate stability for the zygoma to be maintained at the correct position. In these cases, we use Kirschner wire fixation as an additional zygoma fixation technique. The purpose of this article is to classify fracture patterns for treatment of zygoma and to verify the effectiveness of Kirschner wire fixation. The study groups were assembled by reviewing medical records of patients who had undergone zygomatic repair at Teikyo University Hospital, Tokyo between the January of 2003 and December of 2007. Ninety-one malar fractures were divided into eight different types according to their malar tripod dislocation, especially frontozygomatic suture, maxillozygomatic suture and temporozygomatic suture (zygomatic arch). We then matched these types of malar fracture to a corresponding treatment strategy. Noncomminuted zygomatic fracture models were simulated by osteotomy. Each model was fixed with miniplates, microplates and Kirschner wires in the 6 different ways. A static force was loaded onto each model from three dictions. 58 patients (64%) were classified type 2. In the experimental study, additional

  19. Effect of Cr, Ti, V, and Zr Micro-additions on Microstructure and Mechanical Properties of the Al-Si-Cu-Mg Cast Alloy

    Shaha, S. K.; Czerwinski, F.; Kasprzak, W.; Friedman, J.; Chen, D. L.

    2016-05-01

    Uniaxial static and cyclic tests were used to assess the role of Cr, Ti, V, and Zr additions on properties of the Al-7Si-1Cu-0.5Mg (wt pct) alloy in as-cast and T6 heat-treated conditions. The microstructure of the as-cast alloy consisted of α-Al, eutectic Si, and Cu-, Mg-, and Fe-rich phases Al2.1Cu, Al8.5Si2.4Cu, Al5.2CuMg4Si5.1, and Al14Si7.1FeMg3.3. In addition, the micro-sized Cr/Zr/Ti/V-rich phases Al10.7SiTi3.6, Al6.7Si1.2TiZr1.8, Al21.4Si3.4Ti4.7VZr1.8, Al18.5Si7.3Cr2.6V, Al7.9Si8.5Cr6.8V4.1Ti, Al6.3Si23.2FeCr9.2V1.6Ti1.3, Al92.2Si16.7Fe7.6Cr8.3V1.8, and Al8.2Si30.1Fe1.6Cr18.8V3.3Ti2.9Zr were present. During solution treatment, Cu-rich phases were completely dissolved, while the eutectic silicon, Fe-, and Cr/Zr/Ti/V-rich intermetallics experienced only partial dissolution. Micro-additions of Cr, Zr, Ti, and V positively affected the alloy strength. The modified alloy in the T6 temper during uniaxial tensile tests exhibited yield strength of 289 MPa and ultimate tensile strength of 342 MPa, being significantly higher than that for the Al-Si-Cu-Mg base. Besides, the cyclic yield stress of the modified alloy in the T6 state increased by 23 pct over that of the base alloy. The fatigue life of the modified alloy was substantially longer than that of the base alloy tested using the same parameters. The role of Cr, Ti, V, and Zr containing phases in controlling the alloy fracture during static and cyclic loading is discussed.

  20. Study of the Adherence Mechanism Between the Metal and Inorganic Coating with Mill Addition of Li2Ni8O10 Nano Powder

    QIAN Hui-chun; JIANG Wei-zhong

    2009-01-01

    The adherence strength between the metal and the inorganic coating can be greatly increased by mill addition of Li2Ni8O10,. The interface structure between metal and the inorganic coating with excellent adherence has been studied by investigating the chemical composition and the microstructure as well as elements valence bond on the interface with the help of scanning electron microscope (SEM), electron microprobe, and Auger electron spectroscope (AES). The results show that there is a non-stoichiometrical transitional layer on the interface between metal and the inorganic coating with excellent adherence, the adherence between metal and the non-stoichiometrical transitional layer is achieved by the metallic bond and the adherence between the non-stoichiometrical transitional layer and the inorganic coating is produced by ionic and covalent bond. The non-stoichiometrical transitional layer results in the strong adherence.

