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Sample records for affecting plastic instability

  1. Kinesics of Affective Instability.

    ERIC Educational Resources Information Center

    Dil, Nasim

    1979-01-01

    Discusses the rationale of studying kinesics of affective instability, describes the phenonmenon of affective instability, examines the role of kinesics in the overall process of communication, and presents three case studies. (Author/AM)

  2. Plastic and dehydration instabilities of antigorite serpentinite

    NASA Astrophysics Data System (ADS)

    Ando, J.; Katayama, I.; Ohfuji, H.; Terada, Y.

    2008-12-01

    We conducted a constant displacement rate test of antigorite serpentinite by a triaxial solid medium deformation apparatus installed at Hiroshima University. Experimental conditions were P = ca. 1.0 GPa, T = 450 C to 800 C, which cover from stability to dehydration conditions of antigorite, and strain rate of digit of 10-5 /sec. Samples were cylindrical shape cored from serpentinite and their sizes were 7 mm x 7 mm and 5 mm x 5 mm in diameter by length. Faults were observed in recovered samples from all temperature conditions. Mechanical data of faulted samples showed stress drop of several 10 MPa during experiments. The followings summarize microstructural observations of the recovered samples, and propose generation processes of fault at stability and dehydration conditions. 1) Stability field (plastic instability): Antigorite grains develop a lattice preferred orientation (LPO) along a fault, which characterized by (001) cleavage face parallel to fault plane. This fact suggests the fault is generated by the following process. i) Antigorite grains on the plane applied by maximum shear stress are preferentially deformed by plastic manner, and then develop the LPO. ii) The arrangement of cleavage face gradually reduces the strength of this plane. iii) Eventually, embrittlement occurs at the critical point when the rock strength along this weak plane becomes smaller than shear stress. 2) Dehydration condition (dehydration instability): Fine grained dehydration phases less than 1 micrometer in size such as olivine and talc are detected as a thin vein along the fault. Moreover, talc and olivine, or antigorite ca. 1 - 5 micrometers in size with angular shape are observed within the fault as a fault gauge. These facts suggest the following generation process of fault. i) Dehydration reaction of antigorite begins on the plane applied by maximum shear stress and expands along this plane. ii) The dehydration gradually reduces the strength of this plane. iii) Eventually

  3. Plastic instabilities in statically and dynamically loaded spherical vessels

    SciTech Connect

    Duffey, Thomas A; Rodriguez, Edward A

    2010-01-01

    Significant changes were made in design limits for pressurized vessels in the 2007 version of the ASME Code (Section VIII, Div. 3) and 2008 and 2009 Addenda. There is now a local damage-mechanics based strain-exhaustion limit as well as the well-known global plastic collapse limit. Moreover, Code Case 2564 (Section VIII, Div. 3) has recently been approved to address impulsively loaded vessels. It is the purpose of this paper to investigate the plastic collapse limit as it applies to dynamically loaded spherical vessels. Plastic instabilities that could potentially develop in spherical shells under symmetric loading conditions are examined for a variety of plastic constitutive relations. First, a literature survey of both static and dynamic instabilities associated with spherical shells is presented. Then, a general plastic instability condition for spherical shells subjected to displacement controlled and impulsive loading is given. This instability condition is evaluated for six plastic and visco-plastic constitutive relations. The role of strain-rate sensitivity on the instability point is investigated. Calculations for statically and dynamically loaded spherical shells are presented, illustrating the formation of instabilities as well as the role of imperfections. Conclusions of this work are that there are two fundamental types of instabilities associated with failure of spherical shells. In the case of impulsively loaded vessels, where the pulse duration is short compared to the fundamental period of the structure, one instability type is found not to occur in the absence of static internal pressure. Moreover, it is found that the specific role of strain-rate sensitivity on the instability strain depends on the form of the constitutive relation assumed.

  4. Toward a definition of affective instability.

    PubMed

    Renaud, Suzane M; Zacchia, Camillo

    2012-01-01

    Affective instability is a psychophysiological symptom observed in some psychopathologies. It is a complex construct that encompasses (1) primary emotions, or affects, and secondary emotions, with each category having its own characteristics, amplitude, and duration, (2) rapid shifting from neutral or valenced affect to intense affect, and (3) dysfunctional modulation of emotions. Affective instability is often confused with mood lability, as in bipolar disorders, as well as with other terms. To clarify the concept, we searched databases for the term affective instability and read related articles on the topic. In this article we situate the term within the current affective nomenclature and human emotional experience, explore its psychophysiological features, and place it within the context of psychopathology. We explain why the term can potentially be confused with mood pathology and then define affective instability as an inherited temperamental trait modulated by developmental experience.

  5. Directional plasticity of clay showing instability

    NASA Astrophysics Data System (ADS)

    Fortuna, Sonia

    2010-06-01

    A graphical approach is used to sketch the field of small plastic strains (epsilon < 0.1 %) of Pisa clay along different axi-symmetric stress paths associated to a partial confining stress reduction. Within the classic framework of elasto-plasticity, volumetric and deviatoric plastic strains contours are determined from data obtained from triaxial tests, assuming a cross-anisotropic hypo-elastic formulation calibrated on a wide set of tests and with non linear evolution of the elastic moduli calibrated along a quasi-1D swelling stress path. The evolutions of the plastic strains and of the plastic strain vectors are shown along the stress path directly explored with tests and along virtual paths interpolated from the actual data along intermediate directions at various strain levels.

  6. Instability phenomena in plasticity: Modelling and computation

    NASA Astrophysics Data System (ADS)

    Stein, E.; Steinmann, P.; Miehe, C.

    1995-12-01

    We presented aspects and results related to the broad field of strain localization with special focus on large strain elastoplastic response. Therefore, we first re-examined issues related to the classification of discontinuities and the classical description of localization with a particular emphasis on an Eulerian geometric representation. We touched the problem of mesh objectivity and discussed results of a particular regularization method, namely the micropolar approach. Generally, regularization has to preserve ellipticity and to reflect the underlying physics. For example ductile materials have to be modelled including viscous effects whereas geomaterials are adequately described by the micropolar approach. Then we considered localization phenomena within solids undergoing large strain elastoplastic deformations. Here, we documented the influence of isotropic damage on the failure analysis. Next, the interesting influence of an orthotropic yield condition on the spatial orientation of localized zones has been studied. Finally, we investigated the localization condition for an algorithmic model of finite strain single crystal plasticity.

  7. Shape optimization of a pressure vessel under plastic flow, plastic instability, weight and fatigue life criteria

    NASA Astrophysics Data System (ADS)

    El Abdi, R.; Touratier, M.; Convert, P.; Lalanne, B.

    1994-06-01

    The structural shape optimization of a complex shell under complex criteria is presented. The shell is one of various cases of a turboshaft, and optimization criteria are associated with the cost, the technology, and above all the working conditions for the turboshaft. Optimization criteria involved are of course the weight of the structure, but also the plastic flow, plastic instability and fatigue life. The fatigue life criterion is an extension to the three-dimensional state of the one-dimensional Lemaitre-Chaboche rule, taking into account the elasto-plastic Neuber correction. All computations have been made with the ANSYS finite element program in which an optimization module exists.

  8. Mechanical instabilities in periodic porous elasto-plastic solids.

    NASA Astrophysics Data System (ADS)

    Singamaneni, Srikanth; Bertoldi, Katia; Chang, Sehoon; Jang, Ji-Hyun; Young, Seth; Thomas, Edwin; Boyce, Mary; Tsukruk, Vladimir

    2009-03-01

    We describe the transformation of the periodic microporous structures fabricated by interference lithography followed by their freezing below glass transition. Periodic porous microstructures subjected to internal compressive stresses can undergo sudden structural transformation at a critical strain. The pattern transformation of collapsed pores is caused by the stresses originated during the polymerization of acrylic acid (rubbery component) inside of cylindrical pores and the subsequent solvent evaporation in the organized microporous structure. The results of a non-linear numerical investigation confirm the critical role of the bifurcation of the periodic solid under compressive stresses. In striking contrast to the earlier observations of elastic instabilities in porous elastomeric solids, the elastic-plastic nature of the crosslinked periodic microstructure studied here provides for the ability to lock in the transformed pattern with complete relaxation of the internal stresses. By confining the polymerization of acrylic acid to localized porous areas complex microscopic periodic structures are obtained.

  9. Plastic instability behavior of bcc and hcp metals after low temperature neutron irradiation

    NASA Astrophysics Data System (ADS)

    Byun, T. S.; Farrell, K.; Hashimoto, N.

    2004-08-01

    Plastic instability in uniaxial tensile deformation has been investigated for the body centered cubic (bcc) and hexagonal close packed (hcp) pure metals, V, Nb, Mo, and Zr, after low temperature (60-100 °C) neutron irradiation up to 0.7 dpa. Relatively ductile metals, V, Nb, and Zr, experienced uniform deformation prior to necking at low doses and prompt plastic instability at yield at high doses. Mo failed in a brittle mode within the elastic limit at doses above 0.0001 dpa. V showed a quasi-brittle failure at the highest dose of 0.69 dpa. In the ductile metals, plastic instability at yield occurred when the yield stress exceeded the plastic instability stress (PIS), which was nearly independent of dose. The PIS values for V, Nb, Mo, and Zr were about 390, 370, 510, and 170 MPa, respectively. The coincidence of plastic instability at yield and dislocation channeling cannot be generalized for all metallic materials.

  10. Affective instability in patients with chronic pain: a diary approach.

    PubMed

    Rost, Silke; Van Ryckeghem, Dimitri M L; Koval, Peter; Sütterlin, Stefan; Vögele, Claus; Crombez, Geert

    2016-08-01

    Affective instability, conceptualized as fluctuations in mood over time, has been related to ill-health and psychopathology. In this study, we examined the role of affective instability on daily pain outcomes in 70 patients with chronic pain (Mage = 49.7 years; 46 females) using an end-of-day diary. During a baseline phase, patients completed self-reported questionnaires of pain severity, pain duration, disability, depression, and anxiety. During a subsequent diary phase, patients filled out an electronic end-of-day diary over 14 consecutive days assessing daily levels of pain severity, disability, cognitive complaints, negative affect (NA) and positive affect. Affective instability was operationalized as the mean square of successive differences in daily mood (separately for NA and positive affect), which takes into account the size of affective changes over consecutive days. Results indicated that NA instability was positively associated with daily disability, beyond the effects of daily pain severity. Furthermore, NA instability moderated the relationship between daily pain severity and daily disability and the relationship between daily pain severity and daily cognitive complaints. Positive affect instability, however, showed to be unrelated to all outcomes. Current findings extend previous results and reveal the putative role of affective instability on pain-related outcomes and may yield important clinical implications. Indeed, they suggest that targeting NA instability by improving emotion regulation skills may be a strategy to diminish disability and cognitive complaints in patients with chronic pain.

  11. How Funding Instability Affects Army Programs

    DTIC Science & Technology

    2007-01-01

    with LTC Philip Carey , Javelin project manager in the Close Combat Weapon Systems Program Management Office, and with Lloyd Olson, cost and budget...Black = Non-Army White = Army No growth Sample size D ev el o p m en t co st g ro w th f ac to r Sample size ratio 31% 32% 35% 25%36% Years after... ana - lysts have discussed instability in DoD programs for a long time, they have not developed funding instability measures that could help address

  12. How Funding Instability Affects Army Programs

    DTIC Science & Technology

    2007-01-01

    program benefited from discussions with LTC Philip Carey , Javelin project manager in the Close Combat Weapon Systems Program Management Office, and with...44 20 40 19 30 17 20 11 15 5 Black = Non-Army White = Army No growth Sample size D ev el o p m en t co st g ro w th f ac to r Sample size ratio 31...clearly defined measures. Although ana - lysts have discussed instability in DoD programs for a long time, they have not developed funding instability

  13. Affective instability, childhood trauma and major affective disorders.

    PubMed

    Marwaha, S; Gordon-Smith, K; Broome, M; Briley, P M; Perry, A; Forty, L; Craddock, N; Jones, I; Jones, L

    2016-01-15

    Affective instability (AI), childhood trauma, and mental illness are linked, but evidence in affective disorders is limited, despite both AI and childhood trauma being associated with poorer outcomes. Aims were to compare AI levels in bipolar disorder I (BPI) and II (BPII), and major depressive disorder recurrent (MDDR), and to examine the association of AI and childhood trauma within each diagnostic group. AI, measured using the Affective Lability Scale (ALS), was compared between people with DSM-IV BPI (n=923), BPII (n=363) and MDDR (n=207) accounting for confounders and current mood. Regression modelling was used to examine the association between AI and childhood traumas in each diagnostic group. ALS scores in descending order were BPII, BPI, MDDR, and differences between groups were significant (p<0.05). Within the BPI group any childhood abuse (p=0.021), childhood physical abuse (p=0.003) and the death of a close friend in childhood (p=0.002) were significantly associated with higher ALS score but no association was found between childhood trauma and AI in BPII and MDDR. The ALS is a self-report scale and is subject to retrospective recall bias. AI is an important dimension in bipolar disorder independent of current mood state. There is a strong link between childhood traumatic events and AI levels in BPI and this may be one way in which exposure and disorder are linked. Clinical interventions targeting AI in people who have suffered significant childhood trauma could potentially change the clinical course of bipolar disorder. Copyright © 2015 Elsevier B.V. All rights reserved.

  14. Hydrodynamic instability of elastic-plastic solid plates at the early stage of acceleration

    NASA Astrophysics Data System (ADS)

    Piriz, A. R.; Sun, Y. B.; Tahir, N. A.

    2015-03-01

    A model is presented for the linear Rayleigh-Taylor instability taking place at the early stage of acceleration of an elastic-plastic solid, when the shock wave is still running into the solid and is driven by a time varying pressure on the interface. When the the shock is formed sufficiently close to the interface, this stage is considered to follow a previous initial phase controlled by the Ritchmyer-Meshkov instability that settles new initial conditions. The model reproduces the behavior of the instability observed in former numerical simulation results and provides a relatively simpler physical picture than the currently existing one for this stage of the instability evolution.

  15. Genetic instability in Streptomyces ambofaciens: inducibility and associated genome plasticity.

    PubMed

    Simonet, J M; Schneider, D; Volff, J N; Dary, A; Decaris, B

    1992-06-15

    DNA amplification and deletions occur at high frequency in unstable regions localized on the Streptomyces ambofaciens chromosome. The structure of these regions was investigated, leading to the identification of internal reiterations which could play a role in the deletion and/or amplification mechanism(s). UV irradiation and treatments with mitomycin C, oxolinic acid and novobiocin were shown to efficiently induce genetic instability. Finally, mutator strains were isolated, in which genetic instability was dramatically increased. The involvement of an SOS-like response in genetic instability in S. ambofaciens is proposed.

  16. Plastic Instabilities and Their Consequences in Steels and Other High Strength Alloys

    DTIC Science & Technology

    1991-09-01

    rate yes Superalloys * Alloy 600 quasi-static no Rend 41 quasi-static no Steels * HY80 quasi-static no ultra-soft5 no low temperatures no AISI 4340...AD-A240 976 ([f) A Final Technical Report Contract No. N00014-88-K-0111 S PLASTIC INSTABILITIES AND THEIR CONSEQUENCES IN STEELS AND OTHER HIGH...PLASTIC INSTABILITIES AND THEIR CONSEQUENCES IN STEELS AND OTHER HIGH STRENGTH ALLOYS Submitted to: Office of Naval Research 800 North Quincy Street

  17. Effects of Initial Conditions on Rayleigh-Taylor Instability in Elastic-Plastic Materials

    NASA Astrophysics Data System (ADS)

    Roach, Pamela; Banerjee, Arindam

    2012-11-01

    In contrast to Newtonian fluids, experimental study of Rayleigh Taylor instability (RTI) in accelerated solids is traditionally hindered by difficulty to measure material properties and exceedingly small time scales of the processes. When an elastic-plastic solid is accelerated due to a density gradient, the instability is dependent on the material's mechanical strength, initial conditions, and acceleration that drive the instability. RTI in solids is observed in supernovas, explosive welding, and inertial confinement fusion. A novel experimental technique is used to study the effects of initial conditions and variable accelerations on the growth and instability in an elastic-plastic solid. The experiment consists of a container filled with air and mayonnaise, a non-Newtonian emulsion, with an initial perturbation between the two materials. Single mode perturbations of various amplitudes are analyzed and effects of two-dimensional versus three-dimensional interfaces are discussed. Furthermore, the instability threshold and stable elastic and plastic regions are investigated by controlling the acceleration. The instability threshold and perturbation growth rate are compared to linear analysis of incompressible RTI. The authors acknowledge financial support through DOE-LANL subcontract # 173667-1.

  18. Spectral and dynamic analysis of plastic instabilities during serrated creep of the aluminum-magnesium alloy

    NASA Astrophysics Data System (ADS)

    Shibkov, A. A.; Zolotov, A. E.; Zheltov, M. A.; Denisov, A. A.; Gasanov, M. F.

    2014-05-01

    The force response to the development of a macroscopic plastic deformation jump under the conditions of serrated creep of the aluminummagnesium alloy 5456 has been studied using spectral and dynamic analysis methods. The flicker-noise structure of the force response indicating the self-organized criticality state has been revealed. It has been found that a short-term state of plastic instability flatter spontaneously appears during the development of the macroscopic deformation step.

  19. Colored plastic mulch microclimates affect strawberry fruit yield and quality

    NASA Astrophysics Data System (ADS)

    Shiukhy, Saeid; Raeini-Sarjaz, Mahmoud; Chalavi, Vida

    2015-08-01

    Significant reduction of strawberry ( Fragaria × ananassa, Duch.) fruit yield and quality, as a consequence of conventional cultivation method, is common in the Caspian Sea region, Iran. Recently, growers started using plastic mulches to overcome these shortcomings. Plastic mulches have different thermal and radiation properties and could affect strawberry fruit yield and quality. In the present study, the effect of different colored plastic mulches (black, red, and white) along with conventional practice was tested on yield and quality of strawberry Camarosa cultivar, in a completely randomized block design. Colored plastic mulches had highly significant effect on fruit weight, size, and phytochemical contents. In the most harvest times, mean fruit weight was significantly higher in red plastic relative to white and control treatments. Total fruit weight of plastic mulches was not significantly different, while all were statistically higher than that of control. Fruit size significantly increased over red plastic mulch. Total fruit numbers over plastic mulches were significantly higher than that of control treatment. The content of phenolic compounds was similar between treatments, while anthocyanin content, IC50 value, and flavonoid content significantly were affected by colored plastics. In conclusion, colored plastic mulches could affect strawberry fruit weight and quality through altering strawberry thermal and radiation environment.

  20. Colored plastic mulch microclimates affect strawberry fruit yield and quality.

    PubMed

    Shiukhy, Saeid; Raeini-Sarjaz, Mahmoud; Chalavi, Vida

    2015-08-01

    Significant reduction of strawberry (Fragaria × ananassa, Duch.) fruit yield and quality, as a consequence of conventional cultivation method, is common in the Caspian Sea region, Iran. Recently, growers started using plastic mulches to overcome these shortcomings. Plastic mulches have different thermal and radiation properties and could affect strawberry fruit yield and quality. In the present study, the effect of different colored plastic mulches (black, red, and white) along with conventional practice was tested on yield and quality of strawberry Camarosa cultivar, in a completely randomized block design. Colored plastic mulches had highly significant effect on fruit weight, size, and phytochemical contents. In the most harvest times, mean fruit weight was significantly higher in red plastic relative to white and control treatments. Total fruit weight of plastic mulches was not significantly different, while all were statistically higher than that of control. Fruit size significantly increased over red plastic mulch. Total fruit numbers over plastic mulches were significantly higher than that of control treatment. The content of phenolic compounds was similar between treatments, while anthocyanin content, IC(50) value, and flavonoid content significantly were affected by colored plastics. In conclusion, colored plastic mulches could affect strawberry fruit weight and quality through altering strawberry thermal and radiation environment.

  1. Effects of initial conditions on Rayleigh-Taylor instability using elastic-plastic materials

    NASA Astrophysics Data System (ADS)

    Roach, Pamela Susan

    When an elastic-plastic solid is accelerated by a fluid of lower density, Rayleigh- Taylor instability (RTI) is observed, and the instability is mitigated by the material's mechanical strength, initial conditions, and the acceleration that drives the instability. Such instances of RTI are observed in supernovas, explosive welding, and inertial confinement fusion. In contrast to Newtonian fluids, experimental study of RTI in accelerated solids is traditionally hindered by difficulty to measure material properties and exceedingly small time scales. An understanding of the role initial conditions and material properties have on the growth of RTI will lead to better control of the instability. We present the results for a series of experiments to study the effect of amplitude and wavelength on RT instability with an elastic-plastic solid. A novel rotating wheel RT experiment that uses centrifugal forces to accelerate the two-material interface is used for this purpose. The experiment consists of a container filled with air and mayonnaise, a non-Newtonian emulsion, with an initial perturbation between the two materials. Single mode perturbations of various amplitudes and wavelength were analyzed and results found the instability required for acceleration was inversely proportional to both initial amplitude and wavelength. Three-dimensional (3D) interfaces were found to be more stable than two-dimensional (2D) interfaces. Elastic and plastic peak amplitude responses were observed for stable interfaces using a variable acceleration profile where the test section was first accelerated to slightly below the critical acceleration and then decelerated at the same rate. This exercise allowed for verification of the elastic-plastic (EP) transition process before instability was reached.

  2. Experimental investigation of Rayleigh Taylor instability in elastic-plastic materials

    NASA Astrophysics Data System (ADS)

    Haley, Aaron Alan; Banerjee, Arindam

    2010-11-01

    The interface of an elastic-plastic plate accelerated by a fluid of lower density is Rayleigh Taylor (RT) unstable, the growth being mitigated by the mechanical strength of the plate. The instability is observed when metal plates are accelerated by high explosives, in explosive welding, and in volcanic island formation due to the strength of the inner crust. In contrast to the classical case involving Newtonian fluids, RT instability in accelerated solids is not well understood. The difficulties for constructing a theory for the linear growth phase in solids is essentially due to the character of elastic-plastic constitutive properties which has a nonlinear dependence on the magnitude of the rate of deformation. Experimental investigation of the phenomena is difficult due to the exceedingly small time scales (in high energy density experiments) and large measurement uncertainties of material properties. We performed experiments on our Two-Wheel facility to study the linear stage of the incompressible RT instability in elastic-plastic materials (yogurt) whose properties were well characterized. Rotation of the wheels imparted a constant centrifugal acceleration on the material interface that was cut with a small sinusoidal ripple. The controlled initial conditions and precise acceleration amplitudes are levied to investigate transition from elastic to plastic deformation and allow accurate and detailed measurements of flow properties.

  3. Magnetic field generation by the Rayleigh-Taylor instability in laser-driven planar plastic targets.

    PubMed

    Gao, L; Nilson, P M; Igumenschev, I V; Hu, S X; Davies, J R; Stoeckl, C; Haines, M G; Froula, D H; Betti, R; Meyerhofer, D D

    2012-09-14

    Magnetic fields generated by the Rayleigh-Taylor instability were measured in laser-accelerated planar foils using ultrafast proton radiography. Thin plastic foils were irradiated with ∼4-kJ, 2.5-ns laser pulses focused to an intensity of ∼10(14)  W/cm(2) on the OMEGA EP Laser System. Target modulations were seeded by laser nonuniformities and amplified during target acceleration by the Rayleigh-Taylor instability. The experimental data show the hydrodynamic evolution of the target and MG-level magnetic fields generated in the broken foil. The experimental data are in good agreement with predictions from 2-D magnetohydrodynamic simulations.

  4. Vestibular plasticity following orbital spaceflight: recovery from postflight postural instability

    NASA Technical Reports Server (NTRS)

    Black, F. O.; Paloski, W. H.; Doxey-Gasway, D. D.; Reschke, M. F.

    1995-01-01

    Results of previous studies suggested that the vestibular mediated postural instability observed in astronauts upon return to earth from orbital spaceflight may be exacerbated by an increased weighting of visual inputs for spatial orientation and control of movement. This study was performed to better understand the roles of visual and somatosensory contributions to recovery of normal sensori-motor postural control in returning astronauts. Preflight and postflight, 23 astronaut volunteers were presented randomly with three trials of six sensory organization test (SOT) conditions in the EquiTest system test battery. Sagittal plane center-of-gravity (COG) excursions computed from ground reaction forces were significantly higher on landing day than preflight for those test conditions presenting sway-referenced visual and/or somatosensory orientation cues. The ratio of summed peak-to-peak COG sway amplitudes on the two sway-referenced vision tests (SOTs 3 + 6) compared to the two eyes closed tests (SOTs 2 + 5) was increased on landing day, indicating an increased reliance on visual orientation cues for postural control. The ratio of peak-to-peak COG excursions on sway-referenced surfaces (SOTs 4, 5 & 6) to an earth fixed support surfaces (SOTs 1, 2 & 3) increased even more after landing suggesting primary reliance on somatosensory orientation cues for recovery of postflight postural stability. Readaptation to sway-referenced support surfaces took longer than readaptation to sway-referenced vision. The increased reliance on visual and somatosensory inputs disappeared in all astronauts 4-8 days following return to earth.

  5. Vestibular plasticity following orbital spaceflight: recovery from postflight postural instability

    NASA Technical Reports Server (NTRS)

    Black, F. O.; Paloski, W. H.; Doxey-Gasway, D. D.; Reschke, M. F.

    1995-01-01

    Results of previous studies suggested that the vestibular mediated postural instability observed in astronauts upon return to earth from orbital spaceflight may be exacerbated by an increased weighting of visual inputs for spatial orientation and control of movement. This study was performed to better understand the roles of visual and somatosensory contributions to recovery of normal sensori-motor postural control in returning astronauts. Preflight and postflight, 23 astronaut volunteers were presented randomly with three trials of six sensory organization test (SOT) conditions in the EquiTest system test battery. Sagittal plane center-of-gravity (COG) excursions computed from ground reaction forces were significantly higher on landing day than preflight for those test conditions presenting sway-referenced visual and/or somatosensory orientation cues. The ratio of summed peak-to-peak COG sway amplitudes on the two sway-referenced vision tests (SOTs 3 + 6) compared to the two eyes closed tests (SOTs 2 + 5) was increased on landing day, indicating an increased reliance on visual orientation cues for postural control. The ratio of peak-to-peak COG excursions on sway-referenced surfaces (SOTs 4, 5 & 6) to an earth fixed support surfaces (SOTs 1, 2 & 3) increased even more after landing suggesting primary reliance on somatosensory orientation cues for recovery of postflight postural stability. Readaptation to sway-referenced support surfaces took longer than readaptation to sway-referenced vision. The increased reliance on visual and somatosensory inputs disappeared in all astronauts 4-8 days following return to earth.

  6. Exploring elastic and plastic regimes of Rayleigh-Taylor instability in solids

    NASA Astrophysics Data System (ADS)

    Polavarapu, Rinosh; Banerjee, Arindam

    2014-11-01

    The elastic-plastic (EP) transition stage of Rayleigh-Taylor (RT) instability was studied in an accelerated elastic-plastic solid. A novel rotating wheel RT experiment with linear vibratory motion that centrifugally accelerates a test section with two-material interface was utilized. The test section consists of a container filled with air and mayonnaise, a non-Newtonian emulsion, with an initial perturbation between the two materials. Single mode perturbations of various amplitudes and wavelengths were analyzed earlier to find the effects of initial conditions on instability acceleration. Presently, the EP transition process for a stable interface before reaching the instability was verified by accelerating the test section to a magnitude which is slightly less than critical acceleration and imparting linear vibration which alters the radius of circular path and thus varies the magnitude of centrifugal force. The results were compared with various instability and EP transition criteria given by analytical growth models. The authors acknowledge support of the DOE-SSAP (Grant # DE-NA0001975) and DOE-LANL subcontract (Grant #173-667-1).

  7. Hypersonic boundary layer instabilities affected by various porous surfaces

    NASA Astrophysics Data System (ADS)

    Wang, Xiaowen; Zhong, Xiaolin

    2010-11-01

    Hypersonic boundary layer instabilities of a Mach 5.92 flow over a flat plate affected by various porous surfaces are studied by numerical simulations. Steady base flow is obtained by solving compressible Navier-Stokes equations with a fifth-order shock-fitting method and a second-order TVD scheme. Stability simulations consist of two steps: (1) disturbances corresponding to a single boundary layer wave (mode F or mode S) are superimposed at a cross-section of the boundary layer near the leading edge to show spatial development of the wave; (2) porous coatings are used downstream of the superimposed wave to investigate its effect on boundary-layer instabilities. The results show that porous coating only has local effects on the instabilities of mode S and mode F. In porous region, Mack's first mode is destabilized whereas Mack's second mode and Mode F are stabilized. For felt-metal porous coating, destabilization of Mack's first mode is so significant that disturbances are slightly destabilized when porous coating are put on the whole flat plate. At approximately the same porosity, regular structure porous coating is weaker in first mode destabilization and second mode stabilization than felt-metal porous coating.

  8. Application of critical COD and plastic instability concepts to fracture of shells. [Crack Opening Displacement

    NASA Technical Reports Server (NTRS)

    Erdogan, F.; Ratwani, M.

    1974-01-01

    The paper deals with the initiation, growth, and possible arrest of fracture in shell structures containing initial defects which may be approximated by an isolated part-through crack. The main study is restricted to the structures in which the net section of the shell wall around the defect zone is fully yielded. The problem is solved by using an 8th order shallow shell theory with a conventional plastic strip model to account for the plastic deformations. Using the critical COD or the plastic instability as fracture criterion, the results are applied to the fracture propagation and arrest in shells. The calculated results are then compared with those obtained from the experiments on zircaloy, aluminum, and steel pipes.

  9. Application of critical COD and plastic instability concepts to fracture of shells. [Crack Opening Displacement

    NASA Technical Reports Server (NTRS)

    Erdogan, F.; Ratwani, M.

    1974-01-01

    The paper deals with the initiation, growth, and possible arrest of fracture in shell structures containing initial defects which may be approximated by an isolated part-through crack. The main study is restricted to the structures in which the net section of the shell wall around the defect zone is fully yielded. The problem is solved by using an 8th order shallow shell theory with a conventional plastic strip model to account for the plastic deformations. Using the critical COD or the plastic instability as fracture criterion, the results are applied to the fracture propagation and arrest in shells. The calculated results are then compared with those obtained from the experiments on zircaloy, aluminum, and steel pipes.

  10. Experimental and numerical study of plastic shear instability under high-speed loading conditions

    SciTech Connect

    Sokovikov, Mikhail E-mail: naimark@icmm.ru; Chudinov, Vasiliy E-mail: naimark@icmm.ru; Bilalov, Dmitry E-mail: naimark@icmm.ru; Oborin, Vladimir E-mail: naimark@icmm.ru; Uvarov, Sergey E-mail: naimark@icmm.ru; Plekhov, Oleg E-mail: naimark@icmm.ru; Terekhina, Alena E-mail: naimark@icmm.ru; Naimark, Oleg E-mail: naimark@icmm.ru

    2014-11-14

    The behavior of specimens dynamically loaded during the split Hopkinson (Kolsky) bar tests in a regime close to simple shear conditions was studied. The lateral surface of the specimens was investigated in a real-time mode with the aid of a high-speed infra-red camera CEDIP Silver 450M. The temperature field distribution obtained at different time made it possible to trace the evolution of plastic strain localization. The process of target perforation involving plug formation and ejection was examined using a high-speed infra-red camera and a VISAR velocity measurement system. The microstructure of tested specimens was analyzed using an optical interferometer-profilometer and a scanning electron microscope. The development of plastic shear instability regions has been simulated numerically.

  11. Effect of bromine-dopant on radiation-driven Rayleigh-Taylor instability in plastic foil

    NASA Astrophysics Data System (ADS)

    Xu, Binbin; Ma, Yanyun; Yang, Xiaohu; Tang, Wenhui; Ge, Zheyi; Zhao, Yuan; Ke, Yanzhao; Kawata, Shiego

    2017-10-01

    Effects of bromine (Br) dopant on the growth of radiation-driven ablative Rayleigh-Taylor instability (RTI) in plastic foils are studied by radiation hydrodynamics simulations and theoretical analysis. It is found that the Br-dopant in plastic foil reduces the seed of ablative RTI. The main reasons of the reduction are attributed to the smaller oscillation amplitude of ablative Richtmyer-Meshkov instability (RMI) induced by the smaller post-shock sound speed, and the smaller oscillation frequency of ablative RMI induced by the smaller ablation velocity and blow-off plasma velocity. The Br-dopant also decreases the linear growth rate of ablative RTI due to the smaller acceleration. Treating the perturbation growth as a function of foil’s displacement, the perturbation growth would increase in Br-doped foil at the phase of ablative RTI, which is attributed to the decrease of the ablation velocity and the density gradient scale length. The results are helpful for further understanding the influence of high-Z dopant on the radiation-driven ablative RTI.

  12. Effects of acceleration rate on Rayleigh-Taylor instability in elastic-plastic materials

    NASA Astrophysics Data System (ADS)

    Banerjee, Arindam; Polavarapu, Rinosh

    2016-11-01

    The effect of acceleration rate in the elastic-plastic transition stage of Rayleigh-Taylor instability in an accelerated non-Newtonian material is investigated experimentally using a rotating wheel experiment. A non-Newtonian material (mayonnaise) was accelerated at different rates by varying the angular acceleration of a rotating wheel and growth patterns of single mode perturbations with different combinations of amplitude and wavelength were analyzed. Experiments were run at two different acceleration rates to compare with experiments presented in prior years at APS DFD meetings and the peak amplitude responses are captured using a high-speed camera. Similar to the instability acceleration, the elastic-plastic transition acceleration is found to be increasing with increase in acceleration rate for a given amplitude and wavelength. The experimental results will be compared to various analytical strength models and prior experimental studies using Newtonian fluids. Authors acknowledge funding support from Los Alamos National Lab subcontract(370333) and DOE-SSAA Grant (DE-NA0001975).

  13. Prediction of plastic instabilities under thermo-mechanical loadings in tension and simple shear

    NASA Astrophysics Data System (ADS)

    Manach, P. Y.; Mansouri, L. F.; Thuillier, S.

    2016-08-01

    Plastic instabilities like Portevin-Le Châtelier were quite thoroughly investigated experimentally in tension, under a large range of strain rates and temperatures. Such instabilities are characterized both by a jerky flow and a localization of the strain in bands. Similar phenomena were also recorded for example in simple shear [1]. Modelling of this phenomenon is mainly performed at room temperature, taking into account the strain rate sensitivity, though an extension of the classical Estrin-Kubin-McCormick was proposed in the literature, by making some of the material parameters dependent on temperature. A similar approach is considered in this study, furthermore extended for anisotropic plasticity with Hill's 1948 yield criterion. Material parameters are identified at 4 different temperatures, ranging from room temperature up to 250°C. The identification procedure is split in 3 steps, related to the elasticity, the average stress level and the magnitude of the stress drops. The anisotropy is considered constant in this temperature range, as evidenced by experimental results [2]. The model is then used to investigate the temperature dependence of the critical strain, as well as its capability to represent the propagation of the bands. Numerical predictions of the instabilities in tension and simple shear at room temperature and up to 250°C are compared with experimental results [3]. In the case of simple shear, a monotonic loading followed by unloading and reloading in the reverse direction (“Bauschinger-type” test) is also considered, showing that (i) kinematic hardening should be taken into account to fully describe the transition at re-yielding (ii) the modelling of the critical strain has to be improved.

  14. The role of affective instability and UPPS impulsivity in borderline personality disorder features.

    PubMed

    Tragesser, Sarah L; Robinson, R Joe

    2009-08-01

    Current theories of borderline personality disorder (BPD) suggest that extreme levels of affective instability/emotional dysregulation, impulsivity, or a combination of these traits account for the symptoms of BPD. The present study tested the extent to which personality measures of affective instability and impulsivity could account for BPD features in a nonclinical sample. One hundred forty-one undergraduates completed the Affective Lability Scale, the UPPS Impulsive Behavior Scale, and the Personality Assessment Inventory for Borderlines. Both affective instability and impulsivity were uniquely associated with BPD features. Shifts between euthymia and anger, and between anxiety and depression, were associated with BPD features, as were the urgency and (lack of) premeditation scales. Results indicated that specific BPD features may be differentially accounted for by affective instability vs. impulsivity, consistent with perspectives on BPD emphasizing combinations of affective instability and impulsivity as underlying dimensions of the disorder.

  15. An elastic-plastic finite element analysis of crack initiation, stable crack growth, and instability

    NASA Technical Reports Server (NTRS)

    Newman, J. C., Jr.

    1984-01-01

    Studies have been conducted to develop efficient techniques to simulate crack extension and to examine various local and global fracture criteria. Of the considered criteria, the crack-tip-opening angle (CTOA) or displacement (CTOD) at a specified distance from the crack tip was shown to be most suited for modeling stable crack growth and instability during the fracture process. The results obtained in a number of studies show the necessity for studying different crack configurations when assessing the validity of any fracture criteria. One of the objectives of the present investigation is related to a critical evaluation of the CTOD growth criterion using an elastic-plastic finite element analysis under monotonic loading to failure. The analysis was found to predict three stages of crack growth behavior under monotonic loading to failure. Calculated CTOD values agreed well with experimental values for crack growth initiation.

  16. Do plastic particles affect microalgal photosynthesis and growth?

    PubMed

    Sjollema, Sascha B; Redondo-Hasselerharm, Paula; Leslie, Heather A; Kraak, Michiel H S; Vethaak, A Dick

    2016-01-01

    The unbridled increase in plastic pollution of the world's oceans raises concerns about potential effects these materials may have on microalgae, which are primary producers at the basis of the food chain and a major global source of oxygen. Our current understanding about the potential modes and mechanisms of toxic action that plastic particles exert on microalgae is extremely limited. How effects might vary with particle size and the physico-chemical properties of the specific plastic material in question are equally unelucidated, but may hold clues to how toxicity, if observed, is exerted. In this study we selected polystyrene particles, both negatively charged and uncharged, and three different sizes (0.05, 0.5 and 6μm) for testing the effects of size and material properties. Microalgae were exposed to different polystyrene particle sizes and surface charges for 72h. Effects on microalgal photosynthesis and growth were determined by pulse amplitude modulation fluorometry and flow cytometry, respectively. None of the treatments tested in these experiments had an effect on microalgal photosynthesis. Microalgal growth was negatively affected (up to 45%) by uncharged polystyrene particles, but only at high concentrations (250mg/L). Additionally, these adverse effects were demonstrated to increase with decreasing particle size. Copyright © 2015 Elsevier B.V. All rights reserved.

  17. Chronic Ankle Instability Does Not Affect Lower Extremity Functional Performance.

    PubMed

    Demeritt, Kerry M; Shultz, Sandra J; Docherty, Carrie L; Gansneder, Bruce M; Perrin, David H

    2002-12-01

    OBJECTIVE: To determine if functional performance is impaired in individuals with self-reported chronic ankle instability. DESIGN AND SETTING: We used a between-groups design to assess 3 functional variables. All data were collected at a Division III college and a military academy. Before testing, all subjects performed a 5-minute warm-up, followed by a series of stretches for the lower extremity muscles. Subjects then performed cocontraction, shuttle run, and agility hop tests in a counterbalanced fashion. Three trials for each functional test were completed and averaged for analysis. SUBJECTS: Twenty men with a history of at least 1 significant ankle sprain and episodes of at least 1 repeated ankle injury or feelings of instability or "giving way" were compared with 20 men with no prior history of ankle injury. Subjects were matched by age, height, weight, and activity level. MEASUREMENTS: Time to completion was measured in seconds for the cocontraction and the shuttle run tests. The agility hop test was measured on an error point scale. RESULTS: Using 3 separate, independent, 2-tailed t tests, we found no significant difference between groups for the cocontraction (P =.452), shuttle run (P =.680), or agility hop (P =.902) tests. CONCLUSIONS: Chronic ankle instability is a subjectively reported phenomenon defined as the tendency to "give way" during normal activity. Although athletes commonly complain of subjective symptoms associated with chronic ankle instability, our findings suggest that these symptoms do not negatively influence actual functional performance. Future researchers should evaluate other, more demanding functional-performance tests to further substantiate these findings.

  18. Role of Self-Organization of Dislocations in the Onset and Kinetics of Macroscopic Plastic Instability

    NASA Astrophysics Data System (ADS)

    Kobelev, Nikolay P.; Lebyodkin, Mikhail A.; Lebedkina, Tatiana A.

    2017-03-01

    The present paper examines two aspects of the problem of critical conditions of jerky flow in alloys, or the Portevin-Le Chatelier (PLC) effect. Recent development of dynamic strain aging (DSA) models proved their capacity to qualitatively reproduce complex non-monotonic behavior of the critical strain, providing that the parameters of theory are allowed to depend on strain. Experimental measurements of such strain dependences have been realized for the first time and used to revise the predictions of the critical strain and stress relaxation kinetics upon abrupt strain-rate changes. On the other hand, it is usually omitted from consideration that the PLC stress serrations can last very short time in comparison with the characteristic time of stress transients. The development of stress drops was studied with the aid of the acoustic emission (AE) technique. It is shown that such macroscopic instabilities are caused by clustering of AE events which otherwise occur all the time, including the periods of smooth plastic flow. The role of synchronization of dislocation avalanches in the development of abrupt stress serrations and its relationship with the predictions of the local DSA models is discussed.

  19. Origin of intermittent plastic flow and instability of shear band sliding in bulk metallic glasses.

    PubMed

    Sun, B A; Pauly, S; Hu, J; Wang, W H; Kühn, U; Eckert, J

    2013-05-31

    Intermittent or serrated plastic flow is widely observed in the deformation of bulk metallic glasses (BMGs) or other disordered solids at low temperatures. However, the underlying physical process responsible for the phenomena is still poorly understood. Here, we give an interpretation of the serrated flow behavior in BMGs by relating the atomic-scale deformation with the macroscopic shear band behavior. Our theoretical analysis shows that serrated flow in fact arises from an intrinsic dynamic instability of the shear band sliding, which is determined by a critical stiffness parameter in stick-slip dynamics. Based on this, the transition from serrated to nonserrated flow with the strain rate or the temperature is well predicted and the effects of various extrinsic and intrinsic factors on shear band stability can be quantitatively analyzed in BMGs. Our results, which are verified by a series of compression tests on various BMGs, provide key ingredients to fundamentally understand serrated flow and may bridge the gap between the atomic-scale physics and the larger-scale shear band dynamics governing the deformation of BMGs.

  20. Influence of real gas effects on ablative Rayleigh-Taylor instability in plastic target

    SciTech Connect

    Fan Zhengfeng; Xue Chuang; Ye Wenhua; Zhu Shaoping; Wang Lifeng

    2011-06-15

    In this research, real gas effects on ablative Rayleigh-Taylor instability are investigated in a plastic target. The real gas effects are included by adopting the quotidian equation of state (QEOS) model. Theoretical solutions for both QEOS and ideal gas EOS are obtained and compared, based on a same set of ablation parameters. It is found that when real gas effects are considered, the density gradient becomes less steep than that of ideal gas assumption, even though this cannot be used directly to draw a stabilization conclusion for the real gas effects. Further analysis shows that when real gas effects are considered, lower {partial_derivative}p/{partial_derivative}T in the dense shell region has the effect of stabilization, whereas the dependence of the internal energy on the density, lower specific heat (at constant volume) in the dense shell region, and higher specific heat in the low-density ablation region contribute to stronger destabilization effects. Overall, when real gas effects are considered, the destabilization effects are dominant for long wavelength perturbations, and the growth rates become much higher than the results of ideal gas assumption. In our specific case, the maximum relative error reaches 18%.

  1. Using plastic instability to validate and test the strength law of a material under pressure

    NASA Astrophysics Data System (ADS)

    Bolis, Cyril; Counilh, Denis; Savale, Brice

    2015-09-01

    In dynamical experiments (pressures higher than 10 GPa, strain rate around 104-106 s-1), metals are classically described using an equation of state and a strength law which is usually set using data from compression or traction tests at low pressure (few MPa) and low strain rates (less than 103 s-1). In consequence, it needs to be extrapolated during dynamical experiments. Classical shock experiments do not allow a fine validation of the stress law due to the interaction with the equation of state. To achieve this aim, we propose to use a dedicated experiment. We started from the works of Barnes et al. (1974 and 1980) where plastic instabilities initiated by a sinusoidal perturbation at the surface of the metal develop with the pressure. We adapted this principle to a new shape of initial perturbation and realized several experiments. We will present the setup and its use on a simple material: gold. We will detail how the interpretation of the experiments, coupled with previous characterization experiments helps us to test the strength lax of this material at high pressure and high strain rate.

  2. Role of Self-Organization of Dislocations in the Onset and Kinetics of Macroscopic Plastic Instability

    NASA Astrophysics Data System (ADS)

    Kobelev, Nikolay P.; Lebyodkin, Mikhail A.; Lebedkina, Tatiana A.

    2017-01-01

    The present paper examines two aspects of the problem of critical conditions of jerky flow in alloys, or the Portevin-Le Chatelier (PLC) effect. Recent development of dynamic strain aging (DSA) models proved their capacity to qualitatively reproduce complex non-monotonic behavior of the critical strain, providing that the parameters of theory are allowed to depend on strain. Experimental measurements of such strain dependences have been realized for the first time and used to revise the predictions of the critical strain and stress relaxation kinetics upon abrupt strain-rate changes. On the other hand, it is usually omitted from consideration that the PLC stress serrations can last very short time in comparison with the characteristic time of stress transients. The development of stress drops was studied with the aid of the acoustic emission (AE) technique. It is shown that such macroscopic instabilities are caused by clustering of AE events which otherwise occur all the time, including the periods of smooth plastic flow. The role of synchronization of dislocation avalanches in the development of abrupt stress serrations and its relationship with the predictions of the local DSA models is discussed.

  3. Richtmyer-Meshkov instability for elastic-plastic solids in converging geometries

    NASA Astrophysics Data System (ADS)

    López Ortega, A.; Lombardini, M.; Barton, P. T.; Pullin, D. I.; Meiron, D. I.

    2015-03-01

    We present a detailed study of the interface instability that develops at the boundary between a shell of elastic-plastic material and a cylindrical core of confined gas during the inbound implosive motion generated by a shock-wave. The main instability in this configuration is the so-called Richtmyer-Meshkov instability that arises when the shock wave crosses the material interface. Secondary instabilities, such as Rayleigh-Taylor, due to the acceleration of the interface, and Kelvin-Helmholtz, due to slip between solid and fluid, arise as the motion progresses. The reflection of the shock wave at the axis and its second interaction with the material interface as the shock moves outbound, commonly known as re-shock, results in a second Richtmyer-Meshkov instability that potentially increases the growth rate of interface perturbations, resulting in the formation of a mixing zone typical of fluid-fluid configurations and the loss of the initial perturbation length scales. The study of this problem is of interest for achieving stable inertial confinement fusion reactions but its complexity and the material conditions produced by the implosion close to the axis prove to be challenging for both experimental and numerical approaches. In this paper, we attempt to circumvent some of the difficulties associated with a classical numerical treatment of this problem, such as element inversion in Lagrangian methods or failure to maintain the relationship between the determinant of the deformation tensor and the density in Eulerian approaches, and to provide a description of the different events that occur during the motion of the interface. For this purpose, a multi-material numerical solver for evolving in time the equations of motion for solid and fluid media in an Eulerian formalism has been implemented in a Cartesian grid. Equations of state are derived using thermodynamically consistent hyperelastic relations between internal energy and stresses. The resolution required

  4. Affective Instability in Daily Life Is Predicted by Resting Heart Rate Variability

    PubMed Central

    Kuppens, Peter; Van den Bergh, Omer; Tuerlinckx, Francis; Sütterlin, Stefan

    2013-01-01

    Previous research has shown that being affectively unstable is an indicator of several forms of psychological maladjustment. However, little is known about the mechanisms underlying affective instability. Our research aims to examine the possibility that being prone to extreme fluctuations in one’s feelings is related to maladaptive emotion regulation. We investigated this hypothesis by relating affective instability, assessed in daily life using the experience sampling method, to self-reported emotion regulation strategies and to parasympathetically mediated heart rate variability (HRV), a physiological indicator of emotion regulation capacity. Results showed that HRV was negatively related to instability of positive affect (as measured by mean square successive differences), indicating that individuals with lower parasympathetic tone are emotionally less stable, particularly for positive affect. PMID:24312315

  5. Ecological Momentary Assessment of Affective and Interpersonal Instability in Adolescent Non-Suicidal Self-Injury.

    PubMed

    Santangelo, Philip S; Koenig, Julian; Funke, Vera; Parzer, Peter; Resch, Franz; Ebner-Priemer, Ulrich W; Kaess, Michael

    2016-12-19

    Affective and interpersonal instability, both core features of Borderline Personality Disorder (BPD), have been suggested to underlie non-suicidal self-injury (NSSI). Ecological momentary assessment (EMA) is the method of choice when investigating dynamic processes. Previously no study addressed affective and interpersonal instability in daily life of adolescents engaging in NSSI. Female adolescents with NSSI (n = 26) and age- and sex-matched healthy controls (n = 20) carried e-diaries on 2 consecutive weekends and were prompted in hourly intervals to rate their momentary affective state and feelings of attachment towards their mother and best friend. The majority of participants in the NSSI group also fulfilled diagnostic criteria for BPD (73%). Squared successive differences were calculated to quantify instability. Adolescents with NSSI reported less positive affect, t (44) = 6.94, p < 0.01, lower levels of attachment to the mother, t (44) = 5.53, p < 0.01, and best friend, t (44) = 4.36, p < 0.01. Both affective, t (44) = -5.55, p < 0.01, and interpersonal instability, mother: t (44) = -4.10, p < 0.01; best friend: t (44) = -4.57, p < 0.01, were significantly greater in adolescents engaging in NSSI. In the NSSI group, the number of BPD criteria met was positively correlated with affective instability, r = 0.40, p < 0.05, and instability of attachment to the best friend, r = 0.42, p < 0.05, but not instability of attachment towards the mother, r = 0.06, p = 0.79. In line with previous work in adults, NSSI is associated with affective and interpersonal instability assessed by EMA in adolescents. Preliminary findings highlight the association of affective and interpersonal instability with diagnostic criteria for BPD. Clinical implications and avenues for further research are discussed.

  6. Magnetic Field Generation by the Nonlinear Rayleigh--Taylor Instability in Laser-Driven Planar Plastic Targets

    NASA Astrophysics Data System (ADS)

    Gao, L.; Igumenshchev, I. V.; Hu, S. X.; Stoeckl, C.; Froula, D. H.; Nilson, P. M.; Davies, J. R.; Betti, R.; Meyerhofer, D. D.; Haines, M. G.

    2012-10-01

    Magnetic field generation during the nonlinear phase of the Rayleigh--Taylor (RT) instability in an ablatively driven plasma using ultrafast laser-driven proton radiography has been measured. Thin plastic foils were irradiated with ˜4-kJ, 2.5-ns laser pulses focused to an intensity of ˜10^14 W/cm^2 on the OMEGA EP Laser System. Target modulations were seeded by laser nonuniformities and amplified during target acceleration by the RT instability. The experimental data show the hydrodynamic evolution of the target and MG-level magnetic fields generated in the broken foil. The experimental data are in good agreement with predictions from 2-D magnetohydrodynamic simulations. This work was supported by the U.S. Department of Energy Office of Inertial Confinement Fusion under Cooperative Agreement No. DE-FC52-08NA28302.

  7. (In)stability of quasi-static paths of some finite dimensional smooth or elastic-plastic systems

    NASA Astrophysics Data System (ADS)

    Martins, J. A. C.; Monteiro Marques, M. D. P.; Petrov, A.; Rebrova, N. V.; Sobolev, V. A.; Coelho, I.

    2005-01-01

    In this paper we discuss some mathematical issues related to the stability of quasistatic paths of finite dimensional mechanical systems that have a smooth or an elastic-plastic behavior. The concept of stability of quasi-static paths used here is essentially a continuity property relatively to the size of the initial perturbations (as in Lyapunov stability) and to the smallness of the rate of application of the external forces (which here plays the role of the small parameter in singular perturbation problems). A related concept of attractiveness is also proposed. Sufficient conditions for attractiveness or for instability of quasi-static paths of smooth systems are presented. The Ziegler column and other examples illustrate these situations. Mathematical formulations (plus existence and uniqueness results) for dynamic and quasi-static elastic-plastic problems with linear hardening are recalled. A stability result is proved for the quasi-static evolution of these systems.

  8. Motion and Muscle Activity Are Affected by Instability Location During a Squat Exercise.

    PubMed

    Nairn, Brian C; Sutherland, Chad A; Drake, Janessa D M

    2017-03-01

    Nairn, BC, Sutherland, CA, and Drake, JDM. Motion and muscle activity are affected by instability location during a squat exercise. J Strength Cond Res 31(3): 677-685, 2017-Squat exercise training using instability devices has become increasingly popular for a multitude of reasons. Many devices generate instability at the feet and provide a bottom-up perturbation; however, the effect of a top-down instability device during a squat remains unclear. To induce instability at the upper body, a water-filled cylinder called the Attitube was used. This study analyzed the effects of instability location (top-down, bottom-up, and no instability) during a squat exercise in terms of kinematics and muscle activation. Ten male participants were instrumented with 75 reflective markers to track kinematics of the ankle, knee, hip, trunk, and the Bar/Attitube, and electromyography was recorded from 12 muscles bilaterally. Squats were performed with an Olympic bar on a stable surface, an Olympic bar on a BOSU ball (BALL, bottom-up), and the Attitube on solid ground (TUBE, top-down). The TUBE showed up to 1.5 times reduction in erector spinae activation and up to 1.5 times less trunk flexion while being performed at a slower velocity. There was also higher abdominal activation in the TUBE, with up to 2.8 times greater oblique activation compared with the stable condition. The BALL increased ankle eversion and knee flexion with higher muscle activation in gastrocnemius, biceps femoris, and quadriceps. Overall, changing the location of instability during a squat changed the motion and muscle activation patterns of the trunk and lower extremities. This provides information for future research into rehabilitation, learning proper squat technique, and for specific training scenarios.

  9. Negative Affect Instability among Individuals with Comorbid Borderline Personality Disorder and Posttraumatic Stress Disorder

    PubMed Central

    Scheiderer, Emily M.; Wang, Ting; Tomko, Rachel L.; Wood, Phillip K.; Trull, Timothy J.

    2015-01-01

    Ecological momentary assessment (EMA; Stone & Shiffman, 1994) was utilized to examine affective instability (AI) in the daily lives of outpatients with borderline personality disorder (BPD; n=78) with and without posttraumatic stress disorder (PTSD). A psychiatric control group (n=50) composed of outpatients with major depressive disorder/dysthymia (MDD/DYS) was employed to compare across subgroups: BPD-only, BPD+PTSD, MDD/DYS-only, and MDD/DYS+PTSD. Compared to the BPD-only group, the BPD+PTSD group had significantly greater instability of fear and sadness, but did not significantly differ in instability of hostility or aggregate negative affect. This pattern of elevated instability of fear and sadness was not present—and, in fact, was reversed—in the MDD/DYS group. Results emphasize the importance of examining AI within the context of specific comorbidities and affect types. Treatment and research addressing AI in the context of BPD-PTSD comorbidity may benefit from a focus on fear and sadness as separate from hostility or general negative affect. PMID:26904388

  10. Do Polyethylene Plastic Covers Affect Smoke Emissions from Debris Piles?

    NASA Astrophysics Data System (ADS)

    Weise, D. R.; Jung, H.; Cocker, D.; Hosseini, E.; Li, Q.; Shrivastava, M.; McCorison, M.

    2010-12-01

    Shrubs and small diameter trees exist in the understories of many western forests. They are important from an ecological perspective; however, this vegetation also presents a potential hazard as “ladder fuels” or as a heat source to damage the overstory during prescribed burns. Cutting and piling of this material to burn under safe conditions is a common silvicultural practice. To improve ignition success of the piled debris, polyethylene plastic is often used to cover a portion of the pile. While burning of piled forest debris is an acceptable practice in southern California from an air quality perspective, inclusion of plastic in the piles changes these debris piles to rubbish piles which should not be burned. With support from the four National Forests in southern California, we conducted a laboratory experiment to determine if the presence of polyethylene plastic in a pile of burning wood changed the smoke emissions. Debris piles in southern California include wood and foliage from common forest trees such as sugar and ponderosa pines, white fir, incense cedar, and California black oak and shrubs such as ceanothus and manzanita in addition to forest floor material and dirt. Manzanita wood was used to represent the debris pile in order to control the effects of fuel bed composition. The mass of polyethylene plastic incorporated into the pile was 0, 0.25 and 2.5% of the wood mass—a range representative of field conditions. Measured emissions included NOx, CO, CO2, SO2, polycyclic and light hydrocarbons, carbonyls, particulate matter (5 to 560 nm), elemental and organic carbon. The presence of polyethylene did not alter the emissions composition from this experiment.

  11. Numerical simulations of the Richtmyer-Meshkov instability in solid-vacuum interfaces using calibrated plasticity laws.

    PubMed

    López Ortega, A; Lombardini, M; Pullin, D I; Meiron, D I

    2014-03-01

    The Richtmyer-Meshkov instability of interfaces separating elastic-plastic materials from vacuum (heavy-light configuration) is studied by means of computational techniques. A fully Eulerian multimaterial algorithm that solves consistently the Euler equations and the time evolution of the deformations in the material is applied to three distinct materials (copper, aluminum, and stainless steel). If a perfectly plastic constitutive relation is considered, an empirical law is computed that relates the long-term perturbation amplitude of the interface, its maximum growth rate, the initial density, and the yield stress of the material. It is shown that this linear relation can be extended to materials that follow more complex plastic behavior which can account for rate dependency, hardening, and thermal softening, and to situations in which small-perturbation theory is no longer valid. In effect, the yield stress computed from measurements of the long-term amplitude and maximum growth rate closely matches the von Mises stress found at the interface of solid materials for a wide range of cases with different initial parameters.

  12. The use of COD and plastic instability in crack propagation and arrest in shells

    NASA Technical Reports Server (NTRS)

    Erdogan, F.; Ratwani, M.

    1974-01-01

    The initiation, growth, and possible arrest of fracture in cylindrical shells containing initial defects are dealt with. For those defects which may be approximated by a part-through semi-elliptic surface crack which is sufficiently shallow so that part of the net ligament in the plane of the crack is still elastic, the existing flat plate solution is modified to take into account the shell curvature effect as well as the effect of the thickness and the small scale plastic deformations. The problem of large defects is then considered under the assumptions that the defect may be approximated by a relatively deep meridional part-through surface crack and the net ligament through the shell wall is fully yielded. The results given are based on an 8th order bending theory of shallow shells using a conventional plastic strip model to account for the plastic deformations around the crack border.

  13. The role of affective instability and impulsivity in predicting future BPD features.

    PubMed

    Tragesser, Sarah L; Solhan, Marika; Schwartz-Mette, Rebecca; Trull, Timothy J

    2007-12-01

    Models of borderline personality disorder (BPD) suggest that extreme levels of affective instability/emotional dysregulation, impulsivity, or the combination of these two traits account for the symptoms characteristic of BPD. The present study utilized longitudinal data to evaluate the ability of Personality Assessment Inventory-Borderline Features (PAI-BOR; Morey, 1991) subscale scores to predict BPD features two years later as a test of these models of BPD. Participants were 156 male and 194 female young adults who completed the PAI-BOR at age 18 and again two years later. Three models were compared: (a) Wave 1 affective instability scores predicting Wave 2 BPD features (AI model); (b) Wave 1 self-harm/impulsivity scores predicting Wave 2 BPD features (IMP model); and (c) both Wave 1 affective instability and self-harm/impulsivity scores predicting Wave 2 BPD features (AI-IMP model), all controlling for stabilities and within-time covariances. Results indicated that the AI model provided the best fit to the data, and improved model fit over a baseline stabilities model and the other models tested. These results are consistent with Linehan's theory (1993) that emotional dysregulation drives the other BPD symptoms.

  14. The transmission of light affect the color reproduction of plastic print

    NASA Astrophysics Data System (ADS)

    Chen, Jie; Zhang, Yi-xin; Shi, Gongcheng

    2011-01-01

    By analyzing the different paths that the incident light traverses in the printing, the paper aims to study the effect the transmission of light produces on the color reproduction of the plastic printing. The article also analyzes object characteristics about the three color properties and the color density, so as to make an accurate prediction on the color reproduction of the printing where ink is printed on the end of the plastic base directly. In the research, the incident light on the plastic print are divided into two parts: the reflection of diffuse light in the ink and the optical multi-layer internal reflection of the light through ink layer onto the plastic substrate. In this paper, we use kubelka-munk theory to analyze the transmission of the incident light on the surface of the printing product and Clapper-Yule theory to analyze the incident light which through the ink to the plastic film surface. When the incident light through the ink to the film surface, we have a series of mutually parallel reflected beam and refracted beam, and then obtain the synthesis of the reflected light complex amplitude, using the similar methods to obtain the total reflected and refraction light intensity. Combining the total reflection light intensity through the plastic substrate and the overall reflectivity through a plastic print surface by the kubelka-munk theory, color density and light transmission factor of the plastic substrate can be drawn in the formula: D ∞ f (δ,d,i1 ). From the above equation, we can find that optical phase retardation δ, the thickness of plastic d and the angle of incidence on the plastic surface i1 affect the color reproduction of plastic print.

  15. Statistical Properties of Real-Time Amplitude Estimate of Harmonics Affected by Frequency Instability

    NASA Astrophysics Data System (ADS)

    Bellan, Diego; Pignari, Sergio A.

    2016-07-01

    This work deals with the statistical characterization of real-time digital measurement of the amplitude of harmonics affected by frequency instability. In fact, in modern power systems both the presence of harmonics and frequency instability are well-known and widespread phenomena mainly due to nonlinear loads and distributed generation, respectively. As a result, real-time monitoring of voltage/current frequency spectra is of paramount importance as far as power quality issues are addressed. Within this framework, a key point is that in many cases real-time continuous monitoring prevents the application of sophisticated algorithms to extract all the information from the digitized waveforms because of the required computational burden. In those cases only simple evaluations such as peak search of discrete Fourier transform are implemented. It is well known, however, that a slight change in waveform frequency results in lack of sampling synchronism and uncertainty in amplitude estimate. Of course the impact of this phenomenon increases with the order of the harmonic to be measured. In this paper an approximate analytical approach is proposed in order to describe the statistical properties of the measured magnitude of harmonics affected by frequency instability. By providing a simplified description of the frequency behavior of the windows used against spectral leakage, analytical expressions for mean value, variance, cumulative distribution function, and probability density function of the measured harmonics magnitude are derived in closed form as functions of waveform frequency treated as a random variable.

  16. Will phenotypic plasticity affecting flowering phenology keep pace with climate change?

    PubMed

    Richardson, Bryce A; Chaney, Lindsay; Shaw, Nancy L; Still, Shannon M

    2016-10-14

    Rising temperatures have begun to shift flowering time, but it is unclear whether phenotypic plasticity can accommodate projected temperature change for this century. Evaluating clines in phenological traits and the extent and variation in plasticity can provide key information on assessing risk of maladaptation and developing strategies to mitigate climate change. In this study, flower phenology was examined in 52 populations of big sagebrush (Artemisia tridentata) growing in three common gardens. Flowering date (anthesis) varied 91 days from late July to late November among gardens. Mixed-effects modeling explained 79% of variation in flowering date, of which 46% could be assigned to plasticity and genetic variation in plasticity and 33% to genetics (conditional R(2) = 0.79, marginal R(2) = 0.33). Two environmental variables that explained the genetic variation were photoperiod and the onset of spring, the Julian date of accumulating degree days > 5°C reaching 100. The genetic variation was mapped for contemporary and future climates (decades 2060 and 2090), showing flower date change varies considerably across the landscape. Plasticity was estimated to accommodate, on average, a +/- 13-day change in flowering date. However, the examination of genetic variation in plasticity suggests that the magnitude of plasticity could be affected by variation in the sensitivity to photoperiod and temperature. In a warmer common garden, lower latitude populations have greater plasticity (+16 days) compared to higher latitude populations (+10 days). Mapped climatypes of flowering date for contemporary and future climates illustrate the wide breadth of plasticity and large geographic overlap. Our research highlights the importance of integrating information on genetic variation, phenotypic plasticity and climatic niche modeling to evaluate plant responses and elucidate vulnerabilities to climate change. This article is protected by copyright. All rights reserved.

  17. CB1 receptor affects cortical plasticity and response to physiotherapy in multiple sclerosis

    PubMed Central

    Mori, Francesco; Ljoka, Concetta; Nicoletti, Carolina G.; Kusayanagi, Hajime; Buttari, Fabio; Giordani, Laura; Rossi, Silvia; Foti, Calogero

    2014-01-01

    Objectives: Therapeutic effects of physical therapy in neurologic disorders mostly rely on the promotion of use-dependent synaptic plasticity in damaged neuronal circuits. Genetic differences affecting the efficiency of synaptic plasticity mechanisms could explain why some patients do not respond adequately to the treatment. It is known that physical exercise activates the endocannabinoid system and that stimulation of cannabinoid CB1 receptors (CB1Rs) promotes synaptic plasticity in both rodents and humans. We thus tested whether CB1R genetic variants affect responsiveness to exercise therapy. Methods: We evaluated the effect of a genetic variant of the CB1R associated with reduced receptor expression (patients with long AAT trinucleotide short tandem repeats in the CNR1 gene) on long-term potentiation (LTP)–like cortical plasticity induced by transcranial magnetic theta burst stimulation (TBS) of the motor cortex and, in parallel, on clinical response to exercise therapy in patients with multiple sclerosis. Results: We found that patients with long AAT CNR1 repeats do not express TBS-induced LTP-like cortical plasticity and show poor clinical benefit after exercise therapy. Conclusions: Our results provide the first evidence that genetic differences within the CB1R may influence clinical responses to exercise therapy, and they strengthen the hypothesis that CB1Rs are involved in the regulation of synaptic plasticity and in the control of spasticity in humans. This information might be of great relevance for patient stratification and personalized rehabilitation treatment programs. PMID:25520956

  18. The instability of viscous self-gravitating protostellar disk affected by density bump

    NASA Astrophysics Data System (ADS)

    Elyasi, Mahjubeh; Nejad-Asghar, Mohsen

    2017-09-01

    In this work, we study the instability of viscous self-gravitating protostellar disk affected by infalling Low-mass condensations (LMCs) from the envelope of collapsing molecular cloud cores. The infalling low-mass-condensations (LMCs) are considered as density bumps through the nearly Keplerian viscous accretion disk, and their evolutions are analyzed by using the linear perturbation approximation. We investigate occurrence of instability in the evolution of these density bumps. We find the unstable regions of the bumped accretion disk and evaluate the growth time scale (GTS) of the instability. We also study the radial accretion and azimuthal rotation in these unstable regions. The results show that the GTS will be minimum at a special radius so that the unstable regions can be divided in two parts (inner and outer regions). The perturbed radial and azimuthal velocities in the inner unstable regions are strengthened, while in the outer unstable regions are weakened. Decreasing the radial and azimuthal velocities in the outer unstable regions may lead to coagulation of matters. This effect can help the fragmentation of the disk and formation of the self-gravitating bound objects.