  1. Influence of Al{sub 2}O{sub 3} addition on microstructure and mechanical properties of 3YSZ-Al{sub 2}O{sub 3} composites

    Abden, Md. Jaynul [International Islamic Univ., Chittagong (Bangladesh). Dept. of Electrical and Electronic Engineering; Afroze, Jannatul Dil [Noakhali Science and Technology Univ. (Bangladesh). Faculty of Science and Engineering; Gafur, Md. Abdul [Bangladesh Council of Scientific and Industrial Research, Dhaka (Bangladesh). Pilot Plant and Process Development Centre; Chowdhury, Faruque-Uz-Zaman [Chittagong University of Engineering and Technology (Bangladesh). Dept. of Physics

    2015-07-01

    The effect of the amount of Al{sub 2}O{sub 3} content on microstructure, tetragonal phase stability and mechanical properties of 3YSZ-Al{sub 2}O{sub 3} composites are investigated in this study. The ceramic composites are obtained by means of uniaxial compacting at 210 MPa and green compacts are sintered at 1550 C for 3 h in air. The monoclinic zirconia (m-ZrO{sub 2}) phase has completely been transformed into tetragonal zirconia (t-ZrO{sub 2}) phase with corresponding higher Al{sub 2}O{sub 3} content. The t-ZrO{sub 2} grains induce transgranular fracture mode that has contribution in improvement of fracture toughness. The maximum flexural strength of 340 MPa, Vickers hardness value of 14.31 GPa and fracture toughness of 5.1 MPa x m{sup 1/2} in the composition containing 40 wt.-% Al{sub 2}O{sub 3} is attributed to the microstructure with t-ZrO{sub 2} grains as inter- and intragranular particles in the Al{sub 2}O{sub 3} grains, which makes it suitable for dental applications.

  2. Additively Manufactured Open-Cell Porous Biomaterials Made from Six Different Space-Filling Unit Cells: The Mechanical and Morphological Properties

    Seyed Mohammad Ahmadi

    2015-04-01

    Full Text Available It is known that the mechanical properties of bone-mimicking porous biomaterials are a function of the morphological properties of the porous structure, including the configuration and size of the repeating unit cell from which they are made. However, the literature on this topic is limited, primarily because of the challenge in fabricating porous biomaterials with arbitrarily complex morphological designs. In the present work, we studied the relationship between relative density (RD of porous Ti6Al4V EFI alloy and five compressive properties of the material, namely elastic gradient or modulus (Es20–70, first maximum stress, plateau stress, yield stress, and energy absorption. Porous structures with different RD and six different unit cell configurations (cubic (C, diamond (D, truncated cube (TC, truncated cuboctahedron (TCO, rhombic dodecahedron (RD, and rhombicuboctahedron (RCO were fabricated using selective laser melting. Each of the compressive properties increased with increase in RD, the relationship being of a power law type. Clear trends were seen in the influence of unit cell configuration and porosity on each of the compressive properties. For example, in terms of Es20–70, the structures may be divided into two groups: those that are stiff (comprising those made using C, TC, TCO, and RCO unit cell and those that are compliant (comprising those made using D and RD unit cell.

  3. Effects of extrusion speed on the microstructure and mechanical properties of ZK60 alloys with and without 1 wt% cerium addition

    The effects of extrusion speed on the microstructure and tensile properties of the ZK60 and ZK60-1Ce alloys were investigated by performing indirect extrusion at three ram speeds (0.3, 1.0 and 3.0 mm/s). All of the extruded alloys showed a bimodal microstructure consisting of equiaxed fine recrystallized (DRXed) grains and elongated coarse unDRXed grains. With increasing extrusion speed, the exit temperature increased due to deformation heating, resulting in a larger grain and a higher DRXed fraction. The yield and ultimate tensile strengths and elongation at RT decreased with an increase of extrusion speed. The ZK60-1Ce alloys exhibited a finer grain size, a higher DRXed fraction, and weaker texture intensity than the ZK60 alloys at the same extrusion speed due to the inhibition of grain growth by the pinning effect and the promotion of DRX by particle-stimulated nucleation. The yield and ultimate tensile strengths at room and elevated temperatures were increased by the addition of Ce, while elongation was decreased due to cracking at the Mg–Zn–Ce particles