  19. Increased plastic litter cover affects the foraging activity of the sandy intertidal gastropod Nassarius pullus.

    PubMed

    Aloy, Alexander B; Vallejo, Benjamin M; Juinio-Meñez, Marie Antonette

    2011-08-01

    This study analyzed the foraging behavior of the gastropod Nassarius pullus on garbage-impacted sandy shores of Talim Bay, Batangas, Philippines. The effect of different levels of plastic garbage cover on foraging efficiency was investigated. Controlled in situ baiting experiments were conducted to quantify aspects of foraging behavior as affected by the levels of plastic litter cover in the foraging area. The results of the study indicated that the gastropod's efficiency in locating and in moving towards a food item generally decreased as the level of plastic cover increased. Prolonged food searching time and increased self-burial in sand were highly correlated with increased plastic cover. The accuracy of orientation towards the actual position of the bait decreased significantly when the amount of plastic cover increased to 50%. These results are consistent with the significant decreases in the abundance of the gastropod observed during periods of deposition of large amounts of plastic and other debris on the shore. Copyright © 2011 Elsevier Ltd. All rights reserved.

  20. A Mixed Model to Disentangle Variance and Serial Autocorrelation in Affective Instability Using Ecological Momentary Assessment Data.

    PubMed

    Vansteelandt, Kristof; Verbeke, Geert

    2016-01-01

    Affective instability, the tendency to experience emotions that fluctuate frequently and intensively over time, is a core feature of several mental disorders including borderline personality disorder. Currently, affect is often measured with Ecological Momentary Assessment protocols, which yield the possibility to quantify the instability of affect over time. A number of linear mixed models are proposed to examine (diagnostic) group differences in affective instability. The models contribute to the existing literature by estimating simultaneously both the variance and serial dependency component of affective instability when observations are unequally spaced in time with the serial autocorrelation (or emotional inertia) declining as a function of the time interval between observations. In addition, the models can eliminate systematic trends, take between subject differences into account and test for (diagnostic) group differences in serial autocorrelation, short-term as well as long-term affective variability. The usefulness of the models is illustrated in a study on diagnostic group differences in affective instability in the domain of eating disorders. Limitations of the model are that they pertain to group (and not individual) differences and do not focus explicitly on circadian rhythms or cycles in affect.

  1. Tensile elastic properties of 18:8 chromium-nickel steel as affected by plastic deformation

    NASA Technical Reports Server (NTRS)

    Mcadam, D J; Mebs, R W

    1939-01-01

    The relationship between stress and strain, and between stress and permanent set, for 18:8 alloy as affected by prior plastic deformation is discussed. Hysteresis and creep and their effects on the stress-strain and stress-set curves are also considered, as well as the influence of duration of the rest interval after cold work and the influence of plastic deformation on proof stresses, on the modulus of elasticity at zero stress, and on the curvature of the stress-strain line. A constant (c sub 1) is suggested to represent the variation of the modulus of elasticity with stress.

  2. The role of microRNAs in synaptic plasticity, major affective disorders and suicidal behavior.

    PubMed

    Serafini, Gianluca; Pompili, Maurizio; Innamorati, Marco; Giordano, Gloria; Montebovi, Franco; Sher, Leo; Dwivedi, Yogesh; Girardi, Paolo

    2012-07-01

    Major affective disorders are common widespread conditions associated with multiple psychosocial impairments and suicidal risk in the general population. At least 3-4% of all depressive individuals die by suicide. At a molecular level, affective disorders and suicidal behavior are recently associated with disturbances in structural and synaptic plasticity. A recent hypothesis suggested that small non-coding RNAs (ncRNAs), in particular microRNAs (miRNAs), play a critical role in the translational regulation at the synapse. We performed a selective overview of the current literature on miRNAs putative subcellular localization and sites of action in mature neurons analyzing their role in neurogenesis, synaptic plasticity, pathological stress changes, major affective disorders and suicidal behavior. miRNAs have played a fundamental role in the evolution of brain functions. The perturbation of some intracellular mechanisms as well as impaired assembly, localization, and translational regulation of specific RNA binding proteins may affect learning and memory, presumably contributing to the pathogenesis of major affective disorders and perhaps suicidal behavior. Also, miRNA dys-regulation has also been linked to several neuropsychiatric diseases. However, further evidence are needed in order to directly clarify the role of miRNAs in major affective disorders and suicidal behavior.

  3. Affective instability as rapid cycling: theoretical and clinical implications for borderline personality and bipolar spectrum disorders.

    PubMed

    Mackinnon, Dean F; Pies, Ronald

    2006-02-01

    The Diagnostic and Statistical Manual of Mental Disorders guidelines provide only a partial solution to the nosology and treatment of bipolar disorder in that disorders with common symptoms and biological correlates may be categorized separately because of superficial differences related to behavior, life history, and temperament. The relationship is explored between extremely rapid switching forms of bipolar disorder, in which manic and depressive symptoms are either mixed or switch rapidly, and forms of borderline personality disorder in which affective lability is a prominent symptom. A MedLine search was conducted of articles that focused on rapid cycling in bipolar disorder, emphasizing recent publications (2001-2004). Studies examined here suggest a number of points of phenomenological and biological overlap between the affective lability criterion of borderline personality disorder and the extremely rapid cycling bipolar disorders. We propose a model for the development of 'borderline' behaviors on the basis of unstable mood states that sheds light on how the psychological and somatic interventions may be aimed at 'breaking the cycle' of borderline personality disorder development. A review of pharmacologic studies suggests that anticonvulsants may have similar stabilizing effects in both borderline personality disorder and rapid cycling bipolar disorder. The same mechanism may drive both the rapid mood switching in some forms of bipolar disorder and the affective instability of borderline personality disorder and may even be rooted in the same genetic etiology. While continued clinical investigation of the use of anticonvulsants in borderline personality disorder is needed, anticonvulsants may be useful in the treatment of this condition, combined with appropriate psychotherapy.

  4. Analysis of Affective Instability in Ecological Momentary Assessment: Indices Using Successive Difference and Group Comparison via Multilevel Modeling

    ERIC Educational Resources Information Center

    Jahng, Seungmin; Wood, Phillip K.; Trull, Timothy J.

    2008-01-01

    Temporal instability of affect is a defining characteristic of psychological disorders such as borderline personality disorder (BPD) and mood cycling disorders. Ecological momentary assessment (EMA) enables researchers to directly assess such frequent and extreme fluctuations over time. The authors examined 4 operationalizations of such temporal…

  5. Analysis of Affective Instability in Ecological Momentary Assessment: Indices Using Successive Difference and Group Comparison via Multilevel Modeling

    ERIC Educational Resources Information Center

    Jahng, Seungmin; Wood, Phillip K.; Trull, Timothy J.

    2008-01-01

    Temporal instability of affect is a defining characteristic of psychological disorders such as borderline personality disorder (BPD) and mood cycling disorders. Ecological momentary assessment (EMA) enables researchers to directly assess such frequent and extreme fluctuations over time. The authors examined 4 operationalizations of such temporal…

  6. Structural plasticity of the social brain: Differential change after socio-affective and cognitive mental training.

    PubMed

    Valk, Sofie L; Bernhardt, Boris C; Trautwein, Fynn-Mathis; Böckler, Anne; Kanske, Philipp; Guizard, Nicolas; Collins, D Louis; Singer, Tania

    2017-10-01

    Although neuroscientific research has revealed experience-dependent brain changes across the life span in sensory, motor, and cognitive domains, plasticity relating to social capacities remains largely unknown. To investigate whether the targeted mental training of different cognitive and social skills can induce specific changes in brain morphology, we collected longitudinal magnetic resonance imaging (MRI) data throughout a 9-month mental training intervention from a large sample of adults between 20 and 55 years of age. By means of various daily mental exercises and weekly instructed group sessions, training protocols specifically addressed three functional domains: (i) mindfulness-based attention and interoception, (ii) socio-affective skills (compassion, dealing with difficult emotions, and prosocial motivation), and (iii) socio-cognitive skills (cognitive perspective-taking on self and others and metacognition). MRI-based cortical thickness analyses, contrasting the different training modules against each other, indicated spatially diverging changes in cortical morphology. Training of present-moment focused attention mostly led to increases in cortical thickness in prefrontal regions, socio-affective training induced plasticity in frontoinsular regions, and socio-cognitive training included change in inferior frontal and lateral temporal cortices. Module-specific structural brain changes correlated with training-induced behavioral improvements in the same individuals in domain-specific measures of attention, compassion, and cognitive perspective-taking, respectively, and overlapped with task-relevant functional networks. Our longitudinal findings indicate structural plasticity in well-known socio-affective and socio-cognitive brain networks in healthy adults based on targeted short daily mental practices. These findings could promote the development of evidence-based mental training interventions in clinical, educational, and corporate settings aimed at

  7. How does the Vertical Profile of Baroclinicity Affect the Wave Instability?

    NASA Astrophysics Data System (ADS)

    Iwasaki, T.; Kodama, C.

    2011-12-01

    The global warming is expected to decrease the baroclinicity in the lower troposphere but increase it in the upper troposphere. It is unknown how the vertical profile of baroclinicity affects the wave instability. In order to study this problem, the growth rate of instability waves is generalized to consider the realistic atmosphere on the basis of wave-mean flow interactions in the mass-weighted isentropic zonal mean (MIM). Energy conversion diagram in MIM becomes a cascade type, which is different from the four box scheme in the conventional Eurelian mean framework. The wave energy W is converted from the zonal mean kinetic energy Kz and the integrated conversion rate is proportional to the mean zonal flow difference between the Eliassen-Palm (E-P) flux convergence and divergence areas. The space-mean growth rate is defined as the half of energy conversion rate divided by the wave energy 0.5/. In the Eady waves, the generalized growth rate becomes identical to the conventional one. Sensitivity of growth rate to the UT-LS baroclinicity was studied using an aqua-planet simulation. The UT-LS baroclinicity is enhanced (reduced) in winter (summer) hemisphere, when the solar condition is modified with the SST unchanged. Wave energy and energy conversions integrated over hemispheres are increased (decreased) in the winter (summer) hemisphere from the spring/fall hemisphere. Peak positions of wave energy and its generation rate shift poleward (equatorward) in winter (summer). Generalized growth rate is increased (decreased) in the winter (summer) hemisphere. The UT-LS baroclinicity is considered to enhance growth rates of existing waves and accordingly increases wave energy as well as the low-level baroclinicity does.The growth rate is diagnosed of aqua-planet simulation under equinox/solstice solar conditions with equinox SST. The result suggests that the growth rate may be sensitive to baroclinicity in the upper troposphere as well as that in the

  8. Pushing the Limits: Cognitive, Affective, and Neural Plasticity Revealed by an Intensive Multifaceted Intervention

    PubMed Central

    Mrazek, Michael D.; Mooneyham, Benjamin W.; Mrazek, Kaita L.; Schooler, Jonathan W.

    2016-01-01

    Scientific understanding of how much the adult brain can be shaped by experience requires examination of how multiple influences combine to elicit cognitive, affective, and neural plasticity. Using an intensive multifaceted intervention, we discovered that substantial and enduring improvements can occur in parallel across multiple cognitive and neuroimaging measures in healthy young adults. The intervention elicited substantial improvements in physical health, working memory, standardized test performance, mood, self-esteem, self-efficacy, mindfulness, and life satisfaction. Improvements in mindfulness were associated with increased degree centrality of the insula, greater functional connectivity between insula and somatosensory cortex, and reduced functional connectivity between posterior cingulate cortex (PCC) and somatosensory cortex. Improvements in working memory and reading comprehension were associated with increased degree centrality of a region within the middle temporal gyrus (MTG) that was extensively and predominately integrated with the executive control network. The scope and magnitude of the observed improvements represent the most extensive demonstration to date of the considerable human capacity for change. These findings point to higher limits for rapid and concurrent cognitive, affective, and neural plasticity than is widely assumed. PMID:27047361

  9. [Risk factors affecting fusion in the treatment of lumbar spine instability].

    PubMed

    Jiménez-Avila, J M; García-Valencia, J; Bitar-Alatorre, W E

    2011-01-01

    Risk factors are the endogenous or exogenous factors that may be controlled and they are responsible for disease. The objective of this paper is to describe the risk factors affecting vertebral fusion in patients with lumbar spine instability seen at our hospital and to see how they relate to nutritional factors. Patients undergoing vertebral fusion due to several diagnoses were analyzed. Different parameters were captured to determine the interaction among them and assess the factors affecting vertebral fusion healing. They were compared with patients with pseudoarthrosis to determine its risk factors. Patients were divided into two groups: the control group, who underwent fusion, and the cases, who had pseudoarthrosis. A total of 59 patients were examined; 15 (25.4%) were cases (pseudoarthrosis) and 44 (74.6%) were controls (fusion). The demographic distribution was 27 (45.8%) females and 32 (54.2%) males; mean age was 51 +/- 12 years, with a minimum age of 20 and a maximum of 85. The diagnostic-based distribution was as follows: 29 (49.1%) spondylolistheses, 21 (35.6%) fractures, 5 (8.5%) herniated discs, 3 (5.1%) infections, and one (1.7%) tumor. Mean body weight was 75.9 kg, height was 160 cm, BMI 24.5, Hb 15.2, Hct 35.9, and Alb 3.5. Various risk factors were analyzed including the following: age over 60 years, which showed a 49% higher chance of pseudoarthrosis compared with the control group, with a 95% CI, 0.12-2.27; body weight over 90 kg, which showed an 82% higher chance of pseudoarthrosis compared with the fusion group, with a 95% CI, 0.03-0.43; BMI, which showed a 25% higher chance of pseudoarthrosis, with a 95% CI, 0.18-3.18; hypoalbuminemia < 3.4 mg/100 ml, which showed a 78% higher chance of pseudoarthrosis, with a 95% CI, 0.06-0.75. This study found that pseudoarthrosis is caused by risk factors linked to the nutritional profile, i.e., obesity, and hypoalbuminemia; its chance of occurring is 1.5 greater than in individuals with normal values. For

  10. ERK Pathway Activation Bidirectionally Affects Visual Recognition Memory and Synaptic Plasticity in the Perirhinal Cortex

    PubMed Central

    Silingardi, Davide; Angelucci, Andrea; De Pasquale, Roberto; Borsotti, Marco; Squitieri, Giovanni; Brambilla, Riccardo; Putignano, Elena; Pizzorusso, Tommaso; Berardi, Nicoletta

    2011-01-01

    ERK 1,2 pathway mediates experience-dependent gene transcription in neurons and several studies have identified its pivotal role in experience-dependent synaptic plasticity and in forms of long term memory involving hippocampus, amygdala, or striatum. The perirhinal cortex (PRHC) plays an essential role in familiarity-based object recognition memory. It is still unknown whether ERK activation in PRHC is necessary for recognition memory consolidation. Most important, it is unknown whether by modulating the gain of the ERK pathway it is possible to bidirectionally affect visual recognition memory and PRHC synaptic plasticity. We have first pharmacologically blocked ERK activation in the PRHC of adult mice and found that this was sufficient to impair long term recognition memory in a familiarity-based task, the object recognition task (ORT). We have then tested performance in the ORT in Ras-GRF1 knock-out (KO) mice, which exhibit a reduced activation of ERK by neuronal activity, and in ERK1 KO mice, which have an increased activation of ERK2 and exhibit enhanced striatal plasticity and striatal mediated memory. We found that Ras-GRF1 KO mice have normal short term memory but display a long term memory deficit; memory reconsolidation is also impaired. On the contrary, ERK1 KO mice exhibit a better performance than WT mice at 72 h retention interval, suggesting a longer lasting recognition memory. In parallel with behavioral data, LTD was strongly reduced and LTP was significantly smaller in PRHC slices from Ras-GRF1 KO than in WT mice while enhanced LTP and LTD were found in PRHC slices from ERK1 KO mice. PMID:22232579

  11. Thermal plasticity in young snakes: how will climate change affect the thermoregulatory tactics of ectotherms?

    PubMed

    Aubret, F; Shine, R

    2010-01-15

    Climate change will result in some areas becoming warmer and others cooler, and will amplify the magnitude of year-to-year thermal variation in many areas. How will such changes affect animals that rely on ambient thermal heterogeneity to behaviourally regulate their body temperatures? To explore this question, we raised 43 captive-born tiger snakes Notechis scutatus in enclosures that provided cold (19-22 degrees C), intermediate (19-26 degrees C) or hot (19-37 degrees C) thermal gradients. The snakes adjusted their diel timing of thermoregulatory behaviour so effectively that when tested 14 months later, body temperatures (mean and maximum), locomotor speeds and anti-predator behaviours did not differ among treatment groups. Thus, the young snakes modified their behaviour to compensate for restricted thermal opportunities. Then, we suddenly shifted ambient conditions to mimic year-to-year variation. In contrast to the earlier plasticity, snakes failed to adjust to this change, e.g. snakes raised at cooler treatments but then shifted to hot conditions showed a higher mean body temperature for at least two months after the onset of the new thermal regime. Hence, thermal conditions experienced early in life influenced subsequent thermoregulatory tactics; the mean selected temperature of a snake depended more upon its prior raising conditions than upon its current thermoregulatory opportunities. Behavioural plasticity thus allows snakes to adjust to suboptimal thermal conditions but this plasticity is limited. The major thermoregulatory challenge from global climate change may not be the shift in mean values (to which our young snakes adjusted) but the increased year-to-year variation (with which our snakes proved less able to deal).

  12. The Role of GluK4 in Synaptic Plasticity and Affective Behavior in Mice

    NASA Astrophysics Data System (ADS)

    Catches, Justin Samuel

    Kainate receptors (KARs) are glutamate-gated ion channels that signal through both ionotropic and metabotropic pathways (Contractor et al., 2011). Combinations of five KAR subunits (GluK1-5) form tetrameric receptors with GluK1, GluK2, and GluK3 able to form functional homomeric channels. The high-affinity subunits, GluK4 and GluK5, do not form homomeric channels but modify the properties of heteromeric receptors. Expression of the GluK4 receptor subunit in the forebrain is restricted to the CA3 region of the hippocampus and dentate gyrus regions where KARs modulate synaptic plasticity. In this study, ablation of Grik4, which encodes GluK4, in mice reduced KAR synaptic currents and altered activation properties of postsynaptic receptors but left two forms of presynaptic short-term plasticity intact. Disruption of both Grik4 and Grik5 caused complete loss of the postsynaptic ionotropic KAR current and impaired presynaptic frequency facilitation. Additionally, KAR surface expression was altered at pre- and postsynaptic sites at the MF synapse. Despite the loss of ionotropic signaling, KAR-mediated inhibition of the slow afterhyperpolarization current, which is dependent on metabotropic signaling, was intact in CA3 neurons. Long-term potentiation at the MF-CA3 synapse was reduced, likely through a loss of KAR modulation of excitability of the presynaptic MF axons. Genetic variants in the human GRIK4 gene alter the susceptibility for affective disorders (Bloss and Hunter, 2010). We found that ablation of Grik4 in mice resulted in reduced anxiety and an antidepressant-like phenotype. In the elevated zero-maze, a test for anxiety and risk taking behavior, and in two anxiogenic tests, marble-burying and novelty-induced suppression of feeding, anxiety-like behavior was consistently reduced in knockout animals. In the forced swim, a test of learned helplessness used to determine depression-like behavior, knockout mice demonstrated significantly less immobility suggesting

  13. Is sleep essential for neural plasticity in humans, and how does it affect motor and cognitive recovery?

    PubMed

    Gorgoni, Maurizio; D'Atri, Aurora; Lauri, Giulia; Rossini, Paolo Maria; Ferlazzo, Fabio; De Gennaro, Luigi

    2013-01-01

    There is a general consensus that sleep is strictly linked to memory, learning, and, in general, to the mechanisms of neural plasticity, and that this link may directly affect recovery processes. In fact, a coherent pattern of empirical findings points to beneficial effect of sleep on learning and plastic processes, and changes in synaptic plasticity during wakefulness induce coherent modifications in EEG slow wave cortical topography during subsequent sleep. However, the specific nature of the relation between sleep and synaptic plasticity is not clear yet. We reported findings in line with two models conflicting with respect to the underlying mechanisms, that is, the "synaptic homeostasis hypothesis" and the "consolidation" hypothesis, and some recent results that may reconcile them. Independently from the specific mechanisms involved, sleep loss is associated with detrimental effects on plastic processes at a molecular and electrophysiological level. Finally, we reviewed growing evidence supporting the notion that plasticity-dependent recovery could be improved managing sleep quality, while monitoring EEG during sleep may help to explain how specific rehabilitative paradigms work. We conclude that a better understanding of the sleep-plasticity link could be crucial from a rehabilitative point of view.

  14. Is Sleep Essential for Neural Plasticity in Humans, and How Does It Affect Motor and Cognitive Recovery?

    PubMed Central

    2013-01-01

    There is a general consensus that sleep is strictly linked to memory, learning, and, in general, to the mechanisms of neural plasticity, and that this link may directly affect recovery processes. In fact, a coherent pattern of empirical findings points to beneficial effect of sleep on learning and plastic processes, and changes in synaptic plasticity during wakefulness induce coherent modifications in EEG slow wave cortical topography during subsequent sleep. However, the specific nature of the relation between sleep and synaptic plasticity is not clear yet. We reported findings in line with two models conflicting with respect to the underlying mechanisms, that is, the “synaptic homeostasis hypothesis” and the “consolidation” hypothesis, and some recent results that may reconcile them. Independently from the specific mechanisms involved, sleep loss is associated with detrimental effects on plastic processes at a molecular and electrophysiological level. Finally, we reviewed growing evidence supporting the notion that plasticity-dependent recovery could be improved managing sleep quality, while monitoring EEG during sleep may help to explain how specific rehabilitative paradigms work. We conclude that a better understanding of the sleep-plasticity link could be crucial from a rehabilitative point of view. PMID:23840970

  15. Chromosomal instability affects the tumorigenicity of glioblastoma tumor-initiating cells

    PubMed Central

    Godek, Kristina M.; Venere, Monica; Wu, Quilian; Mills, Kevin D.; Hickey, William F.; Rich, Jeremy N.; Compton, Duane A.

    2016-01-01

    Tumors are dynamic organs that evolve during disease progression with genetic, epigenetic, and environmental differences among tumor cells serving as the foundation for selection and evolution in tumors. Tumor-initiating cells (TICs) that are responsible for tumorigenesis are a source of functional cellular heterogeneity while chromosomal instability (CIN) is a source of karyotypic genetic diversity. However, the extent that CIN contributes to TIC genetic diversity and its relationship to TIC function remains unclear. Here we demonstrate that glioblastoma TICs display chromosomal instability with lagging chromosomes at anaphase and extensive non-clonal chromosome copy number variations. Elevating the basal chromosome mis-segregation rate in TICs both decreases proliferation and the stem-like phenotype of TICs in vitro. Consequently tumor formation is abolished in an orthotopic mouse model. These results demonstrate that TICs generate genetic heterogeneity within tumors but that TIC function is impaired if the rate of genetic change is elevated above a tolerable threshold. PMID:27001151

  16. Meal size and frequency affect neuronal plasticity and vulnerability to disease: cellular and molecular mechanisms.

    PubMed

    Mattson, Mark P; Duan, Wenzhen; Guo, Zhihong

    2003-02-01

    Although all cells in the body require energy to survive and function properly, excessive calorie intake over long time periods can compromise cell function and promote disorders such as cardiovascular disease, type-2 diabetes and cancers. Accordingly, dietary restriction (DR; either caloric restriction or intermittent fasting, with maintained vitamin and mineral intake) can extend lifespan and can increase disease resistance. Recent studies have shown that DR can have profound effects on brain function and vulnerability to injury and disease. DR can protect neurons against degeneration in animal models of Alzheimer's, Parkinson's and Huntington's diseases and stroke. Moreover, DR can stimulate the production of new neurons from stem cells (neurogenesis) and can enhance synaptic plasticity, which may increase the ability of the brain to resist aging and restore function following injury. Interestingly, increasing the time interval between meals can have beneficial effects on the brain and overall health of mice that are independent of cumulative calorie intake. The beneficial effects of DR, particularly those of intermittent fasting, appear to be the result of a cellular stress response that stimulates the production of proteins that enhance neuronal plasticity and resistance to oxidative and metabolic insults; they include neurotrophic factors such as brain-derived neurotrophic factor (BDNF), protein chaperones such as heat-shock proteins, and mitochondrial uncoupling proteins. Some beneficial effects of DR can be achieved by administering hormones that suppress appetite (leptin and ciliary neurotrophic factor) or by supplementing the diet with 2-deoxy-d-glucose, which may act as a calorie restriction mimetic. The profound influences of the quantity and timing of food intake on neuronal function and vulnerability to disease have revealed novel molecular and cellular mechanisms whereby diet affects the nervous system, and are leading to novel preventative and

  17. Asymmetry in dentition and shape of pharyngeal arches in the clonal fish Chrosomus eos-neogaeus: Phenotypic plasticity and developmental instability

    PubMed Central

    Leung, Christelle; Duclos, Kevin Karl; Grünbaum, Thomas; Cloutier, Richard

    2017-01-01

    The effect of the environment may result in different developmental outcomes. Extrinsic signals can modify developmental pathways and result in alternative phenotypes (phenotypic plasticity). The environment can also be interpreted as a stressor and increase developmental instability (developmental noise). Directional and fluctuating asymmetry provide a conceptual background to discriminate between these results. This study aims at assessing whether variation in dentition and shape of pharyngeal arches of the clonal fish Chrosomus eos-neogaeus results from developmental instability or environmentally induced changes. A total of 262 specimens of the Chrosomus eos-neogaeus complex from 12 natural sites were analysed. X-ray microcomputed tomography (X-ray micro-CT) was used to visualize the pharyngeal arches in situ with high resolution. Variation in the number of pharyngeal teeth is high in hybrids in contrast to the relative stability observed in both parental species. The basal dental formula is symmetric while the most frequent alternative dental formula is asymmetric. Within one lineage, large variation in the proportion of individuals bearing basal or alternative dental formulae was observed among sites in the absence of genetic difference. Both dentition and arch shape of this hybrid lineage were explained significantly by environmental differences. Only individuals bearing asymmetric dental formula displayed fluctuating asymmetry as well as directional left-right asymmetry for the arches. The hybrids appeared sensitive to environmental signals and intraspecific variation on pharyngeal teeth was not random but reflects phenotypic plasticity. Altogether, these results support the influence of the environment as a trigger for an alternative developmental pathway resulting in left-right asymmetry in dentition and shape of pharyngeal arches. PMID:28380079

  18. Asymmetry in dentition and shape of pharyngeal arches in the clonal fish Chrosomus eos-neogaeus: Phenotypic plasticity and developmental instability.

    PubMed

    Leung, Christelle; Duclos, Kevin Karl; Grünbaum, Thomas; Cloutier, Richard; Angers, Bernard

    2017-01-01

    The effect of the environment may result in different developmental outcomes. Extrinsic signals can modify developmental pathways and result in alternative phenotypes (phenotypic plasticity). The environment can also be interpreted as a stressor and increase developmental instability (developmental noise). Directional and fluctuating asymmetry provide a conceptual background to discriminate between these results. This study aims at assessing whether variation in dentition and shape of pharyngeal arches of the clonal fish Chrosomus eos-neogaeus results from developmental instability or environmentally induced changes. A total of 262 specimens of the Chrosomus eos-neogaeus complex from 12 natural sites were analysed. X-ray microcomputed tomography (X-ray micro-CT) was used to visualize the pharyngeal arches in situ with high resolution. Variation in the number of pharyngeal teeth is high in hybrids in contrast to the relative stability observed in both parental species. The basal dental formula is symmetric while the most frequent alternative dental formula is asymmetric. Within one lineage, large variation in the proportion of individuals bearing basal or alternative dental formulae was observed among sites in the absence of genetic difference. Both dentition and arch shape of this hybrid lineage were explained significantly by environmental differences. Only individuals bearing asymmetric dental formula displayed fluctuating asymmetry as well as directional left-right asymmetry for the arches. The hybrids appeared sensitive to environmental signals and intraspecific variation on pharyngeal teeth was not random but reflects phenotypic plasticity. Altogether, these results support the influence of the environment as a trigger for an alternative developmental pathway resulting in left-right asymmetry in dentition and shape of pharyngeal arches.

  19. 40 CFR 63.5795 - How do I know if my reinforced plastic composites production facility is a new affected source or...

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 13 2014-07-01 2014-07-01 false How do I know if my reinforced plastic... Emissions Standards for Hazardous Air Pollutants: Reinforced Plastic Composites Production What This Subpart Covers § 63.5795 How do I know if my reinforced plastic composites production facility is a new affected...

  20. 40 CFR 63.5795 - How do I know if my reinforced plastic composites production facility is a new affected source or...

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 13 2012-07-01 2012-07-01 false How do I know if my reinforced plastic... Emissions Standards for Hazardous Air Pollutants: Reinforced Plastic Composites Production What This Subpart Covers § 63.5795 How do I know if my reinforced plastic composites production facility is a new affected...

  1. 40 CFR 63.5795 - How do I know if my reinforced plastic composites production facility is a new affected source or...

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 12 2011-07-01 2009-07-01 true How do I know if my reinforced plastic... for Hazardous Air Pollutants: Reinforced Plastic Composites Production What This Subpart Covers § 63.5795 How do I know if my reinforced plastic composites production facility is a new affected source or...

  2. 40 CFR 63.5795 - How do I know if my reinforced plastic composites production facility is a new affected source or...

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 13 2013-07-01 2012-07-01 true How do I know if my reinforced plastic... Emissions Standards for Hazardous Air Pollutants: Reinforced Plastic Composites Production What This Subpart Covers § 63.5795 How do I know if my reinforced plastic composites production facility is a new affected...

  3. Cognitive-affective neural plasticity following active-controlled mindfulness intervention

    PubMed Central

    Allen, Micah; Dietz, Martin; Blair, Karina S.; van Beek, Martijn; Rees, Geraint; Vestergaard-Poulsen, Peter; Lutz, Antoine; Roepstorff, Andreas

    2015-01-01

    Mindfulness meditation is a set of attention-based, regulatory and self-inquiry training regimes. Although the impact of mindfulness meditation training (MT) on self-regulation is well established, the neural mechanisms supporting such plasticity are poorly understood. MT is thought to act on attention through interoceptive salience and attentional control mechanisms, but until now conflicting evidence from behavioral and neural measures has made it difficult to distinguish the role of these mechanisms. To resolve this question we conducted a fully randomized 6-week longitudinal trial of MT, explicitly controlling for cognitive and treatment effects with an active control group. We measured behavioral metacognition and whole-brain Blood Oxygenation Level Dependent (BOLD) signals using functional MRI during an affective Stroop task before and after intervention. Although both groups improved significantly on a response-inhibition task, only the MT group showed reduced affective Stroop conflict. Moreover, the MT group displayed greater dorsolateral prefrontal cortex (DLPFC) responses during executive processing, consistent with increased recruitment of top-down mechanisms to resolve conflict. In contrast, we did not observe overall group by time interactions on negative affect-related RTs or BOLD responses. However, only participants with the greatest amount of MT practice showed improvements in response-inhibition and increased recruitment of dorsal anterior cingulate cortex (dACC), medial prefrontal cortex (mPFC), and right anterior insula during negative valence processing. Collectively our findings highlight the importance of active control in MT research, and indicate unique neural mechanisms for progressive stages of mindfulness training. PMID:23115195

  4. Glutamatergic plasticity and alcohol dependence-induced alterations in reward, affect and cognition

    PubMed Central

    Burnett, Elizabeth J; Chandler, L Judson; Trantham-Davidson, Heather

    2015-01-01

    Introduction Alcohol dependence is characterized by a reduction in reward threshold, development of a negative affective state, and significant cognitive impairments. Dependence-induced glutamatergic neuroadaptations in the neurocircuitry mediating reward, affect and cognitive function are thought to underlie the neural mechanism for these alterations. These changes serve to promote increased craving for alcohol and facilitate the development of maladaptive behaviors that promote relapse to alcohol drinking during periods of abstinence. Objective To review the extant literature on the effects of chronic alcohol exposure on glutamatergic neurotransmission and its impact on reward, affect and cognition. Results Evidence from a diverse set of studies demonstrates significant enhancement of glutamatergic activity following chronic alcohol exposure and up-regulation of GluN2B-containing NMDA receptor expression and function is a commonly observed phenomenon that likely reflects activity-dependent adaptive homeostatic plasticity. However, changes in NMDA receptors and additional glutamatergic neuroadaptations are often circuit and cell-type specific. Discussion Dependence-induced alterations in glutamate signaling contribute to many of the symptoms experienced in addicted individuals and can persist well into abstinence. This suggests they play an important role in the development of behaviors that increase the probability for relapse. As our understanding of the complexity of the neurocircuitry involved in the addictive process has advanced, it has become increasingly clear that investigations of cell-type and circuit-specific effects are required to gain a more comprehensive understanding of the glutamatergic adaptations and their functional consequences in alcohol addiction. Conclusion While pharmacological treatments for alcohol dependence and relapse targeting the glutamatergic system have shown great promise in preclinical models, more research is needed to uncover

  5. Cognitive-affective neural plasticity following active-controlled mindfulness intervention.

    PubMed

    Allen, Micah; Dietz, Martin; Blair, Karina S; van Beek, Martijn; Rees, Geraint; Vestergaard-Poulsen, Peter; Lutz, Antoine; Roepstorff, Andreas

    2012-10-31

    Mindfulness meditation is a set of attention-based, regulatory, and self-inquiry training regimes. Although the impact of mindfulness training (MT) on self-regulation is well established, the neural mechanisms supporting such plasticity are poorly understood. MT is thought to act through interoceptive salience and attentional control mechanisms, but until now conflicting evidence from behavioral and neural measures renders difficult distinguishing their respective roles. To resolve this question we conducted a fully randomized 6 week longitudinal trial of MT, explicitly controlling for cognitive and treatment effects with an active-control group. We measured behavioral metacognition and whole-brain blood oxygenation level-dependent (BOLD) signals using functional MRI during an affective Stroop task before and after intervention in healthy human subjects. Although both groups improved significantly on a response-inhibition task, only the MT group showed reduced affective Stroop conflict. Moreover, the MT group displayed greater dorsolateral prefrontal cortex responses during executive processing, consistent with increased recruitment of top-down mechanisms to resolve conflict. In contrast, we did not observe overall group-by-time interactions on negative affect-related reaction times or BOLD responses. However, only participants with the greatest amount of MT practice showed improvements in response inhibition and increased recruitment of dorsal anterior cingulate cortex, medial prefrontal cortex, and right anterior insula during negative valence processing. Our findings highlight the importance of active control in MT research, indicate unique neural mechanisms for progressive stages of mindfulness training, and suggest that optimal application of MT may differ depending on context, contrary to a one-size-fits-all approach.

  6. Optimal level activity of matrix metalloproteinases is critical for adult visual plasticity in the healthy and stroke-affected brain

    PubMed Central

    Pielecka-Fortuna, Justyna; Kalogeraki, Evgenia; Fortuna, Michal G; Löwel, Siegrid

    2015-01-01

    The ability of the adult brain to undergo plastic changes is of particular interest in medicine, especially regarding recovery from injuries or improving learning and cognition. Matrix metalloproteinases (MMPs) have been associated with juvenile experience-dependent primary visual cortex (V1) plasticity, yet little is known about their role in this process in the adult V1. Activation of MMPs is a crucial step facilitating structural changes in a healthy brain; however, upon brain injury, upregulated MMPs promote the spread of a lesion and impair recovery. To clarify these seemingly opposing outcomes of MMP-activation, we examined the effects of MMP-inhibition on experience-induced plasticity in healthy and stoke-affected adult mice. In healthy animals, 7-day application of MMP-inhibitor prevented visual plasticity. Additionally, treatment with MMP-inhibitor once but not twice following stroke rescued plasticity, normally lost under these conditions. Our data imply that an optimal level of MMP-activity is crucial for adult visual plasticity to occur. DOI: http://dx.doi.org/10.7554/eLife.11290.001 PMID:26609811

  7. Optimal level activity of matrix metalloproteinases is critical for adult visual plasticity in the healthy and stroke-affected brain.

    PubMed

    Pielecka-Fortuna, Justyna; Kalogeraki, Evgenia; Fortuna, Michal G; Löwel, Siegrid

    2015-11-26

    The ability of the adult brain to undergo plastic changes is of particular interest in medicine, especially regarding recovery from injuries or improving learning and cognition. Matrix metalloproteinases (MMPs) have been associated with juvenile experience-dependent primary visual cortex (V1) plasticity, yet little is known about their role in this process in the adult V1. Activation of MMPs is a crucial step facilitating structural changes in a healthy brain; however, upon brain injury, upregulated MMPs promote the spread of a lesion and impair recovery. To clarify these seemingly opposing outcomes of MMP-activation, we examined the effects of MMP-inhibition on experience-induced plasticity in healthy and stoke-affected adult mice. In healthy animals, 7-day application of MMP-inhibitor prevented visual plasticity. Additionally, treatment with MMP-inhibitor once but not twice following stroke rescued plasticity, normally lost under these conditions. Our data imply that an optimal level of MMP-activity is crucial for adult visual plasticity to occur.

  8. Increasing preoperative dislocations and total time of dislocation affect surgical management of anterior shoulder instability

    PubMed Central

    Denard, Patrick J.; Dai, Xuesong; Burkhart, Stephen S.

    2015-01-01

    Purpose: Our purpose was to determine the relationship between number of preoperative shoulder dislocations and total dislocation time and the need to perform bone deficiency procedures at the time of primary anterior instability surgery. Our hypothesis was that need for bone deficiency procedures would increase with the total number and hours of dislocation. Materials and Methods: A retrospective review was performed of primary instability surgeries performed by a single surgeon. Patients with <25% glenoid bone loss were treated with an isolated arthroscopic Bankart repair. Those who also had an engaging Hill-Sachs lesion underwent arthroscopic Bankart repair with remplissage. Patients with >25% glenoid bone loss were treated with Latarjet reconstruction. Number of dislocations and total dislocation time were examined for their relationship with the treatment method. Results: Ten arthroscopic Bankart repairs, 13 arthroscopic Bankart plus remplissage procedures, and 9 Latarjet reconstructions were available for review. Total dislocations (P = 0.012) and total hours of dislocation (P = 0.019) increased from the Bankart, to the remplissage, to the Latarjet groups. Patients with a total dislocation time of 5 h or more were more likely to require a Latarjet reconstruction (P = 0.039). Patients with only 1 preoperative dislocation were treated with an isolated Bankart repair in 64% (7 of 11) of cases, whereas those with 2 or more dislocations required a bone loss procedure in 86% (18 of 21) of cases (P = 0.013). Conclusion: Increasing number of dislocations and total dislocation time are associated with the development of glenoid and humeral head bony lesions that alter surgical management of anterior shoulder instability. The necessity for the addition of a remplissage to an arthroscopic Bankart repair or the use of a Latarjet reconstruction increases with only 1 recurrent dislocation. Level of evidence: Level III, retrospective comparative study. PMID:25709237

  9. Experience Affects Critical Period Plasticity in the Visual Cortex through an Epigenetic Regulation of Histone Post-Translational Modifications.

    PubMed

    Baroncelli, Laura; Scali, Manuela; Sansevero, Gabriele; Olimpico, Francesco; Manno, Ilaria; Costa, Mario; Sale, Alessandro

    2016-03-23

    During an early phase of enhanced sensitivity called the critical period (CP), monocular deprivation causes a shift in the response of visual cortex binocular neurons in favor of the nondeprived eye, a process named ocular dominance (OD) plasticity. While the time course of the CP for OD plasticity can be modulated by genetic/pharmacological interventions targeting GABAergic inhibition, whether an increased sensory-motor experience can affect this major plastic phenomenon is not known. We report that exposure to environmental enrichment (EE) accelerated the closure of the CP for OD plasticity in the rat visual cortex. Histone H3 acetylation was developmentally regulated in primary visual cortex, with enhanced levels being detectable early in enriched pups, and chromatin immunoprecipitation revealed an increase at the level of the BDNF P3 promoter. Administration of the histone deacetylase inhibitor SAHA (suberoylanilide hydroxamic acid) to animals reared in a standard cage mimicked the increase in H3 acetylation observed in the visual cortex and resulted in an accelerated decay of OD plasticity. Finally, exposure to EE in adulthood upregulated H3 acetylation and was paralleled by a reopening of the CP. These findings demonstrate a critical involvement of the epigenetic machinery as a mediator of visual cortex developmental plasticity and of the impact of EE on OD plasticity. While it is known that an epigenetic remodeling of chromatin structure controls developmental plasticity in the visual cortex, three main questions have remained open. Which is the physiological time course of histone modifications? Is it possible, by manipulating the chromatin epigenetic state, to modulate plasticity levels during the critical period? How can we regulate histone acetylation in the adult brain in a noninvasive manner? We show that the early exposure of rat pups to enriching environmental conditions accelerates the critical period for plasticity in the primary visual cortex

  10. Spines slow down dendritic chloride diffusion and affect short-term ionic plasticity of GABAergic inhibition

    NASA Astrophysics Data System (ADS)

    Mohapatra, Namrata; Tønnesen, Jan; Vlachos, Andreas; Kuner, Thomas; Deller, Thomas; Nägerl, U. Valentin; Santamaria, Fidel; Jedlicka, Peter

    2016-03-01

    Cl‑ plays a crucial role in neuronal function and synaptic inhibition. However, the impact of neuronal morphology on the diffusion and redistribution of intracellular Cl‑ is not well understood. The role of spines in Cl‑ diffusion along dendritic trees has not been addressed so far. Because measuring fast and spatially restricted Cl‑ changes within dendrites is not yet technically possible, we used computational approaches to predict the effects of spines on Cl‑ dynamics in morphologically complex dendrites. In all morphologies tested, including dendrites imaged by super-resolution STED microscopy in live brain tissue, spines slowed down longitudinal Cl‑ diffusion along dendrites. This effect was robust and could be observed in both deterministic as well as stochastic simulations. Cl‑ extrusion altered Cl‑ diffusion to a much lesser extent than the presence of spines. The spine-dependent slowing of Cl‑ diffusion affected the amount and spatial spread of changes in the GABA reversal potential thereby altering homosynaptic as well as heterosynaptic short-term ionic plasticity at GABAergic synapses in dendrites. Altogether, our results suggest a fundamental role of dendritic spines in shaping Cl‑ diffusion, which could be of relevance in the context of pathological conditions where spine densities and neural excitability are perturbed.

  11. Social competition affects electric signal plasticity and steroid levels in the gymnotiform fish Brachyhypopomus gauderio.

    PubMed

    Salazar, Vielka L; Stoddard, Philip K

    2009-10-01

    Sexually-selected communication signals can be used by competing males to settle contests without incurring the costs of fighting. Steroid regulation of these signals can render them as reliable indicators of a male's physiological state. We investigated how plasticity in electrocommunication signals is driven by social competition for mates, mediated by steroid hormones, and subject to the effects of past social experience. We measured the electric waveform's amplitude and duration and steroid hormone levels of male gymnotiform electric fish (Brachyhypopomus gauderio) following week-long periods of social isolation, and low or high social competition. To quantify the effect of social history on the modulation of the electric signal, six groups of six males experienced all three social conditions but in different order. We found that males differentially modulate their electric signals depending on the order they experienced these conditions. Thus, past social interactions affect both present and future social electric signals. Cortisol levels and the amplitude of the electric signal appeared to track the intensity of competition, while androgen levels and the duration of the electric signal only responded to the presence (low and high competition) or absence (isolation) of a social environment (low and high androgens respectively). In addition, cortisol levels were related to the body size of the males at high social competition. Taken together, these findings suggest that the capacity of males to modulate their signals in response to social competition is regulated by steroids.

  12. Spines slow down dendritic chloride diffusion and affect short-term ionic plasticity of GABAergic inhibition

    PubMed Central

    Mohapatra, Namrata; Tønnesen, Jan; Vlachos, Andreas; Kuner, Thomas; Deller, Thomas; Nägerl, U. Valentin; Santamaria, Fidel; Jedlicka, Peter

    2016-01-01

    Cl− plays a crucial role in neuronal function and synaptic inhibition. However, the impact of neuronal morphology on the diffusion and redistribution of intracellular Cl− is not well understood. The role of spines in Cl− diffusion along dendritic trees has not been addressed so far. Because measuring fast and spatially restricted Cl− changes within dendrites is not yet technically possible, we used computational approaches to predict the effects of spines on Cl− dynamics in morphologically complex dendrites. In all morphologies tested, including dendrites imaged by super-resolution STED microscopy in live brain tissue, spines slowed down longitudinal Cl− diffusion along dendrites. This effect was robust and could be observed in both deterministic as well as stochastic simulations. Cl− extrusion altered Cl− diffusion to a much lesser extent than the presence of spines. The spine-dependent slowing of Cl− diffusion affected the amount and spatial spread of changes in the GABA reversal potential thereby altering homosynaptic as well as heterosynaptic short-term ionic plasticity at GABAergic synapses in dendrites. Altogether, our results suggest a fundamental role of dendritic spines in shaping Cl− diffusion, which could be of relevance in the context of pathological conditions where spine densities and neural excitability are perturbed. PMID:26987404

  13. Spines slow down dendritic chloride diffusion and affect short-term ionic plasticity of GABAergic inhibition.

    PubMed

    Mohapatra, Namrata; Tønnesen, Jan; Vlachos, Andreas; Kuner, Thomas; Deller, Thomas; Nägerl, U Valentin; Santamaria, Fidel; Jedlicka, Peter

    2016-03-18

    Cl(-) plays a crucial role in neuronal function and synaptic inhibition. However, the impact of neuronal morphology on the diffusion and redistribution of intracellular Cl(-) is not well understood. The role of spines in Cl(-) diffusion along dendritic trees has not been addressed so far. Because measuring fast and spatially restricted Cl(-) changes within dendrites is not yet technically possible, we used computational approaches to predict the effects of spines on Cl(-) dynamics in morphologically complex dendrites. In all morphologies tested, including dendrites imaged by super-resolution STED microscopy in live brain tissue, spines slowed down longitudinal Cl(-) diffusion along dendrites. This effect was robust and could be observed in both deterministic as well as stochastic simulations. Cl(-) extrusion altered Cl(-) diffusion to a much lesser extent than the presence of spines. The spine-dependent slowing of Cl(-) diffusion affected the amount and spatial spread of changes in the GABA reversal potential thereby altering homosynaptic as well as heterosynaptic short-term ionic plasticity at GABAergic synapses in dendrites. Altogether, our results suggest a fundamental role of dendritic spines in shaping Cl(-) diffusion, which could be of relevance in the context of pathological conditions where spine densities and neural excitability are perturbed.

  14. Will phenotypic plasticity affecting flowering phenology keep pace with climate change?

    Treesearch

    Bryce A. Richardson; Linsay Chaney; Nancy L. Shaw; Shannon M. Still

    2016-01-01

    Rising temperatures have begun to shift flowering time, but it is unclear whether phenotypic plasticity can accommodate projected temperature change for this century. Evaluating clines in phenological traits and the extent and variation in plasticity can provide key information on assessing risk of maladaptation and developing strategies to mitigate climate change. In...

  15. Incipient plasticity in metallic thin films

    NASA Astrophysics Data System (ADS)

    Soer, W. A.; De Hosson, J. Th. M.; Minor, A. M.; Shan, Z.; Syed Asif, S. A.; Warren, O. L.

    2007-04-01

    The authors have compared the incipient plastic behaviors of Al and Al-Mg thin films during indentation under load control and displacement control. In Al-Mg, solute pinning limits the ability of dislocations to propagate into the crystal and thus substantially affects the appearance of plastic instabilities as compared to pure Al. Displacement control allows for a more sensitive detection of such instabilities, as it does not require collective dislocation motion to the extent required by load-controlled indentation in order to resolve a yield event. This perception is supported by in situ transmission electron microscopy observations.

  16. Investigation of instabilities affecting detonations: Improving the resolution using block-structured adaptive mesh refinement

    NASA Astrophysics Data System (ADS)

    Ravindran, Prashaanth

    The unstable nature of detonation waves is a result of the critical relationship between the hydrodynamic shock and the chemical reactions sustaining the shock. A perturbative analysis of the critical point is quite challenging due to the multiple spatio-temporal scales involved along with the non-linear nature of the shock-reaction mechanism. The author's research attempts to provide detailed resolution of the instabilities at the shock front. Another key aspect of the present research is to develop an understanding of the causality between the non-linear dynamics of the front and the eventual breakdown of the sub-structures. An accurate numerical simulation of detonation waves requires a very efficient solution of the Euler equations in conservation form with detailed, non-equilibrium chemistry. The difference in the flow and reaction length scales results in very stiff source terms, requiring the problem to be solved with adaptive mesh refinement. For this purpose, Berger-Colella's block-structured adaptive mesh refinement (AMR) strategy has been developed and applied to time-explicit finite volume methods. The block-structured technique uses a hierarchy of parent-child sub-grids, integrated recursively over time. One novel approach to partition the problem within a large supercomputer was the use of modified Peano-Hilbert space filling curves. The AMR framework was merged with CLAWPACK, a package providing finite volume numerical methods tailored for wave-propagation problems. The stiffness problem is bypassed by using a 1st order Godunov or a 2nd order Strang splitting technique, where the flow variables and source terms are integrated independently. A linearly explicit fourth-order Runge-Kutta integrator is used for the flow, and an ODE solver was used to overcome the numerical stiffness. Second-order spatial resolution is obtained by using a second-order Roe-HLL scheme with the inclusion of numerical viscosity to stabilize the solution near the discontinuity

  17. Intra-day signal instabilities affect decoding performance in an intracortical neural interface system.

    PubMed

    Perge, János A; Homer, Mark L; Malik, Wasim Q; Cash, Sydney; Eskandar, Emad; Friehs, Gerhard; Donoghue, John P; Hochberg, Leigh R

    2013-06-01

    Motor neural interface systems (NIS) aim to convert neural signals into motor prosthetic or assistive device control, allowing people with paralysis to regain movement or control over their immediate environment. Effector or prosthetic control can degrade if the relationship between recorded neural signals and intended motor behavior changes. Therefore, characterizing both biological and technological sources of signal variability is important for a reliable NIS. To address the frequency and causes of neural signal variability in a spike-based NIS, we analyzed within-day fluctuations in spiking activity and action potential amplitude recorded with silicon microelectrode arrays implanted in the motor cortex of three people with tetraplegia (BrainGate pilot clinical trial, IDE). 84% of the recorded units showed a statistically significant change in apparent firing rate (3.8 ± 8.71 Hz or 49% of the mean rate) across several-minute epochs of tasks performed on a single session, and 74% of the units showed a significant change in spike amplitude (3.7 ± 6.5 µV or 5.5% of mean spike amplitude). 40% of the recording sessions showed a significant correlation in the occurrence of amplitude changes across electrodes, suggesting array micro-movement. Despite the relatively frequent amplitude changes, only 15% of the observed within-day rate changes originated from recording artifacts such as spike amplitude change or electrical noise, while 85% of the rate changes most likely emerged from physiological mechanisms. Computer simulations confirmed that systematic rate changes of individual neurons could produce a directional 'bias' in the decoded neural cursor movements. Instability in apparent neuronal spike rates indeed yielded a directional bias in 56% of all performance assessments in participant cursor control (n = 2 participants, 108 and 20 assessments over two years), resulting in suboptimal performance in these sessions. We anticipate that signal acquisition and

  18. Low-Volatility Model Demonstrates Humidity Affects Environmental Toxin Deposition on Plastics at a Molecular Level.

    PubMed

    Hankett, Jeanne M; Collin, William R; Yang, Pei; Chen, Zhan; Duhaime, Melissa

    2016-02-02

    Despite the ever-increasing prevalence of plastic debris and endocrine disrupting toxins in aquatic ecosystems, few studies describe their interactions in freshwater environments. We present a model system to investigate the deposition/desorption behaviors of low-volatility lake ecosystem toxins on microplastics in situ and in real time. Molecular interactions of gas-phase nonylphenols (NPs) with the surfaces of two common plastics, poly(styrene) and poly(ethylene terephthalate), were studied using quartz crystal microbalance and sum frequency generation vibrational spectroscopy. NP point sources were generated under two model environments: plastic on land and plastic on a freshwater surface. We found the headspace above calm water provides an excellent environment for NP deposition and demonstrate significant NP deposition on plastic within minutes at relevant concentrations. Further, NP deposits and orders differently on both plastics under humid versus dry environments. We attributed the unique deposition behaviors to surface energy changes from increased water content during the humid deposition. Lastly, nanograms of NP remained on microplastic surfaces hours after initial NP introduction and agitating conditions, illustrating feasibility for plastic-bound NPs to interact with biota and surrounding matter. Our model studies reveal important interactions between low-volatility environmental toxins and microplastics and hold potential to correlate the environmental fate of endocrine disrupting toxins in the Great Lakes with molecular behaviors.

  19. Legal and institutional tools to mitigate plastic pollution affecting marine species: Argentina as a case study.

    PubMed

    González Carman, Victoria; Machain, Natalia; Campagna, Claudio

    2015-03-15

    Plastics are the most common form of debris found along the Argentine coastline. The Río de la Plata estuarine area is a relevant case study to describe a situation where ample policy exists against a backdrop of plastics disposed by populated coastal areas, industries, and vessels; with resultant high impacts of plastic pollution on marine turtles and mammals. Policy and institutions are in place but the impact remains due to ineffective waste management, limited public education and awareness, and weaknesses in enforcement of regulations. This context is frequently repeated all over the world. We list possible interventions to increase the effectiveness of policy that require integrating efforts among governments, the private sector, non-governmental organizations and the inhabitants of coastal cities to reduce the amount of plastics reaching the Río de la Plata and protect threatened marine species. What has been identified for Argentina applies to the region and globally.

  20. Intra-day signal instabilities affect decoding performance in an intracortical neural interface system

    PubMed Central

    Perge, János A.; Homer, Mark L.; Malik, Wasim Q.; Cash, Sydney; Eskandar, Emad; Friehs, Gerhard; Donoghue, John P.; Hochberg, Leigh R.

    2013-01-01

    Objective Motor Neural Interface Systems (NIS) aim to convert neural signals into motor prosthetic or assistive device control, allowing people with paralysis to regain movement or control over their immediate environment. Effector or prosthetic control can degrade if the relationship between recorded neural signals and intended motor behavior changes. Therefore, characterizing both biological and technological sources of signal variability is important for a reliable NIS. Approach To address the frequency and causes of neural signal variability in a spike-based NIS, we analyzed within-day fluctuations in spiking activity and action potential amplitude recorded with silicon microelectrode arrays implanted in the motor cortex of three people with tetraplegia (BrainGate pilot clinical trial, IDE). Main results Eighty-four percent of the recorded units showed a statistically significant change in apparent firing rate (3.8±8.71Hz or 49% of the mean rate) across several-minute epochs of tasks performed on a single session, and seventy-four percent of the units showed a significant change in spike amplitude (3.7±6.5μV or 5.5% of mean spike amplitude). Forty percent of the recording sessions showed a significant correlation in the occurrence of amplitude changes across electrodes, suggesting array micro-movement. Despite the relatively frequent amplitude changes, only 15% of the observed within-day rate changes originated from recording artifacts such as spike amplitude change or electrical noise, while 85% of the rate changes most likely emerged from physiological mechanisms. Computer simulations confirmed that systematic rate changes of individual neurons could produce a directional “bias” in the decoded neural cursor movements. Instability in apparent neuronal spike rates indeed yielded a directional bias in fifty-six percent of all performance assessments in participant cursor control (n=2 participants, 108 and 20 assessments over two years), resulting in

  1. Intra-day signal instabilities affect decoding performance in an intracortical neural interface system

    NASA Astrophysics Data System (ADS)

    Perge, János A.; Homer, Mark L.; Malik, Wasim Q.; Cash, Sydney; Eskandar, Emad; Friehs, Gerhard; Donoghue, John P.; Hochberg, Leigh R.

    2013-06-01

    Objective. Motor neural interface systems (NIS) aim to convert neural signals into motor prosthetic or assistive device control, allowing people with paralysis to regain movement or control over their immediate environment. Effector or prosthetic control can degrade if the relationship between recorded neural signals and intended motor behavior changes. Therefore, characterizing both biological and technological sources of signal variability is important for a reliable NIS. Approach. To address the frequency and causes of neural signal variability in a spike-based NIS, we analyzed within-day fluctuations in spiking activity and action potential amplitude recorded with silicon microelectrode arrays implanted in the motor cortex of three people with tetraplegia (BrainGate pilot clinical trial, IDE). Main results. 84% of the recorded units showed a statistically significant change in apparent firing rate (3.8 ± 8.71 Hz or 49% of the mean rate) across several-minute epochs of tasks performed on a single session, and 74% of the units showed a significant change in spike amplitude (3.7 ± 6.5 µV or 5.5% of mean spike amplitude). 40% of the recording sessions showed a significant correlation in the occurrence of amplitude changes across electrodes, suggesting array micro-movement. Despite the relatively frequent amplitude changes, only 15% of the observed within-day rate changes originated from recording artifacts such as spike amplitude change or electrical noise, while 85% of the rate changes most likely emerged from physiological mechanisms. Computer simulations confirmed that systematic rate changes of individual neurons could produce a directional ‘bias’ in the decoded neural cursor movements. Instability in apparent neuronal spike rates indeed yielded a directional bias in 56% of all performance assessments in participant cursor control (n = 2 participants, 108 and 20 assessments over two years), resulting in suboptimal performance in these sessions

  2. Impairment of systemic DHA synthesis affects macrophage plasticity and polarization: implications for DHA supplementation during inflammation.

    PubMed

    Talamonti, Emanuela; Pauter, Anna M; Asadi, Abolfazl; Fischer, Alexander W; Chiurchiù, Valerio; Jacobsson, Anders

    2017-08-01

    Docosahexaenoic acid (DHA) is an omega-3 fatty acid obtained from the diet or synthesized from alpha-linolenic acid through the action of fatty acid elongases (ELOVL) and desaturases. DHA plays important roles in the central nervous system as well as in peripheral organs and is the precursor of several molecules that regulate resolution of inflammation. In the present study, we questioned whether impaired synthesis of DHA affected macrophage plasticity and polarization both in vitro and in vivo models. For this we investigated the activation status and inflammatory response of bone marrow-derived M1 and M2 macrophages obtained from mice deficient of Elovl2 (Elovl2(-/-)), a key enzyme for DHA synthesis in mammals. Although both wild type and Elovl2(-/-) mice were able to generate efficient M1 and M2 macrophages, M1 cells derived from Elovl2(-/-) mice showed an increased expression of key markers (iNOS, CD86 and MARCO) and cytokines (IL-6, IL-12 and IL-23). However, M2 macrophages exhibited upregulated M1-like markers like CD80, CD86 and IL-6, concomitantly with a downregulation of their signature marker CD206. These effects were counteracted in cells obtained from DHA-supplemented animals. Finally, white adipose tissue of Elovl2(-/-) mice presented an M1-like pro-inflammatory phenotype. Hence, impairment of systemic DHA synthesis delineates an alteration of M1/M2 macrophages both in vitro and in vivo, with M1 being hyperactive and more pro-inflammatory while M2 less protective, supporting the view that DHA has a key role in controlling the balance between pro- and anti-inflammatory processes.

  3. Fertilization and colors of plastic mulch affect biomass and essential oil of sweet-scented geranium.

    PubMed

    Silva, Anderson de Carvalho; Blank, Arie Fitzgerald; dos Santos, Wallace Melo; Prata, Paloma Santana; Alves, Péricles Barreto; Arrigoni-Blank, Maria de Fátima

    2014-01-01

    Sweet-scented geranium (Pelargonium graveolens L'Hér), a plant belonging to the Geraniaceae family, has medicinal and aromatic properties and is widely used in the cosmetic, soap, perfume, aromatherapy, and food industries. The aim of this study was to evaluate the influence of fertilization and the use of different colors of plastic mulch on sweet-scented geranium biomass and essential oil. Three colors of plastic mulch (black, white, and silver-colored) and a control without plastic mulch were assessed along with three fertilizers (20,000 L · ha(-1) of cattle manure; 1,000 kg · ha(-1) of NPK 3-12-6; and 20,000 L · ha(-1) of cattle manure + 1,000 kg · ha(-1) of NPK 3-12-6 fertilizer) and a control without fertilizer. The absence of a soil cover negatively influenced the agronomical variables, while coverage with plastic mulch was associated with increased biomass. The use of fertilizer had no effect on the evaluated agronomic variables. When cattle manure and NPK 3-12-6 were used together, combined with white or black plastic mulch, the highest yields of essential oil were obtained. For the silver-colored plastic mulch, higher amounts of essential oil (6,9-guaiadien) were obtained with mineral fertilizer.

  4. Fertilization and Colors of Plastic Mulch Affect Biomass and Essential Oil of Sweet-Scented Geranium

    PubMed Central

    Silva, Anderson de Carvalho; dos Santos, Wallace Melo; Prata, Paloma Santana; Alves, Péricles Barreto

    2014-01-01

    Sweet-scented geranium (Pelargonium graveolens L'Hér), a plant belonging to the Geraniaceae family, has medicinal and aromatic properties and is widely used in the cosmetic, soap, perfume, aromatherapy, and food industries. The aim of this study was to evaluate the influence of fertilization and the use of different colors of plastic mulch on sweet-scented geranium biomass and essential oil. Three colors of plastic mulch (black, white, and silver-colored) and a control without plastic mulch were assessed along with three fertilizers (20,000 L·ha−1 of cattle manure; 1,000 kg·ha−1 of NPK 3-12-6; and 20,000 L·ha−1 of cattle manure + 1,000 kg·ha−1 of NPK 3-12-6 fertilizer) and a control without fertilizer. The absence of a soil cover negatively influenced the agronomical variables, while coverage with plastic mulch was associated with increased biomass. The use of fertilizer had no effect on the evaluated agronomic variables. When cattle manure and NPK 3-12-6 were used together, combined with white or black plastic mulch, the highest yields of essential oil were obtained. For the silver-colored plastic mulch, higher amounts of essential oil (6,9-guaiadien) were obtained with mineral fertilizer. PMID:24757440

  5. Interfacial instabilities affect microfluidic extraction of small molecules from non-Newtonian fluids.

    PubMed

    Helton, Kristen L; Yager, Paul

    2007-11-01

    As part of a project to develop an integrated microfluidic biosensor for the detection of small molecules in saliva, practical issues of extraction of analytes from non-Newtonian samples using an H-filter were explored. The H-filter can be used to rapidly and efficiently extract small molecules from a complex sample into a simpler buffer. The location of the interface between the sample and buffer streams is a critical parameter in the function of the H-filter, so fluorescence microscopy was employed to monitor the interface position; this revealed apparently anomalous fluorophore diffusion from the samples into the buffer solutions. Using confocal microscopy to understand the three-dimensional distribution of the fluorophore, it was found that the interface between the non-Newtonian sample and Newtonian buffer was both curved and unstable. The core of the non-Newtonian sample extended into the Newtonian buffer and its position was unstable, producing a fluorescence intensity profile that gave rise to the apparently anomalously fast fluorophore transport. These instabilities resulted from the pairing of rheologically dissimilar fluid streams and were flowrate dependent. We conclude that use of non-Newtonian fluids, such as saliva, in the H-filter necessitates pretreatment to reduce viscoelasticity. The interfacial variation in position, stability and shape caused by the non-Newtonian samples has substantial implications for the use of biological samples for quantitative analysis and analyte extraction in concurrent flow extraction devices.

  6. Inter-episode affective intensity and instability: predictors of depression and functional impairment in bipolar disorder.

    PubMed

    Gershon, Anda; Eidelman, Polina

    2015-03-01

    Dysregulated affect is a hallmark feature of acute episodes of bipolar disorder (BD) and persists during inter-episode periods. Its contribution to course of illness is not yet known. The present report examines the prospective influence of inter-episode affect dysregulation on symptoms and functional impairment in BD. Twenty-seven participants diagnosed with inter-episode bipolar I disorder completed daily measures of negative and positive affect for 49 days (±8 days) while they remained inter-episode. One month following this daily assessment period, symptom severity interviews and a measure of functional impairment were administered by telephone. More intense negative affect and positive affect during the inter-episode period were associated with higher depressive, but not manic, symptoms at the one-month follow-up assessment. More intense and unstable negative affect, and more unstable positive affect, during the inter-episode period were associated with greater impairment in home and work functioning at the follow-up assessment. All associations remained significant after controlling for concurrent symptom levels. The findings need to be confirmed in larger samples with longer follow-up periods. A more comprehensive assessment of functional impairment is also warranted. The findings suggest that a persistent affective dysregulation between episodes of BD may be an important predictor of depression and functional impairment. Monitoring daily affect during inter-episode periods could allow for a more timely application of interventions that aim to prevent or reduce depressive symptoms and improve functioning for individuals with BD. Copyright © 2014 Elsevier Ltd. All rights reserved.

  7. Affective and Self-Esteem Instability in the Daily Lives of People with Generalized Social Anxiety Disorder

    PubMed Central

    Farmer, Antonina S.; Kashdan, Todd B.

    2014-01-01

    Research on affect and self-esteem in social anxiety disorder (SAD) has focused on trait or average levels, but we know little about the dynamic patterns of these experiences in the daily lives of people with SAD. We asked 40 adults with SAD and 39 matched healthy controls to provide end-of-day reports on their affect and self-esteem over two weeks. Compared to healthy adults, participants with SAD exhibited greater instability of negative affect and self-esteem, though the self-esteem effect was driven by mean level differences. The SAD group also demonstrated a higher probability of acute changes in negative affect and self-esteem (i.e., from one assessment period to the next), as well as difficulty maintaining positive states and improving negative states (i.e., dysfunctional self-regulation). Our findings provide insights on the phenomenology of SAD, with particular attention to the temporal dependency, magnitude of change, and directional patterns of psychological experiences in everyday life. PMID:25821659

  8. "Does the Organization of Plastic Surgery Units into Independent Departments Affect Academic Productivity?"

    PubMed

    Loewenstein, Scott N; Duquette, Stephen; Valsangkar, Nakul; Avula, Umakanth; Lad, Neha; Socas, Juan; Flores, Roberto L; Sood, Rajiv; Koniaris, Leonidas G

    2017-07-12

    There is an increased push for plastic surgery units in the United States to become independent departments administered autonomously rather than as divisions of a multispecialty surgery department. The purpose of this research was to determine if there are any quantifiable differences in the academic performance of departments versus divisions. Using a list of the plastic surgery units affiliated with The American Council of Academic Plastic Surgeons (ACAPS), unit websites were queried for departmental status and to obtain a list of affiliated faculty. Academic productivity was then quantified using the SCOPUS database. National Institute of Health (NIH) funding was determined through the Research Portfolio Online Reporting Tools database. Plastic surgery departments were comparable to divisions in academic productivity, evidenced by a similar number of publications per faculty (38.9 versus 38.7; p=0.94), number of citations per faculty (692 versus 761; p=0.64), H-indices (9.9 versus 9.9; p=0.99), and NIH grants (3.25 versus 2.84; p=0.80), including RO1 grants (1.33 versus 0.84; p=0.53). There was a trend for departments to have a more equitable male to female ratio (2.8 versus 4.1; p=0.06), and departments trained a greater number of integrated plastic surgery residents (9.0 versus 5.28; p=0.03). This study demonstrates that the academic performance of independent plastic surgery departments is generally similar to divisions, but with nuanced distinctions.

  9. Habitat Fragmentation Differentially Affects Genetic Variation, Phenotypic Plasticity and Survival in Populations of a Gypsum Endemic.

    PubMed

    Matesanz, Silvia; Rubio Teso, María Luisa; García-Fernández, Alfredo; Escudero, Adrián

    2017-01-01

    Habitat fragmentation, i.e., fragment size and isolation, can differentially alter patterns of neutral and quantitative genetic variation, fitness and phenotypic plasticity of plant populations, but their effects have rarely been tested simultaneously. We assessed the combined effects of size and connectivity on these aspects of genetic and phenotypic variation in populations of Centaurea hyssopifolia, a narrow endemic gypsophile that previously showed performance differences associated with fragmentation. We grew 111 maternal families sampled from 10 populations that differed in their fragment size and connectivity in a common garden, and characterized quantitative genetic variation, phenotypic plasticity to drought for key functional traits, and plant survival, as a measure of population fitness. We also assessed neutral genetic variation within and among populations using eight microsatellite markers. Although C. hyssopifolia is a narrow endemic gypsophile, we found substantial neutral genetic variation and quantitative variation for key functional traits. The partition of genetic variance indicated that a higher proportion of variation was found within populations, which is also consistent with low population differentiation in molecular markers, functional traits and their plasticity. This, combined with the generally small effect of habitat fragmentation suggests that gene flow among populations is not restricted, despite large differences in fragment size and isolation. Importantly, population's similarities in genetic variation and plasticity did not reflect the lower survival observed in isolated populations. Overall, our results indicate that, although the species consists of genetically variable populations able to express functional plasticity, such aspects of adaptive potential may not always reflect populations' survival. Given the differential effects of habitat connectivity on functional traits, genetic variation and fitness, our study highlights

  10. Habitat Fragmentation Differentially Affects Genetic Variation, Phenotypic Plasticity and Survival in Populations of a Gypsum Endemic

    PubMed Central

    Matesanz, Silvia; Rubio Teso, María Luisa; García-Fernández, Alfredo; Escudero, Adrián

    2017-01-01

    Habitat fragmentation, i.e., fragment size and isolation, can differentially alter patterns of neutral and quantitative genetic variation, fitness and phenotypic plasticity of plant populations, but their effects have rarely been tested simultaneously. We assessed the combined effects of size and connectivity on these aspects of genetic and phenotypic variation in populations of Centaurea hyssopifolia, a narrow endemic gypsophile that previously showed performance differences associated with fragmentation. We grew 111 maternal families sampled from 10 populations that differed in their fragment size and connectivity in a common garden, and characterized quantitative genetic variation, phenotypic plasticity to drought for key functional traits, and plant survival, as a measure of population fitness. We also assessed neutral genetic variation within and among populations using eight microsatellite markers. Although C. hyssopifolia is a narrow endemic gypsophile, we found substantial neutral genetic variation and quantitative variation for key functional traits. The partition of genetic variance indicated that a higher proportion of variation was found within populations, which is also consistent with low population differentiation in molecular markers, functional traits and their plasticity. This, combined with the generally small effect of habitat fragmentation suggests that gene flow among populations is not restricted, despite large differences in fragment size and isolation. Importantly, population’s similarities in genetic variation and plasticity did not reflect the lower survival observed in isolated populations. Overall, our results indicate that, although the species consists of genetically variable populations able to express functional plasticity, such aspects of adaptive potential may not always reflect populations’ survival. Given the differential effects of habitat connectivity on functional traits, genetic variation and fitness, our study

  11. Catechol-O-methyltransferase (COMT) Genotype Affects Age-Related Changes in Plasticity in Working Memory: A Pilot Study

    PubMed Central

    Riemer, Thomas G.; Schulte, Stefanie; Onken, Johanna; Heinz, Andreas; Rapp, Michael A.

    2014-01-01

    Objectives. Recent work suggests that a genetic variation associated with increased dopamine metabolism in the prefrontal cortex (catechol-O-methyltransferase Val158Met; COMT) amplifies age-related changes in working memory performance. Research on younger adults indicates that the influence of dopamine-related genetic polymorphisms on working memory performance increases when testing the cognitive limits through training. To date, this has not been studied in older adults. Method. Here we investigate the effect of COMT genotype on plasticity in working memory in a sample of 14 younger (aged 24–30 years) and 25 older (aged 60–75 years) healthy adults. Participants underwent adaptive training in the n-back working memory task over 12 sessions under increasing difficulty conditions. Results. Both younger and older adults exhibited sizeable behavioral plasticity through training (P < .001), which was larger in younger as compared to older adults (P < .001). Age-related differences were qualified by an interaction with COMT genotype (P < .001), and this interaction was due to decreased behavioral plasticity in older adults carrying the Val/Val genotype, while there was no effect of genotype in younger adults. Discussion. Our findings indicate that age-related changes in plasticity in working memory are critically affected by genetic variation in prefrontal dopamine metabolism. PMID:24772423

  12. Mood dysregulation and affective instability in emerging adults with childhood maltreatment: An ecological momentary assessment study.

    PubMed

    Teicher, Martin H; Ohashi, Kyoko; Lowen, Steven B; Polcari, Ann; Fitzmaurice, Garrett M

    2015-11-01

    Childhood maltreatment increases risk for mood, anxiety, substance use and personality disorders and is associated with alterations in structure, function and connectivity of brain regions involved in emotional regulation. We sought to assess whether maltreatment was specifically associated with disturbances in positive or negative mood regulation. Ecological momentary ratings were collected with a wristwatch-like device with joy-stick (Seiko ecolog) approximately six times per day over a week in 60 unmedicated participants (22 control, 38 maltreated, 18-25 years old). Forty-five percent of maltreated subjects had a history of major depression but all were currently euthymic. Principal component analysis with varimax rotation was used to provide orthogonal measures of positive and negative valence, which were analyzed for indices of variability, circadian rhythmicity and persistence, using linear and non-linear hierarchical modeling and Hurst analysis. Groups did not differ in mean levels of positive or negative affect. Maltreated subjects had increased variability and circadian and hemicircadian abnormalities in ratings of positive but not negative affect. Conversely, they had higher estimated Hurst exponents for negative but not positive affect ratings indicating a greater degree of persistence. Abnormalities in variability, rhythmicity and persistence were present in both maltreated subjects with and without histories of major depression. These findings suggest that both positive and negative valence systems may be dysregulated in individuals with childhood maltreatment. However the nature of the dysregulation appears to differ fundamentally in these domains, as positive mood ratings were more variable and negative ratings more persistent.

  13. Osteoporosis affects both post-yield microdamage accumulation and plasticity degradation in vertebra of ovariectomized rats

    NASA Astrophysics Data System (ADS)

    Li, Siwei; Niu, Guodong; Dong, Neil X.; Wang, Xiaodu; Liu, Zhongjun; Song, Chunli; Leng, Huijie

    2017-04-01

    Estrogen withdrawal in postmenopausal women increases bone loss and bone fragility in the vertebra. Bone loss with osteoporosis not only reduces bone mineral density (BMD), but actually alters bone quality, which can be comprehensively represented by bone post-yield behaviors. This study aimed to provide some information as to how osteoporosis induced by estrogen depletion could influence the evolution of post-yield microdamage accumulation and plastic deformation in vertebral bodies. This study also tried to reveal the part of the mechanisms of how estrogen deficiency-induced osteoporosis would increase the bone fracture risk. A rat bilateral ovariectomy (OVX) model was used to induce osteoporosis. Progressive cyclic compression loading was developed for vertebra testing to elucidate the post-yield behaviors. BMD, bone volume fraction, stiffness degradation, and plastic deformation evolution were compared among rats raised for 5 weeks (ovx5w and sham5w groups) and 35 weeks (ovx35w and sham35w groups) after sham surgery and OVX. The results showed that a higher bone loss in vertebral bodies corresponded to lower stiffness and higher plastic deformation. Thus, osteoporosis could increase the vertebral fracture risk probably through microdamage accumulation and plastic deforming degradation.

  14. Osteoporosis affects both post-yield microdamage accumulation and plasticity degradation in vertebra of ovariectomized rats

    NASA Astrophysics Data System (ADS)

    Li, Siwei; Niu, Guodong; Dong, Neil X.; Wang, Xiaodu; Liu, Zhongjun; Song, Chunli; Leng, Huijie

    2017-03-01

    Estrogen withdrawal in postmenopausal women increases bone loss and bone fragility in the vertebra. Bone loss with osteoporosis not only reduces bone mineral density (BMD), but actually alters bone quality, which can be comprehensively represented by bone post-yield behaviors. This study aimed to provide some information as to how osteoporosis induced by estrogen depletion could influence the evolution of post-yield microdamage accumulation and plastic deformation in vertebral bodies. This study also tried to reveal the part of the mechanisms of how estrogen deficiency-induced osteoporosis would increase the bone fracture risk. A rat bilateral ovariectomy (OVX) model was used to induce osteoporosis. Progressive cyclic compression loading was developed for vertebra testing to elucidate the post-yield behaviors. BMD, bone volume fraction, stiffness degradation, and plastic deformation evolution were compared among rats raised for 5 weeks (ovx5w and sham5w groups) and 35 weeks (ovx35w and sham35w groups) after sham surgery and OVX. The results showed that a higher bone loss in vertebral bodies corresponded to lower stiffness and higher plastic deformation. Thus, osteoporosis could increase the vertebral fracture risk probably through microdamage accumulation and plastic deforming degradation.

  15. Identification of critical factors for the instability of permafrost-affected rockwalls in the Turtmann valley (Swiss Alps)

    NASA Astrophysics Data System (ADS)

    Messenzehl, Karoline; Draebing, Daniel; Dikau, Richard

    2014-05-01

    Rock slope instability, small-scale rockfalls and associated talus slopes are widespread phenomena in mountain environments. The heterogeneous spatial pattern, sediment properties and volume of talus deposits in alpine valleys reflect a complicated set of various variables governing the spatial and temporal occurrence of slope failure. However, the dynamic and non-linear interplay between environmental settings, the mechanical properties of the rock mass, its discontinuities and different weathering processes promoting rock degradation makes the identification of the dominant destabilizing factors a difficult task. In our project we studied the instability of permafrost-affected rockwalls (Nyenhuis et al., 2005) in the high alpine Turtmann Valley in the Swiss Alps (110 km2). Here, we present a combination of (i) meso-scale spatial analyses and (ii) local-scale geotechnical investigations of critical factors on rockwall instability and (iii) incorporate the results into a theoretical concept with respect to abiotic and biotic weathering processes. (i) To explain the spatial variability of talus deposits stored in 14 WE-oriented hanging valleys, a detailed geomorphological map of 220 talus slopes (Otto et al. 2009) was spatially combined with different key variables of the rockfall source area including topography, climate, lithology and rockwall morphometry. The talus slopes are strongly oriented towards north indicating reduced solar radiation. This aspect-driven trend appears to support the high significance of frost weathering processes as dominant mechanism for rock slope instability, in particular during thawing phases of rockwall permafrost. (ii) To assess the role of mechanical properties of rockwalls at local scales, field surveys of rock discontinuities were performed at selected rockwalls with and without talus slopes based on ISRM standards. Geotechnical investigations reveal discontinuity orientations and spacings that might effectively promote rock

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

    SciTech Connect

    Hsiung, L; Zhou, J

    2005-12-06

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

  17. A test of the empirical network surrounding affective instability and the degree to which it is independent from neuroticism.

    PubMed

    Maples, Jessica; Miller, Joshua D; Hoffman, Brian J; Johnson, Sheri L

    2014-07-01

    Affective instability (AI) is as a central component of a number of psychiatric disorders, but it has received relatively little empirical attention as an individual construct. The goal of the current study was to study AI in the context of a broad empirical network of relevant constructs and compare its pattern of relations with those generated by trait neuroticism, both of which were assessed using both self- and informant reports. In a sample of 343 college students, the present study examined the correlations generated by an AI factor (derived from a factor analysis of relevant scales) in comparison to neuroticism in relation to personality and etiological and outcome variables. An exploratory factor analysis revealed a one-factor structure of AI related to the experience of intense and changeable negative affect and subsequent physical and behavioral consequences. The correlations generated by self- and informant reports of AI with these external criteria were almost perfectly correlated with the correlations demonstrated by self- and informant reports of neuroticism. Self- and informant reports of AI generated a pattern of results consistent with its role in a number of psychological disorders that are associated with substantial impairment. The current data suggest that AI might be best conceived of as largely overlapping with neuroticism rather than as a distinct construct.

  18. Concentration of plasticizers applied during heat-moisture treatment affects properties of the modified canna starch.

    PubMed

    Juansang, Juraluck; Puncha-Arnon, Santhanee; Uttapap, Dudsadee; Puttanlek, Chureerat; Rungsardthong, Vilai; Watcharatewinkul, Yanika

    2017-04-15

    Effects of the concentration of plasticizers applied during heat-moisture treatment (HMT) on the properties of canna starch were investigated. The modified starches were prepared by soaking starch in 0 (water), 1, 3, 5, 10, 20 and 30% w/w glycerol or sorbitol solution for 24h and adjusting the moisture content to 25% before HMT (100°C, 1h). Changes in the pasting profiles of heat-moisture treated starches were more obvious when glycerol solutions were used instead of water. An increase in the concentration of glycerol solution from 1% to 5% resulted in a progressive decrease in paste viscosity; paste viscosity then increased as the glycerol concentration rose from 10 to 30%. A similar trend was observed when sorbitol was used as a plasticizer, but with a lesser effect. A scheme for arrangements of the molecular structure of starch during the process of HMT was suggested.

  19. Dietary cholesterol concentration affects synaptic plasticity and dendrite spine morphology of rabbit hippocampal neurons.

    PubMed

    Wang, Desheng; Zheng, Wen

    2015-10-05

    Previous studies have shown dietary cholesterol can enhance learning but retard memory which may be partly due to increased cholesterol levels in hippocampus and reduced afterhyperpolarization (AHP) amplitude of hippocampal CA1 neurons. This study explored the dose-dependent effect of dietary cholesterol on synaptic plasticity of rabbit hippocampal CA1 neurons and spine morphology, the postsynaptic structures responsible for synaptic plasticity. Field potential recordings revealed a low concentration of dietary cholesterol increased long-term potentiation (LTP) expression while high concentrations produced a pronounced reduction in LTP expression. Dietary cholesterol facilitated basal synaptic transmission but did not influence presynaptic function. DiI staining showed dietary cholesterol induced alterations in dendrite spine morphology characterized by increased mushroom spine density and decreased thin spine density, two kinds of dendritic spines that may be linked to memory consolidation and learning acquisition. Dietary cholesterol also modulated the geometric measures of mushroom spines. Therefore, dietary cholesterol dose-dependently modulated both synaptic plasticity and dendrite spine morphologies of hippocampal CA1 neurons that could mediate learning and memory changes previously seen to result from feeding a cholesterol diet.

  20. Thermal developmental plasticity affects body size and water conservation of Drosophila nepalensis from the Western Himalayas.

    PubMed

    Parkash, R; Lambhod, C; Singh, D

    2014-08-01

    In the Western Himalayas, Drosophila nepalensis is more abundant during the colder and drier winter than the warmer rainy season but the mechanistic bases of such adaptations are largely unknown. We tested effects of developmental plasticity on desiccation-related traits (body size, body melanization and water balance traits) that may be consistent with changes in seasonal abundance of this species. D. nepalensis grown at 15°C has shown twofold higher body size, greater melanization (∼15-fold), higher desiccation resistance (∼55 h), hemolymph as well as carbohydrate content (twofold higher) as compared with corresponding values at 25°C. Water loss before succumbing to death was much higher (∼16%) at 15°C than 25°C. Developmental plastic effects on body size are associated with changes in water balance-related traits (bulk water, hemolymph and dehydration tolerance). The role of body melanization was evident from the analysis of assorted darker and lighter flies (from a mass culture of D. nepalensis reared at 21°C) which lacked differences in dry mass but showed differences in desiccation survival hours and rate of water loss. For adult acclimation, we found a slight increase in desiccation resistance of flies reared at lower growth temperature, whereas in flies reared at 25°C such a response was lacking. In D. nepalensis, greater developmental plasticity is consistent with its contrasting levels of seasonal abundance. Finally, in the context of global climate change in the Western Himalayas, D. nepalensis seems vulnerable in the warmer season due to lower adult as well as developmental acclimation potential at higher growth temperature (25°C).

  1. 40 CFR 63.5795 - How do I know if my reinforced plastic composites production facility is a new affected source or...

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... composites production facility is a new affected source or an existing affected source? 63.5795 Section 63...) NATIONAL EMISSION STANDARDS FOR HAZARDOUS AIR POLLUTANTS FOR SOURCE CATEGORIES National Emissions Standards....5795 How do I know if my reinforced plastic composites production facility is a new affected source or...

  2. Four Weeks of Balance Training does not Affect Ankle Joint Stiffness in Subjects with Unilateral Chronic Ankle Instability

    PubMed Central

    Jain, Tarang Kumar; Wauneka, Clayton N.; Liu, Wen

    2016-01-01

    Background Balance training has been shown to be effective in preventing ankle sprain recurrences in subjects with chronic ankle instability (CAI) but the biomechanical pathways underlying the clinical outcomes are still unknown. This study was conducted to determine if a 4-week balance training intervention can alter the mechanical characteristics in ankles with CAI. Methods Twenty-two recreationally active subjects with unilateral CAI were randomized to either a control (n = 11, 35.1 ± 9.3 years) or intervention (n = 11, 33.5 ± 6.6 years) group. Subjects in the intervention group were trained on the affected limb with static and dynamic components using a Biodex balance stability system for 4-weeks. The ankle joint stiffness and neutral zone in inversion and eversion directions on the involved and uninvolved limbs was measured at baseline and post-intervention using a dynamometer. Results At baseline, the mean values of the inversion stiffness (0.69 ± 0.37 Nm/degree) in the involved ankle was significantly lower (p < 0.011, 95% CI [0.563, 0.544]) than that of uninvolved contralateral ankle (0.99 ± 0.41 Nm/degree). With the available sample size, the eversion stiffness, inversion neutral zone, and eversion neutral zone were not found to be significantly different between the involved and uninvolved contralateral ankles. The 4-week balance training intervention failed to show any significant effect on the passive ankle stiffness and neutral zones in inversion and eversion. Conclusion Decreased inversion stiffness in the involved chronic unstable ankle was found that of uninvolved contralateral ankle. The 4-week balance training program intervention was ineffective in altering the mechanical characteristics of ankles with CAI. Level of evidence Randomized controlled clinical trial; Level of evidence, 1. PMID:27642647

  3. Factors affecting the efficiency of aerosol therapy with pressurised metered-dose inhalers through plastic spacers.

    PubMed

    Chuffart, A A; Sennhauser, F H; Wildhaber, J H

    2001-01-12

    The main objective of this study was to compare the in vitro delivery of salbutamol from a chlorofluorocarbon(CFC)-propelled pressurised metered-dose inhaler (pMDI) versus a newly developed hydrofluoroalkane(HFA)-propelled pMDI through various spacers. In addition, we aimed to study the effect on bronchodilator response when using an optimal pMDI/spacer combination for aerosol delivery compared to a suboptimal combination. Particle size distribution and output from salbutamol pMDIs containing either CFC propellants (Ventolin) or HFA propellants (Airomir) were measured using a multistage liquid impinger (MSLI) and compared to that through both detergent-coated (non-static) or untreated (static) large volume (Nebuhaler, Volumatic) and small volume (Aerochamber) plastic spacers. Flow-volume curves (FEV1) were obtained from twelve asthmatic children with known significant bronchodilator response (8 males), aged 13-17 years, randomly inhaling salbutamol from a CFC-pMDI through a static spacer (Nebuhaler) and from an HFA-pMDI through a non-static spacer (Nebuhaler). In vitro output of particles in the respirable range (< 6.8 microns) from HFA-pMDIs was significantly higher than that from CFC-pMDIs using various spacers. Removal of electrostatic charge increased output from CFC- and HFA-pMDIs through all spacers by 17-82%. The mean (SD) bronchodilator response after inhalation of salbutamol from a CFC-pMDI through a static spacer was 7.1% (6.3%) compared to 17.5% (7.9%) after inhalation from an HFA-pMDI through a non-static spacer (p = 0.002). Use of a newly developed HFA-propelled pMDI greatly improves drug delivery through spacers compared to a CFC-propelled pMDI. However, electrostatic charge in plastic spacers remains the key determinant limiting delivery of salbutamol from a pMDI through spacers, and can be reduced by soaking the spacer in a household detergent. Using an optimal pMDI/spacer combination leads to a significantly improved bronchodilator response.

  4. Bacterial Genome Instability

    PubMed Central

    Darmon, Elise

    2014-01-01

    SUMMARY Bacterial genomes are remarkably stable from one generation to the next but are plastic on an evolutionary time scale, substantially shaped by horizontal gene transfer, genome rearrangement, and the activities of mobile DNA elements. This implies the existence of a delicate balance between the maintenance of genome stability and the tolerance of genome instability. In this review, we describe the specialized genetic elements and the endogenous processes that contribute to genome instability. We then discuss the consequences of genome instability at the physiological level, where cells have harnessed instability to mediate phase and antigenic variation, and at the evolutionary level, where horizontal gene transfer has played an important role. Indeed, this ability to share DNA sequences has played a major part in the evolution of life on Earth. The evolutionary plasticity of bacterial genomes, coupled with the vast numbers of bacteria on the planet, substantially limits our ability to control disease. PMID:24600039

  5. Plasticity-Related Gene 1 Affects Mouse Barrel Cortex Function via Strengthening of Glutamatergic Thalamocortical Transmission.

    PubMed

    Unichenko, Petr; Kirischuk, Sergei; Yang, Jenq-Wei; Baumgart, Jan; Roskoden, Thomas; Schneider, Patrick; Sommer, Angela; Horta, Guilherme; Radyushkin, Konstantin; Nitsch, Robert; Vogt, Johannes; Luhmann, Heiko J

    2016-07-01

    Plasticity-related gene-1 (PRG-1) is a brain-specific protein that modulates glutamatergic synaptic transmission. Here we investigated the functional role of PRG-1 in adolescent and adult mouse barrel cortex both in vitro and in vivo. Compared with wild-type (WT) animals, PRG-1-deficient (KO) mice showed specific behavioral deficits in tests assessing sensorimotor integration and whisker-based sensory discrimination as shown in the beam balance/walking test and sandpaper tactile discrimination test, respectively. At P25-31, spontaneous network activity in the barrel cortex in vivo was higher in KO mice compared with WT littermates, but not at P16-19. At P16-19, sensory evoked cortical responses in vivo elicited by single whisker stimulation were comparable in KO and WT mice. In contrast, at P25-31 evoked responses were smaller in amplitude and longer in duration in WT animals, whereas KO mice revealed no such developmental changes. In thalamocortical slices from KO mice, spontaneous activity was increased already at P16-19, and glutamatergic thalamocortical inputs to Layer 4 spiny stellate neurons were potentiated. We conclude that genetic ablation of PRG-1 modulates already at P16-19 spontaneous and evoked excitability of the barrel cortex, including enhancement of thalamocortical glutamatergic inputs to Layer 4, which distorts sensory processing in adulthood.

  6. How does visual language affect crossmodal plasticity and cochlear implant success?

    PubMed Central

    Lyness, C.R.; Woll, B.; Campbell, R.; Cardin, V.

    2013-01-01

    Cochlear implants (CI) are the most successful intervention for ameliorating hearing loss in severely or profoundly deaf children. Despite this, educational performance in children with CI continues to lag behind their hearing peers. From animal models and human neuroimaging studies it has been proposed the integrative functions of auditory cortex are compromised by crossmodal plasticity. This has been argued to result partly from the use of a visual language. Here we argue that ‘cochlear implant sensitive periods’ comprise both auditory and language sensitive periods, and thus cannot be fully described with animal models. Despite prevailing assumptions, there is no evidence to link the use of a visual language to poorer CI outcome. Crossmodal reorganisation of auditory cortex occurs regardless of compensatory strategies, such as sign language, used by the deaf person. In contrast, language deprivation during early sensitive periods has been repeatedly linked to poor language outcomes. Language sensitive periods have largely been ignored when considering variation in CI outcome, leading to ill-founded recommendations concerning visual language in CI habilitation. PMID:23999083

  7. Discussion of Developmental Plasticity: Factors Affecting Cognitive Outcome after Pediatric Traumatic Brain Injury.

    ERIC Educational Resources Information Center

    Chapman, Sandra Bond; McKinnon, Lyn

    2000-01-01

    This article discusses psychobiological factors that affect recovery after traumatic brain injury in children and adolescents, including biological pathophysiology of the injury, the cognitive stage of the child at injury, the amount of time after injury, the challenge level of tasks, and the child's reserve of psychosocial resources. (Contains…

  8. Vibrational modes as a predictor for plasticity in a model glass

    NASA Astrophysics Data System (ADS)

    Tanguy, A.; Mantisi, B.; Tsamados, M.

    2010-04-01

    The density of vibrational states in amorphous materials is known to present an unusual shape related as "boson peak", and responsible for the very specific thermal behaviour of these systems. In this letter, we show how the vibrational modes of a model Lennard-Jones glass are affected by a mechanical load. Far from a mechanical instability, vibrational modes can be described at low frequency by weak scattering of acoustic modes. Close to a plastic instability, some of them localize. We show how the shape of the "localized" vibrational modes, juste before the plastic instability, is directly related to the spatial organization of the plastic rearrangements. A measurement of the spatial organization of the low-frequency vibrational modes could thus be used as a predictor for plastic activity.

  9. Factors Affecting the Plasticity of Sodium Chloride, Lithium Fluoride, and Magnesium Oxide Single Crystals. 1

    NASA Technical Reports Server (NTRS)

    Stearns, Carl A.; Pack, Ann E.; Lad, Robert A.

    1959-01-01

    A study was made of the relative magnitude of the effects of various factors on the ductility of single crystals of sodium chloride (NaCl), lithium fluoride (LiF), and magnesium oxide (MgO). Specimen treatments included water-polishing, varying cleavage rate, annealing, quenching, X-irradiation, surface coating, aging, and combinations of some of these treatments. The mechanical behavior of the crystals was studied in flexure and in compression, the latter study being performed at both constant strain rate and constant load. Etch-pit studies were carried out to provide some pertinent information on the results of pretreatment on the dislocation concentration and distribution in the vicinity of the surface. The load deformation curves for these ionic single crystals show an initial region of very low slope which proved to be due to anelastic deformation. The extent of initial anelastic deformation is modified by specimen pretreatment in a way that suggests that this deformation is the result of expansion of cleaved-in dislocation loops, which can contract on the removal of the stress. The effects of the various pretreatments on the load and deflection at fracture are in accord with the prediction one might make with regard to their effect on the nucleation of fatal surface cracks. For NaCl, increases in ductility are always accompanied by increases in strength. The creep constants for NaCl are a function of treatments which affect the bulk structure but are not a function of treatments which only affect the surface.

  10. Mechanisms of Plastic and Fracture Instabilities for Alloy Development of Fusion Materials. Final Project Report for period July 15, 1998 - July 14, 2003

    SciTech Connect

    Ghoniem, N. M.

    2003-07-14

    The main objective of this research was to develop new computational tools for the simulation and analysis of plasticity and fracture mechanisms of fusion materials, and to assist in planning and assessment of corresponding radiation experiments.

  11. Morphological Study: Ultrastructural Aspects of Articular Cartilage and Subchondral Bone in Patients Affected by Post-Traumatic Shoulder Instability.

    PubMed

    Baudi, Paolo; Catani, Fabio; Rebuzzi, Manuela; Ferretti, Marzia; Smargiassi, Alberto; Campochiaro, Gabriele; Serafini, Fabio; Palumbo, Carla

    2016-12-16

    Post-traumatic shoulder instability is a frequent condition in active population, representing one of most disabling pathologies, due to altered balance involving joints. No data are so far available on early ultrastructural osteo-chondral damages, associated with the onset of invalidating pathologies, like osteoarthritis-OA. Biopsies of glenoid articular cartilage and sub-chondral bone were taken from 10 adult patients underwent arthroscopic stabilization. Observations were performed under Transmission Electron Microscopy-TEM in tangential, arcuate and radial layers of the articular cartilage and in the sub-chondral bone. In tangential and arcuate layers chondrocytes display normal and very well preserved ultrastructure, probably due to the synovial liquid supply; otherwise, throughout the radial layer (un-calcified and calcified) chondrocytes show various degrees of degeneration; occasionally, in the radial layer evidences of apoptosis/autophagy were also observed. Concerning sub-chondral bone, osteocytes next to the calcified cartilage also show signs of degeneration, while osteocytes farther from the osteo-chondral border display normal ultrastructure, probably due to the bone vascular supply. The ultrastructural features of the osteo-chondral complex are not age-dependent. This study represents the first complete ultrastructural investigation of the articular osteo-chondral complex in shoulder instability, evaluating the state of preservation/viability of both chondrocytes and osteocytes throughout the successive layers of articular cartilage and sub-chondral bone. Preliminary observations here collected represent the morphological basis for further deepening of pathogenesis related to shoulder instability, enhancing the relationship between cell shape and microenvironment; in particular, they could be useful in understanding if the early surgical treatment in shoulder instability could avoid the onset of OA. Anat Rec, 300:12-15, 2017. © 2016 Wiley

  12. The plasticizer bisphenol A affects somatic and sexual development, but differently in pipid, hylid and bufonid anurans.

    PubMed

    Tamschick, Stephanie; Rozenblut-Kościsty, Beata; Ogielska, Maria; Kekenj, David; Gajewski, Franz; Krüger, Angela; Kloas, Werner; Stöck, Matthias

    2016-09-01

    Due to their terrestrial habitats and aquatic reproduction, many amphibians are both very vulnerable and highly suitable bioindicators. The plasticizer bisphenol A (BPA) is one of the most produced chemical substances worldwide, and knowledge on its impacts on humans and animals is mounting. BPA is used for the industrial production of polycarbonate plastics and epoxy resins and found in a multitude of consumer products. Studies on BPA have involved mammals, fish and the fully aquatic anuran model Xenopus laevis. However, our knowledge about the sexual development of non-model, often semi-terrestrial anuran amphibians remains poor. Using a recently developed experimental design, we simultaneously applied BPA to two non-model species (Hyla arborea, Hylidae; Bufo viridis, Bufonidae) and the model X. laevis (Pipidae), compared their genetic and phenotypic sex for detection of sex reversals, and studied sexual development, focusing on anatomical and histological features of gonads. We compared three concentrations of BPA (0.023, 2.28 and 228 μg/L) to control groups in a high-standard flow-through-system, and tested whether conclusions, drawn from the model species, can be extrapolated to non-model anurans. In contrast to previous studies on fish and Xenopus, often involving dosages much higher than most environmental pollution data, we show that BPA causes neither the development of mixed sex nor of sex-reversed individuals (few, seemingly BPA-independent sex reversals) in all focal species. However, environmentally relevant concentrations, as low as 0.023 μg/L, were sufficient to provoke species-specific anatomically and histologically detectable impairments of gonads, and affected morphological traits of metamorphs. As the intensity of these effects differed between the three species, our data imply that BPA diversely affects amphibians with different evolutionary history, sex determination systems and larval ecologies. These results highlight the role of

  13. Extrinsic visual feedback and additional cognitive/physical demands affect single-limb balance control in individuals with ankle instability

    PubMed Central

    Hung, You-jou; Miller, Jacob

    2016-01-01

    AIM To investigate the impact of extrinsic visual feedback and additional cognitive/physical demands on single-limb balance in individuals with ankle instability. METHODS Sixteen subjects with ankle instability participated in the study. Ankle instability was identified using the Cumberland Ankle Instability Tool (CAIT). The subject’s unstable ankle was examined using the Athletic Single Leg Stability Test of the Biodex Balance System with 4 different protocols: (1) default setting with extrinsic visual feedback from the monitor; (2) no extrinsic visual feedback; (3) no extrinsic visual feedback with cognitive demands; and (4) no extrinsic visual feedback with physical demands. For the protocol with added cognitive demands, subjects were asked to continue subtracting 7 from a given number while performing the same test without extrinsic visual feedback. For the protocol with added physical demands, subjects were asked to pass and catch a basketball to and from the examiner while performing the same modified test. RESULTS The subject’s single-limb postural control varied significantly among different testing protocols (F = 103; P = 0.000). Subjects’ postural control was the worst with added physical demands and the best with the default condition with extrinsic visual feedback. Pairwise comparison shows subjects performed significantly worse in all modified protocols (P < 0.01 in all comparisons) compared to the default protocol. Results from all 4 protocols are significantly different from each other (P < 0.01) except for the comparison between the “no extrinsic visual feedback” and “no extrinsic visual feedback with cognitive demands” protocols. Comparing conditions without extrinsic visual feedback, adding a cognitive demand did not significantly compromise single-limb balance control but adding a physical demand did. Scores from the default protocol are significantly correlated with the results from all 3 modified protocols: No extrinsic visual

  14. Inflammation affects the viability and plasticity of equine mesenchymal stem cells: possible implications in intra-articular treatments

    PubMed Central

    Barrachina, Laura; Remacha, Ana Rosa; Romero, Antonio; Vázquez, Francisco José; Albareda, Jorge; Prades, Marta; Ranera, Beatriz; Zaragoza, Pilar; Martín-Burriel, Inmaculada

    2017-01-01

    Mesenchymal stem cells (MSCs) are gaining relevance for treating equine joint injuries because of their ability to limit inflammation and stimulate regeneration. Because inflammation activates MSC immunoregulatory function, proinflammatory priming could improve MSC efficacy. However, inflammatory molecules present in synovial fluid or added to the culture medium might have deleterious effects on MSCs. Therefore, this study was conducted to investigate the effects of inflammatory synovial fluid and proinflammatory cytokines priming on viability and plasticity of equine MSCs. Equine bone marrow derived MSCs (eBM-MSCs) from three animals were cultured for 72 h in media supplemented with: 20% inflammatory synovial fluid (SF); 50 ng/mL IFN-γ and TNF-α (CK50); and 20 ng/mL IFN-γ and TNF-α (CK20). Proliferation assay and expression of proliferation and apoptosis-related genes showed that SF exposed-eBM-MSCs maintained their viability, whereas the viability of CK primed-eBM-MSCs was significantly impaired. Tri-lineage differentiation assay revealed that exposure to inflammatory synovial fluid did not alter eBM-MSCs differentiation potential; however, eBM-MSCs primed with cytokines did not display osteogenic, adipogenic or chondrogenic phenotype. The inflammatory synovial environment is well tolerated by eBM-MSCs, whereas cytokine priming negatively affects the viability and differentiation abilities of eBM-MSCs, which might limit their in vivo efficacy. PMID:27297420

  15. Sex Differences in Phenotypic Plasticity Affect Variation in Sexual Size Dimorphism in Insects: From Physiology to Evolution

    PubMed Central

    Stillwell, R. Craig; Blanckenhorn, Wolf U.; Teder, Tiit; Davidowitz, Goggy; Fox, Charles W.

    2015-01-01

    Males and females of nearly all animals differ in their body size, a phenomenon called sexual size dimorphism (SSD). The degree and direction of SSD vary considerably among taxa, including among populations within species. A considerable amount of this variation is due to sex differences in body size plasticity. We examine how variation in these sex differences is generated by exploring sex differences in plasticity in growth rate and development time and the physiological regulation of these differences (e.g., sex differences in regulation by the endocrine system). We explore adaptive hypotheses proposed to explain sex differences in plasticity, including those that predict that plasticity will be lowest for traits under strong selection (adaptive canalization) or greatest for traits under strong directional selection (condition dependence), but few studies have tested these hypotheses. Studies that combine proximate and ultimate mechanisms offer great promise for understanding variation in SSD and sex differences in body size plasticity in insects. PMID:19728836

  16. Prenatal Hypoxia in Different Periods of Embryogenesis Differentially Affects Cell Migration, Neuronal Plasticity, and Rat Behavior in Postnatal Ontogenesis

    PubMed Central

    Vasilev, Dmitrii S.; Dubrovskaya, Nadezhda M.; Tumanova, Natalia L.; Zhuravin, Igor A.

    2016-01-01

    cortical cytoarchitecture, neuronal plasticity and behavior in postnatal ontogenesis which testify to cortical dysfunction. Hypoxia on E18 does not significantly affect cortical structure and parietal cortex-dependent behavioral tasks. PMID:27065788

  17. Inducible offences affect predator-prey interactions and life-history plasticity in both predators and prey.

    PubMed

    Kishida, Osamu; Costa, Zacharia; Tezuka, Ayumi; Michimae, Hirofumi

    2014-07-01

    Phenotypic plasticity can have strong impacts on predator-prey interactions. Although much work has examined the effects of inducible defences, less understood is how inducible offences in predators affect predator-prey interactions and predator and prey phenotypes. Here, we examine the impacts of an inducible offence on the interactions and life histories of a cohort of predatory Hynobius retardatus salamander larvae and their prey, Rana pirica tadpoles. We examined larval (duration, survival) and post-metamorphic (size) traits of both species after manipulating the presence/absence of tadpoles and salamanders with offensive (broadened gape width) or non-offensive phenotypes in pond enclosures. Offensive phenotype salamanders reduced tadpole survival and metamorph emergence by 58% compared to tadpole-only treatments, and by over 30% compared to non-offensive phenotypes. Average time to metamorphosis of frogs was delayed by 30% in the presence of salamanders, although this was independent of salamander phenotype. Thus, offensive phenotype salamanders reduced the number of tadpoles remaining in the pond over time by reducing tadpole survival, not by altering patterns of metamorph emergence. Offensive phenotypes also caused tadpoles to metamorphose 19% larger than no salamander treatments and 6% larger than non-offensive phenotype treatments. Pooled across salamander treatments, tadpoles caused salamanders to reach metamorphosis faster and larger. Moreover, in the presence of tadpoles, offensive phenotype salamanders metamorphosed 25% faster and 5% larger than non-offensive phenotype salamanders, but in their absence, neither their size nor larval period differed from non-offensive phenotype individuals. To our knowledge, this study is the first to demonstrate that inducible offences in predators can have strong impacts on predator and prey phenotypes across multiple life stages. Since early metamorphosis at a larger size has potential fitness advantages, the impacts

  18. Parent-of-origin genetic background affects the transcriptional levels of circadian and neuronal plasticity genes following sleep loss.

    PubMed

    Tinarelli, Federico; Garcia-Garcia, Celina; Nicassio, Francesco; Tucci, Valter

    2014-03-05

    Sleep homoeostasis refers to a process in which the propensity to sleep increases as wakefulness progresses and decreases as sleep progresses. Sleep is tightly organized around the circadian clock and is regulated by genetic and epigenetic mechanisms. The homoeostatic response of sleep, which is classically triggered by sleep deprivation, is generally measured as a rebound effect of electrophysiological measures, for example delta sleep. However, more recently, gene expression changes following sleep loss have been investigated as biomarkers of sleep homoeostasis. The genetic background of an individual may affect this sleep-dependent gene expression phenotype. In this study, we investigated whether parental genetic background differentially modulates the expression of genes following sleep loss. We tested the progeny of reciprocal crosses of AKR/J and DBA/2J mouse strains and we show a parent-of-origin effect on the expression of circadian, sleep and neuronal plasticity genes following sleep deprivation. Thus, we further explored, by in silico, specific functions or upstream mechanisms of regulation and we observed that several upstream mechanisms involving signalling pathways (i.e. DICER1, PKA), growth factors (CSF3 and BDNF) and transcriptional regulators (EGR2 and ELK4) may be differentially modulated by parental effects. This is the first report showing that a behavioural manipulation (e.g. sleep deprivation) in adult animals triggers specific gene expression responses according to parent-of-origin genomic mechanisms. Our study suggests that the same mechanism may be extended to other behavioural domains and that the investigation of gene expression following experimental manipulations should take seriously into account parent-of-origin effects.

  19. Parent-of-origin genetic background affects the transcriptional levels of circadian and neuronal plasticity genes following sleep loss

    PubMed Central

    Tinarelli, Federico; Garcia-Garcia, Celina; Nicassio, Francesco; Tucci, Valter

    2014-01-01

    Sleep homoeostasis refers to a process in which the propensity to sleep increases as wakefulness progresses and decreases as sleep progresses. Sleep is tightly organized around the circadian clock and is regulated by genetic and epigenetic mechanisms. The homoeostatic response of sleep, which is classically triggered by sleep deprivation, is generally measured as a rebound effect of electrophysiological measures, for example delta sleep. However, more recently, gene expression changes following sleep loss have been investigated as biomarkers of sleep homoeostasis. The genetic background of an individual may affect this sleep-dependent gene expression phenotype. In this study, we investigated whether parental genetic background differentially modulates the expression of genes following sleep loss. We tested the progeny of reciprocal crosses of AKR/J and DBA/2J mouse strains and we show a parent-of-origin effect on the expression of circadian, sleep and neuronal plasticity genes following sleep deprivation. Thus, we further explored, by in silico, specific functions or upstream mechanisms of regulation and we observed that several upstream mechanisms involving signalling pathways (i.e. DICER1, PKA), growth factors (CSF3 and BDNF) and transcriptional regulators (EGR2 and ELK4) may be differentially modulated by parental effects. This is the first report showing that a behavioural manipulation (e.g. sleep deprivation) in adult animals triggers specific gene expression responses according to parent-of-origin genomic mechanisms. Our study suggests that the same mechanism may be extended to other behavioural domains and that the investigation of gene expression following experimental manipulations should take seriously into account parent-of-origin effects. PMID:24446504

  20. Can high pressure I-II transitions in semiconductors be affected by plastic flow and nanocrystal precipitation in phase I?

    NASA Astrophysics Data System (ADS)

    Weinstein, B. A.; Lindberg, G. P.

    Pressure-Raman spectroscopy in ZnSe and ZnTe single crystals reveals that Se and Te nano-crystals (NCs) precipitate in these II-VI hosts for pressures far below their I-II phase transitions. The inclusions are evident from the appearance and negative pressure-shift of the A1 Raman peaks of Se and Te (trigonal phase). The Se and Te NCs nucleate at dislocations and grain boundaries that arise from pressure-induced plastic flow. This produces chemical and structural inhomogeneities in the zincblende phase of the host. At substantially higher pressures, the I-II transition proceeds in the presence of these inhomogenities. This can affect the transition's onset pressure Pt and width ΔPt, and the occurrence of metastable phases along the transition path. Precipitation models in metals show that nucleation of inclusions depends on the Peierls stress τp and a parameter α related to the net free energy gained on nucleation. For favorable values of τp and α, NC precipitation at pressures below the I-II transition could occur in other compounds. We propose criteria to judge whether this is likely based on the observed ranges of τp in the hosts, and estimates of α derived from the cohesive energy densities of the NC materials. One finds trends that can serve as a useful guide, both to test the proposed criteria, and to decide when closer scrutiny of phase transition experiments is warranted, e.g., in powders where high dislocation densities are initially created

  1. [Investigation and analysis of factors that affect the health of children in the plastic recycling and regeneration processing region].

    PubMed

    Wang, Juanli; Li, Liping; Lu, Yaogui

    2014-09-01

    To investigate the main influential factors for the health of children in the plastic waste recovery and recycling area. A cross-sectional survey was performed among children aged 9∼17 years from three natural villages engaged in plastic waste recovery and recycling and four control villages engaged in planting. The health status of children was investigated by random household survey using a face-to-face questionnaire, and the main influential factors were analyzed accordingly. The incidence rates of respiratory symptoms (cough and expectoration, nasal congestion, and sore throat) (78.4%, 69/88) and digestive diseases (gastrointestinal disease and liver disease) (14.8%, 13/88) in the waste processing area were significantly higher than those in the control area (64.0%, 71/111; 6.3%, 7/111) (P < 0.05). Multivariate logistic regression analysis indicated that skin diseases are related to whether plastic can be smelt around the residential area.

  2. Metaplasticity and behavior: how training and inflammation affect plastic potential within the spinal cord and recovery after injury

    PubMed Central

    Grau, James W.; Huie, J. Russell; Lee, Kuan H.; Hoy, Kevin C.; Huang, Yung-Jen; Turtle, Joel D.; Strain, Misty M.; Baumbauer, Kyle M.; Miranda, Rajesh M.; Hook, Michelle A.; Ferguson, Adam R.; Garraway, Sandra M.

    2014-01-01

    Research has shown that spinal circuits have the capacity to adapt in response to training, nociceptive stimulation and peripheral inflammation. These changes in neural function are mediated by physiological and neurochemical systems analogous to those that support plasticity within the hippocampus (e.g., long-term potentiation and the NMDA receptor). As observed in the hippocampus, engaging spinal circuits can have a lasting impact on plastic potential, enabling or inhibiting the capacity to learn. These effects are related to the concept of metaplasticity. Behavioral paradigms are described that induce metaplastic effects within the spinal cord. Uncontrollable/unpredictable stimulation, and peripheral inflammation, induce a form of maladaptive plasticity that inhibits spinal learning. Conversely, exposure to controllable or predictable stimulation engages a form of adaptive plasticity that counters these maladaptive effects and enables learning. Adaptive plasticity is tied to an up-regulation of brain derived neurotrophic factor (BDNF). Maladaptive plasticity is linked to processes that involve kappa opioids, the metabotropic glutamate (mGlu) receptor, glia, and the cytokine tumor necrosis factor (TNF). Uncontrollable nociceptive stimulation also impairs recovery after a spinal contusion injury and fosters the development of pain (allodynia). These adverse effects are related to an up-regulation of TNF and a down-regulation of BDNF and its receptor (TrkB). In the absence of injury, brain systems quell the sensitization of spinal circuits through descending serotonergic fibers and the serotonin 1A (5HT 1A) receptor. This protective effect is blocked by surgical anesthesia. Disconnected from the brain, intracellular Cl- concentrations increase (due to a down-regulation of the cotransporter KCC2), which causes GABA to have an excitatory effect. It is suggested that BDNF has a restorative effect because it up-regulates KCC2 and re-establishes GABA-mediated inhibition

  3. Plastic Hatching Timing by Red-Eyed Treefrog Embryos Interacts with Larval Predator Identity and Sublethal Predation to Affect Prey Morphology but Not Performance

    PubMed Central

    Touchon, Justin C.; Wojdak, Jeremy M.

    2014-01-01

    Many animals respond to predation risk by altering their morphology, behavior, or life-history. We know a great deal about the cues prey respond to and the changes to prey that can be induced by predation risk, but less is known about how plastic responses to predators may be affected by separate plastic responses occurring earlier in life, particularly during the embryonic period. Embryos of a broad array of taxa can respond to egg- or larval-stage risks by altering hatching timing, which may alter the way organisms respond to future predators. Using the red-eyed treefrog (Agalychnis callidryas), a model for understanding the effects of plasticity across life-stages, we assessed how the combined effects of induced variation in the timing of embryo hatching and variation in the larval predator community impacted tadpole morphology, pigmentation and swimming performance. We found that A. callidryas tadpoles developed deeper tail muscles and fins and darker pigmentation in response to fish predators, either when alone or in diverse community with other predators. Tadpoles altered morphology much less so to dragonfly naiads or water bugs. Interestingly, morphological responses to predators were also affected by induced differences in hatching age, with early and late-hatched tadpoles exhibiting different allometric relationships between tail height and body length in different predator environments. Beyond induced morphological changes, fish predators often damaged tadpoles’ tails without killing them (i.e., sublethal predation), but these tadpoles swam equally quickly to those with fully intact tails. This was due to the fact that tadpoles with more damaged tails increased tail beats to achieve equal swimming speed. This study demonstrates that plastic phenotypic responses to predation risk can be influenced by a complex combination of responses to both the embryo and larval environments, but also that prey performance can be highly resilient to sublethal predation

  4. Pentylenetetrazol-Induced Epileptiform Activity Affects Basal Synaptic Transmission and Short-Term Plasticity in Monosynaptic Connections

    PubMed Central

    Giachello, Carlo Natale Giuseppe; Premoselli, Federica; Montarolo, Pier Giorgio; Ghirardi, Mirella

    2013-01-01

    Epileptic activity is generally induced in experimental models by local application of epileptogenic drugs, including pentylenetetrazol (PTZ), widely used on both vertebrate and invertebrate neurons. Despite the high prevalence of this neurological disorder and the extensive research on it, the cellular and molecular mechanisms underlying epileptogenesis still remain unclear. In this work, we examined PTZ-induced neuronal changes in Helix monosynaptic circuits formed in vitro, as a simpler experimental model to investigate the effects of epileptiform activity on both basal release and post-tetanic potentiation (PTP), a form of short-term plasticity. We observed a significant enhancement of basal synaptic strength, with kinetics resembling those of previously described use-dependent forms of plasticity, determined by changes in estimated quantal parameters, such as the readily releasable pool and the release probability. Moreover, these neurons exhibited a strong reduction in PTP expression and in its decay time constant, suggesting an impairment in the dynamic reorganization of synaptic vesicle pools following prolonged stimulation of synaptic transmission. In order to explain this imbalance, we determined whether epileptic activity is related to the phosphorylation level of synapsin, which is known to modulate synaptic plasticity. Using western blot and immunocytochemical staining we found a PTZ-dependent increase in synapsin phosphorylation at both PKA/CaMKI/IV and MAPK/Erk sites, both of which are important for modulating synaptic plasticity. Taken together, our findings suggest that prolonged epileptiform activity leads to an increase in the synapsin phosphorylation status, thereby contributing to an alteration of synaptic strength in both basal condition and tetanus-induced potentiation. PMID:23437283

  5. Tensile Elastic Properties of Typical Stainless Steels and Nonferrous Metals as Affected by Plastic Deformation and by Heat Treatment

    NASA Technical Reports Server (NTRS)

    Mcadam, D J; Mebs, R W

    1940-01-01

    A general discussion is given of the relationships between stress, strain, and permanent set. From stress-set curves are derived proof stresses based on five different percentages of permanent set. The influence of prior plastic extension on these values is illustrated and discussed. A discussion is given of the influence of work-hardening, rest interval, and internal stress on the form of the proof stress-extension curve.

  6. Rotor internal friction instability

    NASA Technical Reports Server (NTRS)

    Bently, D. E.; Muszynska, A.

    1985-01-01

    Two aspects of internal friction affecting stability of rotating machines are discussed. The first role of internal friction consists of decreasing the level of effective damping during rotor subsynchronous and backward precessional vibrations caused by some other instability mechanisms. The second role of internal frication consists of creating rotor instability, i.e., causing self-excited subsynchronous vibrations. Experimental test results document both of these aspects.

  7. Collective instabilities

    SciTech Connect

    K.Y. Ng

    2003-08-25

    The lecture covers mainly Sections 2.VIII and 3.VII of the book ''Accelerator Physics'' by S.Y. Lee, plus mode-coupling instabilities and chromaticity-driven head-tail instability. Besides giving more detailed derivation of many equations, simple interpretations of many collective instabilities are included with the intention that the phenomena can be understood more easily without going into too much mathematics. The notations of Lee's book as well as the e{sup jwt} convention are followed.

  8. Ovarian cycle-linked plasticity of δ-GABAA receptor subunits in hippocampal interneurons affects γ oscillations in vivo

    PubMed Central

    Barth, Albert M. I.; Ferando, Isabella; Mody, Istvan

    2014-01-01

    GABAA receptors containing δ subunits (δ-GABAARs) are GABA-gated ion channels with extra- and perisynaptic localization, strong sensitivity to neurosteroids (NS), and a high degree of plasticity. In selective brain regions they are expressed on specific principal cells and interneurons (INs), and generate a tonic conductance that controls neuronal excitability and oscillations. Plasticity of δ-GABAARs in principal cells has been described during states of altered NS synthesis including acute stress, puberty, ovarian cycle, pregnancy and the postpartum period, with direct consequences on neuronal excitability and network dynamics. The defining network events implicated in cognitive function, memory formation and encoding are γ oscillations (30–120 Hz), a well-timed loop of excitation and inhibition between principal cells and PV-expressing INs (PV + INs). The δ-GABAARs of INs can modify γ oscillations, and a lower expression of δ-GABAARs on INs during pregnancy alters γ frequency recorded in vitro. The ovarian cycle is another physiological event with large fluctuations in NS levels and δ-GABAARs. Stages of the cycle are paralleled by swings in memory performance, cognitive function, and mood in both humans and rodents. Here we show δ-GABAARs changes during the mouse ovarian cycle in hippocampal cell types, with enhanced expression during diestrus in principal cells and specific INs. The plasticity of δ-GABAARs on PV-INs decreases the magnitude of γ oscillations continuously recorded in area CA1 throughout several days in vivo during diestrus and increases it during estrus. Such recurring changes in γ magnitude were not observed in non-cycling wild-type (WT) females, cycling females lacking δ-GABAARs only on PV-INs (PV-Gabrd-/-), and in male mice during a time course equivalent to the ovarian cycle. Our findings may explain the impaired memory and cognitive performance experienced by women with premenstrual syndrome (PMS) or premenstrual dysphoric

  9. Ovarian cycle-linked plasticity of δ-GABAA receptor subunits in hippocampal interneurons affects γ oscillations in vivo.

    PubMed

    Barth, Albert M I; Ferando, Isabella; Mody, Istvan

    2014-01-01

    GABAA receptors containing δ subunits (δ-GABAARs) are GABA-gated ion channels with extra- and perisynaptic localization, strong sensitivity to neurosteroids (NS), and a high degree of plasticity. In selective brain regions they are expressed on specific principal cells and interneurons (INs), and generate a tonic conductance that controls neuronal excitability and oscillations. Plasticity of δ-GABAARs in principal cells has been described during states of altered NS synthesis including acute stress, puberty, ovarian cycle, pregnancy and the postpartum period, with direct consequences on neuronal excitability and network dynamics. The defining network events implicated in cognitive function, memory formation and encoding are γ oscillations (30-120 Hz), a well-timed loop of excitation and inhibition between principal cells and PV-expressing INs (PV + INs). The δ-GABAARs of INs can modify γ oscillations, and a lower expression of δ-GABAARs on INs during pregnancy alters γ frequency recorded in vitro. The ovarian cycle is another physiological event with large fluctuations in NS levels and δ-GABAARs. Stages of the cycle are paralleled by swings in memory performance, cognitive function, and mood in both humans and rodents. Here we show δ-GABAARs changes during the mouse ovarian cycle in hippocampal cell types, with enhanced expression during diestrus in principal cells and specific INs. The plasticity of δ-GABAARs on PV-INs decreases the magnitude of γ oscillations continuously recorded in area CA1 throughout several days in vivo during diestrus and increases it during estrus. Such recurring changes in γ magnitude were not observed in non-cycling wild-type (WT) females, cycling females lacking δ-GABAARs only on PV-INs (PV-Gabrd (-/-)), and in male mice during a time course equivalent to the ovarian cycle. Our findings may explain the impaired memory and cognitive performance experienced by women with premenstrual syndrome (PMS) or premenstrual dysphoric

  10. [Intervertebral instability].

    PubMed

    Colaiacomo, M C; Tortora, A; Di Biasi, C; Polettini, E; Casciani, E; Gualdi, G F

    2009-01-01

    The clinic diagnosis of degenerative lumbar intervertebral instability is a controversial topic and have not yet been clarified clinical criteria for to define this condition with accuracy. Although the lumbar pain is the most common symptom in patients who have lumbar intervertebral instability its clinical presentation is not specific; moreover in patients with lumbar pain there are no agreed signs and symptoms that can be truly attributable to instability. Despite better imaging techniques of testing spinal instability there is not a clear relations between radiologic signs of instability and clinical symptoms. It is, however, still far from unanimous definition of degenerative lumbar intervertebral instability accepted from all specialists involved in diagnosis and treatment of this condition; however, seem there is most agree about suspected vertebral instability. Nevertheless this unresolved topic, it is possible to state that imaging play an increasing role in diagnosis and management of patients with suspected instability. The aim of this study is to investigate the different imaging modalities most indicated in diagnosis if vertebral instability and whether degenerative change can be associated with lower back pain.

  11. Quantitative Trait Loci Affecting Phenotypic Plasticity and the Allometric Relationship of Ovariole Number and Thorax Length in Drosophila melanogaster

    PubMed Central

    Bergland, Alan O.; Genissel, Anne; Nuzhdin, Sergey V.; Tatar, Marc

    2008-01-01

    Environmental factors during juvenile growth such as temperature and nutrition have major effects on adult morphology and life-history traits. In Drosophila melanogaster, ovary size, measured as ovariole number, and body size, measured as thorax length, are developmentally plastic traits with respect to larval nutrition. Herein we investigated the genetic basis for plasticity of ovariole number and body size, as well the genetic basis for their allometric relationship using recombinant inbred lines (RILs) derived from a natural population in Winters, California. We reared 196 RILs in four yeast concentrations and measured ovariole number and body size. The genetic correlation between ovariole number and thorax length was positive, but the strength of this correlation decreased with increasing yeast concentration. Genetic variation and genotype-by-environment (G × E) interactions were observed for both traits. We identified quantitative trait loci (QTL), epistatic, QTL-by-environment, and epistatic-by-environment interactions for both traits and their scaling relationships. The results are discussed in the context of multivariate trait evolution. PMID:18716336

  12. Biodegradability of plastics.

    PubMed

    Tokiwa, Yutaka; Calabia, Buenaventurada P; Ugwu, Charles U; Aiba, Seiichi

    2009-08-26

    Plastic is a broad name given to different polymers with high molecular weight, which can be degraded by various processes. However, considering their abundance in the environment and their specificity in attacking plastics, biodegradation of plastics by microorganisms and enzymes seems to be the most effective process. When plastics are used as substrates for microorganisms, evaluation of their biodegradability should not only be based on their chemical structure, but also on their physical properties (melting point, glass transition temperature, crystallinity, storage modulus etc.). In this review, microbial and enzymatic biodegradation of plastics and some factors that affect their biodegradability are discussed.

  13. Biodegradability of Plastics

    PubMed Central

    Tokiwa, Yutaka; Calabia, Buenaventurada P.; Ugwu, Charles U.; Aiba, Seiichi

    2009-01-01

    Plastic is a broad name given to different polymers with high molecular weight, which can be degraded by various processes. However, considering their abundance in the environment and their specificity in attacking plastics, biodegradation of plastics by microorganisms and enzymes seems to be the most effective process. When plastics are used as substrates for microorganisms, evaluation of their biodegradability should not only be based on their chemical structure, but also on their physical properties (melting point, glass transition temperature, crystallinity, storage modulus etc.). In this review, microbial and enzymatic biodegradation of plastics and some factors that affect their biodegradability are discussed. PMID:19865515

  14. Substratum cavities affect growth-plasticity, allometry, movement and feeding rates in the sea urchin Strongylocentrotus purpuratus.

    PubMed

    Hernández, J C; Russell, M P

    2010-02-01

    We assessed the influence of rock cavities, or pits, on the growth dynamics and behavior of the purple sea urchin, Strongylocentrotus purpuratus. In a paired-designed, laboratory experiment, sea urchins were assigned to sandstone blocks that were either 'Flat' or had a 'Pit' drilled into the center. At the start, both groups were approximately the same shape and size. In just 2 months, the shapes of the tests were significantly different between the two treatments, with the Pit urchins having an increased height:diameter profile. This result demonstrates the plastic nature of the sea urchin test and that, despite its apparent rigidity, it is capable of deforming during growth. In addition, the presence of pits modified behavior and food consumption as well as allometric growth of the test and Aristotle's lantern. Sea urchins on Pit sandstone blocks tended to stay in the cavities and not move about the flat areas, whereas individuals on Flat blocks changed position. Sea urchins in the Pit treatment consumed less food and had relatively larger demipyramids (the 'jaw' ossicle in Aristotle's lantern). These morphological and allometric changes occurred over a short time-period (8-20 weeks). We conclude that microhabitat is an important factor in controlling the behavior and growth dynamics of the bioeroding sea urchin S. purpuratus.

  15. On Factors Affecting the Phase Transformation and Mechanical Properties of Cold-Rolled Transformation-Induced-Plasticity-Aided Steel

    NASA Astrophysics Data System (ADS)

    Soliman, Mohamed; Palkowski, Heinz

    2008-10-01

    Two Mo-Nb microalloyed transformation-induced-plasticity (TRIP) steels, with Al contents of 0.23 and 0.65, were subjected to several hot-rolling conditions designed to generate different ferrite morphologies and grain sizes. These structures were then cold rolled and TRIP annealed under different heat-treatment conditions. To further develop TRIP steel in terms of strength and ductility, stabilizing retained austenite by isothermal bainitic transformation was studied in detail. Microstructure observation and tensile tests were conducted, and volume fractions of retained austenite were measured. It was observed that increasing the aluminum content enhances the transformation rate and increases the total amount of bainite fraction at the expense of retained austenite. The latter effect enhances formability by increasing ductility. Furthermore, it was observed that the hot-rolling schedule, prior to cold rolling and heat treatment, has a decisive effect on structure refinement, which enhances the strength-ductility balance of the final product. To study the transformation behavior, dilatometer testing was conducted under conditions similar to that of the heat treatment. Thermodynamic calculations were used to verify the results.

  16. Colored light-quality selective plastic films affect anthocyanin content, enzyme activities, and the expression of flavonoid genes in strawberry (Fragaria × ananassa) fruit.

    PubMed

    Miao, Lixiang; Zhang, Yuchao; Yang, Xiaofang; Xiao, Jinping; Zhang, Huiqin; Zhang, Zuofa; Wang, Yuezhi; Jiang, Guihua

    2016-09-15

    The influence of colored light-quality selective plastic films (red, yellow, green, blue, and white) on the content of anthocyanin, the activities of the related enzymes and the transcripts of the flavonoid gene was studied in developing strawberry fruit. The results indicated that colored films had highly significant effects on the total anthocyanin content (TAC) and proportions of individual anthocyanins. Compared with the white control film, the red and yellow films led to the significant increase of TAC, while the green and blue films caused a decrease of TAC. Colored film treatments also significantly affected the related enzyme activity and the expression of structural genes and transcription factor genes, which suggested that the enhancement of TAC by the red and yellow films might have resulted from the activation of related enzymes and transcription factor genes in the flavonoid pathway. Treatment with red and yellow light-quality selective plastic films might be useful as a supplemental cultivation practice for enhancing the anthocyanin content in developing strawberry fruit.

  17. Early social instability affects plasma testosterone during adolescence but does not alter reproductive capacity or measures of stress later in life.

    PubMed

    Siegeler, Katja; Wistuba, Joachim; Damm, Oliver S; von Engelhardt, Nikolaus; Sachser, Norbert; Kaiser, Sylvia

    2013-08-15

    The social environment plays an important role in modulating processes of the hormonal and behavioural profile of an animal in a variety of group-living species. In wild cavies for instance, unstable social environmental conditions during pregnancy and lactation lead to an infantilised biobehavioural profile of the male offspring. In the present study, the influence of the social environment during pregnancy and lactation on the male wild cavy offsprings' plasma testosterone development, reproductive capacity and stress system activity was investigated. To this purpose, 12 sons whose mothers had lived in an unstable social environment during pregnancy and lactation were compared with 12 sons whose mothers had lived in a stable social environment during the same time. Plasma testosterone (T) and plasma cortisol (C) concentrations were determined from days 20 to 107 of age. Adrenal tyrosine hydroxylase (TH) activity and different parameters of reproductive capacity (weights of testes, epididymides and accessory sex glands, cellular composition of the testes, DNA fragmentation indices and sperm motility parameters) were analysed at day 107 of age. TH activity and plasma C were unaffected by different social environmental conditions early in life. The developmental time course of T concentrations, however, was significantly different: Sons whose mothers had lived in an unstable social environment during pregnancy and lactation showed a delayed increase in T concentrations around adolescence compared to controls. In contrast, no reproduction-related parameters measured within this study differed significantly between the two groups. Thus, early social instability affects plasma testosterone development during adolescence in a significant way but does not alter reproductive capacity or measures of stress later in life.