  4. Impaired Fracture Healing after Hemorrhagic Shock

    Philipp Lichte

    2015-01-01

    Full Text Available Impaired fracture healing can occur in severely injured patients with hemorrhagic shock due to decreased soft tissue perfusion after trauma. We investigated the effects of fracture healing in a standardized pressure controlled hemorrhagic shock model in mice, to test the hypothesis that bleeding is relevant in the bone healing response. Male C57/BL6 mice were subjected to a closed femoral shaft fracture stabilized by intramedullary nailing. One group was additionally subjected to pressure controlled hemorrhagic shock (HS, mean arterial pressure (MAP of 35 mmHg for 90 minutes. Serum cytokines (IL-6, KC, MCP-1, and TNF-α were analyzed 6 hours after shock. Fracture healing was assessed 21 days after fracture. Hemorrhagic shock is associated with a significant increase in serum inflammatory cytokines in the early phase. Histologic analysis demonstrated a significantly decreased number of osteoclasts, a decrease in bone quality, and more cartilage islands after hemorrhagic shock. μCT analysis showed a trend towards decreased bone tissue mineral density in the HS group. Mechanical testing revealed no difference in tensile failure. Our results suggest a delay in fracture healing after hemorrhagic shock. This may be due to significantly diminished osteoclast recruitment. The exact mechanisms should be studied further, particularly during earlier stages of fracture healing.

  5. Extinction memory is impaired in schizophrenia

    Holt, Daphne. J.; Lebron-Milad, Kelimer; Milad, Mohammed R.; Rauch, Scott L.; Pitman, Roger K.; Orr, Scott P.; Cassidy, Brittany S.; Walsh, Jared P.; Goff, Donald C.

    2013-01-01

    Background Schizophrenia is associated with abnormalities in emotional processing and social cognition, which may result from disruption of the underlying neural mechanism(s) governing emotional learning and memory. To investigate this possibility, we measured the acquisition and extinction of conditioned fear responses and delayed recall of extinction in schizophrenia and control subjects. Methods 28 schizophrenia and 18 demographically-matched control subjects underwent a two-day fear conditioning, extinction learning and extinction recall procedure, in which skin conductance response (SCR) magnitude was used as the index of conditioned responses. Results During fear acquisition, 83% of the controls and 57% of the patients showed autonomic responsivity (‘responders’), and the patients showed larger SCRs to the stimulus that was not paired with the unconditioned stimulus (CS−) than the controls. Within the responder group, there was no difference between the patients and controls in levels of extinction learning; however, the schizophrenia patients showed significant impairment, relative to the controls, in context-dependent recall of the extinction memory. In addition, delusion severity in the patients correlated with baseline skin conductance levels. Conclusions These data are consistent with prior evidence for a heightened neural response to innocuous stimuli in schizophrenia and elevated arousal levels in psychosis. The finding of deficient extinction recall in schizophrenia patients who showed intact extinction learning suggests that schizophrenia is associated with a disturbance in the neural processes supporting emotional memory. PMID:18986648

  6. Impairments to Vision

    ... an external Non-Government web site. Impairments to Vision Normal Vision Diabetic Retinopathy Age-related Macular Degeneration In this ... pictures, fixate on the nose to simulate the vision loss. In diabetic retinopathy, the blood vessels in ...

  7. Aids for visual impairment.

    Dudley, N. J.

    1990-01-01

    This article provides only a flavour of the type and range of aids available to the visually impaired person. Many other aids for leisure, learning, and daily living are illustrated in the RNIB equipment and games catalogue.

  8. Kids' Quest: Vision Impairment

    ... and neighborhood . Step 8: Now see if your attitudes have changed. Take the Fact Checkup again. ... impairment also have at least one other developmental disability, such as intellectual disabilities, cerebral palsy, hearing loss, ...

  9. Speech impairment (adult)

    ... ALS or Lou Gehrig disease), cerebral palsy, myasthenia gravis, or multiple sclerosis (MS) Facial trauma Facial weakness, ... provider will likely ask about the speech impairment. Questions may include when the problem developed, whether there ...