  18. Propagating Instabilities in Solids

    NASA Astrophysics Data System (ADS)

    Kyriakides, Stelios

    1998-03-01

    Instability is one of the factors which limit the extent to which solids can be loaded or deformed and plays a pivotal role in the design of many structures. Such instabilities often result in localized deformation which precipitates catastrophic failure. Some materials have the capacity to recover their stiffness following a certain amount of localized deformation. This local recovery in stiffness arrests further local deformation and spreading of the instability to neighboring material becomes preferred. Under displacement controlled loading the propagation of the transition fronts can be achieved in a steady-state manner at a constant stress level known as the propagation stress. The stresses in the transition fronts joining the highly deformed zone to the intact material overcome the instability nucleation stresses and, as a result, the propagation stress is usually much lower than the stress required to nucleate the instability. The classical example of this class of material instabilities is L/"uders bands which tend to affect mild steels and other metals. Recent work has demonstrated that propagating instabilities occur in several other materials. Experimental and analytical results from four examples will be used to illustrate this point: First the evolution of L=FCders bands in mild steel strips will be revisited. The second example involves the evolution of stress induced phase transformations (austenite to martensite phases and the reverse) in a shape memory alloy under displacement controlled stretching. The third example is the crushing behavior of cellular materials such as honeycombs and foams made from metals and polymers. The fourth example involves the axial broadening/propagation of kink bands in aligned fiber/matrix composites under compression. The microstructure and, as a result, the micromechanisms governing the onset, localization, local arrest and propagation of instabilities in each of the four materials are vastly different. Despite this

  19. How Plastics Work

    NASA Astrophysics Data System (ADS)

    Bloomfield, Louis

    2013-03-01

    We encounter plastics every day, but despite their widespread use, amazing range of properties, and basic scientific underpinnings, most physicists--like most people--know relatively little about plastics. In contrast to hard crystalline and amorphous solids (e.g., metals, salts, ceramics, and glasses), we take plastics for granted, select them carelessly, and examine them more closely only on a need-to-know basis. By ignoring plastics until we need them, however, we risk not knowing what we don't know and using the wrong ones. To repurpose a familiar advertisement, ``there's a plastic for that.'' This talk will review some of the basic physics and science of plastics. It will examine the roles of temperature, order, intermolecular forces, entanglements, and linkages in plastics, and how those issues affect the properties of a given plastic. We'll stop along the way to recognize a few of the more familiar plastics, natural and synthetic, and explain some of their mechanical, chemical, and optical properties. The talk will conclude by explaining the remarkable properties of a plastic that has been largely misunderstood since its discovery 70 years ago: Silly Putty.

  20. Posterior Shoulder Instability.

    PubMed

    Brelin, Alaina; Dickens, Jonathan F

    2017-09-01

    Posterior shoulder instability is a relatively uncommon condition, occurring in ∼10% of those with shoulder instability. Because of the rarity of the condition and the lack of knowledge in treatment, it is often misdiagnosed or patients experience a delay in diagnosis. Posterior instability typically affects athletes participating in contact or overhead sports and is usually the result of repetitive microtrauma or blunt force with the shoulder in the provocative position of flexion, adduction, and internal rotation, leading to recurrent subluxation events. Acute traumatic posterior dislocations are rare injuries with an incidence rate of 1.1 per 100,000 person years. This rate is ∼20 times lower than that of anterior shoulder dislocations. Risk factors for recurrent instability are: (1) age below 40 at time of first instability; (2) dislocation during a seizure; (3) a large reverse Hill-Sachs lesion; and (4) glenoid retroversion. A firm understanding of the pathoanatomy, along with pertinent clinical and diagnostic modalities is required to accurately diagnosis and manage this condition.

  1. A numerical and analytical investigation of Rayleigh-Taylor instability in a solid tungsten plate

    SciTech Connect

    Robinson, A.C.; Swegle, J.W.

    1987-07-01

    The Rayleigh-Taylor instability response of an elastic-plastic tungsten plate is investigated by numerical experiments and an approximate modal analysis. The so-called ''minimum amplitude'' instability criteria derived from plasticity analyses is shown to be incomplete as a general indicator of instability or stability at very large driving pressures. Model equations are derived which are able to reproduce the basic qualitative features of the observed instability response given by the numerical calculations. 11 refs., 29 figs.

  2. Rayleigh-Taylor and Richtmyer-Meshkov Instabilities in Turbulent Regime

    NASA Astrophysics Data System (ADS)

    Dimonte, G.

    1998-11-01

    The Rayleigh-Taylor instability (RTI) and its shock driven analog, the Richtmyer-Meshkov instability (RMI), affect a wide variety of important phenomena from sub-terrainian to astrophysical environments. The ``fluids" are equally varied from plasmas and magnetic fields to elastic-plastic solids. In most applications, the instabilities occur with a complex acceleration history and evolve to a highly nonlinear state, making the theoretical description formidable. We will link the fluid and plasma regimes while describing the theoretical issues and basic experiments in different venues to isolate key physics issues. RMI experiments on the Nova laser investigate the affects of compressibility with strong radiatively driven shocks (Mach > 10) in near solid density plasmas of sub-millimeter scale. The growth of single sinusoidal and random 3-D perturbations are measured using backlit radiography. RTI experiments with the Linear Electric Motor (LEM) are conducted with a variety of acceleration (<< 10^4 m/s^2) histories and fluids of 10 cm scale. Turbulent RTI experiments with high Reynolds number liquids show self-similar growth which is characterized with laser induced fluorescence. LEM experiments with an elastic-plastic material (yogurt) exhibit a critical wavelength and amplitude for instability. The experimental results will be compared with linear and nonlinear theories and hydrodynamic simulations.

  3. Quinolinic acid injection in mouse medial prefrontal cortex affects reversal learning abilities, cortical connectivity and hippocampal synaptic plasticity

    PubMed Central

    Latif-Hernandez, Amira; Shah, Disha; Ahmed, Tariq; Lo, Adrian C.; Callaerts-Vegh, Zsuzsanna; Van der Linden, Annemie; Balschun, Detlef; D’Hooge, Rudi

    2016-01-01

    Intracerebral injection of the excitotoxic, endogenous tryptophan metabolite, quinolinic acid (QA), constitutes a chemical model of neurodegenerative brain disease. Complementary techniques were combined to examine the consequences of QA injection into medial prefrontal cortex (mPFC) of C57BL6 mice. In accordance with the NMDAR-mediated synapto- and neurotoxic action of QA, we found an initial increase in excitability and an augmentation of hippocampal long-term potentiation, converting within two weeks into a reduction and impairment, respectively, of these processes. QA-induced mPFC excitotoxicity impaired behavioral flexibility in a reversal variant of the hidden-platform Morris water maze (MWM), whereas regular, extended MWM training was unaffected. QA-induced mPFC damage specifically affected the spatial-cognitive strategies that mice use to locate the platform during reversal learning. These behavioral and cognitive defects coincided with changes in cortical functional connectivity (FC) and hippocampal neuroplasticity. FC between various cortical regions was assessed by resting-state fMRI (rsfMRI) methodology, and mice that had received QA injection into mPFC showed increased FC between various cortical regions. mPFC and hippocampus (HC) are anatomically as well as functionally linked as part of a cortical network that controls higher-order cognitive functions. Together, these observations demonstrate the central functional importance of rodent mPFC as well as the validity of QA-induced mPFC damage as a preclinical rodent model of the early stages of neurodegeneration. PMID:27819338

  4. Congenital absence of corticospinal tract does not severely affect plastic changes of the developing postnatal spinal cord.

    PubMed

    Huang, L; Xian, Q; Shen, N; Shi, L; Qu, Y; Zhou, L

    2015-08-20

    The arrival and refinement of corticospinal afferents are likely to influence the maturation of the spinal cord and sensory-motor networks. To understand this better, we studied the revision of monosynaptic muscle afferents, the expression of activity-related genes, neurotrophins and their receptors in the cervical spinal cord from postnatal day (P) 0 to 21. We compared control and Celsr3|Emx1 mice, in which corticospinal axons never develop. The corticospinal tract (CST), labeled by anti-protein kinase C gamma (PKCγ) antibody in the dorsal funiculus, increased gradually in the control, but was never visible in the mutant. Using anti-parvalbumin and choline acetyltransferase double immunostaining, close contacts between proprioceptive afferent fibers and spinal motor neurons appeared at P0 and were gradually eliminated thereafter, with no difference between control and mutant mice. In both genotypes, the number of parvalbumin-positive interneurons increased similarly from P7 to P21, and a comparable upregulation of c-Jun protein was seen at P7. Contrary to control samples, in which ciliary neurotrophic factor (CNTF) protein levels increased from P0 to P7 and gradually decreased after P14, CNTF concentrations were time-invariant in mutant samples. The dynamic profile of neurotrophin-3 (NT3) expression was also moderately affected in mutant mice. In control spinal cord, NT3 was increased at P7 and decreased at P14, but remained more stable in mutant samples. In contrast, expression profiles of brain-derived neurotrophic factor (BDNF), tropomyosin-related kinase (Trk) B, TrkC, p75 neurotrophin receptor (p75(NTR)) and glial cell-line-derived neurotrophic factor (GDNF) were similar in both genotypes. In conclusion, with the possible exception of CNTF and NT3 expression, most events that accompany maturation of the spinal cord appear largely independent of corticospinal inputs.

  5. Gestational stress and fluoxetine treatment differentially affect plasticity, methylation and serotonin levels in the PFC and hippocampus of rat dams.

    PubMed

    Gemmel, Mary; Rayen, Ine; van Donkelaar, Eva; Loftus, Tiffany; Steinbusch, Harry W; Kokras, Nikolaos; Dalla, Christina; Pawluski, Jodi L

    2016-07-07

    Women are more likely to develop depression during childbearing years with up to 20% of women suffering from depression during pregnancy and in the postpartum period. Increased prevalence of depression during the perinatal period has resulted in frequent selective serotonin reuptake inhibitor (SSRI) antidepressant treatment; however the effects of such medications on the maternal brain remain limited. Therefore, the aim of the present study is to investigate the effects of the SSRI medication, fluoxetine, on neurobiological differences in the maternal brain. To model aspects of maternal depression, gestational stress was used. Sprague-Dawley rat dams were exposed to either gestational stress and/or fluoxetine (5mg/kg/day) to form the following four groups: 1. Control+Vehicle, 2. Stress+Vehicle, 3. Control+Fluoxetine, and 4. Stress+Fluoxetine. At weaning maternal brains were collected. Main findings show that gestational stress alone increased synaptophysin and serotonin metabolism in the cingulate cortex2 region of the cortex while fluoxetine treatment after stress normalized these effects. In the hippocampus, fluoxetine treatment, regardless of gestational stress exposure, decreased both global measures of methylation in the dentate gyrus, as measured by Dnmt3a immunoreactivity, as well as serotonin metabolism. No further changes in synaptophysin, PSD-95, or Dnmt3a immunoreactivity were seen in the cortical or hippocampal areas investigated. These findings show that gestational stress and SSRI medication affect the neurobiology of the maternal brain in a region-specific manner. This work adds to a much needed area of research aimed at understanding neurobiological changes associated with maternal depression and the role of SSRI treatment in altering these changes in the female brain. Copyright © 2016 IBRO. Published by Elsevier Ltd. All rights reserved.

  6. Micromechanics of nonlinear plastic modes.

    PubMed

    Lerner, Edan

    2016-05-01

    Nonlinear plastic modes (NPMs) are collective displacements that are indicative of imminent plastic instabilities in elastic solids. In this work we formulate the atomistic theory that describes the reversible evolution of NPMs and their associated stiffnesses under external deformations. The deformation dynamics of NPMs is compared to those of the analogous observables derived from atomistic linear elastic theory, namely, destabilizing eigenmodes of the dynamical matrix and their associated eigenvalues. The key result we present and explain is that the dynamics of NPMs and of destabilizing eigenmodes under external deformations follow different scaling laws with respect to the proximity to imminent instabilities. In particular, destabilizing modes vary with a singular rate, whereas NPMs exhibit no such singularity. As a result, NPMs converge much earlier than destabilizing eigenmodes to their common final form at plastic instabilities. This dynamical difference between NPMs and linear destabilizing eigenmodes underlines the usefulness of NPMs for predicting the locus and geometry of plastic instabilities, compared to their linear-elastic counterparts.

  7. Hybrid rocket instability

    NASA Technical Reports Server (NTRS)

    Greiner, B.; Frederick, R. A., Jr.

    1993-01-01

    The paper provides a brief review of theoretical and experimental studies concerned with hybrid rocket instability. The instabilities discussed include atomization and mixing instabilities, chuffing instabilities, pressure coupled combustion instabilities, and vortex shedding. It is emphasized that the future use of hybrid motor systems as viable design alternatives will depend on a better understanding of hybrid instability.

  8. Persistence, distribution, and emission of Telone C35 injected into a Florida sandy soil as affected by moisture, organic matter, and plastic film cover.

    PubMed

    Thomas, J E; Ou, L T; Allen, L H; McCormack, L A; Vu, J C; Dickson, D W

    2004-05-01

    With the phase-out of methyl bromide scheduled for 2005, alternative fumigants are being sought. This study of Telone C35, a mixture of (Z)- and (E)-1,3-dichloropropene (1,3-D) with chloropicirin (CP), focuses on its emissions, distribution, and persistence in Florida sandy soil in microplots with different soil-water and organic matter carbon (C) content with and without two different plastic film mulches. The addition of CP did not affect the physical behavior of the isomers of 1,3-D. Slower subsurface dispersion and longer residence time of the mixed fumigant occurred at higher water content. An increase in the percent organic carbon in the soil led to a more rapid decrease for chloropicirin than for 1,3-dichloropene isomers. The use of a virtually impermeable film (VIF) for soil cover provided a more even distribution and longer persistence under all the conditions studied in comparison to polyethylene (PE) film cover or no cover. The conditions of near field capacity water content, low organic matter, and a virtually impermeable film cover yielded optimum conditions for the distribution, emission control, and persistence of Telone C35 in a Florida sandy soil.

  9. Plastic Jellyfish.

    ERIC Educational Resources Information Center

    Moseley, Christine

    2000-01-01

    Presents an environmental science activity designed to enhance students' awareness of the hazards of plastic waste for wildlife in aquatic environments. Discusses how students can take steps to reduce the effects of plastic waste. (WRM)

  10. Plastic Jellyfish.

    ERIC Educational Resources Information Center

    Moseley, Christine

    2000-01-01

    Presents an environmental science activity designed to enhance students' awareness of the hazards of plastic waste for wildlife in aquatic environments. Discusses how students can take steps to reduce the effects of plastic waste. (WRM)

  11. [Treatment of patellar instability].

    PubMed

    Lind, Martin; Faunø, Peter; Sørensen, Ole Gade; Mygind-Klavsen, Bjarne

    2017-09-18

    First-time patellar luxation appears typically in teenagers and young adults below the age of 16 years, with a prevalence of 45/100,000/year. This luxation is treated with brief limited mobility in a bandage, and with a complementary physiotherapy if the mobility is influenced afterwards. Risk factors for patellar instability are patellofemoral dysplasia, hyperlaxity, patella alta and valgus malalignment in the knee joint. In case of repeated luxation the treatment is surgical, i.e. reconstruction of the medial patellofemoral ligament recreating the medial patella-stabilizing structures. If the dysplasia is severe, tuberositas tibiae-osteotomy and trochlea plastic can correct a lateral tracking of the knee joint. Generally, patella-stabilizing surgery is successful with a reluxation rate of only a few per cent.

  12. Rayleigh-Taylor instability in elastic solids

    NASA Astrophysics Data System (ADS)

    Piriz, A. R.; Cela, J. J. López; Cortázar, O. D.; Tahir, N. A.; Hoffmann, D. H. H.

    2005-11-01

    We present an analytical model for the Rayleigh-Taylor instability that allows for an approximate but still very accurate and appealing description of the instability physics in the linear regime. The model is based on the second law of Newton and it has been developed with the aim of dealing with the instability of accelerated elastic solids. It yields the asymptotic instability growth rate but also describes the initial transient phase determined by the initial conditions. We have applied the model to solid/solid and solid/fluid interfaces with arbitrary Atwood numbers. The results are in excellent agreement with previous models that yield exact solutions but which are of more limited validity. Our model allows for including more complex physics. In particular, the present approach is expected to lead to a more general theory of the instability that would allow for describing the transition to the plastic regime.

  13. Rayleigh-Taylor instability in elastic solids.

    PubMed

    Piriz, A R; Cela, J J López; Cortázar, O D; Tahir, N A; Hoffmann, D H H

    2005-11-01

    We present an analytical model for the Rayleigh-Taylor instability that allows for an approximate but still very accurate and appealing description of the instability physics in the linear regime. The model is based on the second law of Newton and it has been developed with the aim of dealing with the instability of accelerated elastic solids. It yields the asymptotic instability growth rate but also describes the initial transient phase determined by the initial conditions. We have applied the model to solid/solid and solid/fluid interfaces with arbitrary Atwood numbers. The results are in excellent agreement with previous models that yield exact solutions but which are of more limited validity. Our model allows for including more complex physics. In particular, the present approach is expected to lead to a more general theory of the instability that would allow for describing the transition to the plastic regime.

  14. Developmental instability of gynodioecious Teucrium lusitanicum

    USGS Publications Warehouse

    Alados, C.L.; Navarro, T.; Cabezudo, B.; Emlen, J.M.; Freeman, C.

    1998-01-01

    Developmental instability was assessed in two geographical races of Teucrium lusitanicum using morphometric measures of vegetative and reproductive structures. T. lusitanicum is a gynodioecious species. Male sterile (female) individuals showed greater developmental instability at all sites. Plants located inland had higher developmental instability of vegetative characters and lower developmental instability of reproductive characters than coastal plants. These results support the contentions that (1) developmental instability is affected more by the disruption of co-adapted gene complexes than by lower heterozygosity, and (2) different habitat characteristics result in the differential response of vegetative and reproductive structures.

  15. Magnetohydrodynamic instability

    NASA Technical Reports Server (NTRS)

    Priest, E. R.; Cargill, P.; Forbes, T. G.; Hood, A. W.; Steinolfson, R. S.

    1986-01-01

    There have been major advances in the theory of magnetic reconnection and of magnetic instability, with important implications for the observations, as follows: (1) Fast and slow magnetic shock waves are produced by the magnetohydrodynamics of reconnection and are potential particle accelerators. (2) The impulsive bursty regime of reconnection gives a rapid release of magnetic energy in a series of bursts. (3) The radiative tearing mode creates cool filamentary structures in the reconnection process. (4) The stability analyses imply that an arcade can become unstable when either its height or twist of plasma pressure become too great.

  16. GluN2B antagonism affects interneurons and leads to immediate and persistent changes in synaptic plasticity, oscillations, and behavior.

    PubMed

    Hanson, Jesse E; Weber, Martin; Meilandt, William J; Wu, Tiffany; Luu, Tom; Deng, Lunbin; Shamloo, Mehrdad; Sheng, Morgan; Scearce-Levie, Kimberly; Zhou, Qiang

    2013-06-01

    Although antagonists to GluN2B-containing N-methyl-D-aspartate receptors (NMDARs) have been widely considered to be neuroprotective under certain pathological conditions, their immediate and lasting impacts on synaptic, circuit, and cognitive functions are poorly understood. In hippocampal slices, we found that the GluN2B-selective antagonist Ro25-6981 (Ro25) reduced synaptic NMDAR responses and consequently neuronal output in a subpopulation of GABAergic interneurons, but not pyramidal neurons. Consistent with these effects, Ro25 reduced GABAergic responses in pyramidal neurons and hence could affect circuit functions by altering the excitation/inhibition balance in the brain. In slices from Ts65Dn mice, a Down syndrome model with excess inhibition and cognitive impairment, acutely applied Ro25-rescued long-term potentiation (LTP) and gamma oscillation deficits, whereas prolonged dosing induced persistent rescue of LTP. In contrast, Ro25 did not impact LTP in wild-type (wt) mice but reduced gamma oscillations both acutely and following prolonged treatment. Although acute Ro25 treatment impaired memory performance in wt mice, memory deficits in Ts65Dn mice were unchanged. Thus, GluN2B-NMDARs contribute to the excitation/inhibition balance via impacts on interneurons, and blocking GluN2B-NMDARs can alter functions that depend on this balance, including synaptic plasticity, gamma oscillations, and memory. That prolonged GluN2B antagonism leads to persistent changes in synaptic and circuit functions, and that the influence of GluN2B antagonism differs between wt and disease model mice, provide critical insight into the therapeutic potential and possible liabilities of GluN2B antagonists.

  17. GluN2B Antagonism Affects Interneurons and Leads to Immediate and Persistent Changes in Synaptic Plasticity, Oscillations, and Behavior

    PubMed Central

    Hanson, Jesse E; Weber, Martin; Meilandt, William J; Wu, Tiffany; Luu, Tom; Deng, Lunbin; Shamloo, Mehrdad; Sheng, Morgan; Scearce-Levie, Kimberly; Zhou, Qiang

    2013-01-01

    Although antagonists to GluN2B-containing N-methyl-𝒟-aspartate receptors (NMDARs) have been widely considered to be neuroprotective under certain pathological conditions, their immediate and lasting impacts on synaptic, circuit, and cognitive functions are poorly understood. In hippocampal slices, we found that the GluN2B-selective antagonist Ro25-6981 (Ro25) reduced synaptic NMDAR responses and consequently neuronal output in a subpopulation of GABAergic interneurons, but not pyramidal neurons. Consistent with these effects, Ro25 reduced GABAergic responses in pyramidal neurons and hence could affect circuit functions by altering the excitation/inhibition balance in the brain. In slices from Ts65Dn mice, a Down syndrome model with excess inhibition and cognitive impairment, acutely applied Ro25-rescued long-term potentiation (LTP) and gamma oscillation deficits, whereas prolonged dosing induced persistent rescue of LTP. In contrast, Ro25 did not impact LTP in wild-type (wt) mice but reduced gamma oscillations both acutely and following prolonged treatment. Although acute Ro25 treatment impaired memory performance in wt mice, memory deficits in Ts65Dn mice were unchanged. Thus, GluN2B–NMDARs contribute to the excitation/inhibition balance via impacts on interneurons, and blocking GluN2B–NMDARs can alter functions that depend on this balance, including synaptic plasticity, gamma oscillations, and memory. That prolonged GluN2B antagonism leads to persistent changes in synaptic and circuit functions, and that the influence of GluN2B antagonism differs between wt and disease model mice, provide critical insight into the therapeutic potential and possible liabilities of GluN2B antagonists. PMID:23340518

  18. rTMS stimulation to induce plastic changes at the language motor area in a patient with a left recidivant brain tumor affecting Broca's area.

    PubMed

    Barcia, Juan A; Sanz, Ana; González-Hidalgo, Mercedes; de Las Heras, Carmen; Alonso-Lera, Pedro; Díaz, Pedro; Pascual-Leone, Alvaro; Oliviero, Antonio; Ortiz, Tomás

    2012-01-01

    Extent of resection is one of the most powerful predictors of outcome in surgery of gliomas. Tumors located within areas governing eloquence may impede a total tumor resection. Functional plasticity may be induced by therapeutic means, such as cortical stimulation with repetitive transcranial magnetic stimulation (rTMS). Thus, rTMS is a potential tool to induce an improvement of functions of eloquence menaced by brain tumors. We report a case of a 59-year-old woman operated for a left sided precentral oligodendroglioma with awake intraoperative stimulation, whose tumor could not be completely removed because it affected areas governing language. Nine months later the tumor progressed and the motor language functions worsened. We submitted the patient to rTMS directed to Broca's area, next to the anterior pole of the tumor, with the aim of improving motor language function before a new tumor resection attempt. We performed 12 daily sessions of theta-burst rTMS followed by intensive language rehabilitation for 10 minutes, and 5 different aspects of language were measured before, immediately after and 10 minutes after each session. Repetition and nomination worsened immediately after each rTMS session, and improved after 10 min of rehabilitation. However, basal values improved globally along the experiment. Also, the impact of rTMS on motor language was increasingly less along the procedure. rTMS induces changes in Broca's area and this effect can be potentially used to improve language function in tumors located at or close to eloquent cortical areas.

  19. Escitalopram affects cytoskeleton and synaptic plasticity pathways in a rat gene-environment interaction model of depression as revealed by proteomics. Part II: environmental challenge.

    PubMed

    Piubelli, Chiara; Vighini, Miriam; Mathé, Aleksander A; Domenici, Enrico; Carboni, Lucia

    2011-07-01

    Large-scale investigations aimed at elucidating the molecular mechanism of action of antidepressant treatment are achievable through the application of proteomic technologies. We performed a proteomic study on the Flinders Sensitive Line (FSL), a genetically selected rat model of depression, and the control Flinders Resistant Line (FRL). To evaluate gene-environment interactions, FSL and FRL animals were separated from their mothers for 3 h from postnatal days 2 to 14 (maternal separation; MS), since early-life trauma is considered an important antecedent of depression. All groups received either escitalopram (Esc) admixed to food pellets (25 mg/kg.d) or vehicle for 1 month. Protein extracts from prefrontal/frontal cortex and hippocampus were separated by 2D electrophoresis. Proteins differentially modulated were identified by mass spectrometry. Bioinformatics analyses were performed to discover gene ontology terms associated with the modulated proteins. This paper was focused on the modifications induced by the environmental challenge of MS, both on the predisposed genetic background and on the resistant phenotype. The combination between Esc treatment and MS was investigated by comparing the MS, Esc-treated rats with rats subjected to each single procedure. In MS rats, antidepressant treatment influenced mainly proteins involved in carbohydrate metabolism in FSL rats and in vesicle-mediated transport in FRL rats. When studying the interaction between Esc and MS vs. non-separated rats, proteins playing a role in cytoskeleton organization, neuronal development, vesicle-mediated transport and synaptic plasticity were identified. The results provide further support to the available reports that antidepressant treatment affects intracellular pathways and also suggest new potential targets for future therapeutic intervention.

  20. Kinetic theory of Jeans instability.

    PubMed

    Trigger, S A; Ershkovich, A I; van Heijst, G J F; Schram, P P J M

    2004-06-01

    Kinetic treatment of the Jeans gravitational instability, with collisions taken into account, is presented. The initial-value problem for the distribution function which obeys the kinetic equation, with the collision integral conserving the number of particles, is solved. Dispersion relation is obtained and analyzed. New modes are found. Collisions are shown not to affect the Jeans instability criterion. Although the instability growth rate diminishes, the collisions they cannot quench the instability. However, the oscillation spectrum is modified significantly: even in the neighborhood of the threshold frequency omega=0 (separating stable and unstable modes) the spectrum of oscillations can strongly depend on the collision frequency. Propagating (rather than aperiodic) modes are also found. These modes, however, are strongly damped.

  1. Fluid Instabilities inside Astrophysical Explosions

    NASA Astrophysics Data System (ADS)

    Chen, Ke-Jung; Woosley, Stan; Heger, Alexander; Almgren, Ann; Zheng, Weiqun

    2014-11-01

    We present our results from the simulations of fluid instabilities inside supernovae with a new radiation-hydrodynamic code, CASTRO. Massive stars are ten times more massive than Sun. Observational and theoretical studies suggest that these massive stars tend to end their lives with energetic explosions, so-called supernovae. Many fluid instabilities occur during the supernova explosions. The fluid instabilities can be driven by hydrodynamics, nuclear burning, or radiation. In this talk, we discuss about the possible physics of fluid instabilities found in our simulations and how the resulting mixing affects the observational signatures of supernovae. This work was supported by the DOE HEP Program under contract DE-SC0010676; the National Science Foundation (AST 0909129) and the NASA Theory Program (NNX14AH34G).

  2. Plastics Technology.

    ERIC Educational Resources Information Center

    Barker, Tommy G.

    This curriculum guide is designed to assist junior high schools industrial arts teachers in planning new courses and revising existing courses in plastics technology. Addressed in the individual units of the guide are the following topics: introduction to production technology; history and development of plastics; safety; youth leadership,…

  3. Plastics Technology.

    ERIC Educational Resources Information Center

    Barker, Tommy G.

    This curriculum guide is designed to assist junior high schools industrial arts teachers in planning new courses and revising existing courses in plastics technology. Addressed in the individual units of the guide are the following topics: introduction to production technology; history and development of plastics; safety; youth leadership,…

  4. Plastic stability of metallic glass composites under tension

    NASA Astrophysics Data System (ADS)

    Wu, F. F.; Li, S. T.; Zhang, G. A.; Wu, X. F.; Lin, P.

    2013-10-01

    The plastic stability of metallic glass composites (MGCs) under tension was investigated. There exists a critical normalized strain-hardening rate determining the plastic stability of MGCs: if the normalized strain-hardening rate is smaller than the critical normalized strain-hardening rate, the plastic instability occurs, thus, leading to localized plastic strain in MGCs; otherwise the plastic stability is in charge of the plastic deformation of the MGCs, so the strain localization or necking is effectively suppressed, which results in homogeneous elongation in MGCs.

  5. DNA profiling analysis of 100 consecutive de novo acute myeloid leukemia cases reveals patterns of genomic instability that affect all cytogenetic risk groups.

    PubMed

    Suela, J; Alvarez, S; Cifuentes, F; Largo, C; Ferreira, B I; Blesa, D; Ardanaz, M; García, R; Marquez, J A; Odero, M D; Calasanz, M J; Cigudosa, J C

    2007-06-01

    We have carried out a high-resolution whole genome DNA profiling analysis on 100 bone marrow samples from a consecutive series of de novo acute myeloid leukemia (AML) cases. After discarding copy number changes that are known to be genetic polymorphisms, we found that genomic aberrations (GA) in the form of gains or losses of genetic material were present in 74% of the samples, with a median of 2 GA per case (range 0-35). In addition to the cytogenetically detected aberration, GA were present in cases from all cytogenetic prognostic groups: 79% in the favorable group, 60% in the intermediate group (including 59% of cases with normal karyotype) and 83% in the adverse group. Five aberrant deleted regions were recurrently associated with cases with a highly aberrant genome (e.g., a 1.5 Mb deletion at 17q11.2 and a 750 kb deletion at 5q31.1). Different degrees of genomic instability showed a statistically significant impact on survival curves, even within the normal karyotype cases. This association was independent of other clinical and genetic parameters. Our study provides, for the first time, a detailed picture of the nature and frequency of DNA copy number aberrations in de novo AML.

  6. Polygonal instabilities

    NASA Astrophysics Data System (ADS)

    Labousse, Matthieu

    2015-11-01

    The interaction of a vortex with a free surface is encountered in a series of experiments, the hydraulic jump, the hydraulic bump, the toroidal Leidenfrost experiment. All these experiments share in common an unstable configuration in which azimuthal perturbations give rise to polygonal patterns. We propose a unified theoretical framework to model the emergence of this instability by investigating the stability of a liquid torus with a poloidal motion. As simple as it is, we show that the model retains the necessary ingredients to account for the experimental observations. In this talk, I will first describe the model and compare it to the existing data. However this model is purely inviscid and reaches its limits when being applied to relatively moderate Reynolds flows. So in a second part, I will present a recent experimental and theoretical investigation in which polygonal patterns are now driven by Marangoni flows. To our great surprise, it extends the range of validity of the initial proposed framework, much more than initially expected.

  7. Rayleigh-Taylor instability in accelerated solid media

    NASA Astrophysics Data System (ADS)

    Piriz, A. R.; Sun, Y. B.; Tahir, N. A.

    2017-01-01

    A linear study of the Rayleigh-Taylor instability based on momentum conservation and the consideration of an irrotational velocity field for incompressible perturbations is discussed. The theory allows for a very appealing physical picture and for a relatively simple description of the main features of the instability. As a result, it is suitable for the study of the very complex problem of the instability of accelerated solids with non-linear elastic-plastic constitutive properties, which cannot be studied by the usual normal modes approach. The elastic to plastic transition occurring early in the instability process determines the entire evolution and makes the instability exhibit behavior that cannot be captured by an asymptotic analysis.

  8. Plastic welder

    NASA Technical Reports Server (NTRS)

    Buckley, J. D.; Fox, R. L.; Swain, R. J.

    1980-01-01

    Low-cost, self-contained, portable welder joins plastic parts by induction heating. Welder is useable in any atmosphere or in vacuum and with most types of thermoplastic; plastic components can be joined in situ. Device is applicable to aerospace industry and in automobile, furniture, and construction industries. Power requirements are easily met by battery or solar energy. In welder, toroidal inductor transfers magnetic flux through thermoplastic to screen. Heated screen causes plastic surface on either side to melt and flow into it to form joint.

  9. EPDM plasticizers

    SciTech Connect

    Godail, M.J.

    1983-08-01

    The properties of paraffinic, naphthenic, and aromatic extender oils used as EPDM plasticizers are discussed in detail. Particular attention is given to viscosity, volatility, specific gravity, and aromatic content.

  10. Plastic Surgery Statistics

    MedlinePlus

    ... PRS GO PSN PSEN GRAFT Contact Us News Plastic Surgery Statistics Plastic surgery procedural statistics from the ... Plastic Surgery Statistics 2005 Plastic Surgery Statistics 2016 Plastic Surgery Statistics Stats Report 2016 National Clearinghouse of ...

  11. Plastic-film mulching and urea types affect soil CO2 emissions and grain yield in spring maize on the Loess Plateau, China.

    PubMed

    Liu, Qiaofei; Chen, Yu; Li, Weiwei; Liu, Yang; Han, Juan; Wen, Xiaoxia; Liao, Yuncheng

    2016-06-22

    A 2-year field experiment was conducted on maize (Zea mays L.) to explore effective ways to decrease soil CO2 emissions and increase grain yield. Treatments established were: (1) no mulching with urea, (2) no mulching with controlled release fertiliser (CRF), (3) transparent plastic-film mulching (PMt) with urea, (4) PMt with CRF, (5) black plastic-film mulching (PMb) with urea, and (6) PMb with CRF. During the early growth stages, soil CO2 emissions were noted as PMt > PMb > no mulching, and this order was reversed in the late growth stages. This trend was the result of topsoil temperature dynamics. There were no significant correlations noted between soil CO2 emissions and soil temperature and moisture. Cumulative soil CO2 emissions were higher for the PMt than for the PMb, and grain yield was higher for the PMb treatments than for the PMt or no mulching treatments. The CRF produced higher grain yield and inhibited soil CO2 emissions. Soil CO2 emissions per unit grain yield were lower for the BC treatment than for the other treatments. In conclusion, the use of black plastic-film mulching and controlled release fertiliser not only increased maize yield, but also reduced soil CO2 emissions.

  12. Plastic-film mulching and urea types affect soil CO2 emissions and grain yield in spring maize on the Loess Plateau, China

    NASA Astrophysics Data System (ADS)

    Liu, Qiaofei; Chen, Yu; Li, Weiwei; Liu, Yang; Han, Juan; Wen, Xiaoxia; Liao, Yuncheng

    2016-06-01

    A 2-year field experiment was conducted on maize (Zea mays L.) to explore effective ways to decrease soil CO2 emissions and increase grain yield. Treatments established were: (1) no mulching with urea, (2) no mulching with controlled release fertiliser (CRF), (3) transparent plastic-film mulching (PMt) with urea, (4) PMt with CRF, (5) black plastic-film mulching (PMb) with urea, and (6) PMb with CRF. During the early growth stages, soil CO2 emissions were noted as PMt > PMb > no mulching, and this order was reversed in the late growth stages. This trend was the result of topsoil temperature dynamics. There were no significant correlations noted between soil CO2 emissions and soil temperature and moisture. Cumulative soil CO2 emissions were higher for the PMt than for the PMb, and grain yield was higher for the PMb treatments than for the PMt or no mulching treatments. The CRF produced higher grain yield and inhibited soil CO2 emissions. Soil CO2 emissions per unit grain yield were lower for the BC treatment than for the other treatments. In conclusion, the use of black plastic-film mulching and controlled release fertiliser not only increased maize yield, but also reduced soil CO2 emissions.

  13. Plastic-film mulching and urea types affect soil CO2 emissions and grain yield in spring maize on the Loess Plateau, China

    PubMed Central

    Liu, Qiaofei; Chen, Yu; Li, Weiwei; Liu, Yang; Han, Juan; Wen, Xiaoxia; Liao, Yuncheng

    2016-01-01

    A 2-year field experiment was conducted on maize (Zea mays L.) to explore effective ways to decrease soil CO2 emissions and increase grain yield. Treatments established were: (1) no mulching with urea, (2) no mulching with controlled release fertiliser (CRF), (3) transparent plastic-film mulching (PMt) with urea, (4) PMt with CRF, (5) black plastic-film mulching (PMb) with urea, and (6) PMb with CRF. During the early growth stages, soil CO2 emissions were noted as PMt > PMb > no mulching, and this order was reversed in the late growth stages. This trend was the result of topsoil temperature dynamics. There were no significant correlations noted between soil CO2 emissions and soil temperature and moisture. Cumulative soil CO2 emissions were higher for the PMt than for the PMb, and grain yield was higher for the PMb treatments than for the PMt or no mulching treatments. The CRF produced higher grain yield and inhibited soil CO2 emissions. Soil CO2 emissions per unit grain yield were lower for the BC treatment than for the other treatments. In conclusion, the use of black plastic-film mulching and controlled release fertiliser not only increased maize yield, but also reduced soil CO2 emissions. PMID:27329934

  14. Mechanical Instabilities of Biological Tubes

    NASA Astrophysics Data System (ADS)

    Hannezo, Edouard; Prost, Jacques; Joanny, Jean-François

    2012-07-01

    We study theoretically the morphologies of biological tubes affected by various pathologies. When epithelial cells grow, the negative tension produced by their division provokes a buckling instability. Several shapes are investigated: varicose, dilated, sinuous, or sausagelike. They are all found in pathologies of tracheal, renal tubes, or arteries. The final shape depends crucially on the mechanical parameters of the tissues: Young’s modulus, wall-to-lumen ratio, homeostatic pressure. We argue that since tissues must be in quasistatic mechanical equilibrium, abnormal shapes convey information as to what causes the pathology. We calculate a phase diagram of tubular instabilities which could be a helpful guide for investigating the underlying genetic regulation.

  15. Chondral Injury in Patellofemoral Instability

    PubMed Central

    Lustig, Sébastien; Servien, Elvire; Neyret, Philippe

    2014-01-01

    Objective: Patellofemoral instability is common and affects a predominantly young age group. Chondral injury occurs in up to 95%, and includes osteochondral fractures and loose bodies acutely and secondary degenerative changes in recurrent cases. Biomechanical abnormalities, such as trochlear dysplasia, patella alta, and increased tibial tuberosity-trochlear groove distance, predispose to both recurrent dislocations and patellofemoral arthrosis. Design: In this article, we review the mechanisms of chondral injury in patellofemoral instability, diagnostic modalities, the distribution of lesions seen in acute and episodic dislocation, and treatments for articular cartilage lesions of the patellofemoral joint. Results: Little specific evidence exists for cartilage treatments in patellofemoral instability. In general, the results of reparative and restorative procedures in the patellofemoral joint are inferior to those observed in other compartments of the knee. Conclusion: Given the increased severity of chondral lesions and progression to osteoarthritis seen with recurrent dislocations, careful consideration should be given to early stabilisation in patients with predisposing factors. PMID:26069693

  16. Segregation of the fragile-X mutation from an affected male: Evidence of unusual somatic instability in the FMR-1 locus

    SciTech Connect

    Kambouris, M.; Bluhm, D.; Feldman, G.L.

    1994-09-01

    Fragile X syndrome is associated with an unstable CGG-repeat in the FMR-1 gene. There are few reports of affected males transmitting the FMR-1 gene to offspring. We report a family in which the paternal grandfather has an unusual FMR-1 pattern, with allele sizes ranging from premutation to full mutation. The family was initially ascertained because of a diagnosis of fragile X syndrome in this individual`s grandson. For Southern blot analyses, the samples were digested with Pst 1 and hybridized to the pE5.1 probe or digested with HindIII and hybridized to the StB12.3 probe. The proband had a high molecular weight allele, indicating significant amplifications, and an abnormal methylation pattern, consistent with a full mutation. His twin sister, who also had features of fragile X syndrome, had a similar pattern in addition to her normal allele (30 repeats). Their mother had one normal allele (33 repeats) and a premutation allele (>130 CGG repeats), with a normal methylation pattern. The maternal grandmother had alleles of 32 and 33 CGG repeats. These findings support the hypothesis that transmission of a full fragile-X mutation does not occur through a male, even if that male has clincial and molecular evidence of a full mutation. Gonadal mosaicism is an alternative explanation. Thus, an affected male with extensive FMR-1 somatic mosaicism transmitted a large premutation to his daughter, who in turn transmitted a full mutation to both of her offspring. FMR-1 protein studies on this individual, which are in progress, should help to determine the correlation, if any, of the molecular findings with the phenotypic effects.

  17. Plastic condoms.

    PubMed

    1968-01-01

    Only simple equipment, simple technology and low initial capital investment are needed in their manufacture. The condoms can be made by people who were previously unskilled or only semi-skilled workers. Plastic condoms differ from those made of latex rubber in that the nature of the plastic film allows unlimited shelf-life. Also, the plastic has a higher degree of lubricity than latex rubber; if there is a demand for extra lubrication in a particular market, this can be provided. Because the plastic is inert, these condoms need not be packaged in hermetically sealed containers. All these attributes make it possible to put these condoms on the distributors' shelves in developing countries competitively with rubber condoms. The shape of the plastic condom is based on that of the lamb caecum, which has long been used as luxury-type condom. The plastic condom is made from plastic film (ethylene ethyl acrilate) of 0.001 inch (0.0254 mm.) thickness. In addition, a rubber ring is provided and sealed into the base of the condom for retention during coitus. The advantage of the plastic condom design and the equipment on which it is made is that production can be carried out either in labour-intensive economy or with varying degrees of mechanization and automation. The uniform, finished condom if made using previously untrained workers. Training of workers can be done in a matter of hours on the two machines which are needed to produce and test the condoms. The plastic film is provided on a double wound roll, and condom blanks are prepared by means of a heat-sealing die on the stamping machine. The rubber rings are united to the condom blanks on an assembly machine, which consists of a mandrel and heat-sealing equipment to seal the rubber ring to the base of the condom. Built into the assembly machine is a simple air-testing apparatus that can detect the smallest pinhole flaw in a condom. The manufacturing process is completed by unravelling the condom from the assembly

  18. Electron heat flux instability

    NASA Astrophysics Data System (ADS)

    Saeed, Sundas; Sarfraz, M.; Yoon, P. H.; Lazar, M.; Qureshi, M. N. S.

    2017-02-01

    The heat flux instability is an electromagnetic mode excited by a relative drift between the protons and two-component core-halo electrons. The most prominent application may be in association with the solar wind where drifting electron velocity distributions are observed. The heat flux instability is somewhat analogous to the electrostatic Buneman or ion-acoustic instability driven by the net drift between the protons and bulk electrons, except that the heat flux instability operates in magnetized plasmas and possesses transverse electromagnetic polarization. The heat flux instability is also distinct from the electrostatic counterpart in that it requires two electron species with relative drifts with each other. In the literature, the heat flux instability is often called the 'whistler' heat flux instability, but it is actually polarized in the opposite sense to the whistler wave. This paper elucidates all of these fundamental plasma physical properties associated with the heat flux instability starting from a simple model, and gradually building up more complexity towards a solar wind-like distribution functions. It is found that the essential properties of the instability are already present in the cold counter-streaming electron model, and that the instability is absent if the protons are ignored. These instability characteristics are highly reminiscent of the electron firehose instability driven by excessive parallel temperature anisotropy, propagating in parallel direction with respect to the ambient magnetic field, except that the free energy source for the heat flux instability resides in the effective parallel pressure provided by the counter-streaming electrons.

  19. Plastic Bronchitis.

    PubMed

    Rubin, Bruce K

    2016-09-01

    Plastic bronchitis is an uncommon and probably underrecognized disorder, diagnosed by the expectoration or bronchoscopic removal of firm, cohesive, branching casts. It should not be confused with purulent mucous plugging of the airway as seen in patients with cystic fibrosis or bronchiectasis. Few medications have been shown to be effective and some are now recognized as potentially harmful. Current research directions in plastic bronchitis research include understanding the genetics of lymphatic development and maldevelopment, determining how abnormal lymphatic malformations contribute to cast formation, and developing new treatments.

  20. Cultural Diversity, Economic Development and Societal Instability

    PubMed Central

    Nettle, Daniel; Grace, James B.; Choisy, Marc; Cornell, Howard V.; Guégan, Jean-François; Hochberg, Michael E.

    2007-01-01

    Background Social scientists have suggested that cultural diversity in a nation leads to societal instability. However, societal instability may be affected not only by within-nation or α diversity, but also diversity between a nation and its neighbours or β diversity. It is also necessary to distinguish different domains of diversity, namely linguistic, ethnic and religious, and to distinguish between the direct effects of diversity on societal instability, and effects that are mediated by economic conditions. Methodology/Principal Findings We assembled a large cross-national dataset with information on α and β cultural diversity, economic conditions, and indices of societal instability. Structural equation modeling was used to evaluate the direct and indirect effects of cultural diversity on economics and societal stability. Results show that different types and domains of diversity have interacting effects. As previously documented, linguistic α diversity has a negative effect on economic performance, and we show that it is largely through this economic mechanism that it affects societal instability. For β diversity, the higher the linguistic diversity among nations in a region, the less stable the nation. But, religious β diversity has the opposite effect, reducing instability, particularly in the presence of high linguistic diversity. Conclusions Within-nation linguistic diversity is associated with reduced economic performance, which, in turn, increases societal instability. Nations which differ linguistically from their neighbors are also less stable. However, religious diversity between neighboring nations has the opposite effect, decreasing societal instability. PMID:17895970

  1. Cultural diversity, economic development and societal instability.

    PubMed

    Nettle, Daniel; Grace, James B; Choisy, Marc; Cornell, Howard V; Guégan, Jean-François; Hochberg, Michael E

    2007-09-26

    Social scientists have suggested that cultural diversity in a nation leads to societal instability. However, societal instability may be affected not only by within-nation or alpha diversity, but also diversity between a nation and its neighbours or beta diversity. It is also necessary to distinguish different domains of diversity, namely linguistic, ethnic and religious, and to distinguish between the direct effects of diversity on societal instability, and effects that are mediated by economic conditions. We assembled a large cross-national dataset with information on alpha and beta cultural diversity, economic conditions, and indices of societal instability. Structural equation modeling was used to evaluate the direct and indirect effects of cultural diversity on economics and societal stability. Results show that different types and domains of diversity have interacting effects. As previously documented, linguistic alpha diversity has a negative effect on economic performance, and we show that it is largely through this economic mechanism that it affects societal instability. For beta diversity, the higher the linguistic diversity among nations in a region, the less stable the nation. But, religious beta diversity has the opposite effect, reducing instability, particularly in the presence of high linguistic diversity. Within-nation linguistic diversity is associated with reduced economic performance, which, in turn, increases societal instability. Nations which differ linguistically from their neighbors are also less stable. However, religious diversity between neighboring nations has the opposite effect, decreasing societal instability.

  2. Cultural diversity, economic development and societal instability

    USGS Publications Warehouse

    Nettle, D.; Grace, J.B.; Choisy, M.; Cornell, H.V.; Guegan, J.-F.; Hochberg, M.E.

    2007-01-01

    Background. Social scientists have suggested that cultural diversity in a nation leads to societal instability. However, societal instability may be affected not only by within-nation on ?? diversity, but also diversity between a nation and its neighbours or ?? diversity. It is also necessary to distinguish different domains of diversity, namely linguistic, ethnic and religious, and to distinguish between the direct effects of diversity on societal instability, and effects that are mediated by economic conditions. Methodology/Principal Findings. We assembled a large cross-national dataset with information on ?? and ?? cultural diversity, economic conditions, and indices of societal instability. Structural equation modeling was used to evaluate the direct and indirect effects of cultural diversity on economics and societal stability. Results show that different type and domains of diversity have interacting effects. As previously documented, linguistic ?? diversity has a negative effect on economic performance, and we show that it is largely through this economic mechanism that it affects societal instability. For ?? diversity, the higher the linguistic diversity among nations in a region, the less stable the nation. But, religious ?? diversity has the opposite effect, reducing instability, particularly in the presence of high linguistic diversity. Conclusions. Within-nation linguistic diversity is associated with reduced economic performance, which, in turn, increases societal instability. Nations which differ linguistically from their neighbors are also less stable. However, religious diversity between, neighboring nations has the opposite effect, decreasing societal instability.

  3. Spatio-temporal patterns of recurrent slope instabilities affecting undercut slopes in flysch: A dendrogeomorphic approach using broad-leaved trees

    NASA Astrophysics Data System (ADS)

    Šilhán, Karel; Pánek, Tomáš; Turský, Ondřej; Brázdil, Rudolf; Klimeš, Jan; Kašičková, Lucie

    2014-05-01

    The undercut slope of the Skalická Strážnice/Vrchy hill situated in the piedmont of the Carpathian Mountains (Czech Republic) is a regional landslide "hotspot", notorious for its repeated recent and historical sliding reactivations. We performed tree-ring analysis of a large number (n = 274) of broad-leaved trees to reconstruct the spatio-temporal patterns of landslide reactivation for a period spanning more than one hundred years (1884-2011). Although tree rings of broad-leaved trees are less-reliable archives of landslide activity than those of conifers, the application of a methodology based on the weighting of disturbance signals within eccentricity series generated a usable dataset of sliding activity affecting anisotropic flysch bedrock. Although some known landslide years could not be found (or were expressed by only weak signals) in the reconstructed dataset, the majority of landslide events reconstructed from the tree-ring series coincide with hydrometeorological data, revealing a correlation with heavy summer rainfalls lasting from two to ten days. The spatial distribution of landslide recurrence derived from the tree-ring records together with electrical resistivity tomography and a kinematic analysis of slope failures suggest a close link between the concentration of landslide activity and the presence of faulted or fractured flysch bedrock.

  4. Turbine instabilities: Case histories

    NASA Technical Reports Server (NTRS)

    Laws, C. W.

    1985-01-01

    Several possible causes of turbine rotor instability are discussed and the related design features of a wide range of turbomachinery types and sizes are considered. The instrumentation options available for detecting rotor instability and assessing its severity are also discussed.

  5. Nonlinear plastic modes in disordered solids.

    PubMed

    Gartner, Luka; Lerner, Edan

    2016-01-01

    We propose a theoretical framework within which a robust micromechanical definition of precursors to plastic instabilities, often termed soft spots, naturally emerges. They are shown to be collective displacements (modes) z[over ̂] that correspond to local minima of a barrier function b(z[over ̂]), which depends solely on inherent structure information. We demonstrate how some heuristic searches for local minima of b(z[over ̂]) can a priori detect the locus and geometry of imminent plastic instabilities with remarkable accuracy, at strains as large as γ_{c}-γ∼10^{-2} away from the instability strain γ_{c}. Our findings suggest that the a priori detection of the entire field of soft spots can be effectively carried out by a systematic investigation of the landscape of b(z[over ̂]).

  6. Linear analysis of incompressible Rayleigh-Taylor instability in solids

    NASA Astrophysics Data System (ADS)

    Piriz, A. R.; López Cela, J. J.; Tahir, N. A.

    2009-10-01

    The study of the linear stage of the incompressible Rayleigh-Taylor instability in elastic-plastic solids is performed by considering thick plates under a constant acceleration that is also uniform except for a small sinusoidal ripple in the horizontal plane. The analysis is carried out by using an analytical model based on the Newton second law and it is complemented with extensive two-dimensional numerical simulations. The conditions for marginal stability that determine the instability threshold are derived. Besides, the boundary for the transition from the elastic to the plastic regime is obtained and it is demonstrated that such a transition is not a sufficient condition for instability. The model yields complete analytical solutions for the perturbation amplitude evolution and reveals the main physical process that governs the instability. The theory is in general agreement with the numerical simulations and provides useful quantitative results. Implications for high-energy-density-physics experiments are also discussed.

  7. Linear analysis of incompressible Rayleigh-Taylor instability in solids.

    PubMed

    Piriz, A R; Cela, J J López; Tahir, N A

    2009-10-01

    The study of the linear stage of the incompressible Rayleigh-Taylor instability in elastic-plastic solids is performed by considering thick plates under a constant acceleration that is also uniform except for a small sinusoidal ripple in the horizontal plane. The analysis is carried out by using an analytical model based on the Newton second law and it is complemented with extensive two-dimensional numerical simulations. The conditions for marginal stability that determine the instability threshold are derived. Besides, the boundary for the transition from the elastic to the plastic regime is obtained and it is demonstrated that such a transition is not a sufficient condition for instability. The model yields complete analytical solutions for the perturbation amplitude evolution and reveals the main physical process that governs the instability. The theory is in general agreement with the numerical simulations and provides useful quantitative results. Implications for high-energy-density-physics experiments are also discussed.

  8. Plastics Technician.

    ERIC Educational Resources Information Center

    Ohio State Univ., Columbus. Center on Education and Training for Employment.

    This document contains 16 units to consider for use in a tech prep competency profile for the occupation of plastics technician. All the units listed will not necessarily apply to every situation or tech prep consortium, nor will all the competencies within each unit be appropriate. Several units appear within each specific occupation and would…

  9. Plastics Technician.

    ERIC Educational Resources Information Center

    Ohio State Univ., Columbus. Center on Education and Training for Employment.

    This document contains 16 units to consider for use in a tech prep competency profile for the occupation of plastics technician. All the units listed will not necessarily apply to every situation or tech prep consortium, nor will all the competencies within each unit be appropriate. Several units appear within each specific occupation and would…

  10. Neurocardiovascular Instability and Cognition

    PubMed Central

    O’Callaghan, Susan; Kenny, Rose Anne

    2016-01-01

    Neurocardiovascular instability (NCVI) refers to abnormal neural control of the cardiovascular system affecting blood pressure and heart rate behavior. Autonomic dysfunction and impaired cerebral autoregulation in aging contribute to this phenomenon characterized by hypotension and bradyarrhythmia. Ultimately, this increases the risk of falls and syncope in older people. NCVI is common in patients with neurodegenerative disorders including dementia. This review discusses the various syndromes that characterize NCVI icluding hypotension, carotid sinus hypersensitivity, postprandial hypotension and vasovagal syncope and how they may contribute to the aetiology of cognitive decline. Conversely, they may also be a consequence of a common neurodegenerative process. Regardless, recognition of their association is paramount in optimizing management of these patients. PMID:27505017

  11. Field evaluation of spatial repellency of metofluthrin-impregnated latticework plastic strips against Aedes aegypti (L.) and analysis of environmental factors affecting its efficacy in My Tho City, Tien Giang, Vietnam.

    PubMed

    Kawada, Hitoshi; Iwasaki, Tomonori; LE Loan, Luu; Tien, Tran Khanh; Mai, Nguyen Thi Nhu; Shono, Yoshinori; Katayama, Yasuyuki; Takagi, Masahiro

    2006-12-01

    Spatial repellency of metofluthrin-impregnated polyethylene latticework plastic strips against Aedes aegypti mosquitoes was evaluated. Analysis of environmental factors affecting the efficacy of these strips, such as room temperature, humidity, and house structure, was performed in a residential area in My Tho City, Tien Giang Province, Vietnam. Treatment with the strips at the rate of 1 strip per 2.6-5.52 m(2) (approximately 600 mg per 2.6-5.52 m(2)) reduced the collection of Ae. aegypti resting inside the houses for at least eight weeks. Multiple regression analysis indicated that both increase in the average room temperature and decrease in the area of openings in the rooms that were treated with the strips positively affected the spatial repellency of metofluthrin.

  12. GLASS FIBER REINFORCED PLASTICS,

    DTIC Science & Technology

    Contents: Fibrous glass fillers Binders used in the glass plastic industry Method of manufacturing glass plastics and glass plastic articles Properties of fiberglass Primary areas for use of glass fibre reinforced plastics

  13. Instability of rectangular jets

    NASA Technical Reports Server (NTRS)

    Tam, Christopher K. W.; Thies, Andrew T.

    1992-01-01

    The instability of rectangular jets is investigated using a vortex sheet model. It is shown that such jets support four linearly independent families of instability waves. Within each family there are infinitely many modes. A way to classify these modes according to the characteristics of their mode shapes or eigenfunctions is proposed. A parametric study of the instability wave characteristics has been carried out. A sample of the numerical results is reported here. It is found that the first and third modes of each instability wave family are corner modes. The pressure fluctuations associated with these instability waves are localized near the corners of the jet. The second mode, however, is a center mode with maximum fluctuations concentrated in the central portion of the jet flow. The center mode has the largest spatial growth rate. It is anticipated that as the instability waves propagate downstream the center mode would emerge as the dominant instability of the jet.

  14. Instability of rectangular jets

    NASA Technical Reports Server (NTRS)

    Tam, Christopher K. W.; Thies, Andrew T.

    1992-01-01

    The instability of rectangular jets is investigated using a vortex sheet model. It is shown that such jets support four linearly independent families of instability waves. Within each family there are infinitely many modes. A way to classify these modes according to the characteristics of their mode shapes or eigenfunctions is proposed. A parametric study of the instability wave characteristics has been carried out. A sample of the numerical results is reported here. It is found that the first and third modes of each instability wave family are corner modes. The pressure fluctuations associated with these instability waves are localized near the corners of the jet. The second mode, however, is a center mode with maximum fluctuations concentrated in the central portion of the jet flow. The center mode has the largest spatial growth rate. It is anticipated that as the instability waves propagate downstream the center mode would emerge as the dominant instability of the jet.

  15. MIX and Instability Growth from Oblique Shock

    SciTech Connect

    Molitoris, J D; Batteux, J D; Garza, R G; Tringe, J W; Souers, P C; Forbes, J W

    2011-07-22

    We have studied the formation and evolution of shock-induced mix resulting from interface features in a divergent cylindrical geometry. In this research a cylindrical core of high-explosive was detonated to create an oblique shock wave and accelerate the interface. The interfaces studied were between the high-explosive/aluminum, aluminum/plastic, and finally plastic/air. Pre-emplaced surface features added to the aluminum were used to modify this interface. Time sequence radiographic imaging quantified the resulting instability formation from the growth phase to over 60 {micro}s post-detonation. Thus allowing the study of the onset of mix and evolution to turbulence. The plastic used here was porous polyethylene. Radiographic image data are compared with numerical simulations of the experiments.

  16. Experimental Observation of Sheath-presheath Instabilities

    NASA Astrophysics Data System (ADS)

    Kella, Vara Prasad; Ghosh, Joydeep; Sharma, Devendra; Chattopadhyay, Prabal K.

    2016-10-01

    Instabilities in the Sheath-presheath regime are most important phenomena that can affect the plasma-wall interaction. These instabilities can modify the particle flow velocities and distribution functions in that regime. In this present work, instabilities exists in the sheath-presheath in a low temperature plasma are observed. Experiments are carried in single ion species argon plasma and multi ion species Ar-He plasma. Experiments are carried in a stainless steel chamber with filament discharge plasma. Sheath is produced around a stainless steel grid at center of the chamber. Fluctuations from the grid and cylindrical Langmuir probe are recorded. Langmuir probe is used to get the floating potential fluctuations from presheath and bulk plasma as well. In single ion species argon plasma, there are two instabilities observed namely ion-ion counter streaming instability through mesh grid and ion acoustic instability respectively arises in the presheath. In case of multi-ion Ar-He plasma, two stream instability also explored. The neutral pressure threshold for the sustain of these instabilities also observed.

  17. Diffusion and emissions of 1,3-dichloro propene in Florida sandy soil in microplots affected by soil moisture, organic matter, and plastic film.

    PubMed

    Thomas, John E; Allen, L Hartwell; McCormack, Leslie A; Vu, Joseph C; Dickson, Donald W; Ou, Li-Tse

    2004-04-01

    The main objective of this study was to determine the influence of soil moisture, organic matter amendment and plastic cover (a virtually impermeable film, VIF) on diffusion and emissions of (Z)- and (E)-1,3-dichloropropene (1,3-D) in microplots of Florida sandy soil (Arredondo fine sand). Upward diffusion of the two isomers in the Arredondo soil without a plastic cover was greatly influenced by soil-water content and (Z)-1,3-D diffused faster than (E)-1,3-D. In less than 5 h after 1,3-D injection to 30 cm depth, (Z)- and (E)-1,3-D in air dry soil had diffused to a 10 cm depth, whereas diffusion for the two isomers was negligible in near-water-saturated soil, even 101 h after injection. The diffusion rate of (Z)- and (E)-1,3-D in near-field-capacity soil was between the rates in the two water regimes. Yard waste compost (YWC) amendment greatly reduced diffusion of (Z)- and (E)-1,3-D, even in air-dry soil. Although upward diffusion of (Z)- and (E)-1,3-D in soil with VIF cover was slightly less than in the corresponding bare soil; the cover promoted retention of vapors of the two isomers in soil pore air in the shallow subsurface. More (Z)-1,3-D vapor was found initially in soil pore air than (E)-1,3-D although the difference declined thereafter. As a result of rapid upward movement in air-dry bare soil, (Z)- and (E)-1,3-D were rapidly volatilized into the atmosphere, but emissions from the near-water-saturated soil were minimal. Virtually impermeable film and YWC amendment retarded emissions. This study indicated that adequate soil water in this sandy soil is needed to prevent rapid emissions, but excess soil water slows diffusion of (Z)- and (E)-1,3-D. Thus, management for optimum water in soil is critical for pesticidal efficacy and the environment.

  18. Plastic bronchitis

    PubMed Central

    Singhi, Anil Kumar; Vinoth, Bharathi; Kuruvilla, Sarah; Sivakumar, Kothandam

    2015-01-01

    Plastic bronchitis, a rare but serious clinical condition, commonly seen after Fontan surgeries in children, may be a manifestation of suboptimal adaptation to the cavopulmonary circulation with unfavorable hemodynamics. They are ominous with poor prognosis. Sometimes, infection or airway reactivity may provoke cast bronchitis as a two-step insult on a vulnerable vascular bed. In such instances, aggressive management leads to longer survival. This report of cast bronchitis discusses its current understanding. PMID:26556975

  19. Stability of α-tocopherol in freeze-dried sugar-protein-oil emulsion solids as affected by water plasticization and sugar crystallization.

    PubMed

    Zhou, Yankun; Roos, Yrjö H

    2012-08-01

    Water plasticization of sugar-protein encapsulants may cause structural changes and decrease the stability of encapsulated compounds during storage. The retention of α-tocopherol in freeze-dried lactose-milk protein-oil, lactose-soy protein-oil, trehalose-milk protein-oil, and trehalose-soy protein-oil systems at various water activities (a(w)) and in the presence of sugar crystallization was studied. Water sorption was determined gravimetrically. Glass transition and sugar crystallization were studied using differential scanning calorimetry and the retention of α-tocopherol spectrophotometrically. The loss of α-tocopherol followed lipid oxidation, but the greatest stability was found at 0 a(w) presumably because of α-tocopherol immobilization at interfaces and consequent reduction in antioxidant activity. A considerable loss of α-tocopherol coincided with sugar crystallization. The results showed that glassy matrices may protect encapsulated α-tocopherol; however, its role as an antioxidant at increasing aw accelerated its loss. Sugar crystallization excluded the oil-containing α-tocopherol from the protecting matrices and exposed it to surroundings, which decreased the stability of α-tocopherol.

  20. Confinement effects on electroconvective instability.

    PubMed

    Andersen, Mathias B; Wang, Karen M; Schiffbauer, Jarrod; Mani, Ali

    2017-03-01

    We present an analysis of hydrodynamic effects in systems involving ion transport from an aqueous electrolyte to an ion-selective surface. These systems are described by the Poisson-Nernst-Planck and Navier-Stokes equations. Historically, such systems were modeled by one-dimensional geometries with spatial coordinate in the direction of transport and normal to the ion-selective surface. Rubinstein and Zaltzman [JFM 579, 173-226 (2007)] showed that when such systems are unbounded in the transverse directions, a hydrodynamic instability can occur. This instability, referred to as electroconvective instability, leads to advective mixing, which results in overlimiting transport rates significantly beyond what is predicted from one-dimensional models. In this study, we present an analysis of electroconvection in confined systems, considering a broad range of applications including microfluidic systems and porous media. Our analysis reveals that full confinement in the transverse directions significantly suppresses electroconvection and overlimiting current. However, when at least one transverse direction allows for flow escape, such as in thin but wide channels or in porous media, the onset of instability is only weakly affected by confinement. We will also present a review of relevant literature and discuss how the present study resolves the contradictory contrasts between the results of recent work on this topic. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. Radiative heat transport instability in a laser produced inhomogeneous plasma

    SciTech Connect

    Bychenkov, V. Yu.; Rozmus, W.

    2015-08-15

    A laser produced high-Z plasma in which an energy balance is achieved due to radiation emission and radiative heat transfer supports ion acoustic instability. A linear dispersion relation is derived, and instability is compared to the radiation cooling instability [R. G. Evans, Plasma Phys. Controlled Fusion 27, 751 (1985)]. Under conditions of indirect drive fusion experiments, the driving term for the instability is the radiative heat flux and, in particular, the density dependence of the radiative heat conductivity. A specific example of thermal Bremsstrahlung radiation source has been considered. This instability may lead to plasma jet formation and anisotropic x-ray generation, thus affecting inertial confinement fusion related experiments.

  2. Joint Instability and Osteoarthritis

    PubMed Central

    Blalock, Darryl; Miller, Andrew; Tilley, Michael; Wang, Jinxi

    2015-01-01

    Joint instability creates a clinical and economic burden in the health care system. Injuries and disorders that directly damage the joint structure or lead to joint instability are highly associated with osteoarthritis (OA). Thus, understanding the physiology of joint stability and the mechanisms of joint instability-induced OA is of clinical significance. The first section of this review discusses the structure and function of major joint tissues, including periarticular muscles, which play a significant role in joint stability. Because the knee, ankle, and shoulder joints demonstrate a high incidence of ligament injury and joint instability, the second section summarizes the mechanisms of ligament injury-associated joint instability of these joints. The final section highlights the recent advances in the understanding of the mechanical and biological mechanisms of joint instability-induced OA. These advances may lead to new opportunities for clinical intervention in the prevention and early treatment of OA. PMID:25741184

  3. Parametric instabilities in large nonuniform laser plasmas

    SciTech Connect

    Baldis, H.A.; Montgomery, D.S.; Moody, J.D.; Estabrook, K.G.; Berger, R.L.; Kruer, W.L.; Labaune, C.; Batha, S.H.

    1992-09-01

    The study of parametric instabilities in laser plasmas is of vital importance for inertial confinement fusion (ICF). The long scale-length plasma encountered in the corona of an ICF target provides ideal conditions for the growth of instabilities such as stimulated Brillouin scattering (SBS), stimulated Raman scattering (SRS), and filamentation. These instabilities can have detrimental effects in ICF and their characterization and understanding is of importance. Scattering instabilities are driven through a feedback loop by which the beating between the electromagnetic EM fields of the laser and the scattered light matches the frequency of a local longitudinal mode of the plasma. Any process which interferes with the coherence of this mechanism can substantially alter the behavior of the instability. Of particular interest is the study of laser beam smoothing techniques on parametric instabilities. These techniques are used to improve irradiation uniformity which can suppress hydrodynamic instabilities. Laser beam smoothing techniques have the potential to control the scattering level from parametric instabilities since they provide not only a smoother laser intensity distribution, but also reduced coherence. Beam smoothing techniques that affect the growth of parametric instabilities include spatial smoothing and temporal smoothing by laser bandwidth. Spatial smoothing modifies the phase fronts and temporal distribution of intensities in the focal volume. The transverse intensity spectrum is shifted towards higher spatial wavenumber and can significantly limit the growth of filamentation. Temporal smoothing reduces the coherence time and consequently limits the growth time. Laser bandwidth is required for most smoothing techniques, and can have an independent effect on the instabilities as well.

  4. Ordinary electromagnetic mode instability

    NASA Technical Reports Server (NTRS)

    Cheng, C. Z.

    1974-01-01

    The instability of the ordinary electromagnetic mode propagating perpendicular to an external magnetic field is studied for a single-species plasma with ring velocity distribution. The marginal instability boundaries for both the purely growing mode and the propagating growing modes are calculated from the instability criteria. The dispersion characteristics for various sets of plasma parameters are also given. The typical growth rates are of the order of the cyclotron frequency.

  5. Instability in Rotating Machinery

    NASA Technical Reports Server (NTRS)

    1985-01-01

    The proceedings contain 45 papers on a wide range of subjects including flow generated instabilities in fluid flow machines, cracked shaft detection, case histories of instability phenomena in compressors, turbines, and pumps, vibration control in turbomachinery (including antiswirl techniques), and the simulation and estimation of destabilizing forces in rotating machines. The symposium was held to serve as an update on the understanding and control of rotating machinery instability problems.

  6. Generalities on combustion instabilities

    NASA Astrophysics Data System (ADS)

    Kuentzmann, Paul

    The main manifestations of combustion instabilities are reviewed, and the specific characteristics of instabilities in solid-propellant rocket engines are analyzed, with the Minuteman III third-stage engine and the SRB engine of Titan 34 D considered as examples. The main approaches for predicting combustion instabilities are discussed, including the linear approach based on the acoustic balance, the nonlinear mode-coupling approach, and the nonlinear approach using numerical calculation. Projected directions for future research are also examined.

  7. Root treatment with rhizobacteria antagonistic to Phytophthora blight affects anthracnose occurrence, ripening, and yield of pepper fruit in the plastic house and field.

    PubMed

    Sang, Mee Kyung; Kim, Jeong Do; Kim, Beom Seok; Kim, Ki Deok

    2011-06-01

    We previously selected rhizobacterial strains CCR04, CCR80, GSE09, ISE13, and ISE14, which were antagonistic to Phytophthora blight of pepper. In this study, we investigated the effects of root treatment of rhizobacteria on anthracnose occurrence, ripening, and yield of pepper fruit in the plastic house and field in 2008 and 2009. We also examined the effects of volatiles produced by the strains on fruit ripening and on mycelial growth and spore development of Colletotrichum acutatum and Phytophthora capsici in the laboratory, identifying the volatile compounds by gas chromatography-mass spectrometry (GC-MS). In the house tests, all strains significantly (P < 0.05) reduced anthracnose incidence on pepper fruit; strains GSE09 and ISE14 consistently produced higher numbers of pepper fruit or increased the fresh weight of red fruit more than the controls in both years. In the field tests, all strains significantly (P < 0.05) reduced anthracnose occurrence on either green or red pepper fruit; strain ISE14 consistently produced higher numbers or increased fresh weights of red fruit more than the controls in both years. In the laboratory tests, volatiles produced by strains GSE09 and ISE13 only stimulated maturation of pepper fruit from green (unripe) to red (ripe) fruit; the volatiles of certain strains inhibited the growth and development of C. acutatum and P. capsici. On the other hand, GC-MS analysis of volatiles of strains GSE09 and ISE13 revealed 17 distinct compounds in both strains, including decane, dodecane, 1,3-di-tert-butylbenzene, tetradecane, 2,4-di-tert-butylphenol, and hexadecane. Among these compounds, 2,4-di-tert-butylphenol only stimulated fruit ripening and inhibited growth and development of the pathogens. Taken together, strains GSE09 and ISE14 effectively reduced anthracnose occurrence and stimulated pepper fruit ripening and yield, possibly via bacterial volatiles. Therefore, these two strains could be potential agents for controlling Phytophthora

  8. Influence of ion streaming instabilities on transport near plasma boundaries

    NASA Astrophysics Data System (ADS)

    Baalrud, Scott D.

    2016-04-01

    Plasma boundary layers are susceptible to electrostatic instabilities driven by ion flows in presheaths and, when present, these instabilities can influence transport. In plasmas with a single species of positive ion, ion-acoustic instabilities are expected under conditions of low pressure and large electron-to-ion temperature ratio ({{T}e}/{{T}i}\\gg 1 ). In plasmas with two species of positive ions, ion-ion two-stream instabilities can also be excited. The stability phase-space is characterized using the Penrose criterion and approximate linear dispersion relations. Predictions for how these instabilities affect ion and electron transport in presheaths, including rapid thermalization due to instability-enhanced collisions and an instability-enhanced ion-ion friction force, are briefly reviewed. Recent experimental tests of these predictions are discussed along with research needs required for further validation. The calculated stability boundaries provide a guide to determine the experimental conditions at which these effects can be expected.

  9. Metabolic plasticity of human T cells: Preserved cytokine production under glucose deprivation or mitochondrial restriction, but 2-deoxy-glucose affects effector functions.

    PubMed

    Renner, Kathrin; Geiselhöringer, Anna-Lena; Fante, Matthias; Bruss, Christina; Färber, Stephanie; Schönhammer, Gabriele; Peter, Katrin; Singer, Katrin; Andreesen, Reinhard; Hoffmann, Petra; Oefner, Peter; Herr, Wolfgang; Kreutz, Marina

    2015-09-01

    The strong link between T-cell metabolism and effector functions is well characterized in the murine system but hardly investigated in human T cells. Therefore, we analyzed glycolytic and mitochondrial activity in correlation to function in activated human CD4 and CD8 T cells. Glycolysis was barely detectable upon stimulation but accelerated beyond 24 h, whereas mitochondrial activity was elevated immediately in both T-cell populations. Glucose deprivation or mitochondrial restriction reduced proliferation, had only a transient impact on "on-blast formation" and no impact on viability, IFN-γ, IL-2, IL-4, and IL-10 production, whereas TNF was reduced. Similar results were obtained in bulk T cells and T-cell subsets. Elevated respiration under glucose restriction demonstrated metabolic flexibility. Administration of the glycolytic inhibitor 2-deoxy-glucose suppressed both glycolysis and respiration and exerted a strong impact on cytokine production that persisted for IFN-γ after removal of 2-deoxy-glucose. Taken together, glycolytic or mitochondrial restriction alone compromised proliferation of human T cells, but barely affected their effector functions. In contrast, effector functions were severely affected by 2-deoxy-glucose treatment. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. Treatment of hip instability.

    PubMed

    Robbins, G M; Masri, B A; Garbuz, D S; Greidanus, N; Duncan, C P

    2001-10-01

    Instability after total hip arthroplasty is a major source of patient morbidity, second only to aseptic loosening. Certain patient groups have been identified as having a greater risk of instability, including patients undergoing revision arthroplasty as early or late treatment for proximal femoral fractures.

  11. Finite temperature mechanical instability in disordered lattices

    NASA Astrophysics Data System (ADS)

    Zhang, Leyou; Mao, Xiaoming

    Mechanical instability takes different forms in various ordered and disordered systems, and little is known about how thermal fluctuations affect different classes of mechanical instabilities. We develop an analytic theory involving renormalization of rigidity and coherent potential approximation that can be used to understand finite-temperature mechanical stabilities in various disordered systems. We used this theory to study two disordered lattices: randomly diluted triangular lattice and randomly braced square lattice. These two lattices belong to two different universality classes as they approach mechanical instability at T = 0 . We show that thermal fluctuations stabilize both lattices. In particular, the triangular lattice displays a critical regime in which the shear modulus scales as G ~T 1 / 2 , whereas the square lattice shows G ~T 2 / 3 . We discuss generic scaling laws for finite T mechanical instabilities and relate to experimental systems including jamming and glass transitions.

  12. The Future of Plastic Surgery: Surgeon's Perspective.

    PubMed

    Ozturk, Sinan; Karagoz, Huseyin; Zor, Fatih

    2015-11-01

    Since the days of Sushruta, innovation has shaped the history of plastic surgery. Plastic surgeons have always been known as innovators or close followers of innovations. With this descriptive international survey study, the authors aimed to evaluate the future of plastic surgeons by analyzing how plastic surgery and plastic surgeons will be affected by new trends in medicine. Aesthetic surgery is the main subclass of plastic surgery thought to be the one that will change the most in the future. Stem cell therapy is considered by plastic surgeons to be the most likely "game changer." Along with changes in surgery, plastic surgeons also expect changes in plastic surgery education. The most approved assumption for the future of plastic surgery is, "The number of cosmetic nonsurgical procedures will increase in the future." If surgeons want to have better outcomes in their practice, they must at least be open minded for innovations if they do not become innovators themselves. Besides the individual effort of each surgeon, international and local plastic surgery associations should develop new strategies to adopt these innovations in surgical practice and education.

  13. Experimental observations of turbulent mixing due to Kelvin-Helmholtz instability on the OMEGA Laser Facility

    SciTech Connect

    Smalyuk, V. A.; Hansen, J. F.; Hurricane, O. A.; Langstaff, G.; Martinez, D.; Park, H.-S.; Raman, K.; Remington, B. A.; Robey, H. F.; Schilling, O.; Wallace, R.; Elbaz, Y.; Shimony, A.; Shvarts, D.; Di Stefano, C.; Drake, R. P.; Marion, D.; Krauland, C. M.; Kuranz, C. C.

    2012-09-15

    Shear-flow, Kelvin-Helmholtz (KH) turbulent mixing experiments were performed on the OMEGA Laser Facility [Boehly et al., Opt. Commun. 133, 495 (1997)] in which laser-driven shock waves propagated through a low-density plastic foam placed on top of a higher-density plastic foil. The plastic foil was comprised a thin iodine-doped plastic tracer layer bonded on each side to an undoped density-matched polyamide-imide plastic. Behind the shock front, lower-density foam plasma flowed over the higher-density plastic plasma, such that the interface between the foam and plastic was KH unstable. The initial perturbations consisted of pre-imposed, sinusoidal 2D perturbations, and broadband 3D perturbations due to surface roughness at the interface between the plastic and foam. KH instability growth was measured using side-on radiography with a point-projection 5-keV vanadium backlighter. Time-integrated images were captured on D-8 x-ray film. Spatial density profiles of iodine-doped plastic mixed with foam were inferred using x-ray radiographs. The mixing layer ensuing from the KH instability with layer width up to {approx}100 {mu}m was observed at a location {approx}1 mm behind the shock front. The measured mixing layer width was in good agreement with predictions based on a simple self-similar model of KH instability growth using an estimate of the shear velocity obtained from numerical simulations of the experiments.

  14. Buckling instability in arteries.

    PubMed

    Vandiver, Rebecca M

    2015-04-21

    Arteries can become tortuous in response to abnormal growth stimuli, genetic defects and aging. It is suggested that a buckling instability is a mechanism that might lead to artery tortuosity. Here, the buckling instability in arteries is studied by examining asymmetric modes of bifurcation of two-layer cylindrical structures that are residually stressed. These structures are loaded by an axial force, internal pressure and have nonlinear, anisotropic, hyperelastic responses to stresses. Strain-softening and reduced opening angle are shown to lower the critical internal pressure leading to buckling. In addition, the ratio of the media thickness to the adventitia thickness is shown to have a dramatic impact on arterial instability.

  15. Plastic in north sea fish.

    PubMed

    Foekema, Edwin M; De Gruijter, Corine; Mergia, Mekuria T; van Franeker, Jan Andries; Murk, Albertinka J; Koelmans, Albert A

    2013-08-06

    To quantify the occurrence of ingested plastic in fish species caught at different geographical positions in the North Sea, and to test whether the fish condition is affected by ingestion of plastics, 1203 individual fish of seven common North Sea species were investigated: herring, gray gurnard, whiting, horse mackerel, haddock, atlantic mackerel, and cod. Plastic particles were found in 2.6% of the examined fish and in five of the seven species. No plastics were found in gray gurnard and mackerel. In most cases, only one particle was found per fish, ranging in size from 0.04 to 4.8 mm. Only particles larger than 0.2 mm, being the diameter of the sieve used, were considered for the data analyses, resulting in a median particle size of 0.8 mm. The frequency of fish with plastic was significantly higher (5.4%) in the southern North Sea, than in the northern North Sea above 55°N (1.2%). The highest frequency (>33%) was found in cod from the English Channel. In addition, small fibers were initially detected in most of the samples, but their abundance sharply decreased when working under special clean air conditions. Therefore, these fibers were considered to be artifacts related to air born contamination and were excluded from the analyses. No relationship was found between the condition factor (size-weight relationship) of the fish and the presence of ingested plastic particles.

  16. Convective Instabilities in Liquid Foams

    NASA Technical Reports Server (NTRS)

    Veretennikov, Igor; Glazier, James A.

    2004-01-01

    The main goal of this work is to better understand foam behavior both on the Earth and in microgravity conditions and to determine the relation between a foam's structure and wetness and its rheological properties. Our experiments focused on the effects of the bubble size distribution (BSD) on the foam behavior under gradual or stepwise in the liquid flow rate and on the onset of the convective instability. We were able to show experimentally, that the BSD affects foam rheology very strongly so any theory must take foam texture into account.

  17. The genetics of phenotypic plasticity. XI. Joint evolution of plasticity and dispersal rate

    PubMed Central

    Scheiner, Samuel M; Barfield, Michael; Holt, Robert D

    2012-01-01

    In a spatially heterogeneous environment, the rate at which individuals move among habitats affects whether selection favors phenotypic plasticity or genetic differentiation, with high dispersal rates favoring trait plasticity. Until now, in theoretical explorations of plasticity evolution, dispersal rate has been treated as a fixed, albeit probabilistic, characteristic of a population, raising the question of what happens when the propensity to disperse and trait plasticity are allowed to evolve jointly. We examined the effects of their joint evolution on selection for plasticity using an individual-based computer simulation model. In the model, the environment consisted of a linear gradient of 50 demes with dispersal occurring either before or after selection. Individuals consisted of loci whose phenotypic expression either are affected by the environment (plastic) or are not affected (nonplastic), plus a locus determining the propensity to disperse. When dispersal rate and trait plasticity evolve jointly, the system tends to dichotomous outcomes of either high trait plasticity and high dispersal, or low trait plasticity and low dispersal. The outcome strongly depended on starting conditions, with high trait plasticity and dispersal favored when the system started at high values for either trait plasticity or dispersal rate (or both). Adding a cost of plasticity tended to drive the system to genetic differentiation, although this effect also depended on initial conditions. Genetic linkage between trait plasticity loci and dispersal loci further enhanced this strong dichotomy in evolutionary outcomes. All of these effects depended on organismal life history pattern, and in particular whether selection occurred before or after dispersal. These results can explain why adaptive trait plasticity is less common than might be expected. PMID:22957203

  18. Genomic Instability Induced by High and Low Let Ionizing Radiation

    NASA Astrophysics Data System (ADS)

    Limoli, C. L.; Ponnaiya, B.; Corcoran, J. J.; Giedzinski, E.; Kaplan, M. I.; Hartmann, A.; Morgan, W. F.

    Genomic instability is the increased rate of acquisition of alterations in the mammalian genome, and includes such diverse biological endpoints as chromosomal destabilization, aneuploidy, micronucleus formation, sister chromatid exchange, gene mutation and amplification, variations in colony size, reduced plating efficiency, and cellular transformation. Because these multiple endpoints persist long after initial radiation exposure, genomic instability has been proposed to operate as a driving force contributing to genetic plasticity and carcinogenic potential. Many of these radiation-induced endpoints depend qualitatively and quantitatively on genetic background, dose and LET. Differences in the frequency and temporal expression of chromosomal instability depend on all three of the foregoing factors. On the other hand, many of these endpoints appear independent of dose and show bystander effects, implicating non-nuclear targets and epigenetic regulatory mechanisms. The present work will survey results concerning the LET dependence of genomic instability and the role of epigenetic mechanisms, with a particular emphasis on the endpoint of chromosomal in tability

  19. Scribable coating for plastic films

    NASA Technical Reports Server (NTRS)

    Clark, R. T.

    1967-01-01

    Scribable opaque coating for transparent plastic film tape is not affected by aging, vacuum, and moderate temperature extremes. It consists of titanium dioxide, a water-compatible acrylic polymer emulsion, and a detergent. The coating mixture is readily dispersed in water before it is dried.

  20. Chronic Ankle Instability

    MedlinePlus

    ... Risk for Newly Active Baby Boomers The American College of Foot and Ankle Surgeons has a valuable lesson for Baby Boomers now getting back into fitness and sports: Get your ankles checked for chronic instability caused ...

  1. Evaporatively driven morphological instability

    NASA Astrophysics Data System (ADS)

    Style, Robert W.; Wettlaufer, J. S.

    2007-07-01

    Simple observations of evaporating solutions reveal a complex hierarchy of spatiotemporal instabilities. We analyze one such instability suggested by the qualitative observations of Du and Stone and find that it is driven by a variant of the classical morphological instability in alloy solidification. In the latter case a moving solid-liquid interface is accompanied by a solutally enriched boundary layer that is thermodynamically metastable due to constitutional supercooling. Here, we consider the evaporation of an impure film adjacent to a solid composed of the nonvolatile species. In this case, constitutional supercooling within the film is created by evaporation at the solution-vapor interface and this drives the corrugation of the solid-solution interface across the thickness of the film. The principal points of this simple theoretical study are to suggest an instability mechanism that is likely operative across a broad range of technological and natural systems and to focus future quantitative experimental searches.

  2. Neuronal cytoskeleton in synaptic plasticity and regeneration.

    PubMed

    Gordon-Weeks, Phillip R; Fournier, Alyson E

    2014-04-01

    During development, dynamic changes in the axonal growth cone and dendrite are necessary for exploratory movements underlying initial axo-dendritic contact and ultimately the formation of a functional synapse. In the adult central nervous system, an impressive degree of plasticity is retained through morphological and molecular rearrangements in the pre- and post-synaptic compartments that underlie the strengthening or weakening of synaptic pathways. Plasticity is regulated by the interplay of permissive and inhibitory extracellular cues, which signal through receptors at the synapse to regulate the closure of critical periods of developmental plasticity as well as by acute changes in plasticity in response to experience and activity in the adult. The molecular underpinnings of synaptic plasticity are actively studied and it is clear that the cytoskeleton is a key substrate for many cues that affect plasticity. Many of the cues that restrict synaptic plasticity exhibit residual activity in the injured adult CNS and restrict regenerative growth by targeting the cytoskeleton. Here, we review some of the latest insights into how cytoskeletal remodeling affects neuronal plasticity and discuss how the cytoskeleton is being targeted in an effort to promote plasticity and repair following traumatic injury in the central nervous system. © 2013 International Society for Neurochemistry.

  3. Distal Radioulnar Joint Instability

    PubMed Central

    Mirghasemi, Ali R.; Lee, Daniel J.; Rahimi, Narges; Rashidinia, Shervin

    2015-01-01

    Distal radioulnar joint (DRUJ) instability is a common clinical condition but a frequently missed diagnosis. Both surgical and nonsurgical treatments are possible for chronic cases of DRUJ instability. Nonsurgical treatment can be considered as the primary therapy in less active patients, while surgery should be considered to recover bone and ligament injuries if nonsurgical treatment fails to restore forearm stability and function. The appropriate choice of treatment depends on the individual patient and specific derangement of the DRUJ PMID:26328241

  4. State Instability and Terrorism

    DTIC Science & Technology

    2010-01-01

    terrorism is a form ( Durkheim , 1930 [1951]; Useem, 1998). In addition, different types of instability ought to invite different levels of terrorism...society. The effects of the disruption in controls should be to increase levels of nonroutine collective action, of which terrorism is a form ( Durkheim ...instability at the country-level using a modified breakdown theoretical framework. This framework is based especially upon the work of Emile Durkheim

  5. Prediction of Algebraic Instabilities

    NASA Astrophysics Data System (ADS)

    Zaretzky, Paula; King, Kristina; Hill, Nicole; Keithley, Kimberlee; Barlow, Nathaniel; Weinstein, Steven; Cromer, Michael

    2016-11-01

    A widely unexplored type of hydrodynamic instability is examined - large-time algebraic growth. Such growth occurs on the threshold of (exponentially) neutral stability. A new methodology is provided for predicting the algebraic growth rate of an initial disturbance, when applied to the governing differential equation (or dispersion relation) describing wave propagation in dispersive media. Several types of algebraic instabilities are explored in the context of both linear and nonlinear waves.

  6. Evolution of environmental cues for phenotypic plasticity.

    PubMed

    Chevin, Luis-Miguel; Lande, Russell

    2015-10-01

    Phenotypically plastic characters may respond to multiple variables in their environment, but the evolutionary consequences of this phenomenon have rarely been addressed theoretically. We model the evolution of linear reaction norms in response to several correlated environmental variables, in a population undergoing stationary environmental fluctuations. At evolutionary equilibrium, the linear combination of environmental variables that acts as a developmental cue for the plastic trait is the multivariate best linear predictor of changes in the optimum. However, the reaction norm with respect to any single environmental variable may exhibit nonintuitive patterns. Apparently maladaptive, or hyperadaptive plasticity can evolve with respect to single environmental variables, and costs of plasticity may increase, rather than reduce, plasticity in response to some variables. We also find conditions for the evolution of an indirect environmental indicator that affects expression of a plastic phenotype, despite not influencing natural selection on it.

  7. Topographic-driven instabilities in terrestrial bodies

    NASA Astrophysics Data System (ADS)

    Vantieghem, S.; Cebron, D.; Herreman, W.; Lacaze, L.

    2013-12-01

    Models of internal planetary fluid layers (core flows, subsurface oceans) commonly assume that these fluid envelopes have a spherical shape. This approximation however entails a serious restriction from the fluid dynamics point of view. Indeed, in the presence of mechanical forcings (precession, libration, nutation or tides) due to gravitational interaction with orbiting partners, boundary topography (e.g. of the core-mantle boundary) may excite flow instabilities and space-filling turbulence. These phenomena may affect heat transport and dissipation at the main order. Here, we focus on instabilities driven by longitudinal libration. Using a suite of theoretical tools and numerical simulations, we are able to discern a parameter range for which instability may be excited. We thereby consider deformations of different azimuthal order. This study gives the first numerical evidence of the tripolar instability. Furthermore, we explore the non-linear regime and investigate the amplitude as well as the dissipation of the saturated instability. Indeed, these two quantities control the torques on the solid layers and the thermal transport. Furthermore, based on this results, we address the issue of magnetic field generation associated with these flows (by induction or by dynamo process). This instability mechanism applies to both synchronized as non-synchronized bodies. As such, our results show that a tripolar instability might be present in various terrestrial bodies (Early Moon, Gallilean moons, asteroids, etc.), where it could participate in dynamo action. Simulation of a libration-driven tripolar instability in a deformed spherical fluid layer: snapshot of the velocity magnitude, where a complex 3D flow pattern is established.

  8. Equilibrium Electroconvective Instability

    NASA Astrophysics Data System (ADS)

    Rubinstein, I.; Zaltzman, B.

    2015-03-01

    Since its prediction 15 years ago, hydrodynamic instability in concentration polarization at a charge-selective interface has been attributed to nonequilibrium electro-osmosis related to the extended space charge which develops at the limiting current. This attribution had a double basis. On the one hand, it has been recognized that neither equilibrium electro-osmosis nor bulk electroconvection can yield instability for a perfectly charge-selective solid. On the other hand, it has been shown that nonequilibrium electro-osmosis can. The first theoretical studies in which electro-osmotic instability was predicted and analyzed employed the assumption of perfect charge selectivity for the sake of simplicity and so did the subsequent studies of various time-dependent and nonlinear features of electro-osmotic instability. In this Letter, we show that relaxing the assumption of perfect charge selectivity (tantamount to fixing the electrochemical potential of counterions in the solid) allows for the equilibrium electroconvective instability. In addition, we suggest a simple experimental test for determining the true, either equilibrium or nonequilibrium, origin of instability in concentration polarization.

  9. The single-mode CSR instability for a bunched beam

    SciTech Connect

    Heifets, Samuel A

    2003-03-19

    The coherent synchrotron radiation (CSR) instability at the shielding threshold may be driven by a single synchronous mode excited by the beam in the beam pipe. The instability in this case has been analyzed [1] in the coasting beam approximation neglecting synchrotron motion. The later becomes important at large time intervals in storage rings where it substantially affects the beam dynamics. The single-mode CSR instability of a bunched beam with the synchrotron motion taken into account is described in this paper both in linear and nonlinear regimes. Analysis is relevant to other instabilities where the interaction is dominated by a single mode.

  10. On The Prediction Of Plastic Instability In Metal Sheets

    SciTech Connect

    Mattiasson, Kjell; Sigvant, Mats; Larsson, Mats

    2007-05-17

    The current report presents some results from a study on the prediction of necking failure in ductile metal sheets. In particular methods for creating Forming Limit Curves (FLCs) are discussed in the present report. Three groups of methods are treated: Experimental methods, Theoretical/analytical methods, and the Finite Element Method (FEM). The various methods are applied to two different materials: An aluminum alloy and a high strength steel. These materials do both exhibit a distinct necking behavior before fracture, and they do both exhibit only a small strain rate dependence. As can be expected, the resulting FLCs from the various experimental, theoretical, and numerical methods show a substantial scatter. The reasons for these deviating results are analyzed, and some conclusions are drawn regarding the applicability of the different methods.

  11. Providing plastic zone extrusion

    DOEpatents

    Manchiraju, Venkata Kiran; Feng, Zhili; David, Stan A.; Yu, Zhenzhen

    2017-04-11

    Plastic zone extrusion may be provided. First, a compressor may generate frictional heat in stock to place the stock in a plastic zone of the stock. Then, a conveyer may receive the stock in its plastic zone from the compressor and transport the stock in its plastic zone from the compressor. Next, a die may receive the stock in its plastic zone from the conveyer and extrude the stock to form a wire.

  12. Polychlorinated biphenyls and organochlorine pesticides in plastics ingested by seabirds.

    PubMed

    Colabuono, Fernanda Imperatrice; Taniguchi, Satie; Montone, Rosalinda Carmela

    2010-04-01

    The occurrence of plastic objects in the digestive tract was assessed in eight species of Procellariiformes collected in southern Brazil and the occurrence of polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs) in the ingested plastics pellets and plastic fragments was evaluated. PCBs were detected in plastic pellets (491 ng g(-1)) and plastic fragments (243-418 ng g(-1)). Among the OCPs, p,p'-DDE had the highest concentrations, ranging from 68.0 to 99.0 ng g(-1). The occurrence of organic pollutants in post-consumer plastics supports the fact that plastics are an important source carrying persistent organic pollutants in the marine environment. Although transfer through the food chain may be the main source of exposure to POPs to seabirds, plastics could be an additional source for the organisms which ingest them, like Procellariiformes which are the seabirds most affected by plastic pollution. (c) 2010 Elsevier Ltd. All rights reserved.

  13. Genomic Instability in Cancer

    PubMed Central

    Abbas, Tarek; Keaton, Mignon A.; Dutta, Anindya

    2013-01-01

    One of the fundamental challenges facing the cell is to accurately copy its genetic material to daughter cells. When this process goes awry, genomic instability ensues in which genetic alterations ranging from nucleotide changes to chromosomal translocations and aneuploidy occur. Organisms have developed multiple mechanisms that can be classified into two major classes to ensure the fidelity of DNA replication. The first class includes mechanisms that prevent premature initiation of DNA replication and ensure that the genome is fully replicated once and only once during each division cycle. These include cyclin-dependent kinase (CDK)-dependent mechanisms and CDK-independent mechanisms. Although CDK-dependent mechanisms are largely conserved in eukaryotes, higher eukaryotes have evolved additional mechanisms that seem to play a larger role in preventing aberrant DNA replication and genome instability. The second class ensures that cells are able to respond to various cues that continuously threaten the integrity of the genome by initiating DNA-damage-dependent “checkpoints” and coordinating DNA damage repair mechanisms. Defects in the ability to safeguard against aberrant DNA replication and to respond to DNA damage contribute to genomic instability and the development of human malignancy. In this article, we summarize our current knowledge of how genomic instability arises, with a particular emphasis on how the DNA replication process can give rise to such instability. PMID:23335075

  14. Low energy ghosts and the Jeans' instability

    NASA Astrophysics Data System (ADS)

    Gümrükçüoǧlu, A. Emir; Mukohyama, Shinji; Sotiriou, Thomas P.

    2016-09-01

    We show that a massless canonical scalar field minimally coupled to general relativity can become a tachyonic ghost at low energies around a background in which the scalar's gradient is spacelike. By performing a canonical transformation we demonstrate that this low energy ghost can be recast, at the level of the action, in a form of a fluid that undergoes a Jeans-like instability affecting only modes with large wavelength. This illustrates that low energy tachyonic ghosts do not lead to a catastrophic quantum vacuum instability, unlike the usual high-energy ghost degrees of freedom.

  15. Magneto-Rayleigh-Taylor instability in solid media

    SciTech Connect

    Sun, Y. B.; Piriz, A. R.

    2014-07-15

    A linear analysis of the magneto-Rayleigh-Taylor instability at the interface between a Newtonian fluid and an elastic-plastic solid is performed by considering a uniform magnetic B{sup →}, parallel to the interface, which has diffused into the fluid but not into the solid. It is found that the magnetic field attributes elastic properties to the viscous fluid which enhance the stability region by stabilizing all the perturbation wavelengths shorter than λ{sub 0}∝B{sup 2} for any initial perturbation amplitude. Longer wavelengths are stabilized by the mechanical properties of the solid provided that the initial perturbation wavelength is smaller than a threshold value determined by the yield strength and the shear modulus of the solid. Beyond this threshold, the amplitude grows initially with a growth rate reduced by the solid strength properties. However, such properties do not affect the asymptotic growth rate which is only determined by the magnetic field and the fluid viscosity. The described physical situation intends to resemble some of the features present in recent experiments involving the magnetic shockless acceleration of flyers plates.

  16. Pathways towards instability in financial networks

    NASA Astrophysics Data System (ADS)

    Bardoscia, Marco; Battiston, Stefano; Caccioli, Fabio; Caldarelli, Guido

    2017-02-01

    Following the financial crisis of 2007-2008, a deep analogy between the origins of instability in financial systems and complex ecosystems has been pointed out: in both cases, topological features of network structures influence how easily distress can spread within the system. However, in financial network models, the details of how financial institutions interact typically play a decisive role, and a general understanding of precisely how network topology creates instability remains lacking. Here we show how processes that are widely believed to stabilize the financial system, that is, market integration and diversification, can actually drive it towards instability, as they contribute to create cyclical structures which tend to amplify financial distress, thereby undermining systemic stability and making large crises more likely. This result holds irrespective of the details of how institutions interact, showing that policy-relevant analysis of the factors affecting financial stability can be carried out while abstracting away from such details.

  17. Pathways towards instability in financial networks

    PubMed Central

    Bardoscia, Marco; Battiston, Stefano; Caccioli, Fabio; Caldarelli, Guido

    2017-01-01

    Following the financial crisis of 2007–2008, a deep analogy between the origins of instability in financial systems and complex ecosystems has been pointed out: in both cases, topological features of network structures influence how easily distress can spread within the system. However, in financial network models, the details of how financial institutions interact typically play a decisive role, and a general understanding of precisely how network topology creates instability remains lacking. Here we show how processes that are widely believed to stabilize the financial system, that is, market integration and diversification, can actually drive it towards instability, as they contribute to create cyclical structures which tend to amplify financial distress, thereby undermining systemic stability and making large crises more likely. This result holds irrespective of the details of how institutions interact, showing that policy-relevant analysis of the factors affecting financial stability can be carried out while abstracting away from such details. PMID:28221338

  18. Pathways towards instability in financial networks.

    PubMed

    Bardoscia, Marco; Battiston, Stefano; Caccioli, Fabio; Caldarelli, Guido

    2017-02-21

    Following the financial crisis of 2007-2008, a deep analogy between the origins of instability in financial systems and complex ecosystems has been pointed out: in both cases, topological features of network structures influence how easily distress can spread within the system. However, in financial network models, the details of how financial institutions interact typically play a decisive role, and a general understanding of precisely how network topology creates instability remains lacking. Here we show how processes that are widely believed to stabilize the financial system, that is, market integration and diversification, can actually drive it towards instability, as they contribute to create cyclical structures which tend to amplify financial distress, thereby undermining systemic stability and making large crises more likely. This result holds irrespective of the details of how institutions interact, showing that policy-relevant analysis of the factors affecting financial stability can be carried out while abstracting away from such details.

  19. Instabilities in a Layer-Multiplying Device

    NASA Astrophysics Data System (ADS)

    Sollogoub, Cyrille; Grandmontagne, Anne; Guinault, Alain

    2011-01-01

    The application of a layer-multiplying device to coextrusion has resulted in a process, called microlayer coextrusion, producing films with ten to thousands of layers of two different polymers. It was shown that this device is quite versatile and can be used to produce new layered systems with improved mechanical, optical, electrical and barrier properties. However, instabilities may occur in the feedblock and/or the layer multiplying unit, affecting the uniformity and the continuity of the created layers. Those instabilities have been widely studied for classical systems with three to five layer structures, while very few studies deal with microlayer coextrusion process. The aim of this paper is to study the flow instabilities in multilayered films. In particular, the role of polymer properties and the effect of some parameters, such as the viscosity ratio, will be investigated.

  20. Entanglement production at Instabilities

    NASA Astrophysics Data System (ADS)

    Hackl, Lucas; Bianchi, Eugenio; Yokomizo, Nelson

    2016-03-01

    Instabilities play a major role in various areas of physics. In this talk, I will present some new results on how instabilities produce entanglement between subsystems. We study the asymptotic behavior of the entanglement entropy when we evolve a squeezed vacuum with an unstable quadratic Hamiltonian. We show that in this setting the entanglement entropy always grows linearly with a slope determined by the classical Lyapunov exponents of the system, resembling the classical Kolmogorov-Sinai entropy rate. Our theorem applies to all bosonic quantum field theories with quadratic coupling, including the scalar Schwinger effect, the inverted mass scalar field and various complex field theory models.

  1. Dislocation motion and instability

    NASA Astrophysics Data System (ADS)

    Zhu, Yichao; Chapman, Stephen Jonathan; Acharya, Amit

    2013-08-01

    The Peach-Koehler expression for the stress generated by a single (non-planar) curvilinear dislocation is evaluated to calculate the dislocation self stress. This is combined with a law of motion to give the self-induced motion of a general dislocation curve. A stability analysis of a rectilinear, uniformly translating dislocation is then performed. The dislocation is found to be susceptible to a helical instability, with the maximum growth rate occurring when the dislocation is almost, but not exactly, pure screw. The non-linear evolution of the instability is determined numerically, and implications for slip band formation and non-Schmid behavior in yielding are discussed.

  2. Circuit reactivation dynamically regulates synaptic plasticity in neocortex

    NASA Astrophysics Data System (ADS)

    Kruskal, Peter B.; Li, Lucy; Maclean, Jason N.

    2013-10-01

    Circuit reactivations involve a stereotyped sequence of neuronal firing and have been behaviourally linked to memory consolidation. Here we use multiphoton imaging and patch-clamp recording, and observe sparse and stereotyped circuit reactivations that correspond to UP states within active neurons. To evaluate the effect of the circuit on synaptic plasticity, we trigger a single spike-timing-dependent plasticity (STDP) pairing once per circuit reactivation. The pairings reliably fall within a particular epoch of the circuit sequence and result in long-term potentiation. During reactivation, the amplitude of plasticity significantly correlates with the preceding 20-25 ms of membrane depolarization rather than the depolarization at the time of pairing. This circuit-dependent plasticity provides a natural constraint on synaptic potentiation, regulating the inherent instability of STDP in an assembly phase-sequence model. Subthreshold voltage during endogenous circuit reactivations provides a critical informative context for plasticity and facilitates the stable consolidation of a spatiotemporal sequence.

  3. Plastic casting resin poisoning

    MedlinePlus

    Epoxy poisoning; Resin poisoning ... Epoxy and resin can be poisonous if they are swallowed or their fumes are breathed in. ... Plastic casting resins are found in various plastic casting resin products.

  4. Plastic encapsulated parts

    SciTech Connect

    Castillo, T.

    1994-10-01

    Plastic semiconductor packages were characterized as possible alternatives for canned devices, which are susceptible to internal shorts caused by conductive particles. Highly accelerated stress testing (HAST) as well as electrical and mechanical testing were conducted on plastic technology devices.

  5. Ear Plastic Surgery

    MedlinePlus

    ... ENTCareers Marketplace Find an ENT Doctor Near You Ear Plastic Surgery Ear Plastic Surgery Patient Health Information ... they may improve appearance and self-confidence. Can Ear Deformities Be Corrected? Formation of the ear during ...

  6. Electric Field Induced Interfacial Instabilities

    NASA Technical Reports Server (NTRS)

    Kusner, Robert E.; Min, Kyung Yang; Wu, Xiao-Lun; Onuki, Akira

    1996-01-01

    The study of the interface in a charge-free, nonpolar, critical and near-critical binary fluid in the presence of an externally applied electric field is presented. At sufficiently large fields, the interface between the two phases of the binary fluid should become unstable and exhibit an undulation with a predefined wavelength on the order of the capillary length. As the critical point is approached, this wavelength is reduced, potentially approaching length-scales such as the correlation length or critical nucleation radius. At this point the critical properties of the system may be affected. In zero gravity, the interface is unstable at all long wavelengths in the presence of a field applied across it. It is conjectured that this will cause the binary fluid to break up into domains small enough to be outside the instability condition. The resulting pattern formation, and the effects on the critical properties as the domains approach the correlation length are of acute interest. With direct observation, laser light scattering, and interferometry, the phenomena can be probed to gain further understanding of interfacial instabilities and the pattern formation which results, and dimensional crossover in critical systems as the critical fluctuations in a particular direction are suppressed by external forces.

  7. Genome instability, cancer and aging

    PubMed Central

    Maslov, Alexander Y.; Vijg, Jan

    2015-01-01

    DNA damage-driven genome instability underlies the diversity of life forms generated by the evolutionary process but is detrimental to the somatic cells of individual organisms. The cellular response to DNA damage can be roughly divided in two parts. First, when damage is severe, programmed cell death may occur or, alternatively, temporary or permanent cell cycle arrest. This protects against cancer but can have negative effects on the long term, e.g., by depleting stem cell reservoirs. Second, damage can be repaired through one or more of the many sophisticated genome maintenance pathways. However, erroneous DNA repair and incomplete restoration of chromatin after damage is resolved, produce mutations and epimutations, respectively, both of which have been shown to accumulate with age. An increased burden of mutations and/or epimutations in aged tissues increases cancer risk and adversely affects gene transcriptional regulation, leading to progressive decline in organ function. Cellular degeneration and uncontrolled cell proliferation are both major hallmarks of aging. Despite the fact that one seems to exclude the other, they both may be driven by a common mechanism. Here, we review age related changes in the mammalian genome and their possible functional consequences, with special emphasis on genome instability in stem/progenitor cells. PMID:19344750

  8. [Psychodynamics of childhood instability].

    PubMed

    Flavigny, C

    1988-01-01

    This work focuses on the Anglo-Saxon idea concerning "hyperactivity" and "hyperkinesis" and the French-language idea of "child psycho-motor instability". The author's own personal study (having two separate parts, on the one hand studying the psychic functioning of parent and their interaction with their child, and on the other, studying material gathered on the individual psychotherapy of unstable children), goes along with the French school of thought, highlighting the extent of incestuous sexual advances toward children (especially boys) in the family unit and the sexual nature (in the sense of child sexuality) of this excitement as the source of their instability, justifying a comparison between the unstable child and a Don Juan-type of instability. What comes out is epistemological thinking on Anglo-Saxon and French-language ideas, in particular criticism of the pre-suppositions in the Anglo-Saxon way of seeing things, which seems only to envisage the characterization of a syndromic range, rather than an organic etiology, this being more often implicit; distanced by the idea of psychodynamics, which predominate in the French-language studies, integrating the symptom of "psycho-motor instability" in the general "wholeness" of the child and evaluating ways of parent-child interaction.

  9. Partial Torus Instability

    NASA Astrophysics Data System (ADS)

    Olmedo, Oscar; Zhang, J.

    2010-05-01

    Flux ropes are now generally accepted to be the magnetic configuration of Coronal Mass Ejections (CMEs), which may be formed prior or during solar eruptions. In this study, we model the flux rope as a current-carrying partial torus loop with its two footpoints anchored in the photosphere, and investigate its instability in the context of the torus instability (TI). Previous studies on TI have focused on the configuration of a circular torus and revealed the existence of a critical decay index. Our study reveals that the critical index is a function of the fractional number of the partial torus, defined by the ratio between the arc length of the partial torus above the photosphere and the circumference of a circular torus of equal radius. We refer to this finding the partial torus instability (PTI). It is found that a partial torus with a smaller fractional number has a smaller critical index, thus requiring a more gradually decreasing magnetic field to stabilize the flux rope. On the other hand, the partial torus with a larger fractional number has a larger critical index. In the limit of a circular torus when the fractional number approaches one, the critical index goes to a maximum value that depends on the distribution of the external magnetic field. We demonstrate that the partial torus instability helps us to understand the confinement, growth, and eventual eruption of a flux rope CME.

  10. Electromagnetic ion beam instabilities

    NASA Technical Reports Server (NTRS)

    Gary, S. P.; Foosland, D. W.; Smith, C. W.; Lee, M. A.; Goldstein, M. L.

    1984-01-01

    The linear theory of electromagnetic instabilities driven by an energetic ion beam streaming parallel to a magnetic field in a homogeneous Vlasov plasma is considered. Numerical solutions of the full dispersion equation are presented. At propagation parallel to the magnetic field, there are four distinct instabilities. A sufficiently energetic beam gives rise to two unstable modes with right-hand polarization, one resonant with the beam, the other nonresonant. A beam with sufficiently large T (perpendicular to B)/T (parallel to B) gives rise to the left-hand ion cyclotron anisotropy instability at relatively small beam velocities, and a sufficiently hot beam drives unstable a left-hand beam resonant mode. The parametric dependences of the growth rates for the three high beam velocity instabilities are presented here. In addition, some properties at oblique propagation are examined. It is demonstrated that, as the beam drift velocity is increased, relative maxima in growth rates can arise at harmonics of the ion cyclotron resonance for both right and left elliptically polarized modes.

  11. Multidirectional Shoulder Instability: Treatment

    PubMed Central

    Ruiz Ibán, Miguel Angel; Díaz Heredia, Jorge; García Navlet, Miguel; Serrano, Francisco; Santos Oliete, María

    2017-01-01

    Background: The treatment of multidirectional instability of the shoulder is complex. The surgeon should have a clear understanding of the role of hiperlaxity, anatomical variations, muscle misbalance and possible traumatic incidents in each patient. Methods: A review of the relevant literature was performed including indexed journals in English and Spanish. The review was focused in both surgical and conservative management of multidirectional shoulder instability. Results: Most patients with multidirectional instability will be best served with a period of conservative management with physical therapy; this should focus in restoring strength and balance of the dynamic stabilizers of the shoulder. The presence of a significant traumatic incident, anatomic alterations and psychological problems are widely considered to be poor prognostic factors for conservative treatment. Patients who do not show a favorable response after 3 months of conservative treatment seem to get no benefit from further physical therapy. When conservative treatment fails, a surgical intervention is warranted. Both open capsular shift and arthroscopic capsular plication are considered to be the treatment of choice in these patients and have similar outcomes. Thermal or laser capsuloraphy is no longer recommended. Conclusion: Multidirectional instability is a complex problem. Conservative management with focus on strengthening and balancing of the dynamic shoulder stabilizers is the first alternative. Some patients will fare poorly and require either open or arthroscopic capsular plication.

  12. #PlasticSurgery.

    PubMed

    Branford, Olivier A; Kamali, Parisa; Rohrich, Rod J; Song, David H; Mallucci, Patrick; Liu, Daniel Z; Lang, Dustin; Sun, Kristi; Stubican, Miran; Lin, Samuel J

    2016-12-01

    Social media use is growing inexorably, and there is public appetite for evidence-based information. Little is known about engagement by plastic surgeons with social media. The aim of this study was to examine posting about plastic surgery on Twitter, to best inform how board-certified plastic surgeons could use the hashtag #PlasticSurgery as a tool to educate patients and the public. A prospective analysis of 2880 "tweets" containing the words "plastic surgery" was performed. The following were assessed: identity of author, use of the hashtag #PlasticSurgery, subject matter, whether link to study was provided, and whether posts by surgeons were self-promotional or educational. Social media posting about plastic surgery is dominated by the public, accounting for 70.6 percent of posts versus only 6.0 percent by plastic surgeons. Only 5.4 percent of all tweets contained the hashtag #PlasticSurgery, although almost half of those that did were by plastic surgeons. Of these, 61.3 percent of posts by plastic surgeons were about aesthetic surgery; additional posts were about basic science, patient safety, and reconstruction (13.9, 4.0, and 2.3 percent, respectively). Eighteen scientific articles were referenced, with a link to the Journal site posted in two tweets. Of posts by plastic surgeons, 37.0 percent were self-promotional. The American Society of Plastic Surgeons and its Journal have recognized that social media may be used to educate and engage. Board-certified plastic surgeons have a great opportunity to promote evidence-based plastic practice by means of #PlasticSurgery in the interests of supporting patients and the profession.

  13. Tomorrow's Plastic World

    ERIC Educational Resources Information Center

    Macdonald, Averil

    2005-01-01

    Far from being just cheap packaging materials, plastics may be the materials of tomorrow. Plastic can conduct electricity, and this opens up a host of high-tech possibilities in the home and in energy generation. These possibilities are discussed here along with how plastic can be recycled and perhaps even grown.

  14. Plastics in Building.

    ERIC Educational Resources Information Center

    Skeist, Irving, Ed.

    The evaluation and use of plastics in the construction industry are explained. The contributors offer extensive, timely, and thoroughly researched data on the chemistry, properties, functions, engineering behavior, and specific applications of plastics to building requirements. The major subjects discussed in depth are--(1) the role of plastics in…

  15. Processing of plastics

    PubMed Central

    Spaak, Albert

    1975-01-01

    An overview is given of the processing of plastic materials from the handling of polymers in the pellet and powder form to manufacturing of a plastic fabricated product. Various types of equipment used and melt processing ranges of various polymer formulations to make the myriad of plastic products that are commercially available are discussed. PMID:1175556

  16. Tomorrow's Plastic World

    ERIC Educational Resources Information Center

    Macdonald, Averil

    2005-01-01

    Far from being just cheap packaging materials, plastics may be the materials of tomorrow. Plastic can conduct electricity, and this opens up a host of high-tech possibilities in the home and in energy generation. These possibilities are discussed here along with how plastic can be recycled and perhaps even grown.

  17. Plastics in Building.

    ERIC Educational Resources Information Center

    Skeist, Irving, Ed.

    The evaluation and use of plastics in the construction industry are explained. The contributors offer extensive, timely, and thoroughly researched data on the chemistry, properties, functions, engineering behavior, and specific applications of plastics to building requirements. The major subjects discussed in depth are--(1) the role of plastics in…

  18. Plastic Accumulation in the Mediterranean Sea

    PubMed Central

    Cózar, Andrés; Sanz-Martín, Marina; Martí, Elisa; González-Gordillo, J. Ignacio; Ubeda, Bárbara; Gálvez, José Á.; Irigoien, Xabier; Duarte, Carlos M.

    2015-01-01

    Concentrations of floating plastic were measured throughout the Mediterranean Sea to assess whether this basin can be regarded as a great accumulation region of plastic debris. We found that the average density of plastic (1 item per 4 m2), as well as its frequency of occurrence (100% of the sites sampled), are comparable to the accumulation zones described for the five subtropical ocean gyres. Plastic debris in the Mediterranean surface waters was dominated by millimeter-sized fragments, but showed a higher proportion of large plastic objects than that present in oceanic gyres, reflecting the closer connection with pollution sources. The accumulation of floating plastic in the Mediterranean Sea (between 1,000 and 3,000 tons) is likely related to the high human pressure together with the hydrodynamics of this semi-enclosed basin, with outflow mainly occurring through a deep water layer. Given the biological richness and concentration of economic activities in the Mediterranean Sea, the affects of plastic pollution on marine and human life are expected to be particularly frequent in this plastic accumulation region. PMID:25831129

  19. Plastic accumulation in the Mediterranean sea.

    PubMed

    Cózar, Andrés; Sanz-Martín, Marina; Martí, Elisa; González-Gordillo, J Ignacio; Ubeda, Bárbara; Gálvez, José Á; Irigoien, Xabier; Duarte, Carlos M

    2015-01-01

    Concentrations of floating plastic were measured throughout the Mediterranean Sea to assess whether this basin can be regarded as a great accumulation region of plastic debris. We found that the average density of plastic (1 item per 4 m2), as well as its frequency of occurrence (100% of the sites sampled), are comparable to the accumulation zones described for the five subtropical ocean gyres. Plastic debris in the Mediterranean surface waters was dominated by millimeter-sized fragments, but showed a higher proportion of large plastic objects than that present in oceanic gyres, reflecting the closer connection with pollution sources. The accumulation of floating plastic in the Mediterranean Sea (between 1,000 and 3,000 tons) is likely related to the high human pressure together with the hydrodynamics of this semi-enclosed basin, with outflow mainly occurring through a deep water layer. Given the biological richness and concentration of economic activities in the Mediterranean Sea, the affects of plastic pollution on marine and human life are expected to be particularly frequent in this plastic accumulation region.

  20. Plasticity of Nonneuronal Brain Tissue: Roles in Developmental Disorders

    ERIC Educational Resources Information Center

    Dong, Willie K.; Greenough, William T.

    2004-01-01

    Neuronal and nonneuronal plasticity are both affected by environmental and experiential factors. Remodeling of existing neurons induced by such factors has been observed throughout the brain, and includes alterations in dendritic field dimensions, synaptogenesis, and synaptic morphology. The brain loci affected by these plastic neuronal changes…

  1. Plasticity of Nonneuronal Brain Tissue: Roles in Developmental Disorders

    ERIC Educational Resources Information Center

    Dong, Willie K.; Greenough, William T.

    2004-01-01

    Neuronal and nonneuronal plasticity are both affected by environmental and experiential factors. Remodeling of existing neurons induced by such factors has been observed throughout the brain, and includes alterations in dendritic field dimensions, synaptogenesis, and synaptic morphology. The brain loci affected by these plastic neuronal changes…

  2. Instability improvement of the subgrade soils by lime addition at Borg El-Arab, Alexandria, Egypt

    NASA Astrophysics Data System (ADS)

    El Shinawi, A.

    2017-06-01

    Subgrade soils can affect the stability of any construction elsewhere, instability problems were found at Borg El-Arab, Alexandria, Egypt. This paper investigates geoengineering properties of lime treated subgrade soils at Borg El-Arab. Basic laboratory tests, such as water content, wet and dry density, grain size, specific gravity and Atterberg limits, were performed for twenty-five samples. Moisture-density (compaction); California Bearing Ratio (CBR) and Unconfined Compression Strength (UCS) were conducted on treated and natural soils. The measured geotechnical parameters of the treated soil shows that 6% lime is good enough to stabilize the subgrade soils. It was found that by adding lime, samples shifted to coarser side, Atterberg limits values of the treated soil samples decreased and this will improve the soil to be more stable. On the other hand, Subgrade soils improved as a result of the bonding fine particles, cemented together to form larger size and reduce the plastiCity index which increase soils strength. The environmental scanning electron microscope (ESEM) is point to the presence of innovative aggregated cement materials which reduce the porosity and increase the strength as a long-term curing. Consequently, the mixture of soil with the lime has acceptable mechanical characteristics where, it composed of a high strength base or sub-base materials and this mixture considered as subgrade soil for stabilizations and mitigation the instability problems that found at Borg Al-Arab, Egypt.

  3. Genomic instability, driver genes and cell selection: Projections from cancer to stem cells.

    PubMed

    Ben-David, Uri

    2015-04-01

    Cancer cells and stem cells share many traits, including a tendency towards genomic instability. Human cancers exhibit tumor-specific genomic aberrations, which often affect their malignancy and drug response. During their culture propagation, human pluripotent stem cells (hPSCs) also acquire characteristic genomic aberrations, which may have significant impact on their molecular and cellular phenotypes. These aberrations vary in size from single nucleotide alterations to copy number alterations to whole chromosome gains. A prominent challenge in both cancer and stem cell research is to identify "driver aberrations" that confer a selection advantage, and "driver genes" that underlie the recurrence of these aberrations. Following principles that are already well-established in cancer research, candidate driver genes have also been suggested in hPSCs. Experimental validation of the functional role of such candidates can uncover whether these are bona fide driver genes. The identification of driver genes may bring us closer to a mechanistic understanding of the genomic instability of stem cells. Guided by terminologies and methodologies commonly applied in cancer research, such understanding may have important ramifications for both stem cell and cancer biology. This article is part of a Special Issue entitled: Stress as a fundamental theme in cell plasticity.

  4. Suppression of the Rayleigh-Taylor instability due to self-radiation in a multiablation target.

    PubMed

    Fujioka, Shinsuke; Sunahara, Atsushi; Nishihara, Katsunobu; Ohnishi, Naofumi; Johzaki, Tomoyuki; Shiraga, Hiroyuki; Shigemori, Keisuke; Nakai, Mitsuo; Ikegawa, Tadashi; Murakami, Masakatsu; Nagai, Keiji; Norimatsu, Takayoshi; Azechi, Hiroshi; Yamanaka, Tatsuhiko

    2004-05-14

    A scheme to suppress the Rayleigh-Taylor instability has been investigated for a direct-drive inertial fusion target. In a high-Z doped-plastic target, two ablation surfaces are formed separately-one driven by thermal radiation and the other driven by electron conduction. The growth of the Rayleigh-Taylor instability is significantly suppressed on the radiation-driven ablation surface inside the target due to the large ablation velocity and long density scale length. A significant reduction of the growth rate was observed in simulations and experiments using a brominated plastic target. A new direct-drive pellet was designed using this scheme.

  5. Test Methods: Cast Plastic Tooling Materials.

    DTIC Science & Technology

    1957-04-01

    The physical and working properties of room temperature curing tooling resin systems are affected by the factors listed below: (a) Temperature of...Hardeners stored exposed to moisture. (h) Presence of moisture in plasters against which the tool surfaces will be made. (i) Types of fillers used in...developed for the plastics industry and its suppliers to facilitate the exchange of test data and to promote the development of materials and techniques which will advance the use of plastics in tooling applications.

  6. Instability in poroelastic media

    NASA Astrophysics Data System (ADS)

    Pramanik, Satyajit; Wettlaufer, John

    2016-11-01

    Fluid flow in deformable porous materials, which play significant role in different biological and geological systems of wide range of scales, is a highly nonlinear problem. Feedback from the elastic deformation of the solid skeleton on the fluid flow and vice-versa gives rise to pattern formation in the porosity structure of the skeleton. We view some of these patterns as instabilities of the coupled fluid-solid system. Due to highly nonlinear nature of the problem, very little has been understood about this instability. Here, we use a minimal poroelastic theory to understand the pattern formation in a fluid-saturated poroelastic material and discuss the similarities/differences with viscous fingering in non-deformable porous media.

  7. Open field lines instabilities

    SciTech Connect

    Pozzoli, R. |

    1995-09-01

    The results of some recent theoretical papers dealing with flute-like instabilities in the scrape-off layer of a tokamak with limiter configuration, where the magnetic field intersects conducting walls, are briefly recalled. Attention is then paid to the instability driven by the electron temperature gradient across the field in conjunction with the formation of the Debye sheath at the boundary, and to the effects due to the inclination of the end walls with respect to the magnetic field. When a divertor configuration is considered, important modifications are found owing to the strong deformations of the flux tubes passing near the {ital x}-point, which contrast the onset of flute-like perturbations, and to the stochasticity of field lines that can be excited by magnetic field perturbations. {copyright} {ital 1995 American Institute of Physics.}

  8. Modulation instability: The beginning

    NASA Astrophysics Data System (ADS)

    Noskov, Roman; Belov, Pavel; Kivshar, Yuri

    2012-11-01

    The study of metal nanoparticles plays a central role in the emerging novel technologies employing optics beyond the diffraction limit. Combining strong surface plasmon resonances, high intrinsic nonlinearities and deeply subwavelength scales, arrays of metal nanoparticles offer a unique playground to develop novel concepts for light manipulation at the nanoscale. Here we suggest a novel principle to control localized optical energy in chains of nonlinear subwavelength metal nanoparticles based on the fundamental nonlinear phenomenon of modulation instability. In particular, we demonstrate that modulation instability can lead to the formation of long-lived standing and moving nonlinear localized modes of several distinct types such as bright and dark solitons, oscillons, and domain walls. We analyze the properties of these nonlinear localized modes and reveal different scenarios of their dynamics including transformation of one type of mode to another. We believe this work paves a way towards the development of nonlinear nanophotonics circuitry.

  9. Instabilities in sensory processes

    NASA Astrophysics Data System (ADS)

    Balakrishnan, J.

    2014-07-01

    In any organism there are different kinds of sensory receptors for detecting the various, distinct stimuli through which its external environment may impinge upon it. These receptors convey these stimuli in different ways to an organism's information processing region enabling it to distinctly perceive the varied sensations and to respond to them. The behavior of cells and their response to stimuli may be captured through simple mathematical models employing regulatory feedback mechanisms. We argue that the sensory processes such as olfaction function optimally by operating in the close proximity of dynamical instabilities. In the case of coupled neurons, we point out that random disturbances and fluctuations can move their operating point close to certain dynamical instabilities triggering synchronous activity.

  10. Wrist Instability After Injury

    PubMed Central

    Muminagic, Sahib; Kapidzic, Tarik

    2012-01-01

    Fractures of the bones that make the wrist joint together with injury to the ligaments and joint capsules are frequent traumas. It can cause besides limited movement also the pathological mobility. These mild injuries often do not provide the degree of recognizable symptoms and signs. They are diagnosed by X-ray imaging, stress images. Before arthrography was an important method, but nowadays arthroscopy has the advantage. Fresh bone and ligament injuries can be and should be repaired in the early posttraumatic period. Unrecognized and undiagnosed injuries are leading to instability of the wrist, to motion abnormalities or impingement overload syndrome. In the treatment of instability important place have reconstruction of the ligaments and arthrodesis of the wrist. PMID:23678318

  11. [Orthostatic tremor inducing instability].

    PubMed

    Manrique-Huarte, Raquel; Arcocha, Juan; Pérez-Fernández, Nicolás

    2012-01-01

    Orthostatic tremor (OT) is a neurological disease of unknown aetiology. It is defined by the presence of a 10-20 Hz tremor in the legs while standing still. Symptoms described are dizziness and instability that diminish if the patient sits down or leans on something; drinking small amounts of alcohol significantly reduces OT. Due to the dizziness and/or unsteadiness, these patients are usually referred to the neuro-otology department. We report 4 cases diagnosed with OT. The diagnosis of OT should be considered for patients with instability. The clinical history is a key factor to suspect this entity, and the diagnosis is given by the register of 10-20 Hz contractions on limb electromyography. Treatment for this disease consists of medical treatment; the first option is clonazepam.

  12. Modulation instability: The beginning

    NASA Astrophysics Data System (ADS)

    Zakharov, V. E.; Ostrovsky, L. A.

    2009-03-01

    We discuss the early history of an important field of “sturm and drang” in modern theory of nonlinear waves. It is demonstrated how scientific demand resulted in independent and almost simultaneous publications by many different authors on modulation instability, a phenomenon resulting in a variety of nonlinear processes such as envelope solitons, envelope shocks, freak waves, etc. Examples from water wave hydrodynamics, electrodynamics, nonlinear optics, and convection theory are given.

  13. The signaling mechanisms of hippocampal endoplasmic reticulum stress affecting neuronal plasticity-related protein levels in high fat diet-induced obese rats and the regulation of aerobic exercise.

    PubMed

    Cai, Ming; Wang, Hong; Li, Jing-Jing; Zhang, Yun-Li; Xin, Lei; Li, Feng; Lou, Shu-Jie

    2016-10-01

    High fat diet (HFD)-induced obesity has been shown to reduce the levels of neuronal plasticity-related proteins, specifically brain-derived neurotrophic factor (BDNF) and synaptophysin (SYN), in the hippocampus. However, the underlying mechanisms are not fully clear. Endoplasmic reticulum stress (ERS) has been reported to play a key role in regulating gene expression and protein production by affecting stress signaling pathways and ER functions of protein folding and post-translational modification in peripheral tissues of obese rodent models. Additionally, HFD that is associated with hyperglycemia could induce hippocampal ERS, thus impairing insulin signaling and cognitive health in HFD mice. One goal of this study was to determine whether hyperglycemia and hyperlipidemia could cause hippocampal ERS in HFD-induced obese SD rats, and explore the potential mechanisms of ERS regulating hippocampal BDNF and SYN proteins production. Additionally, although regular aerobic exercise could reduce central inflammation and elevate hippocampal BDNF and SYN levels in obese rats, the regulated mechanisms are poorly understood. Nrf2-HO-1 pathways play roles in anti-ERS, anti-inflammation and anti-apoptosis in peripheral tissues. Therefore, the other goal of this study was to determine whether aerobic exercise could activate Nrf2-HO-1 in hippocampus to alleviate obesity-induced hippocampal ERS, which would lead to increased BDNF and SYN levels. Male SD rats were fed on HFD for 8weeks to establish the obese model. Then, 8weeks of aerobic exercise treadmill intervention was arranged for the obese rats. Results showed that HFD-induced obesity caused hyperglycemia and hyperlipidemia, and significantly promoted hippocampal glucose transporter 3 (GLUT3) and fatty acid transport protein 1 (FATP1) protein expression. These results were associated with the activation of hippocampal ERS and ERS-mediated apoptosis. At the same time, we found that excessive hippocampal ERS not only

  14. Combustion instability analysis

    NASA Technical Reports Server (NTRS)

    Chung, T. J.

    1990-01-01

    A theory and computer program for combustion instability analysis are presented. The basic theoretical foundation resides in the concept of entropy-controlled energy growth or decay. Third order perturbation expansion is performed on the entropy-controlled acoustic energy equation to obtain the first order integrodifferential equation for the energy growth factor in terms of the linear, second, and third order energy growth parameters. These parameters are calculated from Navier-Stokes solutions with time averages performed on as many Navier-Stokes time steps as required to cover at least one peak wave period. Applications are made for a 1-D Navier-Stokes solution for the Space Shuttle Main Engine (SSME) thrust chamber with cross section area variations taken into account. It is shown that instability occurs when the mean pressure is set at 2000 psi with 30 percent disturbances. Instability also arises when the mean pressure is set at 2935 psi with 20 percent disturbances. The system with mean pressures and disturbances more adverse that these cases were shown to be unstable.

  15. Chronic ankle instability: Current perspectives

    PubMed Central

    Al-Mohrej, Omar A.; Al-Kenani, Nader S.

    2016-01-01

    Ankle sprain is reported to be among the most common recurrent injuries. About 20% of acute ankle sprain patients develop chronic ankle instability. The failure of functional rehabilitation after acute ankle sprain leads to the development of chronic ankle instability. Differentiation between functional and anatomical ankle instability is very essential to guide the proper treatment. Stability testing by varus stress test and anterior drawer test should be carried out. Subtalar instability is an important pathology that is commonly by passed during the assessment of chronic ankle instability. Unlike acute ankle sprain, chronic ankle instability might require surgical intervention. The surgical and conservative management options can be very much developed by in-depth knowledge of the ankle anatomy, biomechanics, and pathology. Anatomical repair, augmentation by tendon, or both are the basic methods of surgical intervention. Arthroscopy is becoming more popular in the management of chronic ankle instability. PMID:27843798

  16. Robust dynamic mitigation of instabilities

    SciTech Connect

    Kawata, S.; Karino, T.