  10. What determines goodwill impairment?

    Verriest, Arnt; Gaeremynck, Ann

    2009-01-01

    This study investigates determinants of goodwill impairment decisions and their disclosure quality. Under IAS36 goodwill is subject to an annual impairment test in which the carrying amount of goodwill is not allowed to exceed the recoverable amount. However, valuing this recoverable amount is subject to substantial managerial discretion. Therefore, we predict that ownership concentration, corporate governance quality and firm performance provide incentives for managers to engage in goodwill ...

  11. Formation of Carbon Nanotube Based Gears: Quantum Chemistry and Molecular Mechanics Study of the Electrophilic Addition of o-Benzyne to Fullerenes, Graphene, and Nanotubes

    Jaffe, Richard; Han, Jie; Globus, Al; Chancellor, Marisa K. (Technical Monitor)

    1997-01-01

    Considerable progress has been made in recent years in chemical functionalization of fullerene molecules. In some cases, the predominant reaction products are different from those obtained (using the same reactants) from polycyclic aromatic hydrocarbons (PAHs). One such example is the cycloaddition of o-benzyne to C60. It is well established that benzyne adds across one of the rings in naphthalene, anthracene and other PAHs forming the [2+4] cycloaddition product (benzobicyclo[2.2.2.]-octatriene with naphthalene and triptycene with anthracene). However, Hoke et al demonstrated that the only reaction path for o-benzyne with C60 leads to the [2+2] cycloaddition product in which benzyne adds across one of the interpentagonal bonds (forming a cyclobutene ring in the process). Either reaction product results in a loss of aromaticity and distortion of the PAH or fullerene substrate, and in a loss of strain in the benzyne. It is not clear, however, why different products are preferred in these cases. In the current paper, we consider the stability of benzyne-nanotube adducts and the ability of Brenner's potential energy model to describe the structure and stability of these adducts. The Brenner potential has been widely used for describing diamondoid and graphitic carbon. Recently it has also been used for molecular mechanics and molecular dynamics simulations of fullerenes and nanotubes. However, it has not been tested for the case of functionalized fullerenes (especially with highly strained geometries). We use the Brenner potential for our companion nanogear simulations and believe that it should be calibrated to insure that those simulations are physically reasonable. In the present work, Density Functional theory (DFT) calculations are used to determine the preferred geometric structures and energetics for this calibration. The DFT method is a kind of ab initio quantum chemistry method for determining the electronic structure of molecules. For a given basis set

  12. Zymosan-mediated inflammation impairs in vivo reverse cholesterol transport[S

    Malik, Priya; Berisha, Stela Z.; Santore, Jennifer; Agatisa-Boyle, Colin; Brubaker, Gregory; Smith, Jonathan D.

    2011-01-01

    Inflammation has been proposed to impair HDL function and reverse cholesterol transport (RCT). We investigated the effects of inflammation mediated by zymosan, a yeast glucan, on multiple steps along the RCT pathway in vivo and ex vivo. Acute inflammation with 70 mg/kg zymosan impaired RCT to plasma, liver, and feces similarly by 17–22% (P < 0.05), with no additional block at the liver. Hepatic gene expression further demonstrated no change in ABCG5, ABCB4, and ABCB11 expression but a decline in ABCG8 mRNA (32% P < 0.05). Plasma from zymosan-treated mice had a 21% decrease in cholesterol acceptor ability (P < 0.01) and a 35% decrease in ABCA1-specfic efflux capacity (P < 0.01) in vitro. Zymosan treatment also decreased HDL levels and led to HDL remodeling with increased incorporation of serum amyloid A. In addition, cholesterol efflux from cultured macrophages declined with zymosan treatment in a dose dependant manner. Taken together, our results suggest that zymosan impairs in vivo RCT primarily by decreasing macrophage-derived cholesterol entering the plasma, with minimal additional blocks downstream. Our study supports the notion that RCT impairment is one of the mechanisms for the increased atherosclerotic burden observed in inflammatory conditions. PMID:21335620

  13. Impaired GABAergic Neurotransmission in Schizophrenia Underlies Impairments in Cortical Gamma Band Oscillations

    McNally, James M.; McCarley, Robert W.; Brown, Ritchie E.