    2015-04-15

    A dynamic mitigation mechanism for instability growth was proposed and discussed in the paper [S. Kawata, Phys. Plasmas 19, 024503 (2012)]. In the present paper, the robustness of the dynamic instability mitigation mechanism is discussed further. The results presented here show that the mechanism of the dynamic instability mitigation is rather robust against changes in the phase, the amplitude, and the wavelength of the wobbling perturbation applied. Generally, instability would emerge from the perturbation of the physical quantity. Normally, the perturbation phase is unknown so that the instability growth rate is discussed. However, if the perturbation phase is known, the instability growth can be controlled by a superposition of perturbations imposed actively: If the perturbation is induced by, for example, a driving beam axis oscillation or wobbling, the perturbation phase could be controlled, and the instability growth is mitigated by the superposition of the growing perturbations.

  17. Jet-Splitting Instability in Electrospinning of POLY(2-HYDROXYETHYL Methacrylate)

    NASA Astrophysics Data System (ADS)

    Koombhongse, Sureeporn; Reneker, Darrell H.

    2000-03-01

    The electrically charged surface of a polymer fluid becomes unstable when the electrical forces overcome forces of surface tension. A charged jet is then ejected from the surface. The electrical charge carried with the ejected jet can excite instabilities of the jet, which affect its path. A bending instability [1] is frequently observed. In some solutions of poly(2-hydroxyethyl methacrylate) (HEMA), high speed videographic images show that a splitting instability also occurs for the more concentrated solutions. In the splitting instability, a smaller, straight jet is ejected from the primary jet. The splitting instability may be observed before or while the bending instability is growing. In a 20instabilities are dominant. The bending instability became observable when the concentration was reduced to 16more dominant when the concentration was further reduced to 16 1. D. H. Reneker, A. L. Yarin, H. Fong, S. Koombhongse, J. App. Phys, to be published.

  18. Pair Instability Supernovae of Very Massive Population III Stars

    NASA Astrophysics Data System (ADS)

    Chen, Ke-Jung; Heger, Alexander; Woosley, Stan; Almgren, Ann; Whalen, Daniel J.

    2014-09-01

    Numerical studies of primordial star formation suggest that the first stars in the universe may have been very massive. Stellar models indicate that non-rotating Population III stars with initial masses of 140-260 M ⊙ die as highly energetic pair-instability supernovae. We present new two-dimensional simulations of primordial pair-instability supernovae done with the CASTRO code. Our simulations begin at earlier times than previous multidimensional models, at the onset of core contraction, to capture any dynamical instabilities that may be seeded by core contraction and explosive burning. Such instabilities could enhance explosive yields by mixing hot ash with fuel, thereby accelerating nuclear burning, and affect the spectra of the supernova by dredging up heavy elements from greater depths in the star at early times. Our grid of models includes both blue supergiants and red supergiants over the range in progenitor mass expected for these events. We find that fluid instabilities driven by oxygen and helium burning arise at the upper and lower boundaries of the oxygen shell ~20-100 s after core bounce. Instabilities driven by burning freeze out after the SN shock exits the helium core. As the shock later propagates through the hydrogen envelope, a strong reverse shock forms that drives the growth of Rayleigh-Taylor instabilities. In red supergiant progenitors, the amplitudes of these instabilities are sufficient to mix the supernova ejecta.

  19. Pair instability supernovae of very massive population III stars

    SciTech Connect

    Chen, Ke-Jung; Woosley, Stan; Heger, Alexander; Almgren, Ann; Whalen, Daniel J.

    2014-09-01

    Numerical studies of primordial star formation suggest that the first stars in the universe may have been very massive. Stellar models indicate that non-rotating Population III stars with initial masses of 140-260 M {sub ☉} die as highly energetic pair-instability supernovae. We present new two-dimensional simulations of primordial pair-instability supernovae done with the CASTRO code. Our simulations begin at earlier times than previous multidimensional models, at the onset of core contraction, to capture any dynamical instabilities that may be seeded by core contraction and explosive burning. Such instabilities could enhance explosive yields by mixing hot ash with fuel, thereby accelerating nuclear burning, and affect the spectra of the supernova by dredging up heavy elements from greater depths in the star at early times. Our grid of models includes both blue supergiants and red supergiants over the range in progenitor mass expected for these events. We find that fluid instabilities driven by oxygen and helium burning arise at the upper and lower boundaries of the oxygen shell ∼20-100 s after core bounce. Instabilities driven by burning freeze out after the SN shock exits the helium core. As the shock later propagates through the hydrogen envelope, a strong reverse shock forms that drives the growth of Rayleigh-Taylor instabilities. In red supergiant progenitors, the amplitudes of these instabilities are sufficient to mix the supernova ejecta.

  20. Continental Rifts: Lithospheric Weakness and Strength Contrasts as Triggers for Necking Instabilities

    NASA Astrophysics Data System (ADS)

    Wenker, S.; Beaumont, C.

    2014-12-01

    Rifted margin geometry is too complex and diverse to be explained by simple kinematic models. Instead, we consider the effects of strain localization and the growth of necking instabilities as they apply to rifted margins. The intrinsic layering of the lithosphere will affect the growth rate of necking instabilities, leading to depth-dependent extension. In addition, continents are far from homogeneous after multiple cycles of collision, strike-slip motion and rifting. The resulting inherited heterogeneities may serve to localize strain and initiate necking instabilities. We use 2D finite element models containing embedded finite weak zones in the crust and/or mantle as well as a vertical lithospheric boundary across which lithospheric layering changes resulting in an overall strength contrast. We show that there are two controls on the style of rifting: Control 1, the stiff/pliable nature of the lithospheric layers and; Control 2, the distribution of the background strain rate in the lithosphere. Control 1 depends on the lithospheric rheology, such that necking instabilities grow faster in a stiff, dominantly plastic, layer than in equivalent layers with a pliable, mostly viscous, rheology. Control 2 is important where a strength contrast at a lithospheric boundary influences the distribution of the background strain rate. Necking is a mechanism that amplifies the background strain rate, which implies faster necking in parts of the lithosphere where background strain rates are highest. In a laterally homogeneous lithosphere, the background strain rate will be uniform in each layer and Control 1 will dominate giving necking in stiff layers. However, juxtaposed lithospheres with different strengths will distribute strain giving the weaker lithosphere the higher strain rate, implying the fastest necking may occur under Control 2 in pliable layers with the higher strain rate. An end-member case is where strong lithosphere acts as a rigid block. Here, no necking

  1. Rodeo athletes: management of shoulder instability.

    PubMed

    Figueiredo, Eduardo A; Belangero, Paulo S; Cohen, Carina; Louchard, Rafael L; Terra, Bernardo B; Pochini, Alberto C; Andreoli, Carlos V; Cohen, Moisés; Ejnisman, Benno

    2016-05-01

    The aim of this study was to describe epidemiological data and evaluate the clinical results of traumatic anterior glenohumeral instability in rodeo athletes. Thirteen patients, all male, with a mean age of 23.2 (18-31) years old, with anterior glenohumeral instability were include in this study. In 9 patients, the right side was affected. The mean time elapsed between injury and undergoing surgery was 56 months (24-120 months). The surgical technique used (arthroscopic or open bone block procedure) was chosen based on the ISIS (Instability Severity Index Score). Only professional athletes who had been in the sport for at least 60 months were included. Functional evaluation was conducted using the UCLA scale, after a 24-month follow-up period. The number of dislocation episodes varied from 10 to 100 (mean 27 episodes). All of the patients were submitted a surgical treatment open bone block procedure, due to their degree of sport participation, type of sport (forced overhead and collision) and the presence of associated bone defect lesions. According to UCLA criteria, the results were excellent in 12 patients and good in one. The mean time elapsed before returning to the sport was five months, varying between two and ten months. Complications included one patient developing axillary neuropraxia, which was completely resolved six months after the operation, and another patient developed a superficial skin infection. The rodeo athletes with anterior shoulder instability had serious associated bony lesions and has good outcome after bone block procedure.

  2. Family hardship, family instability, and cognitive development.

    PubMed

    Schoon, Ingrid; Jones, Elizabeth; Cheng, Helen; Maughan, Barbara

    2012-08-01

    Associations between the characteristics of the family environment, in particular poverty and family structure, and cognitive development are well established, yet little is known about the role of timing and accumulation of risk in early childhood. The aim of this paper is to assess the associations between income poverty, family instability and cognitive development in early childhood. In particular, it tests the relative role of family economic hardship compared with family instability in affecting cognitive functioning at the age of 5 years. The study draws on data from the UK Millennium Cohort, linking data collected in infancy, age 3, and age 5 years. Cognitive ability was directly assessed at age 5 years with the British Ability Scales. Using regression models we examine associations between persistent income poverty, family transitions, and children's cognitive ability, controlling for family demographics and housing conditions, as well as child characteristics. The findings suggest that the experience of persistent economic hardship as well as very early poverty undermines cognitive functioning at 5 years of age. Family instability shows no significant association with cognitive functioning after controlling for family poverty, family demographics, housing and a set of control variables indicating child characteristics. Persistent poverty is a crucial risk factor undermining children's cognitive development--more so than family instability.

  3. Electrocapillary instability of magnetic fluid peak.

    PubMed

    Mkrtchyan, Levon; Zakinyan, Arthur; Dikansky, Yuri

    2013-07-23

    This Article presents an experimental study of the capillary electrostatic instability occurring under the effect of a constant electric field on a magnetic fluid individual peak. The peaks under study occur at disintegration of a magnetic fluid layer applied on a flat electrode surface under the effect of a perpendicular magnetic field. The electrocapillary instability shows itself as an emission of charged drops jets from the peak point in direction of the opposing electrode. The charged drops emission repeats periodically and results in the peak shape pulsations. It is shown that a magnetic field affects the electrocapillary instability occurrence regularities and can stimulate its development. The critical electric and magnetic field strengths at which the instability occurs have been measured; their dependence on the peak size is shown. The hysteresis in the system has been studied; it consists in that the charged drops emission stops at a lesser electric (or magnetic) field strength than that of the initial occurrence. The peak pulsations frequency depending on the magnetic and electric field strengths and on the peak size has been measured.

  4. Thermal instability of a radiative and resistive coronal plasma

    NASA Technical Reports Server (NTRS)

    Sparks, L.; Van Hoven, G.

    1988-01-01

    Thermal instability is believed to determine the evolution and formation of cool structures in the solar atmosphere such as the transition region and prominences (or filaments). The linear modes that arise in a sheared, force-free, magnetic field due to thermal instability are studied numerically. Previous studies have considered separately modes that arise due to the effects of radiation, compression, anisotropic thermal conduction, and ohmic heating. Here the results of such studies are integrated, first by presenting simple arguments that illustrate the essential physics of ideal, sheared-field, condensation modes, and second by showing numerically how finite resistivity affects the condensational instability in parameter regimes applicable to the solar corona.

  5. Electric Field Induced Interfacial Instabilities

    NASA Technical Reports Server (NTRS)

    Kusner, Robert E.; Min, Kyung Yang; Wu, Xiao-lun; Onuki, Akira

    1999-01-01

    The study of the interface in a charge-free, critical and near-critical binary fluid in the presence of an externally applied electric field is presented. At sufficiently large fields, the interface between the two phases of the binary fluid should become unstable and exhibit an undulation with a predefined wavelength on the order of the capillary length. As the critical point is approached, this wavelength is reduced, potentially approaching length-scales such as the correlation length or critical nucleation radius. At this point the critical properties of the system may be affected. In this paper, the flat interface of a marginally polar binary fluid mixture is stressed by a perpendicular alternating electric field and the resulting instability is characterized by the critical electric field E(sub c) and the pattern observed. The character of the surface dynamics at the onset of instability is found to be strongly dependent on the frequency f of the field applied. The plot of E(sub c) vs. f for a fixed temperature shows a sigmoidal shape, whose low and high frequency limits are well described by a power-law relationship, E(sub c) = epsilon(exp zeta) with zeta = 0.35 and zeta = 0.08, respectively. The low-limit exponent compares well with the value zeta = 4 for a system of conducting and non-conducting fluids. On the other hand, the high-limit exponent coincides with what was first predicted by Onuki. The instability manifests itself as the conducting phase penetrates the non-conducting phase. As the frequency increases, the shape of the pattern changes from an array of bifurcating strings to an array of column-like (or rod-like) protrusions, each of which spans the space between the plane interface and one of the electrodes. For an extremely high frequency, the disturbance quickly grows into a parabolic cone pointing toward the upper plate. As a result, the interface itself changes its shape from that of a plane to that of a high sloping pyramid.

  6. Our plastic age.

    PubMed

    Thompson, Richard C; Swan, Shanna H; Moore, Charles J; vom Saal, Frederick S

    2009-07-27

    Within the last few decades, plastics have revolutionized our daily lives. Globally we use in excess of 260 million tonnes of plastic per annum, accounting for approximately 8 per cent of world oil production. In this Theme Issue of Philosophical Transactions of the Royal Society, we describe current and future trends in usage, together with the many benefits that plastics bring to society. At the same time, we examine the environmental consequences resulting from the accumulation of waste plastic, the effects of plastic debris on wildlife and concerns for human health that arise from the production, usage and disposal of plastics. Finally, we consider some possible solutions to these problems together with the research and policy priorities necessary for their implementation.

  7. Our plastic age

    PubMed Central

    Thompson, Richard C.; Swan, Shanna H.; Moore, Charles J.; vom Saal, Frederick S.

    2009-01-01

    Within the last few decades, plastics have revolutionized our daily lives. Globally we use in excess of 260 million tonnes of plastic per annum, accounting for approximately 8 per cent of world oil production. In this Theme Issue of Philosophical Transactions of the Royal Society, we describe current and future trends in usage, together with the many benefits that plastics bring to society. At the same time, we examine the environmental consequences resulting from the accumulation of waste plastic, the effects of plastic debris on wildlife and concerns for human health that arise from the production, usage and disposal of plastics. Finally, we consider some possible solutions to these problems together with the research and policy priorities necessary for their implementation. PMID:19528049

  8. Suppressing shape instabilities to discover the Bjerknes force instability (L).

    PubMed

    Alibakhshi, Mohammad A; Holt, R Glynn

    2011-11-01

    For sufficiently strong acoustic forcing in a standing wave field, subresonant size bubbles are predicted to be repelled from the pressure antinode. Single bubble sonoluminescence (SBSL) conditions in water do not allow the observation of this instability. This study investigates the possibility that increasing the viscosity of the host liquid can preferentially suppress shape instabilities of a bubble and allow SBSL experiments to be limited by the Bjerknes force instability.

  9. Experimental assessment of unvalidated assumptions in classical plasticity theory.

    SciTech Connect

    Brannon, Rebecca Moss; Burghardt, Jeffrey A.; Bauer, Stephen J.; Bronowski, David R.

    2009-01-01

    This report investigates the validity of several key assumptions in classical plasticity theory regarding material response to changes in the loading direction. Three metals, two rock types, and one ceramic were subjected to non-standard loading directions, and the resulting strain response increments were displayed in Gudehus diagrams to illustrate the approximation error of classical plasticity theories. A rigorous mathematical framework for fitting classical theories to the data, thus quantifying the error, is provided. Further data analysis techniques are presented that allow testing for the effect of changes in loading direction without having to use a new sample and for inferring the yield normal and flow directions without having to measure the yield surface. Though the data are inconclusive, there is indication that classical, incrementally linear, plasticity theory may be inadequate over a certain range of loading directions. This range of loading directions also coincides with loading directions that are known to produce a physically inadmissible instability for any nonassociative plasticity model.

  10. Plasticized phenolphthalein polycarbonate

    NASA Technical Reports Server (NTRS)

    Harrison, E. S.

    1976-01-01

    Phenolphthalein polycarbonate was successfully plasticized with polychlorinated biphenyls (e.g., Aroclor 1231) or tricresyl phosphate and cast from tetrahydrofuran to give clear films without loss of fire resistance. At loadings of 20 to 30 percent plasticizer the Tg was lowered to approximately 100 C which would render phenolphthalein polycarbonate easily moldable. Although these materials had some mechanical integrity as shown by their film forming ability, the room temperature toughness of the plasticized polymer was not significantly improved over unmodified polymer.

  11. Critical stress statistics and a fold catastrophe in intermittent crystal plasticity.

    PubMed

    Derlet, P M; Maaß, R

    2016-09-01

    The statistics and origin of the first discrete plastic event in a one-dimensional dislocation dynamics simulation are studied. This is done via a linear stability analysis of the evolving dislocation configuration up to the onset of irreversible plasticity. It is found that, via a fold catastrophe, the dislocation configuration prior to loading directly determines the stress at which the plastic event occurs and that between one and two trigger dislocations are involved. The resulting irreversible plastic strain arising from the instability is found to be highly correlated with these triggering dislocations.

  12. Critical stress statistics and a fold catastrophe in intermittent crystal plasticity

    NASA Astrophysics Data System (ADS)

    Derlet, P. M.; Maaß, R.

    2016-09-01

    The statistics and origin of the first discrete plastic event in a one-dimensional dislocation dynamics simulation are studied. This is done via a linear stability analysis of the evolving dislocation configuration up to the onset of irreversible plasticity. It is found that, via a fold catastrophe, the dislocation configuration prior to loading directly determines the stress at which the plastic event occurs and that between one and two trigger dislocations are involved. The resulting irreversible plastic strain arising from the instability is found to be highly correlated with these triggering dislocations.

  13. Radiation Induced Genomic Instability

    SciTech Connect

    Morgan, William F.

    2011-03-01

    Radiation induced genomic instability can be observed in the progeny of irradiated cells multiple generations after irradiation of parental cells. The phenotype is well established both in vivo (Morgan 2003) and in vitro (Morgan 2003), and may be critical in radiation carcinogenesis (Little 2000, Huang et al. 2003). Instability can be induced by both the deposition of energy in irradiated cells as well as by signals transmitted by irradiated (targeted) cells to non-irradiated (non-targeted) cells (Kadhim et al. 1992, Lorimore et al. 1998). Thus both targeted and non-targeted cells can pass on the legacy of radiation to their progeny. However the radiation induced events and cellular processes that respond to both targeted and non-targeted radiation effects that lead to the unstable phenotype remain elusive. The cell system we have used to study radiation induced genomic instability utilizes human hamster GM10115 cells. These cells have a single copy of human chromosome 4 in a background of hamster chromosomes. Instability is evaluated in the clonal progeny of irradiated cells and a clone is considered unstable if it contains three or more metaphase sub-populations involving unique rearrangements of the human chromosome (Marder and Morgan 1993). Many of these unstable clones have been maintained in culture for many years and have been extensively characterized. As initially described by Clutton et al., (Clutton et al. 1996) many of our unstable clones exhibit persistently elevated levels of reactive oxygen species (Limoli et al. 2003), which appear to be due dysfunctional mitochondria (Kim et al. 2006, Kim et al. 2006). Interestingly, but perhaps not surprisingly, our unstable clones do not demonstrate a “mutator phenotype” (Limoli et al. 1997), but they do continue to rearrange their genomes for many years. The limiting factor with this system is the target – the human chromosome. While some clones demonstrate amplification of this chromosome and thus lend

  14. Additives in plastics.

    PubMed

    Deanin, R D

    1975-06-01

    The polymers used in plastics are generally harmless. However, they are rarely used in pure form. In almost all commercial plastics, they are "compounded" with monomeric ingredients to improve their processing and end-use performance. In order of total volume used, these monomeric additives may be classified as follows: reinforcing fibers, fillers, and coupling agents; plasticizers; colorants; stabilizers (halogen stabilizers, antioxidants, ultraviolet absorbers, and biological preservatives); processing aids (lubricants, others, and flow controls); flame retardants, peroxides; and antistats. Some information is already available, and much more is needed, on potential toxicity and safe handling of these additives during processing and manufacture of plastics products.

  15. Additives in plastics.

    PubMed Central

    Deanin, R D

    1975-01-01

    The polymers used in plastics are generally harmless. However, they are rarely used in pure form. In almost all commercial plastics, they are "compounded" with monomeric ingredients to improve their processing and end-use performance. In order of total volume used, these monomeric additives may be classified as follows: reinforcing fibers, fillers, and coupling agents; plasticizers; colorants; stabilizers (halogen stabilizers, antioxidants, ultraviolet absorbers, and biological preservatives); processing aids (lubricants, others, and flow controls); flame retardants, peroxides; and antistats. Some information is already available, and much more is needed, on potential toxicity and safe handling of these additives during processing and manufacture of plastics products. PMID:1175566

  16. Plastics and health risks.

    PubMed

    Halden, Rolf U

    2010-01-01

    By 2010, the worldwide annual production of plastics will surpass 300 million tons. Plastics are indispensable materials in modern society, and many products manufactured from plastics are a boon to public health (e.g., disposable syringes, intravenous bags). However, plastics also pose health risks. Of principal concern are endocrine-disrupting properties, as triggered for example by bisphenol A and di-(2-ethylhexyl) phthalate (DEHP). Opinions on the safety of plastics vary widely, and despite more than five decades of research, scientific consensus on product safety is still elusive. This literature review summarizes information from more than 120 peer-reviewed publications on health effects of plastics and plasticizers in lab animals and humans. It examines problematic exposures of susceptible populations and also briefly summarizes adverse environmental impacts from plastic pollution. Ongoing efforts to steer human society toward resource conservation and sustainable consumption are discussed, including the concept of the 5 Rs--i.e., reduce, reuse, recycle, rethink, restrain--for minimizing pre- and postnatal exposures to potentially harmful components of plastics.

  17. Surface properties of beached plastic pellets.

    PubMed

    Fotopoulou, Kalliopi N; Karapanagioti, Hrissi K

    2012-10-01

    The presence of pollutants on plastic debris is an emerging environmental hot topic. Understanding the surface alteration of plastics while in the marine environment increases our understanding of the pollutant-plastic debris interaction. Plastic pellets are widely distributed throughout the world oceans. Eroded and virgin polyethylene (PE) and polypropylene (PP) pellets were studied for their surface properties to better understand the interaction between plastic and compounds in marine environment. Surface properties such as point of zero charge, surface area and pore volume, surface topography, functional groups and acid-base behavior are important factors which affect sorption. Virgin plastic pellets had homogeneous smooth surfaces that do not have any acid-base behavior. Eroded PE demonstrates an altered surface that at seawater pH acquires a negative charge due to ketone groups. The uneven surface and possible functional groups could have been formed from the erosion processes while floating at the sea surface and might explain the interaction of eroded plastics with microbes and metals. Copyright © 2012 Elsevier Ltd. All rights reserved.

  18. Radiative-convective instability

    NASA Astrophysics Data System (ADS)

    Emanuel, Kerry; Wing, Allison A.; Vincent, Emmanuel M.

    2014-03-01

    equilibrium (RCE) is a simple paradigm for the statistical equilibrium the earth's climate would exhibit in the absence of lateral energy transport. It has generally been assumed that for a given solar forcing and long-lived greenhouse gas concentration, such a state would be unique, but recent work suggests that more than one stable equilibrium may be possible. Here we show that above a critical specified sea surface temperature, the ordinary RCE state becomes linearly unstable to large-scale overturning circulations. The instability migrates the RCE state toward one of the two stable equilibria first found by Raymond and Zeng (2000). It occurs when the clear-sky infrared opacity of the lower troposphere becomes so large, owing to high water vapor concentration, that variations of the radiative cooling of the lower troposphere are governed principally by variations in upper tropospheric water vapor. We show that the instability represents a subcritical bifurcation of the ordinary RCE state, leading to either a dry state with large-scale descent, or to a moist state with mean ascent; these states may be accessed by finite amplitude perturbations to ordinary RCE in the subcritical state, or spontaneously in the supercritical state. As first suggested by Raymond (2000) and Sobel et al. (2007), the latter corresponds to the phenomenon of self-aggregation of moist convection, taking the form of cloud clusters or tropical cyclones. We argue that the nonrobustness of self-aggregation in cloud system resolving models may be an artifact of running such models close to the critical temperature for instability.

  19. Chromosome instability syndromes

    SciTech Connect

    1993-12-31

    Chapter 11, discusses chromosome instability syndromes. The focus is on the most extensively studied genotypic chromosomal aberrations which include Bloom syndrome, Fanconi anemia, ataxia telangiectasia, and xeroderma pigmentosum. The great interest in these syndromes is out of proportion to their rare occurrence; however, studies of genotypic chromosome breakage have been inspired by the hope of throwing light on chromosome structure and behavior. A table is given which relates chromosomal aberrations in Bloom syndrome which may cause or promote cancer. 34 refs., 3 figs., 1 tab.

  20. Non-conventional Fishbone Instabilities

    SciTech Connect

    Ya.I. Kolesnichenko; V.V. Lutsenko; V.S. Marchenko; R.B. White

    2004-11-10

    New instabilities of fishbone type are predicted. First, a trapped-particle-induced m = n = 1 instability with the mode structure having nothing to do with the conventional rigid kink displacement. This instability takes place when the magnetic field is weak, so that the precession frequency of the energetic ions is not small as compared to the frequency of the corresponding Alfven continuum at r = 0 and the magnetic shear is small inside the q = 1 radius [the case relevant to spherical tori]. Second, an Energetic Particle Mode fishbone instability driven by circulating particles. Third, a double-kink-mode instability driven by the circulating energetic ions. In particular, the latter can have two frequencies simultaneously: we refer to it as ''doublet'' fishbones. This instability can occur when the radial profile of the energetic ions has an off-axis maximum inside the region of the mode localization.

  1. Weibel instability with nonextensive distribution

    SciTech Connect

    Qiu, Hui-Bin; Liu, Shi-Bing

    2013-10-15

    Weibel instability in plasma, where the ion distribution is isotropic and the electron component of the plasma possesses the anisotropic temperature distribution, is investigated based on the kinetic theory in context of nonextensive statistics mechanics. The instability growth rate is shown to be dependent on the nonextensive parameters of both electron and ion, and in the extensive limit, the result in Maxwellian distribution plasma is recovered. The instability growth rate is found to be enhanced as the nonextensive parameter of electron increases.

  2. Hydrodynamic Instabilities in High-Energy-Density Settings

    NASA Astrophysics Data System (ADS)

    Smalyuk, Vladimir

    2016-10-01

    Our understanding of hydrodynamic instabilities, such as the Rayleigh-Taylor (RT), Richtmyer-Meshkov (RM), and Kelvin-Helmholtz (KH) instabilities, in high-energy-density (HED) settings over past two decades has progressed enormously. The range of conditions where hydrodynamic instabilities are experimentally observed now includes direct and indirect drive inertial confinement fusion (ICF) where surprises continue to emerge, linear and nonlinear regimes, classical interfaces vs. stabilized ablation fronts, tenuous ideal plasmas vs. high density Fermi degenerate plasmas, bulk fluid interpenetration vs. mixing down to the atomic level, in the presence of magnetic fields and/or intense radiation, and in solid state plastic flow at high pressures and strain rates. Regimes in ICF can involve extreme conditions of matter with temperatures up to kilovolts, densities of a thousand times solid densities, and time scales of nanoseconds. On the other hand, scaled conditions can be generated that map to exploding stars (supernovae) with length and time scales of millions of kilometers and hours to days or even years of instability evolution, planetary formation dynamics involving solid-state plastic flow which severely modifies the RT growth and continues to challenge reliable theoretical descriptions. This review will look broadly at progress in probing and understanding hydrodynamic instabilities in these very diverse HED settings, and then will examine a few cases in more depth to illustrate the detailed science involved. Experimental results on large-scale HED facilities such as the Omega, Nike, Gekko, and Shenguang lasers will be reviewed and the latest developments at the National Ignition Facility (NIF) and Z machine will be covered. Finally, current overarching questions and challenges will be summarized to motivate research directions for future. This work was performed under the auspices of the U.S. Department of Energy by LLNL under Contract DE-AC52-07NA27344.

  3. Planetesimal Formation through the Streaming Instability

    NASA Astrophysics Data System (ADS)

    Yang, Chao-Chin; Johansen, Anders; Schäfer, Urs

    2015-12-01

    The streaming instability is a promising mechanism to circumvent the barriers in direct dust growth and lead to the formation of planetesimals, as demonstrated by many previous studies. In order to resolve the thin layer of solids, however, most of these studies were focused on a local region of a protoplanetary disk with a limited simulation domain. It remains uncertain how the streaming instability is affected by the disk gas on large scales, and models that have sufficient dynamical range to capture both the thin particle layer and the large-scale disk dynamics are required.We hereby systematically push the limits of the computational domain up to more than the gas scale height, and study the particle-gas interaction on large scales in the saturated state of the streaming instability and the initial mass function of the resulting planetesimals. To overcome the numerical challenges posed by this kind of models, we have developed a new technique to simultaneously relieve the stringent time step constraints due to small-sized particles and strong local solid concentrations. Using these models, we demonstrate that the streaming instability can drive multiple radial, filamentary concentrations of solids, implying that planetesimals are born in well separated belt-like structures. We also find that the initial mass function of planetesimals via the streaming instability has a characteristic exponential form, which is robust against computational domain as well as resolution. These findings will help us further constrain the cosmochemical history of the Solar system as well as the planet formation theory in general.

  4. Study of cavitating inducer instabilities

    NASA Technical Reports Server (NTRS)

    Young, W. E.; Murphy, R.; Reddecliff, J. M.

    1972-01-01

    An analytic and experimental investigation into the causes and mechanisms of cavitating inducer instabilities was conducted. Hydrofoil cascade tests were performed, during which cavity sizes were measured. The measured data were used, along with inducer data and potential flow predictions, to refine an analysis for the prediction of inducer blade suction surface cavitation cavity volume. Cavity volume predictions were incorporated into a linearized system model, and instability predictions for an inducer water test loop were generated. Inducer tests were conducted and instability predictions correlated favorably with measured instability data.

  5. Instabilities in mimetic matter perturbations

    NASA Astrophysics Data System (ADS)

    Firouzjahi, Hassan; Gorji, Mohammad Ali; Mansoori, Seyed Ali Hosseini

    2017-07-01

    We study cosmological perturbations in mimetic matter scenario with a general higher derivative function. We calculate the quadratic action and show that both the kinetic term and the gradient term have the wrong sings. We perform the analysis in both comoving and Newtonian gauges and confirm that the Hamiltonians and the associated instabilities are consistent with each other in both gauges. The existence of instabilities is independent of the specific form of higher derivative function which generates gradients for mimetic field perturbations. It is verified that the ghost instability in mimetic perturbations is not associated with the higher derivative instabilities such as the Ostrogradsky ghost.

  6. Novel Cauchy-horizon instability

    SciTech Connect

    Maeda, Hideki; Torii, Takashi; Harada, Tomohiro

    2005-03-15

    The evolution of weak discontinuity is investigated on horizons in the n-dimensional static solutions in the Einstein-Maxwell-scalar-{lambda} system, including the Reissner-Nordstroem-(anti) de Sitter black hole. The analysis is essentially local and nonlinear. We find that the Cauchy horizon is unstable, whereas both the black hole event horizon and the cosmological event horizon are stable. This new instability, the so-called kink instability, of the Cauchy horizon is completely different from the well-known 'infinite-blueshift' instability. The kink instability makes the analytic continuation beyond the Cauchy horizon unstable.

  7. PARTIAL TORUS INSTABILITY

    SciTech Connect

    Olmedo, Oscar; Zhang Jie

    2010-07-20

    Flux ropes are now generally accepted to be the magnetic configuration of coronal mass ejections (CMEs), which may be formed prior to or during solar eruptions. In this study, we model the flux rope as a current-carrying partial torus loop with its two footpoints anchored in the photosphere, and investigate its stability in the context of the torus instability (TI). Previous studies on TI have focused on the configuration of a circular torus and revealed the existence of a critical decay index of the overlying constraining magnetic field. Our study reveals that the critical index is a function of the fractional number of the partial torus, defined by the ratio between the arc length of the partial torus above the photosphere and the circumference of a circular torus of equal radius. We refer to this finding as the partial torus instability (PTI). It is found that a partial torus with a smaller fractional number has a smaller critical index, thus requiring a more gradually decreasing magnetic field to stabilize the flux rope. On the other hand, a partial torus with a larger fractional number has a larger critical index. In the limit of a circular torus when the fractional number approaches 1, the critical index goes to a maximum value. We demonstrate that the PTI helps us to understand the confinement, growth, and eventual eruption of a flux-rope CME.

  8. [Genomic instability in atherosclerosis].

    PubMed

    Dzhokhadze, T A; Buadze, T Zh; Gaiozishvili, M N; Kakauridze, N G; Lezhava, T A

    2014-11-01

    A comparative study of the level of genomic instability, parameters of quantitative and structural mutations of chromosomes (aberration, aneuploidy, polyploidy) in lymphocyte cultures from patients with atherosclerosis of age 80 years and older (control group - 30-35 years old) was conducted. The possibility of correction of disturbed genomic indicators by peptide bioregulators - Livagen (Lys-Glu-Asp-Ala) and cobalt ions with separate application or in combination was also studied. Control was lymphocyte culture of two healthy respective age groups. It was also shown that patients with atherosclerosis exhibit high level of genomic instability in all studied parameters, regardless of age, which may suggest that there is marked increase in chromatin condensation in atherosclerosis. It was also shown that Livagen (characterized by modifying influence on chromatin) separately and in combination with cobalt ions, promotes normalization of altered genomic indicators of atherosclerosis in both age groups. The results show that Livagen separately and in combination with cobalt ions has impact on chromatin of patients with atherosclerosis. The identified protective action of Livagen proves its efficacy in prevention of atherosclerosis.

  9. Microtearing instability in ITER*

    NASA Astrophysics Data System (ADS)

    Wong, King-Lap; Mikkelsen, David; Budny, Robert; Breslau, Joshua

    2010-11-01

    Microtearing modes are found to be unstable in some regions of a simulated ITER H-mode plasma [1] with the GS2 code [2]. Modes with kρs>1 are in the interior (r/a˜0.65-0.85) while longer wavelength modes are in the pedestal region. This instability may keep the pedestal within the peeling-ballooning stability boundary [3]. Microtearing modes can produce stochastic magnetic field similar to RMP coils; they may have similar effects on ELMs by increasing the pedestal width. The possibility of using this technique for ELM mitigation in ITER is explored. We propose to use a deuterium gas jet to control the microtearing instability and the Chirikov parameter at the edge. Preliminary evaluation of its effectiveness will be presented and the limitations of the GS2 code will be discussed based on our understanding from NSTX [4]. *This work is supported by USDoE contract DE-AC02-09CH11466. [4pt] [1] R. V. Budny, Nucl. Fusion (2009)[0pt] [2] W. Dorland et al., Phys. Rev. Lett. (2000).[0pt] [3] P. B. Snyder et al.,Nucl. Fusion (2009).[0pt] [4] K. L. Wong et al., Phys. Rev. Lett. (2007).

  10. Partial Torus Instability

    NASA Astrophysics Data System (ADS)

    Olmedo, Oscar; Zhang, Jie

    2010-07-01

    Flux ropes are now generally accepted to be the magnetic configuration of coronal mass ejections (CMEs), which may be formed prior to or during solar eruptions. In this study, we model the flux rope as a current-carrying partial torus loop with its two footpoints anchored in the photosphere, and investigate its stability in the context of the torus instability (TI). Previous studies on TI have focused on the configuration of a circular torus and revealed the existence of a critical decay index of the overlying constraining magnetic field. Our study reveals that the critical index is a function of the fractional number of the partial torus, defined by the ratio between the arc length of the partial torus above the photosphere and the circumference of a circular torus of equal radius. We refer to this finding as the partial torus instability (PTI). It is found that a partial torus with a smaller fractional number has a smaller critical index, thus requiring a more gradually decreasing magnetic field to stabilize the flux rope. On the other hand, a partial torus with a larger fractional number has a larger critical index. In the limit of a circular torus when the fractional number approaches 1, the critical index goes to a maximum value. We demonstrate that the PTI helps us to understand the confinement, growth, and eventual eruption of a flux-rope CME.

  11. Recycling of Reinforced Plastics

    NASA Astrophysics Data System (ADS)

    Adams, R. D.; Collins, Andrew; Cooper, Duncan; Wingfield-Digby, Mark; Watts-Farmer, Archibald; Laurence, Anna; Patel, Kayur; Stevens, Mark; Watkins, Rhodri

    2014-02-01

    This work has shown is that it is possible to recycle continuous and short fibre reinforced thermosetting resins while keeping almost the whole of the original material, both fibres and matrix, within the recyclate. By splitting, crushing hot or cold, and hot forming, it is possible to create a recyclable material, which we designate a Remat, which can then be used to remanufacture other shapes, examples of plates and tubes being demonstrated. Not only can remanufacturing be done, but it has been shown that over 50 % of the original mechanical properties, such as the E modulus, tensile strength, and interlaminar shear strength, can be retained. Four different forms of composite were investigated, a random mat Glass Fibre Reinforced Plastic (GFRP) bathroom component and boat hull, woven glass and carbon fibre cloth impregnated with an epoxy resin, and unidirectional carbon fibre pre-preg. One of the main factors found to affect composite recyclability was the type of resin matrix used in the composite. Thermoset resins tested were shown to have a temperature range around the Glass Transition Temperature (Tg) where they exhibit ductile behaviour, hence aiding reforming of the material. The high-grade carbon fibre prepreg was found to be less easy to recycle than the woven of random fibre laminates. One method of remanufacturing was by heating the Remat to above its glass transition temperature, bending it to shape, and then cooling it. However, unless precautions are taken, the geometric form may revert. This does not happen with the crushed material.

  12. Biodegradation of plastics.

    PubMed

    Shimao, M

    2001-06-01

    Widespread studies on the biodegradation of plastics have been carried out in order to overcome the environmental problems associated with synthetic plastic waste. Recent work has included studies of the distribution of synthetic polymer-degrading microorganisms in the environment, the isolation of new microorganisms for biodegradation, the discovery of new degradation enzymes, and the cloning of genes for synthetic polymer-degrading enzymes.

  13. Detecting plastics in seedcotton

    USDA-ARS?s Scientific Manuscript database

    To increase global market share and value the US cotton industry needs to supply cotton lint that is free of contamination. Removing plastic contamination first requires developing a means to detect plastics in seedcotton. This study was conducted to validate a custom Ion Mobility Spectrometer (IM...

  14. Detecting plastics in seedcotton

    USDA-ARS?s Scientific Manuscript database

    The US cotton industry wants to increase market share and value by supplying pure cotton. Removing contamination requires developing a means to detect plastics in seedcotton. This study was conducted to determine if Ion Mobility Spectrometry (IMS) could be used to find small amounts of plastic in ...

  15. Instability vaccination: A structural design to reduce Rayleigh Taylor instability

    NASA Astrophysics Data System (ADS)

    Esmaeili, Amin

    2013-10-01

    Instability vaccination can be defined as designing a structure to stimulate the system in order to develop immunity against its instability. In this work we have tried to do this stabilization by a new technique. Previously some suppression of R-M instability was done by insertion of magnetic field, but in this work we have tried to do this suppression by proposing a configuration similar to the shape of instability, we call it instability vaccination. This design will reduce the rotations (mostly rotations of Rayleigh Taylor instability) in the fluids that cause more mixing and instabilities. In this paper, we consider the evolution of the interface between two ideal semi-infinite fluid surfaces, using two-dimensional Riemann solver, to solve the Euler equations. First, we performed evolution of a rectangular disorder between the 2 surfaces using two-dimensional Riemann problem for the equations of Euler. Next, the interface was replaced with a perturbation that was part rectangular and part semi-circular (like a mushroom). The simulation was continued till some time steps using the HLL method. We have seen that the rotations of Rayleigh Taylor (R-T) instability were decreased in the second case. Email: amin@cavelab.cs.tsukuba.ac.jp

  16. Applying to plastic surgery residency: factors associated with medical student career choice.

    PubMed

    Greene, Arin K; May, James W

    2008-03-01

    Applications to plastic surgery residency increased 34 percent from 2002 to 2005, despite decreasing applications to other surgical subspecialties. During this period, medical education, reimbursement, work hours, and media coverage have changed. To determine factors responsible for rising applications to plastic surgery residencies, medical student applicants to plastic surgery residencies for 2005 were surveyed. Applicants recorded exposure to plastic surgery during medical school and graded the influence of personality, lifestyle, income potential, and media coverage on their decision to choose plastic surgery training. To further study the effects of plastic surgery exposure on career choice, the percentage of graduating students applying to plastic surgery residency was compared between medical schools with and without plastic surgery training programs. Medical schools that provided greater exposure to plastic surgery and schools with plastic surgery training programs had a higher percentage of graduates applying to plastic surgery residency (p < 0.001). Applicants rated compatibility with the personality of plastic surgeons as a significant factor in their career choice. Lifestyle and income potential were moderately important, whereas media coverage minimally affected career decision. Applicants typically decided on a plastic surgical career during the third year of medical school. Medical student exposure to plastic surgery is the most influential factor in a student's decision to pursue a career in plastic surgery. To continue the increasing applicant trend toward plastic surgery, plastic surgeon engagement of medical students should be emphasized, ideally before the third year of medical school.

  17. Track recording plastic compositions

    NASA Technical Reports Server (NTRS)

    Tarle, Gregory (Inventor)

    1983-01-01

    Improved nuclear track recording plastic compositions are provided which exhibit greatly decreased surface roughness when etched to produce visible tracks of energetic nuclear particles which have passed into and/or through said plastic. The improved compositions incorporate a small quantity of a phthalic acid ester into the major plastic component which is derived from the polymerization of monomeric di-ethylene glycol bis allyl carbonate. Di-substituted phthalic acid esters are preferred as the added component, with the further perference that the ester substituent has a chain length of 2 or more carbon atoms. The inclusion of the phthalic acid ester to an extent of from about 1-2% by weight of the plastic compositions is sufficient to drastically reduce the surface roughness ordinarily produced when the track recording plastic is contacted by etchants.

  18. Cellular detonation - Instability and sub-structure

    NASA Astrophysics Data System (ADS)

    Sugimura, Tadayoshi; Fujiwara, Toshitaka; Lee, John H.

    The present study investigates numerically the instability and irregularity of multidimensional detonations experimentally observed over a lengthy period. By increasing computational resolution significantly, the computed results are able to reproduce most of the salient experimental features like inherent instability of a plane ZND detonation, irregular triple-shock structures seen in self-sustaining detonations, and very fine triple-shock structures superimposed in a macroscopic triple-shock configuration. Under sufficient resolution, the acquired information on the number of triple shocks, regularity and symmetry of wave structure, and detailed substructures of a triple shock configuration are found to be surprisingly incorrect. It is argued that such results would affect the future numerical simulation of detonation initiation, transition, and critical tube diameter problems where the formation of new cells is an essential mechanism.

  19. Thermal radiation in Rayleigh-Benard instability

    NASA Astrophysics Data System (ADS)

    Lienhard, J. H.

    1990-02-01

    Thermal radiation from finite-conductivity boundaries can strongly affect the stability of horizontally unbounded plane fluid layers heated from below. The role of thermal radiation in plane-layer instabilities is studied under the assumption that the fluid medium is transparent (as a model of IR transfer through gas layers). The solution procedure modifies a previous formulation of the conductive boundary problem to account for the gray radiant interchange between boundaries. The nonisothermal character of the boundaries is shown to bias instability toward higher wavenumbers and to substantially increase the stability of fluid layers between radiative nonconductive boundaries relative to layers having nonradiative boundaries. A single layer is studied first, and then a case of parallel interacting fluid layers is considered. Critical Rayleigh numbers are presented as both tabulations and correlations. The implications for solar-collector design are discussed.

  20. Pump instability phenomena generated by fluid forces

    NASA Technical Reports Server (NTRS)

    Gopalakrishnan, S.

    1985-01-01

    Rotor dynamic behavior of high energy centrifugal pumps is significantly affected by two types of fluid forces; one due to the hydraulic interaction of the impeller with the surrounding volute or diffuser and the other due to the effect of the wear rings. The available data on these forces is first reviewed. A simple one degree-of-freedom system containing these forces is analytically solved to exhibit the rotor dynamic effects. To illustrate the relative magnitude of these phenomena, an example of a multistage boiler feed pump is worked out. It is shown that the wear ring effects tend to suppress critical speed and postpone instability onset. But the volute-impeller forces tend to lower the critical speed and the instability onset speed. However, for typical boiler feed pumps under normal running clearances, the wear ring effects are much more significant than the destabilizing hydraulic interaction effects.

  1. Dynamical instability of spark-ignited engines

    SciTech Connect

    Kantor, J.C.

    1984-06-15

    A simple model for spark-ignited engines is proposed in which the residual exhaust gases of a combustion event affect ignition of the subsequent charge. The model is an example of a one-dimensional, discrete, nonlinear mapping of an interval. Laminar flame correlations incorporated within models for ignition exhibit Arrhenius kinetics. Small variations of the ignition time with respect to the expansion cycle alter the work produced by each cycle, thereby altering the exhaust-gas temperature. It is shown that the mixing of hot residual gases with a fresh charge is a sufficient mechanism to produce an instability of the ignition process, resulting in oscillatory behavior. When this instability is compounded with the effects of mixture turbulence, one obtains a novel picture of the well-known phenomenon of cyclic dispersion exhibited by such engines.

  2. Understanding ionospheric instabilities eludes current approaches

    NASA Astrophysics Data System (ADS)

    Bhattacharya, Atreyee

    2012-07-01

    Ionized gases are heavily concentrated in the ionosphere's F zone, the region between 200 and 500 kilometers in altitude, which is critical for transmitting long-distance radio signals on Earth. However, instabilities in the F region plasma, which can last from seconds to hours and can be spread over centimeters to tens of kilometers, disrupt transmission of radio signals. The plasma instabilities, restricted to the equatorial region following sunset, are called equatorial spread F (ESF). Earth-based instruments perceive ESF events as “twinkling” radio signals. ESF events, first detected in the 1930s, affect the performance and reliability of space-borne and ground-based electronic systems; they can disrupt satellite operations and related communications and navigation systems.

  3. Plasticity comparisons between plants and animals: Concepts and mechanisms.

    PubMed

    Borges, Renee M

    2008-06-01

    This review attempts to present an integrated update of the issue of comparisons of phenotypic plasticity between plants and animals by presenting the problem and its integrated solutions via a whole-organism perspective within an evolutionary framework. Plants and animals differ in two important aspects: mobility and longevity. These features can have important implications for plasticity, and plasticity may even have facilitated greater longevity in plants. Furthermore, somatic genetic mosaicism, intra-organismal selection, and genomic instability contribute to the maintenance of an adaptive phenotype that is especially relevant to long-lived plants. It is contended that a cross-kingdom phylogenetic examination of sensors, messengers and responses that constitute the plasticity repertoire would be more useful than dichotomizing the plant and animal kingdoms. Furthermore, physicochemical factors must be viewed cohesively in the signal reception and transduction pathways leading to plastic responses. Comparison of unitary versus modular organisms could also provide useful insights into the range of expected plastic responses. An integrated approach that combines evolutionary theory and evolutionary history with signal-response mechanisms will yield the most insights into phenotypic plasticity in all its forms.

  4. Experiments on Effects of Initial Conditions and Material Strength on Rayleigh-Taylor Instability

    NASA Astrophysics Data System (ADS)

    Roach, Pamela; Banerjee, Arindam

    2013-11-01

    The effects of initial conditions on Rayleigh-Taylor (RT) instability in an accelerated elastic-plastic solid were studied. A novel rotating wheel RT experiment that uses centrifugal forces to accelerate a two-material interface was utilized to study the effect of amplitude and wavelength on RT instability with an elastic-plastic solid. The experiment consists of a container filled with air and mayonnaise, a non-Newtonian emulsion, with an initial perturbation between the two materials. Single mode perturbations of various amplitudes and wavelengths were analyzed and results indicated the acceleration required for instability increased for both decreasing initial amplitude and wavelength. Three-dimensional interfaces were found to be more stable than two-dimensional interfaces. Critical amplitude and growth rates were compared with prior experimental results and analytical growth models. Elastic and plastic peak amplitude responses were observed for stable interfaces using a variable acceleration profile where the test section was first accelerated to slightly below the critical acceleration and then decelerated at the same rate. This exercise allowed for verification of the elastic-plastic (EP) transition process before instability was reached. Authors acknowledge financial support from DOE-LANL subcontract # 173667-1 to Lehigh University and a NSF-Graduate Research Fellowship to Pamela Roach.

  5. The genetics of phenotypic plasticity. X. Variation versus uncertainty

    PubMed Central

    Scheiner, Samuel M; Holt, Robert D

    2012-01-01

    Despite the apparent advantages of adaptive plasticity, it is not common. We examined the effects of variation and uncertainty on selection for plasticity using an individual-based computer simulation model. In the model, the environment consisted of a linear gradient of 50 demes with dispersal occurring either before or after selection. Individuals consisted of multiple loci whose phenotypic expression either are affected (plastic) or are not affected (nonplastic) by the environment. Typically, evolution occurred first as genetic differentiation, which was then replaced by the evolution of adaptive plasticity, opposite to the evolutionary trend that is often assumed. Increasing dispersal rates selected for plasticity, if selection occurred before dispersal. If selection occurred after dispersal, the highest plasticity was at intermediate dispersal rates. Temporal variation in the environment occurring after development, but before selection, favored the evolution of plasticity. With dispersal before selection, such temporal variation resulted in hyperplasticity, with a reaction norm much steeper than the optimum. This effect was enhanced with negative temporal autocorrelation and can be interpreted as representing a form of bet hedging. As the number of nonplastic loci increased, plasticity was disfavored due to an increase in the uncertainty of the genomic environment. This effect was reversed with temporal variation. Thus, variation and uncertainty affect whether or not plasticity is favored with different sources of variation—arising from the amount and timing of dispersal, from temporal variation, and even from the genetic architecture underlying the phenotype—having contrasting, interacting, and at times unexpected effects. PMID:22837824

  6. The Rayleigh-Taylor instability

    NASA Astrophysics Data System (ADS)

    Piriz, A. R.; Cortázar, O. D.; López Cela, J. J.; Tahir, N. A.

    2006-12-01

    A new approach to the Rayleigh-Taylor instability is presented that yields exact solutions for the simplest cases and provides approximate but still very accurate analytical expressions for important and more complex cases involving nonideal fluids. The approach is based on Newton's second law and allows for an intuitive and physically appealing explanation of the mechanisms underlying the instability.

  7. Liquid propellant rocket combustion instability

    NASA Technical Reports Server (NTRS)

    Harrje, D. T.

    1972-01-01

    The solution of problems of combustion instability for more effective communication between the various workers in this field is considered. The extent of combustion instability problems in liquid propellant rocket engines and recommendations for their solution are discussed. The most significant developments, both theoretical and experimental, are presented, with emphasis on fundamental principles and relationships between alternative approaches.

  8. Bony instability of the shoulder.

    PubMed

    Bushnell, Brandon D; Creighton, R Alexander; Herring, Marion M

    2008-09-01

    Instability of the shoulder is a common problem treated by many orthopaedists. Instability can result from baseline intrinsic ligamentous laxity or a traumatic event-often a dislocation that injures the stabilizing structures of the glenohumeral joint. Many cases involve soft-tissue injury only and can be treated successfully with repair of the labrum and ligamentous tissues. Both open and arthroscopic approaches have been well described, with recent studies of arthroscopic soft-tissue techniques reporting results equal to those of the more traditional open techniques. Over the last decade, attention has focused on the concept of instability of the shoulder mediated by bony pathology such as a large bony Bankart lesion or an engaging Hill-Sachs lesion. Recent literature has identified unrecognized large bony lesions as a primary cause of failure of arthroscopic reconstruction for instability, a major cause of recurrent instability, and a difficult diagnosis to make. Thus, although such bony lesions may be relatively rare compared with soft-tissue pathology, they constitute a critically important entity in the management of shoulder instability. Smaller bony lesions may be amenable to arthroscopic treatment, but larger lesions often require open surgery to prevent recurrent instability. This article reviews recent developments in the diagnosis and treatment of bony instability.

  9. Research on aviation fuel instability

    NASA Technical Reports Server (NTRS)

    Baker, C. E.; Bittker, D. A.; Cohen, S. M.; Seng, G. T.

    1983-01-01

    The underlying causes of fuel thermal degradation are discussed. Topics covered include: nature of fuel instability and its temperature dependence, methods of measuring the instability, chemical mechanisms involved in deposit formation, and instrumental methods for characterizing fuel deposits. Finally, some preliminary thoughts on design approaches for minimizing the effects of lowered thermal stability are briefly discussed.

  10. Marital instability after midlife.

    PubMed

    Wu, Z; Penning, M J

    1997-09-01

    "Divorce in later life has been shown to produce dramatic declines in the economic, psychological, and physical well-being of marital partners. This study examines the prevalence and determinants of marital disruption after midlife using Becker's theory of marital instability. Using recent Canadian national data, the marital outcomes of women and men who were married as of age 40 are tracked across the remaining years of the marriage. Cox proportional hazard regression models indicate stabilizing effects of the duration of the marriage, the age at first marriage, the presence of young children, as well as of remarriage for middle-aged and older persons. Other significant risk factors include education, heterogamous marital status, premarital cohabitation, number of siblings, and region."

  11. Instabilities in uranium plasma.

    NASA Technical Reports Server (NTRS)

    Tidman, D. A.

    1971-01-01

    The nonlinear evolution of unstable sound waves in a uranium plasma has been calculated using a multiple time-scale asymptotic expansion scheme. The fluid equations used include the fission power density, radiation diffusion, and the effects of the changing degree of ionization of the uranium atoms. The nonlinear growth of unstable waves is shown to be limited by mode coupling to shorter wavelength waves which are damped by radiation diffusion. This mechanism limits the wave pressure fluctuations to values of order delta P/P equal to about .00001 in the plasma of a typical gas-core nuclear rocket engine. The instability is thus not expected to present a control problem for this engine.

  12. Instabilities in uranium plasma.

    NASA Technical Reports Server (NTRS)

    Tidman, D. A.

    1971-01-01

    The nonlinear evolution of unstable sound waves in a uranium plasma has been calculated using a multiple time-scale asymptotic expansion scheme. The fluid equations used include the fission power density, radiation diffusion, and the effects of the changing degree of ionization of the uranium atoms. The nonlinear growth of unstable waves is shown to be limited by mode coupling to shorter wavelength waves which are damped by radiation diffusion. This mechanism limits the wave pressure fluctuations to values of order delta P/P equal to about .00001 in the plasma of a typical gas-core nuclear rocket engine. The instability is thus not expected to present a control problem for this engine.

  13. Combustion Instabilities Modeled

    NASA Technical Reports Server (NTRS)

    Paxson, Daniel E.

    1999-01-01

    NASA Lewis Research Center's Advanced Controls and Dynamics Technology Branch is investigating active control strategies to mitigate or eliminate the combustion instabilities prevalent in lean-burning, low-emission combustors. These instabilities result from coupling between the heat-release mechanisms of the burning process and the acoustic flow field of the combustor. Control design and implementation require a simulation capability that is both fast and accurate. It must capture the essential physics of the system, yet be as simple as possible. A quasi-one-dimensional, computational fluid dynamics (CFD) based simulation has been developed which may meet these requirements. The Euler equations of mass, momentum, and energy have been used, along with a single reactive species transport equation to simulate coupled thermoacoustic oscillations. A very simple numerical integration scheme was chosen to reduce computing time. Robust boundary condition procedures were incorporated to simulate various flow conditions (e.g., valves, open ends, and choked inflow) as well as to accommodate flow reversals that may arise during large flow-field oscillations. The accompanying figure shows a sample simulation result. A combustor with an open inlet, a choked outlet, and a large constriction approximately two thirds of the way down the length is shown. The middle plot shows normalized, time-averaged distributions of the relevant flow quantities, and the bottom plot illustrates the acoustic mode shape of the resulting thermoacoustic oscillation. For this simulation, the limit cycle peak-to-peak pressure fluctuations were 13 percent of the mean. The simulation used 100 numerical cells. The total normalized simulation time was 50 units (approximately 15 oscillations), which took 26 sec on a Sun Ultra2.

  14. Internal rotor friction instability

    NASA Technical Reports Server (NTRS)

    Walton, J.; Artiles, A.; Lund, J.; Dill, J.; Zorzi, E.

    1990-01-01

    The analytical developments and experimental investigations performed in assessing the effect of internal friction on rotor systems dynamic performance are documented. Analytical component models for axial splines, Curvic splines, and interference fit joints commonly found in modern high speed turbomachinery were developed. Rotor systems operating above a bending critical speed were shown to exhibit unstable subsynchronous vibrations at the first natural frequency. The effect of speed, bearing stiffness, joint stiffness, external damping, torque, and coefficient of friction, was evaluated. Testing included material coefficient of friction evaluations, component joint quantity and form of damping determinations, and rotordynamic stability assessments. Under conditions similar to those in the SSME turbopumps, material interfaces experienced a coefficient of friction of approx. 0.2 for lubricated and 0.8 for unlubricated conditions. The damping observed in the component joints displayed nearly linear behavior with increasing amplitude. Thus, the measured damping, as a function of amplitude, is not represented by either linear or Coulomb friction damper models. Rotordynamic testing of an axial spline joint under 5000 in.-lb of static torque, demonstrated the presence of an extremely severe instability when the rotor was operated above its first flexible natural frequency. The presence of this instability was predicted by nonlinear rotordynamic time-transient analysis using the nonlinear component model developed under this program. Corresponding rotordynamic testing of a shaft with an interference fit joint demonstrated the presence of subsynchronous vibrations at the first natural frequency. While subsynchronous vibrations were observed, they were bounded and significantly lower in amplitude than the synchronous vibrations.

  15. POLYESTER GLASS PLASTICS FOR SHIPBUILDING,

    DTIC Science & Technology

    POLYESTER PLASTICS , SHIP HULLS), (*SHIP HULLS, POLYESTER PLASTICS ), GLASS TEXTILES, REINFORCING MATERIALS, SHIP STRUCTURAL COMPONENTS, COMPOSITE MATERIALS, PROCESSING, CHEMISTRY, HANDBOOKS, BINDERS, USSR

  16. Family Instability and School Readiness in the United Kingdom

    PubMed Central

    Fomby, Paula

    2012-01-01

    I investigate the prevalence of family instability in the United Kingdom and its association with children's school readiness at age 5. Data are from three sweeps of the Millennium Cohort Study (2001–2007). Family instability is measured by mother's self-report of union status changes since her child's birth. Outcome measures include mother assessments of child behavior and standardized scores on cognitive assessments. Maternal education and household income explained the association of family instability with children's emotional behavior and nonverbal ability, but conduct problems and verbal ability remained associated with family instability after accounting for explanatory factors. Compared to children born to married parents, the verbal ability of children born to cohabiting parents was less affected by later family structure change. PMID:22574238

  17. Finite-temperature mechanical instability in disordered lattices

    NASA Astrophysics Data System (ADS)

    Zhang, Leyou; Mao, Xiaoming

    2016-02-01

    Mechanical instability takes different forms in various ordered and disordered systems and little is known about how thermal fluctuations affect different classes of mechanical instabilities. We develop an analytic theory involving renormalization of rigidity and coherent potential approximation that can be used to understand finite-temperature mechanical stabilities in various disordered systems. We use this theory to study two disordered lattices: a randomly diluted triangular lattice and a randomly braced square lattice. These two lattices belong to two different universality classes as they approach mechanical instability at T =0 . We show that thermal fluctuations stabilize both lattices. In particular, the triangular lattice displays a critical regime in which the shear modulus scales as G ˜T1 /2 , whereas the square lattice shows G ˜T2 /3 . We discuss generic scaling laws for finite-T mechanical instabilities and relate them to experimental systems.

  18. Fingering instability of Bingham fluids

    NASA Astrophysics Data System (ADS)

    Ghadge, Shilpa; Myers, Tim

    2005-11-01

    Contact line instabilities have been extensively studied and many useful results obtained for industrial applications. Our research in this area is to explore these instabilities for non-Newtonian fluids which has wide scope in geological, biological as well as industrial areas. In this talk, we will present an analysis of fingering instability near a contact line of the thin sheet of fluid flowing down on a moderately inclined plane. This instability has been well studied for Newtonian fluids. We explore the effect of a yield strength of the fluid on this instability. We have conveniently assumed the presence of the precussor film of small thickness ahead of the fluid film to avoid some mathematical singularities. Using a lubrication-type approximation, we perform a linear stability analysis of a straight contact line. We will show comparison with some experimental results using suspensions of kaolin in silicone oil as a yield strength fluid.

  19. Application of chemical and thermal analysis methods for studying cellulose ester plastics.

    PubMed

    Schilling, Michael; Bouchard, Michel; Khanjian, Herant; Learner, Tom; Phenix, Alan; Rivenc, Rachel

    2010-06-15

    Cellulose acetate, developed about 100 years ago as a versatile, semisynthetic plastic material, is used in a variety of applications and is perhaps best known as the basis of photographic film stock. Objects made wholly or partly from cellulose acetate are an important part of modern and contemporary cultural heritage, particularly in museum collections. Given the potential instability of the material, however, it is imperative to understand the aging mechanisms and deterioration pathways of cellulose ester plastics to mitigate decomposition and formulate guidelines for storage, exhibition, and conservation. One important aspect of this process is the ability to fully characterize the plastic, because variations in composition affect its aging properties and ultimate stability. In this Account, we assess the potential of a range of analytical techniques for plastics made from cellulose acetate, cellulose propionate, and cellulose butyrate. Comprehensive characterization of cellulose ester plastics is best achieved by applying several complementary analytical techniques. Fourier-transform IR (FTIR) and Raman spectroscopy provide rapid means for basic characterization of plastic objects, which can be useful for quick, noninvasive screening of museum collections with portable instruments. Pyrolysis GC/MS is capable of differentiating the main types of cellulose ester polymers but also permits a richly detailed compositional analysis of additives. Thermal analysis techniques provide a wealth of compositional information and thermal behavior. Thermogravimetry (TG) allows for quantitative analysis of thermally stable volatile additives, and weight-difference curves offer a novel means for assessing oxidative stability. The mechanical response to temperature, such as the glass transition, can be measured with dynamic mechanical analysis (DMA), but results from other thermal analysis techniques such as TG, differential scanning calorimetry (DSC), and dynamic load

  20. Gravitational Instabilities in Circumstellar Disks

    NASA Astrophysics Data System (ADS)

    Kratter, Kaitlin; Lodato, Giuseppe

    2016-09-01

    Star and planet formation are the complex outcomes of gravitational collapse and angular momentum transport mediated by protostellar and protoplanetary disks. In this review, we focus on the role of gravitational instability in this process. We begin with a brief overview of the observational evidence for massive disks that might be subject to gravitational instability and then highlight the diverse ways in which the instability manifests itself in protostellar and protoplanetary disks: the generation of spiral arms, small-scale turbulence-like density fluctuations, and fragmentation of the disk itself. We present the analytic theory that describes the linear growth phase of the instability supplemented with a survey of numerical simulations that aim to capture the nonlinear evolution. We emphasize the role of thermodynamics and large-scale infall in controlling the outcome of the instability. Despite apparent controversies in the literature, we show a remarkable level of agreement between analytic predictions and numerical results. In the next part of our review, we focus on the astrophysical consequences of the instability. We show that the disks most likely to be gravitationally unstable are young and relatively massive compared with their host star, Md/M*≥0.1. They will develop quasi-stable spiral arms that process infall from the background cloud. Although instability is less likely at later times, once infall becomes less important, the manifestations of the instability are more varied. In this regime, the disk thermodynamics, often regulated by stellar irradiation, dictates the development and evolution of the instability. In some cases the instability may lead to fragmentation into bound companions. These companions are more likely to be brown dwarfs or stars than planetary mass objects. Finally, we highlight open questions related to the development of a turbulent cascade in thin disks and the role of mode-mode coupling in setting the maximum angular

  1. A comparative study of Rayleigh-Taylor and Richtmyer-Meshkov instabilities in 2D and 3D in tantalum

    NASA Astrophysics Data System (ADS)

    Sternberger, Z.; Maddox, B. R.; Opachich, Y. P.; Wehrenberg, C. E.; Kraus, R. G.; Remington, B. A.; Randall, G. C.; Farrell, M.; Ravichandran, G.

    2017-01-01

    Driving a shock wave through the interface between two materials with different densities can result in the Richtmyer-Meshkov or Rayleigh-Taylor instability and initial perturbations at the interface will grow. If the shock wave is sufficiently strong, the instability will lead to plastic flow at the interface. Material strength will reduce the amount of plastic flow and suppress growth. While such instabilities have been investigated in 2D, no studies of this phenomena have been performed in 3D on materials with strength. Initial perturbations to seed the hydrodynamic instability were coined into tantalum recovery targets. Two types of perturbations were used, two dimensional (2D) perturbations (hill and valley) and three-dimensional (3D) perturbations (egg crate pattern). The targets were subjected to dynamic loading using the Janus laser at the Jupiter Laser Facility. Shock pressures ranged from 50 GPa up to 150 GPa and were calibrated using VISAR drive targets.

  2. Production of Methane and Water from Crew Plastic Waste

    NASA Technical Reports Server (NTRS)

    Captain, Janine; Santiago, Eddie; Parrish, Clyde; Strayer, Richard F.; Garland, Jay L.

    2008-01-01

    Recycling is a technology that will be key to creating a self sustaining lunar outpost. The plastics used for food packaging provide a source of material that could be recycled to produce water and methane. The recycling of these plastics will require some additional resources that will affect the initial estimate of starting materials that will have to be transported from earth, mainly oxygen, energy and mass. These requirements will vary depending on the recycling conditions. The degredation products of these plastics will vary under different atmospheric conditions. An estimate of the the production rate of methane and water using typical ISRU processes along with the plastic recycling will be presented.