    2013-01-01

    Impairment of cortical circuit function is increasingly believed to be central to the pathophysiology of schizophrenia (Sz). Such impairments are suggested to result in abnormal gamma band oscillatory activity observed in Sz patients, and likely underlie the psychosis and cognitive deficits linked to this disease. Development of improved therapeutic strategies to enhance functional outcome of Sz patients is contingent upon a detailed understanding of the mechanisms behind the cortical circuit...

  14. A novel cognitive impairment mechanism that astrocytic p-connexin 43 promotes neuronic autophagy via activation of P2X7R and down-regulation of GLT-1 expression in the hippocampus following traumatic brain injury in rats.

    Sun, Liqian; Gao, Junling; Zhao, Manman; Cui, Jianzhong; Li, Youxiang; Yang, Xinjian; Jing, Xiaobin; Wu, Zhongxue

    2015-09-15

    Connexin 43 (Cx43) is one of the major gap junction proteins in astrocytes. Our previous studies reported that astrocytic phosphorylated Cx43 (p-CX43) regulated neuronic autophagy levels in the rat hippocampus after traumatic brain injury (TBI). In this study, we explored the underlying molecular mechanism by which gap junctional intercellular communication influenced neuronic autophagy and therefore initiated cognitive and memory impairments after TBI. The gap junctional blocker carbenoxolone (CBX) or autophagy inhibitor 3-methyladenine (3-MA) reduced latencies, as compared to TBI rats. Similarly, CBX or 3-MA restored long-term potentiation (LTP), relative to TBI hippocampal slices. Immunoblotting analysis showed that the expression of autophagy-related gene Beclin-1 in the hippocampus post-TBI were decreased in response to treatment with CBX, the P2X7 receptor (P2X7R) antagonist Oxidized ATP (OxATP) or ceftriaxone (Cef) which increased the expression and activity of the glutamate transporter (GLT-1) in the central nervous system (CNS). Moreover, CBX or OxATP pretreatment increased GLT-1 level in the rat hippocampus after TBI. However, CBX pretreatment suppressed P2X7R expression whereas maintained P2X7 level post-TBI. Confocal images revealed that p-CX43, P2X7 and GLT-1 strongly colocalized with glial fibrillary acidic protein (GFAP). Taken together, these results implied that Cx43, might induce neuronic autophagy by activation of P2X7R and reduce the expression of GLT-1 in the hippocampus, promoting TBI-induced cognitive deficits repair. Therefore, control of this communication may be serve as therapeutic strategies for intervention against TBI. PMID:26031379

  15. Effect of zirconium addition on the grain size and mechanical behavior of aluminum grain refined by titanium plus boron (Ti+B) in the as cast and cold extruded conditions

    Aluminum and its alloys are the second most commonly used metal for a variety of industrial applications. They normally solidify in coarse grain columnar structure which tends to reduce their mechanical behavior and surface quality. It was found that this large grain size structure can be refined by using titanium, Ti, or titanium plus boron, Ti+B, and using the latter resulted in reducing the amount of Ti to fifth its values although boron itself is not a grain refiner. This is why it is becoming customary in the aluminum foundry to add Ti or Ti+B to their melt before solidification. The available literature reveals that most of the work is directed towards the metallurgical aspects and little was directed on the mechanical aspects. To the best of the authors knowledge, no work was directed on the aspects of grain refiners on the formability of metals. In this paper, the effect of addition of Zr on the mechanical properties of commercially pure aluminum grain refined by Ti+B in the as cast and extruded conditions is investigated. Comparison between the addition of Zr alone or Zr+Ti+B is also investigated. It was found that addition of Ti+B either alone or in the presence of Zr resulted in grain refinement of aluminum both in the as cast and in the cold extruded conditions. The maximum reduction in grain size was 53.22% and 76.92%, respectively. Similarly, it was found that addition of Ti+B either alone or in the presence of Zr to Al resulted in improvement of its Vickers's hardness, However addition of Zr alone to Al resulted in decrease of its hardness in the as cast conditions but increase in the extruded condition .The maximum increase was in the case of adding both of them in the extruded condition being 94.59 %, (from Hv 37 to Hv72). Similarly the ultimate tensile strength, UTS, was improved at all additions except when Ti+B or Zr is added alone. On the whole it may be concluded that addition of Zr to Al grain refined by Ti+B resulted in enhancement of its