  3. Candidate Genes in Ocular Dominance Plasticity

    PubMed Central

    Rietman, M. Liset; Sommeijer, J.-P.; Levelt, Christiaan N.; Heimel, J. Alexander

    2012-01-01

    Many studies have been devoted to the identification of genes involved in experience-dependent plasticity in the visual cortex. To discover new candidate genes, we have reexamined data from one such study on ocular dominance (OD) plasticity in recombinant inbred BXD mouse strains. We have correlated the level of plasticity with the gene expression data in the neocortex that have become available for these same strains. We propose that genes with a high correlation are likely to play a role in OD plasticity. We have tested this hypothesis for genes whose inactivation is known to affect OD plasticity. The expression levels of these genes indeed correlated with OD plasticity if their levels showed strong differences between the BXD strains. To narrow down our candidate list of correlated genes, we have selected only those genes that were previously found to be regulated by visual experience and associated with pathways implicated in OD plasticity. This resulted in a list of 32 candidate genes. The list contained unproven, but not unexpected candidates such as the genes for IGF-1, NCAM1, NOGO-A, the gamma2 subunit of the GABA(A) receptor, acetylcholine esterase, and the catalytic subunit of cAMP-dependent protein kinase A. This demonstrates the viability of our approach. More interestingly, the following novel candidate genes were identified: Akap7, Akt1, Camk2d, Cckbr, Cd44, Crim1, Ctdsp2, Dnajc5, Gnai1, Itpka, Mapk8, Nbea, Nfatc3, Nlk, Npy5r, Phf21a, Phip, Ppm1l, Ppp1r1b, Rbbp4, Slc1a3, Slit2, Socs2, Spock3, St8sia1, Zfp207. Whether all these novel candidates indeed function in OD plasticity remains to be established, but possible roles of some of them are discussed in the article. PMID:22347157

  4. Onset of Plasticity in Thin Polystyrene Films

    NASA Astrophysics Data System (ADS)

    Gurmessa, Bekele J.; Croll, Andrew B.

    2013-02-01

    Polymer glasses have numerous advantageous mechanical properties in comparison to other materials. One of the most useful is the high degree of toughness that can be achieved due to significant yield occurring in the material. Remarkably, the onset of plasticity in polymeric materials is very poorly quantified, despite its importance as the ultimate limit of purely elastic behavior. Here, we report the results of a novel experiment which is extremely sensitive to the onset of yield and discuss its impact on measurement and elastic theory. In particular, we use an elastic instability to locally bend and impart a local tensile stress in a thin, glassy polystyrene film, and directly measure the resulting residual stress caused by the bending. We show that plastic failure is initiated at extremely low strains, of the order 10-3 for polystyrene. Not only is this critical strain found to be small in comparison to bulk measurement, we show that it is influenced by thin film confinement—leading to an increase in the critical strain for plastic failure as film thickness approaches zero.

  5. Onset of plasticity in thin polystyrene films.

    PubMed

    Gurmessa, Bekele J; Croll, Andrew B

    2013-02-15

    Polymer glasses have numerous advantageous mechanical properties in comparison to other materials. One of the most useful is the high degree of toughness that can be achieved due to significant yield occurring in the material. Remarkably, the onset of plasticity in polymeric materials is very poorly quantified, despite its importance as the ultimate limit of purely elastic behavior. Here, we report the results of a novel experiment which is extremely sensitive to the onset of yield and discuss its impact on measurement and elastic theory. In particular, we use an elastic instability to locally bend and impart a local tensile stress in a thin, glassy polystyrene film, and directly measure the resulting residual stress caused by the bending. We show that plastic failure is initiated at extremely low strains, of the order 10(-3) for polystyrene. Not only is this critical strain found to be small in comparison to bulk measurement, we show that it is influenced by thin film confinement--leading to an increase in the critical strain for plastic failure as film thickness approaches zero.

  6. Influence Of The Plastic Material Behaviour On The Prediction Of Forming Limits

    NASA Astrophysics Data System (ADS)

    Vegter, H.; ten Horn, C. H. L. J.; van den Boogaard, A. H.

    2007-05-01

    Prediction of the onset of necking is of large importance in reliability of forming simulation in present automotive industry. Advanced material models require accurate descriptions of the plastic material behaviour including the effect of strain rate. The usual approach for identifying the forming limits in industry is the comparison of a calculated strain map (major against minor strain) with a measured forming limit curve. This approach does not take into account the influence of strain path changes. Prediction of forming limit curves with classical material models can already demonstrate that the forming limits are influenced by this strain path change effect. Including the effect of strain rate on the plastic material behaviour has a strong influence in prediction of onset of instability. Neglecting this effect leads to underestimation of forming capacity of the material in stretch forming parts in particular. The shape of the yield locus will influence the predicted forming limit curves in the region from plane strain to bi-axial. Damage controlled failure will become more important using (advanced) high strength steels. This will affect the stress strain curve at high deformation grades. The work hardening is not only controlled by dislocation interaction, but also by void growth and possible presence of micro-cracks at the interface between the hard en soft phases.

  7. Temperature anisotropy and beam type whistler instabilities

    NASA Technical Reports Server (NTRS)

    Hashimoto, K.; Matsumoto, H.

    1976-01-01

    Whistler instabilities have been investigated for two different types; i.e., a temperature-anisotropy type instability and a beam-type instability. A comparison between the two types of whistler instabilities is made within the framework of linear theory. A transition from one type to the other is also discussed, which is an extension of the work on electrostatic beam and Landau instabilities performed by O'Neil and Malmberg (1968) for electromagnetic whistler instabilities. It is clarified that the essential source of the whistler instability is not beam kinetic energy but a temperature anisotropy, even for the beam-type whistler instability.

  8. Multi-Dimensional Combustion Instability Analysis of Solid Propellant Rocket Motors.

    DTIC Science & Technology

    2014-09-26

    that vortex shedding may lead to an instability in solid propellant rocket motors. It is quite possible that high speed mean flows also affect the...significant [7-13]. Although it can be ar- gued that the hydrodynamic instability may not occur in high Reynolds numbers, the turbulent shear layer...can be significant [7-13]. Although it -(U + ] u 0 (2) can be argued that the hydrodynamic instability may Re i,jj 3 jji not occur in high Reynolds

  9. Instability-driven electromagnetic fields in coronal plasmas

    SciTech Connect

    Manuel, M. J.-E.; Li, C. K.; Seguin, F. H.; Sinenian, N.; Frenje, J. A.; Casey, D. T.; Petrasso, R. D.; Hager, J. D.; Betti, R.; Hu, S. X.; Delettrez, J.; Meyerhofer, D. D.

    2013-04-15

    Filamentary electromagnetic fields previously observed in the coronae of laser-driven spherical targets [F. H. S eguin et al., Phys. Plasma. 19, 012701 (2012)] have been further investigated in laser irradiated plastic foils. Face-on proton-radiography provides an axial view of these filaments and shows coherent cellular structure regardless of initial foil-surface conditions. The observed cellular fields are shown to have an approximately constant scale size of 210 lm throughout the plasma evolution. A discussion of possible field-generation mechanisms is provided and it is demonstrated that the likely source of the cellular field structure is the magnetothermal instability. Using predicted temperature and density profiles, the fastest growing modes of this instability were found to be slowly varying in time and consistent with the observed cellular size.

  10. Instability-driven electromagnetic fields in coronal plasmas

    DOE PAGES

    Manuel, M. J.-E.; Li, C. K.; Seguin, F. H.; ...

    2013-04-15

    Filamentary electromagnetic fields previously observed in the coronae of laser-driven spherical targets [F. H. S eguin et al., Phys. Plasma. 19, 012701 (2012)] have been further investigated in laser irradiated plastic foils. Face-on proton-radiography provides an axial view of these filaments and shows coherent cellular structure regardless of initial foil-surface conditions. The observed cellular fields are shown to have an approximately constant scale size of 210 lm throughout the plasma evolution. A discussion of possible field-generation mechanisms is provided and it is demonstrated that the likely source of the cellular field structure is the magnetothermal instability. Using predicted temperature andmore » density profiles, the fastest growing modes of this instability were found to be slowly varying in time and consistent with the observed cellular size.« less

  11. A Plastic Menagerie

    ERIC Educational Resources Information Center

    Hadley, Mary Jane

    2010-01-01

    Bobble heads had become quite popular, depicting all sorts of sports figures, animals, and even presidents. In this article, the author describes how her fourth graders made bobble head sculptures out of empty plastic drink bottles. (Contains 1 online resource.)

  12. Shape-Shifting Plastic

    SciTech Connect

    2015-05-20

    A new plastic developed by ORNL and Washington State University transforms from its original shape through a series of temporary shapes and returns to its initial form. The shape-shifting process is controlled through changes in temperature

  13. Dreaming in plastic

    NASA Astrophysics Data System (ADS)

    Korzhov, Marianna; Andelman, David; Shikler, Rafi

    2008-07-01

    Plastic is one of the most versatile materials available. It is cheap, flexible and easy to process, and as a result it is all around us - from our computer keyboards to the soles of our shoes. One of its most common applications is as an insulating coating for electric wires; indeed, plastic is well known for its insulating characteristics. It came as something of a surprise, therefore, when in the late 1970s a new generation of plastics was discovered that displayed exactly the opposite behaviour - the ability to conduct electricity. In fact, plastics can be made with a whole range of conductivities - there are polymer materials that behave like semiconductors and there are those that can conduct as well as metals. This discovery sparked a revolution in the electronics community, and three decades of research effort is now yielding a range of stunning new applications for this ubiquitous material.

  14. Strain avalanches in plasticity

    NASA Astrophysics Data System (ADS)

    Argon, A. S.

    2013-09-01

    Plastic deformation at the mechanism level in all solids occurs in the form of discrete thermally activated individual stress relaxation events. While there are clear differences in mechanisms between dislocation mediated events in crystalline solids and by individual shear transformations in amorphous metals and semiconductors, such relaxation events interact strongly to form avalanches of strain bursts. In all cases the attendant distributions of released energy as amplitudes of acoustic emissions, or in serration amplitudes in flow stress, the levels of strain bursts are of fractal character with fractal exponents in the range from -1.5 to -2.0, having the character of phenomena of self-organized criticality, SOC. Here we examine strain avalanches in single crystals of ice, hcp metals, the jerky plastic deformations of nano-pillars of fcc and bcc metals deforming in compression, those in the plastic flow of bulk metallic glasses, all demonstrating the remarkable universality of character of plastic relaxation events.

  15. A Plastic Menagerie

    ERIC Educational Resources Information Center

    Hadley, Mary Jane

    2010-01-01

    Bobble heads had become quite popular, depicting all sorts of sports figures, animals, and even presidents. In this article, the author describes how her fourth graders made bobble head sculptures out of empty plastic drink bottles. (Contains 1 online resource.)

  16. Mechanical plasticity of cells

    NASA Astrophysics Data System (ADS)

    Bonakdar, Navid; Gerum, Richard; Kuhn, Michael; Spörrer, Marina; Lippert, Anna; Schneider, Werner; Aifantis, Katerina E.; Fabry, Ben

    2016-10-01

    Under mechanical loading, most living cells show a viscoelastic deformation that follows a power law in time. After removal of the mechanical load, the cell shape recovers only incompletely to its original undeformed configuration. Here, we show that incomplete shape recovery is due to an additive plastic deformation that displays the same power-law dynamics as the fully reversible viscoelastic deformation response. Moreover, the plastic deformation is a constant fraction of the total cell deformation and originates from bond ruptures within the cytoskeleton. A simple extension of the prevailing viscoelastic power-law response theory with a plastic element correctly predicts the cell behaviour under cyclic loading. Our findings show that plastic energy dissipation during cell deformation is tightly linked to elastic cytoskeletal stresses, which suggests the existence of an adaptive mechanism that protects the cell against mechanical damage.

  17. Art and Plastic Surgery.

    PubMed

    Fernandes, Julio Wilson; Metka, Susanne

    2016-04-01

    The roots of science and art of plastic surgery are very antique. Anatomy, drawing, painting, and sculpting have been very important to the surgery and medicine development over the centuries. Artistic skills besides shape, volume, and lines perception can be a practical aid to the plastic surgeons' daily work. An overview about the interactions between art and plastic surgery is presented, with a few applications to rhinoplasty, cleft lip, and other reconstructive plastic surgeries. This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266.

  18. Physics in Plastics Technology.

    ERIC Educational Resources Information Center

    Thomas, Ken

    1980-01-01

    Discusses the increasing role of the physicist in plastics technology. Relationships of molecular structure to material behavior, design which is related to the material, and the practical problems of fabricating a material into an article are included. (HM)

  19. Sawtooth Instability in the Compact Toroidal Hybrid

    NASA Astrophysics Data System (ADS)

    Herfindal, J. L.; Maurer, D. A.; Hartwell, G. J.; Ennis, D. A.; Knowlton, S. F.

    2015-11-01

    Sawtooth instabilities have been observed in the Compact Toroidal Hybrid (CTH), a current-carrying stellarator/tokamak hybrid device. The sawtooth instability is driven by ohmic heating of the core plasma until the safety factor drops below unity resulting in the growth of an m = 1 kink-tearing mode. Experiments varying the vacuum rotational transform from 0.02 to 0.13 are being conducted to study sawtooth property dependance on vacuum flux surface structure. The frequency of the sawtooth oscillations increase from 2 kHz to 2.8 kHz solely due the decrease in rise time of the oscillation, the crash time is unchanged. CTH has three two-color SXR cameras, a three-channel 1mm interferometer, and a new bolometer system capable of detecting the signatures of sawtooth instabilities. The new bolometer system consists of two cameras, each containing a pair of diode arrays viewing the plasma directly or through a beryllium filter. Electron temperature measurements are found with the two-color SXR cameras through a ratio of the SXR intensities. Impurity radiation can drastically affect the electron temperature measurement, therefore new filters consisting of aluminum and carbon were selected to avoid problematic line radiation while maximizing the signal for a 100 eV plasma. This work is supported by U.S. Department of Energy Grant No. DE-FG02-00ER54610.

  20. Flow Instability in Baffled Channel Flow

    NASA Astrophysics Data System (ADS)

    Kang, Changwoo; Yang, Kyung-Soo; Lee, Kyongjun

    2010-11-01

    Flow instability of baffled channel flow, where thin baffles are mounted on both channel walls periodically in the direction of the main flow, has been numerically investigated. Flow in a baffled channel is regarded as a simple model for flow in finned heat exchangers, including micro channels. In baffled channel flow, flow characteristics are significantly affected by geometrical configuration of the baffles. Two key parameters were considered, namely baffle interval (L) and Reynolds number (Re) of the main flow. The baffle height is fixed as one quarter of the channel height (H). By using a parametric study, we elucidate dependency of the primary instability, a Hopf bifurcation from steady to a time-periodic flow, on L. It turned out that the most unstable flow is obtained with L/H=3. Transition of two-dimensional (2D) time-periodic flow to three-dimensional (3D) flow is initiated by a secondary instability (SI). Floquet stability analysis was performed to identify the critical Reynolds number of SI for some selected baffle intervals. Several distinct modes were identified, and dependency of SI on L was elucidated. A 3D simulation was finally carried out to confirm the Floquet analysis. The current results shed light on understanding flow characteristics of a finned heat exchanger.

  1. Ionospheric feedback instability and substorm development

    NASA Astrophysics Data System (ADS)

    Streltsov, A. V.; Pedersen, T. R.; Mishin, E. V.; Snyder, A. L.

    2010-07-01

    We report on ground magnetic and optical observations performed during an ionospheric heating experiment at the High Frequency Active Auroral Research Program (HAARP) facility in Alaska on 29 October 2008. The experiment was aimed at generation of large-amplitude ULF electromagnetic waves by triggering and facilitating development of the ionospheric feedback instability (IFI) in the region adjacent to a bright auroral arc. In this region the downward/return magnetic field-aligned current decreases plasma density and enhances the electric field in the ionosphere. A combination of these two effects creates favorable conditions for the instability. The experiment occurred during a period of substorm activity, but effects from the HAARP transmitter were not sufficiently intense to be detected against the background of strong natural oscillations occurring farther north from the HAARP site. Thus the experiment did not provide concrete evidence that heating of the ionosphere with powerful HF transmitters can affect IFI development or generate intense ULF electromagnetic waves. However, during the experiment ground-based magnetometers in Alaska and Canada detected large-amplitude ULF waves in regions where the substorm onset auroral arcs interacted with the ionosphere. The frequencies of these waves closely matched frequencies predicted by simulations of IFI for these particular geophysical conditions. These observations support the hypothesis that geomagnetic substorms, the corresponding dynamics of discrete auroral arcs, and the ionospheric feedback instability are closely connected phenomena.

  2. ROTATIONAL INSTABILITIES AND CENTRIFUGAL HANGUP

    SciTech Connect

    K. NEW; J. CENTRELLA

    2000-12-01

    One interesting class of gravitational radiation sources includes rapidly rotating astrophysical objects that encounter dynamical instabilities. We have carried out a set of simulations of rotationally induced instabilities in differentially rotating polytropes. An n=1.5 polytrope with the Maclaurin rotation law will encounter the m=2 bar instability at T/{vert_bar}W{vert_bar} {ge} 0.27. Our results indicate that the remnant of this in-stability is a persistent bar-like structure that emits a long-lived gravitational radiation signal. Furthermore, dynamical instability is shown to occur in n=3.33 polytropes with the j-constant rotation law at T/{vert_bar}W{vert_bar} {ge} 0:14. In this case, the dominant mode of instability is m=1. Such instability may allow a centrifugally-hung core to begin collapsing to neutron star densities on a dynamical timescale. If it occurs in a supermassive star, it may produce gravitational radiation detectable by LISA.

  3. A Multi-Parameter Approach for Calculating Crack Instability

    NASA Technical Reports Server (NTRS)

    Zanganeh, M.; Forman, R. G.

    2014-01-01

    An accurate fracture control analysis of spacecraft pressure systems, boosters, rocket hardware and other critical low-cycle fatigue cases where the fracture toughness highly impacts cycles to failure requires accurate knowledge of the material fracture toughness. However, applicability of the measured fracture toughness values using standard specimens and transferability of the values to crack instability analysis of the realistically complex structures is refutable. The commonly used single parameter Linear Elastic Fracture Mechanics (LEFM) approach which relies on the key assumption that the fracture toughness is a material property would result in inaccurate crack instability predictions. In the past years extensive studies have been conducted to improve the single parameter (K-controlled) LEFM by introducing parameters accounting for the geometry or in-plane constraint effects]. Despite the importance of the thickness (out-of-plane constraint) effects in fracture control problems, the literature is mainly limited to some empirical equations for scaling the fracture toughness data] and only few theoretically based developments can be found. In aerospace hardware where the structure might have only one life cycle and weight reduction is crucial, reducing the design margin of safety by decreasing the uncertainty involved in fracture toughness evaluations would result in lighter hardware. In such conditions LEFM would not suffice and an elastic-plastic analysis would be vital. Multi-parameter elastic plastic crack tip field quantifying developments combined with statistical methods] have been shown to have the potential to be used as a powerful tool for tackling such problems. However, these approaches have not been comprehensively scrutinized using experimental tests. Therefore, in this paper a multi-parameter elastic-plastic approach has been used to study the crack instability problem and the transferability issue by considering the effects of geometrical

  4. Laser cutting plastic materials

    SciTech Connect

    Van Cleave, R.A.

    1980-08-01

    A 1000-watt CO/sub 2/ laser has been demonstrated as a reliable production machine tool for cutting of plastics, high strength reinforced composites, and other nonmetals. More than 40 different plastics have been laser cut, and the results are tabulated. Applications for laser cutting described include fiberglass-reinforced laminates, Kevlar/epoxy composites, fiberglass-reinforced phenolics, nylon/epoxy laminates, ceramics, and disposable tooling made from acrylic.

  5. The plastic-associated microorganisms of the North Pacific Gyre.

    PubMed

    Carson, Henry S; Nerheim, Magnus S; Carroll, Katherine A; Eriksen, Marcus

    2013-10-15

    Microorganisms likely mediate processes affecting the fate and impacts of marine plastic pollution, including degradation, chemical adsorption, and colonization or ingestion by macroorganisms. We investigated the relationship between plastic-associated microorganism communities and factors such as location, temperature, salinity, plankton abundance, plastic concentration, item size, surface roughness, and polymer type. Small plastic items from the surface of the North Pacific Gyre in 2011 were examined using scanning electron microscopy. Bacillus bacteria (mean 1664 ± 247 individuals mm(-2)) and pennate diatoms (1097 ± 154 mm(-2)) were most abundant, with coccoid bacteria, centric diatoms, dinoflagellates, coccolithophores, and radiolarians present. Bacterial abundance was patchy, but increased on foamed polystyrene. Diatom abundance increased on items with rough surfaces and at sites with high plastic concentrations. Morphotype richness increased slightly on larger fragments, and a biogeographic transition occurred between pennate diatom groups. Better characterizing this community will aid in understanding how it interacts with plastic pollution. Copyright © 2013 Elsevier Ltd. All rights reserved.

  6. Neuronal plasticity and thalamocortical sleep and waking oscillations.

    PubMed

    Timofeev, Igor

    2011-01-01

    Throughout life, thalamocortical (TC) network alternates between activated states (wake or rapid eye movement sleep) and slow oscillatory state dominating slow-wave sleep. The patterns of neuronal firing are different during these distinct states. I propose that due to relatively regular firing, the activated states preset some steady state synaptic plasticity and that the silent periods of slow-wave sleep contribute to a release from this steady state synaptic plasticity. In this respect, I discuss how states of vigilance affect short-, mid-, and long-term synaptic plasticity, intrinsic neuronal plasticity, as well as homeostatic plasticity. Finally, I suggest that slow oscillation is intrinsic property of cortical network and brain homeostatic mechanisms are tuned to use all forms of plasticity to bring cortical network to the state of slow oscillation. However, prolonged and profound shift from this homeostatic balance could lead to development of paroxysmal hyperexcitability and seizures as in the case of brain trauma.

  7. Neuronal plasticity and thalamocortical sleep and waking oscillations

    PubMed Central

    Timofeev, Igor

    2011-01-01

    Throughout life, thalamocortical (TC) network alternates between activated states (wake or rapid eye movement sleep) and slow oscillatory state dominating slow-wave sleep. The patterns of neuronal firing are different during these distinct states. I propose that due to relatively regular firing, the activated states preset some steady state synaptic plasticity and that the silent periods of slow-wave sleep contribute to a release from this steady state synaptic plasticity. In this respect, I discuss how states of vigilance affect short-, mid-, and long-term synaptic plasticity, intrinsic neuronal plasticity, as well as homeostatic plasticity. Finally, I suggest that slow oscillation is intrinsic property of cortical network and brain homeostatic mechanisms are tuned to use all forms of plasticity to bring cortical network to the state of slow oscillation. However, prolonged and profound shift from this homeostatic balance could lead to development of paroxysmal hyperexcitability and seizures as in the case of brain trauma. PMID:21854960

  8. Global change and the evolution of phenotypic plasticity in plants.

    PubMed

    Matesanz, Silvia; Gianoli, Ernesto; Valladares, Fernando

    2010-09-01

    Global change drivers create new environmental scenarios and selective pressures, affecting plant species in various interacting ways. Plants respond with changes in phenology, physiology, and reproduction, with consequences for biotic interactions and community composition. We review information on phenotypic plasticity, a primary means by which plants cope with global change scenarios, recommending promising approaches for investigating the evolution of plasticity and describing constraints to its evolution. We discuss the important but largely ignored role of phenotypic plasticity in range shifts and review the extensive literature on invasive species as models of evolutionary change in novel environments. Plasticity can play a role both in the short-term response of plant populations to global change as well as in their long-term fate through the maintenance of genetic variation. In new environmental conditions, plasticity of certain functional traits may be beneficial (i.e., the plastic response is accompanied by a fitness advantage) and thus selected for. Plasticity can also be relevant in the establishment and persistence of plants in novel environments that are crucial for populations at the colonizing edge in range shifts induced by climate change. Experimental studies show taxonomically widespread plastic responses to global change drivers in many functional traits, though there is a lack of empirical support for many theoretical models on the evolution of phenotypic plasticity. Future studies should assess the adaptive value and evolutionary potential of plasticity under complex, realistic global change scenarios. Promising tools include resurrection protocols and artificial selection experiments.

  9. Plasticity as a developing trait: exploring the implications

    PubMed Central

    2015-01-01

    Individual differences in plasticity have been classically framed as genotype-by-environment interactions, with different genotypes showing different reaction norms in response to environmental conditions. However, research has shown that early experience can be a critical factor in shaping an individual's plasticity to later environmental factors. In other words, plasticity itself can be investigated as a developing trait that reflects the combined action of an individual's genes and previous interactions with the environment. In this paper I explore some implications of the idea that the early environment modulates long-term plasticity, with an emphasis on plasticity in behavioral traits. I begin by focusing on the mechanisms that mediate plasticity at the proximate level, and discussing the possibility that some traits may work as generalized mediators of plasticity by affecting the sensitivity of multiple phenol types across developmental contexts. I then tackle the complex problem of the evolution of reaction norms for plasticity. Next, I consider a number of potential implications for research on parental effects and phenotypic matching, and conclude by discussing how plasticity may become a target of evolutionary conflict between parents and offspring. In total, I aim to show how the idea of plasticity as a developing trait offers a rich source of questions and insights that may inform future research in this area. PMID:26816522

  10. Analysis of structures causing instabilities.

    PubMed

    Wilhelm, Thomas

    2007-07-01

    We present a simple new method to systematically identify all topological structures (e.g., positive feedback loops) potentially leading to locally unstable steady states: ICSA-The instability causing structure analysis. Systems without any instability causing structure (i.e., not fulfilling the necessary topological condition for instabilities) cannot have unstable steady states. It follows that common bistability or multistability and Hopf bifurcations are excluded and sustained oscillations and deterministic chaos are most unlikely. The ICSA leads to new insights into the topological organization of chemical and biochemical systems, such as metabolic, gene regulatory, and signal transduction networks.

  11. Simulations of Astrophysical fluid instabilities

    NASA Astrophysics Data System (ADS)

    Calder, A. C.; Fryxell, B.; Rosner, R.; Dursi, L. J.; Olson, K.; Ricker, P. M.; Timmes, F. X.; Zingale, M.; MacNeice, P.; Tufo, H. M.

    2001-10-01

    We present direct numerical simulations of mixing at Rayleigh-Taylor unstable interfaces performed with the FLASH code, developed at the ASCI/Alliances Center for Astrophysical Thermonuclear Flashes at the University of Chicago. We present initial results of single-mode studies in two and three dimensions. Our results indicate that three-dimensional instabilities grow significantly faster than two-dimensional instabilities and that grid resolution can have a significant effect on instability growth rates. We also find that unphysical diffusive mixing occurs at the fluid interface, particularly in poorly resolved simulations. .

  12. Instability of a bubble chain.

    PubMed

    Zhang, Wenjuan; An, Yu

    2013-05-01

    Based on the theory of shape instability and diffusive instability for single bubbles, we have studied the instability of an individual bubble in a bubble chain and found that its stable area enlarges the narrower the distance between bubbles. The spatial stability of the bubble chain is due to the secondary Bjerknes force between bubbles. Numerical calculations show the tension of the bubble chain varies with bubble distance and maxima appear at certain distances which could correspond to the stable states of the bubble chain.

  13. Phase Instability in Semiconductor Lasers

    NASA Astrophysics Data System (ADS)

    Gil, L.; Lippi, G. L.

    2014-11-01

    For many years, the apparent absence of a phase instability has characterized lasers as peculiar nonlinear oscillators. We show that this unusual feature is solely due to the approximations used in writing the standard models. A new, careful derivation of the fundamental equations, based on codimension 2 bifurcation theory, shows the possible existence of dynamical regimes displaying either a pure phase instability, or mixed phase-amplitude turbulence. A comparison to existing experimental results convincingly shows that the Benjamin-Feir instability, common to all nonlinear wave problems, is a fundamental, satisfactory interpretation for their deterministic multimode dynamics.

  14. Crack Instability Predictions Using a Multi-Term Approach

    NASA Technical Reports Server (NTRS)

    Zanganeh, Mohammad; Forman, Royce G.

    2015-01-01

    Present crack instability analysis for fracture critical flight hardware is normally performed using a single parameter, K(sub C), fracture toughness value obtained from standard ASTM 2D geometry test specimens made from the appropriate material. These specimens do not sufficiently match the boundary conditions and the elastic-plastic constraint characteristics of the hardware component, and also, the crack instability of most commonly used aircraft and aerospace structural materials have some amount of stable crack growth before fracture which makes the normal use of a K(sub C) single parameter toughness value highly approximate. In the past, extensive studies have been conducted to improve the single parameter (K or J controlled) approaches by introducing parameters accounting for the geometry or in-plane constraint effects. Using 'J-integral' and 'A' parameter as a measure of constraint is one of the most accurate elastic-plastic crack solutions currently available. In this work the feasibility of the J-A approach for prediction of the crack instability was investigated first by ignoring the effects of stable crack growth i.e. using a critical J and A and second by considering the effects of stable crack growth using the corrected J-delta a using the 'A' parameter. A broad range of initial crack lengths and a wide range of specimen geometries including C(T), M(T), ESE(T), SE(T), Double Edge Crack (DEC), Three-Hole-Tension (THT) and NC (crack from a notch) manufactured from Al7075 were studied. Improvements in crack instability predictions were observed compared to the other methods available in the literature.

  15. The Need for Plastics Education.

    ERIC Educational Resources Information Center

    Society of Plastics Engineers, Inc., Stamford, CT.

    In view of a lack of trained personnel in the industry, the Plastics Education Foundation proposes that educators (1) add more plastics programs, (2) establish plastics engineering degrees at appropriate 4-year institutions, (3) add plastics processing technology to current engineering curricula, and (4) interest younger students in courses and/or…

  16. The Need for Plastics Education.

    ERIC Educational Resources Information Center

    Society of Plastics Engineers, Inc., Stamford, CT.

    In view of a lack of trained personnel in the industry, the Plastics Education Foundation proposes that educators (1) add more plastics programs, (2) establish plastics engineering degrees at appropriate 4-year institutions, (3) add plastics processing technology to current engineering curricula, and (4) interest younger students in courses and/or…

  17. Chronic ankle instability.

    PubMed

    Gerstner Garces, Juan Bernardo

    2012-09-01

    Chronic instability of the ankle and anterolateral impingement syndrome are abnormalities that present as a result of inversion and forced plantar-flexion traumas of the foot, despite strict conservative management in the ER and in rehabilitation. A conservative approach is always the first choice of treatment, including anti-inflammatory medications, rehabilitation and proprioception, infiltration with steroids in impingement cases, and use of orthotics, whose true effectiveness is the subject of multiple studies and much debate. Good to excellent results can be obtained surgically with a minimally invasive approach, such as the arthroscopic technique presented herein. Such an approach is useful in managing a combination of conditions such as anterolateral impingement, synovitis, and osteochondral lesions of the talus. The method is easily reproducible, its learning curve is rapid, and it has the advantage of not preventing the use other arthroscopic methods, or open anatomic or nonanatomic methods (tendon transfers), in the case of failure. No nerve lesion was recorded, probably owing to the use of the security zone, and neither was there any arthrofibrosis, possibly related to the use of nonsteroidal anti-inflammatory medications in the immediate postsurgical period coupled with aggressive rehabilitation from the fourth week. The success of the technique is due to multidisciplinary team work leading to the ultimate achievement of patient satisfaction. This technique is not indicated for patients with a high sports demand or for sport professionals, until further biomechanical studies on its use and success are completed. Copyright © 2012 Elsevier Inc. All rights reserved.

  18. Resistive instabilities in tokamaks

    SciTech Connect

    Rutherford, P.H.

    1985-10-01

    Low-m tearing modes constitute the dominant instability problem in present-day tokamaks. In this lecture, the stability criteria for representative current profiles with q(0)-values slightly less than unit are reviewed; ''sawtooth'' reconnection to q(0)-values just at, or slightly exceeding, unity is generally destabilizing to the m = 2, n = 1 and m = 3, n = 2 modes, and severely limits the range of stable profile shapes. Feedback stabilization of m greater than or equal to 2 modes by rf heating or current drive, applied locally at the magnetic islands, appears feasible; feedback by island current drive is much more efficient, in terms of the radio-frequency power required, then feedback by island heating. Feedback stabilization of the m = 1 mode - although yielding particularly beneficial effects for resistive-tearing and high-beta stability by allowing q(0)-values substantially below unity - is more problematical, unless the m = 1 ideal-MHD mode can be made positively stable by strong triangular shaping of the central flux surfaces. Feedback techniques require a detectable, rotating MHD-like signal; the slowing of mode rotation - or the excitation of non-rotating modes - by an imperfectly conducting wall is also discussed.

  19. Instabilities of Charged Polyampholytes

    NASA Astrophysics Data System (ADS)

    Kardar, Mehran

    1996-03-01

    We consider polymers formed from a (quenched) random sequence of charged monomers of opposite signs. Such polymers, known as polyampholytes (PAs), are compact when completely neutral and expanded when highly charged.footnote Y. Kantor and M. Kardar, Europhys. Lett. 27, 643 (1994). We examine the transition between the two regimes by Monte Carlo simulations, exact enumeration studies, and by analogies to charged drops. We find that the overall excess charge, Q, is the main determinant of the size of the PA. A polymer composed of N charges of ± q0 is compact for Qinstability of a charged drop. A uniform excess charge causes the breakup of a fluid drop. We speculate that a uniformly charged polymer stretches out to a necklace shape. The inhomogeneities in charge distort the shape away from an ordered necklace.footnote Y. Kantor and M. Kardar, Phys. Rev. E 51, 1299 (1995).

  20. Instabilities in the aether

    SciTech Connect

    Carroll, Sean M.; Dulaney, Timothy R.; Gresham, Moira I.; Tam, Heywood

    2009-03-15

    We investigate the stability of theories in which Lorentz invariance is spontaneously broken by fixed-norm vector 'aether' fields. Models with generic kinetic terms are plagued either by ghosts or by tachyons, and are therefore physically unacceptable. There are precisely three kinetic terms that are not manifestly unstable: a sigma model ({partial_derivative}{sub {mu}}A{sub {nu}}){sup 2}, the Maxwell Lagrangian F{sub {mu}}{sub {nu}}F{sup {mu}}{sup {nu}}, and a scalar Lagrangian ({partial_derivative}{sub {mu}}A{sup {mu}}){sup 2}. The timelike sigma-model case is well defined and stable when the vector norm is fixed by a constraint; however, when it is determined by minimizing a potential there is necessarily a tachyonic ghost, and therefore an instability. In the Maxwell and scalar cases, the Hamiltonian is unbounded below, but at the level of perturbation theory there are fewer degrees of freedom and the models are stable. However, in these two theories there are obstacles to smooth evolution for certain choices of initial data.

  1. Filamentation instability in two counter-streaming laser plasmas

    NASA Astrophysics Data System (ADS)

    Liu, Hui; Dong, Quan-Li; Yuan, Da-Wei; Liu, Xun; Hua, Neng; Qiao, Zhan-Feng; Zhu, Bao-Qiang; Zhu, Jian-Qiang; Jiang, Bo-Bin; Du, Kai; Tang, Yong-Jian; Zhao, Gang; Yuan, Xiao-Hui; Sheng, Zheng-Ming; Zhang, Jie

    2016-12-01

    The filamentation instability was observed in the interaction of two counter-streaming laser ablated plasma flows, which were supersonic, collisionless, and also closely relevant to astrophysical conditions. The plasma flows were created by irradiating a pair of oppositely standing plastic (CH) foils with 1ns-pulsed laser beams of total energy of 1.7 kJ in two laser spots. With characteristics diagnosed in experiments, the calculated features of Weibel-type filaments are in good agreement with measurements. Project supported by the National Natural Science Foundation of China (Grant Nos. 11074297, 11674146, and 11220101002) and the National Basic Research Program of China (Grant No. 2013CBA01500.

  2. Drinking-Straw Microbalance and Seesaw: Stability and Instability

    NASA Astrophysics Data System (ADS)

    Chapman, Peter; Glasser, Leslie

    2015-03-01

    The mechanics of a beam balance are little appreciated and seldom understood. We here consider the conditions that result in a stable balance, with center of gravity below the fulcrum (pivot point), while an unstable balance results when the center of gravity is above the fulcrum. The highly sensitive drinking-straw microbalance, which uses a plastic drinking straw as a rigid beam, is briefly described with some slight convenient modifications. Different placements of the center of gravity are considered analytically to explain the equilibrium neutrality, stability, and instability of such beam balances as the microbalance, the playground "seesaw" or "teeter-totter," the "dipping bird," and other toys and magic tricks.

  3. Plastic Deformation Modes of CuZr/Cu Multilayers

    PubMed Central

    Cui, Yan; Abad, Oscar Torrents; Wang, Fei; Huang, Ping; Lu, Tian-Jian; Xu, Ke-Wei; Wang, Jian

    2016-01-01

    We synthesized CuZr/Cu multilayers and performed nanoindentation testing to explore the dependence of plastic deformation modes on the thickness of CuZr layers. The Cu layers were 18 nm thick and the CuZr layers varied in thickness from 4 nm to 100 nm. We observed continuous plastic co-deformation in the 4 nm and 10 nm CuZr − 18 nm Cu multilayers and plastic-induced shear instability in thick CuZr layers (>20 nm). The plastic co-deformation is ascribed to the nucleation and interaction of shear transformation zones in CuZr layers at the adjacent interfaces, while the shear instability is associated with the nucleation and propagation of shear bands in CuZr layers. Shear bands are initialized in the CuZr layers due to the accumulated glide dislocations along CuZr-Cu interfaces, and propagate into adjacent Cu layers via slips on {111} plane non-parallel to the interface. Due to crystallographic constraint of the Cu layers, shear bands are approximately parallel to {111} plane in the Cu layer. PMID:26984537

  4. Hydrodynamic instabilities in beryllium targets for the National Ignition Facility

    SciTech Connect

    Yi, S. A. Simakov, A. N.; Wilson, D. C.; Olson, R. E.; Kline, J. L.; Batha, S. H.; Clark, D. S.; Hammel, B. A.; Milovich, J. L.; Salmonson, J. D.; Kozioziemski, B. J.

    2014-09-15

    Beryllium ablators offer higher ablation velocity, rate, and pressure than their carbon-based counterparts, with the potential to increase the probability of achieving ignition at the National Ignition Facility (NIF) [E. I. Moses et al., Phys. Plasmas 16, 041006 (2009)]. We present here a detailed hydrodynamic stability analysis of low (NIF Revision 6.1) and high adiabat NIF beryllium target designs. Our targets are optimized to fully utilize the advantages of beryllium in order to suppress the growth of hydrodynamic instabilities. This results in an implosion that resists breakup of the capsule, and simultaneously minimizes the amount of ablator material mixed into the fuel. We quantify the improvement in stability of beryllium targets relative to plastic ones, and show that a low adiabat beryllium capsule can be at least as stable at the ablation front as a high adiabat plastic target.

  5. Conservation laws in baroclinic inertial-symmetric instabilities

    NASA Astrophysics Data System (ADS)

    Grisouard, Nicolas; Fox, Morgan B.; Nijjer, Japinder

    2017-04-01

    Submesoscale oceanic density fronts are structures in geostrophic and hydrostatic balance, but are more prone to instabilities than mesoscale flows. As a consequence, they are believed to play a large role in air-sea exchanges, near-surface turbulence and dissipation of kinetic energy of geostrophically and hydrostatically balanced flows. We will present two-dimensional (x, z) Boussinesq numerical experiments of submesoscale baroclinic fronts on the f-plane. Instabilities of the mixed inertial and symmetric types (the actual name varies across the literature) develop, with the absence of along-front variations prohibiting geostrophic baroclinic instabilities. Two new salient facts emerge. First, contrary to pure inertial and/or pure symmetric instability, the potential energy budget is affected, the mixed instability extracting significant available potential energy from the front and dissipating it locally. Second, in the submesoscale regime, the growth rate of this mixed instability is sufficiently large that significant radiation of near-inertial internal waves occurs. Although energetically small compared to e.g. local dissipation within the front, this process might be a significant source of near-inertial energy in the ocean.

  6. Gravitational instability of rotating magnetized quantum anisotropic plasma

    NASA Astrophysics Data System (ADS)

    Argal, Shraddha; Tiwari, Anita; Prajapati, R. P.; Sharma, P. K.

    2017-04-01

    The present problem deals with the study of gravitational (Jeans) instability of magnetized, rotating, anisotropic plasmas considering quantum effects. The basic equations of the considered system are constructed using combined Chew-Goldberger-Low (CGL) fluid model and quantum magnetohydrodynamic (QMHD) fluid model. A dispersion relation is obtained using the normal mode technique which is discussed for transverse and longitudinal modes of propagation. It is found that a rotating quantum plasma influences the gravitational mode in transverse propagation but not in longitudinal propagation. The presence of rotation decreases the critical wavenumber and it has a stabilizing effect on the Jeans instability criterion of magnetized quantum plasma in transverse propagation. The firehose instability is unaffected due to the presence of uniform rotation and quantum corrections. We observe from the numerical analysis that region of instability and critical Jeans wavenumber are both decreased due to the presence of uniform rotation. The stabilizing influence of uniform rotation is observed for magnetized, rotating, anisotropic plasmas in the presence of quantum correction. In the case of a longitudinal mode of propagation we found the Jeans instability criterion is not affected by rotation. The quantum diffraction term has a stabilizing effect on the growth rate of the Jeans instability when the wave propagates along the direction of the magnetic field.

  7. Evaporative instabilities in climbing films

    NASA Astrophysics Data System (ADS)

    Hosoi, A. E.; Bush, John W. M.

    2001-09-01

    We consider flow in a thin film generated by partially submerging an inclined rigid plate in a reservoir of ethanol or methanol water solution and wetting its surface. Evaporation leads to concentration and surface tension gradients that drive flow up the plate. An experimental study indicates that the climbing film is subject to two distinct instabilities. The first is a convective instability characterized by flattened convection rolls aligned in the direction of flow and accompanied by free-surface deformations; in the meniscus region, this instability gives rise to pronounced ridge structures aligned with the mean flow. The second instability, evident when the plate is nearly vertical, takes the form of transverse surface waves propagating up the plate.

  8. Clustering instability of focused swimmers

    NASA Astrophysics Data System (ADS)

    Lauga, Eric; Nadal, Francois

    2016-12-01

    One of the hallmarks of active matter is its rich nonlinear dynamics and instabilities. Recent numerical simulations of phototactic algae showed that a thin jet of swimmers, obtained from hydrodynamic focusing inside a Poiseuille flow, was unstable to longitudinal perturbations with swimmers dynamically clustering (Jibuti L. et al., Phys. Rev. E, 90, (2014) 063019). As a simple starting point to understand these instabilities, we consider in this paper an initially homogeneous one-dimensional line of aligned swimmers moving along the same direction, and characterise its instability using both a continuum framework and a discrete approach. In both cases, we show that hydrodynamic interactions between the swimmers lead to instabilities in density for which we compute the growth rate analytically. Lines of pusher-type swimmers are predicted to remain stable while lines of pullers (such as flagellated algae) are predicted to always be unstable.

  9. 77 FR 54930 - Carlyle Plastics and Resins, Formerly Known as Fortis Plastics, A Subsidiary of Plastics...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-09-06

    ... Employment and Training Administration Carlyle Plastics and Resins, Formerly Known as Fortis Plastics, A Subsidiary of Plastics Acquisitions Inc., Including On-Site Leased Workers From Kelly Services and Shelley... Adjustment Assistance on July 3, 2012, applicable to workers and former workers of workers of Fortis Plastics...

  10. Origins of Folding Instabilities on Polycrystalline Metal Surfaces

    NASA Astrophysics Data System (ADS)

    Beckmann, N.; Romero, P. A.; Linsler, D.; Dienwiebel, M.; Stolz, U.; Moseler, M.; Gumbsch, P.

    2014-12-01

    Wear and removal of material from polycrystalline metal surfaces is inherently connected to plastic flow. Here, plowing-induced unconstrained surface plastic flow on a nanocrystalline copper surface has been studied by massive molecular dynamics simulations and atomic force microscopy scratch experiments. In agreement with experimental findings, bulges in front of a model asperity develop into vortexlike fold patterns that mark the disruption of laminar flow. We identify dislocation-mediated plastic flow in grains with suitably oriented slip systems as the basic mechanism of bulging and fold formation. The observed folding can be fundamentally explained by the inhomogeneity of plasticity on polycrystalline surfaces which favors bulge formation on grains with suitably oriented slip system. This process is clearly distinct from Kelvin-Helmholtz instabilities in fluids, which have been previously suggested to resemble the formed surface fold patterns. The generated prow grows into a rough chip with stratified lamellae that are identified as the precursors of wear debris. Our findings demonstrate the importance of surface texture and grain structure engineering to achieve ultralow wear in metals.

  11. Instability following total knee arthroplasty.

    PubMed

    Rodriguez-Merchan, E Carlos

    2011-10-01

    Background Knee prosthesis instability (KPI) is a frequent cause of failure of total knee arthroplasty. Moreover, the degree of constraint required to achieve immediate and long-term stability in total knee arthroplasty (TKA) is frequently debated. Questions This review aims to define the problem, analyze risk factors, and review strategies for prevention and treatment of KPI. Methods A PubMed (MEDLINE) search of the years 2000 to 2010 was performed using two key words: TKA and instability. One hundred and sixty-five initial articles were identified. The most important (17) articles as judged by the author were selected for this review. The main criteria for selection were that the articles addressed and provided solutions to the diagnosis and treatment of KPI. Results Patient-related risk factors predisposing to post-operative instability include deformity requiring a large surgical correction and aggressive ligament release, general or regional neuromuscular pathology, and hip or foot deformities. KPI can be prevented in most cases with appropriate selection of implants and good surgical technique. When ligament instability is anticipated post-operatively, the need for implants with a greater degree of constraint should be anticipated. In patients without significant varus or valgus malalignment and without significant flexion contracture, the posterior cruciate ligament (PCL) can be retained. However, the PCL should be sacrificed when deformity exists particularly in patients with rheumatoid arthritis, previous patellectomy, previous high tibial osteotomy or distal femoral osteotomy, and posttraumatic osteoarthritis with disruption of the PCL. In most cases, KPI requires revision surgery. Successful outcomes can only be obtained if the cause of KPI is identified and addressed. Conclusions Instability following TKA is a common cause of the need for revision. Typically, knees with deformity, rheumatoid arthritis, previous patellectomy or high tibial osteotomy, and

  12. Aerodynamic instability: A case history

    NASA Technical Reports Server (NTRS)

    Eisenmann, R. C.

    1985-01-01

    The identification, diagnosis, and final correction of complex machinery malfunctions typically require the correlation of many parameters such as mechanical construction, process influence, maintenance history, and vibration response characteristics. The progression is reviewed of field testing, diagnosis, and final correction of a specific machinery instability problem. The case history presented addresses a unique low frequency instability problem on a high pressure barrel compressor. The malfunction was eventually diagnosed as a fluidic mechanism that manifested as an aerodynamic disturbance to the rotor assembly.

  13. Magnetothermal instability in cooling flows

    NASA Technical Reports Server (NTRS)

    Loewenstein, Michael

    1990-01-01

    The effect of magnetic fields on thermal instability in cooling flows is investigated using linear, Eulerian perturbation analysis. As contrasted with the zero magnetic-field case, hydromagnetic stresses support perturbations against acceleration caused by buoyancy - comoving evolution results and global growth rates are straightforward to obtain for a given cooling flow entropy distribution. In addition, background and induced magnetic fields ensure that conductive damping of thermal instability is greatly reduced.

  14. Waves and instabilities in plasmas

    SciTech Connect

    Chen, L.

    1987-01-01

    The contents of this book are: Plasma as a Dielectric Medium; Nyquist Technique; Absolute and Convective Instabilities; Landau Damping and Phase Mixing; Particle Trapping and Breakdown of Linear Theory; Solution of Viasov Equation via Guilding-Center Transformation; Kinetic Theory of Magnetohydrodynamic Waves; Geometric Optics; Wave-Kinetic Equation; Cutoff and Resonance; Resonant Absorption; Mode Conversion; Gyrokinetic Equation; Drift Waves; Quasi-Linear Theory; Ponderomotive Force; Parametric Instabilities; Problem Sets for Homework, Midterm and Final Examinations.

  15. Magnetothermal instability in cooling flows

    NASA Technical Reports Server (NTRS)

    Loewenstein, Michael

    1990-01-01

    The effect of magnetic fields on thermal instability in cooling flows is investigated using linear, Eulerian perturbation analysis. As contrasted with the zero magnetic-field case, hydromagnetic stresses support perturbations against acceleration caused by buoyancy - comoving evolution results and global growth rates are straightforward to obtain for a given cooling flow entropy distribution. In addition, background and induced magnetic fields ensure that conductive damping of thermal instability is greatly reduced.

  16. Material Instabilities in Particulate Systems

    NASA Technical Reports Server (NTRS)

    Goddard, J. D.

    1999-01-01

    Following is a brief summary of a theoretical investigation of material (or constitutive) instability associated with shear induced particle migration in dense particulate suspensions or granular media. It is shown that one can obtain a fairly general linear-stability analysis, including the effects of shear-induced anisotropy in the base flow as well as Reynolds dilatancy. A criterion is presented here for simple shearing instability in the absence of inertia and dilatancy.

  17. Numerical methods for large eddy simulation of acoustic combustion instabilities

    NASA Astrophysics Data System (ADS)

    Wall, Clifton T.

    Acoustic combustion instabilities occur when interaction between the combustion process and acoustic modes in a combustor results in periodic oscillations in pressure, velocity, and heat release. If sufficiently large in amplitude, these instabilities can cause operational difficulties or the failure of combustor hardware. In many situations, the dominant instability is the result of the interaction between a low frequency acoustic mode of the combustor and the large scale hydrodynamics. Large eddy simulation (LES), therefore, is a promising tool for the prediction of these instabilities, since both the low frequency acoustic modes and the large scale hydrodynamics are well resolved in LES. Problems with the tractability of such simulations arise, however, due to the difficulty of solving the compressible Navier-Stokes equations efficiently at low Mach number and due to the large number of acoustic periods that are often required for such instabilities to reach limit cycles. An implicit numerical method for the solution of the compressible Navier-Stokes equations has been developed which avoids the acoustic CFL restriction, allowing for significant efficiency gains at low Mach number, while still resolving the low frequency acoustic modes of interest. In the limit of a uniform grid the numerical method causes no artificial damping of acoustic waves. New, non-reflecting boundary conditions have also been developed for use with the characteristic-based approach of Poinsot and Lele (1992). The new boundary conditions are implemented in a manner which allows for significant reduction of the computational domain of an LES by eliminating the need to perform LES in regions where one-dimensional acoustics significantly affect the instability but details of the hydrodynamics do not. These new numerical techniques have been demonstrated in an LES of an experimental combustor. The new techniques are shown to be an efficient means of performing LES of acoustic combustion

  18. Instability of enclosed horizons

    NASA Astrophysics Data System (ADS)

    Kay, Bernard S.

    2015-03-01

    We point out that there are solutions to the scalar wave equation on dimensional Minkowski space with finite energy tails which, if they reflect off a uniformly accelerated mirror due to (say) Dirichlet boundary conditions on it, develop an infinite stress-energy tensor on the mirror's Rindler horizon. We also show that, in the presence of an image mirror in the opposite Rindler wedge, suitable compactly supported arbitrarily small initial data on a suitable initial surface will develop an arbitrarily large stress-energy scalar near where the two horizons cross. Also, while there is a regular Hartle-Hawking-Israel-like state for the quantum theory between these two mirrors, there are coherent states built on it for which there are similar singularities in the expectation value of the renormalized stress-energy tensor. We conjecture that in other situations with analogous enclosed horizons such as a (maximally extended) Schwarzschild black hole in equilibrium in a (stationary spherical) box or the (maximally extended) Schwarzschild-AdS spacetime, there will be similar stress-energy singularities and almost-singularities—leading to instability of the horizons when gravity is switched on and matter and gravity perturbations are allowed for. All this suggests it is incorrect to picture a black hole in equilibrium in a box or a Schwarzschild-AdS black hole as extending beyond the past and future horizons of a single Schwarzschild (/Schwarzschild-AdS) wedge. It would thus provide new evidence for 't Hooft's brick wall model while seeming to invalidate the picture in Maldacena's ` Eternal black holes in AdS'. It would thereby also support the validity of the author's matter-gravity entanglement hypothesis and of the paper ` Brick walls and AdS/CFT' by the author and Ortíz.

  19. Replicated evolution of integrated plastic responses during early adaptive divergence.

    PubMed

    Parsons, Kevin J; Robinson, Beren W

    2006-04-01

    Colonization of a novel environment is expected to result in adaptive divergence from the ancestral population when selection favors a new phenotypic optimum. Local adaptation in the new environment occurs through the accumulation and integration of character states that positively affect fitness. The role played by plastic traits in adaptation to a novel environment has generally been ignored, except for variable environments. We propose that if conditions in a relatively stable but novel environment induce phenotypically plastic responses in many traits, and if genetic variation exists in the form of those responses, then selection may initially favor the accumulation and integration of functionally useful plastic responses. Early divergence between ancestral and colonist forms will then occur with respect to their plastic responses across the gradient bounded by ancestral and novel environmental conditions. To test this, we compared the magnitude, integration, and pattern of plastic character responses in external body form induced by shallow versus open water conditions between two sunfish ecomorphs that coexist in four postglacial lakes. The novel sunfish ecomorph is present in the deeper open water habitat, whereas the ancestral ecomorph inhabits the shallow waters along the lake margin. Plastic responses by open water ecomorphs were more correlated than those of their local shallow water ecomorph in two of the populations, whereas equal levels of correlated plastic character responses occurred between ecomorphs in the other two populations. Small but persistent differences occurred between ecomorph pairs in the pattern of their character responses, suggesting a recent divergence. Open water ecomorphs shared some similarities in the covariance among plastic responses to rearing environment. Replication in the form of correlated plastic responses among populations of open water ecomorphs suggests that plastic character states may evolve under selection

  20. History of shoulder instability surgery.

    PubMed

    Randelli, Pietro; Cucchi, Davide; Butt, Usman

    2016-02-01

    The surgical management of shoulder instability is an expanding and increasingly complex area of study within orthopaedics. This article describes the history and evolution of shoulder instability surgery, examining the development of its key principles, the currently accepted concepts and available surgical interventions. A comprehensive review of the available literature was performed using PubMed. The reference lists of reviewed articles were also scrutinised to ensure relevant information was included. The various types of shoulder instability including anterior, posterior and multidirectional instability are discussed, focussing on the history of surgical management of these topics, the current concepts and the results of available surgical interventions. The last century has seen important advancements in the understanding and treatment of shoulder instability. The transition from open to arthroscopic surgery has allowed the discovery of previously unrecognised pathologic entities and facilitated techniques to treat these. Nevertheless, open surgery still produces comparable results in the treatment of many instability-related conditions and is often required in complex or revision cases, particularly in the presence of bone loss. More high-quality research is required to better understand and characterise this spectrum of conditions so that successful evidence-based management algorithms can be developed. IV.

  1. Vertical Instability at IPNS RCS.

    SciTech Connect

    Wang, S.; Brumwell, F. R.; Dooling, J. C.; Harkay, K. C.; Kustom, R.; McMichael, G. E.; Middendorf, M. E.; Nassiri, A.; Accelerator Systems Division

    2008-01-01

    The rapid cycling synchrotron (RCS) of the intense pulsed neutron source (IPNS) at ANL accelerates > 3.0 times 10{sup 12} protons from 50 MeV to 450 MeV with 30-Hz repetition frequency. During the acceleration cycle, the rf frequency varies from 2.21 MHz to 5.14 MHz. Presently, the beam current is limited by a vertical instability. By analyzing turn-by-turn beam position monitor (BPM) data, large- amplitude mode 0 and mode 1 vertical beam centroid oscillations were observed in the later part of the acceleration cycle. The oscillations start in the tail of the bunch, build up, and remain localized in the tail half of the bunch. This vertical instability was compared with a head-tail instability that was intentionally induced in the RCS by adjusting the trim sextupoles. It appears that our vertical instability is not a classical head-tail instability [1]. More data analysis and experiments were performed to characterize the instability.

  2. Vector-Resonance-Multimode Instability

    NASA Astrophysics Data System (ADS)

    Sergeyev, S. V.; Kbashi, H.; Tarasov, N.; Loiko, Yu.; Kolpakov, S. A.

    2017-01-01

    The modulation and multimode instabilities are the main mechanisms which drive spontaneous spatial and temporal pattern formation in a vast number of nonlinear systems ranging from biology to laser physics. Using an Er-doped fiber laser as a test bed, here for the first time we demonstrate both experimentally and theoretically a new type of a low-threshold vector-resonance-multimode instability which inherits features of multimode and modulation instabilities. The same as for the multimode instability, a large number of longitudinal modes can be excited without mode synchronization. To enable modulation instability, we modulate the state of polarization of the lasing signal with the period of the beat length by an adjustment of the in-cavity birefringence and the state of polarization of the pump wave. As a result, we show the regime's tunability from complex oscillatory to periodic with longitudinal mode synchronization in the case of resonance matching between the beat and cavity lengths. Apart from the interest in laser physics for unlocking the tunability and stability of dynamic regimes, the proposed mechanism of the vector-resonance-multimode instability can be of fundamental interest for the nonlinear dynamics of various distributed systems.

  3. Compressibility effect on magnetic-shear-localized ideal magnetohydrodynamic interchange instability

    SciTech Connect

    Gupta, Sangeeta; Callen, J.D.; Hegna, C.C.

    2005-08-15

    Eigenmode analysis of a magnetic-shear-localized ideal magnetohydrodynamic interchange instability in the presence of plasma compressibility indicates the marginal stability criterion (D{sub I}=1/4) is not affected by the compressibility effects. Above the marginal stability criterion, plasma compressibility causes a significant reduction in the growth rate of an ideal interchange instability.

  4. A model for self-treatment of four sub-types of symptomatic 'depression' using non-prescription agents: neuroticism (anxiety and emotional instability); malaise (fatigue and painful symptoms); demotivation (anhedonia) and seasonal affective disorder 'SAD'.

    PubMed

    Charlton, Bruce G

    2009-01-01

    This article will present a model for how 'depression' (i.e. depressive symptoms) can be divided into four self-diagnosed sub-types or causes which might then be self-treated using agents available without prescription. (Another, much rarer, cause of depressed symptoms is the classical illness of 'melancholia', which when severe cannot be self-treated and typically requires hospitalization.) A self-management option and alternative is now needed due to the an inappropriate emphasis of modern psychiatry on treatment of imprecise syndromal 'disorders' which may entail treating 'depression' at the cost of making the patient feel and function worse. By contrast, the basic theoretical stance of self-management is that depressed mood should be seen as a result of unpleasant symptoms - and it is the symptoms that require treatment, not the mood itself. Furthermore, drugs (or other interventions) need to be classified in terms of their potential therapeutic effects on these symptoms that may cause depressed mood. The four common causes of depressed mood considered here are the personality trait of Neuroticism; the state of malaise (fatigue, aching etc) which accompanies an illness with an activated immune system; demotivation due to lack of positive emotions (anhedonia); and the syndrome of seasonal affective disorder (SAD). Each of the four sub-types is then 'matched' with a first-line non-prescription agent. The 'stabilizing' agents such as St John's Wort and the antihistamines chlorpheniramine and diphenhydramine are used for treatment of Neuroticism; analgesics/pain killers such as aspirin, ibuprofen, paracetamol/acetaminophen and the opiates are used to treat malaise; energizing agents such as caffeine and nicotine are used for the treatment of demotivation; and bright light used in the early morning to treat SAD. Self-treatments are intended to be used after research and experimentally, on a trial-and-error basis; with self-monitoring of beneficial and harmful

  5. Exercise and cerebrovascular plasticity.

    PubMed

    Nishijima, T; Torres-Aleman, I; Soya, H

    2016-01-01

    Aging impairs cerebrovascular plasticity and subsequently leads cerebral hypoperfusion, which synergistically accelerates aging-associated cognitive dysfunction and neurodegenerative diseases associated with impaired neuronal plasticity. On the other hand, over two decades of researches have successfully demonstrated that exercise, or higher level of physical activity, is a powerful and nonpharmacological approach to improve brain function. Most of the studies have focused on the neuronal aspects and found that exercise triggers improvements in neuronal plasticity, such as neurogenesis; however, exercise can improve cerebrovascular plasticity as well. In this chapter, to understand these beneficial effects of exercise on the cerebral vasculature, we first discuss the issue of changes in cerebral blood flow and its regulation during acute bouts of exercise. Then, how regular exercise improves cerebrovascular plasticity will be discussed. In addition, to shed light on the importance of understanding interactions between the neuron and cerebral vasculature, we describe neuronal activity-driven uptake of circulating IGF-I into the brain. © 2016 Elsevier B.V. All rights reserved.

  6. The plasticity of clays

    USGS Publications Warehouse

    Group, F.F.

    1905-01-01

    (1) Sand injures plasticity little at first because the grains are suspended in a plastic mass. It is only when grains are abundant enough to come in contact with their neighbors, that the effect becomes serious, and then both strength and amount of possible flow are injured. (2) Certain rare organic colloids increase the plasticity by rendering the water viscous. (3) Fineness also tends to increase plasticity. (4) Plane surfaces (plates) increase the amount of possible flow. They also give a chance for lubrication by thinner films, thus increasing the friction of film, and the strength of the whole mass. The action of plates is thus twofold ; but fineness may be carried to such an extent as to break up plate-like grains into angular fragments. The beneficial effects of plates are also decreased by the fact that each is so closely surrounded by others in the mass. (5) Molecular attraction is twofold in increasing plasticity. As the attraction increases, the coherence and strength of the mass increase, and the amount of possible deformation before crumbling also increases. Fineness increases this action by requiring more water. Colloids and crystalloids in solution may also increase the attraction. It is thus seen to be more active than any other single factor.

  7. Epilepsy as an Example of Neural Plasticity

    PubMed Central

    Scharfman, Helen E.

    2008-01-01

    Epilepsy is a devastating disease affecting more than 1% of the population. Yet, if one considers the neurobiological substrates of this disease, what is revealed is an array of phenomenon that exemplify the remarkable capacity for the brain to change its basic structure and function, that is, neural plasticity. Some of these alterations are transient and merely impressive for their extent, or for their robust nature across animal models and human epilepsy. Others are notable for their persistence, often enduring for months or years. As an example, the dentate gyrus, and specifically the principal cell of the dentate gyrus, the granule cell, is highlighted. This area of the brain and this particular cell type, for reasons that are currently unclear, hold an uncanny capacity to change after seizures. For those interested in plasticity, it is suggested that perhaps the best examples for study of plasticity lie in the field of epilepsy. PMID:11954560

  8. Developmental plasticity and the origin of tetrapods.

    PubMed

    Standen, Emily M; Du, Trina Y; Larsson, Hans C E

    2014-09-04

    The origin of tetrapods from their fish antecedents, approximately 400 million years ago, was coupled with the origin of terrestrial locomotion and the evolution of supporting limbs. Polypterus is a member of the basal-most group of ray-finned fish (actinopterygians) and has many plesiomorphic morphologies that are comparable to elpistostegid fishes, which are stem tetrapods. Polypterus therefore serves as an extant analogue of stem tetrapods, allowing us to examine how developmental plasticity affects the 'terrestrialization' of fish. We measured the developmental plasticity of anatomical and biomechanical responses in Polypterus reared on land. Here we show the remarkable correspondence between the environmentally induced phenotypes of terrestrialized Polypterus and the ancient anatomical changes in stem tetrapods, and we provide insight into stem tetrapod behavioural evolution. Our results raise the possibility that environmentally induced developmental plasticity facilitated the origin of the terrestrial traits that led to tetrapods.

  9. Scalar instabilities in bimetric gravity: the Vainshtein mechanism and structure formation

    SciTech Connect

    Mörtsell, E.; Enander, J. E-mail: enander@fysik.su.se

    2015-10-01

    We investigate the observational consequences of scalar instabilities in bimetric theory, under the assumption that the Vainshtein mechanism restores general relativity within a certain distance from gravitational sources. We argue that early time instabilities have a negligible impact on observed structures. Assuming that the instabilities affect sub-horizon density fluctuations, we constrain the redshift, z{sub i}, below which instabilities are ruled out. For the ''minimal'' β{sub 1}-model, observational constraints are close to the theoretical expectations of z{sub i≈} 0.5, potentially allowing the model to be ruled in or out with a more detailed study, possibly including secondary cosmic microwave background constraints.

  10. Hidden instabilities in the Ti:sapphire Kerr lens mode-locked laser.

    PubMed

    Kovalsky, M G; Hnilo, A A; González Inchauspe, C M

    1999-11-15

    It is experimentally shown that pulse-to-pulse instabilities in the output of Kerr lens mode-locked Ti:sapphire lasers are usual and that they can affect some of the pulse variables (e.g., the spot size) and not others (e.g., pulse duration and energy). These instabilities are not detectable in the averaged signals (such as the autocorrelation of the pulse) that are customarily used for controlling the laser. But, if they are present but are disregarded, these instabilities have undesirable consequences in almost any application. A simple way to detect and eliminate the instabilities is described.

  11. Understanding Etna flank instability through numerical models

    NASA Astrophysics Data System (ADS)

    Apuani, Tiziana; Corazzato, Claudia; Merri, Andrea; Tibaldi, Alessandro

    2013-02-01

    mainly devoted to evaluate the effect of topography, geometry and rheological behaviour of the structural units. The 3D numerical model, extended 40 × 60 km, was implemented to simulate the volcano deformation pattern. First, the role of the Pleistocene subetnean clays was investigated, then, two "structural weakness zones" - the Pernicana Fault system and the NE rift - were introduced and their effects on the flank instability evaluated. Two extreme hydrogeological conditions, drained and undrained, were analysed. The results are expressed in terms of stress-strain field, displacement pattern, plasticity states and shear strain increments. Two main instability mechanisms were identified: one at shallow depth, with the sliding surface located inside the subetnean Quaternary clay, and another deep-seated mechanism with a not continuous and less evident sliding surface, developed inside the Apennine-Maghrebian Chain flysch, bordered by active structures. Both mechanisms contribute to explain the present deformation pattern and some of the main structures of the Etna flank. The effect of magma pressure exerted on the active dyke walls during eruptions was then simulated and relations between magmatic activity and flank instability were preliminarily investigated.