  16. Influence of additive system (Al2O3-RE2O3 , RE = Y, La, Nd, Dy, Yb on microstructure and mechanical properties of silicon nitride-based ceramics

    Juliana Marchi

    2009-06-01

    Full Text Available Silicon nitride based ceramics have been widely used as structural ceramics, due mainly to their thermo-mechanical properties such as high density, high thermal shock resistance, corrosion resistance and chemical stability. The aim of this study was to determine the influence of rare earth and aluminum oxide additions as sintering aids on densification, microstructure and mechanical properties of silicon nitride. Silicon nitride mixtures with 91 wt. (% Si3N4 and 9% wt. (% additives were prepared and sintered. The density, microstructure and mechanical properties of the sintered specimens of these mixtures were determined. In most specimens, scanning electron microscopic examination and X ray diffraction analysis revealed elongated grains of β-Si3N4 with aspect ratio of about 2.0 and dispersed in a glassy phase. The density of the sintered specimens was higher than 94% of the theoretical density (td and specimens with La2O3 and Al2O3 additions exhibited the highest value. The results of this investigation indicate that the rare earth ion size influences densification of silicon nitride, but this correlation was not observed in specimens containing two different rare earth oxides. The hardness values varied in direct proportion to the density of the specimens and the fracture toughness values were influenced by the composition of the intergranular glassy phase.

  17. Unpicking the Semantic Impairment in Alzheimer’s Disease: Qualitative Changes with Disease Severity

    Faye Corbett

    2012-01-01

    Full Text Available Despite a vast literature examining semantic impairment in Alzheimer's disease (AD, consensus regarding the nature of the deficit remains elusive. We re-considered this issue in the context of a framework that assumes semantic cognition can break down in two ways: (1 core semantic representations can degrade or (2 cognitive control mechanisms can become impaired [1]. We hypothesised and confirmed that the nature of semantic impairment in AD changes with disease severity. Patients at mild or severe stages of the disorder exhibited impairment across various semantic tasks but the nature of those deficits differed qualitatively for the two groups. Commensurate with early dysfunction of the cognitive control, temporoparietal-frontal-cingulate network, characteristics of deregulated semantic cognition were exhibited by the mild AD cases. In contrast, the severe AD group reproduced features of additional degradation of core semantic representations. These results suggest that spread of pathology into lateral anterior temporal lobes in later stage AD produces degradation of semantic representations, exacerbating the already deregulated system. Moreover, the dual nature of severe patients’ impairment was highlighted by disproportionately poor performance on tasks placing high demand on both conceptual knowledge and control processes–e.g., category fluency.

  18. Verbal memory impairments in dyslexia.

    Kramer, J H; Knee, K; Delis, D C

    2000-01-01

    Although verbal memory deficits are frequently reported in reading disabled children, the specific mechanisms underlying these impairments have yet to be clearly defined. The present study used the California Verbal Learning Test-Children's Version (CVLT-C) to assess verbal learning in 57 dyslexic children and 114 controls matched for gender, age, and WISC-R Vocabulary score. Three areas of verbal memory were investigated: Recall and recognition, use of learning strategies, and interference effects. The dyslexic group learned the list items more slowly, recalled fewer words on the last learning trial and the delayed trials, and performed less well on the recognition condition. Dyslexics and controls displayed similar vulnerability to interference, but group differences were evident in serial position effects. Taken together, our data suggest that dyslexics have less efficient rehearsal and encoding mechanisms, resulting in deficient encoding of new information, but normal retention and retrieval. PMID:14590570

  19. Chronic Hyponatremia Causes Neurologic and Psychologic Impairments.

    Fujisawa, Haruki; Sugimura, Yoshihisa; Takagi, Hiroshi; Mizoguchi, Hiroyuki; Takeuchi, Hideyuki; Izumida, Hisakazu; Nakashima, Kohtaro; Ochiai, Hiroshi; Takeuchi, Seiji; Kiyota, Atsushi; Fukumoto, Kazuya; Iwama, Shintaro; Takagishi, Yoshiko; Hayashi, Yoshitaka; Arima, Hiroshi; Komatsu, Yukio; Murata, Yoshiharu; Oiso, Yutaka

    2016-03-01

    Hyponatremia is the most common clinical electrolyte disorder. Once thought to be asymptomatic in response to adaptation by the brain, recent evidence suggests that chronic hyponatremia may be linked to attention deficits, gait disturbances, risk of falls, and cognitive impairments. Such neurologic defects are associated with a reduction in quality of life and may be a significant cause of mortality. However, because underlying diseases such as adrenal insufficiency, heart failure, liver cirrhosis, and cancer may also affect brain function, the contribution of hyponatremia alone to neurologic manifestations and the underlying mechanisms remain unclear. Using a syndrome of inappropriate secretion of antidiuretic hormone rat model, we show here that sustained reduction of serum sodium ion concentration induced gait disturbances; facilitated the extinction of a contextual fear memory; caused cognitive impairment in a novel object recognition test; and impaired long-term potentiation at hippocampal CA3-CA1 synapses. In vivo microdialysis revealed an elevated extracellular glutamate concentration in the hippocampus of chronically hyponatremic rats. A sustained low extracellular sodium ion concentration also decreased glutamate uptake by primary astrocyte cultures, suggesting an underlying mechanism of impaired long-term potentiation. Furthermore, gait and memory performances of corrected hyponatremic rats were equivalent to those of control rats. Thus, these results suggest chronic hyponatremia in humans may cause gait disturbance and cognitive impairment, but these abnormalities are reversible and careful correction of this condition may improve quality of life and reduce mortality. PMID:26376860

  20. Neural oscillatory deficits in schizophrenia predict behavioral and neurocognitive impairments.

    Martínez, Antígona; Gaspar, Pablo A; Hillyard, Steven A; Bickel, Stephan; Lakatos, Peter; Dias, Elisa C; Javitt, Daniel C

    2015-01-01

    Paying attention to visual stimuli is typically accompanied by event-related desynchronizations (ERD) of ongoing alpha (7-14 Hz) activity in visual cortex. The present study used time-frequency based analyses to investigate the role of impaired alpha ERD in visual processing deficits in schizophrenia (Sz). Subjects viewed sinusoidal gratings of high (HSF) and low (LSF) spatial frequency (SF) designed to test functioning of the parvo- vs. magnocellular pathways, respectively. Patients with Sz and healthy controls paid attention selectively to either the LSF or HSF gratings which were presented in random order. Event-related brain potentials (ERPs) were recorded to all stimuli. As in our previous study, it was found that Sz patients were selectively impaired at detecting LSF target stimuli and that ERP amplitudes to LSF stimuli were diminished, both for the early sensory-evoked components and for the attend minus unattend difference component (the Selection Negativity), which is generally regarded as a specific index of feature-selective attention. In the time-frequency domain, the differential ERP deficits to LSF stimuli were echoed in a virtually absent theta-band phase locked response to both unattended and attended LSF stimuli (along with relatively intact theta-band activity for HSF stimuli). In contrast to the theta-band evoked responses which were tightly stimulus locked, stimulus-induced desynchronizations of ongoing alpha activity were not tightly stimulus locked and were apparent only in induced power analyses. Sz patients were significantly impaired in the attention-related modulation of ongoing alpha activity for both HSF and LSF stimuli. These deficits correlated with patients' behavioral deficits in visual information processing as well as with visually based neurocognitive deficits. These findings suggest an additional, pathway-independent, mechanism by which deficits in early visual processing contribute to overall cognitive impairment in Sz. PMID