  12. Consumer hazards of plastics.

    PubMed Central

    Wiberg, G S

    1976-01-01

    The modern consumer is exposed to a wide variety of plastic and rubber products in his day to day life: at home, work, school, shopping, recreation and play, and transport. A large variety of toxic sequellae have resulted from untoward exposures by many different routes: oral, dermal, inhalation, and parenteral. Toxic change may result from the plastic itself, migration of unbound components and additives, chemical decomposition or toxic pyrolysis products. The type of damage may involve acute poisoning, chronic organ damage, reproductive disorders, and carcinogenic, mutagenic and teratogenic episodes. Typical examples for all routes are cited along with the activites of Canadian regulatory agencies to reduce both the incidence and severity of plastic-induced disease. PMID:1026409

  13. Libration-driven multipolar instabilities

    NASA Astrophysics Data System (ADS)

    Cébron, D.; Vantieghem, S.; Herreman, W.

    2014-01-01

    We consider rotating flows in non-axisymmetric enclosures that are driven by libration, i.e. by a small periodic modulation of the rotation rate. Thanks to its simplicity, this model is relevant to various contexts, from industrial containers (with small oscillations of the rotation rate) to fluid layers of terrestial planets (with length-of-day variations). Assuming a multipolar $n$-fold boundary deformation, we first obtain the two-dimensional basic flow. We then perform a short-wavelength local stability analysis of the basic flow, showing that an instability may occur in three dimensions. We christen it the Libration Driven Multipolar Instability (LDMI). The growth rates of the LDMI are computed by a Floquet analysis in a systematic way, and compared to analytical expressions obtained by perturbation methods. We then focus on the simplest geometry allowing the LDMI, a librating deformed cylinder. To take into account viscous and confinement effects, we perform a global stability analysis, which shows that the LDMI results from a parametric resonance of inertial modes. Performing numerical simulations of this librating cylinder, we confirm that the basic flow is indeed established and report the first numerical evidence of the LDMI. Numerical results, in excellent agreement with the stability results, are used to explore the non-linear regime of the instability (amplitude and viscous dissipation of the driven flow). We finally provide an example of LDMI in a deformed spherical container to show that the instability mechanism is generic. Our results show that the previously studied libration driven elliptical instability simply corresponds to the particular case $n=2$ of a wider class of instabilities. Summarizing, this work shows that any oscillating non-axisymmetric container in rotation may excite intermittent, space-filling LDMI flows, and this instability should thus be easy to observe experimentally.

  14. The Role of Neuromodulators in Cortical Plasticity. A Computational Perspective

    PubMed Central

    Pedrosa, Victor; Clopath, Claudia

    2017-01-01

    Neuromodulators play a ubiquitous role across the brain in regulating plasticity. With recent advances in experimental techniques, it is possible to study the effects of diverse neuromodulatory states in specific brain regions. Neuromodulators are thought to impact plasticity predominantly through two mechanisms: the gating of plasticity and the upregulation of neuronal activity. However, the consequences of these mechanisms are poorly understood and there is a need for both experimental and theoretical exploration. Here we illustrate how neuromodulatory state affects cortical plasticity through these two mechanisms. First, we explore the ability of neuromodulators to gate plasticity by reshaping the learning window for spike-timing-dependent plasticity. Using a simple computational model, we implement four different learning rules and demonstrate their effects on receptive field plasticity. We then compare the neuromodulatory effects of upregulating learning rate versus the effects of upregulating neuronal activity. We find that these seemingly similar mechanisms do not yield the same outcome: upregulating neuronal activity can lead to either a broadening or a sharpening of receptive field tuning, whereas upregulating learning rate only intensifies the sharpening of receptive field tuning. This simple model demonstrates the need for further exploration of the rich landscape of neuromodulator-mediated plasticity. Future experiments, coupled with biologically detailed computational models, will elucidate the diversity of mechanisms by which neuromodulatory state regulates cortical plasticity. PMID:28119596

  15. The Role of Neuromodulators in Cortical Plasticity. A Computational Perspective.

    PubMed

    Pedrosa, Victor; Clopath, Claudia

    2016-01-01

    Neuromodulators play a ubiquitous role across the brain in regulating plasticity. With recent advances in experimental techniques, it is possible to study the effects of diverse neuromodulatory states in specific brain regions. Neuromodulators are thought to impact plasticity predominantly through two mechanisms: the gating of plasticity and the upregulation of neuronal activity. However, the consequences of these mechanisms are poorly understood and there is a need for both experimental and theoretical exploration. Here we illustrate how neuromodulatory state affects cortical plasticity through these two mechanisms. First, we explore the ability of neuromodulators to gate plasticity by reshaping the learning window for spike-timing-dependent plasticity. Using a simple computational model, we implement four different learning rules and demonstrate their effects on receptive field plasticity. We then compare the neuromodulatory effects of upregulating learning rate versus the effects of upregulating neuronal activity. We find that these seemingly similar mechanisms do not yield the same outcome: upregulating neuronal activity can lead to either a broadening or a sharpening of receptive field tuning, whereas upregulating learning rate only intensifies the sharpening of receptive field tuning. This simple model demonstrates the need for further exploration of the rich landscape of neuromodulator-mediated plasticity. Future experiments, coupled with biologically detailed computational models, will elucidate the diversity of mechanisms by which neuromodulatory state regulates cortical plasticity.

  16. The plasticity of social emotions.

    PubMed

    Klimecki, Olga M

    2015-01-01

    Social emotions such as empathy or compassion greatly facilitate our interactions with others. Despite the importance of social emotions, scientific studies have only recently revealed functional neural plasticity associated with the training of such emotions. Using the framework of two antagonistic neural systems, the threat and social disconnection system on the one hand, and the reward and social connection system on the other, this article describes how training compassion and empathy can change the functioning of these systems in a targeted manner. Whereas excessive empathic sharing of suffering can increase negative feelings and activations in the insula and anterior cingulate cortex (corresponding to the threat and social disconnection system), compassion training can strengthen positive affect and neural activations in the medial orbitofrontal cortex and striatum (corresponding to the reward and social connection system). These neuroimaging findings are complemented by results from behavioral studies showing that compassion is linked to helping and forgiveness behavior, whereas empathic distress not only decreases helping behavior, but is even associated with increased aggressive behavior. Taken together, these data provide encouraging evidence for the plasticity of adaptive social emotions with wide-ranging implications for basic science and applied settings.

  17. Young Plastic Surgeons Forum member survey: Part II. Advocacy in plastic surgery: opinions toward the ASPS and PlastyPAC.

    PubMed

    Ver Halen, Jon P; Chen, Andrew; Jeffers, Lynn; Basu, C Bob

    2014-08-01

    Given the continued evolution of the American health system, the authors explored young plastic surgeons' attitudes on challenges affecting the specialty and the future role of organized plastic surgery and its advocacy mission. A 21-question online survey was distributed to all members of the Young Plastic Surgeons Forum. Questions were related to demographics, attitudes toward policy issues, participation in the American Society of Plastic Surgeons, and its advocacy efforts. The survey was e-mailed to 2155 Forum members, of which 397 responded (19% response rate). Young plastic surgeons appear to be interested in American Society of Plastic Surgeons and PlastyPAC, as evidenced by a higher than normal response rate to this survey and rate of contribution. However, a lack of awareness about the details of the organizations and mechanisms for involvement remains. Scope-of-practice issues and encroachment on the specialty by noncore providers remain the top concern of young plastic surgeons. Other top concerns were financial barriers to participation in advocacy efforts and concerns with return on investment on PlastyPAC contributions. A majority received minimal or no public policy education on issues affecting plastic surgery during training. A minority currently participate in American Society of Plastic Surgeons advocacy efforts. These data represent the first such collection of opinions from Young Plastic Surgeons members regarding goals and directions of the American Society of Plastic Surgeons and PlastyPAC. These organizations are in a uniquely strong position to enlist participation from and provide for the future success of the profession's younger members.

  18. Interfacial Instabilities on a Droplet

    NASA Astrophysics Data System (ADS)

    Jalaal, Maziyar; Mehravaran, Kian

    2013-11-01

    The fragmentation of droplets is an essential stage of several natural and industrial applications such as fuel atomization and rain phenomena. In spite of its relatively long history, the mechanism of fragmentation is not clear yet. This is mainly due to small length and time scales as well as the non-linearity of the process. In the present study, two and three-dimensional numerical simulations have been performed to understand the early stages of the fragmentation of an initially spherical droplet. Simulations are performed for high Reynolds and a range of relatively high Weber numbers (shear breakup). To resolve the small-scale instabilities generated over the droplet, a second-order adaptive finite volume/volume of fluids (FV/VOF) method is employed, where the grid resolution is increased with the curvature of the gas-liquid interface as well as the vorticity magnitude. The study is focused on the onset and growth of interfacial instabilities. The role of Kelvin-Helmholtz instability (in surface wave formation) and Rayleigh-Taylor instability (in azimuthal transverse modulation) are shown and the obtained results are compared with the linear instability theories for zero and non-zero vorticity layers. Moreover, the analogy between the fragmentation of a single drop and a co-axial liquid jet is discussed. The current results can be used for the further development of the current secondary atomization models.

  19. EXPLOSIVE INSTABILITY AND CORONAL HEATING

    SciTech Connect

    Dahlburg, R. B.; Liu, J.-H.; Klimchuk, J. A.; Nigro, G.

    2009-10-20

    The observed energy-loss rate from the solar corona implies that the coronal magnetic field has a critical angle at which energy is released. It has been hypothesized that at this critical angle an 'explosive instability' would occur, leading to an enhanced conversion of magnetic energy into heat. In earlier investigations, we have shown that a shear-dependent magnetohydrodynamic process called 'secondary instability' has many of the distinctive features of the hypothetical 'explosive instability'. In this paper, we give the first demonstration that this 'secondary instability' occurs in a system with line-tied magnetic fields and boundary shearing-basically the situation described by Parker. We also show that, as the disturbance due to secondary instability attains finite amplitude, there is a transition to turbulence which leads to enhanced dissipation of magnetic and kinetic energy. These results are obtained from numerical simulations performed with a new parallelized, viscoresistive, three-dimensional code that solves the cold plasma equations. The code employs a Fourier collocation-finite difference spatial discretization, and uses a third-order Runge-Kutta temporal discretization.

  20. Kozai-Lidov disc instability

    NASA Astrophysics Data System (ADS)

    Lubow, Stephen H.; Ogilvie, Gordon I.

    2017-08-01

    Recent results by Martin et al. showed in 3D smoothed particle hydrodynamics simulations that tilted discs in binary systems can be unstable to the development of global, damped Kozai-Lidov (KL) oscillations in which the discs exchange tilt for eccentricity. We investigate the linear stability of KL modes for tilted inviscid discs under the approximations that the disc eccentricity is small and the disc remains flat. By using 1D equations, we are able to probe regimes of large ratios of outer to inner disc edge radii that are realistic for binary systems of hundreds of astronomical unit separations and are not easily probed by multidimensional simulations. For order unity binary mass ratios, KL instability is possible for a window of disc aspect ratios H/r in the outer parts of a disc that roughly scale as (nb/n)2 ≲ H/r ≲ nb/n, for binary orbital frequency nb and orbital frequency n at the disc outer edge. We present a framework for understanding the zones of instability based on the determination of branches of marginally unstable modes. In general, multiple growing eccentric KL modes can be present in a disc. Coplanar apsidal-nodal precession resonances delineate instability branches. We determine the range of tilt angles for unstable modes as a function of disc aspect ratio. Unlike the KL instability for free particles that involves a critical (minimum) tilt angle, disc instability is possible for any non-zero tilt angle depending on the disc aspect ratio.

  1. Solar wind driven dust acoustic instability with Lorentzian kappa distribution

    SciTech Connect

    Arshad, Kashif; Ehsan, Zahida; Khan, S. A.; Mahmood, S.

    2014-02-15

    In a three species electron-ion-dust plasma following a generalized non-Maxwellian distribution function (Lorentzian or kappa), it is shown that a kinetic instability of dust-acoustic mode exists. The instability threshold is affected when such (quasineutral) plasma permeates through another static plasma. Such case is of interest when the solar wind is streaming through the cometary plasma in the presence of interstellar dust. In the limits of phase velocity of the waves larger and smaller than the thermal velocity of dust particles, the dispersion properties and growth rate of dust-acoustic mode are investigated analytically with validation via numerical analysis.

  2. On the transient phase of the Faraday instability

    NASA Astrophysics Data System (ADS)

    Garih, H.; Estivalezes, J. L.; Casalis, G.

    2013-12-01

    This study pertains to the three-dimensional direct numerical simulation (DNS) of a vertically oscillating vessel containing an incompressible Newtonian liquid, surrounded by air at rest and ambient conditions. Squire's theorem was extended and shown to apply in this case, allowing for the theory of linear stability to be implemented and a comparison to be made with the DNS results. It was further discovered that the method by which a fluid instability is initiated in the numerical simulation affects the initial development of the instability. This phenomenon was confirmed through an optimal perturbations analysis. A possible physical explanation of this effect is also presented.

  3. Ion temperature gradient instability in a dusty plasma.

    PubMed

    Vranjes, J; Saleem, H; Poedts, S

    2004-05-01

    An analysis of the temperature-gradient-driven ( eta(i) ) instability of drift waves in dusty plasma is presented. Various limits that allow for the coupling of the drift wave with the dynamics of dust grains are discussed. In particular, the cases of tiny (magnetized) and relatively heavy (unmagnetized) grains are studied. It is shown that in both limits the behavior of the eta(i) mode is considerably affected by the dust dynamics. The growth rate turns out to be higher in the presence of dust, and the instability threshold is lower, resulting in a more unstable plasma.

  4. Competing Turing and Faraday Instabilities in Longitudinally Modulated Passive Resonators.

    PubMed

    Copie, François; Conforti, Matteo; Kudlinski, Alexandre; Mussot, Arnaud; Trillo, Stefano

    2016-04-08

    We experimentally investigate the interplay of Turing (modulational) and Faraday (parametric) instabilities in a bistable passive nonlinear resonator. The Faraday branch is induced via parametric resonance owing to a periodic modulation of the resonator dispersion. We show that the bistable switching dynamics is dramatically affected by the competition between the two instability mechanisms, which dictates two completely novel scenarios. At low detunings from resonance, switching occurs between the stable stationary lower branch and the Faraday-unstable upper branch, whereas at high detunings we observe the crossover between the Turing and Faraday periodic structures. The results are well explained in terms of the universal Lugiato-Lefever model.

  5. Modulation instability of laser pulse in magnetized plasma

    SciTech Connect

    Jha, Pallavi; Kumar, Punit; Raj, Gaurav; Upadhyaya, Ajay K.

    2005-12-15

    Modulation instability of a laser pulse propagating through transversely magnetized underdense plasma is studied. It is observed that interaction of laser radiation with plasma in the presence of uniform magnetic field results in an additional perturbed transverse plasma current density along with the relativistic and ponderomotive nonlinear current densities, thus affecting the modulational interaction. In the plane wave limit it is observed that modulational interaction is more stable for magnetized plasma as compared to the unmagnetized case. The analysis shows that there is a significant reduction in the growth rate of modulation instability over a given range of unstable wave numbers due to magnetization of plasma.

  6. Plastics in Perspective.

    ERIC Educational Resources Information Center

    Bergandine, David R.; Holm, D. Andrew

    The materials in this curriculum supplement, developed for middle school or high school science classes, present solid waste problems related to plastics. The set of curriculum materials is divided into two units to be used together or independently. Unit I begins by comparing patterns in solid waste from 1960 to 1990 and introducing methods for…

  7. Preserving in Plastic.

    ERIC Educational Resources Information Center

    Wahla, James

    1985-01-01

    Outlines steps for casting insects in permanent molds prepared from commercially available liquid plastic. Also describes dry mountings in glass, acrylic, and petri dishes. The rationale for specimen use, hints for producing quality results, purchasing information, and safety precautions are considered. (DH)

  8. Hydrodynamic Elastic Magneto Plastic

    SciTech Connect

    Wilkins, M. L.; Levatin, J. A.

    1985-02-01

    The HEMP code solves the conservation equations of two-dimensional elastic-plastic flow, in plane x-y coordinates or in cylindrical symmetry around the x-axis. Provisions for calculation of fixed boundaries, free surfaces, pistons, and boundary slide planes have been included, along with other special conditions.

  9. New plastic recycling technology

    EPA Science Inventory

    Greater than 60% of the total plastic content of municipal solid waste is comprised of polyolefins (high-density, low-density, and linear polyethylene and polypropylene. Polyethylene (PE) is the largest-volume component but presents a challenge due to the absence of low-energy de...

  10. Development of a Practical Methodology for Elastic-Plastic and Fully Plastic Fatigue Crack Growth

    NASA Technical Reports Server (NTRS)

    McClung, R. C.; Chell, G. G.; Lee, Y.-D.; Russell, D. A.; Orient, G. E.

    1999-01-01

    A practical engineering methodology has been developed to analyze and predict fatigue crack growth rates under elastic-plastic and fully plastic conditions. The methodology employs the closure-corrected effective range of the J-integral, (Delta)J(sub eff), as the governing parameter. The methodology contains original and literature J and (Delta)J solutions for specific geometries, along with general methods for estimating J for other geometries and other loading conditions, including combined mechanical loading and combined primary and secondary loading. The methodology also contains specific practical algorithms that translate a J solution into a prediction of fatigue crack growth rate or life, including methods for determining crack opening levels, crack instability conditions, and material properties. A critical core subset of the J solutions and the practical algorithms has been implemented into independent elastic-plastic NASGRO modules. All components of the entire methodology, including the NASGRO modules, have been verified through analysis and experiment, and limits of applicability have been identified.

  11. Development of a Practical Methodology for Elastic-Plastic and Fully Plastic Fatigue Crack Growth

    NASA Technical Reports Server (NTRS)

    McClung, R. C.; Chell, G. G.; Lee, Y. -D.; Russell, D. A.; Orient, G. E.

    1999-01-01

    A practical engineering methodology has been developed to analyze and predict fatigue crack growth rates under elastic-plastic and fully plastic conditions. The methodology employs the closure-corrected effective range of the J-integral, delta J(sub eff) as the governing parameter. The methodology contains original and literature J and delta J solutions for specific geometries, along with general methods for estimating J for other geometries and other loading conditions, including combined mechanical loading and combined primary and secondary loading. The methodology also contains specific practical algorithms that translate a J solution into a prediction of fatigue crack growth rate or life, including methods for determining crack opening levels, crack instability conditions, and material properties. A critical core subset of the J solutions and the practical algorithms has been implemented into independent elastic-plastic NASGRO modules. All components of the entire methodology, including the NASGRO modules, have been verified through analysis and experiment, and limits of applicability have been identified.

  12. Costs of plasticity in foraging characteristics of the clonal plant Ranunculus reptans.

    PubMed

    van Kleunen, M; Fischer, M; Schmid, B

    2000-12-01

    In clonal plants, evolution of plastic foraging by increased lengths of leaves and internodes under unfavourable conditions may be constrained by costs and limits of plasticity. We studied costs and limits of plasticity in foraging characteristics in 102 genotypes of the stoloniferous herb Ranunculus reptans. We grew three replicates of each genotype with and three without competition by the naturally co-occuring grass Agrostis stolonifera. We used regression and correlation analyses to investigate potential costs of plasticity in lengths of leaves and stolon internodes, developmental instability costs of these traits, and a developmental range limit of these traits. We used randomization procedures to control for spurious correlations between parameters calculated from the same data. Under competition the number of rosettes, rooted rosettes, and flowers was 58%, 40%, and 61% lower, respectively, than in the absence of competition. Under competition lengths of leaves and stolon internodes were 14% and 6% smaller, respectively, than in the absence of competition. We detected significant costs of plasticity in stolon internode length in the presence of competition when fitness was measured in terms of the number of rosettes and the number of flowers (selection gradients against plasticity were 0.250 and 0.214, respectively). Within-environment variation (SD) in both foraging traits was not positively correlated with the corresponding plasticity, which indicates that there were no developmental instability costs. More plastic genotypes did not have less extreme trait values than less plastic genotypes for both foraging traits, which indicates that there was no developmental range limit. We conclude that in R. reptans costs of plasticity more strongly constrain evolution of foraging in the horizontal plane (i.e., stolon internode length) than in the vertical plane (i.e., leaf length).

  13. American Society of Plastic Surgeons

    MedlinePlus

    ... PRS PRS GO PSN PSEN GRAFT Contact Us Cosmetic Surgery New procedures and advanced technologies offer plastic ... a board-certified plastic surgeon to perform your cosmetic or reconstructive surgery. ASPS member surgeons have the ...

  14. Instability of EDS maglev systems

    SciTech Connect

    Cai, Y.; Chen, S.S.

    1993-09-01

    Instabilities of an EDS maglev suspension system with 3 D.O.F. and 5 D.O.F. vehicles traveling on a double L-shaped set of guideway conductors have been investigated with various experimentally measured magnetical force data incorporated into the theoretical models. Divergence and flutter are obtained from both analytical and numerical solutions for coupled vibration of the 3 D.O.F. maglev vehicle model. Instabilities of five direction motions (heave, slip, rill, pitch and yaw) are observed for the 4 D.O.F. vehicle model. It demonstrates that system parameters, such as, system damping, vehicle geometry and coupling effects among five different motions play very important roles in the occurrence of dynamic instabilities of maglev vehicles.

  15. Thermocapillary instabilities with gravity modulation

    NASA Astrophysics Data System (ADS)

    Zebib, Abdelfattah

    2002-11-01

    We study vibrational thermocapillary instabilities in an infinite layer with one bounding surface rigid, the other free and nondeformable, and both adiabatic. A constant temperature gradient imposed on the free surface drives a return flow, and a zero-mean harmonic gravitational acceleration is assumed to model g-jitter. Linear stability of the time-periodic base state is determined by calculating the Floquet exponents in the parameter space of: the Marangoni number Ma, Rayleigh number Ra, dimensionless frequency Ω, Prandtl number Pr, and wavenumbers α and β. The stability boundaries are composed of two intersecting branches emanating from the points of pure thermocapilary or buoyant instabilities as was found in the 2D study β=0 by Suresh & Homsy (Phys. Fluids 2001). However, 3D instabilities continue to dominate as was found by Smith & Davis (JFM 1983) with Ra=0. We also find that the region of stablity grows with increasing Ω.

  16. Compressive Instability Phenomena During Springback

    NASA Astrophysics Data System (ADS)

    Kim, J.-B.; Yoon, J. W.; Yang, D. Y.

    2007-05-01

    Springback in sheet metal product makes difficulties in die design because small strain causes large displacement. Especially for the sheet metal product having small geometric constraints, springback displacement may become severe. After first stage of stamping of outer case of washing machine, a large amount of springback is observed. The stamping depth of the outer case is small while stamping area is very large compared to the stamping depth, and therefore, there exists small geometric constraints in the formed part. Also, a compressive instability during the elastic recovery takes place and this instability enlarged the elastic recovery and dimensional error. In this paper, the compressive instability during the elastic recovery is analyzed using bifurcation theory. The final deformed shape after springback is obtained by bifurcating the solution path from primary to secondary. The deformed shapes obtained by the finite element analysis are in good agreement with the experimental data. The bifurcation behavior and the springback displacement for different forming depth are investigated.

  17. Compressive Instability Phenomena During Springback

    SciTech Connect

    Kim, J.-B.; Yoon, J. W.; Yang, D. Y.

    2007-05-17

    Springback in sheet metal product makes difficulties in die design because small strain causes large displacement. Especially for the sheet metal product having small geometric constraints, springback displacement may become severe. After first stage of stamping of outer case of washing machine, a large amount of springback is observed. The stamping depth of the outer case is small while stamping area is very large compared to the stamping depth, and therefore, there exists small geometric constraints in the formed part. Also, a compressive instability during the elastic recovery takes place and this instability enlarged the elastic recovery and dimensional error. In this paper, the compressive instability during the elastic recovery is analyzed using bifurcation theory. The final deformed shape after springback is obtained by bifurcating the solution path from primary to secondary. The deformed shapes obtained by the finite element analysis are in good agreement with the experimental data. The bifurcation behavior and the springback displacement for different forming depth are investigated.

  18. Hydrodynamick instabilities on ICF capsules

    SciTech Connect

    Haan, S.W.

    1991-06-07

    This article summarizes our current understanding of hydrodynamic instabilities as relevant to ICF. First we discuss classical, single mode Rayleigh-Taylor instability, and nonlinear effects in the evolution of a single mode. Then we discuss multimode systems, considering: (1) the onset of nonlinearity; (2) a second order mode coupling theory for weakly nonlinear effects, and (3) the fully nonlinear regime. Two stabilization mechanisms relevant to ICF are described next: gradient scale length and convective stabilization. Then we describe a model which is meant to estimate the weakly nonlinear evolution of multi-mode systems as relevant to ICF, given the short-wavelength stabilization. Finally, we discuss the relevant code simulation capability, and experiments. At this time we are quite optimistic about our ability to estimate instability growth on ICF capsules, but further experiments and simulations are needed to verify the modeling. 52 refs.

  19. Gravitational instabilities in protostellar disks

    NASA Technical Reports Server (NTRS)

    Tohline, J. E.

    1994-01-01

    The nonaxisymmetric stability of self-gravitating, geometrically thick accretion disks has been studied for protostellar systems having a wide range of disk-to-central object mass ratios. Global eigenmodes with four distinctly different characters were identified using numerical, nonlinear hydrodynamic techniques. The mode that appears most likely to arise in normal star formation settings, however, resembles the 'eccentric instability' that was identified earlier in thin, nearly Keplerian disks: It presents an open, one-armed spiral pattern that sweeps continuously in a trailing direction through more than 2-pi radians, smoothly connecting the inner and outer edges of the disk, and requires cooperative motion of the point mass for effective amplification. This particular instability promotes the development of a single, self-gravitating clump of material in orbit about the point mass, so its routine appearance in our simulations supports the conjecture that the eccentric instability provides a primary route to the formation of short-period binaries in protostellar systems.

  20. Faraday instability in deformable domains

    NASA Astrophysics Data System (ADS)

    Pucci, Giuseppe; Ben Amar, Martine; Couder, Yves

    2014-11-01

    We investigate the Faraday instability in floating liquid lenses, as an example of hydrodynamic instability that develops in a domain with flexible boundaries. We show that a mutual adaptation of the instability pattern and the domain shape occurs, as a result of the competition between the wave radiation pressure and the capillary response of the lens border. Two archetypes of behaviour are observed. In the first, stable shapes are obtained experimentally and predicted theoretically as the exact solutions of a Riccati equation, and they result from the equilibrium between wave radiation pressure and capillarity. In the second, the radiation pressure exceeds the capillary response of the lens border and leads to non-equilibrium behaviours, with breaking into smaller domains that have a complex dynamics including spontaneous propagation. The authors are grateful to Université Franco-Italienne (UFI) for financial support.

  1. Interfacial Instability during Granular Erosion.

    PubMed

    Lefebvre, Gautier; Merceron, Aymeric; Jop, Pierre

    2016-02-12

    The complex interplay between the topography and the erosion and deposition phenomena is a key feature to model granular flows such as landslides. Here, we investigated the instability that develops during the erosion of a wet granular pile by a dry dense granular flow. The morphology and the propagation of the generated steps are analyzed in relation to the specific erosion mechanism. The selected flowing angle of the confined flow on a dry heap appears to play an important role both in the final state of the experiment, and for the shape of the structures. We show that the development of the instability is governed by the inertia of the flow through the Froude number. We model this instability and predict growth rates that are in agreement with the experiment results.

  2. Stellar explosions, instabilities, and turbulence

    SciTech Connect

    Drake, R. P.; Kuranz, C. C.; Miles, A. R.; Muthsam, H. J.; Plewa, T.

    2009-04-15

    It has become very clear that the evolution of structure during supernovae is centrally dependent on the pre-existing structure in the star. Modeling of the pre-existing structure has advanced significantly, leading to improved understanding and to a physically based assessment of the structure that will be present when a star explodes. It remains an open question whether low-mode asymmetries in the explosion process can produce the observed effects or whether the explosion mechanism somehow produces jets of material. In any event, the workhorse processes that produce structure in an exploding star are blast-wave driven instabilities. Laboratory experiments have explored these blast-wave-driven instabilities and specifically their dependence on initial conditions. Theoretical work has shown that the relative importance of Richtmyer-Meshkov and Rayleigh-Taylor instabilities varies with the initial conditions and does so in ways that can make sense of a range of astrophysical observations.

  3. The Effects of Contact Conditions on the Onset of Shear Instability in Cold-Spray

    NASA Astrophysics Data System (ADS)

    Meng, Fanchao; Aydin, Huseyin; Yue, Stephen; Song, Jun

    2015-04-01

    Using ABAQUS/Explicit, the effects of contact conditions between the particle and substrate, including tangential friction, normal constraint, and contact geometry on the plastic deformation during the cold-spray process are studied. It was found that the onset of shear instability, an event often used to indicate the establishment of bonding, is very sensitive to the choice of contact conditions. This suggests that the onset of shear instability does not serve as an accurate means to identify the plasticity threshold responsible for bonding. On the other hand, it is demonstrated that the evolution of the overall equivalent plastic strain (i.e., ) and the overall von Mises stress, being linearly proportional to each other, are both independent of contact conditions. Furthermore, it is shown that an energy value, defined as the product of the and the von Mises stress integrated over all particle elements, can quantitatively represent the energy dissipated via plastic deformation while being independent of contact conditions. The and associated energy value as defined may provide robust tools to assess the plasticity and the consequent bonding during cold-spray.

  4. Nova Experiments Examining Raleigh-Taylor Instability in Materials with Strength

    SciTech Connect

    Weber, S.V.; Kalantar, D.H.; Colvin, J.D.; Gold, D.M.; Mikaelian, K.O.; Remington, B.A.; Wiley, L.G.

    1999-10-06

    Material strength can affect the growth of the Rayleigh-Taylor instability in solid materials, where growth occurs through plastic flow. In order to study this effect at megabar pressures, we have shocked metal foils using hohlraum x-ray drive on Nova, and observed the growth of pre-imposed modulations with x-ray radiography. Previous experiments employing Cu foils did not conclusively show strength effects for resolvable wavelengths. Therefore, we have redesigned the experiment to use aluminum foils. As aluminum has higher specific strength at pressures {approx}1 Mbar, the new design is predicted to show growth reduction due to strength of at least a factor of two for some wavelengths in the observable range of 10 - 50 {micro}m. We have also modified the drive history to extend the interval of uniform acceleration and to reduce the risk of melting the foils with coalesced shocks. The design changes, as well as Nova operational constraints, limit peak pressures to 1-1.5 Mbar. Foil surface motion has been measured with high sensitivity by laser interferometry to look for thermal expansion due to preheat. We have continued to pursue dynamic x-ray diffraction as the most definitive measurement of crystal state.

  5. Bipolar disorder dynamics: affective instabilities, relaxation oscillations and noise

    PubMed Central

    Geddes, John R.; Goodwin, Guy M.; Holmes, Emily A.

    2015-01-01

    Bipolar disorder is a chronic, recurrent mental illness characterized by extreme episodes of depressed and manic mood, interspersed with less severe but highly variable mood fluctuations. Here, we develop a novel mathematical approach for exploring the dynamics of bipolar disorder. We investigate how the dynamics of subjective experience of mood in bipolar disorder can be understood using a relaxation oscillator (RO) framework and test the model against mood time-series fluctuations from a set of individuals with bipolar disorder. We show that variable mood fluctuations in individuals diagnosed with bipolar disorder can be driven by the coupled effects of deterministic dynamics (captured by ROs) and noise. Using a statistical likelihood-based approach, we show that, in general, mood dynamics are described by two independent ROs with differing levels of endogenous variability among individuals. We suggest that this sort of nonlinear approach to bipolar disorder has neurobiological, cognitive and clinical implications for understanding this mental illness through a mechacognitive framework. PMID:26577592

  6. Driving factors of electro-convective instability in concentration polarization

    NASA Astrophysics Data System (ADS)

    Abu-Rjal, Ramadan; Rubinstein, Isaak; Zaltzman, Boris

    2016-06-01

    Until recently, based on the analysis pertaining to a perfectly charge selective interface, electro-convective instability in concentration polarization was attributed to the nonequilibrium mechanism related to the extended space charge which forms next to that of the electric double layer near the limiting current. More recently it was shown that imperfect charge selectivity of the interface makes equilibrium instability possible, driven by either equilibrium electro-osmosis or bulk electro-convection, or both. In this paper we identify and analyze the major surface and bulk factors affecting the electro-convective instability. These factors, some known previously under the names of diffusio-osmosis, electro-osmosis, or bulk electro-convection, and some newly identified in this paper are manifestations of the electric force and pressure gradient, balanced by the viscous force acting in various locations in solution. The contribution of these factors to hydrodynamic stability in concentration polarization is analyzed for a varying charge selectivity of the interface.

  7. Electromechanical instability in soft materials: Theory, experiments and applications

    NASA Astrophysics Data System (ADS)

    Suo, Zhigang

    2013-03-01

    Subject to a voltage, a membrane of a dielectric elastomer reduces thickness and expands area, possibly straining over 100%. The phenomenon is being developed as transducers for broad applications, including soft robots, adaptive optics, Braille displays, and electric generators. The behavior of dielectric elastomers is closely tied to electromechanical instability. This instability may limit the performance of devices, and may also be used to achieve giant actuation strains. This talk reviews the theory of dielectric elastomers, coupling large deformation and electric potential. The theory is developed within the framework of continuum mechanics and thermodynamics. The theory attempts to answer commonly asked questions. How do mechanics and electrostatics work together to generate large deformation? How efficiently can a material convert energy from one form to another? How do molecular processes affect macroscopic behavior? The theory is used to describe electromechanical instability, and is related to recent experiments.

  8. Transient growth of droplet instabilities in a stream

    SciTech Connect

    Jalaal, M. E-mail: m-jalaal@yahoo.com; Mehravaran, K.

    2014-01-15

    Droplet deformation is the first stage of all aerodynamically induced-breakups, considerably affecting the characteristics of the atomization. In the present study, using an adaptive volume of fluid method, two and three-dimensional direct numerical simulations have been performed to understand droplet deformation. A high Reynolds number and a range of relatively high Weber numbers are chosen, addressing the shear breakup of droplets in a stream. The study is focused on the initiation and growth of instabilities over the droplet. The role of Kelvin-Helmholtz and Rayleigh-Taylor instabilities in wave formation and azimuthal transverse modulation are shown and the obtained results for the most amplified wave-numbers are compared with instability theories for zero and non-zero vorticity layers. The present results for the most amplified wave-numbers and deformation topologies are in good agreement with the previous experimental results.

  9. Critical dynamics of burst instabilities in the Portevin-Le Ch atelier effect.

    PubMed

    D'Anna, G; Nori, F

    2000-11-06

    We investigate the Portevin-Le Châtelier effect (PLC), by compressing Al-Mg alloys in a very large deformation range, and interpret the results from the viewpoint of phase transitions and critical phenomena. The system undergoes two dynamical phase transitions between intermittent (or "jerky") and "laminar" plastic dynamic phases. Near these two dynamic critical points, the order parameter 1/tau of the PLC effect exhibits large fluctuations, and "critical slowing down" (i.e., the number tau of bursts, or plastic instabilities, per unit time slows down considerably).

  10. Beam instabilities in hadron synchrotrons

    DOE PAGES

    Metral, E.; T. Argyropoulos; Bartosik, H.; ...

    2016-04-01

    Beam instabilities cover a wide range of effects in particle accelerators and they have been the subjects of intense research for several decades. As the machines performance was pushed new mechanisms were revealed and nowadays the challenge consists in studying the interplays between all these intricate phenomena, as it is very often not possible to treat the different effects separately. Furthermore, the aim of this paper is to review the main mechanisms, discussing in particular the recent developments of beam instability theories and simulations.

  11. Beam instabilities in hadron synchrotrons

    SciTech Connect

    Metral, E.; T. Argyropoulos; Bartosik, H.; Biancacci, N.; Buffat, X.; Esteban Muller, J. F.; Herr, W.; Iadarola, G.; Lasheen, A.; Li, K.; Pieloni, T.; Quartullo, D.; Rumolo, G.; Salvant, B.; Shaposhnikova, E.; Tambasco, C.; Timko, H.; Zannini, C.; Burov, A.; Banfi, D.; Barranco, J.; Mounet, N.; Boine-Frankenheim, O.; Niedermayer, U.; Kornilov, V.; White, S.

    2016-04-01

    Beam instabilities cover a wide range of effects in particle accelerators and they have been the subjects of intense research for several decades. As the machines performance was pushed new mechanisms were revealed and nowadays the challenge consists in studying the interplays between all these intricate phenomena, as it is very often not possible to treat the different effects separately. Furthermore, the aim of this paper is to review the main mechanisms, discussing in particular the recent developments of beam instability theories and simulations.

  12. Political instability and illegal immigration.

    PubMed

    Campos, J E; Lien, D

    1995-01-01

    "Economic theory suggests that transnational migration results from the push-pull effect of wage differentials between host and source countries. In this paper, we argue that political instability exacerbates the migration flow, with greater instability leading to relatively larger flows. We conclude then that an optimal solution to the illegal immigration problem requires proper coordination of immigration and foreign policies by the host country. A narrow preoccupation with tougher immigration laws is wasteful and may be marginally effective." Emphasis is on the United States as a host country.

  13. Undulation Instability of Epithelial Tissues

    NASA Astrophysics Data System (ADS)

    Basan, Markus; Joanny, Jean-François; Prost, Jacques; Risler, Thomas

    2011-04-01

    Treating the epithelium as an incompressible fluid adjacent to a viscoelastic stroma, we find a novel hydrodynamic instability that leads to the formation of protrusions of the epithelium into the stroma. This instability is a candidate for epithelial fingering observed in vivo. It occurs for sufficiently large viscosity, cell-division rate and thickness of the dividing region in the epithelium. Our work provides physical insight into a potential mechanism by which interfaces between epithelia and stromas undulate and potentially by which tissue dysplasia leads to cancerous invasion.

  14. Research on aviation fuel instability

    NASA Technical Reports Server (NTRS)

    Baker, C. E.; Bittker, D. A.; Cohen, S. M.; Seng, G. T.

    1984-01-01

    The problems associated with aircraft fuel instability are discussed. What is currently known about the problem is reviewed and a research program to identify those areas where more research is needed is discussed. The term fuel instability generally refers to the gums, sediments, or deposits which can form as a result of a set of complex chemical reactions when a fuel is stored for a long period at ambient conditions or when the fuel is thermally stressed inside the fuel system of an aircraft.

  15. Stringy bounces and gradient instabilities

    NASA Astrophysics Data System (ADS)

    Giovannini, Massimo

    2017-04-01

    Bouncing solutions are obtained from a generally covariant action characterized by a potential which is a nonlocal functional of the dilaton field at two separated space-time points. Gradient instabilities are shown to arise in this context but they are argued to be nongeneric. After performing a gauge-invariant and a frame-invariant derivation of the evolution equations of the fluctuations, a heuristic criterion for the avoidance of pathological instabilities is proposed and corroborated by a number of explicit examples that turn out to be compatible with a quasiflat spectrum of curvature inhomogeneities for large wavelengths.

  16. Plastics for Elementary School Children

    ERIC Educational Resources Information Center

    Hanson, Jack

    1977-01-01

    Describes three plastics projects (which involve making a styrene fishing bobber, an acrylic salad fork and spoon set, and acetate shrink art) designed to provide elementary level students an opportunity to work with plastics and to learn about careers in plastics production and distribution. (TA)

  17. Plastics for Elementary School Children

    ERIC Educational Resources Information Center

    Hanson, Jack

    1977-01-01

    Describes three plastics projects (which involve making a styrene fishing bobber, an acrylic salad fork and spoon set, and acetate shrink art) designed to provide elementary level students an opportunity to work with plastics and to learn about careers in plastics production and distribution. (TA)

  18. Localized Plastic Deformation in Colloidal Micropillars

    NASA Astrophysics Data System (ADS)

    Strickland, Daniel; Hor, Jyo Lyn; Ortiz, Carlos; Lee, Daeyeon; Gianola, Daniel

    When driven beyond yield, many amorphous solids exhibit concentrated regions of large plastic strain referred to as shear bands. Shear bands are the result of localized, cooperative rearrangements of particles known as shear transformations (STs). STs are dilatory: their operation results in an increase of free volume and local softening that leads to spatially concentrated plasticity. However, the evolution of STs into a macroscopic shear band remains poorly understood. To study the process, we perform compression experiments on amorphous colloidal micropillars. The micropillars, which are composed of fluorescent 3 μm PMMA particles, are made freestanding so that shear banding instabilities are not suppressed by confining boundaries. During compression, we observe strong localization of strain in a band of the pillar. As deformation proceeds, the sheared region continues to dilate until it reaches the colloidal glass transition, at which point dilation terminates. We quantify a length scale by measuring the extent of spatial correlations in strain. This length scale decreases gradually with increasing dilation and becomes static beyond the glass transition. Our results reinforce the idea of yield as a stress-induced glass transition in amorphous solids.

  19. GABAA receptor plasticity in Jurkat T cells.

    PubMed

    Dionisio, Leonardo; Arias, Verónica; Bouzat, Cecilia; Esandi, María del Carmen

    2013-12-01

    GABAA receptors (GABAAR) mediate inhibitory neurotransmission in the human brain. Neurons modify subunit expression, cellular distribution and function of GABAAR in response to different stimuli, a process named plasticity. Human lymphocytes have a functional neuronal-like GABAergic system with GABAAR acting as inhibitors of proliferation. We here explore if receptor plasticity occurs in lymphocytes. To this end, we analyzed human T lymphocyte Jurkat cells exposed to different physiological stimuli shown to mediate plasticity in neurons: GABA, progesterone and insulin. The exposure to 100 μM GABA differently affected the expression of GABAAR subunits measured at both the mRNA and protein level, showing an increase of α1, β3, and γ2 subunits but no changes in δ subunit. Exposure of Jurkat cells to different stimuli produced different changes in subunit expression: 0.1 μM progesterone decreased δ and 0.5 μM insulin increased β3 subunits. To identify the mechanisms underlying plasticity, we evaluated the Akt pathway, which is involved in the phosphorylation of β subunits and receptor translocation to the membrane. A significant increase of phosphorylated Akt and on the expression of β3 subunit in membrane occurred in cells exposed 15 h to GABA. To determine if plastic changes are translated into functional changes, we performed whole cell recordings. After 15 h GABA-exposure, a significantly higher percentage of cells responded to GABA application when compared to 0 and 40 h exposure, thus indicating that the detected plastic changes may have a role in GABA-modulated lymphocyte function. Our results reveal that lymphocyte GABAAR are modified by different stimuli similarly and by similar mechanisms to those in neurons. This property is of significance for the development of future therapies involving pharmacological modulation of the immune response. Copyright © 2013 Elsevier Masson SAS. All rights reserved.

  20. Effect of distributed heat source on low frequency thermoacoustic instabilities

    NASA Astrophysics Data System (ADS)

    Li, Lei; Yang, Lijun; Sun, Xiaofeng

    2013-06-01

    The problem of thermoacoustic instabilities in the combustor of modern air-breathing engines has become a topic of concern, which occurs as a result of unstable coupling between the heat release fluctuations and acoustic perturbations. A three-dimensional thermoacoustic model including the distributed non-uniform heat source and non-uniform flow is developed based on the domain decomposition spectral method. The importance of distributed heat source on combustion instabilities of longitudinal modes is analyzed with the help of a simplified geometrical configuration of combustor. The results show that the longitudinal distribution of heat source has a crucial effect on instabilities. In addition, the effect of circumferentially non-uniform heat source and non-uniform flow on longitudinal instabilities is also investigated. It can be found that the influence of circumferential non-uniformity can become significant on the lowest frequency instabilities, in particular, the oscillation frequency and growth rate are all evidently affected by temperature non-uniformity and time delay non-uniformity.

  1. Quality assessment of confocal microscopy slide-based systems: instability.

    PubMed

    Zucker, Robert M

    2006-07-01

    All slide-based fluorescence cytometry detections systems basically include an excitation light source, intermediate optics, and a detection device (CCD or PMT). Occasionally, this equipment becomes unstable, generating unreliable and inferior data. A number of tests have been devised to evaluate equipment performance and instability. The following four instability tests are described: galvanometer scanning, stage drift, correct wavelength spectral detection, and long-term laser power. Quality assurance tests revealed that a confocal microscope can become unstable in the following parameters, yielding inaccurate data: laser power, PMTs functionality, spectrophotometer accuracy, galvanometer scanning and laser stability, and stage drift. Long-term laser power stability has been observed to vary greatly. Confocal systems can become unstable in the following parameters: long-term laser power, galvanometer scanning, spectrophotometer accuracy, and stage stability. Instability in any of these parameters will affect image quality. Laser power fluctuations result from either a defective Acousto-optic tunable filter or improper heat dissipation. Spectrophotometer instability will generate unreliable spectra data, extra light reflections, and poor image quality. Galvanometer scanning instability yields poor image quality while microscope stage drift results in a sample going out of the plane of focus. With minor modifications, these tests may be applicable to other slide-based systems. Copyright 2006 International Society for Analytical Cytology.

  2. Fast Transverse Instability and Electron Cloud Measurements in Fermilab Recycler

    SciTech Connect

    Eldred, Jeffery; Adamson, Philip; Capista, David; Eddy, Nathan; Kourbanis, Ioanis; Morris, Denton; Thangaraj, Jayakar; Yang, Ming-Jen; Zwaska, Robert; Ji, Yichen

    2015-03-01

    A new transverse instability is observed that may limit the proton intensity in the Fermilab Recycler. The instability is fast, leading to a beam-abort loss within two hundred turns. The instability primarily affects the first high-intensity batch from the Fermilab Booster in each Recycler cycle. This paper analyzes the dynamical features of the destabilized beam. The instability excites a horizontal betatron oscillation which couples into the vertical motion and also causes transverse emittance growth. This paper describes the feasibility of electron cloud as the mechanism for this instability and presents the first measurements of the electron cloud in the Fermilab Recycler. Direct measurements of the electron cloud are made using a retarding field analyzer (RFA) newly installed in the Fermilab Recycler. Indirect measurements of the electron cloud are made by propagating a microwave carrier signal through the beampipe and analyzing the phase modulation of the signal. The maximum betatron amplitude growth and the maximum electron cloud signal occur during minimums of the bunch length oscillation.

  3. A QSPR for the plasticization efficiency of polyvinylchloride plasticizers.

    PubMed

    Chandola, Mridula; Marathe, Sujata

    2008-01-01

    A simple quantitative structure property relationship (QSPR) for correlating the plasticization efficiency of 25 polyvinylchloride (PVC) plasticizers was obtained using molecular modeling. The plasticizers studied were-aromatic esters (phthalate, terephthalate, benzoate, trimellitate), aliphatic esters (adipate, sebacate, azelate), citrates and a phosphate. The low temperature flex point, Tf, of plasticized polyvinylchloride resins was considered as an indicator of plasticization efficiency. Initially, we attempted to predict plasticization efficiency of PVC plasticizers from physical and structural descriptors derived from the plasticizer molecule alone. However, the correlation of these descriptors with Tf was not very good with R=0.78 and r2=0.613. This implied that the selected descriptors were unable to predict all the interactions between PVC and plasticizer. Hence, to account for these interactions, a model containing two polyvinylchloride (PVC) chain segments along with a plasticizer molecule in a simulation box was constructed, using molecular mechanics. A good QSPR equation correlating physical and structural descriptors derived from the model to Tf of the plasticized resins was obtained with R=0.954 and r2=0.909.

  4. Conductive Plastic Electrodes Reduce EEG Artifact During Pediatric ECMO Therapy.

    PubMed

    Matsumoto, Joyce H; McArthur, David L; Szeliga, Conrad W; Lerner, Jason T; Rao, Lekha M; Hussain, Shaun A; Wu, Joyce Y; Nuwer, Marc R; Sankar, Raman

    2016-10-01

    Extracorporeal membrane oxygenation (ECMO) is a life-saving heart and lung bypass procedure that can cause substantial EEG artifact. Continuous EEG monitoring is nonetheless a helpful neuromonitoring tool for patients receiving ECMO therapy because neurologic complications are frequent, but factors such as sedation, neuromuscular blockade, and hemodynamic instability limit clinical and radiographic evaluation. We examined whether using conductive plastic electrodes in place of conventional gold electrodes reduces artifact in clinical EEG studies of pediatric ECMO patients. Four masked electroencephalographers assessed artifact and its impact on overall EEG interpretation in samples from 21 consecutive EEGs recorded during ECMO therapy (14 gold and 7 plastic). A spectral power analysis then quantified 50- to 70-Hz artifact in a larger group of 14 gold and 34 plastic electrode studies during ECMO and 4 non-ECMO gold electrode studies. The masked electroencephalographers identified less artifact (P < 0.001) and indicated greater confidence in the accuracy of EEG interpretation (P < 0.001) among studies recorded with plastic electrodes. In quantitative analyses, ECMO was associated with greater 50- to 70-Hz power among studies using gold electrodes (P < 0.001) and gold electrodes exhibited greater 50- to 70-Hz power than plastic electrodes (P < 0.001). Contrasting studies in which most of the electroencephalographers believed that interpretation was (n = 12; 7 gold and 5 plastic) or was not (n = 7; all gold) compromised by artifact, 50- to 70-Hz power was similarly higher among the compromised studies (P < 0.001). Plastic electrodes substantially reduce the burden of electrical artifact in EEG studies performed on pediatric ECMO patients and improve confidence in EEG interpretation.

  5. A comparison of analytical techniques for modeling the Rayleigh-Taylor response of elastic-plastic solids

    SciTech Connect

    Robinson, A.C.

    1988-04-01

    The Rayleigh-Taylor instability response of elastic-plastic solids can be modeled by approximate means. However, neither the linear elastic response equation nor the so-called /open quotes/minimum amplitude/close quotes/ instability criterion derived from rigid plastic analyses is sufficient to describe overall stability characteristics at very large driving pressures. We compare several versions of the modal or one-degree-of-freedom approximation technique and indicate the common features which must be included to obtain the qualitative response seen in numerical experiments.

  6. Ingestion of plastic marine debris by longnose lancetfish (Alepisaurus ferox) in the North Pacific Ocean.

    PubMed

    Jantz, Lesley A; Morishige, Carey L; Bruland, Gregory L; Lepczyk, Christopher A

    2013-04-15

    Plastic marine debris affects species on most trophic levels, including pelagic fish. While plastic debris ingestion has been investigated in planktivorous fish in the North Pacific Ocean, little knowledge exists on piscivorous fish. The objectives of this study were to determine the frequency of occurrence and the composition of ingested plastic marine debris in longnose lancetfish (Alepisaurus ferox), a piscivorous fish species captured in the Hawaii-based pelagic longline fishery. Nearly a quarter (47 of 192) of A. ferox sampled contained plastic marine debris, primarily in the form of plastic fragments (51.9%). No relationship existed between size (silhouette area) or amount of plastic marine debris ingested and morphometrics of A. ferox. Although A. ferox are not consumed by humans, they are common prey for fish commercially harvested for human consumption. Further research is needed to determine residence time of ingested plastic marine debris and behavior of toxins associated with plastic debris.

  7. Impact of the nature and concentration of plasticizers on the ability of PVC to sorb drug.

    PubMed

    Al Salloum, H; Saunier, J; Aymes-Chodur, C; Barakat, H; Yagoubi, N

    2015-12-30

    The sorption of a drug by an infusion set may dramatically reduce the drug delivery efficiency. In this paper, we investigated how the drug sorption, in static conditions, is affected by the plasticizer's nature and ratio in the case of plasticized PVC, one of the most common material for infusion set tubing. Within the study, the drug concentration in diazepam solutions was studied after contact with PVC films containing different amounts of DEHP, DEHT, TOTM and DINCH® plasticizers. Moreover the partition coefficients between material and water were calculated. The drug sorption levels were equivalent for the different plasticizers and there was a plasticizer ratio for which the drug uptake was enhanced. As a consequence, the amount of sorbed drug might not be only linked to the amount of plasticizer in the film and to the solubility of the drug in the plasticizer alone: it must probably depend on specific interactions between plasticizer and PVC.

  8. Observation and Analysis of Resistive Instabilities in Negative Central Shear in DIII-D Discharges with L-Mode Edge

    SciTech Connect

    Jayakumar, R.J.; Austin, M.E.; Brennan, D.P.; Chu, M.S.; Luce, T.C.; Strait, E.J.; Turnbull, A.D.

    2002-07-01

    In DIII-D plasmas with L-mode edge and negative central shear (q{sub axis}-q{sub min} {approx}0.3 to 0.5), an interchange-like instability has been observed [1]. The instability and a subsequent tearing mode cause reduction of the core electron temperature and plasma rotation, and therefore the instability affects discharge evolution and the desired high performance is not achieved. Stability analyses indicate robust ideal stability, while the Resistive Interchange Mode criterion is marginal and the instability appears to be localized initially. Based on this, we believe that the mode is, most likely, a Resistive Interchange Mode. The amplitude of the instability is correlated with the location of the q{sub min} surface and inversely with the fast-ion pressure. There is indication that the interchange-like instability may be ''seeding'' the tearing mode that sometimes follows the interchange-like instability.

  9. The effects of control field detuning on the modulation instability in a three-level quantum well system

    SciTech Connect

    Borgohain, Nitu Konar, S.

    2016-06-07

    The paper presents a theoretical study of the modulation instability of a continuous or quasi-continuous optical probe in a three level quantum well system under electromagnetically induced transparency. The modulation instability is affected by the control field detuning, as well as even-order dispersion and by the strength of Kerr (third-order) and quintic (fifth-order) nonlinearities. The fourth-order dispersion reduces the bandwidth over which modulation instability occurs, whereas the quintic nonlinearity saturates the growth of the modulation instability. Detuning the control field from resonance can significantly reduce the growth of the modulation instability at both low and high power levels. At low powers, the system becomes stable against modulation instability for small detuning of the control field and at high powers modulation instability disappears for larger detuning.

  10. Motor Cortical Plasticity in Parkinson’s Disease

    PubMed Central

    Udupa, Kaviraja; Chen, Robert

    2013-01-01

    In Parkinson’s disease (PD), there are alterations of the basal ganglia (BG) thalamocortical networks, primarily due to degeneration of nigrostriatal dopaminergic neurons. These changes in subcortical networks lead to plastic changes in primary motor cortex (M1), which mediates cortical motor output and is a potential target for treatment of PD. Studies investigating the motor cortical plasticity using non-invasive transcranial magnetic stimulation (TMS) have found altered plasticity in PD, but there are inconsistencies among these studies. This is likely because plasticity depends on many factors such as the extent of dopaminergic loss and disease severity, response to dopaminergic replacement therapies, development of l-DOPA-induced dyskinesias (LID), the plasticity protocol used, medication, and stimulation status in patients treated with deep brain stimulation (DBS). The influences of LID and DBS on BG and M1 plasticity have been explored in animal models and in PD patients. In addition, many other factors such age, genetic factors (e.g., brain derived neurotropic factor and other neurotransmitters or receptors polymorphism), emotional state, time of the day, physical fitness have been documented to play role in the extent of plasticity induced by TMS in human studies. In this review, we summarize the studies that investigated M1 plasticity in PD and demonstrate how these afore-mentioned factors affect motor cortical plasticity in PD. We conclude that it is important to consider the clinical, demographic, and technical factors that influence various plasticity protocols while developing these protocols as diagnostic or prognostic tools in PD. We also discuss how the modulation of cortical excitability and the plasticity with these non-invasive brain stimulation techniques facilitate the understanding of the pathophysiology of PD and help design potential therapeutic possibilities in this disorder. PMID:24027555

  11. Recycling of plastic waste: Screening for brominated flame retardants (BFRs).

    PubMed

    Pivnenko, K; Granby, K; Eriksson, E; Astrup, T F

    2017-08-30

    Flame retardants are chemicals vital for reducing risks of fire and preventing human casualties and property losses. Due to the abundance, low cost and high performance of bromine, brominated flame retardants (BFRs) have had a significant share of the market for years. Physical stability on the other hand, has resulted in dispersion and accumulation of selected BFRs in the environment and receiving biota. A wide range of plastic products may contain BFRs. This affects the quality of waste plastics as secondary resource: material recycling may potentially reintroduce the BFRs into new plastic product cycles and lead to increased exposure levels, e.g. through use of plastic packaging materials. To provide quantitative and qualitative data on presence of BFRs in plastics, we analysed bromophenols (tetrabromobisphenol A (TBBPA), dibromophenols (2,4- and 2,6-DBP) and 2,4,6-tribromophenol (2,4,6-TBP)), hexabromocyclododecane stereoisomers (α-, β-, and γ-HBCD), as well as selected polybrominated diphenyl ethers (PBDEs) in samples of household waste plastics, virgin and recycled plastics. A considerable number of samples contained BFRs, with highest concentrations associated with acrylonitrile butadiene styrene (ABS, up to 26,000,000ngTBBPA/g) and polystyrene (PS, up to 330,000ng∑HBCD/g). Abundancy in low concentrations of some BFRs in plastic samples suggested either unintended addition in plastic products or degradation of higher molecular weight BFRs. The presence of currently restricted flame retardants (PBDEs and HBCD) identified in the plastic samples illustrates that circular material flows may be contaminated for extended periods. The screening clearly showed a need for improved documentation and monitoring of the presence of BFRs in plastic waste routed to recycling. Copyright © 2017. Published by Elsevier Ltd.

  12. Rigid plastic collars for marking geese

    USGS Publications Warehouse

    Ballou, R.M.; Martin, F.W.

    1964-01-01

    Rigid plastic collars of one to three colors proved useful for recognition of individual Canada geese (Branta canadensis). The collars did not seem to affect the behavior of the geese, and there was little mortality caused by their use. In good light, bright colors are visible through a 20-power spotting scope for more than 1 mile. Retention of collars was about 90 percent for 1 year and more than 80 percent for 2 years.

  13. Epigenetic Control of Phenotypic Plasticity in the Filamentous Fungus Neurospora crassa

    PubMed Central

    Kronholm, Ilkka; Johannesson, Hanna; Ketola, Tarmo

    2016-01-01

    Phenotypic plasticity is the ability of a genotype to produce different phenotypes under different environmental or developmental conditions. Phenotypic plasticity is a ubiquitous feature of living organisms, and is typically based on variable patterns of gene expression. However, the mechanisms by which gene expression is influenced and regulated during plastic responses are poorly understood in most organisms. While modifications to DNA and histone proteins have been implicated as likely candidates for generating and regulating phenotypic plasticity, specific details of each modification and its mode of operation have remained largely unknown. In this study, we investigated how epigenetic mechanisms affect phenotypic plasticity in the filamentous fungus Neurospora crassa. By measuring reaction norms of strains that are deficient in one of several key physiological processes, we show that epigenetic mechanisms play a role in homeostasis and phenotypic plasticity of the fungus across a range of controlled environments. In general, effects on plasticity are specific to an environment and mechanism, indicating that epigenetic regulation is context dependent and is not governed by general plasticity genes. Specifically, we found that, in Neurospora, histone methylation at H3K36 affected plastic response to high temperatures, H3K4 methylation affected plastic response to pH, but H3K27 methylation had no effect. Similarly, DNA methylation had only a small effect in response to sucrose. Histone deacetylation mainly decreased reaction norm elevation, as did genes involved in histone demethylation and acetylation. In contrast, the RNA interference pathway was involved in plastic responses to multiple environments. PMID:27694114

  14. Posterior instability caused by batter's shoulder.

    PubMed

    Kang, Richard W; Mahony, Gregory T; Harris, Thomas C; Dines, Joshua S

    2013-10-01

    In summary, batter’s shoulder is a rare and only recently recognized entity. This condition is posterior shoulder instability caused by a missed attempt at hitting a pitch, especially with an outside pitch. The lack of counterforce from hitting a ball produces increased forces imparted on the posterior capsulolabral complex of the lead shoulder during batting. If the player fails conservative management, she or he can undergo an arthroscopic posterior labral repair instead of debridement. After treatment, the player can expect to return to play after approximately 6 to 7 months. Initial results from a small, retrospective series demonstrate greater than 90% excellent results. These findings are similar to current literature for arthroscopic treatment of posterior instability, which reports success rates that range from 75% to 91%. Longer-term follow-up will be needed to determine the natural history and prognosis or batter’s shoulder. Based on initial results, the authors predict good to excellent results for most players with batter’s shoulder who undergo proper treatment. Additionally, with the exception of switch hitters, the nonthrowing arm is affected. This can also improve the athlete’s return to play. Copyright © 2013 Elsevier Inc. All rights reserved.

  15. Effects of incoming wind condition and wind turbine aerodynamics on the hub vortex instability

    NASA Astrophysics Data System (ADS)

    Ashton, R.; Viola, F.; Gallaire, F.; Iungo, G. V.

    2015-06-01

    Dynamics and instabilities occurring in the near-wake of wind turbines have a crucial role for the wake downstream evolution, and for the onset of far-wake instabilities. Furthermore, wake dynamics significantly affect the intra-wind farm wake flow, wake interactions and potential power losses. Therefore, the physical understanding and predictability of wind turbine wake instabilities become a nodal point for prediction of wind power harvesting and optimization of wind farm layout. This study is focused on the prediction of the hub vortex instability encountered within wind turbine wakes under different operational conditions of the wind turbine. Linear stability analysis of the wake flow is performed by means of a novel approach that enables to take effects of turbulence on wake instabilities into account. Stability analysis is performed by using as base flow the time-averaged wake velocity field at a specific downstream location. The latter is modeled through Carton-McWilliams velocity profiles by mimicking the presence of the hub vortex and helicoidal tip vortices, and matching the wind turbine thrust coefficient predicted through the actuator disc model. The results show that hub vortex instability is promoted by increasing the turbine thrust coefficient. Indeed, a larger aerodynamic load produces an enhanced wake velocity deficit and axial shear, which are considered the main sources for the wake instability. Nonetheless, wake swirl also promotes hub vortex instability, and it can also affect the azimuthal wavenumber of the most unstable mode.

  16. Lending sociodynamics and economic instability

    NASA Astrophysics Data System (ADS)

    Hawkins, Raymond J.

    2011-11-01

    We show how the dynamics of economic instability and financial crises articulated by Keynes in the General Theory and developed by Minsky as the Financial Instability Hypothesis can be formalized using Weidlich’s sociodynamics of opinion formation. The model addresses both the lending sentiment of a lender in isolation as well as the impact on that lending sentiment of the behavior of other lenders. The risk associated with lending is incorporated through a stochastic treatment of loan dynamics that treats prepayment and default as competing risks. With this model we are able to generate endogenously the rapid changes in lending opinion that attend slow changes in lending profitability and find these dynamics to be consistent with the rise and collapse of the non-Agency mortgage-backed securities market in 2007/2008. As the parameters of this model correspond to well-known phenomena in cognitive and social psychology, we can both explain why economic instability has proved robust to advances in risk measurement and suggest how policy for reducing economic instability might be formulated in an experimentally sound manner.

  17. Biomechanics of complex shoulder instability.

    PubMed

    Degen, Ryan M; Giles, Joshua W; Thompson, Stephen R; Litchfield, Robert B; Athwal, George S

    2013-10-01

    Identification and treatment of the osseous lesions associated with complex shoulder instability remains challenging. Further biomechanical testing is required to delineate critical defect values and determine which treatments provide improved glenohumeral joint stability for the various defect sizes, while minimizing the associated complications.

  18. The Chemistry of Beer Instability

    ERIC Educational Resources Information Center

    Stewart, Graham G.

    2004-01-01

    Brewing of beer, one of the oldest biotechnology industries was one of the earliest processes to be undertaken on commercial basis. Biological instability involves contamination of bacteria, yeast, or mycelia fungi and there is always a risk in brewing that beer can become contaminated by micro-organisms.

  19. Finite element shell instability analysis

    NASA Technical Reports Server (NTRS)

    1975-01-01

    Formulation procedures and the associated computer program for finite element thin shell instability analysis are discussed. Data cover: (1) formulation of basic element relationships, (2) construction of solution algorithms on both the conceptual and algorithmic levels, and (3) conduction of numerical analyses to verify the accuracy and efficiency of the theory and related programs therein are described.

  20. Edge instabilities of topological superconductors

    NASA Astrophysics Data System (ADS)

    Hofmann, Johannes S.; Assaad, Fakher F.; Schnyder, Andreas P.

    2016-05-01

    Nodal topological superconductors display zero-energy Majorana flat bands at generic edges. The flatness of these edge bands, which is protected by time-reversal and translation symmetry, gives rise to an extensive ground-state degeneracy. Therefore, even arbitrarily weak interactions lead to an instability of the flat-band edge states towards time-reversal and translation-symmetry-broken phases, which lift the ground-state degeneracy. We examine the instabilities of the flat-band edge states of dx y-wave superconductors by performing a mean-field analysis in the Majorana basis of the edge states. The leading instabilities are Majorana mass terms, which correspond to coherent superpositions of particle-particle and particle-hole channels in the fermionic language. We find that attractive interactions induce three different mass terms. One is a coherent superposition of imaginary s -wave pairing and current order, and another combines a charge-density-wave and finite-momentum singlet pairing. Repulsive interactions, on the other hand, lead to ferromagnetism together with spin-triplet pairing at the edge. Our quantum Monte Carlo simulations confirm these findings and demonstrate that these instabilities occur even in the presence of strong quantum fluctuations. We discuss the implications of our results for experiments on cuprate high-temperature superconductors.